Effects of propofol on mean arterial pressure and systemic vascular resistance during cardiopulmonary bypass

This study was designed to evaluate the effects of propofol on mean arterial pressure (MAP) and systemic vascular resistance (SVR) during cardiopulmonary bypass (CPB). Twenty patients were divided randomly for administration of 2 mg·kg^-1 propofol (group Propofol, n = 10) or 0.9% saline solution (group Control, n=10) during CPB. The two groups were comparable with respect to sex, age, height, type of surgery (valvular or coronary), arterial hypertension and preoperative antihypertensive treatment. Only their weight and body surface area were significantly different (control group vs propofol group, respectively: 78.5 + 14.4 vs 64.7±7.7 kg, P < 0.05; and 1.85 ±0.2 vs 1.68 ±0.13 m², P < 0.05). MAP, SVR and SVR index were significantly lower in the propofol group than in the control group at 10, 15 and 20 min of study, suggesting that the hypotensive effect of a bolus injection of propofol is due, at least in part, to a direct decrease in the SVR.     

Effects of chlorpromazine as a systemic vasodilator during cardiopulmonary bypass in neonates

OBJECTIVES: Vasodilator use during cardiopulmonary bypass is important in pediatric cardiac surgery, but the full range of their effects on hemodynamics remains to be clarified. We studied the effects of chlorpromazine, a potent alpha-blocking agent, in neonates. METHODS: Subjects were 60 neonates undergoing arterial switch operations for complete transposition of the great arteries with an intact ventricular septum. Of these, 37 received 2.1 to 6.5 mg/kg of chlorpromazine during cardiopulmonary bypass (CPZ group) and 23 received no vasodilator (control group). We then compared hemodynamic parameters between groups during and early after surgery. RESULTS: The systemic vascular resistance index and mean arterial pressure during cardiopulmonary bypass were significantly lower in the CPZ group (p < 0.05), but systolic pressure 15 minutes after cessation of cardiopulmonary bypass did not differ between groups. The rise in peripheral temperature during rewarming after hypothermia was significantly higher and the acid-base status 40 minutes after cardiopulmonary bypass less acidotic in the CPZ group. Urine output during cardiopulmonary bypass was higher in the CPZ group. CONCLUSIONS: Chlorpromazine effectively counteracts systemic vasoconstriction induced by cardiopulmonary bypass without serious side effects in neonatal cardiac surgery.     

Binding of fentanyl and alfentanil to the extracorporeal circuit

Adsorption of fentanyl and alfentanil to the cardiopulmonary bypass (CPB) equipment was studied in vitro by adding one of the analgesics to the priming solution consisting of either saline or a mixture of saline and blood. Opiate concentrations in the solutions were measured during a 60-min circulation period of a closed CPB system. When the saline prime was used, 29% of the predicted fentanyl level of 30 ng ml-1 was found at the end of the experiment, while the recovery of alfentanil was 80% of the calculated level of 1500 ng ml-1. When blood was added to the prime, experiments with fentanyl produced similar results to those with pure saline prime, but recovery exceeding the calculated concentration was obtained with alfentanil. The difference between the alfentanil levels in the two primes may reflect the poor distribution of this analgesic into red blood cells. In another set of experiments, the CPB circuit was primed with fentanyl or alfentanil and circulated for 10 min before connection of the apparatus to patients undergoing cardiac surgery under high-dose opiate anaesthesia. This priming prevented the steep reduction in plasma opiate concentration regularly observed during the institution of CPB. It is concluded that in a clinically relevant dose range a smaller fraction of alfentanil is sequestered by the CPB apparatus than fentanyl.     

Vascular resistance during cardiopulmonary bypass Its effect on cardiac performance in the immediate post-bypass period

A clinical study was undertaken to measure changes in systemic vascular resistance during cardiopulmonary bypass in 56 adults. Forty-five patients snowed a rise in systemic vascular resistance and 77% required no inotropic support in the immediate post-bypass period. Eleven of the 33 patients undergoing valve replacement surgery showed only a small increase or an actual decrease in systemic vascular resistance and required inotropic support. These results were statistically significant. Factors affecting cardiac performance are discussed.     

瑞芬太尼对体外循环患者体循环阻力的影响

Objective To investigate the mechanism by which remifentanil decreases blood pressure during cardiopulmonary bypass (CPB).Methode Twenty-six ASA Ⅱ or Ⅲ patients (NYHA's classification grade Ⅱ or Ⅲ ) of both sexes and aged 20-55 years were randomized to receive remifentanil (group R, n = 13) or normal saline (group C, n = 13). Remifentanil 10 μg/kg or equal volume of normal saline was administered via a venous reservoir when cardiac arrest was induced with cardioplegic solution. The flow rate resistance (SVR) were measured and arterial blood samples were taken for determination of plasma concentrations of histamine,nitric oxide (NO) and 6-keta-prostaglandin F1α(PGF1α) before T0 and at 5, 10, 15 min (T5.10.15) after remifentanil administration.Results Remifentanil administration was associated with a significant decrease in MAP and SVR at T5 and T10 as compared with the baseline values at T0 ( P ＜ 0.05); whereas in control group, MAP and SVR were significantly increased at T5, T10 and T15 as compared with the baseline values at T0 . There were no significant differences in plasma histamine, NO and PGF1α concentrations between the two groups.Conclusion Remifentanil reduces SVR and causes a decrease in BP but without altering plasma concentrations of histamine, NO or PGl2.     

Action of propofol on resistance and capacitance vessels during cardiopulmonary bypass

The peripheral vascular action of propofol on the resistance and the capacitance vessels was investigated in 16 patients during cardiopulmonary bypass. The venous reservoir (RV) and mean arterial pressure (MAP) were used as indices of the changes in venous capacitance and systemic vascular resistance (SVR), respectively. Propofol 2 mg.kg-1 produced a decrease in MAP without a significant change in RV, suggesting that propofol preferentially decreases SVR without a significant change in venous capacitance.     

A rat model of cardiopulmonary bypass with excellent survival

BACKGROUND: Elucidating the underlying mechanisms and developing protective strategies for the pathophysiological consequences of cardiopulmonary bypass (CPB) have been hampered due to the absence of a satisfactory long-term recovery animal model. The objective of this study was to establish a survival experimental model of CPB in rats to meet the requirement of these studies. MATERIALS AND METHODS: Male SD rats (450-550 g) were randomly divided into CPB (n = 10) group and Sham group (n = 10). All rats were anaesthetized and mechanically ventilated. The femoral artery and vein were cannulated for continuous blood pressure recordings and fluid replacement, respectively. The CPB circuit comprised a venous reservoir, a membrane oxygenator, and a roller pump. Blood was drained from the right atrium via a jugular vein catheter and returned to the right carotid artery. Priming consisted of 8 ml of homologous blood and 8 ml of colloid. CPB was conducted for 60 min at a flow rate of 100-150 ml/kg/min in the CPB group. Haemodynamic investigations, blood gas analysis, and survival studies were performed subsequently. RESULTS: Our data show that the rat model principally simulated the clinical setting of CPB in terms of its construction, configuration, performance, material surface area, and priming volume to blood volume ratio. All CPB rats survived and the 2-week follow-up period remained uneventful. CONCLUSIONS: The rat model of CPB was easy to establish and was associated with excellent survival. This model should facilitate the investigation of the pathophysiological processes concerning CPB-related multiple organ dysfunction and possible protective interventions.     

Thiopentone pharmacokinetics during cardiopulmonary bypass with a nonpulsatile or pulsatile flow

To evaluate possible factors affecting the pharmacokinetics of thiopentone during cardiopulmonary bypass (CPB), the present study was undertaken in patients scheduled for coronary artery bypass grafting and with in vitro experiments. The effects of nonpulsatile and pulsatile flow during CPB on the distribution and elimination of thiopentone were compared in 30 patients anaesthetized with fentanyl. The initial rapid phases of distribution of thiopentone were studied in 17 patients undergoing a nonpulsatile or pulsatile perfusion, to whom thiopentone 6 mg/kg was given as a rapid intravenous bolus during CPB. In order to study later distribution and early elimination of thiopentone, 13 patients perfused with a nonpulsatile or pulsatile flow received 6 mg/kg of the drug as a 15-min intravenous infusion before CPB. No differences in the pharmacokinetic parameters characterizing distribution and elimination of thiopentone were found between the patients undergoing nonpulsatile or pulsatile perfusion. As measured in 10 of the patients receiving the drug before the institution of CPB, no difference in plasma thiopentone level was observed in blood samples drawn simultaneously from a radial arterial cannula and a pulmonary artery catheter before, during and after CPB. This suggests that thiopentone is not sequestered in lungs during CPB. In vitro binding of thiopentone to the CPB equipment was studied in 6 experiments using a closed circuit. After a 60-min circulation time, only 50% of the predicted thiopentone level was recovered from the perfusate. It is concluded that replacing a nonpulsatile perfusion with a pulsatile one has no effect on the distribution and elimination of thiopentone in patients undergoing CPB. During CPB, thiopentone is sequestered in the extracorporeal circuit but not in the lungs.     

Influence of arterial carbon dioxide tension on systemic vascular resistance in patients undergoing cardiopulmonary bypass

Background : The effects of induced hypothermia in cardiac surgical patients are not yet fully understood. Despite numerous studies on the effects of acid-base management on organ blood flow, only little information is available on the effects of α-stat versus pH-stat management on systemic haemodynamics. We therefore compared the effect of a-stat and pH-stat acid-base management on systemic haemodynamics in a prospective, controlled, cross-over study.
Methods : Twenty patients undergoing coronary artery bypass surgery were included in the study. Cardiac output was measured by thermodilution. Cardiac index and systemic vascular resistance were calculated according to standard formulae. Measurements were performed under hypo- and hypercapnia after induction of anaesthesia. Measurements were repeated at the end of two 30-min periods of pH-stat and α-stat acid-base management, respectively.
Results : Systemic vascular resistance at the lower PaCO₂-levels (hypocapnia and α-stat, respectively) was significantly higher than those at the higher level (hypercania and pH-stat, respectively). The periods of different PaCO₂-levels were comparable with respect to haematocrit, blood viscosity and temperature. Systemic vascular resistance was not significantly different from the control period.
Conclusions : This study demonstrates that during hypothermic cardiopulmonary bypass, systemic vascular resistance underα-stat acid-base management is higher than under pH-stat management. As obvious from measurements during the control period, this finding can be completely explained by the difference in PaCO₂.     

Critical values of hematocrit and mixed venous oxygen saturation as parameters for a safe cardiopulmonary bypass

Objective: Mixed venous oxygen saturation (SvO₂) is high despite a low hematocrit implies that the relationship between oxygen demand and supply is in a safe state. This study was sought to determine the critical values for hematocrit and SvO₂ for safe cardiopulmonary bypass. Methods: Study 1: To evaluate the limit of hemodilution without cardiopulmonary bypass, normovolemic hemodilution with Dextran 40 (10%) was performed in 14 rabbits. SvO₂ was monitored from the right atrium, and the hemodynamic parameters were recorded continuously. Study 2: To determine the critical values for hematocrit and SvO₂ during cardiopulmonary bypass, normothermic and hypothermic cardiopulmonary bypass were performed in 13 rabbits and hemodynamic parameters were corrected. Results: Study 1: The heart rate decreased to unsafe levels abruptly, when the SvO₂ was ≦43% or the hematocrit was ≦10%. The lactate concentration increased when the SvO₂ was ≦46% or the hematocrit was ≦12%. Study 2: When the hematocrit was ≦12%, the SvO₂ decreased gradually. Even when weaning was possible, the animals with a hematocrit ≦12% collapsed hemodynamically within 40 minutes after cardiopulmonary bypass. Most of the animals could not be weaned from cardiopulmonary bypass during either normothermic or hypothermic cardiopulmonary bypass when the SvO₂ was ≦46%. Conclusions: Continuous monitoring of hematocrit and SvO₂ provides evidence-based guidelines for safe cardiopulmonary bypass. The lower limits of critical range for a safer cardiopulmonary bypass are hematocrit of 12% and SvO₂ of 46%.     

Effects of calcium on left ventricular function early after cardiopulmonary bypass

Evaluation of the effects of intravenous CaC1₂on systolic and diastolic function early after separation from cardiopulmonary bypass (CPB) Prospective study University hospital Twenty patients scheduled for elective coronary artery surgery Left ventricular (LV) pressures were measured with fluid-filled catheters. Data were digitally recorded during pressure elevation induced by tilt-up of the legs. Transgastric short-axis echocardiographic views of the LV were simultaneously recorded on videotape. Measurements were obtained before the start of CPB, 10 minutes after termination of CPB, after intravenous administration of CaC1₂, 5 mg/kg, and 10 minutes later.

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Systolic function was evaluated with the slope (Ees, mmHg/mL) of the systolic pressure-volume relation. Diastolic function was evaluated with the chamber stiffness constant (Kc, mmHg/mL) of the diastolic pressure-volume relation. CaC1₂increased Ees from 2.62 ± 0.46 to 5.58 ± 0.61 (mean ± SD), but induced diastolic dysfunction with an increase in Kc from 0.011 ± 0.006 to 0.019 ± 0.007. These changes were transient and had disappeared within 10 minutes after administration of CaC1₂. CaC1₂early after CPB transiently improved systolic function at the expense of an increase in ventricular stiffness, suggesting temporary diastolic dysfunction.     

Central–to–peripheral arterial pressure gradient during cardiopulmonary bypass: relation to preand intra–operative data and effects of vasoactive agents

A significant central–to–peripheral arterial pressure gradient may exist during and after cardiopulmonary bypass (CPB). The etiology and mechanisms of this phenomenon remain controversial. We studied the pressure gradient between aorta, brachial artery and radial artery in 68 patients, scheduled for elective coronary artery bypass surgery. We evaluated whether choice of cardioprotection during CPB (use of cold cardioplegic solution or use of intermittent crossclamping under protection with lidoflazine), and choice of pulsatile or nonpulsatile flow during the course of CPB, affected the magnitude and duration of the systolic pressure gradient. We also studied whether central–to–peripheral pressure gradient was influenced by administration on CPB of different vasoactive drugs with different mode of action: sodium nitroprusside (direct action on the vessels), droperidol (alpha–adrenergic blocking action), ketanserin (5–hydroxytryptamine antagonist) and phenylephrine (selective alpha,–agonist).
It appeared that central–to–peripheral gradient occurred early during CPB and remained constant throughout the course of CPB. The gradient disappeared within 60 min after weaning from CPB. We found the main pressure gradient to occur between the brachial and the radial artery. There was no relation between magnitude of the gradient and sex, weight, length or age of the patient. There was also no relation between magnitude of the pressure gradient and type of cardioprotection, choice of pulsatile vs nonpulsatile flow on CPB and duration of CPB. We also found no relation between pressure gradients and changes in temperature, haematocrit and systemic vascular resistance. The pressure gradient was not affected by any of the vasoactive drugs.     

Hemodynamic effects of prostaglandin E1 during cardiopulmonary bypass in infants and children

Effects of prostaglandin E₁ (PGE₁) and phenoxybenzamine (POB) on the hemodynamics during cardiopulmonary bypass (CPB) were studied in 30 infants and children. Patients were grouped into three; PGE₁ was given to ten patients, POB to another ten, and the other ten patients served as the control. Vasodilative drugs were witheld. PGE₁ was infused at 0.01 to 0.02 μg/kg/min during CPB, and POB at 1.0 mg/kg within the initial 10 minutes of bypass. There was a significant drop in arterial and venous pressure at the time of initiation of bypass in both the PGE₁ and POB groups. In the PGE₁ group in particular, such a stable hemodynamic condition of over 60 mm Hg in mean arterial pressure, 7.5 to 12.5 cmH₂O in central venous pressure, 1300 to 1700 dynes·sec·cm⁻⁵ in systemic vascular resistance was maintained throughout CPB, as compared with the other two groups. PGE₁ contributed to an adequate diuresis and the preservation of platelets. Our findings indicate that PGE₁ has potential clinical advantages for application during CPB.     

Rat cardiopulmonary bypass model: application of a miniature extracorporeal circuit composed of asanguinous prime

A clinically relevant rat cardiopulmonary bypass (CPB) model would be a valuable tool for investigating pathophysiological and therapeutic strategies on bypass. Previous rat CPB models have been described in the literature; however, they have many limitations, including large circuit surface area, the inability to achieve full bypass, and donor blood requirements for prime. Therefore, we have established a rat CPB model designed to overcome these limitations. The miniature circuit consisted of a filtered reservoir, heat exchanger, membrane oxygenator (surface area = 0.02 m2) with a static priming volume of 2.8 mL, and an inline blood gas monitor. The circuit was primed with 9.5+/-0.5 mL of crystalloid solution and CPB was established on male Sprague-Dawley rats (430-475 g, n = 5) by cannulating the left common carotid artery and the right external jugular vein. The animals were placed on CPB at full flow (111+/-13 mL/kg/ min) for 1 hour and were monitored for and additional 2 hours after the CPB procedure. Hemodynamics, hemoglobin concentration (Hb), and blood gases were analyzed at three time intervals: before, during, and after CPB. The circuit performance was evaluated according to prime volume, compliance, hemodynamic parameters, and gas and heat exchange as described by modified AMMI standards. Data are expressed as mean+/-SD and a repeated-measures analysis of variance with post-Hoc test was used for data comparison between the three time intervals. The ratio of oxygenator surface area to subject body weight for this model is comparable with that of current human adult CPB practice (0.05 m2/kg vs 0.057 m2/kg) Full CPB was achieved and we observed clinically acceptable PaO2, PaCO2, and SvO2 values (209+/-86 mmHg, 25+/-2 mmHg, 78+/-8%, respectively) while on CPB. The use of asanguinous prime did produce statistically significant Hg reduction (15.7+/-0.76 vs. 9.2+/-0.59 g/dL) comparable with clinical practice. No statistically significant differences between pre- and post-CPB hemodynamics and blood gases were found in our study. We have established a miniature circuit consisting of asanquineous prime for a rat CPB model that maintains clinically acceptable results regarding hemodynamic parameters, blood gases, and hemodilution. This model would be valuable for further use in clinically relevant research studies.     

异氟烷预处理对犬心肺转流术相关肺损伤的影响

目的研究异氟烷预处理对心肺转流术（CPB）相关肺损伤的影响。方法12只犬（10kg～18kg），戊巴比妥钠（25mg／kg，iv）麻醉后行股动静脉穿刺、颈外静脉放置飘浮导管、气管插管行机械通气，建立监测（心电图、血流动力学、鼻咽温和气体）后开胸肝素化行主动脉、左右心房插管，操作完成后将动物稳定15min，记录基础值。随后动物被随机分为两组（n=6）。对照组（C组）为空白组；异氟烷预处理组（ISO组）在CPB前吸入1．39％（1．0MAC）异氟烷30min。所有动物行CPB 100 min，其中主动脉和肺动脉阻断60min，维持鼻咽温28℃～30℃。CPB后150min取左下肺对应肺组织标本用于丙二醛（MDA）、多形核粒细胞（PMNs）计数和湿／干重比（WDR）的测定。结果两组间血流动力学参数、MDA及WDR差异无统计学意义。C组的PMNs计数在CPB后150min比ISO组高，差异有统计学意义（P=0．036）。结论异氟烷预处理可减轻CPB结束后早期PMNs的肺内聚集。     

Vacuum assisted cardiopulmonary bypass in minimally invasive cardiac surgery: its feasibility and effects on hemolysis

The present study describes a cardiopulmonary bypass (CPB) technique that incorporates vacuum assisted venous drainage and arterial return using a centrifugal pump in minimally invasive cardiac surgery (MICS). The technique was performed on 40 patients scheduled to undergo MICS. The proposed CPB technique enables a good operative field to be obtained even through a limited incision through the use of peripheral cannulation using small cannulae. Vacuum pressure was applied to the venous reservoir (-43 +/- 14 mm Hg) to maintain adequate CPB flow (>2.4 L x min-1 x M-2). The effects of CPB on hemolysis were subsequently compared between patients who underwent the proposed procedure (MICS group; n = 6) and a control group who underwent coronary arterial bypass grafting (CABG group; n = 6) with conventional CPB. Plasma free hemoglobin (FHb) increased and plasma haptoglobin (Hp) decreased during CPB in both groups, with no significant difference between the groups. By the next day, FHb had returned to pre-CPB levels whereas Hp remained lower in both groups. Again, these values did not differ significantly between groups. Thus, we conclude that the proposed CPB technique is useful in MICS with acceptable effects on hemolysis.     

No effect of L-arginine supplementation on pulmonary endothelial dysfunction after cardiopulmonary bypass

BACKGROUND: Acetylcholine is an endothelium-dependent vasodilator through the L-arginine-nitric oxide pathway. After ischemia-reperfusion this effect is attenuated, also demonstrated in the pulmonary circulation after cardiopulmonary bypass. Administration of L-arginine has been shown to have a protective effect on endothelial function in reperfusion injury. The aim of the current study was to test the possible effect of L-arginine on the acetylcholine reactivity in the pulmonary circulation after cardiopulmonary bypass. METHODS: Thirty-five patients with ischemic and/or valvular heart disease were investigated in a randomized, double-blinded, placebo-controlled study. The patients were divided into three groups. Group 1: high dose L-arginine (n=10), group 2: low dose L-arginine (n=10), group 3: placebo, no L-arginine, (n=15). The acetylcholine reactivity was tested with measurements of pulmonary vascular resistance before surgery and 1, 2 and 3-4 h after cardiopulmonary bypass. RESULTS: After cardiopulmonary bypass an attenuation of the acetylcholine reactivity over time was observed in all groups, with no differences between groups. CONCLUSION: In the current study L-arginine had no protective effect on the pulmonary endothelium after cardiopulmonary bypass, measured as reactivity to an infusion of acetylcholine.     

Effects of cardiopulmonary bypass and hypothermia on electroencephalographic variables

We studied the effects of hypothermia and cardiopulmonary bypass (CPB) on four depth of anaesthesia monitors; spectral edge frequency (SEF), median frequency (MF), bispectral index (BIS) and auditory evoked potential index (AEPIndex) in 12 patients during uneventful cardiac anaesthesia. Each variable was recorded simultaneously at 10 periods during anaesthesia. All four variables were not affected by the transition to CPB. During hypothermia, values of AEPIndex, MF and SEF were tightly distributed but values of BIS were very variable and overlapped with those before induction of anaesthesia. The variability decreased during rewarming. The values of AEPIndex throughout the anaesthesia never overlapped with those before induction of anaesthesia. The AEPIndex was the most stable and reliable as a depth of anaesthesia monitor among the four variables in cardiac bypass surgery.     

Effects of organic nitrate vasodilators on platelet function before and after cardiopulmonary bypass

Various in vitro , ex vivo and in vivo tests have shown that organic nitrates attenuate platelet function. Because organic nitrates are commonly administered to patients undergoing cardiac surgery, the postoperative bleeding tendency observed in these patients might be strengthened by nitrates. Therefore, we compared the acute effects of nitroglycerin (0.5 μg kg^-1 min^-1) and isosorbide dinitrate (0.5 or 2.5 ng kg^-1 min^-1) with those of placebo on platelet function both before and after cardiopulmonary bypass in 40 patients undergoing coronary artery bypass grafting (CABG). Bleeding time, platelet retention on glass beads, i.e. platelet adhesiveness, and thromboel-astograph tracings were used as indicators of platelet function. Although nitroglycerin and isosorbide dinitrate induced significant haemodynamic changes, e.g. decreases in arterial and pulmonary arterial pressure, they had no significant effects on the indices of platelet function. We conclude that, when given in haemodynamically effective doses, neither nitroglycerin nor isosorbide dinitrate have any measurable acute effect on platelet function as evaluated with on-site tests in patients undergoing CABG surgery.