Dilute versus concentrated vasopressin administration during laparoscopic myomectomy: a randomised controlled trial

Objective: To determine if higher-volume, fixed-dose administration of vasopressin further reduces blood loss at the time of minimally invasive myomectomy. Design: Randomised multicentre clinical trial. Setting: Tertiary-care academic centres in the USA. Population: Women undergoing conventional laparoscopic or robot-assisted laparoscopic myomectomy. Methods: All participants received the same 10-unit (U) dose of vasopressin, but were randomly assigned to one of two groups: (i) received 200 ml of diluted vasopressin solution (20 U in 400 ml normal saline), and (ii) received 30 ml of concentrated vasopressin solution (20 U in 60 ml normal saline). Main outcome measures: The primary study outcome was estimated blood loss; the study was powered to detect a 100-ml difference. Results: A total of 152 women were randomised; 76 patients in each group. Baseline demographics were similar between groups. The primary outcome of intraoperative blood loss was not significantly different, as measured by three parameters: surgeon estimate (mean estimated blood loss 178 ± 265 ml and 198 ± 232 ml, dilute and concentrated groups respectively, P = 0.65), suction canister-calculated blood loss, or change in haematocrit levels. There were no vasopressin-related adverse events. Conclusion: Both dilute and concentrated vasopressin solutions that use the same drug dosing demonstrate comparable safety and tolerability when administered for minimally invasive myomectomy; however, higher volume administration of vasopressin does not reduce blood loss. Tweetable abstract: This randomised trial failed to show benefit of high-volume dilute vasopression.