Study Objective: To measure the hemodynamic changes produced by nitrous oxide (N20) during halothane and isof lurane anesthesia in infants and children. Design: A repeated measures design in two groups of infants and small children. Setting: Operating rooms at a university hospital. Patients: Nineteen healthy unmedicated infats and small children (mean age 12 months) who required elective surgery. Interventions: Prior to anesthesia induction, cardiovascular measurements were recorded using pulsed Doppler and two-dimensional echocardiography. Following anesthesia induction with halothane (n = 10) or isof lurane (n = 9) in oxygen (O2) and air, anesthetic measures were stabilized at 1.0 minimum alveolar concentration (MAC) and cardiovascular measures were repeated. After 30% N20 was added to the 1.0 MAC anesthetic concentrations, a third set of cardiovascular measurements was recorded. A final cardiovascular data set was measured 5 minutes following an increase in N20 concentration to 60%. Measurements and Main Results: Mean arterial pressure (MAP), cardiac index (CI), stroke volume (SV), and ejection fraction (EF) decreased similarly and significantly at 1.0 MAC halothane and isof lurane. Heart rate (HR) increased during isoflurane anesthesia but decreased during halothane anesthesia. The addition of N2O resulted in a decrease in HR, CI, and MAP when compared to 1.0 MAC levels of halothane or isof lurane; however, SV and EF were not significantly changed from levels measured during 1.0 MAC halothane or isof lurane. Conclusions: The addition of N2O to halothane and isoflurane anesthesia in infants and children decreased HR. This decrease led to a decrease in cardiac output (CO). Unlike with adults, N20 did not produce cardiovascular signs of sympathetic stimulation in infants and children.
- nitrous oxide