Pulsed Doppler and Two-dimensional Echocardiography

Open Access
Publisher Website
Google Scholar
Abstract
The combination of two-dimensional and pulsed Doppler-echocardiography was used to measure determinants of cardiac function in 20 ASA physical status I infants and small children (9 days-32 months of age) during equipotent halothane (n = 10) or isoflurane (n = 10) anesthesia in oxygen. Five sets of cardiovascular data were recorded in each patient. In the awake, unmedicated state prior to induction, at three different anesthetic levels, 0.75, 1.0, and 1.25 MAC (corrected for age) and a final measurement repeated at 1.25 MAC after the intravenous infusion of 15 ml .cntdot. kg-1 of Lactated Ringers solution. The study was completed prior to intubation and surgery. Results are expressed as mean .+-. SEM. Isoflurane and halothane decreased mean blood pressure from the awake level (isoflurane 76.6 .+-. 2.3 to 60.6 .+-. 3.1 mm, halothane 72.2 .+-. 3.9 to 60.6 .+-. 3.1 mm at 1.25 MAC). Isoflurane increased heart rate at all anesthetic levels (128.7 .+-. 4.2 to 142.5 .+-. 6.0 beats/min at 0.75 MAC). Halothane decreased heart rate at 1.25 MAC (124.6 .+-. 4.6 to 119.4 .+-. 3.5 beats/min). Isoflurane and halothane decreased cardiac index at 1.25 MAC. Stroke volume index decreased at 1.0 and 1.25 MAC with both isoflurane (36.9 .+-. 3.8 to 30.2 .+-. 3.5 ml/m2) and halothane (32.7 .+-. 2.5 to 28.9 .+-. 2.5 ml/m2). Ejection fractions also decreased significantly at 1.0 and 1.25 MAC in both groups of patients (22 .+-. 6% at 1.25 MAC halothane and 28 .+-. 8% at 1.25 MAC isoflurane). Left ventricular end-diastolic and end-systolic volumes increased in the halothane and isoflurane group to a similar degree. After 15 ml .cntdot. kg-1 of LR, ejection fraction, and stroke volume index decreased significantly in the halothane group, but increased sigificantly in the isoflurane group. This response to fluid may indicate that greater cardiovascular reserve exists during isoflurane anesthesia than during halothane anesthesia in infants and small children.