Clinical correlates of dysrhythmias requiring an esophageal ECG for accurate diagnosis in patients with congenital heart disease.

Esophageal electrocardiography (EsECG) is a useful adjunct in the diagnosis of dysrhythmias that are difficult to diagnose with a conventional ECG. This study was designed to evaluate which type of dysrhythmias required the EsECG for proper diagnosis and what factors produced the rhythm problems. Sixty-eight pediatric patients undergoing cardiac surgery were studied. After release of the aortic cross-clamp, the cardiac rhythm was analyzed by a standard limb-lead ECG at five-minute intervals. Twenty-six of 68 patients exhibited rhythms during reperfusion that required the EsECG for definitive diagnosis. This group of patients was younger, had longer durations of cardiopulmonary bypass and aortic occlusion, and required more time and interventions to achieve a normal sinus rhythm. The likelihood of difficult dysrhythmias was not related to the type of surgical procedure performed.

Myocardial recovery from the cardiac depressant effects of enflurane and halothane.

Recovery from the cardiac depressant effects of enflurane and halothane was examined in the dog heart-lung preparation (HLP) and in right ventricular muscle isolated from guinea pig hearts. In the HLP. recovery was studied under two conditions: (1) After a two-hour exposure to anesthetic concentrations increasing from 0.36 to 1.2 MAC, and (2) after a one-hour exposure to a single concentration that raised the left atrial pressure (LAP) to 9 to 10 mmHg. Under either condition, +dP/dtmax. was significantly less depressed with enflurane and returned to preanesthetic control levels, while recovery with halothane remained significantly below control. Following the longer exposure. recovery of the LAP and left ventricular function curves (LVFC) was significantly less with halothane; however, this difference was not observed after the shorter exposure period. In electrically paced, isometrically contracting right ventricular strips exposed for one hour to 2.25 vol% enflurane (a concentration that reduced contractility by 45%), force development returned within 60 minutes to values above preanesthetic control values. After an identical depression for one hour with halothane (0.80 vol%), force development recovered to values less than those observed following enflurane. These data indicate that the recovery from anesthetic-induced negative inotropic effects in isolated cardiac preparations is better with enflurane than halothane.

Effects of cardiopulmonary bypass on eicosanoid metabolism during pediatric cardiovascular surgery.

Cardiopulmonary bypass in children with congenital heart disease is associated with significant morbidity manifested by increased complement degradation products, heightened pulmonary vascular activity, and coagulopathy. In adults with cardiac disease, the prostaglandins (eicosanoids) have been shown to contribute to the pathophysiologic response to extracorporeal circulation. This study assessed the effect of cardiopulmonary bypass in infants and children on two potent eicosanoids: thromboxane, a vasoconstrictor and platelet aggregating agent, and prostacyclin, a vasodilator and platelet disaggregating agent. The biochemical profiles of thromboxane and prostacyclin were evaluated in temporal relationship to selected parameters of platelet loss and pulmonary vascular hemodynamics during and after cardiopulmonary bypass. Twenty-one children, aged 3 days to 9 years, with congenital heart defects who were undergoing repair with cardiopulmonary bypass were studied. Nine pediatric patients undergoing palliative heart operations with no cardiopulmonary bypass served as the control group. In the group having cardiopulmonary bypass, the thromboxane concentration significantly increased during bypass (195 +/- 10 to 910 +/- 240 pg/ml, +/- standard error of the mean, p less than 0.005), whereas the control group demonstrated no significant change in thromboxane concentration. The highest thromboxane values were seen in the youngest patients (p less than 0.002). There was no significant correlation between thromboxane changes with alterations in pulmonary vascular resistance, platelet loss, duration of cardiopulmonary bypass or aortic cross-clamping. Prostacyclin levels rose significantly in both the bypass group (100 +/- 20 to 570 +/- 80 pg/ml, p less than 0.01) and in the control group (109 +/- 44 to 589 +/- 222 pg/ml, p less than 0.01), which apparently is due to surgical manipulation of vascular endothelium. These data show that eicosanoid production is significantly altered in children during cardiopulmonary bypass. Although thromboxane, a potent vasoconstrictor, is produced in significant amounts during and after cardiopulmonary bypass, our data show that thromboxane does not directly mediate changes in pulmonary artery hypertension and is not quantitatively related to platelet loss during pediatric cardiovascular operations.

Comparison of cardiac effects of enflurane, isoflurane, and halothane in the dog heart-lung preparation.

Minimum alveolar concentration (MAC) was determined in intact dogs (N = 10 for each anesthetic) to be 2.12 +/- 0.04 vol% for enflurane (ENF), 1.28 +/- 0.04 vol% for isoflurane (ISO), and 0.94 +/- 0.03 vol% for halothane (HAL). Then, the direct cardiac effects of these three anesthetics were studied at 0.36, 0.6, 1.0, and 1.2 MAC in the dog heart-lung preparation (HLP): an in situ whole heart preparation devoid of major extracardiac influences and reflex control. All three agents produced concentration-dependent decreases in heart rate (HR) that became significantly different from control at 0.6 MAC. HAL and ISO reduced +dP/dtmax by the same degree at all MAC levels, becoming statistically significant at 0.6 MAC, while a significant reduction in +dP/dtmax for ENF occurred first at 1.0 MAC. Marked increases in left atrial pressure (LAP) were observed at 1.0 MAC for all anesthetics and the first significant depression of systemic output (SO) occurred at 1.0 MAC. Each agent produced significant shifts of the left ventricular function curves (LVFC) to the right with each consecutive MAC fraction. Marked reductions in the slope of the LVFC were first observed at 1.0 MAC, and this change in slope was more pronounced with ENF. At 1.2 MAC, ENF seemed to produce a more severe cardiodepression than HAL or ISO, as suggested by a greater incidence of cardiac failure; however, this was not statistically significant. In general, the data suggest that at MAC fractions up to 0.6, ENF is less cardiodepressant than ISO or HAL, but that ENF has a tendency to be more depressant than HAL or ISO at concentrations higher than 1.0 MAC.