Propofol and hypothermic cardiopulmonary bypass

The effects of propofol during low flow (1.6 l.min-1.m-2) hypothermic (27-29 degrees C) cardiopulmonary bypass on systemic haemodynamic and metabolic variables were studied in 20 patients in a parallel group comparison. Patients in the control group underwent two consecutive control periods, whereas those in the propofol group underwent a control period followed by a 'propofol' period during which they received an intravenous bolus of propofol 5 mg.kg-1 followed by an infusion at a rate of 20 mg.kg-1.h-1. Haemodynamic and metabolic variables were measured at the end of each period. The propofol group showed a significant reduction in both systemic vascular resistance (p less than 0.001) and systemic oxygen uptake (p less than 0.05). There was a small but significant fall in lactate in the control group (p less than 0.02); however, there was no significant change in the propofol group. These findings could indicate impaired tissue perfusion, although they more likely indicate systemic metabolic depression with washout of lactate from previously hypoperfused tissues.     

舒芬太尼对心脏瓣膜置换术患者血浆炎性细胞因子及丙二醛的影响

Objective To investigate the effect of sufentanil on inflammatory cytokines and MDA of plasma in valve replacement surgery during cardiopulmonary bypass (CPB). Methods Thirty adult patients undergoing valve replacement with cardiopulmonary bypass were randomly divided into 3 groups: Group S1(suifentanil 3 μg/kg), Group S2(sulfentanil 5 μg/kg), Group S3( sulfentanil 10 μg/kg). Blood samples were taken before anesthesia (T1),5 min after opening the thorax (T2), 30 min after aortic clamping(T3), 2 h after aortic declamping( T4), and 24 h (T5) after the operation for determination of plasma levels of tumornecrosis factor(TNF-α), interteukin-6( IL-6 )and MDA. The stage of ICU and the extubation time were recorded. Results Levels of TNF-α, IL-6 and MDA after the CPB in the 3 groups were significantly higher compared with T0(P<0.01). TNF-α(ng/L), IL-6(ng/L) and MDA (mmol/Dlevels at T2,T3 were significantly lower in Group S2 (at T2: TNF-α15.7±4.1 ,IL-6 116.5±18.2 and MDA 8.5±0.8, at T3: TNF-α22.8±3.6,IL-6 158.9±13.7 and MDA 10.2±1.3)than those in Group S1 (at T2: TNF-α20.3±4.5、IL-6 141.8±21.3 and MDA 10.6±0.9, at T3: TNF-α28.1 ±3.7,IL-6 175.6±15.1 and MDA 12.5±1.4). TNF-α, IL-6 and MDA levels at T2, T3 were significantly lower in Group S3(at T2: TNF-α15.7±4.1 JL-6 116.5±18.2 and MDA 8.5±0.8,at T3: TNF-α22.8±3.6、IL-6 158.9±13.7 and MDA 10.2±1.3)than those in Group S1. But levels of TNF-α,IL-6, and MDA in Group S2 were not significantly different compared with those in Group S3. The duration of stay in ICU and time of endotracheal extubation were significantly longer in patients of Group S3 ( 3.5±0.5 ) d, (29.3±3.0) h than those of Group S1 ( 2.2±0.5 )d, (18.2±2.5)handS2(2.4±0.4d,(19.3±2.8) h(P<0.05). Conclusion CPB leads to a proinflammatory response, as well as oxygen free radicals release. Larger dose sufentanil seemed to be effective in reducing CPB-induced inflammatory response and ischemic reperfusion injury, but the effect was not dependent on dose while sufentanil dose reaching some value, at the same time the duration of stay in ICU and time of endotracheal extubation were longer.     

舒芬太尼对心脏瓣膜置换术患者血浆炎性细胞因子及丙二醛的影响

目的 探讨不同剂量舒芬太尼对心脏瓣膜置换术患者围术期血浆炎性细胞因子和丙二醛(malonic dialdehyde,MDA)的影响.方法 30例心脏瓣膜置换术患者,随机分为3 组即 S1组(舒芬太尼总量3μg/kg),S2组(舒芬太尼总量5μg/kg)和S3组(舒芬太尼总量10 μg/kg).分别于麻醉前(T0)、开胸后5 min(T1)、阻断后30 min(T2)、开主动脉后2 h(T3)和术后24 h(T4)各时间点测定动脉血中肿瘤坏死因子α(TNF-α),白细胞介素-6(IL-6)以及血浆MDA浓度,并记录3组患者在ICU的滞留时间和拔管时间.结果 与麻醉前(T0)比较,3组TNF-α(ng/L)、IL-6(ng/L)和MDA(mmol/L)在体外循环(cardiopul monary bypass,CPB)后明显升高(P<0.01或P<0.05),S2组在T2(TNF-α15.7±4.1、IL-6 116.5±18.2和MDA 8.5±0.8)、T3(TNF-α22.8±3.6、IL-6 158.9±13.7和MDA 10.2±1.3)时均明显低于S1组T2(TNF-α20.3±4.5、IL-6 141.8±21.3和MDA 10.6±0.9)和T3(TNF-α28.1±3.7、IL-6 175.6±15.1和MDA 12.5±1.4)时(P<0.05),S3组在T2(TNF-α14.4±3.2、IL-6 115.3±19.8和MDA 8.3±0.8)、T3(TNF-α21.0±3.7、IL-6 156.7±14.3和MDA 9.8±1.4)时均明显低于S1组(P<0.05),但S2、S3,组比较差异无统计学意义.S3组患者ICU滞留时间(3.5±0.5)d和术后拔管时间(29.3±3.0)h较S1(2.2±0.5)d,(18.2±2.5)h和S2组(2.4±0.4)d,(19.3±2.8)h明显延长(P<0.05).结论 CPB可促发促炎细胞因子及氧自由基的释放,较大剂量舒芬太尼能抑制心脏手术所致的全身性炎性反应,减少氧自由基的产生,从而减轻再灌注损伤,但达到一定剂量后这种效应并不存在剂量依赖性,且延长患者在ICU的滞留时间.     

舒芬太尼对心脏瓣膜置换术患者血浆炎性细胞因子及丙二醛的影响

Objective To investigate the effect of sufentanil on inflammatory cytokines and MDA of plasma in valve replacement surgery during cardiopulmonary bypass (CPB). Methods Thirty adult patients undergoing valve replacement with cardiopulmonary bypass were randomly divided into 3 groups: Group S1(suifentanil 3 μg/kg), Group S2(sulfentanil 5 μg/kg), Group S3( sulfentanil 10 μg/kg). Blood samples were taken before anesthesia (T1),5 min after opening the thorax (T2), 30 min after aortic clamping(T3), 2 h after aortic declamping( T4), and 24 h (T5) after the operation for determination of plasma levels of tumornecrosis factor(TNF-α), interteukin-6( IL-6 )and MDA. The stage of ICU and the extubation time were recorded. Results Levels of TNF-α, IL-6 and MDA after the CPB in the 3 groups were significantly higher compared with T0(P<0.01). TNF-α(ng/L), IL-6(ng/L) and MDA (mmol/Dlevels at T2,T3 were significantly lower in Group S2 (at T2: TNF-α15.7±4.1 ,IL-6 116.5±18.2 and MDA 8.5±0.8, at T3: TNF-α22.8±3.6,IL-6 158.9±13.7 and MDA 10.2±1.3)than those in Group S1 (at T2: TNF-α20.3±4.5、IL-6 141.8±21.3 and MDA 10.6±0.9, at T3: TNF-α28.1 ±3.7,IL-6 175.6±15.1 and MDA 12.5±1.4). TNF-α, IL-6 and MDA levels at T2, T3 were significantly lower in Group S3(at T2: TNF-α15.7±4.1 JL-6 116.5±18.2 and MDA 8.5±0.8,at T3: TNF-α22.8±3.6、IL-6 158.9±13.7 and MDA 10.2±1.3)than those in Group S1. But levels of TNF-α,IL-6, and MDA in Group S2 were not significantly different compared with those in Group S3. The duration of stay in ICU and time of endotracheal extubation were significantly longer in patients of Group S3 ( 3.5±0.5 ) d, (29.3±3.0) h than those of Group S1 ( 2.2±0.5 )d, (18.2±2.5)handS2(2.4±0.4d,(19.3±2.8) h(P<0.05). Conclusion CPB leads to a proinflammatory response, as well as oxygen free radicals release. Larger dose sufentanil seemed to be effective in reducing CPB-induced inflammatory response and ischemic reperfusion injury, but the effect was not dependent on dose while sufentanil dose reaching some value, at the same time the duration of stay in ICU and time of endotracheal extubation were longer.     

Jejunal mucosal perfusion is well maintained during mild hypothermic cardiopulmonary bypass in humans

In the present study, the effects of mild hypothermic (34 degrees C) cardiopulmonary bypass (CPB) on jejunal mucosal perfusion (JMP), gastric tonometry, splanchnic lactate, and oxygen extraction were studied in low-risk cardiac surgical patients (n = 10), anesthetized and managed according to clinical routine. JMP was assessed by endoluminal laser Doppler flowmetry. Patients were studied during seven 10-min measurement periods before, during, and 1 h after the end of CPB. Splanchnic oxygen extraction increased during hypothermia and particularly during rewarming and warm CPB. JMP increased during hypothermia (26%), rewarming (31%), and warm CPB (38%) and was higher 1 h after CPB (42%), compared with pre-CPB control. The gastric-arterial PCO(2) difference was slightly increased (range 0.04-2.26 kPa) during rewarming and warm CPB as well as 1 h after CPB, indicating a mismatch between gastric mucosal oxygen delivery and demand. None of the patients produced lactate during CPB. We conclude that jejunal mucosal perfusion appears well preserved during CPB and moderate (34 degrees C) hypothermia; this finding is in contrast to previous studies showing gastric mucosal hypoperfusion during CPB. Implications: Jejunal mucosal perfusion increases during mild hypothermic cardiopulmonary bypass (CPB). Intestinal laser Doppler flowmetry, gastric tonometry, and measurements of splanchnic lactate extraction could not reveal a local or global splanchnic ischemia during or after CPB. A mismatch between splanchnic oxygen delivery and demand was seen, particularly during rewarming and warm CPB.     

Blood concentrations of enflurane before, during, and after hypothermic cardiopulmonary bypass

OBJECTIVE: The purpose of this study was to determine blood concentrations of enflurane delivered via a membrane oxygenator during hypothermic cardiopulmonary bypass (CPB) with changes in the input enflurane concentration and temperature and to characterize the pharmacokinetics of enflurane washout during and after CPB. DESIGN: Blood enflurane concentrations were measured by gas chromatography before, during, and after CPB by using mean delivered enflurane concentrations of 0.5% v/v (group 1, n = 5), 0.8% (group 2, n = 7), and 1% (group 3, n = 14). SETTING: The investigation was performed in a teaching hospital setting. PARTICIPANTS: Twenty-six patients undergoing cardiac surgery requiring hypothermic CPB. INTERVENTIONS: Variations in input enflurane concentration in different patients plus blood sampling from the arterial side of the circuit for enflurane assay. MEASUREMENTS AND MAIN RESULTS: Median (25th and 75th percentiles) pre-CPB blood enflurane concentrations were 48 (25-50) mg/L, 52 (47-56) mg/L, and 115 (90-143) mg/L in groups 1 (0.5% v/v), 2 (0.8% v/v), and 3 (1% v/v), respectively. During hypothermia (28 degrees C) corresponding enflurane concentrations were 44 (31-53) mg/L, 56 (45-62) mg/L, and 145 (109-203) mg/L, respectively. For groups 1 and 2, there were no significant changes in blood enflurane compared with the corresponding pre-CPB value. However, for group 3, cooling resulted in a significant increase (p = 0.006) in blood enflurane. In all groups, enflurane concentrations after rewarming were similar to those in the pre-CPB period. CONCLUSIONS: It is concluded that exposure to enflurane concentrations greater than 0.8% during CPB can result in high blood concentrations.     

孕羊低温体外循环对胎羊血流动力学以及碳水化合物代谢的影响

目的 探讨孕羊低温体外循环(CPB)对胎羊血流动力学以及碳水化合物代谢的影响.方法 孕羊20头,随机分成对照组,开胸不建立体外循环;常温CPB组(35～36℃)、浅低温组CPB(32～34℃)和中低温CPB组(28～31℃),建立常规体外循环,转流降温、复温30 min.分别监测孕羊和胎羊的心率、平均动脉压、胎羊脐动脉和颈内动脉的搏动指数(pulse index,PI),孕羊与胎羊血糖、乳酸含量和HCO-3值的变化.结果 母羊和胎羊平均动脉压差异无统计学意义(P＞0.05).浅低温组和中低温组颈内动脉PI值较对照组和常温组显著增高(P＜0.05),脐动脉PI值组间差异无统计学意义,但随体外循环时间的延长而增高.血糖水平胎羊各组间差异无统计学意义(P＞0.05),但中低温CPB组中胎羊显著低于孕羊(P＜0.05).中低温CPB组胎羊血乳酸随时间延长有上升趋势(P＜0.05),而且显著高于孕羊(P＜0.05),但各CPB组间血乳酸差异无统计学意义.结论 孕羊低温体外循环降温时,胎羊心率明显下降,复温后胎羊心率能回复正常,体外循环对胎羊平均动脉压无明显影响,但低温降低胎羊脑部和脐动脉的血流;低温体外循环导致胎羊血糖水平降低,而血乳酸浓度显著增高.

Abstract：

Objective To evaluate effects of maternal hypothermic cardiopulmonary bypass on fetal homodynamic and carbohydrate metabolism. Methods Twenty pregnant sheep were divided into four groups randomly: control group(n=5),normothermic group (35-36℃)(n=5), mild hypothermic group(32-34℃)(n=5) and moderate hypothermic group (28-31℃)(n=5).Thoracotomy was performed without CPB in the control group. Routine CPB was established with different temperature in other three groups. The temperature of normothermic group was kept normal; the left two groups were cooled down to the set point of temperature and then rewarmed back to normal level. Fetal and maternal temperatures, heart rate,mean blood pressure(BP), pulse index (PI) of fetal umbilical artery (UA) and internal carotid artery (CA) were evaluated at cooling and rewarming stages. Biochemical indicators including blood glucose and lactic acid were also measured at the same time. Results There are no differences in mesn BP of ewas and fetal lambs between the different groups (P＞0.05). CA PI value of mild hypothermic group and moderate hypothermic group were significantly higher than those of control group and normothermic group (P＜0.05). There was no difference of UA PI in the four groups, but PI increased following the prolonged duration of CPB. There was no difference change of blood glucose in the four group of fetus, which was significantly lower than the ewe groups. An upward trend of fetal blood lactic acid with time was observed in three CPB groups. The whole level of fetal blood lactic acid was much higher than that of maternal blood of lactic acid. Conclusion Cooling of maternal bypsss decreases fetal heart rate significantly,and fetal heart rate recovered to base line following rewarming phase. There was no signicant effect of CPB on fetal mean BP. However, CPB impacted on the blood flow of fetal brain and umbilical artey. Hypothermia CPB can increase fetal blood glucose and blood lactic acid dramatically.     

Temperature and ventilation after hypothermic cardiopulmonary bypass

Rewarming in the postoperative period after hypothermic cardiopulmonary bypass is often associated with hemodynamic and ventilatory instability. Temperature changes, PaCO2 values, and delivered mechanical ventilation were observed for the first 12 hr in the intensive care unit in 73 patients who had undergone cardiac surgery with hypothermic cardiopulmonary bypass. Mean rectal temperature increased from 34.7 to 38.3 degrees C over the first 8 hr after admission to the intensive care unit (P less than 0.001). The temperature curve was sigmoid rather than linear, and the most rapid rate of temperature increase occurred 2-4 hr after admission. During rewarming, the most common abnormality of PaCO2 on mechanical ventilation was acute respiratory acidosis (PaCO2 greater than 45 mm Hg, pH less than 7.35), which occurred in 42% of patients. This suggests that ventilatory management in the early postoperative period after hypothermic cardiopulmonary bypass should be carefully adjusted to the increased metabolic rate during rapid rewarming.     

Enoximone and warming after hypothermic cardiopulmonary bypass

In a randomized, controlled study of 24 patients undergoing myocardial revascularization, we found that enoximone 0.5 mg kg-1 i.v., followed by 5 micrograms kg-1 min-1, when rewarming after hypothermic cardiopulmonary bypass, prevented subsequent cooling of the periphery after transfer to the intensive care unit. Skin surface temperatures on the foot increased by mean 0.33 (SD 0.5) degree C h-1 in the enoximone group, but decreased by 0.43 (0.4) degree C h-1 in the control group until core temperature had increased to 37 degrees C (P < 0.001); only then did peripheral temperatures begin to increase in the control group. Enoximone did not merely redistribute heat from the core to the periphery. The capacity to transfer heat by the circulation rather than the ability to generate heat in the core appeared to limit body warming in the ICU after hypothermic cardiopulmonary bypass.      

Alcuronium pretreatment attenuates succinylcholine-induced increases in plasma catecholamine concentrations in humans

The effect of alcuronium given before succinylcholine (SCh) on plasma catecholamine concentrations, systolic blood pressure and heart rate was studied in patients anesthetized with enflurane. Twenty-one patients were divided into three groups; six control patients without SCh, eight SCh (1 mg/kg) patients, and seven pretreated patients given alcuronium, 0.04 mg/kg, 5 min before SCh, 1 mg/kg. In the SCh group, mean plasma norepinephrine concentrations, systolic blood pressure, and heart rate significantly increased with onset of fasciculations, whereas in the pretreated patients these variables did not change significantly and no fasciculation was observed. These results indicate that alcuronium pretreatment significantly attenuates the SCh-induced increases in plasma norepinephrine concentrations, systolic blood pressure and heart rate.     

Effect of normothermic versus hypothermic cardiopulmonary bypass on cytokine production and platelet function

BACKGROUND: Proinflammatory cytokines and platelets play a key role in the systemic inflammatory response associated with cardiopulmonary bypass (CPB). The aim of this study was to evaluate the effects of both hypothermic and normothermic CPB on platelet activation, cytokine production, as well as their possible correlations. METHODS: Twenty patients who underwent CABG were randomly assigned into two groups receiving hypothermic and normothermic CPB. Blood samples were obtained through a venous catheter at 6 time points. The following parameters were measured: in vitro platelet aggregation, in vivo platelet activation, complete and differential blood cell counts, plasma soluble P-selectin levels, plasma IL-6, IL-1beta and TNFalpha levels. RESULTS: The results demonstrated that platelet abnormalities could be observed to a greater extent during hypothermic rather than normothermic CPB. The occurrence of in vivo platelet activation was suggested by the presence of a significantly increased percentage of platelets expressing CD62P on their surface, as well as by a decreased in vitro platelet aggregation induced by different agonists. Complete and differential blood cell counts showed no substantial decrease in platelet number without differences between groups. The results obtained also showed the presence of a significant release of sP-selectin during CPB, as well as a more pronounced increase of plasma sP-selectin levels in patients undergoing hypothermic compared to normothermic CPB. A comparison of cytokine levels demonstrated a significant elevation of plasma IL-6 levels during either hypothermic or normothenmic CPB, paralleling the neutrophil rise, while no differences were observed for TNF-alpha levels. Conversely, plasma IL-1beta levels were significantly elevated during hypothermic, but not during normothermic CPB. CONCLUSIONS: Hypothermic CPB is responsible for a greater platelet activation and endothelial dysfunction than normothermic CPB, leading to more profound changes in the hemostatic and inflammatory systems, which, in turn, might be responsible for the higher incidence of postoperative complications reported during hypothermic CPB.     

Effect of rewarming speed during hypothermic cardiopulmonary bypass on cerebral pressure-flow relation

BACKGROUND: Cerebral blood flow is less dependent on arterial blood pressure during hypothermic cardiopulmonary bypass (CPB) compared to warm CPB. Fast rewarming has a more pronounced effect on cognitive performance in the elderly and causes an increased arterio-jugular oxygen content difference. We studied the effect of rewarming and rewarming speed on cerebral pressure-flow relation in adult patients undergoing elective coronary artery bypass surgery with mild hypothermic CPB. METHODS: Fifty patients were randomly assigned to either a slow rewarming strategy (0.24 degrees C/min) or a fast rewarming strategy (0.5 degrees C/min). Cerebral pressure-flow relation was assessed by a transcranial Doppler derived index for cerebral pressure-flow relation (Pressure-flow Index, PFI). The effect of rewarming speed on cerebral pressure-flow relation was assessed by comparing the absolute PFI value after rewarming between the two treatment groups. RESULTS: The mean PFI decreased significantly from 0.73 (standard deviation: 0.28) before rewarming to 0.54 (0.35) after rewarming in the slow rewarming group and from 0.63 (0.29) to 0.48 (0.30) in the fast rewarming group. Absolute PFI after rewarming was not significantly different (mean PFI difference = 0.06; 95% CI = - 0.13; 0.26) between both rewarming strategies. CONCLUSION: Rewarming from mild hypothermic CPB might result in pressure-dependent cerebral blood flow velocity but rewarming speed did not aggravate the effect of rewarming on pressure-flow dependency.     

Effect of cardiopulmonary bypass on pulmonary clearance of adrenomedullin in humans

BACKGROUND: Adrenomedullin is a potent vasodilatory peptide and its plasma concentration increases after cardiopulmonary bypass. We analyzed the contribution of the lung to the disposition of adrenomedullin before and after cardiopulmonary bypass in humans. METHODS: Thirty-five patients undergoing cardiac surgery with cardiopulmonary bypass were studied. Bloods were sampled from the pulmonary artery and left atrium at the following times: prior to systemic heparinization, during pulmonary reperfusion and after cardiopulmonary bypass. Plasma concentrations of total and mature adrenomedullin were measured using an immunoradiometric assay kit specific for human adrenomedullin. Intermediate adrenomedullin was calculated as the difference between total adrenomedullin and mature adrenomedullin. RESULTS: Before cardiopulmonary bypass, mature and intermediate adrenomedullin concentrations were reduced by the pulmonary circulation by approximately 30% and 20%, respectively. However, these effects were not observed during pulmonary reperfusion. Mature, but not intermediate, adrenomedullin was reduced after cardiopulmonary bypass. Furthermore, pulmonary clearance quantity of mature adrenomedullin was significantly enhanced after cardiopulmonary bypass. CONCLUSION: These results indicate that cardiopulmonary bypass temporally impairs the pulmonary clearance of mature and intermediate adrenomedullin, but clearance of mature, not intermediate adrenomedullin is enhanced after cardiopulmonary bypass.     

Pancuronium requirements during hypothermic cardiopulmonary bypass in man

Eight patients were studied to determine the changes in pancuronium requirements during hypothermic cardiopulmonary bypass. They were anaesthetised with fentanyl as the principal agent, ventilated with oxygen and the neuromuscular junction was monitored using train-of-four stimulation. After a bolus dose of pancuronium an infusion was used to maintain the first twitch of the train-of-four at 5-15 per cent of control. Before bypass the mean pancuronium infusion rate was 0.52 (SD 0.16) micrograms/kg/min. There was a small, brief increase in requirement with the initiation of bypass to 0.62 (SD 0.38) micrograms/kg/min, which was followed by a decrease of more than 80 per cent during hypothermia to 0.08 (SD 0.03) micrograms/kg/min. Rewarming was associated with a rapid increase in requirement to 0.64 (SD 0.17) micrograms/kg/min, which decreased to 0.33 (SD 0.23) micrograms/kg/min when normothermia was re-established.     

Effect of hemodilution on the adequacy of cerebral perfusion under hypothermic cardiopulmonary bypass

OBJECTIVE: Open heart surgery without transfusion has been performed even in children. However, the critical limit of the hemoglobin level has not yet been ascertained. Here, we have assessed experimentally the effect of the hemoglobin level on brain metabolism under hypothermic cardiopulmonary bypass. METHODS: Brain tissue pH was measured in 14 rabbits that were put on bypass with a different degree of hemodilution. Cardiopulmonary bypass was started at 37 degrees C and cooled down to 25 degrees C. After maintaining the bypass at 25 degrees C for 60 minutes, the animal was rewarmed to 37 degrees C for 30 minutes and then kept on-bypass for another 30 minutes. The perfusion flow was maintained as 10 ml/kg/min. RESULTS: The lowest hemoglobin level in each rabbit was from 2.5 through 8.5 g/dl. During hypothermic bypass, brain tissue pH increased from 7.21 +/- 0.16 (mean +/- SD, at the normothermic baseline) to 7.55 +/- 0.27 except 2 cases (6.91 +/- 0.16) whose hemoglobin level was lower than 3.0 g/dl. The brain tissue pH after 60 minutes on hypothermic bypass had a good correlation with the hemoglobin level (r = 0.831). After rewarming for 60 minutes, the brain tissue pH was decreased to 7.18 +/- 0.31. In 4 rabbits with less than 4.0 g/dl of hemoglobin, the brain tissue pH (6.67 +/- 0.24) was lower than the baseline level. In the other 10 rabbits, the brain tissue pH (7.22 +/- 0.16) was almost the same as the baseline level. The correlation coefficient between the brain tissue pH and the hemoglobin level after rewarming for 60 minutes was 0.778. CONCLUSIONS: These results indicated that severe hemodilution in cardiopulmonary bypass promoted acidosis in brain even during hypothermia.     

Vecuronium and atracurium infusions during hypothermic cardiopulmonary bypass

Two similar groups of patients undergoing coronary artery bypass grafting received either atracurium or vecuronium infusions for neuromuscular blockade. Both groups demonstrated a marked reduction in neuromuscular blocking requirements during hypothermic bypass at 30 C. The ratio of the dose rates at 30 C to that at 37 C was significantly less with vecuronium (p less than 0.01).     

Effect of cardiopulmonary bypass on plasma levels of nifedipine

Blood levels of many medications are acutely lowered by cardiopulmonary bypass (CPB). Because nifedipine is often used to provide protection from coronary ischemia, a determination of the effect of CPB on plasma nifedipine levels might help to determine the potential clinical benefit of nifedipine during and after bypass. Four samples of blood were drawn from each of eight patients undergoing cardiac surgery: one before, two during, and one after CPB. Although plasma levels of nifedipine declined during and after bypass (P less than 0.05, analysis of variance), the time-course and slope of the decline indicate that this was an effect of normal metabolism of the drug rather than an effect of physiologic changes occurring during CPB. An important additional finding was that the majority of patients had subtherapeutic levels of nifedipine before bypass, suggesting that additional nifedipine given during and after surgery might be of benefit. The effect of the CPB circuit itself was also examined in vitro by mixing nifedipine into a pump prime solution that was then recirculated with 2 U of outdated blood while levels of nifedipine were measured for 3 h. Plasma levels did not change in either a CPB circuit exposed to light or kept in a darkened room.     

Effect of cardiopulmonary bypass on serum procalcitonin and C-reactive protein concentrations

We have measured serum procalcitonin (PCT) concentrations after cardiac surgery in 36 patients allocated to one of three groups: group 1, coronary artery bypass grafting (CABG) with cardiopulmonary bypass (CPB) (n = 12); group 2, CABG without CPB (n = 12); and group 3, valvular surgery with CPB (n = 12). Serum PCT and C-reactive protein (CRP) concentrations were measured before operation, at the end of surgery and daily until postoperative day 8. Serum PCT concentrations increased, irrespective of the type of cardiac surgery, with maximum concentrations on day 1: mean 1.3 (SD 1.8), 1.1 (1.2) and 1.4 (1.2) ng ml-1 in groups 1, 2 and 3, respectively (ns). Serum PCT concentrations remained less than 5 ng ml-1 in all patients. Concentrations returned to normal by day 5 in all groups. To determine the effect of the systemic inflammatory response (SIRS) on serum PCT concentrations, patients were divided post hoc, without considering the type of cardiac surgery, into patients with SIRS (n = 19) and those without SIRS (n = 17). The increase in serum PCT was significantly greater in SIRS (peak PCT 1.79 (1.64) ng ml-1 vs 0.34 (0.32) ng ml-1 in patients without SIRS) (P = 0.005). Samples for PCT and CRP measurements were obtained from 10 other patients with postoperative complications (circulatory failure n = 7; active endocarditis n = 2; septic shock n = 1). In these patients, serum PCT concentrations ranged from 6.2 to 230 ng ml-1. Serum CRP concentrations increased in all patients, with no differences between groups. The postoperative increase in CRP lasted longer than that of PCT. We conclude that SIRS induced by cardiac surgery, with and without CPB, influenced serum PCT concentrations with a moderate and transient postoperative peak on the first day after operation. A postoperative serum PCT concentration of more than 5 ng ml-1 is highly suggestive of a postoperative complication.