Right ventricular function after normothermic versus hypothermic cardiopulmonary bypass

Continuous cold blood cardioplegia improves myocardial protection: a prospective randomized study

BACKGROUND

To assess the influence on myocardial protection of the rate of infusion (continuous vs intermittent) of cold blood cardioplegia administered retrogradely during prolonged aortic cross-clamping. The end-points were ventricular performance and biochemical markers of ischemia.

METHODS

Seventy patients undergoing myocardial revascularization for three-vessel disease were prospectively randomized to receive intermittent or continuous retrograde cold blood cardioplegia. Hemodynamic measurements were obtained using a rapid-response thermodilution catheter and included right ventricular ejection fraction, cardiac output, left and right ventricular stroke work index, and systemic and pulmonary vascular resistance. Blood samples were obtained from the coronary sinus before cross-clamp application and immediately after cross-clamp removal for determinations of lactate and hypoxanthine.

RESULTS

The left ventricular stroke work index trend was significantly superior (p = 0.038) by repeated-measures analysis in continuous cardioplegia. Other hemodynamic measurements revealed a similar trend. The need for postoperative inotropic drugs support was reduced in continuous cardioplegia. The release of lactate in the coronary sinus after unclamping was 2.30 +/- 0.12 mmol/L after intermittent cardioplegia and 1.97 +/- 0.09 mmol/L after continuous cardioplegia (p = 0.036). The release of hypoxanthine was 20.47 +/- 2.74 micromol/L in intermittent cardioplegia and 11.77 +/- 0.69 micromol/L in continuous cardioplegia (p = 0.002).

CONCLUSIONS

Continuous cold blood cardioplegia results in improved ventricular performance and reduced myocardial ischemia in comparison with intermittent administration.

A comparative study between hypothermic and normothermic cardiopulmonary bypass in open heart surgery in dogs--effects on systemic hemodynamics

Open heart surgery was performed on two groups of dogs under extracorporeal circulation with or without hypothermia to investigate hemodynamic changes during extracorporeal circulation. During hypothermic cardiopulmonary bypass (CPB), arterial O2 tension and postoperative blood pressure were favorably maintained, indicating that hypothermic extracorporeal circulation can be performed for a long period of time. On the other hand, during normothermic CPB, the average surgical duration was significantly shorter, and marked shifts in the concentrations of various enzymes were suppressed. However, due to reductions in arterial O2 tension, the length of cardiac arrest time was restricted, demonstrating that this method is suitable for performing extracorporeal circulation for CPB of relatively short duration. If circulation circuitry can be improved, such as through the development of a surpassing oxygenator, normothermic CPB would incur less stress on the body, thus making it preferential to hypothermic CPB in most cases.

Influence of normothermic systemic perfusion temperature on cold myocardial protection during coronary artery bypass surgery

OBJECTIVE

To determine the effect of normothermic systemic perfusion on myocardial injury when using cold cardioplegic techniques in patients undergoing coronary artery bypass surgery.

METHOD

Sixty six patients with stable angina pectoris were prospectively randomized into three groups according to cardiopulmonary bypass temperature: hypothermia (28 degrees C, n = 22), moderate hypothermia (32 degrees C, n = 22) and normothermia (37 degrees C, n = 22). All patients received cold antegrade crystalloid cardioplegia and topical cooling with saline at 4 degrees C. Serum samples were collected for troponin T and I estimation preoperatively, 4 hours after removal of the aortic cross clamp, and 12, 24, 36 and 48 hours postoperatively. In addition, serial electrocardiographic studies were undertaken on days 1, 3 and 5.

RESULTS

Patients were similar with regard to preoperative and intraoperative characteristics Four patients showed ECG changes typical of perioperative myocardial infarction but remained clinically well (28 degrees C, one; 32 degrees C, one; 37 degrees C, two). In the remaining 62 patients, serum troponin T increased significantly from a mean baseline value of 0.02 ng/ml to 1.5+/-0.9 ng/ml 4 hours after removal of the aortic cross-clamp (P<0.0001). Similarly, troponin I increased from 0.06 ng/ml to 0.63+/-0.47 ng/ml 12 hours after reperfusion (P<0.0001). Serum concentrations of both markers subsequently declined with time but remained higher than preoperative values at 48 hours. There were no differences between the three groups with respect to peak and cumulative serum troponin release. Normothermic cardiopulmonary bypass did not compromise the efficacy of cold myocardial protection when assessed by serum troponin concentrations in low risk patients undergoing coronary revascularization.

Normothermic Cardiopulmonary Bypass

Normothermic cardiopuhnonary bypass avoids the detrimental systemic effects of hypothermia. It is a safe and effective technique of systemic perfusion during cardiopulmonaiy bypass. Myocardial preservation is not compromised when electromechanical quiescence is maintained. Cerebral protection is comparable to that of systemic hypothermia. Low vascular resistance is common and easily treated with higher perfusion flows or vasopressors during bypass and facilitates weaning from bypass. Duration of cardiopulmonary bypass is significantly shortened by the absence of systemic cooling and rewarming phases. Clinical outcomes of patients undergoing cardiac, surgery with normothermic bypass compare favorably with those receiving moderate hypothermia.

Randomized study of right ventricular function with intermittent warm or cold cardioplegia

BACKGROUND

Transient right ventricular dysfunction has been previously documented after bypass operations despite adequate myocardial protection with intermittent antegrade cold blood cardioplegia. Recently warm blood cardioplegia has been interrupted during construction of distal anastomoses to improve visualization. The effects of intermittent antegrade warm blood cardioplegia, and the resultant periods of right ventricular normothermic ischemia, on postoperative right ventricular function are unknown.

METHODS

To assess the effects of cardioplegia on right ventricular protection, 52 patients undergoing isolated bypass grafting were randomized to intermittent warm or cold blood cardioplegia. The two groups were similar with respect to age, sex, ventricular function, and right coronary stenoses. Cross-clamp times were similar (warm, 64 +/- 22 minutes; cold, 63 +/- 15 minutes; not significant). The cumulative time of cardioplegia interruption was longer in the cold group (42 +/- 8 minutes) than in the warm group (31 +/- 14 minutes; p < 0.002). A rapid-response thermodilution catheter was employed to assess postoperative right ventricular ejection fraction and end-diastolic and end-systolic volume indices.

RESULTS

The right ventricular ejection fraction was greater in the warm group at 6 hours (warm, 0.46 +/- 0.06; cold, 0.37 +/- 0.08; p < 0.05) and 8 hours (warm, 0.43 +/- 0.08; cold, 0.37 +/- 0.08; p < 0.05) postoperatively. The right ventricular end-diastolic volume index was less in the warm group 8 hours postoperatively (warm, 83 +/- 11 mL/m2; cold, 94 +/- 16 mL/m2; p < 0.05). There were no differences in pulmonary arterial pressures or right ventricular stroke work index.

CONCLUSIONS

Despite intermittent normothermic ischemia of half the cross-clamp time, patients receiving warm cardioplegia maintained right ventricular hemodynamics after bypass grafting.

Normothermic versus hypothermic perfusion during primary coronary artery bypass grafting

Normothermic versus hypothermic cardiopulmonary bypass was evaluated in 1442 consecutive patients undergoing primary coronary artery bypass grafting (CABG). Group 1 (n = 545) were operated on in moderate systemic hypothermia (rectal temperature 28 degrees C) and group 2 (n = 897) in normothermia (rectal temperature 37 degrees C). Both groups had cold cardioplegic arrest (10 degrees C) and local cooling of the heart with slush. Anaesthesia and operative techniques were identical in both groups. The mean age was 60 years; group 2 contained significantly more patients aged > 65 years (P < 0.05) and had more frequent emergency operations (P < 0.001) than group 1. Other preoperative patient characteristics were similar between groups. Aortic cross-clamping time was similar in both groups but cardiopulmonary bypass time was significantly longer in group 1 than in group 2 (97.9(28.8) versus 76.6(26.0) min, P < 0.001). Perioperative mortality rate was 3.3% in group 1 and 2.6% in group 2. The incidence of myocardial infarction was significantly higher in group 1 than in group 2 (2.0% versus 0.7%) Perioperative low cardiac output needing inotropic support was similar in both groups, but group 1 patients required more intra-aortic balloon insertions (4.6% versus 2.2%, P < 0.05). Lower incidence of postoperative ventricular arrhythmias, shorter intubation time and less transient renal failures were significant in group 2 compared with those in group 1 (P < 0.001), while re-exploration of bleeding, wound infections, pulmonary, neurological and gastrointestinal complications did not differ. Blood transfusion was less in group 2 (1.2(1.1) units, P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Stroke during coronary artery bypass grafting using hypothermic versus normothermic perfusion

Does the abandonment of hypothermic perfusion during cardiopulmonary bypass compromise cerebral protection and thus lead to a higher incidence of stroke? From 1987 to June 1993, 2,585 consecutive patients underwent myocardial revascularization using warm-body (perfusion at 37 degrees C), cold-heart (cold cardioplegic arrest) surgical technique and were followed for new overt neurologic deficits. Perfusion pressure was maintained between 50 and 70 mm Hg, and hematocrit was kept around 20%. There were 25 operative deaths (1%) in this normothermic group, and new neurologic deficits developed after operation in 25 patients (1%). These results were compared retrospectively with those in 1,605 patients who underwent myocardial revascularization between 1980 and 1986 with moderate hypothermic (25 degrees to 30 degrees C) perfusion, the same surgical team, and similar operative techniques. The normothermic group included more elderly patients, more patients with left ventricular dysfunction and unstable angina, and more frequent use of an internal mammary artery conduit. Neurologic complication rates were 1% and 1.3% for the normothermic and hypothermic perfusion groups, respectively. Risk factors for stroke that were identified included age greater than 70 years, severity of aortic arch atherosclerosis, and severe hypotension in the perioperative period. Thus, in a large clinical series, the incidence of overt neurologic injuries was found to be no higher with normothermic perfusion than with hypothermic perfusion.