Intra-operative lidocaine in the prevention of vomiting after elective tonsillectomy in children: A randomised controlled trial.

BACKGROUND: Postoperative vomiting (POV) is a frequent complication of tonsillectomy in children. In adult patients undergoing abdominal surgeries, the use of intravenous lidocaine infusion can prevent POV. OBJECTIVE: To evaluate the anti-emetic effect of an intravenous lidocaine infusion used as an adjuvant to general anaesthesia, in children undergoing elective ear, nose and throat surgery. DESIGN: Double-blind, randomised, controlled study. SETTING: Hospital-based, single-centre study in Chile. PATIENTS: ASA I-II children, aged 2 to 12 years, scheduled for elective tonsillectomy. INTERVENTION: We standardised the induction and maintenance of anaesthesia. Patients were randomly allocated to lidocaine (1.5 mg kg intravenous lidocaine over 5 min followed by 2 mg kg h) or 0.9% saline (at the same rate and volume). Infusions were continued until the end of the surgery. MAIN OUTCOME MEASURES: Presence of at least one episode of vomiting, retching or both in the first 24 h postoperatively (POV). SECONDARY OUTCOMES: Plasma concentrations of lidocaine and postoperative pain. RESULTS: Ninety-two children were enrolled. Primary outcome data were available for 91. In the Lidocaine group, 28 of 46 patients (60.8%) experienced POV, compared with 37 of 45 patients (82.2%) in the Saline group [difference in proportions 21.3% (95% confidence interval (CI) 2.8 to 38.8), P = 0.024]. The intention-to-treat analysis showed that when we assumed that the patient in the Saline group lost to follow-up did not have POV, the difference in proportions decreased to 19.6% (95% CI, 0.9 to 37.2), with an unadjusted odds ratio of 0.38 (95% CI, 0.15 to 0.97, P = 0.044). The odds of having POV were 62% less likely in those patients receiving lidocaine compared with patients in the Saline group. The mean lidocaine plasma concentration was 3.91 µg ml (range: 0.87 to 4.88). CONCLUSION: Using an intravenous lidocaine infusion as an adjuvant to general anaesthesia decreased POV in children undergoing elective tonsillectomy. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01986309.

Dexmedetomidine pharmacokinetics in the obese.

PURPOSE: This study aims to characterize the influence of body weight and composition on the pharmacokinetics of dexmedetomidine. METHODS: Twenty obese patients and 20 non-obese patients scheduled for elective laparoscopic surgery were given dexmedetomidine infusion schemes. Venous blood samples were taken during and after dexmedetomidine administration. Population pharmacokinetic modeling was undertaken to investigate fat free mass (FFM) and normal fat mass (NFM) as size descriptors of volumes and clearances using non-linear mixed effects modeling. NFM partitions total body weight into FFM and fat mass calculated from total body weight (TBW) minus FFM. The relative influence of fat mass compared to FFM is described by the fraction of fat mass that makes fat equivalent to FFM (Ffat). RESULTS: Theory-based allometric scaling using FFM best described weight and body composition differences in clearances and volumes A negative effect of fat mass of with an exponential parameter of -0.00541/kg (95 % CI -0.0118 to -0.00246) was estimated for clearance which indicates increased fat mass is associated with impairment of clearance. CONCLUSIONS: The use of theory-based allometry with predictions of fat free mass has been able to separate the influences of weight and body composition and indicates that size-normalized clearance of dexmedetomidine is impaired in patients who are obese.