Background: It was suggested that hypoxemia, hypercapnea or apnea occur following administration of flumazenil in patients previously sedated with benzodiazepines alone or in combination with opiates. This prospective, randomized study tested this contention and the possible correlation between reversal of sedation and respiratory parameters. Methods: Seventy-eight patients who underwent lower abdominal surgery under general anesthesia (Group GA, n =24) or epidural block (Groups EMD, n =26, and ED=28) comprised the study groups. GA and EMD patients were premedicated with diazepam 10 mg PO and morphine sulphate 0.1 mg.,kg-1, IM; ED patients received only diazepam. IV meperidine (total of 1 mg.,kg-1,) and midazolam (0.1 mg.,kg-1,) were intermittently administered intraoperatively to GA and EMD; ED patients received only midazolam. In the recovery room, while all subjects were breathing room air, flumazenil 1 mg was administered randomly to one half of each groups. Results: Six patients suffered from hypoxemia (SpO2, < 90% for ±15 sec) before study started. No apnea, increase in end-expiratory CO2 (ETCO2) or decrease in pulse oxymetry (SpO2,) were observed during the study. Sedation was reversed promptly, lasting 45 (ED), 3 0 (EMD) and 10 min (GA). Ninety percent of ED-treated patients were vigil (lying with eyes open) twice as long as GA- and EMD-treated patients. SpO2, in GA- and EMD-treated patients did not change after flumazenil; it increased in the ED subgroup where ET,CO2, decreased and respiratory rate increased too. Sedation score significantly (P =0.0000) correlated with SpO2, in ED- and EMD-treated patients (rp,=-0.92, -0.96, respectively) and with ET,C02, in GA-treated patients only (P<0.05, rp,=-0.88). Heart rate and blood pressure did not change following flumazenil administration. Conclusions: Flumazenil does not cause deterioration in respiratory parameters after benzodiazepines alone or when combined with meperidine, but rather ameliorates them. Significant close correlation between reversal of sedation and SpO2, exists under epidural and general anesthesia.

Keywords: Benzodiazepines, opiates, Flumazenil, sedation, pulse oxymetry, end-expiratory carbon dioxide