Cardiopulmonary bypass management and neurologic outcomes: an evidence-based appraisal of current practices

Incidence and predictors of readmission to the cardiac surgery intensive care unit: A retrospective cohort study in Greece

INTRODUCTION:

Readmission in the intensive care unit (ICU) is a significant morbidity index, which has been related to poor patient outcomes

AIM:

To identify the preoperative and intraoperative risk factors for readmission in the cardiac surgery ICU.

METHODS:

We conducted a retrospective cohort study of 595 consecutive patients who were admitted to the cardiac surgery ICU of a tertiary hospital of Athens — Greece during the one-year period (September 2011-September 2012). Data collection was carried out, retrospectively, by the use of a short questionnaire and based on the review of medical and nursing patient records at December 2012.

RESULTS:

The incidence of ICU readmission was 3.7% (22/595). Respiratory disorders were the main reason for readmission (45.4%). Readmitted patients had a significantly higher in-hospital mortality compared to those requiring no readmission (P < 0.001). Multivariate analysis revealed that female gender [for males odds ratio (OR) 0.37, 95% confidence interval (CI) 0.15-0.89], high logistic EuroSCORE (OR 1.02, 95% CI 1.00-1.04), prolonged cardiopulmonary (CPB) duration (OR 1.01, 95% CI 1.00-1.02) and preoperative renal failure (OR 1.02, 95% CI 1.00-1.05) were the independent risk factors for readmission to the cardiac surgery ICU.

CONCLUSIONS:

One intraoperative and three preoperative variables are associated strongly with higher probability for ICU readmission. Shorter CPB duration could contribute to lower ICU readmission incidence. In addition, the early identification of high risk patients for readmission in the cardiac surgery ICU could encourage both the more efficient healthcare planning and resources allocation.

Effect of remote ischemic preconditioning on cognitive function after off-pump coronary artery bypass graft: a pilot study

Background

Several studies have shown in animal models that remote ischemic preconditioning (rIPC) has a neuroprotective effect. However, a randomized controlled trial in human subjects to investigate the neuroprotective effect of rIPC after cardiac surgery has not yet been reported. Therefore, we performed this pilot study to determine whether rIPC reduced the occurrence of postoperative cognitive dysfunction in patients who underwent off-pump coronary artery bypass graft (OPCAB) surgery.

Methods

Seventy patients who underwent OPCAB surgery were assigned to either the control or the rIPC group using a computer-generated randomization table. The application of rIPC consisted of four cycles of 5 min ischemia and 5 min reperfusion on an upper limb using a blood pressure cuff inflating 200 mmHg before coronary artery anastomosis. The cognitive function tests were performed one day before surgery and again on postoperative day 7. We defined postoperative cognitive dysfunction as decreased postoperative test values more than 20% of the baseline values in more than two of the six cognitive function tests that were performed.

Results

In the cognitive function tests, there were no significant differences in the results obtained during the preoperative and postoperative periods for all tests and there were no mean differences observed in the preoperative and postoperative scores. The incidences of postoperative cognitive dysfunction in the control and rIPC groups were 28.6% (10 patients) and 31.4% (11 patients), respectively.

Conclusions

rIPC did not reduce the incidence of postoperative cognitive dysfunction after OPCAB surgery during the immediate postoperative period.

Intraoperative magnesium administration does not improve neurocognitive function after cardiac surgery

BACKGROUND AND PURPOSE

Neurocognitive decline occurs frequently after cardiac surgery and persists in a significant number of patients. Magnesium is thought to provide neuroprotection by preservation of cellular energy metabolism, blockade of the N-methyl-D-aspartate receptor, diminution of the inflammatory response, and inhibition of platelet activation. We therefore hypothesized that intraoperative magnesium administration would decrease postoperative cognitive impairment.

METHODS

After approval by the Duke University Health System Institutional Review Board, 389 patients undergoing cardiac surgery were enrolled in this prospective, randomized, double-blind, placebo-controlled clinical trial. Subjects were randomized to receive magnesium as a 50 mg/kg bolus followed by another 50 mg/kg infusion for 3 hours or placebo bolus and infusion. Cognitive function was assessed preoperatively and again at 6 weeks postoperatively using a standardized test battery. Mean CD11b fluorescence and percentage of platelets expressing CD62P, which are markers of leukocyte and platelet activation, respectively, were assessed by flow cytometry as a secondary outcome. The effect of magnesium on postoperative cognition was tested using multivariable regression modeling, adjusting for age, years of education, baseline cognition, sex, race, and weight.

RESULTS

Among the 389 allocated subjects (magnesium: n=198; placebo: n=191), the incidence of cognitive deficit in the magnesium group was 44.4% compared with 44.9% in the placebo group (P=0.93). The cognitive change score and platelet and leukocyte activation were also not different between the groups. Multivariable analysis revealed a marginal interaction between treatment group and weight such that heavier subjects receiving magnesium were less likely to have cognitive deficit (P=0.06).

CONCLUSIONS

Magnesium administered intravenously during cardiac surgery does not reduce postoperative cognitive dysfunction.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT00041392.

Duration and magnitude of blood pressure below cerebral autoregulation threshold during cardiopulmonary bypass is associated with major morbidity and operative mortality

OBJECTIVES

Optimizing blood pressure using near-infrared spectroscopy monitoring has been suggested to ensure organ perfusion during cardiac surgery. Near-infrared spectroscopy is a reliable surrogate for cerebral blood flow in clinical cerebral autoregulation monitoring and might provide an earlier warning of malperfusion than indicators of cerebral ischemia. We hypothesized that blood pressure below the limits of cerebral autoregulation during cardiopulmonary bypass would be associated with major morbidity and operative mortality after cardiac surgery.

METHODS

Autoregulation was monitored during cardiopulmonary bypass in 450 patients undergoing coronary artery bypass grafting and/or valve surgery. A continuous, moving Pearson's correlation coefficient was calculated between the arterial pressure and low-frequency near-infrared spectroscopy signals and displayed continuously during surgery using a laptop computer. The area under the curve of the product of the duration and magnitude of blood pressure below the limits of autoregulation was compared between patients with and without major morbidity (eg, stroke, renal failure, mechanical lung ventilation >48 hours, inotrope use >24 hours, or intra-aortic balloon pump insertion) or operative mortality.

RESULTS

Of the 450 patients, 83 experienced major morbidity or operative mortality. The area under the curve of the product of the duration and magnitude of blood pressure below the limits of autoregulation was independently associated with major morbidity or operative mortality after cardiac surgery (odds ratio, 1.36; 95% confidence interval, 1.08-1.71; P = .008).

CONCLUSIONS

Blood pressure management during cardiopulmonary bypass using physiologic endpoints such as cerebral autoregulation monitoring might provide a method of optimizing organ perfusion and improving patient outcomes from cardiac surgery.

Cerebral blood flow autoregulation is preserved after continuous-flow left ventricular assist device implantation

OBJECTIVE

To compare cerebral blood flow (CBF) autoregulation in patients undergoing continuous-flow left ventricular assist device (LVAD) implantation with that in patients undergoing coronary artery bypass grafting (CABG).

DESIGN

Prospective, observational, controlled study.

SETTING

Academic medical center.

PARTICIPANTS

Fifteen patients undergoing LVAD insertion and 10 patients undergoing CABG.

MEASUREMENTS AND MAIN RESULTS

Cerebral autoregulation was monitored with transcranial Doppler and near-infrared spectroscopy. A continuous Pearson correlation coefficient was calculated between mean arterial pressure (MAP) and CBF velocity and between MAP and near-infrared spectroscopic data, rendering the variables mean velocity index (Mx) and cerebral oximetry index (COx), respectively. Mx and COx approach 0 when autoregulation is intact (no correlation between CBF and MAP), but approach 1 when autoregulation is impaired. Mx was lower during and immediately after cardiopulmonary bypass in the LVAD group than in the CABG group, indicating better-preserved autoregulation. Based on COx monitoring, autoregulation tended to be better preserved in the LVAD group than in the CABG group immediately after surgery (p = 0.0906). On postoperative day 1, COx was lower in the LVAD group than in the CABG group, indicating preserved CBF autoregulation (p = 0.0410). Based on COx monitoring, 3 patients (30%) in the CABG group had abnormal autoregulation (COx ≥0.3) on the first postoperative day but no patient in the LVAD group had this abnormality (p = 0.037).

CONCLUSIONS

These data suggest that CBF autoregulation is preserved during and immediately after surgery in patients undergoing LVAD insertion.

Arterial hyperoxia during cardiopulmonary bypass and postoperative cognitive dysfunction

OBJECTIVE

To determine the effect of arterial normobaric hyperoxia during cardiopulmonary bypass (CPB) on postoperative neurocognitive function. The authors hypothesized that arterial hyperoxia during CPB is associated with neurocognitive decline at 6 weeks after cardiac surgery.

DESIGN

Retrospective study of patients undergoing cardiac surgery with CPB.

SETTING

A university hospital.

PARTICIPANTS

One thousand eighteen patients undergoing coronary artery bypass graft (CABG) or CABG + valve surgery with CPB who previously had been enrolled in prospective cognitive trials.

INTERVENTIONS

A battery of neurocognitive measures was administered at baseline and 6 weeks after surgery. Anesthetic and surgical care was managed as clinically indicated.

MEASUREMENTS AND MAIN RESULTS

Arterial hyperoxia was assessed primarily as the area under the curve (AUC) for the duration that PaO2 exceeded 200 mmHg during CPB and secondarily as the mean PaO2 during bypass, as a PaO2 = 300 mmHg at any point and as AUC>150 mmHg. Cognitive change was assessed both as a continuous change score and a dichotomous deficit rate. Multivariate regression accounting for age, years of education, baseline cognition, date of surgery, baseline postintubation PaO2, duration of CPB, and percent change in hematocrit level from baseline to lowest level during CPB revealed no significant association between hyperoxia during CPB and postoperative neurocognitive function.

CONCLUSIONS

Arterial hyperoxia during CPB was not associated with neurocognitive decline after 6 weeks in cardiac surgical patients.

Reliability of different body temperature measurement sites during aortic surgery

OBJECTIVE

We retrospectively performed a comparative analysis of temperature measurement sites during surgical repair of the thoracic aorta.

METHODS

Between January 2004 and May 2006, 22 patients (mean age: 63 ± 12 years) underwent operations on the thoracic aorta with arterial cannulation of the aortic arch concavity and selective antegrade cerebral perfusion (ACP) during deep hypothermic circulatory arrest (HCA). Indications for surgical intervention were acute type A dissection in 14 (64%) patients, degenerative aneurysm in 6 (27%), aortic infiltration of thymic carcinoma in 1 (4.5%) and intra-aortic stent refixation in 1 (4.5%). Rectal, tympanic and bladder temperatures were evaluated to identify the best reference to arterial blood temperature during HCA and ACP.

RESULTS

There were no operative deaths and the 30-day mortality rate was 13% (three patients). Permanent neurological deficits were not observed and transient changes occurred in two patients (9%). During re-warming, there was strong correlation between tympanic and arterial blood temperatures (r = 0.9541, p<0.001), in contrast to the rectal and bladder temperature (r = 0.7654, p = n.s; r = 0.7939, p = n.s., respectively).

CONCLUSION

We conclude that tympanic temperature measurements correlate with arterial blood temperature monitoring during aortic surgery with HCA and ACP and, therefore, should replace bladder and rectal measurements.

Novel emboli protection cannula during cardiac surgery: first animal study

Background

Stroke after open heart surgery is a major cause of morbidity and mortality. Up to 60% of intraoperative cerebral events are caused by emboli generated by manipulations of the aorta during surgery. This is the first animal study evaluating the safety and efficacy of a novel aortic cannula designed to extract solid and gaseous emboli during cardiac surgery.

Methods

Seven domestic pigs were connected to cardiopulmonary bypass using a CardioGard 24F aortic cannula. Three pigs that were cannulated with a standard aortic cannula were defined as controls. Several main flow and suction regimens were carried out. Osseous particles of different sizes were injected into the proximal aorta to simulate emboli.

Results

The CardioGard cannula demonstrated an overall emboli retrieval rate of 77%. A rate of 88.45% was demonstrated during the low-flow regimen used clinically during aortic manipulation. Gaseous and solid emboli were eliminated by suction, as demonstrated by epi-carotid ultrasound. No significant changes were observed in hemodynamic and laboratory parameters.

Conclusions

The CardioGard cannula is as simple to use as a regular commercially available aortic cannula, having a similar safety profile and proven efficacy in capturing intraoperative emboli.

Technological solutions for cardiac surgery in the elderly

The current review addresses contemporary technological advances in cardiac surgery performed on octogenarian patients, namely off-pump coronary artery bypass grafting (CABG), proximal anastomosis device, routine use of intraoperative epiaortic ultrasound, proximal anastomosis without clamping, transcatheter aortic valve implantation (TAVI), and brain protection during cardiac surgery.

Brain emboli distribution and differentiation during cardiopulmonary bypass

OBJECTIVE

Cardiopulmonary bypass (CPB) is a lifesaving practice in cardiac surgery, but its use frequently is associated with cerebral injury and neurocognitive dysfunctions. Despite the involvement of numerous factors, microembolism occurring during CPB seems to be one of the main mechanisms leading to such alterations. The aim of the present study was to characterize the occurrence of cerebral microembolism with reference to microembolic amount, nature, and distribution in different combinations of cardiac procedures and CPB on the microembolic load.

DESIGN

A retrospective observational clinical study.

SETTING

A single-center regional hospital.

PARTICIPANTS

Fifty-five patients undergoing elective cardiac surgery with CPB.

INTERVENTIONS

Bilateral detection of the patients' middle cerebral arteries using a multifrequency transcranial Doppler.

MEASUREMENTS AND MAIN RESULTS

Patients were divided into 3 groups depending on the CPB circuit used (open, open with vacuum, or closed). There was a significant difference between the number of solid and gaseous microemboli (p<0.001), with the solid lower than the gaseous ones. The number of solid microemboli was affected by group (p< 0.05), CPB phase (p<0.001), and laterality (p<0.01). The number of gaseous microemboli was affected only by group (p<0.05) and CPB phase (p<0.001). Generally, the length of CPB phase did not affect the number of microemboli.

CONCLUSIONS

Surgical procedures combined with CPB circuits, but not the CPB phase length, affected the occurrence, nature, and laterality of microemboli.

Blood pressure excursions below the cerebral autoregulation threshold during cardiac surgery are associated with acute kidney injury

OBJECTIVES

To determine whether mean arterial blood pressure excursions below the lower limit of cerebral blood flow autoregulation during cardiopulmonary bypass are associated with acute kidney injury after surgery.

SETTING

Tertiary care medical center.

PATIENTS

Four hundred ten patients undergoing cardiac surgery with cardiopulmonary bypass.

DESIGN

Prospective observational study.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Autoregulation was monitored during cardiopulmonary bypass by calculating a continuous, moving Pearson's correlation coefficient between mean arterial blood pressure and processed near-infrared spectroscopy signals to generate the variable cerebral oximetry index. When mean arterial blood pressure is below the lower limit of autoregulation, cerebral oximetry index approaches 1, because cerebral blood flow is pressure passive. An identifiable lower limit of autoregulation was ascertained in 348 patients. Based on the RIFLE criteria (Risk, Injury, Failure, Loss of kidney function, End-stage renal disease), acute kidney injury developed within 7 days of surgery in 121 (34.8%) of these patients. Although the average mean arterial blood pressure during cardiopulmonary bypass did not differ, the mean arterial blood pressure at the limit of autoregulation and the duration and degree to which mean arterial blood pressure was below the autoregulation threshold (mm Hg × min/hr of cardiopulmonary bypass) were both higher in patients with acute kidney injury than in those without acute kidney injury. Excursions of mean arterial blood pressure below the lower limit of autoregulation (relative risk 1.02; 95% confidence interval 1.01 to 1.03; p < 0.0001) and diabetes (relative risk 1.78; 95% confidence interval 1.27 to 2.50; p = 0.001) were independently associated with for acute kidney injury.

CONCLUSIONS

Excursions of mean arterial blood pressure below the limit of autoregulation and not absolute mean arterial blood pressure are independently associated with for acute kidney injury. Monitoring cerebral oximetry index may provide a novel method for precisely guiding mean arterial blood pressure targets during cardiopulmonary bypass.

Predictors of cognitive recovery after cardiac surgery

BACKGROUND

Postoperative neurocognitive decline occurs frequently. Although predictors of cognitive injury have been well examined, factors that modulate recovery have not. We sought to determine the predictors of cognitive recovery after initial injury following cardiac surgery.

METHODS

Two hundred eighty-one patients previously enrolled in cognitive studies who experienced cognitive decline 6 weeks after cardiac surgery were retrospectively evaluated. Eligible patients completed a battery of neurocognitive measures and quality-of-life assessments at baseline, 6 weeks, and 1 year after surgery. Factor analysis was conducted to calculate the cognitive index (CI), a unified, continuous measure of cognitive function. Cognitive recovery was defined as 1-year CI greater than baseline CI. Potential predictors of cognitive recovery including patient characteristics, quality-of-life factors, comorbidities, medications, and intraoperative variables were assessed with multivariable regression modeling; P<0.05 was considered significant.

RESULTS

Of the 229 patients in our final data set, 103 (45%) demonstrated cognitive recovery after initial decline in CI at 6 weeks. Multivariable analyses revealed that more education (odds ratio [OR] 1.332 [1.131-1.569], P<0.001), baseline CI (OR 0.987 [0.976-0.998], P=0.02), less decline in CI at 6 weeks (OR 1.044 [1.014-1.075], P=0.004), and greater activities of daily living at 6 weeks (OR 0.891 [0.810-0.981], P=0.02) were significant predictors of cognitive recovery.

CONCLUSION

Cognitive recovery occurred in approximately one half of the cardiac surgical patients experiencing early decline. The association between cognitive recovery and Instrumental Activities of Daily Living scores at 6 weeks merits further investigation as it is the only potentially modifiable predictor of recovery.

Attrition in longitudinal randomized controlled trials: home visits make a difference

Background

Participant attrition in longitudinal studies can introduce systematic bias, favoring participants who return for follow-up, and increase the likelihood that those with complications will be underestimated. Our aim was to examine the effectiveness of home follow-up (Home F/U) to complete the final study evaluation on potentially “lost” participants by: 1) evaluating the impact of including and excluding potentially “lost” participants (e.g., those who required Home F/U to complete the final evaluation) on the rates of study complications; 2) examining the relationship between timing and number of complications on the requirement for subsequent Home F/U; and 3) determining predictors of those who required Home F/U.

Methods

We used data from a randomized controlled trial (RCT) conducted from 1991–1994 among coronary artery bypass graft surgery patients that investigated the effect of High mean arterial pressure (MAP) (intervention) vs. Low MAP (control) during cardiopulmonary bypass on 5 complications: cardiac morbidity/mortality, neurologic morbidity/mortality, all-cause mortality, neurocognitive dysfunction and functional decline. We enhanced completion of the final 6-month evaluation using Home F/U.

Results

Among 248 participants, 61 (25%) required Home F/U and the remaining 187 (75%) received Routine F/U. By employing Home F/U, we detected 11 additional complications at 6 months: 1 major neurologic complication, 6 cases of neurocognitive dysfunction and 4 cases of functional decline. Follow-up of 61 additional Home F/U participants enabled us to reach statistical significance on our main trial outcome. Specifically, the High MAP group had a significantly lower rate of the Combined Trial Outcome compared to the Low MAP group, 16.1% vs. 27.4% (p=0.032). In multivariate analysis, participants who were ≥ 75 years (OR=3.23, 95% CI 1.52-6.88, p=0.002) or on baseline diuretic therapy (OR=2.44, 95% CI 1.14-5.21, p=0.02) were more likely to require Home F/U. In addition, those in the Home F/U group were more likely to have sustained 2 or more complications (p=0.05).

Conclusions

Home visits are an effective approach to reduce attrition and improve accuracy of study outcome reporting. Trial results may be influenced by this method of reducing attrition. Older participants, those with greater medical burden and those who sustain multiple complications are at higher risk for attrition.

Risks for impaired cerebral autoregulation during cardiopulmonary bypass and postoperative stroke

BACKGROUND

Impaired cerebral autoregulation may predispose patients to cerebral hypoperfusion during cardiopulmonary bypass (CPB). The purpose of this study was to identify risk factors for impaired autoregulation during coronary artery bypass graft, valve surgery with CPB, or both and to evaluate whether near-infrared spectroscopy (NIRS) autoregulation monitoring could be used to identify this condition.

METHODS

Two hundred and thirty-four patients were monitored with transcranial Doppler and NIRS. A continuous, moving Pearson's correlation coefficient was calculated between mean arterial pressure (MAP) and cerebral blood flow (CBF) velocity, and between MAP and NIRS data, to generate the mean velocity index (Mx) and cerebral oximetry index (COx), respectively. Functional autoregulation is indicated by an Mx and COx that approach zero (no correlation between CBF and MAP); impaired autoregulation is indicated by an Mx and COx approaching 1. Impaired autoregulation was defined as an Mx ≥0.40 at all MAPs during CPB.

RESULTS

Twenty per cent of patients demonstrated impaired autoregulation during CPB. Based on multivariate logistic regression analysis, time-averaged COx during CPB, male gender, Pa(CO(2)), CBF velocity, and preoperative aspirin use were independently associated with impaired CBF autoregulation. Perioperative stroke occurred in six of 47 (12.8%) patients with impaired autoregulation compared with five of 187 (2.7%) patients with preserved autoregulation (P=0.011).

CONCLUSIONS

Impaired CBF autoregulation occurs in 20% of patients during CPB. Patients with impaired autoregulation are more likely than those with functional autoregulation to have perioperative stroke. Non-invasive monitoring autoregulation may provide an accurate means to predict impaired autoregulation. Clinical trials registration. www.clinicaltrials.gov (NCT00769691).

Cognitive deficit in first-time coronary artery bypass graft patients: a randomized clinical trial of lidocaine versus procaine hydrochloride

Introduction:

Cognitive dysfunction increasingly has been recognized as a complication after cardiac surgery. Different methods have been considered for the reduction of cognitive dysfunction after cardiac surgery. One of these methods is by using lidocaine during surgery. The aim of this study was to determine the effects of adding lidocaine to the cardioplegia solution on cognitive impairment after coronary artery surgery.

Design and methods:

In a prospective, randomized, double-blind trial, 110 patients aged between 20-70 years, scheduled for elective CABG surgery using cardiopulmonary bypass, were recruited into the study. They were randomized into two groups who received either cardioplegia solution containing lidocaine 2 mg/kg or procaine hydrochloride 5 mg/kg. The neurocognitive test used in this study was the Mini Mental State Examination (MMSE) or Folstein test. The test was done on the day before and 10 days and 2 months after the operation.

Results:

In the procaine group, the total score after 10 days decreased significantly compared to the preoperative score (mean difference 0.68; 95% CI: 0.20 to 1.17, p=0.006). Comparison between mean differences after 10 and 60 days of operation between the lidocaine and procaine groups were statistically significant, p-value 0.017 and 0.013, respectively. There was no cognitive impairment in the lidocaine group, but, in the procaine group, four patients (7.7%) after 10 days and one patient (1.9%) after both 10 and 60 days had cognitive impairment, p=0.051.

Conclusions:

Administration of lidocaine compared to that of procaine through the cardioplegia solution had a better effect on cognitive function after coronary artery bypass graft surgery.

Remote ischemic preconditioning protects neurocognitive function of rats following cerebral hypoperfusion

BACKGROUND

Protection of remote ischemic preconditioning on neurocognitive function caused by bilateral common carotid artery occlusion has been investigated in rats.

MATERIAL/METHODS

Thirty-six male Sprague-Dawley rats were divided into 3 groups - control group (Group C, n=12), bilateral carotid arteries occlusion group (Group B, n=12) and remote ischemic precondition group (Group P, n=12). In Group P, remote ischemic preconditioning (RIPC) was performed on the right femoral artery with 3 cycles (10 min) of occlusion/perfusion. After 3 cycles of preconditioning, bilateral carotid arteries were occluded immediately for 60 min. In Group B, ischemic insults were conducted without RIPC. Sham surgeries were performed in Group C. Evaluation of memory and learning capacity was performed on days 5-8 after surgery by Morris water maze testing of spatial learning capacity (n=6 for each group). Apoptosis of cells in the hippocampus region was determined by TUNEL tests and Bcl-2 at this region was determined by ELISA 24 h and 9 days after vessel occlusion (n=6 for each group).

RESULTS

Neurocognitive tests showed that latency time was significantly longer in Group B than in Group P on day 7 (p=0.016) and day 8 (p=0.036). Moreover, frequency of platform crossings was significant less in group B than in the other 2 groups on day 9. Bcl-2 level was significantly increased in the hippocampal region of rats in Group P on days 1 and 9 after vessel occlusion. TUNEL test showed that apoptosis could be observed at 24 h after occlusion in Group B, but not in Group P and Group C. No apoptosis was observed on day 9.

CONCLUSIONS

Our results suggest that RIPC can protect neurocognitive function of rats after bilateral carotid occlusions, and that Bcl-2 may play an important role in this protective effect.

Initial description of cerebral oximetry measurement in heart failure patients

Cerebral oximetry is a noninvasive technology using near-infrared spectroscopy (NIRS) to monitor regional cerebral tissue oxygen saturation (SctO(2)). NIRS has been widely used for assessing cerebral tissue oxygenation in a variety of populations including the fields of neonatology, anesthesiology, neurology, and cardiac surgery.However, little information has been reported on cerebral oximetry in heart failure (HF) patients. In this observational study, we enrolled 30 patients (15 men) aged 23 to 82 years (mean 67 years) with stage C HF. All patients had New York Heart Association (NYHA) functional class I to III. All patients were on stable HF medical therapy. SctO(2) measurements were recorded from the left and right forehead simultaneously, using FORE-SIGHT cerebral oximeter (CAS Medical Systems Inc, Branford, CT). Feasible associations with SctO(2) risk factors, known to correlate with HF, were recorded. The mean SctO(2) value was 67.4% (range, 47.6%-76.3%), while the mean peripheral tissue saturation (SpO(2)) was 97% (range, 92%-100%). The mean difference between cerebral and peripheral tissue oxygenation (SpO(2)-SctO(2)) was 29.2% (range, 19.2%-51.4%). There was also a significant positive correlation between SctO(2) and mean arterial blood pressure (0.55, P<.01). Statistically significant lower SctO(2) values were observed in patients with diabetes (P=.026; confidence interval [CI], 0.006-0.090) and in patients with dyslipidemia (P=.007; CI, 0.018-0.103). In this initial description of SctO(2) in patients with stage C HF, we noted a wide range of SctO(2) measurements. For most patients, there was a profound SpO(2)-SctO(2) difference, despite near-normal peripheral oxygen saturations. The authors suggest that SctO(2) is a potentially important biomarker to measure in HF patients and may be a useful marker of target organ perfusion.

Brain damage in cardiac surgery patients

Neuropsychological disorders and brain injury are still a serious problem in cardiac surgery patients. Owing to multifactorial mechanism of brain injury during extracorporeal circulation, the effective and safe protection is extremely difficult. Despite several studies, the ideal neuroprotective treatment has not been found. Based on literature we analysed the main mechanisms of brain injury and new methods of brain protection.

[Acute neurological complications after pediatric cardiac surgery: still a long way to go]

INTRODUCTION

There has been an increasing concern over the neurological complications associated with congenital heart disease and cardiac surgery.

MATERIAL AND METHODS

We performed a retrospective, case-control, observational review of the postoperative period in the intensive care unit of patients undergoing cardiac surgery over the past 10 years. We selected 2 control patients for each case, matched for surgical complexity.

RESULTS

A total of 900 patients were reviewed. We found 38 neurological complications (4.2%), of which 21 (55.3%) were in the peripheral nervous system and 17 (44.7%) in the central nervous system. The complications involving the central nervous system (1.9% of total) consisted of 8 seizures, 4 cerebrovascular accidents, 4 hypoxic-ischemic encephalopathy events, and 1 reversible neurological deficit. At the time of discharge, 35.3% were symptomatic and 17.6% had died. Patients with neurological complications had a longer bypass time (P=.009), longer aortic cross time (P=.012), longer hospitalization in intensive care (P=.001), longer duration of mechanical ventilation (P=.004) and an increased number of days under inotropic support (P=.001).

CONCLUSIONS

Our incidence of neurological complications after cardiac surgery is similar to that previously described. Clinical seizures are the most common complication. Central nervous system complications are associated with a higher morbidity and hospitalization time. Units caring for patients with congenital heart disease must implement neurological monitoring during and after cardiac surgery to prevent and to detect these complications earlier.

Perfusion safety: new initiatives and enduring principles

Perfusion safety has been studied and discussed extensively for decades. Many initiatives occurred through efforts of professional organizations to achieve recognition, establish accreditation and certification, promote consensus practice guidelines, and develop peer-reviewed journals as sources for dissemination of clinical information. Newer initiatives have their basis in other disciplines and include systems approach, Quality Assurance/Quality Improvement processes, error recognition, evidence-based methodologies, registries, equipment automation, simulation, and the Internet. Use of previously established resources such as written protocols, checklists, safety devices, and enhanced communication skills has persisted to the present in promoting perfusion safety and has reduced current complication rates to negligible levels.

Therapeutic hypothermia: benefits, mechanisms and potential clinical applications in neurological, cardiac and kidney injury

Therapeutic hypothermia involves the controlled reduction of core temperature to attenuate the secondary organ damage which occurs following a primary injury. Clinicians have been increasingly using therapeutic hypothermia to prevent or ameliorate various types of neurological injury and more recently for some forms of cardiac injury. In addition, some recent evidence suggests that therapeutic hypothermia may also provide benefit following acute kidney injury. In this review we will examine the potential mechanisms of action and current clinical evidence surrounding the use of therapeutic hypothermia. We will discuss the ideal methodological attributes of future studies using hypothermia to optimise outcomes following organ injury, in particular neurological injury. We will assess the importance of target hypothermic temperature, time to achieve target temperature, duration of cooling, and re-warming rate on outcomes following neurological injury to gain insights into important factors which may also influence the success of hypothermia in other organ injuries, such as the heart and the kidney. Finally, we will examine the potential of therapeutic hypothermia as a future kidney protective therapy.

Intravenous antiarrhythmic doses of lidocaine increase the survival rate of CA1 neurons and improve cognitive outcome after transient global cerebral ischemia in rats

Brain ischemia is often a consequence of cardiac or neurologic surgery. Prophylactic pharmacological neuroprotection would be beneficial for patients undergoing surgery to reduce brain damage due to ischemia. We examined the effects of two antiarrhythmic doses of lidocaine (2 or 4 mg/kg) on rats in a model of transient global cerebral ischemia. The occlusion of both common carotid arteries combined with hypotension for 10 min induced neuronal loss in the CA1 region of the hippocampus (18±12 vs. 31±4 neurons/200 μm linear distance of the cell body layer, X±SD; P<0.01). Lidocaine (4 mg/kg) 30 min before, during and 60 min after ischemia increased dorsal hippocampal CA1 neuronal survival 4 weeks after global cerebral ischemia (30±9 vs. 18±12 neurons/200 μm; P<0.01). There was no significant cell loss after 10 min of ischemia in the CA3 region, the dentate region or the amygdalae; these regions were less sensitive than the CA1 region to ischemic damage. Lidocaine not only increased hippocampal CA1 neuronal survival, but also preserved cognitive function associated with the CA1 region. Using an active place avoidance task, there were fewer entrances into an avoidance zone, defined by relevant distal room-bound cues, in the lidocaine groups. The untreated ischemic group had an average, over the nine sessions, of 21±12 (X±SD) entrances into the avoidance zone per session; the 4 mg/kg lidocaine group had 7±8 entrances (P<0.05 vs. untreated ischemic) and the non-ischemic control group 7±5 entrances (P<0.01 vs. untreated ischemic). Thus, a clinical antiarrhythmic dose of lidocaine increased the number of surviving CA1 pyramidal neurons and preserved cognitive function; this indicates that lidocaine is a good candidate for clinical brain protection.

Near Infrared Spectroscopy during pediatric cardiac surgery: errors and pitfalls

As a result of improvements in early outcomes, long-term neurologicalal outcomes are becoming a major issue in pediatric cardiac surgery. The mechanisms of brain injury are numerous, but a vast majority of injuries are impervious to therapy and only a few are modifiable. The quality of perfusion during cardiac surgery is a modifiable factor and cerebral monitoring during bypass is the way to assess the quality of intra-operative cerebral perfusion. Near infrared spectroscopy (NIRS), as a diagnostic tool, has gained in popularity within the perfusion community. However, NIRS is becoming the standard of care before its scientific validation. This manuscript relates four clinical cases, demonstrating the limitations of NIRS monitoring during pediatric cardiac surgery as well as uncertainties about the interpretation of the recorded values.

The clinical relevance of cerebral oxymetry is needed before the use of NIRS as a decision making tool. Multimodal brain monitoring with NIRS, trans-cranial Doppler and electroencephalogram are currently under way in several pediatric centers. The benefit of this time-consuming and expensive monitoring system has yet to be demonstrated.

The effect of blood pressure on cerebral outcome in a rat model of cerebral air embolism during cardiopulmonary bypass

OBJECTIVE

Higher mean arterial pressure during cardiopulmonary bypass may improve cerebral outcome associated with cerebral air embolism by increasing emboli clearance and collateral flow to salvage the ischemic penumbra. However, this may come at the expense of increased delivery of embolic load. This study was designed to investigate the influence of mean arterial pressures on cerebral functional and histologic outcome after cerebral air embolism during cardiopulmonary bypass in an established rat model.

METHODS

Male Sprague-Dawley rats were exposed to 90 minutes of normothermic cardiopulmonary bypass with 10 cerebral air embolisms (0.3 μL/bolus) injected repetitively. Rats were randomized to 3 groups (n = 10, each) that differed in mean arterial pressure management during cardiopulmonary bypass: 50 mm Hg (low mean arterial pressure), 60 to 70 mm Hg (standard mean arterial pressure), and 80 mm Hg (high mean arterial pressure). Neurologic score was assessed on postoperative days 3 and 7 when cerebral infarct volumes were determined. Cognitive function was determined with the Morris water maze test beginning on postoperative day 3 and continuing to postoperative day 7.

RESULTS

Neurologic score was better in high and standard mean arterial pressure groups versus low mean arterial pressure groups. High mean arterial pressure resulted in shorter water maze latencies compared with standard and low mean arterial pressure on postoperative days 6 and 7. Total infarct volume and number of infarct areas were not different among groups.

CONCLUSIONS

The use of higher mean arterial pressure during cardiopulmonary bypass in a rat model of cerebral air embolism conveyed beneficial effects on functional cerebral outcome with no apparent disadvantage of increased delivery of embolic load. Maintaining higher perfusion pressures in situations of increased cerebral embolic load may be considered as a collateral therapeutic strategy.

The effect of tight glycaemic control, during and after cardiac surgery, on patient mortality and morbidity: A systematic review and meta-analysis

BACKGROUND

Hyperglycaemia is a common occurrence during cardiac surgery, however, there remains some uncertainty surrounding the role of tight glycaemic control (blood glucose <180 mg/dL) during and/or after surgery. The aim of this study was to systematically review the literature to determine the effects of tight versus normal glycaemic control, during and after cardiac surgery, on measures of morbidity and mortality.

METHOD

The literature was systematically reviewed, based on pre-determined search criteria, for clinical trials evaluating the effect of tight versus normal glycaemic control during and/or after cardiac surgery. Each paper was reviewed by two, independent reviewers and data extracted for statistical analysis. Data from identified studies was combined using meta-analysis (RevMan5®). The results are presented either as odds ratios (OR) or mean differences (MD) with 95% confidence intervals (CIs).

RESULTS

A total of seven randomised controlled trials (RCTs) were identified in the literature, although not all trials could be used in each analysis. Tight glycaemic control reduced the incidence of early mortality (death in ICU) (OR 0.52 [95% CI 0.30, 0.91]); of post-surgical atrial fibrillation (odds ratio (OR 0.76 [95%CI 0.58, 0.99]); the use of epicardial pacing (OR 0.28 [95%CI 0.15, 0.54]); the duration of mechanical ventilation (mean difference (MD) -3.69 [95% CI -3.85, -3.54]) and length of stay in the intensive care unit (ICU) (MD -0.57 [95%CI -0.60, -0.55]) days. Measures of the time spent on mechanical ventilation (I2 94%) and time spent in ICU (I2 99%) both had high degrees of heterogeneity in the data.

CONCLUSION

The results from this study suggest that there may be some benefit to tight glycaemic control during and after cardiac surgery. However, due to the limited number of studies available and the significant variability in glucose levels; period of control; and the reporting of outcome measures, further research needs to be done to provide a definitive answer on the benefits of tight glycaemic control for cardiac surgery patients.

[Type A dissection. Principles of anesthesiological management]

Acute type A dissection is among the most dangerous of vascular diseases and is associated with a high lethality. Surgery for type A dissection is a complex procedure which is accompanied by relevant blood losses and severe deterioration of the coagulation system. Either due to the dissection or the surgical procedure, perfusion of affected organs can be diminished or completely disrupted with the risk of irreversible organ damage especially in the brain. Perioperative anesthesiological management for type A dissection is demanding and involves maintaining hemodynamic stability, surveillance of cerebral oxygenation and transesophageal echocardiographical diagnostic support for the decision-making of the most appropriate surgical approach. Furthermore, reestablishment of sufficient hemostasis can be challenging and requires thorough understanding of the relevant aspects affecting normal hemostasis during surgical repair of aortic dissection. In this article relevant pathophysiological aspects and basic principles of anesthesiological management of type A dissection are described.

Real-time continuous monitoring of cerebral blood flow autoregulation using near-infrared spectroscopy in patients undergoing cardiopulmonary bypass

BACKGROUND AND PURPOSE

Individualizing mean arterial blood pressure targets to a patient's cerebral blood flow autoregulatory range might prevent brain ischemia for patients undergoing cardiopulmonary bypass (CPB). This study compares the accuracy of real-time cerebral blood flow autoregulation monitoring using near-infrared spectroscopy with that of transcranial Doppler.

METHODS

Sixty adult patients undergoing CPB had transcranial Doppler monitoring of middle cerebral artery blood flow velocity and near-infrared spectroscopy monitoring. The mean velocity index (Mx) was calculated as a moving, linear correlation coefficient between slow waves of middle cerebral artery blood flow velocity and mean arterial blood pressure. The cerebral oximetry index was calculated as a similar coefficient between slow waves of cerebral oximetry and mean arterial blood pressure. When cerebral blood flow is autoregulated, Mx and cerebral oximetry index vary around zero. Loss of autoregulation results in progressively more positive Mx and cerebral oximetry index.

RESULTS

Mx and cerebral oximetry index showed significant correlation (r=0.55, P<0.0001) and good agreement (bias, 0.08+/-0.18, 95% limits of agreement: -0.27 to 0.43) during CPB. Autoregulation was disturbed in this cohort during CPB (average Mx 0.38, 95% CI 0.34 to 0.43). The lower cerebral blood flow autoregulatory threshold (defined as incremental increase in Mx >0.45) during CPB ranged from 45 to 80 mm Hg.

CONCLUSIONS

Cerebral blood flow autoregulation can be monitored continuously with near-infrared spectroscopy in adult patients undergoing CPB. Real-time autoregulation monitoring may have a role in preventing injurious hypotension during CPB. Clinical Trials Registration- at www.clinicaltrials.gov (NCT00769691).

Hawley H. Seiler Resident Award. Transcriptional profile of brain injury in hypothermic circulatory arrest and cardiopulmonary bypass

BACKGROUND

Little is known about the molecular mechanisms of neurologic complications after hypothermic circulatory arrest (HCA) with cardiopulmonary bypass (CPB). Canine genome sequencing allows profiling of genomic changes after HCA and CPB alone. We hypothesize that gene regulation will increase with increased severity of injury.

METHODS

Dogs underwent 2-hour HCA at 18 degrees C (n = 10), 1-hour HCA (n = 8), or 2-hour CPB at 32 degrees C alone (n = 8). In each group, half were sacrificed at 8 hours and half at 24 hours after treatment. After neurologic scoring, brains were harvested for genomic analysis. Hippocampal RNA isolates were analyzed using canine oligonucleotide expression arrays containing 42,028 probes.

RESULTS

Consistent with prior work, dogs that underwent 2-hour HCA experienced severe neurologic injury. One hour of HCA caused intermediate clinical damage. Cardiopulmonary bypass alone yielded normal clinical scores. Cardiopulmonary bypass, 1-hour HCA, and 2-hour HCA groups historically demonstrated increasing degrees of histopathologic damage (previously published). Exploratory analysis revealed differences in significantly regulated genes (false discovery rate < 10%, absolute fold change > or = 1.2), with increases in differential gene expression with injury severity. At 8 hours and 24 hours after insult, 2-hour HCA dogs had 502 and 1,057 genes regulated, respectively; 1-hour HCA dogs had 179 and 56 genes regulated; and CPB alone dogs had 5 and 0 genes regulated.

CONCLUSIONS

Our genomic profile of canine brains after HCA and CPB revealed 1-hour and 2-hour HCA induced markedly increased gene regulation, in contrast to the minimal effect of CPB alone. This adds to the body of neurologic literature supporting the safety of CPB alone and the minimal effect of CPB on a normal brain, while illuminating genomic results of both.

Is There a Future for Neuroprotective Agents in Cardiac Surgery?

This article gives an overview of neuroprotective drugs that were recently tested in clinical trials in cardiac surgery. Also, recommendations are given for successful translational research and considerations for management during cardiac surgery.

Neuroprotective effects of a combination of dexmedetomidine and hypothermia after incomplete cerebral ischemia in rats

BACKGROUND

Dexmedetomidine and hypothermia are known to reduce neuronal injury following cerebral ischemia. We examined whether a combination of dexmedetomidine and hypothermia reduces brain injury after transient forebrain ischemia in rats to a greater extent than either treatment alone.

METHODS

Thirty-eight male Sprague-Dawley rats were anesthetized with fentanyl and nitrous oxide in oxygen. Four groups were tested: group C (saline 1 ml/kg, temporal muscle temperature 37.5 degrees C); group H (saline 1 ml/kg, 35.0 degrees C); group D (dexmedetomidine 100 microg/kg, 37.5 degrees C); and group DH (dexmedetomidine 100 microg/kg, 35.0 degrees C). Dexmedetomidine or saline was administered intraperitoneally 30 min before ischemia. Cerebral ischemia was produced by right carotid artery ligation with hemorrhagic hypotension (mean arterial pressure 40 mmHg) for 20 min. Neurologic outcome was evaluated at 24, 48, and 72 h after ischemia. Histopathology was evaluated in the caudate and hippocampus at 72 h after ischemia.

RESULTS

Neurologic outcome was significantly better in the group DH than the group C (P<0.05), whereas it was similar between the group DH and the groups D or H. Survival rate of the hippocampal CA1 neurons was significantly greater in groups D, H, and DH than group C (P<0.05). Histopathologic injury in the caudate section was significantly less in groups H and DH than group C (P<0.05).

CONCLUSION

The combination of dexmedetomidine and hypothermia improved short-term neurologic outcome compared with the control group, whereas the combination therapy provided comparable neuroprotection with either of the two therapies alone.

Impaired autoregulation of cerebral blood flow during rewarming from hypothermic cardiopulmonary bypass and its potential association with stroke

BACKGROUND

Patient rewarming after hypothermic cardiopulmonary bypass (CPB) has been linked to brain injury after cardiac surgery. In this study, we evaluated whether cooling and then rewarming of body temperature during CPB in adult patients is associated with alterations in cerebral blood flow (CBF)-blood pressure autoregulation.

METHODS

One hundred twenty-seven adult patients undergoing CPB during cardiac surgery had transcranial Doppler monitoring of the right and left middle cerebral artery blood flow velocity. Eleven patients undergoing CPB who had arterial inflow maintained at >35 degrees C served as controls. The mean velocity index (Mx) was calculated as a moving, linear correlation coefficient between slow waves of middle cerebral artery blood flow velocity and mean arterial blood pressure. Intact CBF-blood pressure autoregulation is associated with an Mx that approaches 0. Impaired autoregulation results in an increasing Mx approaching 1.0. Comparisons of time-averaged Mx values were made between the following periods: before CPB (baseline), during the cooling and rewarming phases of CPB, and after CPB. The number of patients in each phase of CPB with an Mx >4.0, indicative of impaired CBF autoregulation, was determined.

RESULTS

During cooling, Mx (left, 0.29 +/- 0.18; right, 0.28 +/- 0.18 [mean +/- SD]) was greater than that at baseline (left, 0.17 +/- 0.21; right, 0.17 +/- 0.20; P <or= 0.0001). Mx increased during the rewarming phase of CPB (left, 0.40 +/- 0.19; right, 0.39 +/- 0.19) compared with baseline (P <or= 0.001) and the cooling phase (P <or= 0.0001), indicating impaired CBF autoregulation. After CPB, Mx (left, 0.27 +/- 0.20; right, 0.28 +/- 0.21) was higher than at baseline (left, P = 0.0004; right, P = 0.0003), no different than during the cooling phase, but lower than during rewarming (left, P <or= 0.0001; right, P <or= 0.0005). Forty-three patients (34%) had an Mx >or=0.4 during the cooling phase of CPB and 68 (53%) had an average Mx >or=0.4 during rewarming. Nine of the 11 warm controls had an average Mx >or=0.4 during the entire CPB period. There were 7 strokes and 1 TIA after surgery. All strokes were in patients with Mx >or= 0.4 during rewarming (P = 0.015). The unadjusted odds ratio for any neurologic event (stroke or transient ischemic attack) for patients with Mx >or= 0.4 during rewarming was 6.57 (95% confidence interval, 0.79 to 55.0, P < 0.08).

CONCLUSIONS

Hypothermic CPB is associated with abnormal CBF-blood pressure autoregulation that is worsened with rewarming. We found a high rate of strokes in patients with evidence of impaired CBF autoregulation. Whether a pressure-passive CBF state during rewarming is associated with risk for ischemic brain injury requires further investigation.

The Need for Specialized Preanesthesia Clinics for Day Admission Cardiac and Major Vascular Surgery Patients

The majority of patients undergoing surgical procedures today are not admitted to the hospital prior to the morning of surgery. In a medical world that strives not only for patient safety, but also for cost containment, Day Admission Surgery (DAS) plays an important role in our healthcare systems. This is true even for patients undergoing cardiac and major vascular (CMV) procedures. However, CMV patients often present with more complicated pre-, intra- and post-operative issues than other surgical patients.

In order to optimize the preoperative evaluation and care of CMV patients, we developed a specialized Pre-Anesthesia Clinic (PAC). We believed that patients, surgeons, anesthesiologists, and intensive care unit (ICU) teams would all benefit when appropriate preoperative evaluations are thoughtfully performed by those specializing in the care of these complicated patients. Planning for this specialized clinic included a survey of other institutions’ practices. Following initiation of our clinic, we performed a patient satisfaction survey. We report these findings along with the demographic data concerning the patients and types of surgeries evaluated in our initial experience. Finally, we discuss the preoperative evaluation including various areas of assessment provided by our PAC.