Comparative hemodynamic depression of halothane versus isoflurane in neonates and infants: an echocardiographic study.

The purpose of this study was to measure and compare the relationship of cardiovascular depression and dose during equal potent levels of halothane and isoflurane anesthesia in neonates (n = 19) (16.7 ± 6.9 days) and infants (n = 54) (6.1 ± 3.1 mo). Seventy-three children had heart rate, arterial blood pressure, and pulsed Doppler pulmonary blood flow velocity as well as two-dimensional echocardiographic assessments of left ventricular area and length recorded just before anesthesia induction. Anesthesia was induced by inhalation of increasing inspired concentrations of halothane or isoflurane in oxygen using a pediatric circle system and mask. During controlled ventilation, halothane and isoflurane concentrations were adjusted to maintain 1.0 MAC and then 1.5 MAC (corrected for age), and echocardiographic and hemodynamic measurements were repeated. A final cardiovascular measurement was recorded after intravenous administration of 0.02 mg/kg of atropine. All measurements were completed before tracheal intubation and the start of elective surgery. In neonates, 1.0 MAC concentrations of halothane and isoflurane decreased cardiac output (74% ± 16%), stroke volume (75% ± 15%), and ejection fraction (76% ± 15%) similarly from awake levels. Decreases in cardiac output, stroke volume, and ejection fraction with halothane and isoflurane were significantly larger at 1.5 MAC (∼35% decreases from awake values) than at 1.0 MAC. Heart rate decreased significantly during 1.5 MAC halothane anesthesia (94% ± 4%) but remained unchanged during isoflurane anesthesia. In infants, 1.0 MAC halothane and isoflurane decreased cardiac output (83% ± 12%), stroke volume (78% ± 12%), and ejection fraction (74% ± 12%) when compared with awake measures. Heart rate decreased during 1.0 MAC halothane anesthesia but increased during 1.0 MAC isoflurane. When anesthetic concentrations were increased to 1.5 MAC, stroke volume (71% ± 12% of awake) and ejection fraction (64% ± 13% of awake) decreased similarly from the 1.0 MAC measurement in both groups. When compared with 1.0 MAC, heart rate decreased further at 1.5 MAC halothane anesthesia (80% ± 5% of awake) but remained unchanged during 1.5 MAC isoflurane anesthesia (106% ± 4% of awake). Atropine (0.02 mg/kg) increased heart rate and cardiac output by 15%-20% from measurements at 1.5 MAC halothane and isoflurane anesthesia in neonates and infants, but stroke volume and ejection fraction remained unchanged from measurements before atropine administration in both groups. Equipotent halothane and isoflurane produced similar hemodynamic depression in neonates and infants.