Improvement of outcomes after coronary artery bypass. A randomized trial comparing intraoperative high versus low mean arterial pressure

The association of lowest hematocrit during cardiopulmonary bypass with acute renal injury after coronary artery bypass surgery

BACKGROUND

Acute renal injury is a common serious complication of cardiac surgery. Moderate hemodilution is thought to reduce the risk of kidney injury but the current practice of extreme hemodilution (target hematocrit 22% to 24%) during cardiopulmonary bypass (CPB) has been linked to adverse outcomes after cardiac surgery. Therefore we tested the hypothesis that lowest hematocrit during CPB is independently associated with acute renal injury after cardiac surgery.

METHODS

Demographic, perioperative, and laboratory data were gathered for 1,404 primary elective coronary bypass surgery patients. Preoperative and daily postoperative creatinine values were measured until hospital discharge per institutional protocol. Stepwise multivariable linear regression analysis was performed to determine whether lowest hematocrit during CPB was independently associated with peak fractional change in creatinine (defined as the difference between the preoperative and peak postoperative creatinine represented as a percentage of the preoperative value). A p value of less than 0.05 was considered significant.

RESULTS

Multivariable analyses including preoperative hematocrit and other perioperative variables revealed that lowest hematocrit during CPB demonstrated a significant interaction with body weight and was highly associated with peak fractional change in serum creatinine (parameter estimate [PE] = 4.5; p = 0.008) and also with highest postoperative creatinine value (PE = 0.06; p = 0.004). Although other renal risk factors were significant covariates in both models, TM50 (an index of hypotension during CPB) was notably absent.

CONCLUSIONS

These results add to concerns that current CPB management guidelines accepting extreme hemodilution may contribute to postoperative acute renal and other organ injury after cardiac surgery.

Perioperative stroke: evaluation, management, and possible preventive measures

Mechanisms of perioperative ischemic stroke include: hypotension, hypercoagulability, arrhythmias with embolism, or direct vascular insult. Mechanisms of perioperative hemorrhagic stroke include: use of antithrombotics, hypertension, or direct vascular insult.

Outcomes of cardiac surgery in nonagenarians: a 10-year experience

BACKGROUND

With an increasing awareness of health issues and greater emphasis on preventive medicine, the general population is living longer and healthier lives than ever before. Physicians are taking care of older patients, many of whom may require cardiac surgical procedures. Improving cardiopulmonary bypass technology allows for safer procedures with reduced morbidity and mortality even in older patients.

METHODS

We have performed a retrospective analysis of 42 consecutive nonagenarian patients who underwent open-heart procedures over a 10-year period (1993 to 2002) at our institution. Their demographic profiles, operative data, perioperative results, and long-term outcomes were recorded and analyzed.

RESULTS

Twenty-two women and 20 men with an age range of 90 to 97 years (mean, 91.4 years) had open-heart surgery over the study period. The complication rate was 67% overall, consisting of 7% respiratory (pneumonia, respiratory failure, reintubation), 7% hemorrhagic or embolic (postoperative bleeding, cerebral vascular accident), 12% infectious (wound infection, sepsis), and 31% new arrhythmia (atrial fibrillation, atrial flutter, ventricular tachycardia, ventricular fibrillation). Despite these complication rates, average hospital stay was 17.5 days (median, 11 days), with an intensive care unit stay of 12.0 days (median, 5 days). Thirty-day survival was 95% and survival to discharge was 93% (three deaths total; one cardiac arrest at hospital day 134 and two perioperative deaths; one ventricular arrhythmia, one cerebral vascular accident). The only statistically significant risk factor of mortality was emergency surgery. Currently, 81% are still alive an average of 2.53 years since surgery (range, 0.16 to 7.1 years).

CONCLUSIONS

With improving techniques and greater attention to detail, the select nonagenarian can safely undergo cardiac surgery.

Neurologic outcomes after coronary artery bypass grafting with and without cardiopulmonary bypass

Neurologic injury, in the form of either stroke or more subtle neurocognitive impairment, is a frequent and potentially devastating complication of coronary artery bypass grafting (CABG). The etiology of CABG-associated neurologic injury is likely multifactorial, with the phenomena of cerebral hypoperfusion and embolism being the major contributors. Several perioperative strategies have been developed in an effort to reduce the incidence of CABG-associated neurologic complications. Hypothermic cerebral perfusion, alpha stat acid-base management, and slow patient rewarming have been shown by several investigators to minimize adverse neurologic sequelae associated with the use of cardiopulmonary bypass. Performing CABG without cardiopulmonary bypass (off-pump CABG), meanwhile, has been shown to reduce the risk of perioperative stroke, especially in high-risk patients such as the elderly. Whether off-pump CABG reduces the incidence of less severe neurocognitive impairment has not yet been clearly established and merits further investigation in the form of large, multicenter, randomized trials. Other technical innovations, such as the use of sutureless and clampless aortic anastomotic devices, also may be able to further minimize the neurologic complications associated with CABG.

Best Practice for Cardiopulmonary Bypass in the High-Risk Elderly Patient

The management of cardiopulmonary bypass has evolved over the last 50 years resulting in a largely consistent approach to both adult and pediatric perfusion. Very little has been written or prospectively researched on the best practice for cardiopulmonary bypass in the high-risk elderly patient, despite the challenge this patient cohort presents compared to the general adult population and the rapidly increasing number of such patients undergoing cardiac surgery. We propose a framework for perfusion strategies for the high-risk elderly patient from our current understanding of cardiopulmonary bypass. It should stimulate discussion for a consensus on perfusion strategies for the elderly and encourage further research into perfusion variables as they relate to the outcome of patients of advanced age.

Risk factor analysis of early and delayed cerebral complications after cardiac surgery

OBJECTIVE

To report the incidence, severity, and possible risk factors for early and delayed cerebral complications.

DESIGN

Retrospective study.

SETTING

Linköping University Hospital, Sweden.

PARTICIPANTS

Consecutive patients who underwent cardiac surgery in the period July 1996 through June 2000 (n = 3,282).

INTERVENTIONS

A standard cardiopulmonary bypass (CPB) technique was used for most patients. Postoperative anticoagulant treatment included heparin or anti-Xa dalteparin. Patients undergoing coronary artery bypass graft surgery received acetylsalicylic acid, and patients undergoing valve surgery received warfarin.

MEASUREMENTS AND MAIN RESULTS

Cerebral complications occurred in 107 patients (3.3%). Of these, 60 (1.8%) were early, and 33 (1.0%) were delayed, and in 14 (0.4%) patients the onset was unknown. There were 37 variables in univariate analysis (p < 0.15) and 14 variables in multivariate analysis (p < 0.05) associated with cerebral complications. Predictors of early cerebral complications were older age, preoperative hypertension, aortic aneurysm surgery, prolonged CPB time, hypotension at CPB completion and soon after CPB, and postoperative arrhythmia and supraventricular tachyarrhythmia. Predictors of delayed cerebral complications were female gender, diabetes, previous cerebrovascular disease, combined valve surgery and coronary artery bypass graft surgery, postoperative supraventricular tachyarrhythmia, and prolonged ventilator support. Early cerebral complications seem to be more serious, with more permanent deficits and a higher overall mortality (35.0% v 18.2%).

CONCLUSION

Most cerebral complications had an early onset. The results of this study suggest that aggressive antiarrhythmic treatment and blood pressure control may imfurther prove the cerebral outcome after cardiac surgery.

Isolated systolic hypertension is associated with adverse outcomes from coronary artery bypass grafting surgery

Isolated systolic blood pressure has not been sufficiently studied in the perioperative setting and may contribute to morbidity and mortality after coronary artery bypass grafting (CABG) surgery. Our objective was to determine the prevalence of isolated systolic hypertension among patients who had CABG surgery and to assess whether isolated systolic hypertension is associated with perioperative and postoperative in-hospital morbidity or mortality. Patients who underwent CABG were selected from a prospective epidemiological study involving 2417 patients in 24 medical centers. Patients were classified as having normal preoperative blood pressure, isolated systolic hypertension (systolic blood pressure >140 mm Hg), diastolic hypertension (diastolic blood pressure >90 mm Hg), or a combination of these. Demographic risk factors (age, sex, and ethnicity), clinical risk factors (diabetes mellitus, increased cholesterol, antihypertensive medications, history of congestive heart failure, myocardial infarction, hypertension, and neurological deficits), and behavioral risk factors (smoking and heavy drinking) were controlled for statistically. Adverse outcomes included left ventricular dysfunction, cerebral vascular dysfunction or events, renal insufficiency or failure, and all-cause mortality. Isolated systolic hypertension was found in 29.6% of patients. Unadjusted isolated systolic hypertension was associated with a 40% increased risk of adverse outcomes (odds ratio, 1.4; confidence interval, 1.1-1.7). After adjusting for other potential risk factors, the increased risk of adverse outcomes with isolated systolic hypertension was 30%. We conclude that isolated systolic hypertension is associated with a 40% increase in the likelihood of cardiovascular morbidity perioperatively in CABG patients. This increase remains present regardless of antihypertensive medications, anesthetic techniques, and other perioperative cardiovascular risk factors (e.g., age older than 60 yr or history of congestive heart failure, myocardial infarction, or diabetes).

IMPLICATIONS

Isolated systolic hypertension is associated with a 40% increase in the likelihood of perioperative cardiovascular morbidity in coronary artery surgery patients.

Neuroprotection During CPB: From Mechanisms to Interventions

The incidence and etiology of brain dysfunction after conventional coronary artery bypass surgery using cardiopulmonary bypass are reviewed. Stroke rates and incidences of cognitive dysfunction from various studies are considered. Mechanisms of injury including cerebral embolization as detected by transcranial Doppler and evidence for postoperative cerebral edema are discussed. Evidence for lower overall postoperative morbidity, and for a lower incidence of cognitive dysfunction specifically, after nonpump coronary revascularization is presented.

Prostaglandin synthesis inhibitor improves hypotension during normothermic cardiopulmonary bypass

Hypotension is a major systemic side effect during cardiopu monary bypass (CPB), especially at normothermia. We previously reported that prostaglandin (PG) might play a substantial role in hypotension. The purpose of this study was to clarify whether a PG synthesis inhibitor (PGSI) could improve hypotension during CPB. Thirty-six patients undergoing cardiac surgery with normothermic CPB (35-37 degrees C) were divided into two groups: a PGSI group (n = 18), whose members wer given a PGSI before and during CPB, and a control group (n = 18). In both groups, perfusion flow was sufficient and pressure was maintained at above 45 mm Hg by infusion of metaraminol, a vasoconstrictor. The mean arterial pressure throughout CPB was significantly higher in the PGSI group than in the control group (57 +/- 4 vs. 48 +/- 3 mm Hg, p < 0.01), whereas the dose of infused metaraminol was significantly lower in the PGSI group (13 +/- 7 vs. 21 +/- 6 mg, p < 0.01). The blood base excess was not significantly different (1.0 +/- 1.6 vs. 1.7 +/- 1.9 mmol/L, p = 0.28), and urine output was significantly higher in the PGSI group (503 +/- 179 vs. 354 +/- 112 ml/hr, p < 0.01). In conclusion, PGSI can improve hypotension during CPB and increase urine output without impairing peripheral circulation.

Effect of apolipoprotein E genotype on cerebral autoregulation during cardiopulmonary bypass

BACKGROUND AND PURPOSE

The presence of the apolipoprotein E epsilon4 (apoE4) allele has been associated with cognitive decline after cardiac surgery. We compared autoregulation of cerebral blood flow (CBF), cerebral metabolic rate for oxygen (CMRO(2)), and arterial-venous oxygen content difference [C(A-V)O(2)], during cardiopulmonary bypass (CPB) in patients with and without the apoE4 allele to help define the mechanism of association with cognitive decline.

METHODS

One hundred fifty-four patients underwent coronary artery bypass grafting with CPB, nonpulsatile flow, and alpha-stat management. CBF was measured by using (133)Xe washout methods. C(A-V)O(2), CMRO(2), and oxygen delivery were calculated. Pressure-flow autoregulation was tested by using 2 CBF measurements at stable hypothermia: the first at stable mean arterial pressure (MAP) and the second 15 minutes later, when MAP had increased or decreased >/=20%. Metabolism-flow autoregulation was tested by varying the temperature and measuring the coupling of CBF and CMRO(2).

RESULTS

In patients with (n=41) or without (n=113) the apoE4 allele, there were no differences in CBF, CMRO(2), C(A-V)O(2), pressure-flow and metabolism-flow autoregulation corrected for age, gender, non-insulin-dependent diabetes, hemoglobin, CPB time, and temperature.

CONCLUSIONS

We conclude that apoE genotype does not affect global CBF and oxygen delivery/extraction during CPB, which suggests that other mechanisms are responsible for the apoE isoform-related neurocognitive dysfunction seen in patients undergoing CPB.

An extracorporeal membrane oxygenation-based approach to cardiogenic shock in an older population

BACKGROUND

We investigated the efficacy of an integrated system of advanced supportive care based on extracorporeal membrane oxygenation (ECMO) in older patients with an estimated mortality of more than 90% to establish whether its use is justifiable.

METHODS

Treatment was provided by cardiac surgeons and critical care physicians and included the following key elements: (1) ECMO, (2) early application of continuous venovenous hemofiltration, (3) inhaled nitric oxide, (4) maintenance of perfusion pressure with norepinephrine, (5) maintenance of pulmonary blood flow by ventricular filling with intravenous colloids, (6) avoidance of early postoperative anticoagulation, (7) frequent use of transesophageal echocardiography, and (8) low tidal volume ventilation. Demographic features, intraoperative details, postoperative course, ECMO weaning rate, morbidity, survival to hospital discharge, and the quality of life of survivors were recorded.

RESULTS

Seventeen consecutive patients (median age, 69 years) with refractory cardiogenic shock were studied. The median duration of ECMO was 86 hours (20 to 201 hours). Eleven patients (65%) were successfully weaned from ECMO. Seven patients (41%) survived to discharge. The major causes of morbidity were bleeding and leg ischemia. All patients who survived to discharge were alive and well at follow-up (median, 21 months) and reported a satisfactory quality of life.

CONCLUSIONS

An ECMO-based approach can be used with acceptable results in the treatment of refractory cardiogenic shock, even in older patients.

Beating heart surgery or conventional CABG: are neurologic outcomes different?

Although there has been much debate about the causes of neurologic complications associated with coronary artery bypass grafting (CABG), there is good evidence linking such complications with some of the pathophysiologic changes associated with use of conventional cardiopulmonary bypass (CPB). Several studies indicate that it is possible to significantly lower risk of stroke and other central nervous system (CNS) morbidity in patients undergoing CPB for CABG by application of selected techniques and equipment modifications. The resurgence of interest in coronary revascularization by using beating heart surgery (BHS) offers a unique opportunity to evaluate neurologic outcome independent of CPB. Currently, BHS would appear to significantly reduce morbidity in the elderly and to decrease the costs and resource use in coronary revascularization patients. It is hoped that by understanding the mechanisms of CNS injury associated with CABG, techniques can be developed to decrease the risk of neurologic injury associated with coronary revascularization, whether or not CPB is used. Definitive conclusions regarding outcomes after best practice CPB or BHS await large-scale, risk-stratisfied multicenter trials.

Importance of blood pressure regulation in maintaining adequate tissue perfusion during cardiopulmonary bypass

Patients undergoing surgery with the aid of cardiopulmonary bypass (CPB) have an incidence of end-organ dysfunction, caused by embolization, regional hypoperfusion, or some combination of the two. In this article, we attempt to define the effect of mean arterial pressure (MAP) during CPB on postoperative end-organ function. Although early studies reported that cerebral perfusion during hypothermic CPB is independent of MAP, recent laboratory and clinical reports have shown a positive slope in the MAP versus cerebral blood flow relationship. In clinical studies, patients who had higher MAPs during CPB had a lower incidence of cardiac and neurologic complications, as well as late neurocognitive abnormalities compared with patients with lower MAPs. Improving collateral flow in the setting of cerebral embolization has been postulated as the main mechanism for the improved neurologic outcomes in the high MAP groups. Higher perfusion pressure during CPB affects regional blood flow to the kidneys and visceral organs. However, the lower autoregulatory limits of perfusion to abdominal organs differ from the limits to the brain. Enhanced visceral perfusion during CPB is best achieved by increasing perfusion pressure via increases in perfusion flow rates rather than by using peripheral vasoconstriction alone. In conclusion, it is clear that maintenance of a high MAP during CPB may have a significant impact in protecting the brain and abdominal organs, particularly in the subset of patients at high risk for embolization and end-organ dysfunction.

Management of patients with concomitant coronary and carotid vascular disease

Stroke is a major complication of coronary artery bypass graft (CABG) surgery. Carotid stenosis is an important cause of stroke in certain CABG patients. Randomized trials have revealed that carotid endarterectomy (CEA) is clearly indicated in non-CABG patients with symptomatic severe carotid stenosis. CEA is also indicated in patients with symptomatic moderate stenosis and asymptomatic severe stenosis if the predicted incidence of perioperative morbidity and mortality is low. Therapeutic options for patients with concomitant coronary and carotid disease include CABG alone, CABG plus CEA, and CABG plus carotid stenting. In this article we discuss each of these management techniques in detail, and make recommendations regarding the preferred approach in specific patient populations.

Hypothermia to reduce neurological damage following coronary artery bypass surgery

BACKGROUND

Coronary artery bypass surgery (CABG) may be life saving, but known side effects include neurological damage and cognitive impairment. The temperature used during cardiopulmonary bypass (CPB) may be important with regard to these adverse outcomes, where hypothermia is used as a means of neuroprotection.

OBJECTIVES

To assess the effectiveness of hypothermia during CABG in reducing neurological damage and subsequent cognitive deficits.

SEARCH STRATEGY

The Cochrane Controlled Trials Register was searched for randomised controlled trials (RCT) and this was updated by searching MEDLINE and EMBASE to December 1999 using database specific RCT filters. Reference lists of retrieved articles were searched and experts in the field were contacted.

SELECTION CRITERIA

Only RCTs were considered. All patients undergoing CABG, either first time or revisions, elective or emergency procedures, were included. Any hypothermia protocol was considered. Only trials reporting neurological outcomes were included.

DATA COLLECTION AND ANALYSIS

Studies were selected independently and data were extracted from the source papers independently by two reviewers. Authors were contacted for further information. Studies were combined with meta-analysis where appropriate, and meta-regression was used to explore heterogeneity.

MAIN RESULTS

There was a trend towards a reduction in the incidence of non fatal strokes in the hypothermic group (OR 0.68 (0.43, 1.05)). Conversely, there was a trend for the number of non stroke related perioperative deaths to be higher in the hypothermic group (OR 1.46 (0.9, 2.37)). Hypothermia had no effect on the incidence of non fatal myocardial infarction (OR 1.05 (0.81, 1.37)), but the incidence of another marker of myocardial damage, low output syndrome, was higher in the hypothermic group (OR 1.21 (0.99, 1.48). When pooling all "bad" outcomes (stroke, perioperative death, myocardial infarction, low output syndrome, intra aortic balloon pump use) there was no significant advantage of either hypothermia or normothermia (OR 1.07 (0.92, 1.24)). Only 4 of 17 trials reported neuropsychological function as an outcome.

REVIEWER'S CONCLUSIONS

This review could find no definite advantage of hypothermia over normothermia in the incidence of clinical events. Hypothermia was associated with a reduced stroke rate, but this is off set by a trend towards an increase in non stroke related perioperative mortality and myocardial damage. There is insufficient data to date to draw any conclusions about the use of mild hypothermia. Similarly, there is insufficient data to date to comment on the effect of temperature during CPB on subtle neurological deficits, and further trials are needed in these areas.

Carotid and aortic screening for coronary artery bypass grafting

BACKGROUND

To identify risk factors for preexisting carotid and aortic disease in coronary artery bypass grafting (CABG), preoperative parameters were analyzed.

METHODS

Three-hundred eight consecutive patients undergoing elective isolated CABG were investigated through preoperative duplex scanning of the carotid artery, computed tomography of the chest, and intraoperative ultrasonography of the ascending aorta.

RESULTS

Prevalence of carotid stenosis and ascending aortic atherosclerosis was 14.3% (44 of 308) and 30.2% (93 of 308), respectively. Multivariate analysis indicated that significant independent risk factors for carotid stenosis were atherosclerosis of the ascending aorta (p = 0.028, odds ratio [OR] = 2.16), peripheral vascular disease (p = 0.008, OR = 4.08), and history of stroke (p = 0.0004, OR = 3.73). Significant independent risk factors for ascending aortic atherosclerosis were peripheral vascular disease (p = 0.029, OR = 3.05), age older than 60 years (p = 0.009, OR = 2.94), and carotid stenosis (p = 0.018, OR = 2.27). Modifications on the operative procedure for aortic atherosclerosis were carried out in 49 patients. Overall hospital mortality and morbidity for stroke were 0.97% and 0.65%, respectively.

CONCLUSIONS

Prevalence of carotid and aortic disease was not low among candidates for CABG. Carotid and aortic screening may help to modify the operative strategy to reduce morbidity of stroke.

Stroke after coronary artery bypass grafting in patients with cerebrovascular disease

BACKGROUND

Stroke has been associated with a significantly increased mortality from coronary artery bypass grafting (CABG). To determine the predictors of stroke in patients undergoing CABG, we collected data on 472 consecutive patients.

METHODS

From March 1991 to March 1999, all patients undergoing CABG at our institution underwent routine duplex scanning of the extracranial carotid and vertebral arteries. Seven patients with symptomatic carotid stenosis were treated by carotid endarterectomy (CEA) before CABG.

RESULTS

There was a 10-fold increase in mortality (12.5%) associated with postoperative stroke. Many variables were analyzed by a multivariate technique and the severity of extracranial carotid artery stenosis was determined to be the only independent predictor of postoperative stroke (p < 0.01). None of the patients with carotid artery occlusion and none of the patients who underwent CEA before CABG experienced a stroke.

CONCLUSIONS

To reduce the stroke rate, the indications for prophylactic CEA may be extended for asymptomatic patients with carotid artery stenosis greater than 75%.

Neurocognitive dysfunction after coronary artery bypass surgery: a systematic review

OBJECTIVE

Substantial, albeit scattered, evidence suggests that coronary artery bypass grafting may impair cognitive function. As methods and definitions differ greatly across studies, the reported incidence of cognitive decline after coronary bypass surgery varies widely as well. The aim of the present study was to systematically review those studies on cognitive decline that are relatively comparable and meet with certain quality criteria.

METHODS

Four electronic databases and the references of several abstract books and earlier reviews were used to identify relevant literature. Stringent criteria, based in part on the 1994 consensus meeting on assessment of neurobehavioral outcomes after cardiac surgery, were used to assess the studies that were found. In total, 256 different titles were found, of which 23 met with the formulated selection criteria.

RESULTS

Twelve cohort studies and eleven intervention studies were evaluated. A pooled analysis of six highly comparable studies yielded a proportion of 22.5% (95% confidence interval, 18.7%-26.4%) of patients with a cognitive deficit (a decrease of at least 1 standard deviation in at least two of nine or ten tests) 2 months after the operation.

CONCLUSIONS

Neurocognitive dysfunction is a frequently occurring complication of coronary artery bypass grafting. The etiologic contribution of cardiopulmonary bypass to this complication will remain unclear until a randomized trial that directly compares off-pump and on-pump bypass surgery is carried out.

Central Nervous System Complications in Cardiac Surgery: Retrograde Cerebral Perfusion, Pressure, Pulsatility, Temperature, and pH Management During Cardiopulmonary Bypass

Currently, clinical management strategies during cardio pulmonary bypass (CPB) are undergoing profound changes. Renewed interest in normothermic versus hypothermic perfusion during CPB has resulted in appar ently contradictory results regarding patient outcomes. Much effort has been devoted to defining physiological responses of the brain to various alterations during CPB (eg, pH strategy, normothermia versus hypothermia, pulsatile or nonpulsatile perfusion, use of arterial line filtration, circulatory arrest, retrograde cerebral perfu sion). In addition, prospective studies are examining the impact of diverse strategies on neuropsychological and neurological outcomes after CPB, to define optimal management techniques.

Intraoperative physiologic variables and outcome in cardiac surgery: Part I. In-hospital mortality

BACKGROUND

Risk stratification schemes have been developed to predict outcome of coronary artery bypass grafting (CABG) procedures, which are predominately based upon unalterable preoperative patient characteristics. The purpose of this study was to determine if minimum intraoperative hematocrit, maximum glucose concentration, mean arterial pressure on cardiopulmonary bypass, or duration of bypass influence risk-adjusted in-hospital mortality after CABG.

METHODS

Outcome data from 2,862 CABG patients were merged with intraoperative physiologic data. A preoperative mortality risk index was calculated for each patient. Variables found significant (p<0.05) by univariate logistic regression were tested in a multiple variable model to determine risk-adjusted association with mortality.

RESULTS

Overall mortality rate was 1.85%. The preoperative risk index was significantly associated with mortality (p = 0.0001). No significant association was present between mortality and intraoperative variables. Preexisting hypertension was an independent predictor of mortality after controlling for risk index and bypass duration.

CONCLUSIONS

Preexisting hypertension proved to be an independent predictor of mortality in our patient population. This study found no evidence to support the hypothesis that mean arterial pressure less than 50 mm Hg, lower hematocrit, or elevated glucose while on bypass increases in-hospital mortality.

Intraoperative physiologic variables and outcome in cardiac surgery: Part II. Neurologic outcome

BACKGROUND

The impact of alterable physiologic variables on neurologic outcome after coronary artery bypass grafting procedures is unknown. The purpose of this study was to determine whether minimum intraoperative hematocrit, maximum glucose concentration, or mean arterial pressure during cardiopulmonary bypass influences risk-adjusted neurologic outcome after coronary artery bypass grafting.

METHODS

Outcome data from 2,862 patients undergoing coronary artery bypass grafting were merged with intraoperative physiologic data. A preoperative stroke risk index was calculated for each patient. Variables found significant by univariate logistic regression were tested in a multivariable model to determine association with outcome.

RESULTS

The incidence of stroke or coma in the study population was 1.3%. After controlling for stroke risk and bypass time, only an index of low mean arterial pressure during bypass retained a significant inverse association with outcome (p = 0.0304).

CONCLUSIONS

This study found no evidence that glucose concentration or minimum hematocrit are associated with major adverse neurologic outcome. The association between lower pressure during bypass and decreased incidence of stroke or coma persisted in all risk groups. This points to mechanisms other than hypoperfusion as the primary cause of neurologic injury associated with cardiac surgery.

Neuroprotective "agents" in surgery. Secret "agent" man, or common "agent" machine?

The search for clinically-effective neuroprotective agents has received enormous support in recent years--an estimated $200 million by pharmaceutical companies on clinical trials for traumatic brain injury alone. At the same time, the pathophysiology of brain injury has proved increasingly complex, rendering the likelihood of a single agent "magic bullet" even more remote. On the other hand, great progress continues with technology that makes surgery less invasive and less risky. One example is the application of endovascular techniques to treat coronary artery stenosis, where both the invasiveness of sternotomy and the significant neurological complication rate (due to microemboli showering the cerebral vasculature) can be eliminated. In this paper we review aspects of intraoperative neuroprotection both present and future. Explanations for the slow progress on pharmacologic neuroprotection during surgery are presented. Examples of technical advances that have had great impact on neuroprotection during surgery are given both from coronary artery stenosis surgery and from surgery for Parkinson's disease. To date, the progress in neuroprotection resulting from such technical advances is an order of magnitude greater than that resulting from pharmacologic agents used during surgery. The progress over the last 20 years in guidance during surgery (CT and MRI image-guidance) and in surgical access (endoscopic and endovascular techniques) will soon be complemented by advances in our ability to evaluate biological tissue intraoperatively in real-time. As an example of such technology, the NASA Smart Probe project is considered. In the long run (i.e., in 10 years or more), pharmacologic "agents" aimed at the complex pathophysiology of nervous system injury in man will be the key to true intraoperative neuroprotection. In the near term, however, it is more likely that mundane "agents" based on computers, microsensors, and microeffectors will be the major impetus to improved intraoperative neuroprotection.

Particulate emboli capture by an intra-aortic filter device during cardiac surgery

OBJECTIVE

Particulate embolization is associated with neurologic morbidity after cardiac surgery. Crossclamp manipulation has been identified as the single most significant cause of particulate emboli release during cardiac surgery. A new intra-aortic filtration method has been assessed with regard to its safety and its ability to capture particulate emboli before they enter the central circulation.

METHODS

Patients undergoing cardiac surgery with cardiopulmonary bypass through standard median sternotomy were selected for emboli management by means of intra-aortic filtration. A novel intra-aortic filter device was inserted through a modified 24F arterial cannula immediately before releasing the crossclamp in 77 patients. Filters remained in the aorta until cardiopulmonary bypass was discontinued and the heart was fully ejecting. The procedure was assessed for facility, safety, and effect on routine cardiopulmonary bypass operation and function.

RESULTS

The insertion and removal of the intra-aortic filter were safe, easy, and uneventful in most patients. Patient hemodynamics and bypass flow rates remained normal throughout the filter dwell period. No strokes or gross neurologic defects were noted. Electron microscopic analysis of 12 filters revealed an insignificant degree of platelet adhesion on filter surfaces. Histology samples (n = 44) were examined, and 66% (n = 29) showed evidence of atheromatous material, 36% (n = 16) with platelet-fibrin, 25% (n = 11) with true thrombus and/or blood clot, 7% (n = 3) with normal vessel wall, and 2% (n = 1) with aggregates of cholesterol or grumous portion of atheromatous plaque.

CONCLUSION

The intra-aortic filter can be safely deployed and captures particulate emboli, the predominant origin of which is atheromatous. The beneficial effects of this device on neurologic outcomes have yet to be determined.

Predictors and outcomes of cardiac complications following elective coronary bypass grafting

Our objective was to determine the predictors of cardiac complications among a cohort of elective coronary artery bypass graft (CABG) surgery patients and to determine the relationship of such complications to subsequent quality of life and symptoms. A total of 248 patients were enrolled and 237 completed 6 month follow-up. The combined rate of both major and minor cardiac complications was 9.7% (n = 24). Patients in this study were evaluated preoperatively, monitored intraoperatively, followed immediately postoperatively and at 6 months. Major cardiac complications accounted for 3.6% (n = 9) and minor complications for 6% (n = 15). Using multivariable logistic regression analysis, the predictors of major cardiac complications were receiving diuretics preoperatively (p = .01) and increased time during cross-clamping (p = .006). At 6 months after surgery, 19% of the patients with postoperative cardiac complications experienced worsening of symptoms, in contrast to only 8% of those without cardiac complications (p = .03). We concluded that patients who were on preoperative diuretics and those who had longer cross-clamp times were at higher risk of cardiac complications. The majority of patients who had acute cardiac complications had improved function and symptoms at 6 months postoperatively.

Intraoperative hemodynamic predictors of mortality, stroke, and myocardial infarction after coronary artery bypass surgery

Evidence that intraoperative hemodynamic abnormalities influence outcome is limited. The purpose of this study was to determine whether intraoperative hemodynamic abnormalities were associated with mortality, stroke, or perioperative myocardial infarction (PMI) in a large cohort of patients undergoing coronary artery bypass grafting. Risk factors and outcomes were queried from a state-mandated cardiac surgery reporting system at two hospitals in New York, NY. Intraoperative hemodynamic abnormalities were derived from computerized anesthesia records by assessing the duration of exposure to moderate or severe extremes of hemodynamic variables. Multivariate logistic regression identified independent predictors of perioperative mortality, stroke, and PMI. Among 2149 patients, there were 50 mortalities, 51 strokes, and 85 PMIs. In the precardiopulmonary bypass (pre-CPB) period, pulmonary hypertension was a predictor of mortality (odds ratio [OR] 2.1, P = 0.029), and bradycardia and tachycardia were predictors of PMI (OR 2.9, P = 0.007 and OR 2.0, P = 0.028, respectively). During CPB, hypotension was a predictor of mortality (OR 1.3, P = 0.025). Post-CPB, tachycardia was a predictor of mortality (OR 3.1, P = 0.001), diastolic arterial hypertension was a predictor of stroke (OR 5.4, P = 0.012), and pulmonary hypertension was a predictor of PMI (OR 7.0, P < 0.001). Increased pulmonary arterial diastolic pressure post-CPB was a predictor of mortality (OR 1.2, P = 0.004), stroke (OR 3.9, P = 0.002), and PMI (OR 2.2, P = 0.001). Rapid intraoperative variations in blood pressure and heart rate were not independent predictors of these outcomes. These findings demonstrate the prognostic significance of intraoperative hemodynamic abnormalities, including data from pulmonary artery catheterization, to adverse postoperative outcomes. It is not known whether interventions to control these variables would improve outcome.

IMPLICATIONS

Intraoperative hemodynamic abnormalities, including pulmonary hypertension, hypotension during cardiopulmonary bypass, and postcardiopulmonary bypass pulmonary diastolic hypertension, were independently associated with mortality, stroke, and perioperative myocardial infarction over and above the effects of other preoperative risk factors.

Improved cerebral perfusion after stenting of a petrous carotid stenosis: technical case report

OBJECTIVE AND IMPORTANCE

Atherosclerotic occlusive disease of the intracranial vasculature is associated with increased risk of systemic vascular occlusive disease and stroke. Therapeutic options have included anticoagulation therapy, antiplatelet therapy, or, in a limited number of patients, extracranial-intracranial vascular bypass procedures. We report a patient who had improved cerebral perfusion with silent watershed zone infarctions after endovascular stenting of a severe petrous segment carotid stenosis.

CLINICAL PRESENTATION

A 73-year-old man with severe coronary artery disease and unstable angina was referred for treatment of a 90% right petrous carotid artery stenosis before coronary artery bypass grafting. A brain single-photon emission computed tomographic scan using 99mTc-bicisate revealed diminished perfusion throughout the right internal carotid artery territory, particularly in posterior watershed zones.

TECHNIQUE

The patient underwent transfemoral placement of a 7-French introducer sheath, followed by a 7-French guide catheter. Urokinase (225,000 U) was infused through a microcatheter placed proximal to the lesion. No changes were noted in lesion morphology after this infusion. A microguidewire was navigated across the lesion. Subsequent balloon angioplasty with a coronary artery balloon was performed twice, followed by placement of a 4- x 12-mm coronary stent.

CONCLUSION

Selective internal carotid artery angiography after stenting revealed markedly improved flow. A brain 99mTc-bicisate single-photon emission computed tomographic scan performed within 24 hours of stent placement, revealed significantly improved perfusion within the right internal carotid artery territory. Two perfusion voids suggestive of embolic stroke were noted; both were clinically silent. The patient had uncomplicated coronary artery bypass grafting 72 hours later. Five months postoperatively, he remains at home, living independently and with intact neurological function. Intracranial stenting for severe atherosclerotic stenosis is technically possible. However, its ultimate clinical role remains to be determined.

Depressive symptomatology in coronary artery bypass graft surgery patients

Depression is commonly reported in coronary artery bypass graft (CABG) surgery patients. This study assesses the relationship of preoperative characteristics, life stressors, social support, major cardiac and neurologic outcomes and other complications to depressive symptomatology. Demographic and clinical data, CES-D score and information on life stressors and social support were collected from 237 patients; 92% completed 6-month follow-up. CES-D score > or = 16 was defined as significant depressive symptomatology. Significant depressive symptomatology was found in 43% of patients preoperatively and 23% postoperatively. In multivariate models, low social support (p = 0.008), presence of at least one life stressor within a year of surgery (p = 0.006), moderate to severe dyspnea (p = 0.003), little to no available help (p = 0.05) and less education (p = 0.05) were associated with higher preoperative CES-D score, while longer intensive care unit (ICU) stay (p = 0.0001) and little or no available help (p = 0.0008) predicted higher postoperative CES-D scores when controlling for preoperative CES-D scores. Neither pre- nor postoperative depressive symptomatology was related to major outcomes or other complications. A high rate of significant depressive symptomatology exists in CABG patients preoperatively, and it decreases significantly postoperatively. Patients with the above preoperative characteristics as well as those who stay in the ICU postoperatively for more than 2 days might benefit from psychosocial interventions.

Retinal artery air embolism in dogs: fluorescein angiographic evaluation of effects of hypotension and hemodilution

Cerebral air embolism can cause cerebral complications after open heart surgery. The duration of cerebral artery occlusion by air embolism is thought to vary depending on the conditions. However, no study has evaluated factors affecting the duration of occlusion. In this study, we examined the effects of blood pressure and hemodilution on the duration of retinal artery occlusion caused by air embolism in dogs. The duration of retinal artery occlusion caused by the injection of 0.6 mL of air into the common carotid artery was measured by fluorescein angiography and compared among the following three periods: a control period, during which the mean blood pressure (MBP) was maintained at 80 mm Hg; a hypotension period, during which MBP was decreased to 60 mm Hg by exsanguination; and a hypotension plus hemodilution period, during which an additional exchange of blood with hydroxyethyl starch solution was performed and MBP was maintained at 60 mm Hg. When MBP was lowered from 80 to 60 mm Hg, the duration of retinal artery occlusion was prolonged from 34+/-39 to 166+/-90 s (P < 0.01). In dogs with MBP of 60 mm Hg, hemodilution (12.0+/-0.9 to 7.3+/-0.5 g/dL hemoglobin concentration) shortened the duration from 166+/-90 to 75+/-50 s (P < 0.05). Our results demonstrate that hypotension prolongs and hemodilution shortens the duration of retinal artery occlusion caused by air embolism.

IMPLICATIONS

We evaluated the effects of blood pressure and hemodilution on the duration of retinal artery occlusion caused by air embolism by retinal fluorescein angiography. Hypotension prolonged and hemodilution shortened the duration of retinal artery occlusion caused by air embolism.

Cardiovascular surgery in the elderly

The elderly segment of the population is increasing rapidly, and surgeons are more frequently being requested to operate on this group of patients. A number of reports suggest that elderly patients have a significantly higher incidence of operative mortality and 30-day hospital mortality as compared with younger patients. Elderly patients also had a significantly higher increased incidence of complications, such as renal failure, prolonged ventilation, and incidence of strokes and postoperative cardiac arrest. Regarding coronary artery disease, elderly patients are more acutely sick on admission, are more likely to have triple-vessel disease, more likely have comorbid disease, and are usually less likely to receive an internal mammary artery graft. The presence of valvular disorders with concomitant coronary disease (especially mitral ischemic related valve disease) increases operative time, morbidity, and mortality. Efforts must continue to be made to gather data on outcomes of cardiac surgery in the elderly. Consideration must be given to modify the operative approach that minimizes cardiopulmonary bypass time, mitigates the multisystem organ injury associated with cardiopulmonary bypass, and decreases the likelihood of embolization from the ascending aorta. Future efforts must be made to develop measures to decrease the complications rate identified in elderly patients.

Predictors of neurological morbidity after coronary artery bypass surgery

OBJECTIVE

The aim of this study was to analyze the postoperative neurological complications after myocardial revascularization.

METHODS

We analyzed the pre-, peri- and postoperative data of 3834 patients who underwent a primary isolated bypass grafting between January 1987 and December 1995. Postoperative neurological complications (A) were divided into mild complications (B) and major complications (C).

RESULTS

The incidence of A increased, from 1.4% to 3.0%. Unifactor risk analysis identified: age > 75 years, peripheral vascular atherosclerosis, neurological pathology, aorta-pathology and perioperative myocardial infarction as risk factors for A. Perioperative myocardial infarction and neurological pathology for B; age > 75 years, peripheral vascular atherosclerosis, neurological pathology, perioperative myocardial infarction and aorta pathology for C. Multifactor risk regression analysis identified peripheral vascular atherosclerosis, neurological pathology, aorta-pathology, perioperative myocardial infarction and the time cohort 1993-1995 as independent predictors for A; perioperative myocardial infarction and the time cohort 1993-1995 for B; neurological pathology, aorta-pathology and perioperative myocardial infarction for C.

CONCLUSIONS

Peripheral vascular atherosclerosis, neurological pathology, aorta-pathology, the occurrence of a perioperative myocardial infarction and the time cohort 1993-1995 are identified as independent risk factors for neurological complications.

Risk factors for development of acute renal failure (ARF) requiring dialysis in patients undergoing cardiac surgery

Acute renal failure (ARF) is one of the major complications after cardiopulmonary bypass for open heart operations. The present study was undertaken to identify the risk factors for the development of ARF following cardiopulmonary bypass (CPB). Four hundred and forty-seven consecutive patients who underwent open heart procedures from July 1994 to June 1995 were analyzed retrospectively. Their mean age was 55.6 +/- 14.2 (SD) years (range, 18 to 80). Dialysis was instituted whenever a patient exhibited inadequate urine output (<0.5 mL/kg/hr) for 2 to 3 hours despite correction of hemodynamic status and diuretic therapy, especially if fluid overload, hyperkalemia, or metabolic acidosis were also present. Twenty variables were analyzed by univariate analysis; these included nine preoperative variables--age, sex, hypertension, atherosclerosis, diabetes mellitus, left ventricular end-diastolic dimension (LVEDD) >5 cm, preoperative congestive heart failure, renal insufficiency (serum creatinine > or =130 micromol/L on two occasions), and sepsis--10 intraoperative variables--duration of CPB, redo procedures, emergency surgery, use of intraaortic balloon pump (IABP) in operating room, use of gentamicin, use of ceftriaxone, use of sulbactam/ampicillin, requirement of deep hypothermic circulatory arrest, duration of low mean perfusion pressure (mean pressure <50 mmHg for more than 30 minutes), operation on multiple valves--and one postoperative variable--significant hypotension (systolic blood pressure less than 90 mmHg for more than 1 hour). Significant variables or the variables having a trend (p<0.1) to be associated with ARF were included in stepwise multiple logistic regression analyses. Three regression analyses were performed separately. The incidence of ARF requiring dialysis in the study period was 15.0%. Significant risk factors for whole group of patients (regression I) were preoperative renal insufficiency (p<0.0001), postoperative hypotension (p<0.0001), cardiopulmonary bypass time more than 140 min (p<0.005), preoperative congestive heart failure (p<0.01), and history of diabetes mellitus (p<0.01). The risk factors in the valve group of patients (regression II) were preoperative renal insufficiency (p<0.0001) and postoperative hypotension (p<0.05). Risk factors in the CABG patients (regression III) were postoperative hypotension (p=0.0001), CPB time more than 140 min (p<0.05), preoperative renal insufficiency (p<0.05), and age (p<0.05). The authors conclude that preoperative renal insufficiency and postoperative hypotension are the most important independent risk factors for ARF in postcardiac surgical patients. In addition, CPB time greater than 140 minutes and old age are also independent risk factors for ARF in CABG patients. CPB time more than 140 minutes, history of diabetes mellitus, and preoperative congestive heart failure are independent risk factors for development of ARF in our total group of patients. These findings may have important clinical implications in the prevention of ARF in postcardiac surgical patients.

A paradox of cerebral hyperperfusion in the face of cerebral hypotension: the effect of perfusion pressure on cerebral blood flow and metabolism during normothermic cardiopulmonary bypass

BACKGROUND

The purpose of this study was to determine the impact of perfusion pressure on cerebral blood flow (CBF) and metabolism during normothermic cardiopulmonary bypass (CPB) and after weaning.

MATERIALS AND METHODS

Two groups of mongrel dogs were studied (Group A, CPB perfusion at 50 mm Hg, n = 6; and Group B, CPB perfusion at 100 mm Hg, n = 6). All animals underwent 2 h of normothermic bypass at cardiac indexes >2.1 L/min/m2 and were weaned from pump, maintained at pressures >75 mm Hg, and followed for an additional 2 h.

RESULTS

In both groups CBF increased over 85% from baseline, in proportion to the hemodilution during the initiation of CPB. Intracranial pressure increased moderately in both groups during CPB, compromising CBF at 1 h in Group A, but not in Group B. The Group A cerebral metabolic rate for oxygen (CMRO2), however, remained unchanged as the percentage of oxygen extraction increased to compensate for the decreased CBF. During recovery, temperature, mean arterial pressure, and cerebral perfusion pressure were not significantly different between the two groups. However, the CBF, percentage of oxygen extracted, and CMRO2 were significantly lower in Group A.

CONCLUSIONS

Normothermic CPB initiated with a crystalloid prime and performed at the lower end of a 50-70 mm Hg perfusion window resulted in a highly significant increase in CBF in order to compensate for hemodilution, while at the same time reduced the perfusion pressure available to supply the increased CBF. Together, these two events create a hemodynamic paradox of hyperperfusion in the face of hypotension. The reduction in CMRO2 in Group A is yet to be explained but seems to remain coupled to CBF and could represent a previously undescribed protective mechanism of hibernating cerebral tissue, similar to the phenomena of ischemic preconditioning in the heart, where cerebral tissue is stimulated to lower metabolism in response to inadequate CBF.

Critical cerebral perfusion pressure during tepid heart operations in dogs

BACKGROUND

The management of blood pressure during cardiopulmonary bypass varies widely. This may be particularly relevant with the trend to warmer bypass temperatures and an older patient population. Therefore, we examined the minimal perfusion pressure that maintains cerebral oxygen delivery during cardiopulmonary bypass at 33 degrees C.

METHODS

Ten dogs were placed on bypass and body temperature was reduced to 33 degrees C (alpha-stat pH management). At six randomly ordered mean arterial blood pressures (35, 40, 45, 50, 60, and 70 mm Hg), cerebral blood flow, oxygen delivery, and metabolic rate were determined.

RESULTS

Cerebral oxygen delivery was stable if the mean arterial pressure was greater than or equal to 60 mm Hg. If mean arterial pressure was less than or equal to 50 mm Hg, cerebral oxygen delivery decreased, and at less than 45 mm Hg cerebral ischemia was seen.

CONCLUSIONS

In a dog without vascular disease, the brain becomes perfusion pressure-dependent at a mean arterial pressure of approximately 50 mm Hg. There is no leftward shift of the cerebral autoregulatory curve during bypass at 33 degrees C. Greater support of mean arterial pressure during "tepid" cardiopulmonary bypass is indicated in the current adult surgical population that is older and has vascular comorbidity.

Cerebral complications after coronary artery bypass and heart valve surgery: risk factors and onset of symptoms

OBJECTIVES

Cerebral complications continue to be a major cause of morbidity after cardiac surgery. Earlier studies have mainly focused on intraoperative events, but symptoms may also occur later in the postoperative period. The purpose of this study was to determine the incidence and risk factors of focal neurologic complications and timing of cerebral symptoms.

DESIGN

A retrospective study.

SETTING

Linköping University Hospital.

PARTICIPANTS

Two thousand four hundred eighty patients who underwent cardiac surgery from 1992 to 1995.

INTERVENTIONS

Standard cardiopulmonary bypass (CPB) technique was used in all patients. Anticoagulant treatment included heparin and patients with coronary artery surgery were also administered acetylsalicylic acid and valve-surgery patients received warfarin or dicumarol.

MEASUREMENTS AND MAIN RESULTS

Seventy-five patients (3%) had focal neurologic deficits and/or confusion postoperatively. In 32 patients (43%), the onset was not intraoperative but occurred later in the postoperative period. The lowest incidence of cerebral complications was found in patients who underwent single-valve replacement (1.2%) and the highest incidence was found in patients who underwent combined procedures (valve and coronary artery surgery; 7.6%). Patients greater than 70 years of age had a complication rate of 4.1% compared with 2.5% in patients aged 70 years and less (p < 0.05). The incidence of diabetes mellitus was 11.4% in the entire series, but was more common (18.7%; p < 0.05) in patients with cerebral symptoms. Also, 5.9% of all patients had a history of cerebrovascular disease compared with 14.7% (p < 0.01) of patients with cerebral complications.

CONCLUSION

Cerebral complications may be delayed after cardiac surgery, suggesting causes of cerebral damage other than intraoperative events. Valve-surgery patients had the lowest incidence and patients with combined procedures had the highest incidence of cerebral complications. Advanced age, diabetes mellitus, and preexisting cerebrovascular disease increased the risk.