[The effect of nitrous oxide anesthesia combined with low dose alfentanil for minor surgery of short duration].

Abstract

This study was conducted in 30 adult patients with ASA class I-II physical status who received minor operations. Anesthetic induction was achieved by injecting thiopental 4 mg/kg intravenously in addition to N2O/O2 (4L/2L) delivered via Ventri Mask, followed by alfentanil 7 micrograms/kg intravenously 3 min later. Maintenance of anesthesia was accomplished by N2O/O2 in conjunction with alfentanil 0.25-2.5 micrograms/kg/min, delivered intravenously by a syringe pump. Our result showed that in an operation of average duration around 40.2 +/- 10.5 min., the average dose of alfentanil used was 0.62 +/- 0.15 micrograms/kg/min. The respiration rate fell from 13.4 +/- 0.4 cpm to 8.4 +/- 1.1 cpm 2 min later following alfentanil injection, which was statistically significant. SaO2 fell from 97.9 +/- 0.4% to 94.0 +/- 0.8% 3 min after alfentanil injection, which was statistically significant. End-tidal carbon dioxide partial pressure elevated from 39.4 +/- 0.6 mmHg to a peak of 45.3 +/- 1.2 mmHg 5 min after alfentanil injection which was also statistically significant. Temporary apnea was noted in 3 cases, but they all resumed spontaneous respiration after a short period of assisted ventilation. Changes in systolic and diastolic pressure during anesthesia were not marked. Pulse rate was noted to decrease from 80.3 +/- 2.7 bpm to 70.5 +/- 2.0 bpm 1 min after alfentanil injection, which was statistically significant (p less than 0.05). After discontinuation of N2O, the time required to regain the ability to follow orders of "open your eyes," "show your thumb" and "say your name" in sequence was 72.5 +/- 10.6s, 88.2 +/- 11.6s, 128.1 +/- 23.0s, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)