Balloon pump-induced pulsatile perfusion during cardiopulmonary bypass does not improve brain oxygenation.

BACKGROUND: Whether pulsatile flow offers substantial advantages for brain protection during cardiopulmonary bypass is controversial. The purpose of this study is to determine whether differences exist between pulsatile and nonpulsatile bypass concerning the effects on internal jugular venous saturation and on the state of regional cerebral oxygenation during normothermia. METHODS: Twenty-two patients undergoing elective coronary artery bypass grafting were randomly divided into 2 groups: group 1 (n = 11) received nonpulsatile perfusion during cardiopulmonary bypass and group 2 (n = 11) received pulsatile perfusion during bypass. We used an intra-aortic balloon pump to generate pulsatility. A spectrophotometric probe (INVOS 3100R, Somanetics, Troy, Mich) was used to assess the state of regional cerebral oxygenation. A 4F fiberoptic oximetry oxygen saturation catheter was inserted into the right jugular bulb to monitor jugular venous oxygen saturation. Hemodynamic variables, arterial and jugular venous blood gases, and regional cerebral oxygenation were measured at 7 times points. RESULTS: In both groups, jugular venous oxygen saturation decreased at the early stage of the cardiopulmonary bypass (P =.03). Five patients in group 1 and 6 in group 2 had a jugular venous oxygen saturation of less than 50%. In both groups, the regional cerebral oxygenation value decreased during cardiopulmonary bypass (P =.04). CONCLUSIONS: The present results showed that pulsatility generated through the use of intra-aortic balloon pumping did not produce any beneficial effects on jugular venous oxygen saturation and regional cerebral oxygenation at normothermia.     

Low arterial pressure during cardiopulmonary bypass in piglets does not decrease fluid leakage

BACKGROUND: Cardiopulmonary bypass (CPB) is associated with increased fluid filtration occasionally leading to post-operative organ dysfunction. One of the factors determining fluid filtration is the capillary hydrostatic pressure which depends on arterial pressure, venous pressure and pre- to post-capillary resistance ratio. The purpose of this study was to assess whether lowering of the mean arterial pressure and/or the central venous pressure could reduce fluid extravasation during normothermic and hypothermic CPB. METHODS: Seven piglets were given nitroprusside to a mean arterial pressure of 35-40 mmHg during 60 min of normothermic and 90 min of hypothermic CPB (LP group). They were compared with a control group (C group, n = 7) without blood pressure interventions. Blood chemistry, net fluid balance, plasma volume, colloid osmotic pressure in plasma and interstitial fluid, intravascular protein masses, fluid extravasation rate and total tissue water content were measured or calculated. RESULTS: Mean arterial pressure was significantly lower in the LP group than in the C group during CPB. Plasma volume tended to increase in the LP group (P > 0.05), but remained essentially unchanged in the C group. Net fluid balance in the LP group was more positive than in the C group 30 min after CPB start [1.02 (0.15) vs. 0.56 (0.13) ml/kg/min (Mean (SEM) P < 0.05)]. Fluid extravasation rate tended to be higher in the LP group and total tissue water content of the gastrointestinal tract, left myocardium and skin was significantly elevated compared with the C group. CONCLUSION: During CPB, lowering of the mean arterial pressure using nitroprusside did not reduce fluid extravasation. On the contrary, the data may implicate an increase in edema formation during low pressure CPB.     

Cerebral blood flow does not change following sodium nitroprusside infusion during hypothermic cardiopulmonary bypass

Changes in cerebral blood flow (CBF) associated with decreases in mean arterial pressure (MAP) produced by sodium nitroprusside (SNP) infusion were measured by intra-aortic injection of 133Xe in 17 patients during hypothermic cardiopulmonary bypass (CPB). In each patient, CBF was determined at baseline and then again following SNP-induced reduction of MAP. Two groups were studied. In Group I (n = 9), PaCO2 was maintained near 42 mm Hg uncorrected for nasopharyngeal temperature (NPT). In Group II (n = 8), PaCO2 was maintained near 60 mm Hg, uncorrected for NPT. Nasopharyngeal temperature, MAP, pump oxygenator flow, PaO2, and hematocrit were maintained within a narrow range in each patient during both studies. Since the baseline CBF determinations were conducted at the higher MAP in all subjects, we corrected post-SNP CBF data for the spontaneous decline that occurs over time during CPB. In Group I, a reduction in MAP from 76 +/- 9 mm Hg (mean +/- SD) to 50 +/- 6 mm Hg was associated with a reduction in CBF from 17 +/- 5 to 13 +/- 3 ml.100 g.min-1 (P less than 0.01), a decrease that became statistically insignificant once the time correction factor had been applied (16 +/- 4 ml.100 g-1.min-1). In Group II, MAP declined from 75 +/- 5 mm Hg to 54 +/- 5 mm Hg, and CBF declined from 25 +/- 10 to 17 +/- 7 ml.100 g.min-1 (P less than 0.01), but, again, after time correction, the CBF decline was statistically insignificant (22 +/- 8 ml.100 g-1.min-1).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of perfusion flow rate on tissue oxygenation in newborn piglets during cardiopulmonary bypass

BACKGROUND: Our knowledge of the best perfusion flow rate to use during cardiopulmonary bypass (CPB) in order to maintain tissue oxygenation remains incomplete. The present study examined the effects of perfusion flow rate and patent ductus arteriosus (PDA) during normothermic CPB on oxygenation in several organ tissues of newborn piglets. METHODS: The experiments were performed on 12 newborn piglets: 6 with PDA ligation (PDA-L), and 6 without PDA ligation (PDA-NL). CPB was performed through the chest at 37 degrees C. During CPB, the flow rate was changed at 15-minute intervals, ranging from 100 to 250 ml/kg/min. Tissue oxygenation was measured by quenching of phosphorescence. RESULTS: For the PDA-L group, oxygen in the brain did not change significantly with changes in flow rate. In contrast, for the PDA-NL group, oxygen was dependent upon the flow rate. Statistically significant decreases in cortical oxygen were observed with flow rates below 175 ml/kg/min. Within the myocardium, liver, and intestine, there were no significant differences in the oxygen levels between the PDA-L and PDA-NL groups. In these tissues, the oxygen decreased significantly as the flow rate decreased below 150 ml/kg/min, 125 ml/kg/min, and 175 ml/kg/min, respectively. Oxygen pressure in skeletal muscle was not dependent on either PDA ligation or flow rate. CONCLUSIONS: In newborn piglets undergoing CPB, the presence of a PDA results in reduced tissue oxygenation to the brain but not to other organs. In general, perfusion flow rates of 175 ml/kg/min or greater are required in order to maintain normal oxygenation of all organs except muscle.     

Hemodilution elevates cerebral blood flow and oxygen metabolism during cardiopulmonary bypass in piglets

BACKGROUND: Hemodilution continues to be widely used during cardiopulmonary bypass (CPB) for both adults and children. Previous studies with nonbypass models have suggested that an increase in cerebral blood flow (CBF) compensates for the reduced oxygen-carrying capacity; however, this increased CBF is achieved by an increase in cardiac output. We hypothesized that even with the fixed-flow perfusion of CPB, CBF would be increased during hemodilution. METHODS: Two experiments were conducted and analyzed separately. In each experiment, 10 piglets were randomized to two different groups, one with a total blood prime yielding a high hematocrit (25% or 30%), and the other with a crystalloid prime resulting in a low hematocrit (10% or 15%). Animals were cooled with pH-stat strategy at full flow (100 or 150 mL.kg(-1).min(-1)) to a nasopharyngeal temperature of 15 degrees C, a period of low flow (50 mL.kg(-1).min(-1)) preceding deep hypothermic circulatory arrest (45 or 60 minutes), and a period of rewarming at full flow. Cerebral blood flow was measured at the beginning of CPB, at the end of cooling, at the end of low flow, 5 minutes after the start of rewarming, and at the end of rewarming by injection of radioactive microspheres. RESULTS: Mean arterial pressure was significantly greater with higher hematocrit at each time point (p< 0.05). Cerebral blood flow and the cerebral metabolic rate of oxygen decreased during cooling and further during low flow bypass but were significantly greater with lower hematocrit during mild hypothermia and at the end of rewarming (p< 0.05). CONCLUSIONS: Hemodilution is associated with decreased perfusion pressure, increased CBF and increased the cerebral metabolic rate of oxygen during hypothermic CPB.     

Retransfusion of pericardial blood does not trigger systemic coagulation during cardiopulmonary bypass

Objective: During cardiopulmonary bypass (CPB), systemic coagulation is believed to become activated by blood contact with the extracorporeal circuit and by retransfusion of pericardial blood. To which extent retransfusion activates systemic coagulation, however, is unknown. We investigated to which extent retransfusion of pericardial blood triggers systemic coagulation during CPB. Methods: Thirteen patients undergoing elective coronary artery bypass grafting surgery were included. Pericardial blood was retransfused into nine patients and retained in four patients. Systemic samples were collected before, during and after CPB, and pericardial samples before retransfusion. Levels of prothrombin fragment F₁₊₂ (ELISA), microparticles (flow cytometry) and non-cell bound (soluble) tissue factor (sTF; ELISA) were determined. Results: Compared to systemic blood, pericardial blood contained elevated levels of F₁₊₂, microparticles and sTF. During CPB, systemic levels of F₁₊₂ increased from 0.28 (0.25–0.37; median, interquartile range) to 1.10 (0.49–1.55) nmol/l (p = 0.001). This observed increase was similar to the estimated (calculated) increase (p = 0.424), and differed significantly between retransfused and non-retransfused patients (1.12 nmol/l vs 0.02 nmol/l, p = 0.001). Also, the observed systemic increases of platelet- and erythrocyte-derived microparticles and sTF were in line with predicted increases (p = 0.868, p = 0.778 and p = 0.205, respectively). Before neutralization of heparin, microparticles and other coagulant phospholipids decreased from 464 μg/ml (287–701) to 163 μg/ml (121–389) in retransfused patients (p = 0.001), indicating rapid clearance after retransfusion. Conclusion: Retransfusion of pericardial blood does not activate systemic coagulation under heparinization. The observed increases in systemic levels of F₁₊₂, microparticles and sTF during CPB are explained by dilution of retransfused pericardial blood.     

肺动脉灌注低温肺保护液抑制肺内实质细胞凋亡的研究

目的　探讨体外循环中肺动脉灌注低温保护液对肺内实质细胞凋亡的影响。方法　将4 0例行法洛四联症根治术的患儿分为肺保护组和对照组 (各 2 0例 )。肺保护组体外循环期间肺动脉灌注低温肺保护液 ,对照组行常规法洛四联症根治术。 2 0例患儿 (两组各 10例 )术后取右下肺组织活检标本 ,原位末端标记免疫组化染色法检测肺内实质细胞凋亡情况。同时监测围手术期肺功能及临床指标。结果　肺保护组肺内实质细胞凋亡率为 (10± 2 ) % ,而对照组肺内实质细胞凋亡率为 (18± 7) % ,两者比较 ,差异有显著性 (t=- 2 95 ,P <0 0 5 )。肺保护组术后氧指数较对照组高 ,回ICU病房后 0、6和 12h均有显著差异 [分别为 (4 92± 172 )、(4 4 4± 10 4 )、(4 89± 5 8)mmHg和 (36 9± 12 6 )、(347± 10 7)、(340± 119)mmHg ,t =2 5 9,P <0 0 5 ;t=2 88,P <0 0 1;t =5 0 6 ,P <0 0 1];肺保护组呼吸机辅助通气时间短于对照组 [(15± 11)h和 (2 6± 15 )h ,t=- 2 76 ,P <0 0 1]。结论　肺动脉灌注低温保护液可抑制肺组织内实质细胞凋亡 ,减轻体外循环肺损伤     

体外循环中有效的肺动脉灌注方式

目的 探索方便、有效的肺动脉灌注模式,以缓解体外循环心脏术后肺损伤.方法 14只健康家犬模拟临床体外循环肺损伤特点建立动物模型,随机平均分为对照组及灌注组.体外循环期间,分别于实验肺缺血之初及再灌注之前,以15～20 mm Hg(1 mm Hg=0.133 kPa)的灌注压力短时间对灌注组动物实验肺实施改良低钾右旋糖酐保护液灌注;对照组动物无保护液灌注.90 min体外循环肺缺血后,再灌注4 h,行实验肺肺功能变化测定.结果 再灌注后,两组动物实验肺肺功能均有不同程度的恶化.对照组,再灌注后实验肺顺应性及氧合指数均有较大幅度的下降,分别为(30±4)%及(45±5)%,肺血管阻力指数明显上升,幅度为(76±7)%;与对照组比较,灌注组上述指标的变化幅度均明显降低,分别为[(12±2)%,t0.01/2,12=4.885,P＜0.01];[(19±2)%,t0.01/2,12=5.656,P＜0.01];[(28±3)%,t0.01/2,12=6.853,P＜0.01)].结论 应用肺动脉灌注方式可明显减轻体外循环过程中肺组织的损伤,保护肺功能;实验的灌注方式可望方便地应用于临床体外循环心脏手术过程,不会明显干扰既定手术进程.     

Cerebral blood flow and oxygen metabolism during cardiopulmonary bypass with moderate hypothermic selective cerebral perfusion

Cerebral blood flow was measured using transcranial doppler during cardiopulmonary bypass in nine patients with selective cerebral perfusion for surgery of arch aorta (group S). For comparison, 11 adult open heart patients (group C) were also measured. The authors' selective cerebral perfusion at 28 degrees C resulted in moderate hypothermia and antegrade perfusion using independent pumps for three branches. Total flow in the three branches was 500 ml/min. A Labodop DP-100 doppler ultrasound velocimeter was used to measure middle cerebral arterial blood flow velocity. Hemoglobin concentration and oxygen saturation were also measured in arterial and jugular venous blood. The arteriovenous oxygen content difference (Ca-vO2) was calculated and multiplied by the middle cerebral arterial blood flow velocity value, which resulted in the cerebral metabolic rate for oxygen (CMRO2). The cerebral perfusion pressure of group S was lower than in group C, and the arterial carbon-dioxide tension (PaCO2) of group S was higher than in group C during cardiopulmonary bypass. Middle cerebral arterial blood flow velocity values of both groups remained constant before, during and after cardiopulmonary bypass. The CMRO2 decreased during cardiopulmonary bypass and showed no difference between the two groups. The changes in PaCO2 might be significant factors in the increase in cerebral blood flow during selective cerebral perfusion. This study supports the conclusion that, compared with our routine open heart surgery procedures, our selective cerebral perfusion procedures had the same cerebral blood flow and oxygen metabolism during cardiopulmonary bypass.     

含L-精氨酸氧合温血肺动脉持续灌注对肺组织的保护作用

目的 体外循环(CPB)期间观察肺动脉持续灌注氧合血及氧合血内加入L-精氨酸对肺组织的保护作用.方法 45例择期常规行二尖瓣置换术病人纳入临床对照研究,随机分成对照组,常规体外循环;灌注组,肺动脉持续灌注氧合血;加药组,肺动脉持续灌注含L-精氨酸(200 mg/kg)的氧合血;每组各15例.3组病人均采用常规CPB,灌注组和加药组从肺动脉根部持续灌注氧合血至CPB开放主动脉结束.分别在麻醉后、开放主动脉1 h,回ICU 0、6、12、24 h取桡动脉血,采用双抗体夹心酶联免疫吸附试验(ELISA法)测定肿瘤坏死因子(TNF-α)、白细胞介素6(IL-6)、白细胞介素10(IL-10)的表达.征得病人本人及家属同意,于CPB前及停机后30min取1.0 cm×1.0cm×1.0cm右下肺组织.光镜观察肺组织结构变化.结果 45例术中及术后经过顺利,均痊愈出院.开放主动脉后,加药组和灌注组血浆中TNF-α、IL-6水平明显低于对照组(P<0.05),加药组优于灌注组;IL-10水平高于对照组,加药组优于灌注组.对照组光镜下见肺泡间质水肿,肺泡内大量中性粒细胞渗出,细胞核碎裂;灌注组肺泡毛细血管轻度充血,肺间质淋巴细胞浸润;加药组基本保持了正常的肺组织结构.结论 CPB期间持续肺动脉灌注氧合血对肺组织有保护作用;L-精氨酸对肺组织也有保护作用.     

Effects of perfusion pressure on cerebral blood flow and oxygenation during normothermic cardiopulmonary bypass

BACKGROUND: Central nervous system dysfunction after cardiopulmonary bypass (CPB) is an important cause of morbidity and mortality after cardiac surgery. Perfusion pressure (PP) during CPB could be one of the important determinants of cerebral blood flow (CBF). The objective of the present study was to determine the effect of PP on CBF and cerebral oxgenation during normothermic CPB. METHODS: Twelve adult patients undergoing coronary artery bypass graft surgery were randomly assigned to one of two groups based on PP (High and Low group). Patients in High group received phenylephrine immediately after the onset of CPB to maintain PP between 60 and 80 mmHg. Oxyhemoglobin (O2Hb), deoxyhemoglobin (HHb), tissue oxygenation index (TOI), and oxidized cytochrome aa3 (CtOx) were measured by near-infrared spectroscopy, and internal jugular venous bulb blood oxygen saturation (SjvO2) was measured simultaneously. S-100 beta protein concentrations were also measured before and after CPB. RESULTS: SjvO2 in High group increased significantly during CPB. CtOx in Low group decreased significantly during CPB, whereas TOI was unchanged. Although S-100 beta increased significantly at the end of CPB, there was no difference between the groups. CONCLUSIONS: These results suggest that maintaining high PP is benefical for CBF during normothermic CPB.     

Active distal coronary perfusion to prevent regional myocardial ischemia in off-pump coronary artery bypass grafting.

Regional myocardial ischemia during anastomosis in off-pump coronary artery bypass (OPCAB) can occasionally cause hemodynamic instability. To prevent regional myocardial ischemia and stabilize the hemodynamics during the procedure, perfusion of the distal coronary artery to the anastomotic site is necessary as the only reliable method. We have applied an active coronary perfusion method using a servo-controlled pump in selected patients in place of conventional passive perfusion methods (intraluminal shunt and external shunt). We present a case in which the active perfusion method proved useful in avoiding regional myocardial ischemia. A 74-year-old male patient with triple-vessel coronary disease underwent OPCAB for unstable angina. During revascularization of the main right coronary artery, the hemodynamics collapsed due to regional myocardial ischemia. As soon as the distal coronary artery was perfused at a high flow rate around 80 ml/min, the hemodynamics stabilized and the operation was completed successfully. This active coronary perfusion method in OPCAB is particularly useful in cases in which regional myocardial ischemia cause hemodynamic instability.     

Distribution of coronary blood flow during cardiopulmonary bypass in pigs

The distribution of coronary blood flow during cardiopulmonary bypass in pigs was estimated by the radioactive microsphere method. Total flows during bypass were inadequate or marginal under the conditions of the experiment. The endocardial side of the myocardium was markedly underperfused when the heart remained in ventricular fibrillation during bypass. Vasodilation (with dipyridamole) or perfusion with a pulsatile pump improved the gradient, although distribution still greatly favored the epicardial side. Only when the heart remained in normal sinus rhythm during bypass was the normal distribution maintained. The implications of these experiments for explaining the lesion of left ventricular hemorrhagic necrosis are discussed.     

Cerebral blood flow during cardiopulmonary bypass in man: effect of arterial filtration.

Cerebral blood flow was recorded in 39 patients undergoing cardiac surgery by intraarterial injection of xenon 133. There were three subgroups of patients: 10 patients had a 20 micron arterial filter (Johnson) and 11 a 40 micron filter (Pall), and 18 had no arterial filtration. All patients had a 40 micron (Pall) filter in the coronary suction line. Significant changes in cerebral blood flow occurred during extracorporeal circulation (p less than 0.0001). For all patients cerebral blood flow increased from a resting prebypass level of 30 to 46 and 57 ml/100 g a minute during initial and stable hypothermic extracorporeal circulation respectively. Both measurements were obtained at 26 degrees C and the recordings were made on average 12 and 55 minutes after the extracorporeal circulation was started. During rewarming cerebral blood flow increased to 64, 53, 41, and 36 ml/g a minute at 31 degrees, 33 degrees, 35 degrees, and 37 degrees C respectively, and when measured four and 16 minutes on average after bypass it was 44 and 41 ml/100 g a minute. This general brain hyperperfusion was noticed in all patients with a high enough mean blood pressure to produce hyperaemia. Interposing 20 and 40 micron arterial filters reduced cerebral blood flow but did not prevent this hyperaemia. The cerebral autoregulation, which maintains a constant cerebral blood flow within wide limits of perfusion pressures, was not affected by arterial filtration. The lower limit of blood pressure at which a further reduction in blood pressure was followed by a reduction in cerebral blood flow was around 60 mm Hg in all three groups.     

Permissive hypotension does not reduce regional organ perfusion compared to normotensive resuscitation: animal study with fluorescent microspheres

Introduction

The objective of this study was to investigate regional organ perfusion acutely following uncontrolled hemorrhage in an animal model that simulates a penetrating vascular injury and accounts for prehospital times in urban trauma. We set forth to determine if hypotensive resuscitation (permissive hypotension) would result in equivalent organ perfusion compared to normotensive resuscitation.

Methods

Twenty four (n=24) male rats randomized to 4 groups: Sham, No Fluid (NF), Permissive Hypotension (PH) (60% of baseline mean arterial pressure - MAP), Normotensive Resuscitation (NBP). Uncontrolled hemorrhage caused by a standardised injury to the abdominal aorta; MAP was monitored continuously and lactated Ringer’s was infused. Fluorimeter readings of regional blood flow of the brain, heart, lung, kidney, liver, and bowel were obtained at baseline and 85 minutes after hemorrhage, as well as, cardiac output, lactic acid, and laboratory tests; intra-abdominal blood loss was assessed. Analysis of variance was used for comparison.

Results

Intra-abdominal blood loss was higher in NBP group, as well as, lower hematocrit and hemoglobin levels. No statistical differences in perfusion of any organ between PH and NBP groups. No statistical difference in cardiac output between PH and NBP groups, as well as, in lactic acid levels between PH and NBP. NF group had significantly higher lactic acidosis and had significantly lower organ perfusion.

Conclusions

Hypotensive resuscitation causes less intra-abdominal bleeding than normotensive resuscitation and concurrently maintains equivalent organ perfusion. No fluid resuscitation reduces intra-abdominal bleeding but also significantly reduces organ perfusion.

     

深低温低流量灌注与降温期血气管理对乳猪脑保护的对照研究

目的：在深低渐体外循环中比较降温期pH稳态血气管理和深低温阶段低流量灌注对脑保护的作用能力。方法：24头乳猪根据不同的体外循环脑保护处理方法分成4组，A组：深低温停循环、降温期alpha稳态血气管理；B组：深低温停循环、降温期pH稳态血气管理；C组：深低温低流量、降温期alpha稳态血气管理；D组：深低温低流量、降温期pH稳态血气管理。比较不同脑保护方法和体外循环阶段对脑血流（CBF）、脑氧代谢率（CMRO2）、脑乳酸含量、脑水含量和脑电图（EEG）的影响。结果：B组、D组降温末CBF均高于A组、C组；而CMRO2则低于A组、C组；B组、D组降温期EEC平坦波出现早。C组、D组复温期CBF、CMRO2和EEG恢复好于A组、B组。复温末A组、B组颈内静脉乳酸含量显著高于C组、D组，脑水含量组间差异无显著性。结论：深低温体外循环流量灌注对脑保护的作用能力强于降温期pH稳态血气管理，两种方法配合应用具有脑保护的协同作用。     

Relationship of brain blood flow and oxygen consumption to perfusion flow rate during profoundly hypothermic cardiopulmonary bypass. An experimental study

A study was made of the relation of brain blood flow and oxygen consumption to changes in perfusion flow rate during cardiopulmonary bypass at 20 degrees C in nine cynomolgus monkeys. Four perfusion flow rates varying from 0.25 to 1.75 L X min-1 X m-2 were randomly instituted, each for a 10 minute period. At the end of each period, brain arteriovenous oxygen content difference was measured and 15 mu radioactive microspheres were injected into the arterial perfusion line. The brain was then removed and section into anatomic regions and radioactivity was counted. Regional and total brain blood flows were calculated, as was whole brain oxygen consumption. Brain perfusion continued in all areas at all perfusion flow rates. Whole brain blood flow decreased (p less than 0.0001) as perfusion flow rate was reduced (45 +/- 6.5, 41 +/- 7.9, and 23 +/- 2.8 ml X min-1 X 100 gm-1 at 1.5, 1.0, and 0.5 L X min-1 X m-2, respectively). The proportion of the total perfusion delivered to the brain increased (p = 0.003) with decreasing perfusion flow rates (5.4% +/- 0.78%, 7.1% +/- 1.24%, and 8.2% +/- 1.11% at 1.5, 1.0, and 0.5 L X min-1 X m-2, respectively). Brain blood flow resistance remained unchanged (p = 0.4) while that of the remaining body increased (p less than 0.0001). There was a greater reduction of blood flow in the cortical white matter (p = 0.01) than in other regions of the brain. Brain oxygen consumption was the same (p = 0.5) at all perfusion flow rates, related to an increasing percent oxygen extraction with decreasing perfusion flow rate (p less than 0.0001). The data indicate that all areas of the brain remain perfused, even at low perfusion flow rates, during profoundly hypothermic cardiopulmonary bypass, and that brain oxygen consumption is maintained in part by increased oxygen extraction and in part by redistribution of the perfusate from the remaining body to the brain.     

Reduced complement activation during cardiopulmonary bypass does not affect the postoperative acute phase response.

OBJECTIVE: In the present study the relationship was evaluated between perioperative inflammation and the postoperative acute phase response in patients undergoing elective coronary artery bypass grafting (CABG) assisted by cardiopulmonary bypass (CPB). CPB circuits contained either non-coated- (UMS), Carmeda- (BPS) or Trillium-coated oxygenators (BAS). METHODS: Prospectively, 71 CABG patients were randomly allocated to one of the oxygenator groups (UMS: n=25, BPS: n=25 and BAS: n=21). Terminal complement complexes (TCC) and elastase were determined in plasma samples collected before, during and after bypass. Secretory phospholipase A2 (sPLA2) and C-reactive protein (CRP) were determined before and after bypass. RESULTS: Demographic, CPB and clinical outcome data were similar for the three groups. TCC and elastase increased during CPB, and decreased thereafter. Significant differences between the groups were present in the levels of TCC at the end of CPB (P=0.002) and at the first (P=0.012) and second (P<0.001) postoperative days, the BPS and BAS groups having reduced levels of TCC compared to the UMS group. Also elastase concentrations differed significantly between the groups at the end of CPB (P<0.001). The postoperative sPLA2 and CRP levels increased in all three groups on the first and second postoperative days, but no significant differences were present between the groups. CONCLUSIONS: Material-induced reduction of the inflammatory response during CPB does not affect the postoperative acute phase response. Thus, in CABG patients this response seems relatively unaffected by the composition and/or biocompatibility of the modern CPB circuit and rather to be evoked by surgical trauma, anesthetics and organ perfusion.