Cardiovascular response to endotracheal intubation during four anesthetic techniques

In order to investigate the impact of four different anesthetic regimens on the cardiovascular response to endotracheal intubation, 24 patients were anesthetized to approximately the same depth of anesthesia (MAC-fraction) using one of four supplements to N2O-O2 (60:40) anesthesia: Group 1 = morphine 0.5 mg/kg i.v., Group 2 = Innovar 0.1 ml/kg i.v., Group 3 = halothane, 0.4% end-tidal, Group 4 = enflurane 0.7% end-tidal. Cardiovascular variables were recorded from radial arterial and thermistor-tipped pulmonary artery catheters and were determined at the following times: (1) while the patients were awake prior to induction of anesthesia; (2) after a stable level of anesthesia had been induced; and (3) within the first minute after endotracheal intubation. Only the groups receiving morphine and halothane sustained significant increases in heart rate, rate pressure product and pulmonary capillary wedge pressure after intubation. It is concluded that N2O-O2 anesthesia supplemented with either morphine or halothane at the 1 MAC dose level does not adequately prevent cardiovascular response after endotracheal intubation, and that these techniques require additional anesthetic depth or other adjuvant drugs in order to prevent cardiovascular complications.