Dilute Versus Concentrated Vasopressin Administration During Laparoscopic Myomectomy: A Randomized Controlled Trial

Leiomyomata are found in up to 80% of uteri examined at hysterectomy; symptoms are present in 20% to 50% of women. The preferred surgical procedure when uterine conservation is desired is myomectomy; when feasible, the laparoscopic approach is preferred. The major morbidity associated with myomectomy is intraoperative bleeding, which can be treated pharmacologically to minimize blood loss. Vasopressin, a synthetic analog of the posterior pituitary hormone antidiuretic hormone, is often injected into the uterus to reduce blood loss during surgery. This agent has vasoconstrictive effects within the uterus and also stimulates uterine contraction. In a number of placebo-controlled studies, vasopressin was shown to decrease blood loss, blood transfusion, and operative time during myomectomy. Moderate-quality evidence was found in a 2014 Cochrane review that support use of vasopressin at time of myomectomy to decrease blood loss. Because relatively few studies have examined the clinical pharmacokinetics of vasopressin, little is known about optimal dosing and concentration. There are also few data on administration technique or effectiveness of this agent compared with other interventions. It has been postulated that a higher-volume, fixed-dose administration of vasopressin could further reduce blood loss at the time of laparoscopic myomectomy. The aim of this multicenter randomized trial was to compare use of a dilute versus a concentrated vasopressin solution on blood loss at time of minimally invasive myomectomy. The trial was conducted between 2011 and 2015 at 4 tertiary care academic centers in the United States. All participants were planning to undergo either conventional laparoscopic or robotassisted laparoscopic myomectomy. All participants were randomly assigned to 1 of 2 groups receiving a 10-unit (U) dose of vasopressin: the first group received 200 mL of diluted vasopressin solution (20 U in 400 mL normal saline), and the second received 30 mL of concentrated vasopressin solution (20 U in 60 mL normal saline). Patients but not operative staff were blinded to their group assignment. Estimated blood loss as reported by the operating surgeon was the primary study outcome measure. Other outcome measures were suction canister-calculated blood loss, or change in hematocrit levels. Each group comprised 76 patients. There were no differences between groups in baseline characteristics (age, race, body mass index, parity, or surgical history). No significant difference was found between groups in either the amount of blood loss as measured by surgeon-estimated blood loss (mean blood loss 178 +/- 265 and 198 +/- 232 mL, P = 0.65 in dilute and concentrated groups, respectively), suction canister-calculated blood loss, or change in hematocrit levels. No vasopressin-related adverse events occurred. These findings show that both dilute and concentrated solutions of vasopressin appear effective and well-tolerated for both conventional and robotic laparoscopic myomectomy when the same dosing is used. These data fail to confirm a proposed compressive benefit of dilute high-volume vasopressin solution on myomectomy-associated intraoperative-blood loss with laparoscopic surgery.