Ringer's lactate solution remains in the peritoneal cavity after laparoscopy longer than expected

To evaluate by serial ultrasound scans how long a Ringer's lactate instillation remains in the peritoneal cavity after laparoscopy. Prospective, randomized, double blind, clinical trial. Tertiary care, university hospital. Thirty-six patients undergoing diagnostic or minor operative laparoscopy. At the end of laparoscopy, the patients were tilted to an anti-Trendelenburg position and all fluid was aspirated. The patients were then randomized to receive an instillation of 300 mL of Ringer's lactate or no fluid instillation. Serial transvaginal ultrasound scans were performed at the end of surgery and at 24, 48, and 96 hours after the surgery. Through direct measurements of scalar fluid volumes instilled in the operating room and real-time ultrasound comparisons, an empiric formula was calculated to correlate actual intraperitoneal volumes to ultrasonically derived measurements of fluid pockets. With this formula, the volume of intraperitoneal fluid at 24, 48, and 96 hours after surgery was calculated. Twenty-four hours after surgery, a mean volume of 184 mL was present in the Ringer's lactate group versus 46 mL in the control group. At 48 hours after surgery, the mean volumes were 78 mL versus 30 mL, respectively. No statistically significant differences were found after 96 hours. Peritoneal absorption of instilled crystalloids is traditionally reported to be 30 to 60 mL/hour. We report detecting statistically significant amounts of fluid at 24 and 48 hours after surgery, after infusion of 300 mL of Ringer's lactate. This suggests that fluid remains in the peritoneal cavity longer than traditionally believed.