Intravenous infusion of lidocaine significantly reduces propofol dose for colonoscopy: a randomised placebo-controlled study.

BACKGROUND: Propofol use during sedation for colonoscopy can result in cardiopulmonary complications. Intravenous lidocaine can alleviate visceral pain and decrease propofol requirements during surgery. We tested the hypothesis that i.v. lidocaine reduces propofol requirements during colonoscopy and improves post-colonoscopy recovery. METHODS: Forty patients undergoing colonoscopy were included in this randomised placebo-controlled study. After titration of propofol to produce unconsciousness, patients were given i.v. lidocaine (1.5 mg kg-1 then 4 mg kg-1 h-1) or the same volume of saline. Sedation was standardised and combined propofol and ketamine. The primary endpoint was propofol requirements. Secondary endpoints were: number of oxygen desaturation episodes, endoscopists' working conditions, discharge time to the recovery room, post-colonoscopy pain, fatigue. RESULTS: Lidocaine infusion resulted in a significant reduction in propofol requirements: 58 (47) vs 121 (109) mg (P=0.02). Doses of ketamine were similar in the two groups: 19 (2) vs 20 (3) mg in the lidocaine and saline groups, respectively. Number of episodes of oxygen desaturation, endoscopists' comfort, and times for discharge to the recovery room were similar in both groups. Post-colonoscopy pain (P<0.01) and fatigue (P=0.03) were significantly lower in the lidocaine group. CONCLUSIONS: Intravenous infusion of lidocaine resulted in a 50% reduction in propofol dose requirements during colonoscopy. Immediate post-colonoscopy pain and fatigue were also improved by lidocaine. CLINICAL TRIAL REGISTRATION: NCT 02784860.

Propofol EC50 for inducing loss of consciousness is lower in the luteal phase of the menstrual cycle.

BACKGROUND: Varying levels of female sex hormones during the menstrual cycle were found to influence the central nervous system. The goal of the present study was to investigate whether the median (50%) effective effect-concentration (EC50) of propofol inducing loss of consciousness (LOC) varies between the luteal and the follicular phases of the menstrual cycle. METHODS: Twenty-two patients (follicular phase) and 20 patients (luteal phase) undergoing gynaecological procedures under general anaesthesia were enrolled on the study. Anaesthesia was conducted with a target-controlled infusion (TCI) of propofol. The initial target effect-site propofol concentration (Ceprop) was 3.5 µg ml(-1) and was adjusted stepwise by 0.5 µg ml(-1) at 4 min intervals by an up-down sequential method to reach LOC. Anaesthesia was maintained with a propofol TCI guided by the bispectral index. The correlation between female sex hormones and predicted Ceprop at the time of LOC was analysed and emergence time from anaesthesia was recorded. RESULTS: Propofol EC50 to induce LOC was higher in patients in the follicular phase than those in the luteal phase (4.17 vs 3.58 µg ml(-1), P<0.05). Progesterone correlated significantly with Ceprop at LOC. Emergence time was also longer in the follicular group than in the luteal group (6.5 vs 5.0 min, P<0.05). CONCLUSIONS: During general anaesthesia, patients in the luteal phase of the menstrual cycle had a lower propofol EC50 for LOC and a shorter emergence time compared with those in the follicular phase. Differences in progesterone levels between menstrual phases may contribute to these anaesthetic effects. Registry number of clinical trial ChiCTR-RCH-12002755.