Volatile anaesthesia during cardiopulmonary bypass.

Since its inception, administering and ensuring anaesthesia during cardiopulmonary bypass has been challenging. Partly because of the difficulty of administering volatile agents during cardiopulmonary bypass, total intravenous anaesthesia has been a popular technique used by cardiac anaesthetists in the last two decades. However, the possibility that volatile agents reduce mortality and the incidence of myocardial infarction by preconditioning the myocardium has stimulated a resurgence of interest in their use for cardiac anaesthesia. The aim of this review is to provide an overview of the administration of volatile anaesthetic agents during cardiopulmonary bypass for the maintenance of anaesthesia and to address some of the practical issues that are involved in doing so.

Brain damage and cardiopulmonary bypass: is there really any association?

Brain damage, in the form of stroke and cognitive deficit associated with heart surgery, has long been attributed unquestioningly to cardiopulmonary bypass (CPB). The aim of this paper is to review the randomised control trials (RCT), systematic reviews and meta-analyses of studies, comparing patients who have undergone on- or off-pump coronary artery bypass grafting (CABG) surgeries that have used stroke or cognition as an outcome to determine whether CPB is associated with brain damage. Although not definitive, the evidence base to date strongly suggests that the incidence of stroke and the effect on cognition, if any, are no different whether CABG surgery is undertaken on- or off-pump. In addition and contrary to long-held beliefs, this review leads to the conclusion that CPB may well not be the cause of the brain damage associated with heart surgery.

Changing the priming solution from Ringer's to Hartmann's solution is associated with less metabolic acidosis during cardiopulmonary bypass.

BACKGROUND AND OBJECTIVE: Previously, it was noted that changing the solutions used for priming and intravascular volume replacement from Hartmann's to Ringer's resulted in a more profound metabolic acidosis developing during cardiopulmonary bypass (CPB). The aim of this study was to examine the effects of changing the solutions back to Hartmann's on metabolic acidosis that develops during CPB in patients undergoing heart surgery. METHODS: Two groups of patients were studied sequentially: the first received Ringer's (n = 63) and the second Hartmann's solution (n = 66). Arterial blood samples were taken before induction of anaesthesia and towards the end of CPB. Samples were analysed in a blood gas analyser. RESULTS: Hydrogen ion concentration increased from 38 (4) to 41 (7)mmol/L in the Ringer's group, but decreased from 38 (5) to 36 (6) mmol L(-1) in the Hartmann's group. Changes in PaCO2 (0.77, p < 0.001) and volume of fluid administered (r= 0.23, p <0.01) were significant univariate correlates of change in hydrogen ion concentration, but haemoglobin concentration was not (r < 0.01, p = 0.97). Analysis of variance for repeated measures found significant between subject effects on the change in hydrogen ion concentration during CPB caused by the choice of intravascular solution used (p < 0.001) and PaCO2 (p = 0.001), but not as a result of the volume of solution administered (p > 0.10). CONCLUSIONS: Changing the solutions used for priming and intravascular volume replacement from Ringer's to Hartmann's was associated with a reduction in metabolic acidosis that developed during CPB.

Dysaesthesia associated with sternotomy for heart surgery.

BACKGROUND: Chronic pain occurs in 40-50% patients following cardiac surgery. Dysaesthesia, either in the form of heightened or diminished skin sensation, are frequently associated with chronic neuropathic pain. Therefore, dysaesthesia in the early postoperative period may predict chronic pain. However, the character and causes of dysaesthesia in the early postoperative period are unknown. The aim of this study was to investigate the incidence, extent, and causes of dysaesthesia following cardiac surgery by sternotomy. METHODS: In a prospective cohort study, 50 patients undergoing sternotomy for cardiac surgery were admitted to the study: 38 underwent coronary artery bypass graft (CABG), nine valve surgery, and three combined surgery. Forty-eight hours postoperatively, acute pain was measured by four-point verbal scale. Manual pinprick and cotton wool brushing was used to detect the areas of dysaesthesia. RESULTS: Some form of dysaesthesia was found in 27 (54%) of the patients. Using multivariate regression analysis, the total area of dysaesthesia was positively associated with CABG surgery and the severity of postoperative pain (P<0.001). CONCLUSION: Dysaesthesia is common in the early postoperative period following cardiac surgery using a sternotomy and is associated with CABG surgery. The association with severity of pain may indicate a neuropathic element that is unrelieved by conventional opioid analgesia.

Jugular bulb oxyhemoglobin desaturation, S100beta, and neurologic and cognitive outcomes after coronary artery surgery.

UNLABELLED: We reported that a decline in cognitive performance 3 mo after coronary artery bypass grafting surgery is associated with palpable aortic atheroma, but not postoperative jugular bulb oxyhemoglobin saturation (SjO2) <50%. However, the effect of SjO2 on clinical neurologic findings is not known. S100beta is a possible surrogate biochemical marker of brain injury, and we report here the scored clinical neurologic findings in 98 patients from our previous study in relation to SjO2, cognitive performance, aortic atheroma, and S100beta. Patients underwent a scored neurologic examination and cognitive assessment the day before and 3 mo after coronary artery bypass grafting surgery. Intraoperatively, intermittent blood sampling was performed, and postoperatively, the area under the curve describing SjO2 <50% in relation to time was calculated from continuous jugular bulb reflectance oximetry. Palpation was used to assess the ascending aorta for the presence of atheroma. The jugular bulb concentration of S100beta was measured 6 h after completion of surgery. The neurologic score 3 mo after surgery did not correlate with either intra- or postoperative SjO2 (r = 0.111, P = 0.278; and r = -0.074, P = 0.467, respectively). The main determinant of neurologic score at 3 mo was the preoperative neurologic score (r(2) = 0.63, P < 0.001), whereas palpable atheroma of the ascending aorta made a small but significant contribution (r(2) = 0.034, P = 0.004). Neurologic and cognitive scores correlated before surgery (r = 0.226, P = 0.022) and at 3 mo after surgery (r = 0.348, P < 0.001). A preoperative neurologic deficit of two or more had a small but significant negative effect on cognitive performance at 3 mo (standardized beta = -0.097, P = 0.018). There was a significant univariate correlation between S100beta and the 3-mo neurologic score (r = -0.232, P < 0.05), but not a multivariate correlation (beta = -0.090, P = 0.156). IMPLICATIONS: Intraoperative jugular bulb oxyhemoglobin saturation (SjO2) and postoperative SjO2 <50% do not have an important influence on long-term neurologic outcome after coronary artery bypass graft surgery. Subtle preoperative neurology is associated with long-term cognitive decline, and aortic atheroma is a risk factor for both cognitive and neurologic decline.

Cerebral hypoperfusion in immediate postoperative period following coronary artery bypass grafting, heart valve, and abdominal aortic surgery.

Perioperative levels of jugular bulb oxyhaemoglobin saturation (Sj(O(2))) and lactate concentration (Lj), and postoperative duration of Sj(O(2))<50% were compared between patients undergoing coronary artery bypass grafting (CABG) (n=86), heart valve (n=14) and abdominal aortic (n=16) surgery. Radial artery and jugular bulb blood samples were aspirated after induction of anaesthesia, during re-warming on cardiopulmonary bypass (CPB) (36 degrees C), on arrival in the intensive care unit (ICU) and, subsequently, at 1, 2 and 6 h after ICU admission. Most patients having heart surgery were hypocapnic at 36 degrees C on CPB. Following CABG and heart valve surgery, many patients were hypocapnic whereas after abdominal aortic surgery, most were hypercapnic. During CPB and postoperatively, Sj(O(2)) and Lj were significantly correlated to Pa(CO(2)) and the arterial concentration of lactate (La) respectively (P<0.05). After correction for arterial carbon dioxide tension (Pa(CO(2))) and La, there were no significant changes in Sj(O(2)) or Lj on CPB. Postoperatively, having corrected for Pa(CO(2)), there were significant effects on Sj(O(2)) over all groups as a result of time from surgery (P<0.001) and its interaction with operation type (P<0.001). Following correction for La, there were no postoperative effects on Lj. No significant differences (P=0.2) in duration of Sj(O(2))<50% existed between patients undergoing CABG (1054 (82) min), abdominal aortic (893 (113) min) and heart valve (1073 (91) min) surgery. The lack of significant reciprocal effects on Lj combined with the frequency of hypocapnia and strong influence of Pa(CO(2))()on Sj(O(2)), suggest that Sj(O(2))<50% during CPB and after cardiac surgery represents hypoperfusion as a consequence of hypocapnia rather than cerebral ischaemia.

Cognition after coronary artery surgery is not related to postoperative jugular bulb oxyhemoglobin desaturation.

During the early postoperative period after coronary artery bypass grafting (CABG) surgery, many patients experience jugular bulb oxyhemoglobin desaturation (SjO(2) < 50%). We sought to determine whether SjO(2) during cardiopulmonary bypass and the early postoperative period influenced long-term cognitive performance after CABG surgery. One hundred two patients completed a battery of cognitive tests the day before and 3 mo after CABG surgery. A General Cognitive Score was generated from these tests as an overall measure of cognitive function. Intraoperatively, SjO(2) was determined by intermittent blood sampling, and postoperatively, the area under the curve of SjO(2) < 50% and time was calculated from continuous reflectance oximetry. No significant correlations between cognitive performance and either intra- or postoperative SjO(2) were found. Preoperative cognitive performance was the main determinant of cognition at 3 mo (r(2) = 0.83, P<0.001), and palpable atheroma of the ascending aorta made a small, but significant, contribution to a decline in cognition (r(2) = 0.018, P = 0.001).

Continuous monitoring of jugular bulb oxyhaemoglobin saturation using the Edslab dual lumen oximetry catheter during and after cardiac surgery.

Fibreoptic jugular bulb oximetry has been validated for use in the care of severely head-injured patients. We compared bench and fibreoptic methods of measuring jugular bulb oxyhaemoglobin saturation (SjO2) in 33 patients undergoing cardiac surgery both during cardiopulmonary bypass (CPB) and in the early postoperative period. After insertion of a fibreoptic reflectance oximetry catheter into the jugular bulb, it was calibrated against a bench oximeter. Comparisons were made while on CPB (n = 60) and in the postoperative period for up to 18 h (n = 215). There was negligible bias throughout. There were wide limits of agreements (mean difference +/- 2SD) between the two methods during operation (-20.29% to 18.05%), whereas after operation the limits of agreement were far narrower (-6.39% and 7.45%). Measurement of SjO2 by the fibreoptic method compared poorly with bench oximetry during CPB but there was good agreement between the two methods in the early postoperative period.