Effects of Inhaled Nitrous Oxide on the Induction Dose and Time Requirements of Propofol: A Prospective, Randomized, Double-blind Study.

CONTEXT: Propofol is a commonly used induction agent during general anesthesia. As a sole agent, it does not provide any strong analgesic effect. The nitrous oxide (N2O) used along with propofol for induction of anesthesia augments the induction characteristics and reduces the dose of propofol.

AIMS: To study the effects of inhaled N2O on the induction dose and time of propofol during general anesthesia and also its hemodynamic response and adverse effects.

SETTINGS AND DESIGN: The present research is a prospective, randomized, double-blind comparative study.

SUBJECTS AND METHODS: The study population consisted of eighty patients aged 18-60 years from either sex, American Society of Anesthesiologists physical status 1 and 2 which were scheduled for various elective surgical procedures under general anesthesia. The patients were randomly allocated into two groups comprising forty patients in each group. All patients were premedicated with glycopyrrolate 0.2 mg, ondansetron 4 mg, and fentanyl 1 μg/kg intravenously. Group FN received breathing mixture of gases (67% N2O @ 4 L/min and 33% O2 @ 2 L/min), and propofol and Group FO received 100% O2 @ 6 L/min and propofol. The different hemodynamic parameters (heart rate, mean arterial pressure, systolic blood pressure, diastolic blood pressure, and SpO2) were measured.

STATISTICAL ANALYSIS: All observations were analyzed using Chi-square test, Student's t-test, and analysis of variance.

RESULTS: The mean induction time and dose were significantly less in Group FN as compared to Group FO (P < 0.05). The mean induction time was 172 ± 32 s in Group FN as compared to 242 ± 43 s in Group FO (P < 001), whereas the mean induction dose was 56.10 ± 13.92 mg in Group FN as compared to 81.67 ± 17.64 mg in Group FO (P < 0.05). The hemodynamic parameters remained stable with no complications.

CONCLUSION: The coadministration of N2O during induction of anesthesia with propofol not only reduced the induction dose of propofol but also reduced induction time significantly. Furthermore, it provided stable hemodynamics without any complications.