Low-dose fentanyl-midazolam combination improves sevoflurane induction in adults

We investigated the effects of a combination of low-dose fentanyl-midazolam premedication on the speed of inhaled induction with sevoflurane and ProSeal laryngeal mask airway (PLMA) insertion conditions.

Eighty adult patients undergoing elective surgery were randomized in a double-blind fashion to receive either a normal saline placebo (Group PLAC) or a fentanyl 0.6 microg x kg(-1) and midazolam 9 microg x kg(-1) premedication (Group FM) 5 min before tidal volume sevoflurane 8%/O(2) induction. Anxiety levels, times to loss of eyelash reflex (LER) and PLMA insertion, and cardiorespiratory data were recorded.

Times to LER (Group PLAC: 66 +/- 34 sec vs Group FM: 47 +/- 18 sec, P = 0.0027, difference = 19 sec: 95% confidence interval [CI] 7-31 sec) and to PLMA insertion (Group PLAC: 186 +/- 80 sec vs Group FM: 119 +/- 44 sec, P < 0.0001, difference = 68 sec: 95% CI 39-97 sec) were shorter following FM. After PLMA insertion, end-tidal sevoflurane concentration (EtSevo) was lower and end-tidal CO(2) (EtCO(2)) was higher following FM. Respiratory rate (RR) was lower with FM, but there was no difference regarding tidal volume. Adverse events, such as movements and apnea, occurred more often in Group PLAC. Systolic blood pressure (SBP) and heart rate (HR) during induction were both lower with FM. Anxiety level after premedication was lower following FM administration. All participants remembered the face mask being applied in Group PLAC vs 69% in Group FM, P < 0.0001.

Administration of a low-dose fentanyl-midazolam combination prior to sevoflurane induction decreases time to LER and allows for more rapid and less eventful PLMA insertion. Both SBP and HR were lower when premedication was administered. Patients receiving premedication were less anxious and less likely to remember the face mask. However, premedication was associated with a lower RR and increased EtCO(2) values following PLMA insertion, in spite of lower EtSevo concentrations. (ClinicalTrials.gov ID NCT00723164).