Vagal sensory neurons mediate the Bezold-Jarisch reflex and induce syncope

Visceral sensory pathways mediate homeostatic reflexes, the dysfunction of which leads to many neurological disorders1. The Bezold-Jarisch reflex (BJR), first described2,3 in 1867, is a cardioinhibitory reflex that is speculated to be mediated by vagal sensory neurons (VSNs) that also triggers syncope. However, the molecular identity, anatomical organization, physiological characteristics and behavioural influence of cardiac VSNs remain mostly unknown. Here we leveraged single-cell RNA-sequencing data and HYBRiD tissue clearing4 to show that VSNs that express neuropeptide Y receptor Y2 (NPY2R) predominately connect the heart ventricular wall to the area postrema. Optogenetic activation of NPY2R VSNs elicits the classic triad of BJR responses-hypotension, bradycardia and suppressed respiration-and causes an animal to faint. Photostimulation during high-resolution echocardiography and laser Doppler flowmetry with behavioural observation revealed a range of phenotypes reflected in clinical syncope, including reduced cardiac output, cerebral hypoperfusion, pupil dilation and eye-roll. Large-scale Neuropixels brain recordings and machine-learning-based modelling showed that this manipulation causes the suppression of activity across a large distributed neuronal population that is not explained by changes in spontaneous behavioural movements. Additionally, bidirectional manipulation of the periventricular zone had a push-pull effect, with inhibition leading to longer syncope periods and activation inducing arousal. Finally, ablating NPY2R VSNs specifically abolished the BJR. Combined, these results demonstrate a genetically defined cardiac reflex that recapitulates characteristics of human syncope at physiological, behavioural and neural network levels.

Characteristics of Heart Failure Patients With or Without Hypotension When Transitioning From Nitroprusside to Sacubitril-Valsartan

BACKGROUND

Sacubitril-valsartan is an angiotensin receptor-neprilysin inhibitor indicated for the treatment of patients with symptomatic heart failure with reduced ejection fraction (HFrEF). Little is known about outcomes of HFrEF patients transitioned from sodium nitroprusside (SNP) to sacubitril-valsartan during an admission for acute decompensated heart failure. We sought to describe characteristics of patients initiated on sacubitril-valsartan while receiving SNP and, in particular, those patients who did and did not experience hypotension requiring interruption or discontinuation of sacubitril-valsartan.

METHODS

We performed a retrospective case series of adult patients (>18 years) with HFrEF (left ventricular ejection fraction ≤40%) admitted to the University of Michigan cardiac intensive care unit between July 2018 to September 2020 who received sacubitril-valsartan while on SNP.

RESULTS

A total of 15 patients with acute decompensated heart failure were initiated on sacubitril-valsartan while on SNP. The mean age was 57 ± 15.9 years. Seven (46.7%) patients experienced hypotension. The patients in the cohort who experienced hypotension were numerically older (60 ± 17 vs. 55 ± 15.5), and the majority were white (86%). Patients with hypotension had a numerically lower left ventricular ejection fraction (13 ± 4.2 vs. 18 ± 8.2) and higher serum creatinine (1.4 ± 0.54 vs. 0.88 ± 0.25). Seven (100%) patients received a diuretic on the day of sacubitril-valsartan initiation in those who experienced hypotension compared with 2 (25%) in those who did not experience hypotension.

CONCLUSIONS

In almost half of patients admitted to the cardiac intensive care unit with acutely decompensated HFrEF, significant hypotension was seen when initiating sacubitril-valsartan while on SNP. Future studies should evaluate appropriate patients for this transition and delineate appropriate titration parameters.

Potential for Gut Peptide-Based Therapy in Postprandial Hypotension

Postprandial hypotension (PPH) is an important and under-recognised disorder resulting from inadequate compensatory cardiovascular responses to meal-induced splanchnic blood pooling. Current approaches to management are suboptimal. Recent studies have established that the cardiovascular response to a meal is modulated profoundly by gastrointestinal factors, including the type and caloric content of ingested meals, rate of gastric emptying, and small intestinal transit and absorption of nutrients. The small intestine represents the major site of nutrient-gut interactions and associated neurohormonal responses, including secretion of glucagon-like peptide-1, glucose-dependent insulinotropic peptide and somatostatin, which exert pleotropic actions relevant to the postprandial haemodynamic profile. This review summarises knowledge relating to the role of these gut peptides in the cardiovascular response to a meal and their potential application to the management of PPH.

Hypotension during endovascular treatment under general anesthesia for acute ischemic stroke

Objective

The effect of anesthetic management (general anesthesia [GA], conscious sedation, or local anesthesia) on functional outcome and the role of blood pressure management during endovascular treatment (EVT) for acute ischemic stroke is under debate. We aimed to determine whether hypotension during EVT under GA is associated with functional outcome at 90 days.

Methods

We retrospectively collected data from patients with a proximal intracranial occlusion of the anterior circulation treated with EVT under GA. The primary outcome was the distribution on the modified Rankin Scale at 90 days. Hypotension was defined using two thresholds: a mean arterial pressure (MAP) of 70 mm Hg and a MAP 30% below baseline MAP. To quantify the extent and duration of hypotension, the area under the threshold (AUT) was calculated using both thresholds.

Results

Of the 366 patients included, procedural hypotension was observed in approximately half of them. The occurrence of hypotension was associated with poor functional outcome (MAP <70 mm Hg: adjusted common odds ratio [acOR], 0.57; 95% confidence interval [CI], 0.35–0.94; MAP decrease ≥30%: acOR, 0.76; 95% CI, 0.48–1.21). In addition, an association was found between the number of hypotensive periods and poor functional outcome (MAP <70 mm Hg: acOR, 0.85 per period increase; 95% CI, 0.73–0.99; MAP decrease ≥30%: acOR, 0.90 per period; 95% CI, 0.78–1.04). No association existed between AUT and functional outcome (MAP <70 mm Hg: acOR, 1.000 per 10 mm Hg*min increase; 95% CI, 0.998–1.001; MAP decrease ≥30%: acOR, 1.000 per 10 mm Hg*min; 95% CI, 0.999–1.000).

Conclusions

Occurrence of procedural hypotension and an increase in number of procedural hypotensive periods were associated with poor functional outcome, whereas the extent and duration of hypotension were not. Randomized clinical trials are needed to confirm our hypothesis that hypotension during EVT under GA has detrimental effects.

Establishment and validation of a predictive model for mortality within 30 days in patients with sepsis-induced blood pressure drop: A retrospective analysis

OBJECTIVES

To establish and validate an individualized nomogram to predict the probability of death within 30 days in patients with sepsis-induced blood pressure drop would help clinical physicians to pay attention to those with higher risk of death after admission to wards.

METHODS

A total of 1023 patients who were admitted to the Dongyang People's Hospital, China, enrolled in this study. They were divided into model group (717 patients) and validation group (306 patients). The study included 13 variables. The independent risk factors leading to death within 30 days were screened by univariate analyses and multivariate logistic regression analyses and used for Nomogram. The discrimination and correction of the prediction model were assessed by the area under the Receiver Operating Characteristic (ROC) curve and the calibration chart. The clinical effectiveness of the prediction model was assessed by the Decision Curve Analysis (DCA).

RESULTS

Seven variables were independent risk factors, included peritonitis, respiratory failure, cardiac insufficiency, consciousness disturbance, tumor history, albumin level, and creatinine level at the time of admission. The area under the ROC curve of the model group and validation group was 0.834 and 0.836. The P value of the two sets of calibration charts was 0.702 and 0.866. The DCA curves of the model group and validation group were above the two extreme (insignificant) curves.

CONCLUSIONS

The model described in this study could effectively predict the death of patients with sepsis-induced blood pressure drop.

Severe traumatic brain injury and hypotension is a frequent and lethal combination in multiple trauma patients in mountain areas - an analysis of the prospective international Alpine Trauma Registry

BACKGROUND

Hypotension is associated with worse outcome in patients with traumatic brain injury (TBI) and maintaining a systolic blood pressure (SBP) ≥110 mmHg is recommended. The aim of this study was to assess the incidence of TBI in patients suffering multiple trauma in mountain areas; to describe associated factors, treatment and outcome compared to non-hypotensive patients with TBI and patients without TBI; and to evaluate pre-hospital variables to predict admission hypotension.

METHODS

Data from the prospective International Alpine Trauma Registry including mountain multiple trauma patients (ISS ≥ 16) collected between 2010 and 2019 were analysed. Patients were divided into three groups: 1) TBI with hypotension, 2) TBI without hypotension and 3) no TBI. TBI was defined as Abbreviated Injury Scale (AIS) of the head/neck ≥3 and hypotension as SBP < 110 mmHg on hospital arrival.

RESULTS

A total of 287 patients were included. Fifty (17%) had TBI and hypotension, 92 (32%) suffered TBI without hypotension and 145 (51%) patients did not have TBI. Patients in group 1 were more severely injured (mean ISS 43.1 ± 17.4 vs 33.3 ± 15.3 vs 26.2 ± 18.1 for group 1 vs 2 vs 3, respectively, p < 0.001). Mean SBP on hospital arrival was 83.1 ± 12.9 vs 132.5 ± 19.4 vs 119.4 ± 25.8 mmHg (p < 0.001) despite patients in group 1 received more fluids. Patients in group 1 had higher INR, lower haemoglobin and lower base excess (p < 0.001). More than one third of patients in group 1 and 2 were hypothermic (body temperature < 35 °C) on hospital arrival while the rate of admission hypothermia was low in patients without TBI (41% vs 35% vs 21%, for group 1 vs 2 vs 3, p = 0.029). The rate of hypothermia on hospital arrival was different between the groups (p = 0.029). Patients in group 1 had the highest mortality (24% vs 10% vs 1%, p < 0.001).

CONCLUSION

Multiple trauma in the mountains goes along with severe TBI in almost 50%. One third of patients with TBI is hypotensive on hospital arrival and this is associated with a worse outcome. No single variable or set of variables easily obtainable at scene was able to predict admission hypotension in TBI patients.

Angiotensin II receptor type 1 blockade improves hyporesponsiveness to vasopressors in septic shock

Sepsis activates the renin-angiotensin system and the production of angiotensin II, which has a key role in the regulation of blood pressure through AT1 receptors. However, excessive activation of AT1 receptor is associated with deleterious effects. We investigated the consequences of a differential blockade of AT1 receptor caused by two doses of losartan (0.25 mg/kg or 15 mg/kg, s.c), a selective AT1 receptor antagonist on sepsis outcome. These doses reduced the effect of angiotensin II in normal rats by 30% and >90% 8 h after administration, respectively, but only the higher dose maintained its inhibitory effect (~70%) 24 h after injection. Sepsis was induced by cecal ligation and puncture (CLP). Losartan was injected 2 h after CLP and parameters were evaluated 6 and 24 h after CLP. Septic rats developed hypotension and hyporesponsiveness to vasoconstrictors, an intense inflammatory process and increase in plasma markers of organ dysfunction. The lower dose of losartan improved the vasoconstrictive response to phenylephrine and angiotensin II, reduced lung myeloperoxidase and prevented leukopenia 24 h after CLP, but it did not reduce NOS-2 expression, plasma IL-6 levels or organ injury parameters of septic rats. On the other hand, the higher dose of losartan worsened the response to vasoconstrictors, potentiated the hypotension and increased further levels of creatine, urea and lactate in septic rats. Therefore, an early and partial blockade of AT1 receptor with a low dose of losartan may counteract sepsis-induced refractoriness to vasoconstrictors thus providing an opportunity to improve the outcome of this condition.

Omecamtiv mecarbil evokes diastolic dysfunction and leads to periodic electromechanical alternans

Omecamtiv mecarbil (OM) is a promising novel drug for improving cardiac contractility. We tested the therapeutic range of OM and identified previously unrecognized side effects. The Ca2+ sensitivity of isometric force production (pCa50) and force at low Ca2+ levels increased with OM concentration in human permeabilized cardiomyocytes. OM (1 µM) slowed the kinetics of contractions and relaxations and evoked an oscillation between normal and reduced intracellular Ca2+ transients, action potential lengths and contractions in isolated canine cardiomyocytes. Echocardiographic studies and left ventricular pressure-volume analyses demonstrated concentration-dependent improvements in cardiac systolic function at OM concentrations of 600-1200 µg/kg in rats. Administration of OM at a concentration of 1200 µg/kg was associated with hypotension, while doses of 600-1200 µg/kg were associated with the following aspects of diastolic dysfunction: decreases in E/A ratio and the maximal rate of diastolic pressure decrement (dP/dtmin) and increases in isovolumic relaxation time, left atrial diameter, the isovolumic relaxation constant Tau, left ventricular end-diastolic pressure and the slope of the end-diastolic pressure-volume relationship. Moreover, OM 1200 µg/kg frequently evoked transient electromechanical alternans in the rat in vivo in which normal systoles were followed by smaller contractions (and T-wave amplitudes) without major differences on the QRS complexes. Besides improving systolic function, OM evoked diastolic dysfunction and pulsus alternans. The narrow therapeutic window for OM may necessitate the monitoring of additional clinical safety parameters in clinical application.

Low central blood pressure and sympathetic activity predispose for the development of intradialytic hypotension

Intradialytic hypotension (IDH) may lead to a poor life quality and was associated with cardiovascular mortality in patients under hemodialysis. This study investigated the autonomic nerve and cardiovascular function in the IDH episodes.In this case-control study, 70 end stage renal disease patients (198 visits) were recruited. Pulse wave analysis and heart rate variability were evaluated before hemodialysis. Two definitions of IDH were confirmed by medical records. IDH-f indicated a drop of systolic blood pressure or mean arterial pressure, accompanied with symptoms; IDH-n indicated a low nadir systolic pressure during the hemodialysis. All parameters were evaluated for the possible predisposing factors under each definition.A total of 24 IDH-f and 37 IDH-n were noted in 177 visits. For both definitions, central pulse pressure seemed to be a consistent predisposing factor. Furthermore, lower sympathetic activity (odds ratio [OR] 0.55; 95% confidence interval [CI] 0.35-0.87), lower pulse pressure (OR 0.95; 95% CI 0.92-0.98), and higher augmentation index (OR 17.36; 95% CI 1.48-204.10) were the possible predisposing factors for IDH-f. On the contrary, lower mean arterial pressure (OR 0.87; 95% CI 0.78-0.98) was identified as the possible factor for IDH-n.It was suggested that the lower central pulse pressure and sympathetic activity might be involved in the development of IDH.

Recipient pre-existing chronic hypotension is associated with delayed graft function and inferior graft survival in kidney transplantation from elderly donors

Background

Pre-existing chronic hypotension affects a percentage of kidney transplanted patients (KTs). Although a relationship with delayed graft function (DGF) has been hypothesized, available data are still scarce and inconclusive.

Methods

A monocentric retrospective observational study was performed on 1127 consecutive KTs from brain death donors over 11 years (2003–2013), classified according to their pre-transplant Mean Blood Pressure (MBP) as hypotensive (MBP < 80 mmHg) or normal-hypertensive (MBP ≥ 80 mmHg, with or without effective antihypertensive therapy).

Results

Univariate analysis showed that a pre-existing hypotension is associated to DGF occurrence (p<0.01; OR for KTs with MBP < 80 mmHg, 4.5; 95% confidence interval [CI], 2.7 to 7.5). Chronic hypotension remained a major predictive factor for DGF development in the logistic regression model adjusted for all DGF determinants. Adjunctive evaluations on paired grafts performed in two different recipients (one hypotensive and the other one normal-hypertensive) confirmed this assumption. Although graft survival was only associated with DGF but not with chronic hypotension in the overall population, stratification according to donor age revealed that death-censored graft survival was significantly lower in hypotensive patients who received a KT from >50 years old donor.

Conclusions

Our findings suggest that pre-existing recipient hypotension, and the subsequent hypotension-related DGF, could be considered a significant detrimental factor, especially when elderly donors are involved in the transplant procedure.

Defining Kawasaki disease and pediatric inflammatory multisystem syndrome-temporally associated to SARS-CoV-2 infection during SARS-CoV-2 epidemic in Italy: results from a national, multicenter survey

BACKGROUND

There is mounting evidence on the existence of a Pediatric Inflammatory Multisystem Syndrome-temporally associated to SARS-CoV-2 infection (PIMS-TS), sharing similarities with Kawasaki Disease (KD). The main outcome of the study were to better characterize the clinical features and the treatment response of PIMS-TS and to explore its relationship with KD determining whether KD and PIMS are two distinct entities.

METHODS

The Rheumatology Study Group of the Italian Pediatric Society launched a survey to enroll patients diagnosed with KD (Kawasaki Disease Group - KDG) or KD-like (Kawacovid Group - KCG) disease between February 1st 2020, and May 31st 2020. Demographic, clinical, laboratory data, treatment information, and patients' outcome were collected in an online anonymized database (RedCAP®). Relationship between clinical presentation and SARS-CoV-2 infection was also taken into account. Moreover, clinical characteristics of KDG during SARS-CoV-2 epidemic (KDG-CoV2) were compared to Kawasaki Disease patients (KDG-Historical) seen in three different Italian tertiary pediatric hospitals (Institute for Maternal and Child Health, IRCCS "Burlo Garofolo", Trieste; AOU Meyer, Florence; IRCCS Istituto Giannina Gaslini, Genoa) from January 1st 2000 to December 31st 2019. Chi square test or exact Fisher test and non-parametric Wilcoxon Mann-Whitney test were used to study differences between two groups.

RESULTS

One-hundred-forty-nine cases were enrolled, (96 KDG and 53 KCG). KCG children were significantly older and presented more frequently from gastrointestinal and respiratory involvement. Cardiac involvement was more common in KCG, with 60,4% of patients with myocarditis. 37,8% of patients among KCG presented hypotension/non-cardiogenic shock. Coronary artery abnormalities (CAA) were more common in the KDG. The risk of ICU admission were higher in KCG. Lymphopenia, higher CRP levels, elevated ferritin and troponin-T characterized KCG. KDG received more frequently immunoglobulins (IVIG) and acetylsalicylic acid (ASA) (81,3% vs 66%; p = 0.04 and 71,9% vs 43,4%; p = 0.001 respectively) as KCG more often received glucocorticoids (56,6% vs 14,6%; p < 0.0001). SARS-CoV-2 assay more often resulted positive in KCG than in KDG (75,5% vs 20%; p < 0.0001). Short-term follow data showed minor complications. Comparing KDG with a KD-Historical Italian cohort (598 patients), no statistical difference was found in terms of clinical manifestations and laboratory data.

CONCLUSION

Our study suggests that SARS-CoV-2 infection might determine two distinct inflammatory diseases in children: KD and PIMS-TS. Older age at onset and clinical peculiarities like the occurrence of myocarditis characterize this multi-inflammatory syndrome. Our patients had an optimal response to treatments and a good outcome, with few complications and no deaths.

Defining Kawasaki disease and pediatric inflammatory multisystem syndrome-temporally associated to SARS-CoV-2 infection during SARS-CoV-2 epidemic in Italy: results from a national, multicenter survey

BACKGROUND

There is mounting evidence on the existence of a Pediatric Inflammatory Multisystem Syndrome-temporally associated to SARS-CoV-2 infection (PIMS-TS), sharing similarities with Kawasaki Disease (KD). The main outcome of the study were to better characterize the clinical features and the treatment response of PIMS-TS and to explore its relationship with KD determining whether KD and PIMS are two distinct entities.

METHODS

The Rheumatology Study Group of the Italian Pediatric Society launched a survey to enroll patients diagnosed with KD (Kawasaki Disease Group - KDG) or KD-like (Kawacovid Group - KCG) disease between February 1st 2020, and May 31st 2020. Demographic, clinical, laboratory data, treatment information, and patients' outcome were collected in an online anonymized database (RedCAP®). Relationship between clinical presentation and SARS-CoV-2 infection was also taken into account. Moreover, clinical characteristics of KDG during SARS-CoV-2 epidemic (KDG-CoV2) were compared to Kawasaki Disease patients (KDG-Historical) seen in three different Italian tertiary pediatric hospitals (Institute for Maternal and Child Health, IRCCS "Burlo Garofolo", Trieste; AOU Meyer, Florence; IRCCS Istituto Giannina Gaslini, Genoa) from January 1st 2000 to December 31st 2019. Chi square test or exact Fisher test and non-parametric Wilcoxon Mann-Whitney test were used to study differences between two groups.

RESULTS

One-hundred-forty-nine cases were enrolled, (96 KDG and 53 KCG). KCG children were significantly older and presented more frequently from gastrointestinal and respiratory involvement. Cardiac involvement was more common in KCG, with 60,4% of patients with myocarditis. 37,8% of patients among KCG presented hypotension/non-cardiogenic shock. Coronary artery abnormalities (CAA) were more common in the KDG. The risk of ICU admission were higher in KCG. Lymphopenia, higher CRP levels, elevated ferritin and troponin-T characterized KCG. KDG received more frequently immunoglobulins (IVIG) and acetylsalicylic acid (ASA) (81,3% vs 66%; p = 0.04 and 71,9% vs 43,4%; p = 0.001 respectively) as KCG more often received glucocorticoids (56,6% vs 14,6%; p < 0.0001). SARS-CoV-2 assay more often resulted positive in KCG than in KDG (75,5% vs 20%; p < 0.0001). Short-term follow data showed minor complications. Comparing KDG with a KD-Historical Italian cohort (598 patients), no statistical difference was found in terms of clinical manifestations and laboratory data.

CONCLUSION

Our study suggests that SARS-CoV-2 infection might determine two distinct inflammatory diseases in children: KD and PIMS-TS. Older age at onset and clinical peculiarities like the occurrence of myocarditis characterize this multi-inflammatory syndrome. Our patients had an optimal response to treatments and a good outcome, with few complications and no deaths.

Pannexin 1 channels control the hemodynamic response to hypoxia by regulating O2-sensitive extracellular ATP in blood

Pannexin 1 (Panx1) channels export ATP and may contribute to increased concentration of the vasodilator ATP in plasma during hypoxia in vivo. We hypothesized that Panx1 channels and associated ATP export contribute to hypoxic vasodilation, a mechanism that facilitates the matching of oxygen delivery to metabolic demand of tissue. Male and female mice devoid of Panx1 (Panx1-/-) and wild-type controls (WT) were anesthetized, mechanically ventilated, and instrumented with a carotid artery catheter or femoral artery flow transducer for hemodynamic and plasma ATP monitoring during inhalation of 21% (normoxia) or 10% oxygen (hypoxia). ATP export from WT vs. Panx1-/-erythrocytes (RBC) was determined ex vivo via tonometer experimentation across progressive deoxygenation. Mean arterial pressure (MAP) was similar in Panx1-/- (n = 6) and WT (n = 6) mice in normoxia, but the decrease in MAP in hypoxia seen in WT was attenuated in Panx1-/- mice (-16 ± 9% vs. -2 ± 8%; P < 0.05). Hindlimb blood flow (HBF) was significantly lower in Panx1-/- (n = 6) vs. WT (n = 6) basally, and increased in WT but not Panx1-/- mice during hypoxia (8 ± 6% vs. -10 ± 13%; P < 0.05). Estimation of hindlimb vascular conductance using data from the MAP and HBF experiments showed an average response of 28% for WT vs. -9% for Panx1-/- mice. Mean venous plasma ATP during hypoxia was 57% lower in Panx1-/- (n = 6) vs. WT mice (n = 6; P < 0.05). Mean hypoxia-induced ATP export from RBCs from Panx1-/- mice (n = 8) was 82% lower than that from WT (n = 8; P < 0.05). Panx1 channels participate in hemodynamic responses consistent with hypoxic vasodilation by regulating hypoxia-sensitive extracellular ATP levels in blood.NEW & NOTEWORTHY Export of vasodilator ATP from red blood cells requires pannexin 1. Blood plasma ATP elevations in response to hypoxia in mice require pannexin 1. Hemodynamic responses to hypoxia are accompanied by increased plasma ATP in mice in vivo and require pannexin 1.

Complete recovery from COVID-19 of a kidney-pancreas transplant recipient: potential benefit from everolimus?

We present a kidney-pancreas transplant recipient who achieved complete recovery from COVID-19. A 45-year-old patient with T3 paraplegia underwent kidney-pancreas transplantation 18 years ago, followed by a subsequent kidney transplant 9 years ago, and presented with fever, hypoxia and hypotension after exposure to two confirmed cases of COVID-19. History of solid organ transplant, pre-existing renal impairment, asthma and an elevated D-dimer were identified as established risk factors for severe COVID-19. Supportive management was provided, baseline immunosuppression with everolimus was continued, and oral prednisolone was increased. A complete recovery was observed. Given the favourable outcome despite risk factors for severe COVID-19, we identify and review the potential mitigating roles of immunosuppression and mammalian target of rapamycin (mTOR) inhibitors in this disease. Further investigation is required to establish whether mTOR inhibitors could be used as therapeutic agents to treat COVID-19, or as alternative immunosuppression implemented early in the COVID-19 disease course.

Combined head and abdominal blunt trauma in the hemodynamically unstable patient: What takes priority?

BACKGROUND

The management of hypotensive patients with severe combined head and abdominal trauma is challenging, regarding the need, timing, and sequence of craniotomy or laparotomy. The purpose of the present study was to determine whether rare situations requiring craniotomy prior to laparotomy can be identified on admission with simple clinical parameters. We hypothesized that hypotension is rarely associated with the need of a combined procedure, especially in patients with mildly depressed consciousness.

METHODS

National Trauma Data Bank study, including adult blunt trauma patients with combined severe head (Abbreviated Injury Scale score, ≥ 3) and abdominal injury (Abbreviated Injury Scale score, ≥ 3). Data collection included demographic and clinical characteristics, laparotomy, and craniotomy within 24 hours of admission, types of intracranial pathologies, survival, and hospital stay. Multivariate regression analysis was used to determine factors predictive for the need of both operative procedures.

RESULTS

Of 25,585 patients with severe combined head and abdominal trauma, 8,744 (34.2%) needed only laparotomy, 534 (2.1%) only craniotomy, and 394 (1.5%) required both procedures within 24 hours of admission. In the subgroup of 4,667 hypotensive patients, 2,421 (51.9%) underwent only laparotomy, 54 (1.2%) only craniotomy, and 79 (1.7%) both procedures within 24 hours of admission. Only 5 (0.7%) of 711 hypotensive patients with Glasgow Coma Scale (GCS) score above 8 who required a laparotomy also needed a craniotomy. Among clinical parameters available on patient's arrival, GCS score of 7 to 8 was independently associated with the highest need for craniotomy in hypotensive patients requiring laparotomy (odds ratio, 7.94; p = 0.004).

CONCLUSION

The need for craniotomy in patients with severe combined head and abdominal injury requiring exploratory laparotomy is very low. In hypotensive patients requiring laparotomy, GCS score of 7 to 8 was an independent predictor of the need for craniotomy. In hemodynamically unstable patients with a GCS score greater than 8, it may be safer to proceed with a laparotomy first and address the head with a computed tomography scan at a later stage.

LEVEL OF EVIDENCE

Therapeutic, Level IV.

Association of dipping status of blood pressure, visual field defects, and retinal nerve fiber layer thickness in patients with normotensive glaucoma

The aim of this study was to evaluate the association between dipping status of blood pressure (BP), visual field defects (VFDs), and retinal nerve fiber layer (RNFL) thickness in patients with normotensive glaucoma (NTG). Our University echocardiography, electrocardiogram, 24-hour BP monitor and glaucoma database were reviewed from 2016 to 2018 to identify patients with NTG and hypertension (HTN). These NTG patients were followed for a mean 26.4 ± 13.6 months and were divided into 2 groups according to the absence or presence of VFDs. Among the 110 patients with NTG, 55 (50%) patients had VFDs. There were no differences of baseline characteristics between 2 groups. In univariate analysis, extreme dipper status at night in the 24-hour BP monitoring, HTN, age, diabetes mellitus, and hyperlipidemia were significantly associated with VFDs. In multivariate analysis, extreme dipper status at night in the 24-hour BP monitoring (odds ratio [OR] 4.094; P = .045) and HTN (OR 2.368; P = .048) were independent risk factors for VFDs at 2-year follow-up. Moreover, the RNFL thickness was thinner in NTG patients with VFDs (P < .001). VFDs group had more increased fluctuation of systolic and diastolic BP in 24-hour BP monitoring and that the extreme dipper status at night in the 24-hour BP monitoring and HTN itself were also associated with higher incidence of VFDs and thinning changes of the RNFL in patients with NTG, suggesting that more intensive medical therapy with close clinical follow-up will be required for these patients.

Prediction of hypotension events with physiologic vital sign signatures in the intensive care unit

BACKGROUND

Even brief hypotension is associated with increased morbidity and mortality. We developed a machine learning model to predict the initial hypotension event among intensive care unit (ICU) patients and designed an alert system for bedside implementation.

MATERIALS AND METHODS

From the Medical Information Mart for Intensive Care III (MIMIC-3) dataset, minute-by-minute vital signs were extracted. A hypotension event was defined as at least five measurements within a 10-min period of systolic blood pressure ≤ 90 mmHg and mean arterial pressure ≤ 60 mmHg. Using time series data from 30-min overlapping time windows, a random forest (RF) classifier was used to predict risk of hypotension every minute. Chronologically, the first half of extracted data was used to train the model, and the second half was used to validate the trained model. The model's performance was measured with area under the receiver operating characteristic curve (AUROC) and area under the precision recall curve (AUPRC). Hypotension alerts were generated using risk score time series, a stacked RF model. A lockout time were applied for real-life implementation.

RESULTS

We identified 1307 subjects (1580 ICU stays) as the hypotension group and 1619 subjects (2279 ICU stays) as the non-hypotension group. The RF model showed AUROC of 0.93 and 0.88 at 15 and 60 min, respectively, before hypotension, and AUPRC of 0.77 at 60 min before. Risk score trajectories revealed 80% and > 60% of hypotension predicted at 15 and 60 min before the hypotension, respectively. The stacked model with 15-min lockout produced on average 0.79 alerts/subject/hour (sensitivity 92.4%).

CONCLUSION

Clinically significant hypotension events in the ICU can be predicted at least 1 h before the initial hypotension episode. With a highly sensitive and reliable practical alert system, a vast majority of future hypotension could be captured, suggesting potential real-life utility.

Rapid declines in systolic blood pressure are associated with an increase in pulse transit time

BACKGROUND

The correlation between pulse transit time and blood pressure has been proposed as a route to measure continuous non-invasive blood pressure. We investigated whether pulse transit time trends could model blood pressure trends during episodes of rapid declines in blood pressure.

METHODS

From the Medical Information Mart for Intensive Care waveform database we identified substantial blood pressure reductions. Pulse transit time was calculated from the R-peak of the electrocardiogram to the peak of the arterial pulse waveform. The time-series were processed with a moving average filter before comparison. Averaged, continuous heart rate was also analysed as a control. The intra-individual association between variables was assessed per subject using linear regression.

RESULTS

In the 511 patients included we found a median correlation coefficient between blood pressure and pulse transit time of -0.93 (IQR -0.98 to -0.76) with regression slopes of -1.23 mmHg/ms (IQR -1.73 to -0.81). The median correlation coefficient between blood pressure and heart rate was 0.46 (IQR -0.16 to 0.83). In supplementary analysis, results did not differ substantially when widening inclusion criteria, but the results were not always consistent within subjects across episodes of hypotension.

CONCLUSIONS

In a large cohort of critically ill patients experiencing episodes of rapid declines in systolic blood pressure, there was a moderate-strong intra-individual correlation between averaged systolic blood pressure and averaged pulse transit time. Our findings encourage further investigation into using the pulse transit time for non-invasive real-time detection of hypotension.

Noninvasive continuous monitoring versus intermittent oscillometric measurements for the detection of hypotension during digestive endoscopy

BACKGROUND

Hemodynamic monitoring during digestive endoscopy is usually minimal and involves intermittent brachial pressure measurements. New continuous noninvasive devices to acquire instantaneous arterial blood pressure may be more sensitive to detect procedural hypotension.

PURPOSE

To compare the ability of noninvasive continuous monitoring with that of intermittent oscillometric measurements to detect hypotension during digestive endoscopy.

METHODS

In this observational prospective study, patients scheduled for gastrointestinal endoscopy and colonoscopy under sedation were monitored using intermittent pressure measurements and a noninvasive continuous technique (ClearSight™, Edwards). Stroke volume was estimated from the arterial pressure waveform. Mean arterial pressure and stroke volume values were recorded at T1 (prior to anesthetic induction), T2 (after anesthetic induction), T3 (gastric insufflation), T4 (end of gastroscopy), T5 (colonic insufflation). Hypotension was defined as mean arterial pressure < 65 mmHg.

RESULTS

Twenty patients (53±17 years) were included. Six patients (30%) had a hypotension detected using intermittent pressure measurements versus twelve patients (60%) using noninvasive continuous monitoring (p = 0.06). Mean arterial pressure decreased during the procedure with respect to T1 (p < 0.05), but the continuous method provided an earlier warning than the intermittent method (T3 vs T4). Nine patients (45%) had at least a 25% reduction in stroke volume, with respect to baseline.

CONCLUSION

Noninvasive continuous monitoring was more sensitive than intermittent measurements to detect hypotension. Estimation of stroke volume revealed profound reductions in systemic flow. Noninvasive continuous monitoring in high-risk patients undergoing digestive endoscopy under sedation could help in detecting hypoperfusion earlier than the usual intermittent blood pressure measurements.

Identifying cardiogenic shock in the emergency department

INTRODUCTION

Cardiogenic shock is difficult to diagnose due to diverse presentations, overlap with other shock states (i.e. sepsis), poorly understood pathophysiology, complex and multifactorial causes, and varied hemodynamic parameters. Despite advances in interventions, mortality in patients with cardiogenic shock remains high. Emergency clinicians must be ready to recognize and start appropriate therapy for cardiogenic shock early.

OBJECTIVE

This review will discuss the clinical evaluation and diagnosis of cardiogenic shock in the emergency department with a focus on the emergency clinician.

DISCUSSION

The most common cause of cardiogenic shock is a myocardial infarction, though many causes exist. It is classically diagnosed by invasive hemodynamic measures, but the diagnosis can be made in the emergency department by clinical evaluation, diagnostic studies, and ultrasound. Early recognition and stabilization improve morbidity and mortality. This review will focus on identification of cardiogenic shock through clinical examination, laboratory studies, and point-of-care ultrasound.

CONCLUSIONS

The emergency clinician should use the clinical examination, laboratory studies, electrocardiogram, and point-of-care ultrasound to aid in the identification of cardiogenic shock. Cardiogenic shock has the potential for significant morbidity and mortality if not recognized early.

What Inotrope and Why?

Primary function of cardiovascular system is to meet body's metabolic demands. The aim of inotrope therapy is to minimise adverse impact of cardiovascular compromise. Current use of inotropes is primarily guided by the pathophysiology of cardiovascular compromise and anticipated actions of inotropes. Lack of significant reduction in morbidity and mortality associated with cardiovascular compromise despite inotrope use, highlights major gaps in our understanding of circulatory targets, thresholds and choices of inotrope therapy. Thus far, prevention of cardiovascular compromise remains the most effective strategy to optimize outcomes. Studies of alternative design are needed for further advancement in cardiovascular therapy in neonates.

Epidural anesthesia and hypotension in pheochromocytoma and paraganglioma

Postoperative hypotension frequently occurs after resection of pheochromocytoma and/or paraganglioma (PPGLs). Epidural anesthesia (EA) is often used for pain control in open resection of these tumors; one of its side effects is hypotension. Our aim is to determine if EA is associated with an increased risk of postoperative hypotension after open resection of PPGLs. We conducted a retrospective review of patients who underwent open resection of PPGLs at the National Institutes of Health from 2004 to 2019. Clinical and perioperative parameters were analyzed by the use of EA. The primary endpoint was postoperative hypotension. Ninety-seven patients (46 female and 51 male; mean age, 38.5 years) underwent open resection of PPGLs and 69 (71.1%) received EA. Patients with EA had a higher rate beta-blocker use (79.7% vs 57.1%, P = 0.041), metastasis (69.6% vs 39.3%, P = 0.011), and were more frequently hypotensive after surgery (58.8% vs 25.0%, P = 0.003) compared to those without EA. Patients with postoperative hypotension had higher plasma normetanephrines than those without (7.3 fold vs 4.1 fold above the upper limit of normal, P = 0.018). Independent factors associated with postoperative hypotension include the use of beta-blockers (HR = 3.35 (95% CI: 1.16-9.67), P = 0.026) and EA (HR = 3.49 (95% CI: 1.25-9.76), P = 0.017). Data from this retrospective study suggest that, in patients with open resection of PPGLs, EA is an independent risk factor for early postoperative hypotension. Special caution is required in patients on beta-blockade. A prospective evaluation with standardized protocols for the use of EA and management of hemodynamic variability is necessary.

Effects of Proximal and Distal Enteral Glucose Infusion on Cardiovascular Response in Health and Type 2 Diabetes

CONTEXT

Exposure of the small intestine to nutrients frequently leads to marked reductions in blood pressure (BP) in type 2 diabetes (T2DM). It remains unclear whether the region of the gut exposed to nutrients influences postprandial cardiovascular responses.

OBJECTIVE

To evaluate the cardiovascular responses to proximal and distal small intestinal glucose infusion in health and T2DM.

DESIGN

Double-blind, randomized, crossover design.

SETTING

Single center in Australia.

PATIENTS

10 healthy subjects and 10 T2DM patients.

INTERVENTIONS

Volunteers were studied on 2 occasions, when a transnasal catheter was positioned with infusion ports opening 13 cm and 190 cm beyond the pylorus. A 30-g bolus of glucose was infused into either site and 0.9% saline into the alternate site over 60 minutes.

MAIN OUTCOME MEASURES

BP, heart rate (HR), and superior mesenteric artery (SMA) blood flow were measured over 180 minutes.

RESULTS

Systolic BP was unchanged in response to both infusions in health, but decreased in T2DM, with a greater reduction after proximal versus distal infusion (all P ≤ .01). The increment in HR did not differ between treatments in health, but was greater after distal versus proximal infusion in T2DM (P = .02). The increases in SMA blood flow were initially greater, but less sustained, with proximal versus distal infusion in health (P < .001), a pattern less evident in T2DM.

CONCLUSIONS

In T2DM, postprandial hypotension may be mitigated by diversion of nutrients from the proximal to the distal small intestine.

A retrospective cohort analysis for the risk factors of intraoperative hypotension

AIM OF THE STUDY

To reveal the risk factors of intraoperative hypotension (IH) and investigate whether IH was corrected in time.

METHODS USED TO CONDUCT THE STUDY

This retrospective cohort study included patients undergoing surgeries in one medical centre. We divided all patients into two groups, the IH group and non-IH group. The clinical features of these two groups were compared and the independent risk factors for IH were analysed.

RESULTS OF THE STUDY

A total of 5864 non-cardiac surgery patients were included, of which 931 patients had IH diagnose. The independent risk factors of IH include older age, high grade American Society of Anaesthesiologists (ASA) physical status, intrathecal anaesthesia, emergency surgery and medical history of hypertension (P < .01). Among the patients with IH, 44.5% had hypotension lasting between 30 and 120 minutes, and 25.2% had hypotension lasting >120 minutes. Patients with IH are more likely to develop major post-operative complications after surgery (P < .01).

CONCLUSIONS

The independent risk factors of IH include older age, high grade ASA physical status, intrathecal anaesthesia, emergency surgery and history of hypertension. Hypotension during surgery is not always effectively treated.

Recurrent probabilistic neural network-based short-term prediction for acute hypotension and ventricular fibrillation

In this paper, we propose a novel method for predicting acute clinical deterioration triggered by hypotension, ventricular fibrillation, and an undiagnosed multiple disease condition using biological signals, such as heart rate, RR interval, and blood pressure. Efforts trying to predict such acute clinical deterioration events have received much attention from researchers lately, but most of them are targeted to a single symptom. The distinctive feature of the proposed method is that the occurrence of the event is manifested as a probability by applying a recurrent probabilistic neural network, which is embedded with a hidden Markov model and a Gaussian mixture model. Additionally, its machine learning scheme allows it to learn from the sample data and apply it to a wide range of symptoms. The performance of the proposed method was tested using a dataset provided by Physionet and the University of Tokyo Hospital. The results show that the proposed method has a prediction accuracy of 92.5% for patients with acute hypotension and can predict the occurrence of ventricular fibrillation 5 min before it occurs with an accuracy of 82.5%. In addition, a multiple disease condition can be predicted 7 min before they occur, with an accuracy of over 90%.

Pulmonary Edema in COVID19-A Neural Hypothesis

In COVID-19, lung manifestations present as a slowly evolving pneumonia with insidious early onset interstitial pulmonary edema that undergoes acute exacerbation in the late stages and microvascular thrombosis. Currently, these manifestations are considered to be only consequences of pulmonary SARS-CoV-2 virus infection. We are proposing a new hypothesis that neurogenic insult may also play a major role in the pathogenesis of these manifestations. SARS-CoV-2 mediated inflammation of the nucleus tractus solitarius (NTS) may play a role in the acute exacerbation of pulmonary edema and microvascular clotting in COVID-19 patients.

Peculiarities of Autonomic Regulation of the Heart in Experimental Normobaric Hypoxia of Different Genesis

We compared autonomic regulation of the heart in Wistar rats with acute exogenous hypoxic and chronic normobaric hypoxia against the background of experimental chronic obstructive pulmonary disease. In animals subjected to normobaric hypoxia, dysfunction of the autonomic regulation of the heart developed; it manifested in a significant limitation of the effects of the parasympathetic and sympathetic nervous systems on the pacemaker activity of the sinoatrial node. Disturbances in autonomic regulation of the heart in acute exogenous hypoxic normobaric hypoxia were characterized by "rigid" heart rhythm and bradycardia in the presence of systolic-diastolic arterial hypotension. Centralization of heart rhythm control did not provide compensation for hemodynamic disturbances. In case of chronic normobaric hypoxia, an increase in arterial hypoxemia was associated with protective "denervation" of the heart against the background of increased activity of the humoral regulation, which manifested in tachycardia, isolated systolic arterial hypertension, and overstrain of regulatory systems.

Monitoring of cardiovascular physiology augmented by a patient-specific biomechanical model during general anesthesia. A proof of concept study

During general anesthesia (GA), direct analysis of arterial pressure or aortic flow waveforms may be inconclusive in complex situations. Patient-specific biomechanical models, based on data obtained during GA and capable to perform fast simulations of cardiac cycles, have the potential to augment hemodynamic monitoring. Such models allow to simulate Pressure-Volume (PV) loops and estimate functional indicators of cardiovascular (CV) system, e.g. ventricular-arterial coupling (Vva), cardiac efficiency (CE) or myocardial contractility, evolving throughout GA. In this prospective observational study, we created patient-specific biomechanical models of heart and vasculature of a reduced geometric complexity for n = 45 patients undergoing GA, while using transthoracic echocardiography and aortic pressure and flow signals acquired in the beginning of GA (baseline condition). If intraoperative hypotension (IOH) appeared, diluted norepinephrine (NOR) was administered and the model readjusted according to the measured aortic pressure and flow signals. Such patients were a posteriori assigned into a so-called hypotensive group. The accuracy of simulated mean aortic pressure (MAP) and stroke volume (SV) at baseline were in accordance with the guidelines for the validation of new devices or reference measurement methods in all patients. After NOR administration in the hypotensive group, the percentage of concordance with 10% exclusion zone between measurement and simulation was >95% for both MAP and SV. The modeling results showed a decreased Vva (0.64±0.37 vs 0.88±0.43; p = 0.039) and an increased CE (0.8±0.1 vs 0.73±0.11; p = 0.042) in hypotensive vs normotensive patients. Furthermore, Vva increased by 92±101%, CE decreased by 13±11% (p < 0.001 for both) and contractility increased by 14±11% (p = 0.002) in the hypotensive group post-NOR administration. In this work we demonstrated the application of fast-running patient-specific biophysical models to estimate PV loops and functional indicators of CV system using clinical data available during GA. The work paves the way for model-augmented hemodynamic monitoring at operating theatres or intensive care units to enhance the information on patient-specific physiology.

Dexmedetomidine aggravates hypotension following mesenteric traction during total gastrectomy: a randomized controlled trial

BACKGROUND

Mesenteric traction syndrome (MTS), which is characterized by arterial hypotension and tachycardia following mesenteric traction (MT), frequently occurs during abdominal surgery. Dexmedetomidine, commonly used in general anesthesia during major surgery, has a sympatholytic effect and attenuates the compensatory response to hypotension.

OBJECTIVE

Assess the effect of dexmedetomidine on hypotension following mesenteric traction.

DESIGN

Prospective, randomized, controlled clinical trial.

SETTING

Department of Anesthesiology, Zhenjiang First People's Hospital in China.

PATIENTS AND METHODS

Patients were randomly divided into three groups. Dexmedetomidine, 0.5 or 1.0 µg/kg, was intravenously administered over 15 minutes before skin incision followed by a maintenance rate of 0.5 µg/kg/h in groups D1 and D2, respectively; saline was administered in group C.

MAIN OUTCOME MEASURE(S)

The duration of hypotension, heart rate and plasma norepinephrine level in patients with MTS were recorded within 60 minutes following MT.

SAMPLE SIZE

75 patients.

RESULTS

The duration of hypotension in the MTS patients in group D1 and D2 was significantly longer than that in groups C (D1 vs. C, P<.05; D2 vs. C, P<.01). Significantly more phenylephrine was required to treat hypotension in group D1 and D2 than was required for patients in group C (P<.05). The increase in heart rate during the first 15 minutes of MT in group D2 was significantly attenuated compared to that in group C (P<.0083). The increases in norepinephrine levels during the first 15 minutes of MT in group C were significantly higher than those in groups D1 and D2 (P<.0167).

CONCLUSION

Adjunctive dexmedetomidine in general anesthesia aggravates hypotension during MTS in open total gastrectomy.

LIMITATIONS

Postoperative complications were not evaluated.

CONFLICT OF INTEREST

None.

Correlation between body composition measurement by bioelectrical impedance analysis and intradialytic hypotension

OBJECTIVE

To explore the correlation between body composition measurement by bioelectrical impedance analysis (BIA) and intradialytic hypotension (IDH).

METHODS

The clinical data of 127 patients with end-stage renal disease (ESRD) who underwent regular dialysis in the Blood Purification Center of the Second Affiliated Hospital of Chongqing Medical University were retrospectively analyzed. According to the occurrence of IDH, the patients were divided into IDH group and intradialytic normotension group. The difference in body composition measured by BIA and its relationship with IDH were compared between the two groups.

RESULTS

Compared with intradialytic normotension group, the intracellular water (ICW) ratio (P = 0.009), extracellular water (ECW) ratio (P = 0.029), total body water (TBW) ratio (P = 0.012), protein ratio (P = 0.010), soft lean mass (SLM) ratio (P = 0.011), fat-free mass (FFM) ratio (P = 0.012) and skeletal muscle mass (SMM) ratio (P = 0.009) in IDH group were significantly decreased. However, the fat mass (FM) ratio (P = 0.016), percentage body fat (PBF) ratio (P = 0.001), extracellular water/total body water (ECW/TBW) ratio (P = 0.036), extracellular water/total body water in trunk (ECW/TBWT) ratio (P = 0.045) and visceral fat area (VFA) (P = 0.003) in IDH group were significantly increased when compared with intradialytic normotension group. In addition, there was a positive correlation between systolic blood pressure (SBP) during IDH and ECW ratio, ECW/TBW ratio, and ECW/TBWTR ratio before dialysis.

CONCLUSIONS

The body composition of dialysis patients is closely related to the occurrence of IDH. Strengthening the body composition management of dialysis patients outside the hospital may reduce the occurrence of IDH and improve the long-term prognosis of dialysis patients.

Hypotensive effect of Eugenia dysenterica leaf extract is primarily related to its vascular action: The possible underlying mechanisms

ETHNOPHARMACOLOGICAL RELEVANCE

Eugenia dysenterica (ED) leaves are used in Brazil to treat cardiac diseases; however, there are no scientific data describing the effects of this species on cardiac activity.

AIM OF THE STUDY

To investigate the effect of ED aqueous leaf extract (EDLE) on hear rate (HR) and mean arterial pressure (MAP) of anaesthetised rats and its underlying mechanism of action.

MATERIAL AND METHODS

EDLE was analysed, and its proanthocyanidin composition was determined. After performing dose-effect curves for EDLE on HR and MAP, EDLE-induced hypotension was evaluated before and after atropine (AT), L-N(ω)-nitro-L-arginine methyl ester (L-NAME), hexamethonium (HXT), indomethacin (IND), carbenoxolone (CBX), or nifedipine (NFD) administration. The effect of proanthocyanidin-depleted extract (EDLE/P-) was also determined and compared to that of the EDLE with proanthocyanidins.

RESULTS

EDLE decreased the MAP in a dose-dependent manner; HR was decreased only with the highest and most toxic dose. Only CBX and NFD decreased EDLE-induced hypotension. Five polymeric series of proanthocyanidins were identified, which were mainly constituted by procyanidin and prodelphinidin units with B-type linkage and up to 12 flavan-3-ol units. EDLE/P- induced hypotension did not differ from that induced by EDLE.

CONCLUSIONS

The cardiovascular effects of EDLE were primarily related to its vascular action. EDLE-induced hypotensive effect appeared to involve L-type calcium channel blockage as well as myoendothelial gap junction signalling. The higher molecular weight proanthocyanidins from EDLE are unlikely to contribute to its cardiovascular effect.

Carotid Artery Corrected Flow Time and Respiratory Variations of Peak Blood Flow Velocity for Prediction of Hypotension After Induction of General Anesthesia in Adult Patients Undergoing Elective Surgery: A Prospective Observational Study

OBJECTIVES

Hypotension is common after induction of general anesthesia, and intraoperative hypotension is associated with postoperative end-organ injury such as acute kidney injury and myocardial ischemia. This study was designed to determine the utility of the carotid corrected flow time (cFT) and carotid artery peak blood flow velocity variation (ðV_peak ) for prediction of hypotension after induction of general anesthesia.

METHODS

Adult patients (n = 112) undergoing any elective surgery under general anesthesia who fasted for at least 6 to 8 hours were recruited in this prospective observational study. The common carotid artery cFT and ðV_peak were measured with ultrasound 10 minutes before induction of general anesthesia. After that, general anesthesia with propofol was used, and hemodynamic data were collected until 3 minutes after induction of anesthesia.

RESULTS

The carotid cFT was significantly correlated with percentages of the fall in the systolic blood pressure at 2 minutes (P < .0001) and 3 minutes (P < .0001) and percentages of the fall in the mean arterial pressure at 1 minute (P = .0006), 2 minutes (P < .0001), and 3 minutes (P < .0001). The cFT was a predictor of hypotension after induction of general anesthesia, with an area under the receiver operating characteristic curve of 0.91. The best cutoff value obtained from this study was 330.2 milliseconds or less, which predicted postinduction hypotension with sensitivity and specificity of 85.7% and 96.8%, respectively. The ðV_peak was an inferior predictor of postinduction hypotension, with an area under the receiver operating characteristic curve of 0.68. The optimum cutoff value was 18.8%, with sensitivity and specificity of 61.9% and 67.4%.

CONCLUSIONS

The cFT measured in the common carotid artery is a reasonable predictor of hypotension after induction of general anesthesia in American Society of Anesthesiologists physical status I and II patients. Further studies are required to identify its role in high-risk patients such as older groups and patients with cardiovascular diseases and also to identify interobserver and intraobserver variability of cFT and ðV_peak measurements.

Acetaminophen (Paracetamol) Metabolites Induce Vasodilation and Hypotension by Activating Kv7 Potassium Channels Directly and Indirectly

OBJECTIVE

Intravenous acetaminophen/paracetamol (APAP) is well documented to cause hypotension. Since the patients receiving intravenous APAP are usually critically ill, any severe hemodynamic changes, as with those associated with APAP, can be life-threatening. The mechanism underlying this dangerous iatrogenic effect of APAP was unknown. Approach and Results: Here, we show that intravenous APAP caused transient hypotension in rats, which was attenuated by the Kv7 channel blocker, linopirdine. APAP metabolite N-acetyl-p-benzoquinone imine caused vasodilatation of rat mesenteric arteries ex vivo. This vasodilatation was sensitive to linopirdine and also the calcitonin gene-related peptide antagonist, BIBN 4096. Further investigation revealed N-acetyl-p-benzoquinone imine stimulates calcitonin gene-related peptide release from perivascular nerves, causing a cAMP-dependent activation of Kv7 channels. We also show that N-acetyl-p-benzoquinone imine enhances Kv7.4 and Kv7.5 channels overexpressed in oocytes, suggesting that it can activate Kv7.4 and Kv7.5 channels directly, to elicit vasodilatation.

CONCLUSIONS

Direct and indirect activation of Kv7 channels by the APAP metabolite N-acetyl-p-benzoquinone imine decreases arterial tone, which can lead to a drop in blood pressure. Our findings provide a molecular mechanism and potential preventive intervention for the clinical phenomenon of intravenous APAP-dependent transient hypotension.

Autonomic function, postprandial hypotension and falls in older adults at one year after critical illness

OBJECTIVE

Postprandial hypotension occurs frequently in older survivors of critical illness at 3 months after discharge. We aimed to determine whether postprandial hypotension and its predictors - gastric dysmotility and cardiovascular autonomic dysfunction - persist or resolve as older survivors of critical illness recover, and whether postprandial hypotension after intensive care unit (ICU) discharge is associated with adverse outcomes at 12 months.

DESIGN

Prospective observational study.

SETTING

Tertiary medical-surgical ICU.

PARTICIPANTS

Older adults (aged ≥ 65 years) who had been studied 3 months after ICU discharge and who returned for a follow-up study at 12 months after discharge.

MAIN OUTCOME MEASURES

On both occasions after fasting overnight, participants consumed a 300 mL drink containing 75 g glucose, radiolabelled with 20 MBq 99mTcphytate. Blood pressure, heart rate, blood glucose concentration and gastric emptying rate were measured concurrently before and after ingestion of the drink. Falls, quality of life, hospitalisation and mortality rates were also quantified.

RESULTS

Out of 35 older adults studied at 3 months, 22 returned for the follow-up study at 12 months. Postprandial hypotension was evident in 29% of participants (95% CI, 14-44%) at 3 months and 10% of participants (95% CI, 1-30%) at 12 months. Postprandial hypotension at 3 months was associated with a more than threefold increase in the risk of falls in the year after ICU discharge (relative risk, 3.7 [95% CI, 1.6-8.8]; P = 0.003). At 12 months, gastric emptying was normal (mean time taken for 50% of gastric contents to empty, 101.6 [SD, 33.3] min) and cardiovascular autonomic dysfunction prevalence was low (9% [95% CI, 1-29%]).

CONCLUSIONS

In older adults who were evaluated 3 and 12 months after ICU discharge, postprandial hypotension at 3 months was associated with an increased risk of subsequent falls, but the prevalence of postprandial hypotension decreased with time.

The effect of intravenous maropitant on blood pressure in healthy awake and anesthetized dogs

OBJECTIVE

To evaluate the effects of intravenous maropitant on arterial blood pressure in healthy dogs while awake and under general anesthesia.

DESIGN

Experimental crossover study.

ANIMALS

Eight healthy adult Beagle dogs.

PROCEDURE

All dogs received maropitant (1 mg kg-1) intravenously under the following conditions: 1) awake with non-invasive blood pressure monitoring (AwNIBP), 2) awake with invasive blood pressure monitoring (AwIBP), 3) premedication with acepromazine (0.005 mg kg-1) and butorphanol (0.2 mg kg-1) intramuscularly followed by propofol induction and isoflurane anesthesia (GaAB), and 4) premedication with dexmedetomidine (0.005 mg kg-1) and butorphanol (0.2 mg kg-1) intramuscularly followed by propofol induction and isoflurane anesthesia (GaDB). Heart rate (HR), systolic (SAP), diastolic (DAP), and mean blood pressures (MAP) were recorded before injection of maropitant (baseline), during the first 60 seconds of injection, during the second 60 seconds of injection, at the completion of injection and every 2 minutes post injection for 18 minutes. The data were compared over time using a Generalized Linear Model with mixed effects and then with simple effect comparison with Bonferroni adjustments (p <0.05).

RESULTS

There were significant decreases from baseline in SAP in the GaAB group (p < 0.01) and in MAP and DAP in the AwIBP and GaAB (p < 0.001) groups during injection. A significant decrease in SAP (p < 0.05), DAP (p < 0.05), and MAP (p < 0.05) occurred at 16 minutes post injection in GaDB group. There was also a significant increase in HR in the AwIBP group (p < 0.01) during injection. Clinically significant hypotension occurred in the GaAB group with a mean MAP at 54 ± 6 mmHg during injection.

CONCLUSION

Intravenous maropitant administration significantly decreases arterial blood pressure during inhalant anesthesia. Patients premedicated with acepromazine prior to isoflurane anesthesia may develop clinically significant hypotension.

Ability of an Arterial Waveform Analysis-Derived Hypotension Prediction Index to Predict Future Hypotensive Events in Surgical Patients

BACKGROUND

Intraoperative hypotension is associated with worse perioperative outcomes for patients undergoing major noncardiac surgery. The Hypotension Prediction Index is a unitless number that is derived from an arterial pressure waveform trace, and as the number increases, the risk of hypotension occurring in the near future increases. We investigated the diagnostic ability of the Hypotension Prediction Index in predicting impending intraoperative hypotension in comparison to other commonly collected perioperative hemodynamic variables.

METHODS

This is a 2-center retrospective analysis of patients undergoing major surgery. Data were downloaded and analyzed from the Edwards Lifesciences EV1000 platform. Receiver operating characteristic curves were constructed for the Hypotension Prediction Index and other hemodynamic variables as well as event rates and time to event.

RESULTS

Two hundred fifty-five patients undergoing major surgery were included in the analysis yielding 292,025 data points. The Hypotension Prediction Index predicted hypotension with a sensitivity and specificity of 85.8% (95% CI, 85.8%-85.9%) and 85.8% (95% CI, 85.8%-85.9%) 5 minutes before a hypotensive event (area under the curve, 0.926 [95% CI, 0.925-0.926]); 81.7% (95% CI, 81.6%-81.8%) and 81.7% (95% CI, 81.6%-81.8%) 10 minutes before a hypotensive event (area under the curve, 0.895 [95% CI, 0.894-0.895]); and 80.6% (95% CI, 80.5%-80.7%) and 80.6% (95% CI, 80.5%-80.7%) 15 minutes before a hypotensive event (area under the curve, 0.879 [95% CI, 0.879-0.880]). The Hypotension Prediction Index performed superior to all other measured hemodynamic variables including mean arterial pressure and change in mean arterial pressure over a 3-minute window.

CONCLUSIONS

The Hypotension Prediction Index provides an accurate real time and continuous prediction of impending intraoperative hypotension before its occurrence and has superior predictive ability than the commonly measured perioperative hemodynamic variables.

Longitudinal Changes in the Blood Pressure Responses to, and Gastric Emptying of, an Oral Glucose Load in Healthy Older Subjects

The rate of gastric emptying is a major determinant of the hypotensive response to a meal. Cross-sectional studies suggest that healthy aging is associated with a modest slowing of gastric emptying. We aimed to determine longitudinal changes in the blood pressure (BP) response to, and gastric emptying of, glucose in healthy older people. Thirty-three participants (77.0 ± 0.7 years) had baseline and follow-up measurements after 5.8 ± 0.1 years. Participants consumed a 300-mL drink containing 75 g glucose and 150 mg C13-acetate. BP and heart rate (HR) were measured at 5-minute intervals for 120 minutes after the drink. Exhaled breath was collected to calculate the gastric 50% emptying time. The prevalence of postprandial hypotension (PPH) doubled from 9.1% to 18.2%. Gastric emptying was slower at follow-up (p = .04). The fall in systolic BP (SBP) was related directly to the rate of gastric emptying at both the initial study (r = .54, p = .005) and at follow-up (r = .41, p = .04). The change in the maximum fall in SBP was related to the increase in baseline SBP (r = -.63, p < .001). In conclusion, in healthy older people over a period of ~5.8 years, there was an increased prevalence of PPH and a modest slowing of gastric emptying. The latter was related directly to a greater hypotensive response.

Comparison of effects and safety in providing controlled hypotension during surgery between dexmedetomidine and magnesium sulphate: A meta-analysis of randomized controlled trials

Background

Effectiveness of controlled hypotension has been proven in alleviating intraoperative bleeding. Many recent studies emphasized the efficacy of dexmedetomidine and magnesium in providing controlled hypotension during various surgeries. The present meta-analysis of randomized controlled trials (RCTs) was performed to evaluate comprehensively the effects and safety of these two medications.

Methods

Literature search was performed in four databases from inception to April 2019. All RCTs that used dexmedetomidine and magnesium as hypotensive agents were enrolled. The outcomes contained bleeding condition of surgical site, hemodynamic parameters, duration of surgeries, number of patients requiring opioid/analgesia administration, recovery period, and adverse events emerged during surgeries.

Results

Ten studies with 663 patients met with our inclusion criteria. The results indicated that both bleeding score and values of mean arterial pressure (MAP) and heart rate (HR) were significantly lower in patients receiving dexmedetomidine (SMD 1.65 with 95% CI [0.90,2.41], P<0.00001) compared to the patients receiving magnesium. The effect in decreasing the necessity of using opioid/analgesia was affirmative in dexmedetomidine group (29.13% with magnesium vs 10.78% with dexmedetomidine), and the condition was more favorable in magnesium group in reducing recovery period (SMD -1.98 with 95% CI [-4.27,0.30], P = 0.09). Compared with magnesium, using of dexmedetomidine was associated with higher incidence of bradycardia but lower incidence of nausea and vomiting.

Conclusion

Compared with magnesium, dexmedetomidine is more effective to provide promising surgical field condition, favorable controlled hypotension, and less necessity of opioid or analgesia administration. But long recovery period and high-probability bradycardia should be deliberated.

Evaluation of cerebral oxygen perfusion during shoulder arthroplasty performed in the semi-beach chair position

BACKGROUND

The beach chair position is commonly used when performing shoulder arthroplasty. However, this position has been associated with hypotension, potentially leading to cerebral hypoperfusion, which may cause neurologic injury. In addition, shoulder arthroplasty cases are associated with longer operative times, posing a potentially greater risk of cerebral hypoperfusion. We aim to evaluate the risk of cerebral desaturation events (CDEs) during the course of total shoulder arthroplasty.

METHODS

Twenty-six patients undergoing shoulder arthroplasties were monitored for changes in cerebral perfusion. Seven specific time-points during the procedure were labeled for comparison of events: baseline, beach chair, incision, humeral broaching, glenoid reaming, glenoid component implantation, and humeral component implantation. Cerebral oxygen perfusion was measured using near-infrared spectroscopy. A CDE was described as a decrease of oxygen saturation greater than 20%.

RESULTS

Nineteeen of 25 subjects experienced a CDE. 42% of these patients experienced CDEs during semi-beach chair positioning. Patients experienced the largest oxygen saturation drop during semi-beach chair positioning. Transition from baseline to semi-beach chair was the only event to have a statistically significant decrease in cerebral perfusion (8%, P < .05). There was a statistically significant percentage change in mean oxygen saturation in the semi-beach chair interval (10%, P < .01) and the semi-beach chair to incision interval (7%, P < .01).

CONCLUSIONS

Most patients experienced an intraoperative CDE, with greatest incidence during semi-beach chair positioning. The largest decline in cerebral oxygen saturation occurred during semi-beach chair positioning. Implant implantation was not associated with decrease in cerebral oximetry.

The effects of isobaric and hyperbaric bupivacaine on maternal hemodynamic changes post spinal anesthesia for elective cesarean delivery: A prospective cohort study

BACKGROUND

Spinal anesthesia is a form of regional anesthesia frequently used in various lower abdominal, orthopedic, obstetric operations such as a cesarean delivery. The most common local anesthetic used for spinal anesthesia in obstetric and non-obstetric surgery is bupivacaine which can be utilized as an isobaric or hyperbaric solution, producing differences in maternal hemodynamic changes. Against this backdrop, the study aims to compare the effects of isobaric and hyperbaric bupivacaine on maternal hemodynamic alterations after administering spinal anesthesia for elective cesarean delivery at Gandhi Memorial Hospital, Addis Ababa, Ethiopia.

METHODS

A hospital-based prospective cohort study design was employed for the period December 1, 2017 to January 30, 2018. A total of 100 parturient were involved, with one group exposed to isobaric bupivacaine and the other to hyperbaric bupivacaine to observe their effects on maternal hemodynamic changes post spinal anesthesia. The participants were selected through systematic random sampling. Data analysis was performed using SPSS (version 20) through descriptive statistic, independent sample t-test, Mann-Whitney U-test, Fisher's exact test, and Chi-square test were used. P values of <0.05 was assumed as statistically significant for all tests.

RESULTS

The incidence of hypotension was found to be greater in isobaric than hyperbaric groups (82% vs. 60% respectively; p = 0.015). No statistical significant differences were found in mean arterial pressure value at baseline, but, statistically significant changes were observed among the groups (p <0.05) at all study timing after spinal anesthesia, except at 30thmin. No statistically significant differences were seen in the mean heart rate variability after spinal anesthesia at all periods, except the 15th minute (p = 0.033). A greater rate of vasopressor was used in the isobaric group as compared to the hyperbaric group (36% vs. 14% respectively; p = 0.011).

CONCLUSION

Baricity is a significant factor in maternal hemodynamic changes in the parturient for elective cesarean section. Isobaric bupivacaine produces greater change in blood pressure and incidence of hypotension and entails a greater vasopressor requirement than hyperbaric bupivacaine after spinal anesthesia for elective cesarean section.

Dexmedetomidine Sedation for Paroxysmal Supraventricular Tachycardia Ablation Is Not Associated With Alteration of Arrhythmia Inducibility

BACKGROUND

Dexmedetomidine (Dex) is an attractive agent for procedural sedation due to its unique pharmacodynamic profile, specifically affording predictable sedation without concurrent respiratory depression. However, Dex has previously been reported to prevent or terminate arrhythmias. The purpose of this study was to investigate paroxysmal supraventricular tachycardia (PSVT) inducibility and homeostatic stability during electrophysiology studies (EPSs) and ablation when a standardized Dex protocol was used as the primary sedation agent.

METHODS

We performed a retrospective review of 163 consecutive procedures for PSVT ablation that received Dex as the primary sedative with adjunct fentanyl and midazolam boluses (DEX-FENT-MIDAZ). This cohort was compared to 163 consecutive control procedures wherein strictly fentanyl and midazolam were used for sedation. The primary outcome reviewed was PSVT inducibility assessed before ablation. Reviewed secondary outcomes included level of sedation and intraprocedure hemodynamics and oxygenation.

RESULTS

The arrhythmia profiles of the DEX-FENT-MIDAZ and control cohorts were very similar. The overall incidence of a "negative" EPSs in which arrhythmia was not induced was 24% in the DEX-FENT-MIDAZ group and 26% in the control group (P = .7). Unintended deep sedation was significantly less with DEX-FENT-MIDAZ (4.3% vs 27%; P ≤ .0001). However, DEX-FENT-MIDAZ use was associated with a higher incidence of intraprocedure hypotension.

CONCLUSIONS

Dex sedation during EPSs is not associated with a reduction in PSVT inducibility. The therapeutic utility of Dex during EPS arises from the predictable sedation Dex affords but is associated with an increased incidence of intraprocedure hypotension.

Benefits and harms of lower blood pressure treatment targets: systematic review and meta-analysis of randomised placebo-controlled trials

OBJECTIVES

To assess the effect of antihypertensive treatment in the 130-140 mm Hg systolic blood pressure range.

DESIGN

Systematic review and meta-analysis.

INFORMATION SOURCES

PubMed, CDSR and DARE were searched for the systematic reviews, which were manually browsed for clinical trials. PubMed and Cochrane Central Register of Controlled Trials were searched for trials directly in February 2018.

ELIGIBILITY CRITERIA

Randomised double-blind trials with ≥1000 patient-years of follow-up, comparing any antihypertensive agent against placebo.

DATA EXTRACTION AND RISK OF BIAS

Two reviewers extracted study-level data, and assessed risk of bias using Cochrane Collaborations risk of bias assessment tool, independently.

MAIN OUTCOMES AND MEASURES

Primary outcomes were all-cause mortality, major cardiovascular events and discontinuation due to adverse events. Secondary outcomes were cardiovascular mortality, myocardial infarction, stroke, heart failure, hypotension-related adverse events and renal impairment.

RESULTS

Eighteen trials, including 92 567 participants (34% women, mean age 63 years), fulfilled the inclusion criteria. Primary preventive antihypertensive treatment was associated with a neutral effect on all-cause mortality (relative risk 1.00, 95% CI 0.95 to 1.06) and major cardiovascular events (1.01, 0.96 to 1.06), but an increased risk of discontinuation due to adverse events (1.23, 1.03 to 1.47). None of the secondary efficacy outcomes were significantly reduced, but the risk of hypotension-related adverse events increased with treatment (1.71, 1.32 to 2.22). In coronary artery disease secondary prevention, antihypertensive treatment was associated with reduced risk of all-cause mortality (0.91, 0.83 to 0.99) and major cardiovascular events (0.85, 0.77 to 0.94), but doubled the risk of adverse events leading to discontinuation (2.05, 1.62 to 2.61).

CONCLUSION

Primary preventive blood pressure lowering in the 130-140 mm Hg systolic blood pressure range adds no cardiovascular benefit, but increases the risk of adverse events. In the secondary prevention, benefits should be weighed against harms.

PROSPERO REGISTRATION NUMBER

CRD42018088642.

Point-of-care blood analysis of hypotensive patients in the emergency department

OBJECTIVE

The aim of this study is to compare a point-of-care (POC) analysis, Enterprise POC (epoc), using the capillary blood obtained from skin puncture with conventional laboratory tests using arterial and venous blood in hypotensive patients.

METHODS

This study was conducted at the emergency department of a tertiary care hospital between June and November 2018. 231 hypotensive patients were enrolled. Three types of blood samples (capillary blood from skin puncture and arterial and venous blood from blood vessel puncture) were collected and analyzed. We compared a total of 13 parameters (pH, pCO2, pO2, HCO3-, Ca2+, lactate, Na+, K+, Cl-, glucose, Hb, Hct, and creatinine) between the POC analysis and reference analyzers by performing the equivalence test and Bland-Altman plot analysis.

RESULTS

In hypotensive patients, with the exception of two parameters (pCO2, pO2), the pH, HCO3-, Ca2+, lactate, Na+, K+, Cl-, glucose, Hb, Hct, and creatinine parameters measured by the POC analysis were equivalent to or correlated with the reference values. In the patients with cardiac arrest group, nine parameters (pH, HCO3-, Ca2+, Na+, K+, glucose, Hb, Hct, and creatinine) analyzed by the epoc system were equivalent to the reference values.

CONCLUSION

Most parameters, except pO2, measured by the epoc system using the capillary blood in hypotensive patients were equivalent to or correlated with those measured by the reference analyzers.

Impact of intraoperative blood pressure, blood pressure fluctuation, and pulse pressure on postoperative delirium in elderly patients with hip fracture: A prospective cohort study

AIM

Postoperative delirium (PD) is a frequent complication of hip fracture surgery, but its pathophysiology remains poorly understood. We investigated the impact of a single episode of intraoperative hyper/hypotension, blood pressure (BP) fluctuation (ΔMAP), and pulse pressure (PP) on hyper/hypoactive PD in elderly patients undergoing surgery for hip fracture. We also assessed the effect of PD on clinical outcomes.

METHODS

This was a prospective 1-year follow-up study of patients over 60 years of age with a primary diagnosis of acute low-energy hip fracture. Perioperative delirium was assessed using the Confusion Assessment Method (CAM); the development of PD and the type, hyperactive or hypoactive PD, were recorded. Cognitive assessment was evaluated using the Short Portable Mental Status Questionnaire (SPMSQ). The lowest and highest BP values were extracted from the patients' anaesthesia charts. Postoperative complications, reinterventions and 1-month mortality were recorded.

RESULTS

PD occurred in 148 (53%) patients during the first postoperative week, with 75% of the cases diagnosed as hypoactive PD. Patients developing PD of any type were older, had a lower body mass index, higher SPMSQ and Charlson scores, more severe systemic diseases, a lower lowest intraoperative BP, a higher ΔMAP, a lower PP, and a higher postoperative pain score. They also took more drugs and received more blood transfusion intraoperatively. Multivariate logistic regression analyses showed that a higher MAP min had a protective effect on the occurrence of any type of PD, as well as hypoactive and hyperactive. PD had negative effect on outcomes.

CONCLUSION

Our results provide evidence of an association between maximal hypotension, the lowest intraoperative mean blood pressure (MAP), ΔMAP, PP, and PD. A progressive decrease in MAP during surgery was associated with the increased odds of developing either type of PD.

A new mechanism of the protamine-dependent hypotension after cardiopulmonary bypass and the role of calcium

Heparin and protamine are two indispensable agents of cardiopulmonary bypass surgery with effects on the cardiovascular and hematological system. Heparin is used as an anticoagulant in open heart surgery; whereas protamine is used to neutralize heparin effects when surgery is terminated. Protamine is given in order to neutralize heparin effects after cardiopulmonary bypass surgery and it causes hypotension in patients. However, the mechanism of this side effect is not clearly known. Current mechanism is that hypotension occurs after the administration of protamine due to the conformational change in the calcium channels or anaphylactoid thromboxane release or serum ionized calcium levels. The present study was to explain how protamine causes hypotension in evidence-based medicine indexed in PubMed and Web of Science. In addition to above  mechanisms, possibly  the infused protamine binds heparin and causes the coagulation cascade to activate heparin-AT complex on thrombin beside activating FXIa, FXa and FIXa and causing the re-use of Ca2+. The re-use of Ca2+ at the coagulation cascade initiates an anion gap and it is assumed that hypotension develops because of the Ca2+ deficiency. Ca2+ ions are trapped in the thrombus by the resumption of thrombus formation. Ca2+ ions trapped in the thrombus cannot be used, so that Ca2+ ion deficit will develop in circulation and hypotension occurs due to the insufficiency of Ca2+ ions. The administration of Ca2+ ions together with the protamine might help to eliminate the side effect of the protamine (hypotension) while neutralizing heparin after open heart surgery in light of the information provided in the literature.