The Effect of Age on the Cardiovascular Responses Induced by High Concentration of Isoflurane / 대한마취과학회지

BACKGROUND: The inhalation of a high concentration of isoflurane transiently increases heart rate (HR) and blood pressure. The current study examined the effects of age on isoflurane-induced circulatory responses. METHODS: One hundred-ten patients were randomly allocated into one of four groups according to age: under 10 years (Group 1), 20 - 40 years (Group 2), 41 - 60 years (Group 3), and over 65 years (Group 4). In each group, the inspired concentration of isoflurane via mask was increased to 5.0 vol% abruptly. The target was to produce an end-tidal concentration of isoflurane (ETisof) of 2.6 vol% which was maintained until the end of the study by adjusting the vaporizer setting when necessary. HR, mean arterial pressure (MAP), ETisof, and end-tidal concentration of carbon dioxide were measured at baseline and every 30 seconds for 5 minutes after inhalation of isoflurane and for 2 minutes after intubation. RESULTS: HR and MAP significantly increased after inhalation of isoflurane in all four groups compared with the baseline. The time from administration of isoflurane to the maximal HR was less than that for MAP. However, there were no significant differences among the groups for ETisof at the maximal HR and MAP. In Groups 1 and 4, the times for maximal HR were shorter than in Groups 2 and 3. In aged patients (Group 4), the isoflurane-induced HR increase was less than in the other three groups. There were no significant differences among the groups in increases of MAP. CONCLUSIONS: The high concentration of isoflurane transiently increases HR and MAP during inhaled anesthesia induction. In aged patients, the increase in HR is less than in younger-aged patients.

The Effects of the Rate of Increase in Inhaled Isoflurane Concentration on the Circulatory Responses / 대한마취과학회지

BACKGROUND: A rapid increase in isoflurane concentration induces tachycardia and hypertension and increases plasma catecholamine concentration. The current study examined the effects of the rate of increase in inhaled isoflurane concentration on the circulatory responses. METHODS: Unpremedicated sixty three ASA physical status 1 patients, aged 20-40 years, scheduled for elective surgery under general anesthesia were randomly allocated into one of three groups. In each group, the inspired concentration of isoflurane via mask was increased up to 5 vol% at the rate different from other groups. The inspired concentration of isoflurane via mask was increased to 5.0 vol% abruptly (group 1), for 100 seconds (group 2), or 200 seconds (group 3). The target was to produce an end-tidal concentration of isoflurane (ETisof) of 2.6 vol% which was maintained until the end of the study by adjusting the vaporizer setting, when necessary. Heart rate (HR), mean arterial pressure (MAP), ETisof, end-tidal concentration of carbon dioxide, and peripheral oxygen saturation were measured at baseline and every 30 seconds for 5 minutes after inhalation of isoflurane and for 2 minutes after intubation. RESULTS: HR and MAP were significantly increased in all three groups compared with baseline, but significant differences in maximum values were not observed in three groups. There were significant differences among the groups in time from the onset of isoflurane inhalation to the maximal effect on HR and MAP. However, there were no significant differences among the groups of the ETisof at the maximal HR and MAP were seen. CONCLUSIONS: The high concentration of isoflurane transiently increase HR and MAP during inhaled anesthesia induction. However, the rate of increase in inhaled isoflurane concentration does not affect the circulatory responses.