[Hemodynamic changes during the induction phase of halothane-nitrous oxide anesthesia in childhood]

The haemodynamic effects of halothane nitrous oxide anaesthesia were studied in 15 children aged 4-13 using measurements of heart rate, blood pressure and impedance cardiography. The preinduction (control) measurements were compared with measurements obtained one minute after inhalation of nitrous oxide and oxygen, at the beginning of the stage of excitation, at the beginning of the stage of tolerance and after the injection of 0.02 mg/kg atropine. During the induction period blood pressure decreased significantly, while heart rate remained unchanged. Cardiac output was significantly decreased at the stages of excitation and tolerance. Virtually no change in total peripheral resistance occurred. After atropine significant increases in heart rate, mean arterial blood pressure and total peripheral resistance were measured. Cardiac output was increased compared with the pre-atropine values, but not with the control value. Impedance cardiography is a useful non-invasive method of measuring changes of stroke volume during paediatric anaesthesia.