The effect of temperature management during cardiopulmonary bypass on neurologic and neuropsychologic outcomes in patients undergoing coronary revascularization

Adipose Tissue in Peripheral Obesity as an Assessment Factor for Pressure Ulcers

Scope and Significance: Pressure ulcers are very difficult to treat and pose an economic burden, just below cancer and cardiovascular illness, at 4.82 billion U.S. dollars. It is important to understand the pathophysiology of the condition, risk stratification, and ways of preventing it. Prevention forms the most important aspect of their management. The authors systematically evaluated the existing risk prediction scales and explored the evidence from literature regarding the role of additional factors including body mass index, obesity, subcutaneous tissue thickness, and skin integrity in pressure ulcers. With this review it is hoped that the future management of pressure ulcers will concentrate on the preventable and alterable factors in its pathophysiology. Translational Relevance: The review focuses on how adipose tissue thickness can predict the occurrence of pressure ulcer. If adequately proved that a definite thickness of peripheral adipose tissue is efficient in prevention of pressure ulcers, then methods of maintaining the thickness of this tissue will be the next effective strategy in the management of this chronic issue. Clinical Relevance: The review addresses the management of pressure ulcers to wound care providers and emphasize on confounding parameters of obesity, subcutaneous tissue thickness, and skin integrity during the treatment regimen of pressure ulcers. Objectives: The main objective of this review is to draw a consensus concerning the role of adipose tissue in pressure ulcers, based on the published research. A review of the various preexisting predictive scales for pressure ulcers is a secondary objective to highlight the shortcomings in ulcer management. This review finally aims in the future at paving a way to refine our prognosticating scales for pressure sores based on these results. Accurate preventative injury risk scales are needed so that preventative resources can be directed to the patients for whom they are the most appropriate.

Functional recovery after accidental deep hypothermic cardiac arrest: Comparison of different cardiopulmonary bypass rewarming strategies

Introduction: Using a porcine model of accidental immersion hypothermia and hypothermic cardiac arrest (HCA), the aim of the present study was to compare effects of different rewarming strategies on CPB on need for vascular fluid supply, level of cardiac restitution, and cerebral metabolism and pressures.

Materials and Methods: Totally sixteen healthy, anesthetized castrated male pigs were immersion cooled to 20°C to induce HCA, maintained for 75 min and then randomized into two groups: 1) animals receiving CPB rewarming to 30°C followed by immersion rewarming to 36°C (CPB₃₀, n = 8), or 2) animals receiving CPB rewarming to 36°C (CPB₃₆, n = 8). Measurements of cerebral metabolism were collected using a microdialysis catheter. After rewarming to 36°C, surviving animals in both groups were further warmed by immersion to 38°C and observed for 2 h.

Results: Survival rate at 2 h after rewarming was 5 out of 8 animals in the CPB₃₀ group, and 8 out of 8 in the CPB₃₆ group. All surviving animals displayed significant acute cardiac dysfunction irrespective of rewarming method. Differences between groups in CPB exposure time or rewarming rate created no differences in need for vascular volume supply, in variables of cerebral metabolism, or in cerebral pressures and blood flow.

Conclusion: As 3 out of 8 animals did not survive weaning from CPB at 30°C, early weaning gave no advantages over weaning at 36°C. Further, in surviving animals, the results showed no differences between groups in the need for vascular volume replacement, nor any differences in cerebral blood flow or pressures. Most prominent, after weaning from CPB, was the existence of acute cardiac failure which was responsible for the inability to create an adequate perfusion irrespective of rewarming strategy.

Guidelines on enhanced recovery after cardiac surgery under cardiopulmonary bypass or off-pump

OBJECTIVE

To provide recommendations for enhanced recovery after cardiac surgery (ERACS) based on a multimodal perioperative medicine approach in adult cardiac surgery patients with the aim of improving patient satisfaction, reducing postoperative mortality and morbidity, and reducing the length of hospital stay.

DESIGN

A consensus committee of 20 experts from the French Society of Anaesthesia and Intensive Care Medicine (Société française d'anesthésie et de réanimation, SFAR) and the French Society of Thoracic and Cardiovascular Surgery (Société française de chirurgie thoracique et cardio-vasculaire, SFCTCV) was convened. A formal conflict-of-interest policy was developed at the onset of the process and enforced throughout. The entire guideline process was conducted independently of any industry funding. The authors were advised to follow the principles of the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system to guide the assessment of the quality of evidence.

METHODS

Six fields were defined: (1) selection of the patient pathway and its information; (2) preoperative management and rehabilitation; (3) anaesthesia and analgesia for cardiac surgery; (4) surgical strategy for cardiac surgery and bypass management; (5) patient blood management; and (6) postoperative enhanced recovery. For each field, the objective of the recommendations was to answer questions formulated according to the PICO model (Population, Intervention, Comparison, Outcome). Based on these questions, an extensive bibliographic search was carried out and analyses were performed using the GRADE approach. The recommendations were formulated according to the GRADE methodology and then voted on by all the experts according to the GRADE grid method.

RESULTS

The SFAR/SFCTCV guideline panel provided 33 recommendations on the management of patients undergoing cardiac surgery under cardiopulmonary bypass or off-pump. After three rounds of voting and several amendments, a strong agreement was reached for the 33 recommendations. Of these recommendations, 10 have a high level of evidence (7 GRADE 1+ and 3 GRADE 1-); 19 have a moderate level of evidence (15 GRADE 2+ and 4 GRADE 2-); and 4 are expert opinions. Finally, no recommendations were provided for 3 questions.

CONCLUSIONS

Strong agreement existed among the experts to provide recommendations to optimise the complete perioperative management of patients undergoing cardiac surgery.

Renal and Cerebral Hypoxia and Inflammation During Cardiopulmonary Bypass

Cardiac surgery-associated acute kidney injury and brain injury remain common despite ongoing efforts to improve both the equipment and procedures deployed during cardiopulmonary bypass (CPB). The pathophysiology of injury of the kidney and brain during CPB is not completely understood. Nevertheless, renal (particularly in the medulla) and cerebral hypoxia and inflammation likely play critical roles. Multiple practical factors, including depth and mode of anesthesia, hemodilution, pump flow, and arterial pressure can influence oxygenation of the brain and kidney during CPB. Critically, these factors may have differential effects on these two vital organs. Systemic inflammatory pathways are activated during CPB through activation of the complement system, coagulation pathways, leukocytes, and the release of inflammatory cytokines. Local inflammation in the brain and kidney may be aggravated by ischemia (and thus hypoxia) and reperfusion (and thus oxidative stress) and activation of resident and infiltrating inflammatory cells. Various strategies, including manipulating perfusion conditions and administration of pharmacotherapies, could potentially be deployed to avoid or attenuate hypoxia and inflammation during CPB. Regarding manipulating perfusion conditions, based on experimental and clinical data, increasing standard pump flow and arterial pressure during CPB appears to offer the best hope to avoid hypoxia and injury, at least in the kidney. Pharmacological approaches, including use of anti-inflammatory agents such as dexmedetomidine and erythropoietin, have shown promise in preclinical models but have not been adequately tested in human trials. However, evidence for beneficial effects of corticosteroids on renal and neurological outcomes is lacking. © 2021 American Physiological Society. Compr Physiol 11:1-36, 2021.

Blood-Brain Barrier Disruption After Cardiopulmonary Bypass: Diagnosis and Correlation to Cognition

BACKGROUND

Cardiopulmonary bypass (CPB) elicits a systemic inflammatory response that may impair blood-brain barrier (BBB) integrity. BBB disruption can currently be detected by dynamic contrast enhancement magnetic resonance imaging (MRI), reflected by an increase in the permeability constant (K^trans). We aimed to determine (1) whether CPB induces BBB disruption, (2) duration until BBB disruption resolution, and (3) the obtainable correlation between BBB injury (location and intensity) and neurocognitive dysfunction.

METHODS

Seven patients undergoing CPB with coronary artery bypass grafting (CABG) were assigned to serial cerebral designated MRI evaluations, preoperatively and on postoperative day (POD) 1 and 5. Examinations were analyzed for BBB disruption and microemboli using dynamic contrast enhancement MRI and diffusion-weighted imaging methods, respectively. Neuropsychologic tests were performed 1 day preoperatively and on POD 5.

RESULTS

A significant local K^trans increase (0.03 min^-1 vs 0.07 min^-1, p = 0.033) compatible with BBB disruption was evident in 5 patients (71%) on POD 1. Resolution was observed by POD 5 (mean, 0.012 min^-1). The location of the disruption was most prominent in the frontal lobes (400% vs 150% K^trans levels upsurge, p = 0.05). MRI evidence of microembolization was demonstrated in only 1 patient (14%). The postoperative global cognitive score was reduced in all patients (98.2 ± 12 vs 95.1 ± 11, p = 0.032), predominantly in executive and attention (frontal lobe-related) functions (91.8 ± 13 vs 86.9 ± 12, p = 0.042). The intensity of the dynamic contrast enhancement MRI BBB impairment correlated with the magnitude of cognition reduction (r = 0.69, p = 0.04).

CONCLUSIONS

BBB disruption was evident in most patients, primarily in the frontal lobes. The location and intensity of the BBB disruption, rather than the microembolic load, correlated with postoperative neurocognitive dysfunction.

Aortic Arch Atheroma: Stroke Reduction in Cardiac Surgical Patients

Cardiac surgery is increasingly performed on elderly patients with extensive coronary artery abnormalities who have impaired left ventricular function, decreased physiologic reserve, and multiple comorbid conditions. Considerable numbers of these patients develop perioperative neurologic complications ranging from subtle cognitive dysfunction to more evident postoperative confusion, delirium, and, less commonly, clinically apparent stroke. Magnetic resonance imaging studies have elucidated that a considerable number of patients have new ischemic brain infarcts, particularly after conventional coronary artery bypass graft surgery. Mechanisms of cerebral injury during and after cardiac surgery are discussed. Intraoperative transesophageal echocardiography and epiaortic scanning for detection of atheromatous disease of the proximal thoracic aorta is paramount in identifying patients at high risk from neurologic injury. It is important to recognize that our efforts to minimize neurologic injury should not be limited to the intraoperative period. Particular efforts should be directed to temperature management, glycemia control, and pharmacologic neuroprotection extending into the postoperative period. Preoperative magnetic resonance angiography may be of value for screening patients with significant atheroma of the proximal thoracic aorta. It is likely that for patients with no significant atheromatous disease, conventional coronary artery revascularization is the most effective long-term strategy, whereas patients with atheromatous thoracic aorta may be better managed with beating heart surgery, hybrid techniques, or medical therapy alone. Patient stratification based on the aortic atheromatic burden should be addressed in future trials designed to tailor treatment strategies to improve long-term outcomes of coronary heart disease and reduce the risks of perioperative neurologic injury.

Strategies to Protect the Brain During Cardiac Surgery

Despite significant advances in cardiopulmonary by pass (CPB) technology, surgical techniques, and anes thetic management, central nervous system (CNS) com plications remain a common and costly problem after CPB. Stroke is often considered a rare and unprevent able complication of cardiac surgery. Recent studies have shown that through the use of echocardiography and historical risk stratification strategies, we can de fine which patients are at substantially greater risk for CNS injury. Through enhanced understanding of the etiology of stroke and perioperative factors, which are associated with potential for neuroprotection or injury extension, there now exists a greater potential than ever to substantially reduce neurological injury associ ated with cardiac surgery. Strategies and theories of stratifying patients at risk and secondarily reducing that risk are described, as well as consideration for early postoperative assessment to allow treatment when events occur.

Optimal Temperature Management During Cardiopulmonary Bypass: Warm, Cold, or Tepid?

Hypothermia permitted the advent of cardiac surgery and is considered by many the mainstay of cerebral protection during cardiopulmonary bypass (CPB). How ever, some clinicians have questioned the importance of reduced temperatures during CPB and advocate "normo thermic" heart surgery. Hypothermia (mild, moderate, and profound) provides protection during periods of inadequate oxygen delivery by at least two mecha nisms. First, metabolic rate is directly related to tempera ture ; therefore, reduced temperatures increase toler ance to inadequate oxygen delivery. Q10 values (the ratio of metabolic rates at temperature X°C and tempera ture X°C - 10°C) are controversial and are reported as varying between 2.0 and 5.0. During profound hypother mia (temperature = 17°C), metabolic requirements are 10% to 15% of normothermic values. Second, reduced temperatures (even minimal reductions [34°C to 35°C]) attenuate the release of glutamate and other excitatory amines from ischemic neuronal cells. This phenomenon is thought to play an important role in hypothermic cerebral protection. Many investigators have assessed the impact of normothermic temperatures on cerebral outcomes in cardiac surgery patients. Although seem ingly conflicting conclusions are reported, this much is clear: cerebral temperatures in excess of 37°C exacer bate ischemic injury and even mild hypothermia re duces central nervous system damage in the ischemic brain.

Temperature Management During Cardiopulmonary Bypass: Effect of Rewarming Rate on Cognitive Dysfunction

Hypothermia is a very strong neuroprotective agent during cerebral ischemia. However, several randomized clinical trials have failed to demonstrate a protective effect of hypothermic cardiopulmonary bypass on postoperative cognitive deficits. The lack of neuroprotection may be due to rapid rewarming, which in turn may result in cerebral hyperthermia. The purpose of this study was to detennine if rapid rewarming at the end of cardiopulmonary bypass is associated with an increased risk of postoperative neuropsychologic impairment.

Methods: A battery of neuropsychologic tests were administered preand postoperatively to patients undergoing elective coronary bypass surgery. Patients were allowed to drift to 34°C then rewarmed to 37.5°C at the end of cardiopulmonary bypass. Patients were divided into 2 groups according to the median time to rewarm (21 minutes): a rapid group (n = 70) and a slow group (n = 76).

Results: The 2 groups of patients were similar for all pre-, intra-, and postoperative variables, with the exception of rewarming times (15 ± 4 minutes [mean ± SD]) in the rapid group versus 30 ± 9 minutes in the slow group, p < 0.001). The rapid group had a significantly higher prevalence of neuropsychologic impairment 1 week postoperatively than the slow group (82% versus 57%, p < 0.05), as well as worse mean scores on all neuropsychologic tests. There was a nonsignificant trend toward increased neuropsychologic impairment 3 months postoperatively in the rapid group, as well as worse mean scores on 8 of the 10 tests.

Conclusions: Rapid rewarming at the end of cardiopulmonary bypass may increase the risk of postoperative cognitive impairment. Until further studies are performed, rapid rewarming should be avoided in order to minimize the risk of cerebral hyperthermia.

Lessons learned on the path to a healthier brain: dispelling the myths and challenging the hypotheses

Neurologic dysfunction remains the most significant complication associated with cardiopulmonary bypass (CPB). The insidious change of cognitive decline has been perceived as a key factor that has contributed to the shift to percutaneous intervention for coronary disease. Current neuropsychologic testing provides the most sensitive means of demonstrating clinically relevant cerebral damage of this nature. Through extensive experience in randomized clinical trials of over 900 patients undergoing CPB, our team has addressed several key hypotheses related to the embolic/ischemic nature of cerebral injury in cardiac surgery, using this testing. In the first temperature study, patients randomized to hypothermia with passive re-warming had a lower incidence of neurocognitive deficit when compared with those patients who were actively re-warmed to 37°. In order to clarify the role of the hypothermia as opposed to the re-warming process, a second temperature study was completed. In the hypothermic group, patients were cooled and maintained at 34° with no active re-warming whereas, in the normothermic group, the patients were kept at 37° throughout the perioperative period. No difference in neurocognitive outcome in the two groups was seen, implying that the benefit seen in the first temperature study was related not to the hypothermia, but rather to the absence of active re-warming. In the cardiotomy study, patients were randomized to either a control group in which their cardiotomy blood was returned unprocessed, or a treatment group in which this blood was sequestered and processed with centrifugal washing and fat filtration. No significant difference in neurocognitive outcome was found in these two groups. On the other hand, there was a significant increase in bleeding and transfusion requirements in the treatment group. Many of our daily practices in CPB management are based upon assumptions from observational studies without sound reference to evidence-based medicine. Our recent studies have challenged our assumptions related to ischemia and embolic events during CPB. They have also confirmed that, when high standards in trial design are applied, the results can have universal implications in terms of our practice. Perfusion (2007) 22, 153—160.

Ischemia reperfusion injury as a modifiable therapeutic target for cardioprotection or neuroprotection in patients undergoing cardiopulmonary resuscitation

AIMS

We sought to review cellular changes that occur with reperfusion to try to understand whether ischemia-reperfusion injury (RI) is a potentially modifiable therapeutic target for cardioprotection or neuroprotection in patients undergoing cardiopulmonary resuscitation.

DATA SOURCES

Articles written in English and published in PubMed.

RESULTS

Remote ischemic conditioning (RIC) involves brief episodes of non-lethal ischemia and reperfusion applied to an organ or limb distal to the heart and brain. Induction of hypothermia involves cooling an ischemic organ or body. Both have pluripotent effects that reduce the potential harm associated with RI in the heart and brain by reduced opening of the mitochondrial permeability transition pore. Recent trials of RIC and induced hypothermia did not demonstrate these treatments to be effective. Assessment of the effect of these interventions in humans to date may have been modified by use of concurrent medications including propofol.

CONCLUSIONS

Ongoing research is necessary to assess whether reduction of RI improves patient outcomes.

Risk Factors Associated with Cognitive Decline after Cardiac Surgery: A Systematic Review

Modern day cardiac surgery evolved upon the advent of cardiopulmonary bypass machines (CPB) in the 1950s. Following this development, cardiac surgery in recent years has improved significantly. Despite such advances and the introduction of new technologies, neurological sequelae after cardiac surgery still exist. Ischaemic stroke, delirium, and cognitive impairment cause significant morbidity and mortality and unfortunately remain common complications. Postoperative cognitive decline (POCD) is believed to be associated with the presence of new ischaemic lesions originating from emboli entering the cerebral circulation during surgery. Cardiopulmonary bypass was thought to be the reason of POCD, but randomised controlled trials comparing with off-pump surgery show contradictory results. Attention has now turned to the growing evidence that perioperative risk factors, as well as patient-related risk factors, play an important role in early and late POCD. Clearly, identifying the mechanism of POCD is challenging. The purpose of this systematic review is to discuss the literature that has investigated patient and perioperative risk factors to better understand the magnitude of the risk factors associated with POCD after cardiac surgery.

Myocardial injury following aortic valve replacement for severe aortic stenosis: risk factor of postoperative myocardial injury and its impact on long-term outcomes

Background

As hypertrophied myocardium predisposes the patient to decreased tolerance to ischemia and increased reperfusion injury, myocardial protection is of utmost importance in patients undergoing aortic valve replacement (AVR) for severe aortic valve stenosis (AS).

Methods

Consecutive 314 patients (mean age, 62.5±10.8 years; 143 females) with severe AS undergoing isolated AVR were included. Postoperative myocardial injury (PMI) was defined as 1) maximum postoperative creatinine kinase isoenzyme MB or troponin-I levels ≥10 times of reference, 2) postoperative low cardiac output syndrome or episodes of ventricular arrhythmia, or 3) left ventricular ejection fraction of less than 55% and decrease in left ventricle (LV) ejection fraction of more than 20% of the baseline value.

Results

There were 90 patients (28.7%) who developed PMI. There were five cases of early death (1.6%), all of whom had PMI. On multivariable analysis, the use of histidine-tryptophan-ketoglutarate (HTK) solution instead of blood cardioplegia (odds ratio [OR], 3.06; 95% confidence interval [CI], 1.63 to 5.77; p=0.001), greater LV mass (OR, 1.04; 95% CI, 1.01 to 1.07; p=0.007), and increased cardiac ischemic time (OR, 1.13; 95% CI, 1.05 to 1.22; p<0.001) were independent predictors for PMI. Patients who had PMI showed significantly inferior long-term survival than those without PMI (p=0.049).

Conclusion

PMI occurred in a considerable proportion of patients undergoing AVR for severe AS and was associated with poor long-term survival. HTK cardioplegia, higher LV mass, and longer cardiac ischemic duration were suggested as predictors of myocardial injury.

Preexisting depressive symptoms are associated with long-term cognitive decline in patients after cardiac surgery

OBJECTIVE

To examine whether preoperative psychological dysfunctions rather than intraoperative factors may differentially predict short- and long-term postoperative cognitive decline (POCD) in patients after cardiac surgery.

METHOD

Forty-two patients completed a psychological evaluation, including the Trail Making Test Part A and B (TMT-A/B), the memory with 10/30-s interference, the phonemic verbal fluency and the Center for Epidemiological Studies of Depression (CES-D) scale for cognitive functions and depressive symptoms, respectively, before surgery, at discharge and at 18-month follow-up.

RESULTS

Ten (24%) and 11 (26%) patients showed POCD at discharge and at 18-month follow-up, respectively. The duration of cardiopulmonary bypass significantly predicted short-term POCD [odds ratio (OR)=1.04, P<.05], whereas preoperative psychological factors were unrelated to cognitive decline at discharge. Conversely, long-term cognitive decline after cardiac surgery was significantly predicted by preoperative scores in the CES-D (OR=1.26, P<.03) but not by intraoperative variables (all Ps >.23).

CONCLUSIONS

Our findings showed that preexisting depressive symptoms rather than perioperative risk factors are associated with cognitive decline 18 months after cardiac surgery. This study suggests that a preoperative psychological evaluation of depressive symptoms is essential to anticipate which patients are likely to show long-term cognitive decline after cardiac surgery.

Effects of intraoperative external head cooling on short-term cognitive function in patients after coronary artery bypass graft surgery

The aim of study was to assess the effects of an intraoperative external head-cooling technique on cognitive dysfunction in the early postoperative period (at the 10th day) in patients after coronary artery bypass graft (CABG) surgery. Patients in Group H (n=25) were cooled with CPB and the intraoperative, external head-cooling technique, patients in Group C (n=25) were cooled only with cardiopulmonary bypass (CPB) to achieve mild hypothermia (33 - 34 °C). Cognitive function was analyzed before the operation and after the surgery using the Mini Mental State Examination (MMSE), the Modified Visual Reproduction Test from the Wechsler Memory Scale, Trail Making (A/B), WAIS--Digit Span (WDS) and WAIS Digit Symbol Substitution Test (WDSST). The incidence of cognitive impairment at the 10th day after the surgery was 36% (n=9) in Group H and 64% (n=16) in Group C (p=0.048). The temperature during the aortic cross-clamp period was associated with a lower rate of cognitive dysfunction (p=0.05, r(2)=0.09). The intraoperative, external head-cooling technique during the aortic cross-clamp period has a neuroprotective effect and leads to less short-term cognitive function impairment after CABG surgery.

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.

The benefits of cognitive training after a coronary artery bypass graft surgery

Cognitive deficits are frequent after coronary artery bypass graft surgery (CABG) in the elderly population. In fact, memory and attention deficits can persist several months after the surgery. Recent studies with healthy older adults have shown that memory and attention can be improved through cognitive training programs. The present study examined whether memory training (method of loci and story generation) and attentional training (dual-task computerized training) could improve cognitive functions in patients aged 65 years and older who underwent CABG surgery. Participants (n = 51) were assigned to one of three groups: (1) control group (tested at 1, 3 and 6 months after the surgery), (2) attention training followed by memory training, (3) memory training followed by attention training (groups 2 and 3: tested at 1, 2, 3 and 6 months after the surgery). The trainings took place between the 6th and 10th week following the surgery. The three groups were compared before and after each training program using attention and memory tests and neuropsychological tests. The results showed that attention and memory trainings lead to significant improvement in the cognitive domain that was trained. It thus seems that cognitive training can be a promising tool to enhance cognitive functions after a CABG surgery.

Measurement of post-operative cognitive dysfunction after cardiac surgery: a systematic review

Post-operative cognitive dysfunction (POCD) is a decline in cognitive function from pre-operative levels, which has been frequently described after cardiac surgery. The purpose of this study was to examine the variability in the measurement and definitions for POCD using the framework of a 1995 Consensus Statement on measurement of POCD. Electronic medical literature databases were searched for the intersection of the search terms 'thoracic surgery' and 'cognition, dementia, and neuropsychological test.' Abstracts were reviewed independently by two reviewers. English articles with >50 participants published since 1995 that performed pre-operative and post-operative psychometric testing in patients undergoing cardiac surgery were reviewed. Data relevant to the measurement and definition of POCD were abstracted and compared with the recommendations of the Consensus Statement. Sixty-two studies of POCD in patients undergoing cardiac surgery were identified. Of these studies, the recommended neuropsychological tests were carried out in less than half of the studies. The cognitive domains measured most frequently were attention (n=56; 93%) and memory (n=57; 95%); motor skills were measured less frequently (n=36; 60%). Additionally, less than half of the studies examined anxiety and depression, performed neurological exam, or accounted for learning. Four definitions of POCD emerged: per cent decline (n=15), standard deviation decline (n=14), factor analysis (n=13), and analysis of performance on individual tests (n=12). There is marked variability in the measurement and definition of POCD. This heterogeneity may impede progress by reducing the ability to compare studies on the causes and treatment of POCD.

Perioperative hypothermia: use and therapeutic implications

Perioperative cerebral ischemic insults are common in some surgical procedures. The notion that induced hypothermia can be employed to improve outcome in surgical patients has persisted for six decades. Its principal application has been in the context of cardiothoracic and neurosurgery. Mild (32-35 degrees C) and moderate (26-31 degrees C) hypothermia have been utilized for numerous procedures involving the heart, but intensive research has found little or no benefit to outcome. This may, in part, be attributable to confounding effects associated with rewarming and lack of understanding of the mechanisms of injury. Evidence of efficacy of mild hypothermia is absent for cerebral aneurysm clipping and carotid endarterectomy. Deep hypothermia (18-25 degrees C) during circulatory arrest has been practiced in the repair of congenital heart disease, adult thoracic aortas, and giant intracranial aneurysms. There is little doubt of the protective efficacy of deep hypothermia, but continued efforts to refine its application may serve to enhance its utility. Recent evidence that mild hypothermia is efficacious in out-of-hospital cardiac arrest has implications for patients incurring anoxic or global ischemic brain insults during anesthesia and surgery, or perioperatively. Advances in preclinical models of ischemic/anoxic injury and cardiopulmonary bypass that allow definition of optimal cooling strategies and study of cellular and subcellular events during perioperative ischemia can add to our understanding of mechanisms of hypothermia efficacy and provide a rationale basis for its implementation in humans.

Induced hypothermia and fever control for prevention and treatment of neurological injuries

Increasing evidence suggests that induction of mild hypothermia (32-35 degrees C) in the first hours after an ischaemic event can prevent or mitigate permanent injuries. This effect has been shown most clearly for postanoxic brain injury, but could also apply to other organs such as the heart and kidneys. Hypothermia has also been used as a treatment for traumatic brain injury, stroke, hepatic encephalopathy, myocardial infarction, and other indications. Hypothermia is a highly promising treatment in neurocritical care; thus, physicians caring for patients with neurological injuries, both in and outside the intensive care unit, are likely to be confronted with questions about temperature management more frequently. This Review discusses the available evidence for use of controlled hypothermia, and also deals with fever control. Besides discussing the evidence, the aim is to provide information to help guide treatments more effectively with regard to timing, depth, duration, and effective management of side-effects. In particular, the rate of rewarming seems to be an important factor in establishing successful use of hypothermia in the treatment of neurological injuries.

Neuroprotection during cardiac surgery

Cardiac surgery continues to be associated with significant adverse cerebral outcomes, ranging from stroke to cognitive decline. The underlying mechanism of the associated cerebral injury is incompletely understood but is believed to be primarily caused by cerebral embolism and hypoperfusion, exacerbated by ischemia/reperfusion injury. Extensive research has been undertaken in an attempt to minimize the incidence of perioperative cerebral injury, and both pharmacological and nonpharmacological strategies have been investigated. Although many agents demonstrated promise in preclinical studies, there is currently insufficient evidence from clinical trials to recommend the routine administration of any pharmacological agents for neuroprotection during cardiac surgery. The nonpharmacological strategies that can be recommended on the basis of evidence include transesophageal echocardiography and epiaortic ultrasound-guided assessment of the atheromatous ascending aorta with appropriate modification of cannulation, clamping or anastomotic technique and optimal temperature management. Large-scale randomized controlled trials are still required to address further the issues of optimal pH management, glycemic control, blood pressure management and hematocrit during cardiopulmonary bypass. Past, present and future directions in the field of neuroprotection in cardiac surgery will be discussed.

Use of induced hypothermia for neuroprotection: indications and application

Therapeutic temperature regulation has become an exciting field of interest. Mild-to-moderate hypothermia is a safe and feasible management strategy for neuroprotection and control of intracranial pressure in neurological catastrophies such as traumatic brain injury, subarachnoid and intracerebral hemorrhage, and large hemispheric stroke. Fever is associated with worse neurological outcome in patients with brain injury, normothermia may be of benefit in this patient population. The efficacy of mild-to-moderate hypothermia has been proven for neuroprotection after cardiac arrest with ventricular fibrillation as initial rhythm, and after neonatal asphyxia. Application of hypothermia and fever control in neurocritical care, available cooling technologies and systemic effects and complications of hypothermia will be discussed.

The effect of limited rewarming and postoperative hypothermia on cognitive function in a rat cardiopulmonary bypass model

BACKGROUND

Clinical studies have failed to demonstrate significant benefits of hypothermia for the prevention of postoperative cognitive dysfunction (POCD) after cardiopulmonary bypass (CPB). One explanation for this might be that potentially injurious cerebral hyperthermia occurs during rewarming at the end of CPB, off-setting the protective benefits of hypothermia. In this study, we investigated the relative influence of CPB temperature, rewarming strategies, and postoperative temperature in a rat CPB model.

METHODS

Four groups of male Sprague-Dawley rats were surgically prepared and subjected to 90 min of CPB. Group A was normothermic (37.5 degrees C) during and after CPB. Group B underwent hypothermic (32 degrees C) CPB, followed by rewarming to 37.5 degrees C at the end of bypass. Group C had hypothermic (32 degrees C) CPB, followed by limited rewarming to 35 degrees C. Group D had normothermic CPB with hypothermia (35 degrees C) induced only postoperatively. Groups were compared for POCD determined by the performance in the Morris water maze on postoperative days 3-9. Histologic analysis of the brains (CA1 and CA3 hippocampal regions) was also performed.

RESULTS

Hypothermia induced only during (group B versus group A) or after CPB (group D versus group A) conferred no significant POCD benefit. Hypothermia when induced during CPB and continued into the postoperative period resulted in a significant improvement in water maze performance versus all other temperature regimens (group C versus group A, P = 0.044; group C versus group B, P = 0.011; group C versus group D, P = 0.012). No histological differences among groups were demonstrated.

CONCLUSIONS

The combination of hypothermic (32 degrees C) CPB coupled with limited rewarming and prolonged postoperative hypothermia (35 degrees C) decreased POCD after CPB in rats.

Therapeutic hypothermia for global and focal ischemic brain injury--a cool way to improve neurologic outcomes

BACKGROUND

Therapeutic hypothermia (TH) has been employed as a neuroprotective strategy for a wide array of clinical problems since the late 1940s. Animal studies have determined that the neuroprotective effect of hypothermia is pleiotropic, impacting many steps in both the ischemic cascade and reperfusion injury. Interest in the neuroprotective effects of TH for ischemic brain injury has been resurgent, fueled by both recent positive and negative clinical trials. A review of preclinical and clinical reports on TH in adult patients is provided in this article.

REVIEW SUMMARY

Animal data and several large clinical studies of mild to moderate TH (32 degrees C-34 degrees C) for global cerebral ischemia describe favorable neurologic outcomes, with few adverse effects. However, clinical implementation for global ischemia remains poor. Some animal data support a role for TH in focal cerebral ischemia, if instituted soon after the onset of ischemia, and in the setting of reperfusion. Clinical studies of TH for focal cerebral ischemia have so far been equivocal. The available data suggest that, despite sharing some common components in the ischemic cascade, focal and global cerebral ischemia are pathophysiologically disparate, and may respond to different neuroprotective strategies.

CONCLUSION

TH is a safe, effective neuroprotective strategy for global cerebral ischemia. Because of the neuroprotective efficacy of TH in adult comatose survivors of cardiac arrest, neurologists should advocate the implementation of this strategy. TH for focal ischemia is a promising therapeutic option, but requires more basic and clinical investigation.

Neuroprotection during cardiac surgery

Cerebral injury following cardiac surgery continues to be a significant source of morbidity and mortality after cardiac surgery. A spectrum of injuries ranging from subtle neurocognitive dysfunction to fatal strokes are caused by a complex series of multifactorial mechanisms. Protecting the brain from these injuries has focused on intervening on each of the various etiologic factors. Although numerous studies have focused on a pharmacologic solution, more success has been found with nonpharmacologic strategies, including optimal temperature management and reducing emboli generation.

Neuroprotective effect of mild hypothermia in patients undergoing coronary artery surgery with cardiopulmonary bypass: Five-year follow-up of a randomized trial

OBJECTIVE

In a randomized trial of 223 patients undergoing coronary artery surgery with cardiopulmonary bypass, we have reported a neuroprotective effect of mild hypothermia. To determine whether the beneficial effect of mild hypothermia was long-lasting, we repeated the psychometric tests in 131 patients after 5 years.

METHODS

Patients were cooled to 32 degrees C during aortic crossclamping and then randomized to rewarming to either 34 degrees C or 37 degrees C, with no further rewarming until arrival in intensive care unit. Cognitive function was measured preoperatively and 1 week and 5 years postoperatively with a battery of 11 psychometric tests interrogating verbal memory, attention, and psychomotor speed and dexterity.

RESULTS

Patients who had greater cognitive decline 1 week after surgery showed poorer performance 5 years later. The magnitude of cognitive decline over 5 years was modest. The incidence of deficits defined as a 1 standard deviation [SD] decline in at least 1 of 3 factors was not different between temperature groups. Fewer patients in the hypothermic group had deficits that persisted over the 5 years, but this difference did not attain statistical significance (RR = 0.64, P = .16).

CONCLUSIONS

The effect of surgery on cognitive function observed early after surgery is an important predictor of cognitive performance 5 years later. Although there was evidence of a neuroprotective effect of mild hypothermia early after surgery in the original cohort, the results after 5 years were inconclusive. In general, the magnitude of cognitive changes over 5 years was modest. We believe that further trials investigating the efficacy of mild hypothermia in patients having cardiac surgery are warranted.

Postcardiac Surgical Cognitive Impairment in the Aged Using Diffusion-Weighted Magnetic Resonance Imaging

BACKGROUND

Cardiac surgery is associated with cerebral dysfunction. While 1% to 2% of patients experience stroke, cognitive deficits are seen in more than half of patients. Given the high incidence of cognitive decline, it has become the endpoint of many cardiac surgery investigations. Because the elderly are at highest risk, this investigation sought to determine if there is a relationship between new ischemic changes demonstrated by diffusion-weighted magnetic resonance imaging (DW-MRI) and postoperative cognitive deficit in older patients.

METHODS

Fifty cardiac surgical patients (>65 years of age) underwent preoperative and postoperative neurocognitive examinations, including four to six week, postdischarge, follow-up. This evaluation assessed higher cortical function, memory, attention, concentration, and psychomotor performance. Objective evidence of acute cerebral ischemic events was identified using DW-MRI. Scans were analyzed by a neuroradiologist blinded to clinical status and cognitive outcomes.

RESULTS

Among patients with a mean age of 73 years, 88% demonstrated cognitive decline in the postoperative testing period while 32% showed evidence of acute perioperative cerebral ischemia by DW-MRI. At postdischarge follow-up, 30% of patients showed cognitive impairment. However, cognitive decline assessed postoperatively, or at a four to six week follow-up, was unrelated to the presence or absence of DW-MRI detected cerebral ischemia.

CONCLUSIONS

Postoperative neurocognitive impairment, assessed by standard means, is unrelated to acute cerebral ischemia detected by DW-MRI. This strongly suggests that cognitive decline after cardiac surgery is a function of underlying patient factors rather than perioperative ischemic events. This observation has broad implications for future investigation of strategies to prevent cardiac surgery-related neurologic injury.

Temperature During Cardiopulmonary Bypass: The Discrepancies Between Monitored Sites

We performed studies in patients to determine whether temperature recordings from sites commonly monitored during hypothermic cardiopulmonary bypass adequately reflect cerebral temperature. In Study I (n = 12), temperatures monitored in the jugular bulb (JB) were compared with those recorded in the nasopharynx, esophagus, bladder, and rectum. In Study II (n = 30), temperature was also monitored in the arterial outlet of the membrane oxygenator. A calibrated recorder continuously and simultaneously recorded all temperatures. Study I found large temperature discrepancies between the JB and all other body sites during cooling and rewarming. There was considerable interindividual variability in the degree of discrepancy between the JB and other sites. Study II produced similar results but also showed that JB temperature reached equilibration with the temperature of blood entering the patient via the arterial outlet of the membrane oxygenator after cooling for 3.3 +/- 1.3 min and after rewarming for 16.5 +/- 5.5 min. Analysis of variance revealed that this arterial outlet site had the smallest average discrepancy of all temperature sites relative to the JB site (P < 0.001). In summary, temperatures measured in body sites over-estimated JB temperature during cooling and under-estimated it during rewarming, whereas arterial outlet blood temperature provided a good approximation.

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

Neurologic complications after cardiac surgery are of growing importance for an aging surgical population. In this review, we provide a critical appraisal of the impact of current cardiopulmonary bypass (CPB) management strategies on neurologic complications. Other than the use of 20-40 microm arterial line filters and membrane oxygenators, newer modifications of the basic CPB apparatus or the use of specialized equipment or procedures (including hypothermia and "tight" glucose control) have unproven benefit on neurologic outcomes. Epiaortic ultrasound can be considered for ascending aorta manipulations to avoid atheroma, although available clinical trials assessing this maneuver are limited. Current approaches for managing flow, arterial blood pressure, and pH during CPB are supported by data from clinical investigations, but these studies included few elderly or high-risk patients and predated many other contemporary practices. Although there are promising data on the benefits of some drugs blocking excitatory amino acid signaling pathways and inflammation, there are currently no drugs that can be recommended for neuroprotection during CPB. Together, the reviewed data highlight the deficiencies of the current knowledge base that physicians are dependent on to guide patient care during CPB. Multicenter clinical trials assessing measures to reduce the frequency of neurologic complications are needed to develop evidence-based strategies to avoid increasing patient morbidity and mortality.

Neural correlates of cognitive dysfunction after cardiac surgery

Patients who underwent cardiac surgery and their relatives often complain on postoperative memory impairment. Most prospective neuropsychological studies also found postoperative cognitive decline early after surgery. Nevertheless, recently several reports questioned the existence of long-term brain alterations in these patient cohorts. The present review was aimed to clear up the true cardiac surgery effects on brain and cognitive functions. The reviewed data evidence that cardiac surgery interventions induce persistent localized brain ischemic lesions along with rapidly reversing global brain swelling and decreased metabolism. A range of studies showed that left temporal region was especially prone to perioperative ischemic injury, and these findings might explain persistent verbal short-term memory decline in a considerable proportion of cardiac surgery patient cohorts. Speed/time of cognitive performance is commonly decreased early after on-pump surgery either. Nevertheless, no association between psychomotor speed slowing and intraoperative embolic load was found. The rapid recovery of the latter cognitive domain might be better explained by surgery related acute global brain metabolism changes rather than ischemic injury effects. Hence, analyses of performance on separate cognitive tests rather than summarized cognitive indexes are strongly recommended for future neuropsychological studies of cardiac surgery outcomes.

Pressure ulcer risk factors in cardiac surgery: A review of the research literature

BACKGROUND

Pressure ulcer incidence in patients undergoing cardiac surgery is reported to be up to 29.5%. Common known risk factors for pressure ulcer development include compressive and shearing forces. However, knowledge about the specific risk factors in a defined population is helpful in the development of an effective prevention management. This literature review is part of a quality improvement project to reduce pressure ulcer incidence in the cardiac surgery population.

OBJECTIVES

The objective is to determine "which specific risk factors for pressure ulcer development in the cardiac surgery population are identified in the literature."

RESULTS

The results of this literature review indicate a high-risk potential in the tissue tolerance for oxygen as temperature manipulation, vasoactive drugs, hypotensive periods, and reduced hemoglobin and hematocrit levels. Time on the operating room table, frequency of repositioning, immobility time, older age, low albumin level, and corticosteroid are also found as significant risk factors in this population.

CONCLUSION

Diseases that influence oxygen supply in older patients in combination with the special demands of temperature and circulation regulation during the cardiac surgical procedure place the patient at risk for pressure ulcer development. Prevention measures should be aimed at supporting tissue tolerance for pressure and tissue tolerance for oxygen. These measures should be additional to pressure-relieving devices on the operating room table and, postoperatively in bed, a defined minimum frequency of postoperative turning and early mobilization after the surgical procedure should be considered.