Effective hepatic blood flow during cardiopulmonary bypass

Hepatic dysfunction following cardiopulmonary bypass (CPB) is a relatively frequent finding, and jaundice occurring after CPB is associated with an increased mortality rate. Post-CPB jaundice may be a consequence of inadequate liver perfusion during CPB. To evaluate the potential impact of CPB on effective hepatic blood flow, 10 patients undergoing CPB for cardiac procedures were studied. Effective hepatic blood flow was measured in each patient during the operative procedure but before institution of CPB and during CPB as well. Effective hepatic blood flow was measured by the galactose clearance technique. Blood lactate and pyruvate levels were also measured before and during CPB. During CPB, effective hepatic blood flow was consistently reduced by an average of 19%. Although for most patients this reduction seems well tolerated, in a minority of patients it may contribute to postoperative hepatic dysfunction.     

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 and autoregulation during hypothermic cardiopulmonary bypass

Mean hemispheric cerebral blood flow (CBF) was studied following intravenous or intraarterial administration of xenon-133, in 10 men admitted for coronary artery bypass grafting. Repeated CBF measurements were performed to evaluate autoregulation before, during, and after cardiopulmonary bypass (CPB). During CPB mean CBF remained unchanged compared with the pre-CPB level, without evidence of cerebral hyperemia or impairment of autoregulation. A marked increase in CBF occurred after CPB and was followed by a time-dependent reduction toward the pre-CPB level. The data support the alpha-stat regulation theory but cannot explain the cerebral vasodilation observed after CPB.     

Splanchnic blood flow and oxygen uptake during cardiopulmonary bypass

OBJECTIVE: To measure splanchnic blood flow (SBF) with 2 indicator dilution techniques during and after cardiopulmonary bypass (CPB), to compare the results with transesophageal echocardiography Doppler-measured right hepatic vein (RHV) flow, and to study gastric tonometry data in the same patients. DESIGN: Single-arm prospective study. SETTING: University hospital operating room and intensive care unit. PARTICIPANTS: Ten adult patients undergoing cardiac surgery. INTERVENTIONS: SBF was measured using constant rate infusion of indocyanine green dye and low-dose ethanol from induction of anesthesia until end of hypothermic CPB. The infusion of ethanol was continued, and SBF was measured postoperatively at 2, 3, and 4 hours after CPB. Simultaneously, RHV flow, splanchnic oxygen delivery and uptake, and gastric mucosal pH were calculated. MEASUREMENTS AND MAIN RESULTS: SBF, RHV flow, and gastric mucosal pH remained unchanged during the study period. SBF measured with indocyanine green was 765 +/- 88 (SEM) mL/min after induction of anesthesia. SBF before CPB measured with ethanol was 985 +/- 218 mL/min. There was no significant difference between the methods. RHV flow was 450 +/- 87 mL/min after induction of anesthesia. There was no correlation between individual values of RHV flow and SBF. Splanchnic oxygen uptake was 52 +/- 7.8 mL/min after induction of anesthesia and decreased to 28 +/- 2.6 mL/min during CPB. Gastric mucosal pH was 7.32 +/- 0.02 after induction of anesthesia and showed no correlation to SBF or to splanchnic oxygen uptake. CONCLUSION: SBF did not decrease during CPB. SBF could be measured with ethanol with reasonable accuracy. Transesophageal echocardiography assessment of RHV flow was not suitable to quantify SBF in the individual patient, but could be used to follow relative changes.     

多巴胺对病人体外循环期间肾血流的影响

目的 评价小剂量多巴胺对病人体外循环(CPB)期间肾血流的影响.方法 择期体外循环下行心血管手术病人60例,年龄21～64岁,随机分为2组(n=30):生理盐水对照组(C组)和多巴胺组(D组).麻醉诱导后气管插管,机械通气,分别于首次灌注心脏停搏液后5 min(给药前)及颈内静脉输注多巴胺2/μg·kg-1·min-120min时(给药后)采用经食管超声测定左侧肾动脉内径及血流速度,计算左肾血流量和肾动脉阻力.结果 与C组比较,D组给药后肾动脉血流速度及血流量增加,肾动脉阻力下降(P<0.05),肾动脉内径差异无统计学意义(P0.05).结论 CPB中静脉输注小剂量多巴胺可增加肾大血流量.     

Changes in body temperature during profound hypothermic cardiopulmonary bypass in adult patients undergoing aortic arch reconstruction

Purpose Our aim was to characterize changes in body temperatures during profound hypothermic cardiopulmonary bypass (CPB) conducted with the sternum opened.Methods In ten adult patients who underwent profound hypothermic (20°C) CPB for aortic arch reconstruction, pulmonary arterial temperature (PAT), nasopharyngeal temperature (NPT), forehead deep-tissue temperature (FHT), and urinary bladder temperature (UBT) were recorded every 1min throughout the surgery. In addition, the CPB venous line temperature (CPBT), a reasonable indicator of mixed venous blood temperature during CPB and believed to best reflect core temperature during stabilized hypothermia on CPB, was recorded during the period of total CPB.Results PAT began to change immediately after the start of cooling or rewarming, closely matching the CPBT (r = 0.98). During either situation, the other four temperatures lagged behind PAT (P 0.05); however, NPT followed PAT more closely than the other three temperatures (P 0.05). During stabilized hypothermia, PAT, NPT, and FHT, but not UBT, closely matched the CPBT, with gradients of less than 0.5°C.Conclusion During induction of profound hypothermia and its reversal on total CPB with the heart in situ, a PA catheter thermistor, presumably because of its placement immediately behind the superior vena cava, would provide a reliable measure of the mixed venous blood temperature. During stabilized profound hypothermia, PAT, NPT, and FHT, but not UBT, serve as a reliable index of core temperature.This work was presented, in part, at the 50th annual meeting of the Japanese Society of Anesthesiologists, Yokohama, May 29–31, 2003, and at the annual meeting of the American Society of Anesthesiologists, San Francisco, USA, October 11–15, 2003.     

Distribution and hierarchy of regional blood flow during hypothermic cardiopulmonary bypass

BACKGROUND: Cardiopulmonary bypass (CPB) may decrease oxygen delivery relative to the nonbypass state. We predicted that a hierarchy of regional blood flow could be characterized under hypothermic (27 degrees C) CPB. METHODS: Ten pigs underwent bypass at 27 degrees C. Fluorescent microspheres were administered before and during CPB at four randomized flows: 1.9, 1.6, 1.3, and 1.0 L x min(-1) x m(-2). At completion, tissue samples were obtained from brain, renal cortex and medulla, pancreas, small bowel, and limb muscle for regional blood flow determination. RESULTS: Cerebral blood flow remained unchanged between CPB flows of 1.9 and 1.3 L x min(-1) x m(-2). Renal perfusion was stable between flows of 1.9 and 1.6 L x min(-1) x m(-2), whereas perfusion of small bowel decreased linearly with pump flow. Pancreatic perfusion was unchanged over the range of flows studied; muscle blood flow was profoundly reduced at the highest CPB flow and further decreased if pump flow was reduced below 1.6 L x min(-1) x m(-2). CONCLUSIONS: This study characterizes the organ-specific hierarchy of blood flow and oxygen distribution during hypothermic CPB. These dynamics are relevant to clinical decisions for perfusion management.     

Use of hypothermia and cardiopulmonary bypass in resection of aortic arch aneurysms

Surgical correction of aortic arch aneurysms can be technically difficult and present hazards related to central nervous system and myocardial viability. Temporary circulatory arrest may be necessary, and in the age group in which most aneurysms are found, coronary and peripheral vascular disease increase the risk of ischemic damage.A patient is presented in whom hypothermia and cardiopulmonary bypass were utilized for resection of an aneurysm of the distal two-thirds of the aortic arch. Flow to the head through the right brachial and left common carotid arteries was regulated by monitoring pressure tracings from bilateral temporal artery catheters. Anoxic cardiac arrest for 70 minutes was well tolerated. No neurological deficit or cardiac dysfunction was evident postoperatively.Hypothermia with cardiopulmonary bypass is the approach of choice with aneurysms of the aortic arch. It affords the best protection for the central nervous system and myocardium.     

Numerical simulation of the flow field within the aortic arch during cardiac assist

In recent years, artificial heart devices have been implanted in a considerable number of patients with terminal cardiac failure for bridge to transplantation and even destination therapy. These devices provide either pulsatile or continuous blood flow. To determine eventual physiological effects of these different types of flow on the aorta,a computational fluid dynamics model of the aorta and its thoracic branches was implemented. Pulsatile and continuous flow fields were calculated by implementing a comprehensive computational framework with a stabilized finite element method. The computed results revealed that the pulsatile pump support results in a lower mean shear stress and higher oscillatory shear stress index than the continuous pump support. The flow patterns for the pulsatile pump support above the closed aortic valves show a similar washout as for the continuous pump support. In summary, from the flow pattern simulation there was no particular preference for either pulsatile or continuous devices     

Neuronal and astroglial injuries in patients undergoing coronary artery bypass grafting and aortic arch replacement during hypothermic cardiopulmonary bypass

More than 50% of patients suffer neuropsychologic impairment after cardiac surgery. We measured neuron-specific enolase (NSE) and S-100 protein (S-100) in patients' serum as putative markers of neuronal and astroglial cell injury, respectively. Group I (n = 13) underwent coronary artery bypass grafting (CABG) with mild hypothermic cardiopulmonary bypass (CPB); Group II (n = 6) underwent aortic arch replacement with deep hypothermic CPB; Group III (n = 8) underwent CABG under normothermia without CPB. During and after the operation, serum levels of NSE and S-100 were significantly increased only in Groups I and II (during CPB), NSE still being increased 12 h after surgery in Group II. This suggests that neuronal and astroglial cell injuries are more likely in patients undergoing CABG with mild hypothermic CPB or aortic arch replacement with deep hypothermic CPB than in those undergoing CABG under normothermia without CPB. However, these increases of NSE and S-100 failed to reflect clinical brain damage. Rather, an electroencephalogram, was only capable of detecting neurologic complications after surgery. Implications: Neuronal and astroglial cell injuries are likely to occur during coronary artery bypass grafting with mild hypothermic cardiopulmonary bypass (CPB) or aortic arch replacement with deep hypothermic CPB. Conversely, patients undergoing coronary artery bypass grafting without CPB under normothermic conditions may be less likely to suffer brain cell injury.     

Pulsatile flow during routine cardiopulmonary bypass

The effect of pulsatile flow during cardiopulmonary bypass (CPB) was studied on two groups of 11 patients each (aged between 18 and 48 years) undergoing open valvular and congenital heart surgery. In the nonpulsatile group, mean blood pressure (BP) and systemic vascular resistance index (SVRI) increased steadily during CPB; while in the pulsatile group, both BP and SVRI remained stationary. The difference of SVRI between the two groups was not significant within 30 minutes after initiation of CPB (3136 +/- 882 to 2536 +/- 530 dynes X sec X cm-5 X m2). Contrarily, it was significantly higher in the nonpulsatile group after 40 minutes of CPB (3748 +/- 562 to 2612 +/- 609 dynes X sec X cm-5 X m2, p less than 0.02) and thereafter. Oxygen consumption index (59.6 +/- 12.9 to 77.8 +/- 32.6 ml X min-1 X m-2) and carbon dioxide production index (41.1 +/- 16.0 to 59.3 +/- 28.1 ml X min-1 X m-2) measured 20 minutes after institution of CPB seemed lower in the nonpulsatile group than in the pulsatile group, but the differences were not statistically significant. Increased urine flow during CPB (1.8 +/- 1.1 to 6.3 +/- 3.8 ml X min-1 X m-2, p less than 0.001) with less variability indicated better reserve of renal function in the pulsatile group; and less percent change of postoperative sGOT from preoperative level (529.8 +/- 129.8 to 310.0 +/- 175.2%, p less than 0.005) also showed better hepatic function in the pulsatile group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cerebral blood flow autoregulation is preserved during cardiopulmonary bypass in isoflurane-anesthetized patients

In 21 patients undergoing elective coronary artery bypass surgery, cerebral blood flow (CBF) was measured during hypothermic nonpulsatile cardiopulmonary bypass to test the hypothesis that isoflurane abolished the mean arterial pressure-CBF relation (pressure-flow autoregulation). Cerebral blood flow was determined by 133Xe clearance. The patients were randomly divided into three groups according to anesthesia during cardiopulmonary bypass: group 1 received midazolam and fentanyl; group 2 received, in addition to midazolam and fentanyl, 0.6% isoflurane; and group 3 received, in addition to midazolam and fentanyl, 1.2% isoflurane. The groups were maintained at a constant temperature, PaO2, PaCO2, and pump flow during CBF measurements. Mean arterial pressure was increased by phenylephrine greater than or equal to 25% after the first CBF determination. Isoflurane decreased mean arterial pressure significantly (P less than 0.05) and was associated with lower CBF. Increasing the mean arterial pressure 29% in group 1, 25% in group 2, and 34% in group 3 had no effect on CBF. We conclude that, within the range studied, pressure-flow CBF autoregulation is preserved during isoflurane anesthesia administered for cardiopulmonary bypass.     

Urethral blood circulation during cardiopulmonary bypass

The haemodynamic changes induced by extracorporeal circulation (ECC) are thought to be important in the induction of urethral strictures in open heart surgery when indwelling latex catheters are used. In the present study, 6 piglets were cannulated and connected to extracorporeal perfusion apparatus. Pump flows correlated with human ECC values with non-haemic prime were used. The mucosal and submucosal blood circulation in the urethra reduced by 66% during ECC (P less than 0.05). The brain and hepatic arterial flows increased. A significant reduction was seen in renal blood circulation. The changes in the urethral blood circulation during ECC correlated with previous findings. The reduced wash out levels of chemicals leaching from the indwelling latex catheters as a result of reduced local blood circulation are the main trigger for the induction of urethral strictures during ECC and in other shock-like circulatory disturbances in the human body.     

Pulsatile flow improves cerebral blood flow in pediatric cardiopulmonary bypass

The objective of this study was to evaluate the effect of pulsatile flow on cerebral blood flow (CBF) in infants with the use of a mild hypothermic cardiopulmonary bypass (CPB). Thirty infants scheduled for open heart surgery were randomized to the pulsatile group (Group P, n = 15) and nonpulsatile group (Group NP, n = 15). In Group P, pulsatile perfusion was applied during the aortic cross‐clamping period, whereas nonpulsatile perfusion was used in Group NP. The systolic peak velocity (Vs), the end of diastolic velocity (Vd), the mean velocity (Vm), and the pulsatility index (PI) and the resistance index (RI) of the middle cerebral artery were measured by a transcranial Doppler (TCD) ultrasound after anesthesia (T1; baseline), at the beginning of CPB (T2), 10 min after aortic cross‐clamping (T3), 3 min after declamping (T4), at the cessation of CPB (T5), and at the end of the operation (T6). During T3 and T4, the Vs in Group P was significantly higher than in Group NP. However, there were no statistically significant differences between Vd and Vm. The PI and RI in Group P were also higher than those in Group NP (both P < 0.05). During T5, Vd and Vm were higher in Group P (P < 0.05), whereas there was no difference in Vs. Additionally, PI and RI in Group P were significantly lower than those in Group NP (P < 0.05). However, there was no difference during T6. Pulsatile perfusion may increase CBF and decrease cerebral vascular resistance in the early period after mild hypothermic CPB.