Preservation of static and dynamic cerebral autoregulation after mild hypothermic cardiopulmonary bypass

Background. Dysfunction of cerebral autoregulation might contributeto neurological morbidity after cardiac surgery. In this study,our aim was to assess the preservation of cerebral autoregulationafter cardiac surgery involving cardiopulmonary bypass (CPB). Methods. Dynamic and static components of cerebral autoregulationwere evaluated in 12 patients undergoing coronary artery bypassgraft surgery, anaesthetized with midazolam, fentanyl, and propofol,and using mild hypothermic CPB (31–33°C). Arterialpressure (ABP), central venous pressure (CVP), and blood flowvelocity in the middle cerebral artery (CBFV) were recorded.The cerebral perfusion pressure (CPP) was calculated as a differencebetween mean ABP and CVP. Rapid decrease of CPP was caused bya sudden change of patients' position from Trendelenburg toreverse Trendelenburg. Cerebral vascular resistance (CVR) wascalculated by dividing CPP by CBFV. Index of static cerebralautoregulation (CAstat) was calculated as the change of CVRrelated to change of CPP during the manoeuvre. Dynamic rateof autoregulation (RoRdyn) was determined as the change in CVRper second during the first 4 s immediately after a decreasein CPP, related to the change of CPP. Measurements were obtainedafter induction of anaesthesia, and 15, 30, and 45 min aftertermination of CPB. Results. No significant changes were found in CAstat or RoRdynafter CPB. Significant changes in CVR could be explained byconcomitant changes in body temperature and haematocrit. Conclusion. Autoregulation of cerebral blood flow remains preservedafter mild hypothermic CPB.      

Dynamic evaluation of fluid shifts during normothermic and hypothermic cardiopulmonary bypass in piglets

BACKGROUND: Edema, generalized overhydration and organ dysfunction commonly occur in patients undergoing open-heart surgery using cardiopulmonary bypass (CPB) and induced hypothermia. Activation of inflammatory reactions induced by contact between blood and foreign surfaces are commonly held responsible for the disturbances of fluid balance ("capillary leak syndrome"). We used an online technique to determine fluid shifts between the intravascular and the interstitial space during normothermic and hypothermic CPB. METHODS: Piglets were placed on CPB (fixed pump flow) via thoracotomy in general anesthesia. In the normothermic group (n=7), the core temperature was kept at 38 degrees C prior to and during 2 h on CPB, whereas in the hypothermic group (n=7) temperature was lowered to 28 degrees C during bypass. The CPB circuit was primed with acetated Ringer's solution. The blood level in the CPB circuit reservoir was held constant during bypass. Ringer's solution was added when fluid substitution was needed (falling blood level in the reservoir). In addition to invasive hemodynamic monitoring, fluid input and losses were accurately recorded. Inflammatory mediators or markers were not measured in this study. RESULTS: Cardiac output, s-electrolytes and arterial blood gases were similar in the two groups in the pre-bypass period. At start of CPB the blood level in the machine reservoir fell markedly in both groups, necessitating fluid supplementation and leading to a markedly reduced hematocrit. This extra fluid need was transient in the normothermic group, but persisted in the hypothermic animals. After 2 h of CPB the hypothermic animals had received 7 times more fluid as compared to the normothermic pigs. CONCLUSION: We found strong indications for a greater fluid extravasation during hypothermic CPB compared with normothermic CPB. The experimental model using the CPB-circuit reservoir as a fluid gauge gives us the opportunity to study further fluid volume shifts, its causes and potential ways to optimize fluid therapy protocols.     

Effect of acid-base management with or without carbon dioxide on plasma phosphate concentration during and after hypothermic cardiopulmonary bypass.

Variations of the phosphate concentration in plasma were studied in two groups of 12 patients undergoing cardiac surgery with hypothermic cardiopulmonary bypass (CPB). Management of the acid-base status differed between the groups, according to whether or not carbon dioxide was added to the anesthetic gas mixture during hypothermia ('pH-stat' vs. 'alpha-stat' mode) following correction vs. no correction of pCO2 and pH for body temperature. Phosphate variations throughout the study were mostly within normal limits. From the start to the end of CPB, the mean rise in phosphate levels was 70% in the pH-stat group and 37% in the alpha-stat group (p < 0.001). During 3 hours after CPB, the phosphate values continued to rise by a mean of 25% in the alpha-stat patients, but fell by a mean of 3% in the pH-stat patients (p < 0.001). Such different phosphate patterns during and immediately after CPB may reflect profound metabolic disturbances and may be related to the altering effects of CO2 addition and respiratory acidosis on intracellular metabolic activity and phosphate homeostasis.     

氨甲环酸减少体外循环心脏手术后失血的作用及与抑肽酶的比较研究

目的 观察氨甲环酸减少体外循环（ＣＰＢ）心脏手术后失血的作用,探讨其其作用机制,并与抑肽酶比较。方法 随机选取ＰＣＢ心脏手术病人３０例,分为氨甲环酸用药组（ＴＡ组,１０例）,抑肽酶用药组（ＡＰ组,１０例）和对照组（Ｃ组,１０例）。于ＣＰＢ前、中、后２ｈ分别测定ｔ－ＰＡ和ＰＡＩ－Ｉ活性、ＴＸＢ２和６－ｋｅｔｏ－ＰＧＦ１α含量、ＡＤＰ诱导的血小板最大聚集率和血小板超微结构变化,记录各组术后纵隔心包引流     

Study of perioperative extravascular lung water and intrathoracic blood volume in patients undergoing CABG surgery with or without cardiopulmonary bypass

BackgroundWhether off-pump coronary artery bypass graft (OPCAB) surgery is superior to traditional on-pump coronary artery bypass graft (CABG) surgery still one of the most controversial areas of cardiac surgery and anesthesia. We hypothesized that OPCAB surgery may result in less accumulation of extra-vascular lung water (EVLW) and intra-thoracic blood volume (ITBV) in the peri-operative period.Patients and MethodsThirty patients underwent elective CABG surgery were randomized for this study, 15 OPCAB (group 1) and 15 on Pump (group 2). We measured EVLW and ITBV by PiCCO monitor in 8 times; before induction of anesthesia, after induction of anesthesia and before skin incision, before starting revascularization in group 1 or before cardiopulmonary bypass in group 2, at the end of revascularization in group 1 or at the end of CBP in group 2, at the end of surgery (after skin closure), two hours after the end of surgery, six hours after the end of surgery, twelve hours after the end of surgery and finally in the morning of first postoperative period.ResultsDemographic data and the preoperative characteristics were comparable in both patient groups. The intra-operative course was uneventful, and the intra-operative and postoperative characteristics were comparable in both patient groups. In all patients, complete revascularization was achieved. Extra-vascular lung water and intra-thoracic blood volume did not differ between groups in all times of measurements.Discussion and ConclusionThe clinical advantage of off-pump CABG surgery over standard extracorporeal circulation in regard to lung water content was not found in our study. In conclusion, the presumed superiority of off pump surgery for coronary artery bypass grafting could not be confirmed in our group of patients.