Preoperative paracetamol infusion reduces sevoflurane consumption during thyroidectomy under general anesthesia with spectral entropy monitoring

Background
Intravenous (IV) paracetamol has a significant opioid-sparing effect. We investigated the effect of paracetamol infusion on sevoflurane consumption during entropy monitored general anesthesia.
Methods
Sixty-two ASA I and II patients undergoing thyroidectomy under general anesthesia were included in a prospective, randomized, double-blind and placebo controlled study. The patients were randomized to receive a slow infusion of either 1 g paracetamol (paracetamol group,  = 31) or saline (control group,  = 31) just before induction of anesthesia. Sevoflurane concentration was titrated to keep the state entropy value between 40 and 50. End-tidal sevoflurane concentration, sevoflurane consumption, recovery characteristics, time to first analgesic request and meperidine consumption during the first 6 postoperative hours were recorded.
Results
The mean ± SD estimated sevoflurane consumption was significantly lower in the paracetamol treated patients (36.2 ± 15 vs 44.9 ± 13.9 ml, in the control group;  = 0.021). Patients receiving paracetamol had a faster post-anesthetic recovery profile (extubation time, time to eye opening to command and time to state name and mention his/her home address) than the other group ( < 0.05). Mean ± SD time to first analgesic request was significantly prolonged in paracetamol group compared to control group (48.4 ± 14.0 vs 40.7 ± 11.5 min, respectively;  = 0.021). Meperidine consumption was higher in control group than in paracetamol group (28.7 ± 10.2 vs 23.1 ± 9.0 mg, respectively;  = 0.025).
Conclusion
Preoperative IV paracetamol infusion improved consumption and emergence from entropy monitored sevoflurane anesthesia with enhancement of the early postoperative analgesia.