The main purpose of this study is to compare blood loss at the time of laparoscopic or robotically-assisted laparoscopic myomectomy when using different amounts of dilute vasopressin solution. Myomectomy is a surgical procedure to remove fibroids from the uterus. Vasopressin is a synthetic drug used to help decrease blood loss at the time of gynecologic surgery; although very little is know about the optimal dosage and administration.

The investigators plan to perform a randomized clinical trial on patients scheduled for minimally invasive myomectomy. All patients will get the same overall amount of vasopressin. Patients will be assigned by chance to one of two groups: one group will receive higher volume of a more dilute vasopressin solution. The other group will receive a lower volume of a more concentrated solution. The investigators will collect information on operative blood loss and complications related to surgery.

All surgeons who enroll patients into our study are experienced laparoscopic surgeons who have performed at least 100 advanced laparoscopic procedures including hysterectomies and myomectomies. Briefly, our laparoscopic myomectomy technique is as follows: After gaining peritoneal access and placing visual and operative trocars, the surgical site is inspected carefully and fibroid locations identified. After informing the anesthesia team that vasopressin (from pharmaceutical company American Regent 20 units/ml) is about to be injected, the uterus is infiltrated with vasopressin.

Patients will be randomized one of two treatment groups pre-operatively on the day of surgery:

1. One arm will receive injection of 200 ml total of the 0.05 units/ml dilute vasopressin solution (total 10 units Vasopressin used, dilution of 20 units vasopressin in 400 ml of normal saline).
2. The second arm will receive injection of 30 ml total of the 0.3 units/ml dilute vasopressin solution (total 10 units Vasopressin used, dilution of 20 units Vasopressin in 60 mL of Normal Saline).

The procedure is done according to surgeon preference using various energy modalities such as monopolar or Harmonic Scalpel® (Ethicon Endo-Surgery, Cincinnati OH), for making the incision in the uterus. The fibroid is then removed from the uterus and examined. The incision is then closed in several layers with laparoscopic standard suturing technique, and hysterotomy site is generally covered with an adhesion barrier (Gynecare Interceed® (Ethicon Women's Health and Urology, Somerville NJ) or Seprafilm® slurry (Genzyme Biosurgery, Framingham MA)).

Blood Samples:

As per routine, preoperative blood samples to assess hematocrit levels will be taken no greater than 2 weeks prior to surgical date; if no preoperative laboratory studies have been obtained a sample will be drawn on the day of surgery. Postoperative blood samples to assess hematocrit will be taken no sooner than 4 hours after surgery for patients who are discharged the same day; for patients who are monitored overnight in hospital, the lab will be drawn on postoperative day #1.

Follow-up:

Patients will be followed for 8 weeks after surgery to assess for occurrence of any postoperative complication. A member of the team (health care worker such as research assistant who has been trained in HIPPA procedures) will be in charge of abstracting data from the medical records and entering this information into a study database.

Inclusion Criteria:

• The inclusion criteria for our study include all women who are candidates for a laparoscopic or robotic-assisted laparoscopic myomectomy and are willing to accept randomization.
• The exclusion criteria: for our study include: suspected malignancy or contraindication to morcellation of uterine tissue, history of adverse reaction or allergy to vasopressin, and active cardiovascular or pulmonary disease that would indicate a contradiction to use of vasopressin.

Adverse events data was collected for a period of 4 years, from the start of the study (July 2011), to completion of the study (June 2015). The time frame for reporting adverse events will be within 7 calendar days of the adverse event. Patients were assessed from the time of their initial consult to 8 weeks following surgery.

If an adverse event occurs to any patients enrolled in this study, the primary investigator will conduct an investigation to determine if the event was related to the study protocol (ie: administration of vasopressin). If the event is clearly linked, or insufficient data exists to determine relationship of event to study protocol, then the investigator will report the event to the IRB. Any protocol-related complication will be communicated to investigators at other sites as well.

Due to practice pattern differences among sites, there was some missing data for the change in hematocrit variable, and a smaller amount of data missing for suction canister blood loss calculation.