Whole body oxygen consumption after hypothermic cardiopulmonary bypass

Whole body oxygen consumption and the substrate for energy production during the post-bypass period have not been clarified. We hypothesized that the substrate composition for energy production during post-bypass period might be different from that during pre-bypass period because of surgical diabetic state induced by hypothermic cardiopulmonary bypass (CPB). We measured whole body oxygen consumption, carbon dioxide production and respiratory quotient by the gas exchange method using the Datex Deltatrac before and after hypothermic cardiopulmonary bypass. We also measured oxygen consumption by Ficks principle. Whole body oxygen consumption (P 0.001) and carbon dioxide production (P 0.05) increased significantly above pre-CPB values after the termination of CPB. Respiratory quotient (P 0.01) decreased significantly below pre-CPB values after the termination of CPB. We conclude that oxygen consumption increased significantly above pre-bypass values after the termination of hypothermic cardiopulmonary bypass at least under the fentanyl, diazepam, chlorpromazine anesthesia with continuous infusion of nitroglycerin and nicardipine. The changes in respiratory quotient suggest a relatively higher ratio of lipid metabolism for energy production during post-bypass period.(Maruyama K, Hashimoto H, Nakamura K, et al.: Whole body oxygen consumption after hypothermic cardiopulmonary bypass. J Anesth 7: 1–7, 1993)     

体外循环术后早期氧动力学变化

目的：观察体外循环术后病人早期氧动力学变化。方法：１９例病人分别于术前、术毕及术后１２、２４、４８、７２和９６小时测定全身氧供给（ＤＯ２）、氧消耗（ＶＯ２）及氧摄取率（ＥｘｔＯ２）等。结果：存活与死亡两组病人术毕始ＶＯ２、ＥｘｔＯ２即明显增加，ＤＯ２升高不显著。２４小时后两组ＤＯ２均明显升高，存活组ＶＯ２、ＥｘｔＯ２恢复至术前水平，ＶＯ２对ＤＯ２呈非氧供依赖关系；死亡组则ＶＯ２、ＥｘｔＯ２仍显著增加，呈氧供依赖关系，且伴有血乳酸浓度升高。结论：氧供依赖关系的出现反映了组织氧债存在及微循环功能的失调。     

Pharmacokinetics of ketamine during hypothermic cardiopulmonary bypass in cardiac patients

Cardiopulmonary bypass (CPB) makes prediction of any drug concentration diffcult because both hypothermia and hemodilution can alter the pharmacokinetics of the drug. Eleven patients undergoing cardiac surgery under CPB were anesthetized with continuous infusion of ketamine combined with intermittent administration of droperidol and fentanyl. The infusion rate of ketamine was 2 mg·kg⁻¹·hr⁻¹ following a bolus administration of 1.5 mg·kg⁻¹ for the induction of anesthesia. Blood concentrations of ketamine and its main metabolite, norketamine, were measured at 0, 30, and 60 min after the start of and the end of CPB, and 0, 1, 2, and 24 h after the cessation of ketamine infusion. Hypothermia increased blood ketamine levels during CPB, but the norketamine levels did not change. Although acute hemodilution would decrease blood ketamine levels, their levels were already significantly increased at 30 min after CPB. Hypothermic factors have a more kinetically important role during CPB than hemodilution. Increases in blood norketamine levels following rewarming indicate that hypothermia could impair ketamine metabolism in the liver. Further increase in the plasma concentration of ketamine until 30 min after the end of CPB might be due to blood transfusion containing ketamine from the CPB reservoir.     

Thiopentone levels during cardiopulmonary bypass

Plasma total and unbound concentrations of thiopentone were investigated during exponentially decreasing infusions in seven patients undergoing cardiopulmonary bypass. Total plasma thiopentone concentrations reached a plateau (10.2, SD 2.1 micrograms/ml) soon after the initial bolus dose and commencement of the infusion. Concentrations were maintained until the onset of cardiopulmonary bypass, whereupon total plasma thiopentone concentration fell abruptly to 50.0 (SD 5.8) percent of the prebypass level. The unbound fraction of thiopentone increased from 16.6 (SD 1.9) percent before bypass to a maximum of 29.3 (SD 5.6) percent during bypass (p less than 0.01), decreased to 22.9 (SD 3.3) percent at the end of bypass (p less than 0.01), but was still elevated 5-7 hours later (20.5, SD 2.5 percent). The result of the changes in binding was a smaller decline in unbound thiopentone concentration at the onset of bypass to 76.4 (SD 15.7) percent of the prebypass level. Also, unbound levels returned to the prebypass level by the end of bypass, whereas total levels remained low.     

Propofol—fentanyl anaesthesia for coronary artery surgery and cardiopulmonary bypass

A two-stage propofol infusion combined with fentanyl was used to maintain anaesthesia during coronary artery surgery in patients with good ventricular function. Whole blood propofol concentrations were measured at frequent intervals; plasma protein binding was measured before, during and after cardiopulmonary bypass. An initial infusion rate of 10 mg/kg/hour provided good protection from the pressor response to sternotomy. A predictable steady state concentration was achieved in the prebypass period with a maintenance infusion rate of 3 mg/kg/hour. The onset of bypass resulted in a small decrease in propofol concentration as a result of haemodilution. Induced hypothermia resulted in an increase in propofol concentration which returned rapidly to the prebypass steady state value during rewarming. The free propofol fraction increased during cardiopulmonary bypass. No patient had any recall of operative events or required inotropic support during weaning from bypass.     

Propofol: bolus or continuous infusion

Forty patients undergoing vaginal termination of pregnancy were randomly allocated to receive a propofol anaesthetic using either a repeat bolus or infusion technique. The Ohmeda 9000 Infusion Pump was used in the study. Patients in the infusion group recorded significantly longer induction times, greater maintenance doses and prolonged immediate recovery characteristics. Both techniques offered cardiovascular stability but no advantages were demonstrated for the infusion technique over a conventional repeat bolus method.     

常温和低温心肺转流期间门静脉血流量及氧代谢的变化

目的：研究常温和低温心肺转流（CPB）期间门静脉血流量（PBF）和氧代谢的变化。方法：测定11号杂种犬在常温（N组）或低温（H组）CPB期间PBF和氧代谢指标。结果：CPB中低温组SpO2升高，PDO2、PVO2降低（P＜0．05或P＜0．01）；常温组PpO2、PDO2降低，而PERO2和PBF升高（P＜0．05或P＜0．01）。CPB后两组SaO2、PaO2、SpO2、PpO2、PBF、PDO2均有不同程度的降低（P＜0．05或P＜0．01），而PERO2明显升高（P＜0．01），常温组PVO2减少（P＜0．05）。两组相比，CPB中低温组PaO2、SaO2、SpO2高于常温组，PVO2、PERO2、PBF低于常温组（P＜0．05或P＜0．01）。CPB后低温组SaO2、PDO2、PVO2和PBF都高于常温组（P＜0．05）。结论：常温和低温CPB期间门脉系统都存在氧代谢障碍，但常温CPB期间PBF、门脉组织氧利用明显优于低温CPB，CPB后PBF、门脉组织氧代谢低温组优于常温组。     

Propofol combined with nitrous oxide-oxygen for induction and maintenance of anaesthesia

After a bolus of 2 mg/kg, propofol was given by continuous infusion (150 micrograms/kg/minute for 30 minutes and then 100 micrograms/kg/minute) supplemented with nitrous oxide for anaesthesia during ear surgery in 12 patients. Cardiovascular changes were not significant except for a decrease in heart rate after 60 minutes. Acid-base balance was unaffected by the amount of fatty emulsion. Cortisol levels showed a nonsignificant decrease during the prolonged administration of propofol but had recovered completely by one hour following anaesthesia. Mean blood concentrations of propofol were 10.5 micrograms/ml (SEM 1.2) at the onset of unconsciousness, between 3.4 and 4.5 micrograms/ml during continuous infusion and 2.9 micrograms/ml (SEM 0.3) on awakening. Patients opened their eyes 6 minutes (SEM 1) after discontinuation of the infusion, and were responsive at 7.5 minutes (SEM 0.5), which suggests that propofol infusion can be used safely for surgery of 2 hours' duration.     

中度低温体外循环对大鼠认知功能影响的初步探讨

目的　观察大鼠中度低温体外循环(CPB)后认知功能变化。方法　雄性SD大鼠随机分为CPB组(n =6 )、假CPB组(Sham组,n =4 )及单纯麻醉组(n =4 )。所有动物在咪唑安定、芬太尼麻醉后经口插管控制呼吸。CPB组和假手术对照组置入颈静脉流出管和尾动脉输入管,肝素抗凝(5 0 0U/kg)。CPB组采用中度低温CPB(2 6℃～2 8℃) ,经尾动脉灌注、颈静脉右心房-腔静脉引流,灌流量16 0ml·kg-1·min-1,总转流时间2h。Sham组除不经历CPB外,其余操作同CPB组相同,单纯麻醉组除麻醉机械通气外不经历任何手术操作。术后3d采用旷场分析(Openfieldtest )观察5min内动物的跨格次数、中央格停留时间、站立次数和排便粒数,分析术后大鼠兴奋性、紧张程度及空间认知功能变化。结果　术后3d ,CPB组大鼠兴奋性、紧张程度及空间认知功能与Sham组和单纯麻醉组相比显著降低。结论　中度低温CPB可引起大鼠认知功能损害。     

体外循环心脏直视手术中红细胞携氧能力的临床观察

目的　观察体外循环 (CPB)心脏直视手术中红细胞携氧能力的变化。方法　观察 1 5例择期心脏手术病人的红细胞形态、P5 0和红细胞内 2 ,3 二磷酸甘油酸 (2 ,3 DPG)的含量在围转流期的变化。结果　红细胞在CPB期间发生畸形变 ;红细胞内 2 ,3 DPG的浓度在CPB结束时较术前明显增加[(7 82± 1 5 5 ) μmol/ml对 (6 39± 1 2 7) μmol/ml,P <0 0 5 ];P5 0在转流前后无明显变化。 结论　尽管红细胞的形态在CPB期间有所改变 ,但其携氧能力变化不明显。     

异丙酚在心脏瓣膜置换术中对氧供、氧耗、氧摄取率及氧合状态的影响

目的：观察异丙酚在心脏瓣膜置换术中对氧供（ＤＯ２）,氧耗（ＶＯ２）,氧摄取率（ＥＲＯ２）及氧合状态的影响。方法：２０例心脏瓣膜置换术病人随机分为两组。组麻醉诱导与维持用异丙酚,对照组用咪唑安定。观察体外循环（ＣＰＢ）期间ＤＯ２,ＶＯ２,ＥＲＯ２,混合静脉血氧饱和度（ＳＶＯ２）及动脉血乳酸（ＡＢＬ０的变化。结果：（１）组内各时点ＤＯ２无明显变化,复温后观察组ＥＲＯ２增加非常显著;降温开始及复温后观察     

Isoflurane and hypothermic cardiopulmonary bypass: vasodilation without metabolic effects

During cardiopulmonary bypass, isoflurane may have beneficial effects on systemic oxygen uptake and vascular resistance. For this reason, the effects of isoflurane during low-flow (1.6 L/min/m2), hypothermic (27 degrees to 29 degrees C) cardiopulmonary bypass on systemic hemodynamics and oxygen uptake were studied in 20 patients in a cross-over experiment. Mean arterial and central venous pressures were measured during two consecutive periods of 10 minutes' duration. Blood samples were aspirated at the end of each period from the arterial and venous lines and analyzed for oxygen content. The concentration of isoflurane in the arterial samples was also determined. Systemic oxygen uptake and vascular resistance were calculated. Isoflurane had no significant effect on systemic oxygen uptake. Significant inverse relationships between blood isoflurane concentration and both mean arterial pressure and systemic vascular resistance were found. It is concluded that isoflurane is a vasodilator under the abnormal conditions of hypothermic cardiopulmonary bypass, but has no effect on systemic oxygen uptake.     

孕羊深低温体外循环对胎羊温度和血流动力学及血气的影响

目的探讨孕羊深低温体外循环(CPB)对胎羊温度、血流动力学和血气的影响。方法5头健康怀孕山羊常规建立CPB,转流降温、复温各1 h。监测孕羊和胎羊的温度、心率、平均动脉压、血气值。结果孕羊最低温度(17．4±1．5)℃,胎羊最低温度(24．6±1．5)℃。降温期胎羊温度始终高于孕羊温度,复温期孕羊-胎羊温差逆转,转流结束胎羊温度低于孕羊温度。降温期胎羊心率逐渐减慢,复温期不能恢复正常心率。低温转流15 min,胎羊pH值从转流开始的7．30± 0．03降到7．17±0．07(P<0．05)、PO_2从转流开始的(32．5±4．0)mmHg(1 mmHg=0．133 kPa)降到(17．5±3．0)mm Hg(P<0．05),PCO_2从转流开始的(44．8±2．2)mm Hg升到(56．8±5．1)mm Hg(P<0．05),BE值从转流开始的(-3．2±0．6)升到(-5．7±1．3)(P<0．05),此后血气值进一步恶化,复温阶段胎羊血气值也没有好转。CPB结束胎羊存活率为60％。结论孕羊深低温CPB 影响胎盘的热交换和气体交换功能,对胎羊存活不利。     

Effects of mild hypothermic cardiopulmonary bypass on blood viscoelasticity in coronary artery bypass grafting patients

The purpose of this study was to determine the changes in blood viscoelasticity during and after coronary artery bypass grafting (CABG) and to identify correlations between blood viscoelasticity and patients' age, duration of cardiopulmonary bypass (CPB), and cross-clamp time. After Institutional Review Board approvals, patients (n = 10) who were subjected to mild hypothermic CPB were included in this study. Viscosity and elasticity were measured at strains of 0.2, 1, and 5 using a Vilastic-3 Viscoelasticity Analyzer. Arterial blood samples were collected pre-CPB, on normothermic CPB, hypothermic CPB, after rewarming, and after CPB. Viscosity and elasticity at strains of 0.2 and 1 were altered significantly during and after CPB compared to the pre-CPB (p < 0.01). In particular, elasticity of blood was diminished during normothermic bypass and could not be recovered after CPB (p < 0.01). Although there were strong correlations between blood viscoelasticity, duration of CPB, and cross-clamp time on normothermic CPB, only the patients' age showed a positive correlation between viscosity (r = 0.61, p = 0.05), and elasticity (r = 0.89, p < 0.001) after CPB. These results suggest that mild hypothermic CPB alters the blood viscoelasticity during and after CABG.     

中低温减少体外循环下瓣膜置换术中丙泊酚剂量研究

目的以脑电频谱指数(BIS)为参考,探讨不同温度体外循环(CPB)下行瓣膜置换术患者丙泊酚的合适剂量。方法选择60例ASAⅡ-Ⅲ级择期行瓣膜置换术患者,根据术中最低鼻咽温分为2组:浅低温组(32℃,n=30)和中低温组(28℃,n=30)。术中调整丙泊酚剂量,保持BIS值处于40～60。分别于转机前(T1)、阻断升主动脉前(T2)、阻断升主动脉(T3)、开放升主动脉(T4)和停机后(T5)5个时间点,记录患者BIS值和丙泊酚剂量。结果患者均存活出院。组N患者转机前、停机后丙泊酚剂量分别为(4.6±1.3)mg/kg.hr和(4.3±1.6)mg/kg.hr,组H分别为(4.3±1.3)mg/kg.hr和(4.0±1.5)mg/kg.hr,差异均无统计学意义(P>0.05)。CPB转机开始后2组丙泊酚用量均较转机前明显减少,差异具有统计学意义(组N为2.4±1.2 mg/kg.hr,组H为1.2±0.5mg/kg.hr,P<0.01)。T3时间点中低温组较浅低温组下降明显,差异具有统计学意义(P<0.01)。无1例发生术中知晓现象。结论中低温CPB下行瓣膜置换术时,转机开始后应适量减少丙泊酚剂量。     

浅低温体外循环心脏跳动中施术对心肌保护的实验研究

目的　探讨浅低温体外循环（CPB）心脏跳动中心内直视手术对心肌保护的效果。方法　16只健康山羊随机均分为实验组（浅低温心跳组）和对照组（中度低温心停组）。分别在转机后即刻、CPB120、130、150min，取冠状静脉窦血，测定血清中丙二醛（MDA）、超氧化物歧化酶（SOD）、肌酸激酶同工酶（CK-MB）、乳酸脱氢酶（LDH）的含量，并取左室心肌组织观察心肌超微结构的改变。结果　对照组再灌注后MDA、CK-MB、LDH明显升高，SOD明显降低，与实验组相同时点相比，差异有显著意义（P＜0.01）。心肌细胞超微结构观察见对照组变化明显，实验组基本不变。结论　浅低温体外循环心脏跳动中行心内直视手术避免了心肌缺血再灌注损伤过程，有很好的心肌保护效果。