The effect of total intravenous propofol on spontaneous respiration during anesthesia for minor surgery

To evaluate adequate anesthetic depth without unacceptable respiratory consequences during total propofol intravascular anesthesia without intubation, the respiratory response was studied in 20 healthy patients (ASA class I or II), aged 20-50, premedicated with fentanyl 2 micrograms/kg. Anesthesia was induced in all patients with propofol 2.5 mg/kg, subsequently maintained by continuous propofol infusion at 12 mg/kg/h. An additional bolus of 20-60 mg propofol was given when anesthesia was considered inadequately. Assisted ventilation with 100% oxygen through a face mask was applied when apnea time was longer than 60 s. The mask was removed when patients regained spontaneous breathing. During induction stage, 7 patients developed apnea which required ventilatory support, although the period of apnea was short. Among them four regained spontaneous breathing within 5 min, and three within 10 min. PaCO2 significantly increased at both 10 min and 20 min after induction as compared with those before induction (p less than 0.05), while the change between 10 min and 20 min after induction was not statistically different. PaO2 showed little change and also it was not statistically significant. During maintenance of anesthesia spontaneous ventilation was stable and adequate. Though mild hypercapnia was noted, no medication was necessary. There was no episode of arterial oxygen desaturation throughout the course of maintenance. All patients could be adequately anesthetized except for six patients who required additional dose for insufficient anesthetic depth. No major adverse reactions occurred during or after induction. We concluded that the respiratory effect of propofol in total intravenous anesthesia could be divided into two stages: the induction stage and the maintenance stage.(ABSTRACT TRUNCATED AT 250 WORDS)