Costs and quality of life associated with radial artery and saphenous vein cardiac bypass surgery: results from a Veterans Affairs multisite trial.

BACKGROUND: In coronary artery bypass grafting (CABG) surgery, there is uncertainty about whether the radial artery affects quality of life or costs relative to the saphenous vein. This study compared the cost and quality of life for patients randomized to either radial artery or saphenous vein grafts. METHODS: We analyzed the duration and cost of the index surgery and costs and quality of life (Seattle Angina Questionnaire and Health Utility Index) at 1 year for 726 participants. RESULTS: The 2 treatment groups had similar baseline characteristics. Using the radial artery added approximately 31 minutes to the surgery (from skin incision to skin closure; P < .001) compared with a saphenous vein graft. There were no significant differences in terms of costs and quality of life after the index hospitalization or at 1 year. CONCLUSIONS: Coronary artery bypass grafting with the radial artery lasts approximately 31 minutes longer than with the saphenous vein. However, costs and the quality of life were not statistically different.

Intraoperative myocardial acidosis as a risk for hospital readmission after cardiac surgery.

BACKGROUND: This study elucidates the relationship between intraoperative myocardial acidosis/ischemia and the risk of unplanned hospital readmissions within 30 days and 6 months after cardiac surgery. METHODS: Myocardial tissue pH (corrected to 37 degrees C: pH(37C)) was monitored in 221 patients during cardiac surgery. Regional myocardial acidosis was defined in terms of specific pH thresholds. RESULTS: Fourteen percent and 27% of the patients were readmitted within 30 days and 6 months postoperatively, respectively. The mean number of readmissions was 1.67 +/- 1.24; pH(37C) <6.85 at the end of cardiopulmonary bypass (CPB) was identified as the threshold most significantly associated with readmission. This threshold was associated with a 6-fold increased risk of readmission within 30 days and a 5-fold increased risk within 6 months. CONCLUSIONS: Persistent regional myocardial acidosis after weaning from CPB independently determines unplanned readmission rates up to 6 months postoperatively. This study underscores the importance of avoiding myocardial tissue acidosis during cardiac surgery.

Cerebral hemodynamics during coronary artery bypass graft surgery: the effect of carotid stenosis.

Carotid stenosis is a frequent coexisting condition in patients undergoing coronary artery bypass graft (CABG) surgery. The impact of carotid stenosis on cerebral perfusion is not fully understood. The purpose of this study was to determine the impact of carotid stenosis on cerebral blood flow velocity in patients undergoing CABG. Seventy-three patients undergoing CABG were prospectively recruited and underwent preoperative Duplex carotid ultrasound to evaluate the degree of carotid stenosis. Intraoperatively, transcranial Doppler ultrasound was used to record the mean flow velocity (MFV) within the bilateral middle cerebral arteries. In addition, during the period of cardiopulmonary bypass, regulators of cerebral hemodynamics such as hematocrit, partial pressure of carbon dioxide and temperature were recorded. The ipsilateral middle cerebral artery mean flow velocity was compared in arteries with and without carotid stenosis using a repeated measures analysis. Seventy-three patients underwent intraoperative monitoring during CABG and 30% (n=22) had carotid stenosis. Overall, MFV rose throughout the duration of CABG including when the patient was on cardiopulmonary bypass. However, there was no significant MFV difference between those arteries with and without stenosis (F=1.2, p=.21). Further analysis during cardiopulmonary bypass, demonstrated that hemodilution and partial pressure of carbon dioxide may play a role in cerebral autoregulation during CABG. Carotid stenosis did not impact mean cerebral blood flow velocity during CABG. The cerebrovascular regulatory process appears to be largely intact during CABG.

Saphenous vein conduits harvested by endoscopic technique exhibit structural and functional damage.

BACKGROUND: Injury to the saphenous vein endothelium during harvest impacts patency after coronary artery bypass graft surgery. Many centers are adopting endoscopic saphenous vein harvest (ESVH) instead of using the traditional open saphenous vein harvest (OSVH) technique. Our objective was to compare the effects of ESVH and OSVH on the structural and functional viability of saphenous vein endothelium using multiphoton imaging, immunofluorescence, and biochemical techniques. METHODS: Ten patients scheduled for coronary artery bypass graft surgery were prospectively identified. Each underwent ESVH for one portion and OSVH for another portion of the saphenous vein. A 1-cm segment from each portion was immediately transported to the laboratory for processing. The vessel segments were labeled with fluorescent markers to quantify cell viability (esterase activity), calcium mobilization, and generation of nitric oxide. Samples were also labeled with immunofluorescent antibodies to visualize caveolin, endothelial nitric oxide synthase, von Willebrand factor, and cadherin, and extracted to identify these proteins using Western blot techniques. All labeling, imaging, and image analysis was done in a blinded fashion. RESULTS: Esterase activity was significantly higher in the OSVH group (p < 0.0001). Similarly, calcium mobilization and nitric oxide production were significantly greater in the OSVH group (p = 0.0209, p < 0.0001, respectively). Immunofluoresence and Western blot techniques demonstrated an abnormal alteration in distribution of caveolin and endothelial nitric oxide synthase in the ESVH group. CONCLUSIONS: Our study indicates that ESVH has a detrimental effect on the saphenous vein endothelium, which may lead to decreased graft patency and worse patient outcomes.

Impact of intraoperative myocardial tissue acidosis on postoperative adverse outcomes and cost of care for patients undergoing prolonged aortic clamping during cardiopulmonary bypass.

BACKGROUND: This study examined the impact of intraoperative myocardial acidosis and adverse postoperative outcomes on the cost of cardiac surgical care. METHODS: Myocardial tissue pH corrected to 37 degrees C (pH(37C)) was measured in 162 patients with cross-clamp (XC) duration of 119 minutes or longer. Perioperative data and outcomes were collected prospectively. The Veterans Affairs cost accounting system was used to determine the cost of care in a subset of 57 patients. RESULTS: Long XC duration was associated with significantly increased acidosis and adverse postoperative outcomes. The cost of care for patients with adverse outcomes was increased by 110% (P < .0001). Patients with acidosis at the end of reperfusion had significantly (P = .0470) increased costs of care. End reperfusion of myocardial tissue pH(37C) of less than 7.0, diabetes mellitus, and body surface area were significant determinants of postoperative adverse outcomes. CONCLUSIONS: Intraoperative myocardial acidosis is a determinant of postoperative adverse outcomes and cost in cardiac surgery. Reducing XC duration and improving intraoperative myocardial protection should improve outcomes and reduce cost.

Intraoperative cerebral high-intensity transient signals and postoperative cognitive function: a systematic review.

BACKGROUND: Much attention in the literature has focused on the relationship between perioperative microemboli during cardiac and vascular surgery and postoperative cognitive decline. Transcranial Doppler ultrasonography (TCD) has been used to measure high-intensity transient signals (HITS), which represent microemboli during cardiac, vascular, and orthopedic surgery. The purpose of this study was to systematically examine the literature with respect to HITS and postoperative cognitive function. METHODS: Systematic PubMed searches identified articles related to the use of TCD and cognitive function in the surgical setting. RESULTS: The literature remains largely undecided on the role of HITS and cognitive impairment after surgery, with most studies being underpowered to show a relationship. Although the cognitive effects of HITS may be difficult to detect, subclinical microemboli present potential harm, which may be modifiable. CONCLUSIONS: TCD represents a tool for intraoperative cerebral monitoring to reduce the number of HITS during surgery.

Microemboli are not associated with delirium after coronary artery bypass graft surgery.

Delirium is an acute change in cognition which occurs frequently after coronary artery bypass graft (CABG) surgery. Cerebral microemboli, from plaque, air, or thrombus, have been hypothesized to contribute to delirium and cognitive decline after CABG. The purpose of this study was to determine if there was an association between cerebral microemboli and delirium after cardiac surgery. Non-delirious patients (n=68) were prospectively enrolled and underwent intraoperative monitoring of the middle cerebral arteries with transcranial Doppler (TCD). TCD signals were saved and analyzed postoperatively for microemboli manually, according to established criteria. Postoperatively, patients were assessed for delirium with a standardized battery. Thirty-three patients (48.5%) developed delirium after surgery. Microemboli counts (mean + or - SD) were not significantly different in those with and without delirium (303 + or - 449 vs. 299 + or - 350; p=0.97). While intraoperative microemboli were not associated with delirium after CABG, further investigation into the source and composition of microemboli can further elucidate the long-term clinical impact of microemboli.

Troponin I after cardiac surgery and its implications on myocardial protection, outcomes, and cost.

BACKGROUND: Myocardial acidosis during cardiac surgery and postoperative troponin I are markers of myocardial damage that have been shown to predict adverse outcomes. We investigated the relationship between troponin I and myocardial tissue pH, patient outcomes, and cost. METHODS: Data were prospectively collected on 205 cardiac surgery patients. Troponin I was sampled upon arrival to the intensive care unit (ICU) and every 6 hours thereafter for 24 hours. The lowest pH encountered during aortic cross clamp (LpH) was related to postoperative troponin I on the multivariate level. Multivariate models were constructed to predict adverse events (AE) and cost. RESULTS: LpH was an independent inverse determinant of postoperative troponin I (P = .0067). Troponin I and its interaction with LpH were multivariate predictors of AE (P = .0012; .0001;odds ratio = 6.9, 10.2, respectively). Troponin I independently predicts surgical ICU (SICU) cost (P = .0256). CONCLUSION: Postoperative troponin I elevation reflects intraoperative myocardial acidosis and damage. The strong relationship between troponin I, AE, and cost indicates the damage incurred is clinically and economically relevant. Strategies to ameliorate intraoperative myocardial tissue acidosis will decrease troponin I release, subsequent AE, and associated costs.

Patients with diabetes mellitus undergoing cardiac surgery are at greater risk for developing intraoperative myocardial acidosis.

OBJECTIVE: In patients undergoing cardiac surgery, intraoperative myocardial acidosis, which quantifies regional myocardial ischemia, has been shown to increase the risk of adverse postoperative outcomes. In this study, we sought to determine the course of intraoperative myocardial acidosis and its impact on postoperative survival in patients with diabetes mellitus undergoing cardiac surgery. METHODS: Intraoperative myocardial tissue pH(37C) was continuously measured in the anterior and posterior left ventricular walls in 264 patients undergoing cardiac surgery; 74 (28.0%) of the patients had diabetes (insulin-dependent diabetes: 54%; non-insulin dependent diabetes: 46%). The shortest time required to reach intraoperative myocardial tissue pH < 6.34 during aortic occlusion and > 6.73 during reperfusion were compared in 3 patient groups: insulin-dependent, non-insulin dependent, and nondiabetic. These pH thresholds have been demonstrated to be associated with adverse postoperative long-term survival. RESULTS: The median times to reach intraoperative myocardial tissue pH(37C) < 6.34 during aortic occlusion were 14, 23, and 36 minutes in the insulin-dependent, non-insulin dependent, and non-diabetic groups, respectively (P = .003). The time taken to reach intraoperative myocardial tissue pH(37C) > 6.73 during reperfusion was similar between the 3 groups. After adjusting for relevant pre- and intraoperative parameters, the risk of developing intraoperative myocardial tissue pH < 6.34 during aortic occlusion was 73% higher in patients with insulin-dependent diabetes mellitus (P = .022) but the same in with patients with non-insulin dependent diabetes mellitus (P = .98) when compared with patients without diabetes. Patients with insulin-dependent diabetes mellitus also had nearly threefold decrease in long-term survival compared with that of patients without diabetes (P = .0007). CONCLUSIONS: Patients with insulin-dependent diabetes mellitus undergoing cardiac surgery are at a greater risk of developing intraoperative myocardial acidosis/ischemia and of decreased survival postoperatively compared with patients without diabetes.

Adverse 30-day outcomes after cardiac surgery: predictive role of intraoperative myocardial acidosis.

BACKGROUND: Regional myocardial acidosis in patients undergoing cardiac surgery has been shown to be reflective of regional myocardial ischemia. This study elucidates the relationship between intraoperative regional myocardial acidosis and 30-day postoperative outcomes after cardiac surgery. METHODS: Intramyocardial tissue pH in the anterior and posterior left ventricular walls was measured in 397 adult patients undergoing valve replacement or coronary revascularization surgery between 1987 and 2001. Dedicated nurses and research assistants prospectively collected preoperative, intraoperative, and outcomes data. Regional myocardial acidosis was defined in terms of pH thresholds identified by recursive partitioning. Adverse 30-day outcome, defined as death or any one of six complications, was the dependent variable in a multivariate logistic regression analysis. A morbidity score was developed on the basis of the sensitivity of each of the six complications in predicting death, and was the dependent variable in a multivariate linear regression analysis. RESULTS: During the period of aortic clamping, a mean intramyocardial tissue pH less than 6.85 was identified to be significant by recursive partitioning, and was encountered in either the anterior or posterior left ventricular wall in 85.4% of patients. After adjusting for preoperative and intraoperative variables, this pH threshold was found to be significantly associated with increased adverse outcomes within 30 days after surgery (p = 0.045). It was also significantly associated with increase in the morbidity score (p = 0.05). CONCLUSIONS: Regional myocardial acidosis of a magnitude frequently encountered during aortic clamping is an independent determinant of adverse 30-day outcomes after cardiac surgery. Its reversal by pH-guided myocardial management has the potential of improving postoperative patient outcomes.

Atherosclerosis is associated with delirium after coronary artery bypass graft surgery.

OBJECTIVES: To investigate whether atherosclerosis of the ascending aorta, internal carotid arteries, and coronary arteries is predictive of postoperative delirium in subjects undergoing coronary artery bypass graft (CABG) surgery. DESIGN: Prospective cohort study. SETTING: Boston Veterans Affairs Healthcare System. PARTICIPANTS: Thirty-six male veterans undergoing primary CABG surgery. MEASUREMENTS: Subjects underwent Duplex ultrasound to assess stenosis in the internal carotid arteries. Information on the ascending aortic plaque, as assessed by transesophageal echocardiogram, and the number of coronary vessels bypassed was collected. To create an atherosclerosis score, the number of atherosclerotic areas was added. A validated delirium battery was administered to the subjects preoperatively and on postoperative Days 2 and 5. RESULTS: Fifteen subjects (41.7%) developed delirium postoperatively. In bivariate analysis, carotid stenosis of 50% or more (relative risk (RR)=3.5, 95% confidence interval (CI)=1.5-8.1) and moderate-severe ascending aortic plaque (RR=2.9, 95% CI=1.0-8.5) were significantly associated with the development of delirium. There was a trend toward a significant association for three or more vessels bypassed (RR=9.6, 95% CI=0.6-145.3). After controlling for age, baseline cognition, and medical comorbidity, the atherosclerosis score was significantly associated with postoperative delirium (adjusted RR=2.7, 95% CI=1.1-6.8). CONCLUSION: In this preliminary report, atherosclerosis in the carotid arteries, aorta, and coronary circulation is associated with the development of delirium after CABG surgery. Further investigation into atherosclerosis as a risk factor for delirium is warranted.

Intraoperative regional myocardial acidosis and reduction in long-term survival after cardiac surgery.

BACKGROUND: Regional myocardial acidosis, as measured with tissue pH electrodes during cardiac surgery, has been shown to be reflective of regional myocardial ischemia. This study examined the relationship between intraoperative regional myocardial acidosis and long-term survival of patients undergoing cardiac surgery with cardiopulmonary bypass. METHODS: A total of 496 adult patients who underwent valve replacement, coronary artery revascularization, or both with intraoperative myocardial pH monitoring in the anterior and posterior left ventricular walls were followed up for 3 to 17 years (average 10.2 +/- 4.9 years) for all cause mortality. Regional myocardial acidosis in each patient was defined by the lower of the anterior and posterior wall pH values. RESULTS: A bivariate automatic interaction detection analysis identified three significant regional myocardial acidosis thresholds that affected long-term mortality: pH 37C less than 6.63 before aortic crossclamping, integrated mean pH 37C less than 6.34 during the period of aortic crossclamping, and pH 37C less than 6.73 at discontinuation of cardiopulmonary bypass. Cox proportional hazard regression analysis identified each of these thresholds to be independently determinant of survival, with pH 37C during aortic crossclamping having the highest risk ratio (risk ratio 2.15, 95% confidence interval 1.37-3.37). Raising pH 37C from lower than threshold before aortic crossclamping to higher than threshold during clamping increased the median survival by 40.2%. CONCLUSION: In adult patients undergoing cardiac surgery with cardiopulmonary bypass, regional myocardial ischemic acidosis before aortic crossclamping, during aortic crossclamping, and at discontinuation of cardiopulmonary bypass are independently associated with reduced long-term postoperative survival. Reversing or avoiding myocardial acidosis during cardiac surgery improves long-term patient survival.

Intraoperative regional myocardial acidosis predicts the need for inotropic support in cardiac surgery.

OBJECTIVE: To determine the impact of regional myocardial acidosis encountered during cardiac surgery on the need for inotropic and intra-aortic balloon (IAB) support. METHODS: Intramyocardial tissue pH(37C) was measured in 247 patients undergoing cardiopulmonary bypass (CPB). Inotropic support (INO) was defined as requiring one or more of norepinephrine/epinephrine/amrinone/dobutamine/>2.5 mug/kg/min dopamine, for at least 45 minutes intraoperatively, and intraoperative or postoperative IAB use. PH (corrected to 37 degrees C, pH(37C)) during surgery was compared in patients who needed INO versus those who did not. Multivariate logistic regression models identified the determinants of INO. RESULTS: Fifty patients (20.2%) required INO intraoperatively. pH(37C) was significantly lower throughout reperfusion in patients needing INO. Preoperative ejection fraction and pH(37C) during reperfusion were identified as independent predictors of INO. CONCLUSIONS: This is the first study to show that intraoperative regional myocardial acidosis, a preventable condition, independently determines the need for intraoperative INO. Increased INO is associated with greater postoperative mortality and morbidity.

Determinants of regional myocardial acidosis during cardiac surgery.

BACKGROUND: Intraoperative regional myocardial acidosis (RMA) during cardiac surgery has been shown to be reflective of regional myocardial ischemia and an independent predictor of adverse postoperative outcomes. This study identifies the determinants of intraoperative RMA. METHODS: Intramyocardial tissue pH(37C) in the anterior and posterior LV walls was measured in 641 adult patients during cardiac surgery. RMA at two intraoperative periods was quantified as integrated mean pH(37C) < 6.35 during aortic clamping (AC) and pH(37C) < 6.73 at the end of cardiopulmonary bypass (CPB). These pH thresholds were chosen because of their demonstrated relationship to long-term patient survival. Multivariate logistic regression models were constructed. An acidosis prediction score was constructed based on the factors determining RMA at the end of CPB. RESULTS: Independent determinants of RMA during AC were preoperative New York Heart Association class III/IV (P = .007), current smoker (P = .0088), pH(37C) < 6.63 prior to AC (P < .0001), and intraoperative myocardial management technique (P = .0001). Independent determinants of RMA at end of CPB were ASA class IV/V (P = .0042), pH(37C) < 6.63 prior to AC (P = .035), pH(37C) < 6.35 during AC (P = .001), and total duration of CPB > or = 212 minutes (P = .001). CONCLUSIONS: RMA during cardiac surgery is determined by patient risk factors, the magnitude of preceding regional myocardial acidosis, and the duration of CPB.

Acidosis-induced apoptosis in human and porcine heart.

BACKGROUND: Acidosis-mediated injury to cardiac myocytes during surgery may lead to progressive heart failure. The nature of this injury, although not well defined, may be caused by induction of apoptosis in cardiac myocytes. We applied fluorescence imaging and biochemical techniques to assess apoptosis in cardiac myocytes excised from human patients and porcine subjects maintained on cardiopulmonary bypass to demonstrate the relationship between acidosis and apoptosis. METHODS: Multiphoton microscopy was used to image fluorescence signals generated in myocytes deep within atrial and ventricular biopsies for identification of apoptotic changes. The biopsies, obtained during cardiac surgery, were subjected to ex vivo or in vivo acidosis. Proapoptotic markers such as exposure of phosphatidyl serine, cytochrome c, apoptotic protease-activating factor-1, and caspase-3 were identified using fluorescence-based imaging and biochemical assays. RESULTS: Within 30 minutes of storage in low pH (<7) buffers, apoptosis was detected in human atrial samples, the severity of which correlated well with low pH. Apoptosis was also detected in atrial and ventricular biopsy samples obtained from three porcine subjects maintained on cardiopulmonary bypass and undergoing 110 minutes of aortic cross-clamp and 10 minutes of reperfusion, in which the cardiac pH was 6.36, 7.14, and 7.48. The apoptosis level detected in postacidotic reperfused cardiac tissue was pH dependent and approximately threefold greater than the precross-clamp levels. CONCLUSIONS: Using fluorescence multiphoton microscopy and biochemical techniques we have assessed a direct correlation between low pH and induction of apoptosis in cardiac samples obtained both from human patients undergoing cardiac surgery and porcine subjects maintained on cardiopulmonary bypass simulating cardiac surgery.

Multi-photon microscopic evaluation of saphenous vein endothelium and its preservation with a new solution, GALA.

BACKGROUND: Injury to endothelium can compromise the patency of bypass grafts harvested during coronary artery bypass graft (CABG) surgery. Maintaining structural and functional viability of endothelium in grafts may lead to improved long-term patency. The information gained from the application of multi-photon microscopy in transmission and epifluorescence mode was used to assess the structural and functional integrity of human saphenous vein segments stored in multiple preservation solutions, and to design a superior storage solution. METHODS: Multi-photon microscopy was used to image deep within saphenous vein tissue harvested from patients undergoing CABG for analysis of endothelial structure and function. Endothelial cell structural viability, calcium mobilization, and nitric oxide generation were determined using specific fluorescence markers. RESULTS: Within 60 minutes of harvest and storage in standard preservation solutions, calcium mobilization and nitric oxide generation were markedly diminished with more than 90% of endothelial cells no longer viable in the vein. In contrast, veins could be stored for 24 hours without substantial loss in cell viability in a newly formulated heparinized physiologic buffered salt solution containing glutathione, ascorbic acid, and L-arginine (GALA). CONCLUSIONS: Standard solutions in clinical use today led to a profound decline in saphenous vein endothelial cell viability, whereas the newly designed physiologic salt solution (GALA) maintained endothelial function and structural viability for up to 24 hours. The improvements seen from using GALA as a vessel storage medium may lead to greater long-term vein graft patency following CABG surgery.