Impact of Permissive Hypoxia and Hyperoxia Avoidance on Clinical Outcomes in Septic Patients Receiving Mechanical Ventilation: A Retrospective Single-Center Study

BACKGROUND

Septic patients often require mechanical ventilation due to respiratory dysfunction, and effective ventilatory strategies can improve survival. The effects of the combination of permissive hypoxia and hyperoxia avoidance for managing mechanically ventilated patients are unknown. This study examines these effects on outcomes in mechanically ventilated septic patients.

METHODS

In a retrospective before-and-after study, we examined adult septic patients (aged ≥18 years) requiring mechanical ventilation at a university hospital. On April 1, 2017, our mechanical ventilation policy changed from a conventional oxygenation target (SpO2: ≥96%) to more conservative targets with permissive hypoxia (SpO2: 88-92% or PaO2: 60 mmHg) and hyperoxia avoidance (reduced oxygenation for PaO2 > 110 mmHg). Patients were divided into a prechange group (April 2015 to March 2017; n = 83) and a postchange group (April 2017 to March 2019; n = 130). Data were extracted from clinical records and insurance claims. Using a multiple logistic regression model, we examined the association of the postchange group (permissive hypoxia and hyperoxia avoidance) with intensive care unit (ICU) mortality after adjusting for variables such as Sequential Organ Failure Assessment (SOFA) score and PaO2/FiO2 ratios.

RESULTS

The postchange group did not have significantly lower adjusted ICU mortality (0.67, 0.33-1.43; P = 0.31) relative to the prechange group. However, there were significant intergroup differences in mechanical ventilation duration (prechange: 11.0 days, postchange: 7.0 days; P = 0.01) and ICU stay (prechange: 11.0 days, postchange: 9.0 days; P = 0.02).

CONCLUSIONS

Permissive hypoxia and hyperoxia avoidance had no significant association with reduced ICU mortality in mechanically ventilated septic patients. However, this approach was significantly associated with shorter mechanical ventilation duration and ICU stay, which can improve patient turnover and ventilator access.

Polysulfide inhibits hypoxia-elicited hypoxia-inducible factor activation in a mitochondria-dependent manner

In cellular signaling, the diverse physiological actions of biological gases, including O₂, CO, NO, and H₂S, have attracted much interest. Hypoxia-inducible factors (HIFs), including HIF-1 and HIF-2, are transcription factors that respond to reduced intracellular O₂ availability. Polysulfides are substances containing varying numbers of sulfur atoms (H₂S_n) that are generated endogenously from H₂S by 3-mercaptopyruvate sulfurtransferase in the presence of O₂, and regulate ion channels, specific tumor suppressors, and protein kinases. However, the effect of polysulfides on HIF activation in hypoxic mammalian cells is largely unknown. Here, we have investigated the effect of polysulfide on cells in vitro. In established cell lines, polysulfide donors reversibly reduced cellular O₂ consumption and inhibited hypoxia-induced HIF-1α protein accumulation and the expression of genes downstream of HIFs; however, these effects were not observed in anoxia. In Von Hippel-Lindau tumor suppressor (VHL)- and mitochondria-deficient cells, polysulfides did not affect HIF-1α protein synthesis but destabilized it in a VHL- and mitochondria-dependent manner. For the first time, we show that polysulfides modulate intracellular O₂ homeostasis and regulate HIF activation and subsequent hypoxia-induced gene expression in a VHL- and mitochondria-dependent manner.

A rare case of atropine-resistant bradycardia following sugammadex administration

Background

Profound bradycardia caused by sugammadex has been reported, although its mechanism is unclear. Herein, we suggest a possible culprit for this phenomenon.

Case presentation

A 50-year-old woman without comorbidity except mild obesity underwent a transabdominal hysterectomy and right salpingo-oophorectomy. After surgery, sugammadex 200 mg was intravenously administered. Approximately 4 min later, her heart rate decreased to 36 bpm accompanied by hypotension (41/20 mmHg) and ST depression in limb lead electrocardiogram (ECG). Atropine 0.5 mg was injected intravenously without improving the hemodynamics. Intravenous adrenaline 0.5 mg was added despite the lack of signs suggesting allergic reactions. Her heart rate and blood pressure quickly recovered and remained stable thereafter, although 12-lead ECG taken 1 h later still showed ST depression.

Conclusions

In this case, the significant bradycardia appeared attributable to coronary vasospasm (Kounis syndrome) induced by sugammadex, considering the ECG findings and high incidence of anaphylaxis due to sugammadex.

Propofol inhibits stromatoxin-1-sensitive voltage-dependent K+ channels in pancreatic β-cells and enhances insulin secretion

Background

Proper glycemic control is an important goal of critical care medicine, including perioperative patient care that can influence patients’ prognosis. Insulin secretion from pancreatic β-cells is generally assumed to play a critical role in glycemic control in response to an elevated blood glucose concentration. Many animal and human studies have demonstrated that perioperative drugs, including volatile anesthetics, have an impact on glucose-stimulated insulin secretion (GSIS). However, the effects of the intravenous anesthetic propofol on glucose metabolism and insulin sensitivity are largely unknown at present.

Methods

The effect of propofol on insulin secretion under low glucose or high glucose was examined in mouse MIN6 cells, rat INS-1 cells, and mouse pancreatic β-cells/islets. Cellular oxygen or energy metabolism was measured by Extracellular Flux Analyzer. Expression of glucose transporter 2 (GLUT2), potassium channels, and insulin mRNA was assessed by qRT-PCR. Protein expression of voltage-dependent potassium channels (Kv2) was also assessed by immunoblot. Propofol’s effects on potassium channels including stromatoxin-1-sensitive Kv channels and cellular oxygen and energy metabolisms were also examined.

Results

We showed that propofol, at clinically relevant doses, facilitates insulin secretion under low glucose conditions and GSIS in MIN6, INS-1 cells, and pancreatic β-cells/islets. Propofol did not affect intracellular ATP or ADP concentrations and cellular oxygen or energy metabolism. The mRNA expression of GLUT2 and channels including the voltage-dependent calcium channels Cav1.2, Kir6.2, and SUR1 subunit of K_ATP, and Kv2 were not affected by glucose or propofol. Finally, we demonstrated that propofol specifically blocks Kv currents in β-cells, resulting in insulin secretion in the presence of glucose.

Conclusions

Our data support the hypothesis that glucose induces membrane depolarization at the distal site, leading to K_ATP channel closure, and that the closure of Kv channels by propofol depolarization in β-cells enhances Ca²⁺ entry, leading to insulin secretion. Because its activity is dependent on GSIS, propofol and its derivatives are potential compounds that enhance and initiate β-cell electrical activity.

Bromocriptine use for sudden peripartum cardiomyopathy in a patient with preeclampsia: a case report

Background

Peripartum cardiomyopathy is an uncommon form of heart failure that occurs in otherwise healthy women during pregnancy or until 5 months postpartum. Here, we report a rare case where a female patient underwent cesarean section after the occurrence of preeclampsia and intrauterine fetal death, and developed peripartum cardiomyopathy following postsurgical respiratory distress. The prompt initiation of inotropic drug and bromocriptine therapy quickly restored cardiac function.

Case presentation

The patient was a 36-year-old woman who underwent emergency cesarean section for a previous preeclampsia and an intrauterine fetal death that occurred after 24 weeks of pregnancy. In addition, the patient had an extremely low platelet count of 5000/μL on admission. She had been diagnosed as idiopathic thrombocytopenic purpura at the age of 29 years old and treated with prednisolone at 15 mg/day. Therefore, the cesarean section was performed under general anesthesia. The patient did not exhibit respiratory or hemodynamic dysfunction during surgery. However, she developed respiratory distress with sinus tachycardia after extubation and was transferred to the intensive care unit. A chest radiograph showed butterfly shadows, and transthoracic echocardiogram confirmed the reduction of left ventricle contractility (ejection fraction 20%). She was diagnosed with peripartum cardiomyopathy and treated immediately with intravenous milrinone, oral bromocriptine, and angiotensin-converting enzyme inhibitor. Respiratory and hemodynamic function improved rapidly, and the patient was moved to the general ward 2 days after surgery. Fourteen days after surgery, the patient had an ejection fraction of 57%. The patient recovered without any further complications and was discharged 24 days after surgery.

Conclusion

A sudden case of peripartum cardiomyopathy was successfully managed by a prompt diagnosis and treatment with inotropic agents and bromocriptine.

Suppression of mitochondrial oxygen metabolism mediated by the transcription factor HIF-1 alleviates propofol-induced cell toxicity

A line of studies strongly suggest that the intravenous anesthetic, propofol, suppresses mitochondrial oxygen metabolism. It is also indicated that propofol induces the cell death in a reactive oxygen species (ROS)-dependent manner. Because hypoxia-inducible factor 1 (HIF-1) is a transcription factor which is involved in cellular metabolic reprogramming by modulating gene expressions of enzymes including glycolysis pathway and oxygen utilization of mitochondria, we examined the functional role of HIF-1 activity in propofol-induced cell death. The role of HIF-1 activity on oxygen and energy metabolisms and propofol-induced cell death and caspase activity was examined in renal cell-derived RCC4 cells: RCC4-EV cells which lack von Hippel-Lindau protein (VHL) protein expression and RCC4-VHL cells, which express exogenous VHL, and in neuronal SH-SY5Y cells. It was demonstrated that HIF-1 is involved in suppressing oxygen consumption and facilitating glycolysis in cells and that the resistance to propofol-induced cell death was established in a HIF-1 activation-dependent manner. It was also demonstrated that HIF-1 activation by treatment with HIFα-hydroxylase inhibitors such as n-propyl gallate and dimethyloxaloylglycine, alleviated the toxic effects of propofol. Thus, the resistance to propofol toxicity was conferred by HIF-1 activation by not only genetic deletion of VHL but also exposure to HIFα-hydroxylase inhibitors.

Propofol induces a metabolic switch to glycolysis and cell death in a mitochondrial electron transport chain-dependent manner

The intravenous anesthetic propofol (2,6-diisopropylphenol) has been used for the induction and maintenance of anesthesia and sedation in critical patient care. However, the rare but severe complication propofol infusion syndrome (PRIS) can occur, especially in patients receiving high doses of propofol for prolonged periods. In vivo and in vitro evidence suggests that the propofol toxicity is related to the impaired mitochondrial function. However, underlying molecular mechanisms remain unknown. Therefore, we investigated effects of propofol on cell metabolism and death using a series of established cell lines of various origins, including neurons, myocytes, and trans-mitochondrial cybrids, with defined mitochondrial DNA deficits. We demonstrated that supraclinical concentrations of propofol in not less than 50 μM disturbed the mitochondrial function and induced a metabolic switch, from oxidative phosphorylation to glycolysis, by targeting mitochondrial complexes I, II and III. This disturbance in mitochondrial electron transport caused the generation of reactive oxygen species, resulting in apoptosis. We also found that a predisposition to mitochondrial dysfunction, caused by a genetic mutation or pharmacological suppression of the electron transport chain by biguanides such as metformin and phenformin, promoted propofol-induced caspase activation and cell death induced by clinical relevant concentrations of propofol in not more than 25 μM. With further experiments with appropriate in vivo model, it is possible that the processes to constitute the molecular basis of PRIS are identified.

Impact of hydroxyethyl starch 70/0.5 on acute kidney injury after gastroenterological surgery

Background

Previous studies reported a higher mortality risk and a greater need for renal replacement therapy in patients administered hydroxyethyl starch (HES) rather than other fluid resuscitation preparations. In this study, we investigated the association between 6% HES 70/0.5 use and postoperative acute kidney injury (AKI) in gastroenterological surgery patients.

Methods

We conducted retrospective full-cohort and propensity-score-based analyses of patients who underwent gastroenterological surgery between June 2011 and August 2013 in a Japanese university hospital. The study sample comprised 66 AKI and 2,152 non-AKI patients in the full-cohort analysis and 35 AKI and 1,269 non-AKI patients in the propensity-score-based analysis. Propensity scores were calculated using an ordered logistic regression model in which the dependent variable comprised three groups based on HES infusion volumes (0, 1–999, and ≥ 1,000 ml). The association between HES groups and postoperative AKI incidence was analyzed using multiple logistic regression models. Other candidate independent variables included patient characteristics and intraoperative measures.

Results

In the full-cohort analysis, 40 (60.6%) AKI patients were diagnosed as "risk", 15 (22.7%) as "injury," and 11 (16.7%) as "failure". In the propensity-score-based analysis, the corresponding values were 22 (62.9%), 8 (22.9%), and 5 (14.3%). There was no significant association between total infused HES and postoperative AKI incidence in either the full-cohort or the propensity-score-based analysis (P = 0.168 and P = 0.42, respectively).

Conclusions

AKI incidence was not associated with clinical 6% HES 70/0.5 administration in gastroenterological surgery patients treated at a single center.

Rapid development of a spinal epidural hematoma following thoracic epidural catheter removal in an esophageal carcinoma surgical patient: a case report

Background

The occurrence of spinal epidural hematomas associated with the use of epidural catheters is relatively rare. Furthermore, it is unusual for hematoma-associated neurological symptoms to occur within 15 min of removing a catheter. Here, we report our experience with an esophageal carcinoma surgical patient who developed an epidural hematoma almost immediately after catheter removal, resulting in paralysis of his lower extremities. The patient achieved full neurological recovery following prompt diagnosis and surgical intervention.

Case presentation

A 68-year-old man was admitted with esophageal carcinoma and underwent video-assisted thoracoscopic esophagectomy followed by posterior mediastinal gastric tube reconstruction. During surgery, the patient was administered both general and epidural anesthesia. The epidural catheter was inserted approximately 5 cm into the epidural space at the Th6–7 level. The patient was extubated the following day in the general intensive care unit. Two days after surgery, the d-dimer level was high at 36.9 μg/mL (reference range 0–0.9 μg/mL), and we decided to administer an anticoagulant (enoxaparin sodium) to prevent thrombosis. The epidural catheter was removed 2 h prior to the scheduled administration of enoxaparin sodium. However, the patient reported a complete lack of strength in his lower extremities 15 min after catheter removal. Upon examination, the manual muscle testing score was 1 out of 5, and the patient experienced impaired touch sensation and cold sensation below Th4. An emergency magnetic resonance imaging scan was performed 2 h after catheter removal, which revealed a possible spinal epidural hematoma spreading from Th3 to Th6. Three hours after catheter removal, we began emergency surgery to evacuate the hematoma, which had spread to Th7. After surgery, the patient showed improvements in touch sensation, cold sensation, and motor function. The patient was able to walk 2 days after hematoma removal.

Conclusions

It is highly unusual for a spinal epidural hematoma to develop so rapidly after the removal of an epidural catheter. This case emphasizes the need for vigilant patient monitoring, rapid diagnosis, and prompt surgery to ensure adequate neurological recovery in these patients.

[Effect of isometric hand-grip exercise on left ventricular diastolic filling in patients with effort angina: a pulsed Doppler echocardiographic study]

To detect myocardial ischemia and to estimate cardiac reserve in patients with effort angina pectoris without history of myocardial infarction, left ventricular diastolic filling was measured using Doppler echocardiography during isometric handgrip exercise. Nineteen patients with effort angina pectoris undergoing coronary angiography and 16 normal subjects were studied. The angina patients were categorized in two groups: 12 with single vessel disease (SVD) and seven with multiple vessel disease (MVD). Fifty percent maximum voluntary contraction isometric handgrip exercise was performed for two minutes. 1. The resting A/R in the angina group was significantly greater than that of the normal subjects (SVD: 1.20 +/- 0.24, MVD: 1.21 +/- 0.27, normal 0.85 +/- 0.10) (p less than 0.001). However, the values of many cases in these three groups overlapped. 2. In SVD, the A/R increased significantly during isometric handgrip exercise (1.20 +/- 0.24 to 1.96 +/- 0.66: p less than 0.001). The delta A/R (0.76 +/- 0.15) was significantly greater than that of patients in other groups (MVD: 0.10 +/- 0.13, normal: 0.09 +/- 0.01) (p less than 0.001). Consequently, the A/R after exercise clearly distinguished the SVD from the normal subjects. 3. In MVD, the A/R did not change significantly during exercise (1.21 +/- 0.27 to 1.31 +/- 0.41), and there were no significant differences in delta A/R as compared to the normal subjects (p less than 0.01). The A/R decreased during exercise in three of the seven patients, and this was markedly different from that of the normal subjects. These findings suggest that assessment of changes in left ventricular diastolic filling during isometric handgrip exercise is useful in detecting myocardial ischemia and in estimating cardiac reserve in patients with effort angina pectoris.