Isotonic saline causes greater volume overload than electrolyte-free irrigating fluids.

Objectives: Systemic absorption of the irrigating fluid used to flush the operating site is a potentially serious complication in several types of endoscopic operations. To increase safety, many surgeons have changed from a monopolar to a bipolar resection technique because 0.9% saline can then be used instead of electrolyte-free fluid for irrigation. The present study examines whether the tendency for excessive plasma volume expansion is greater with saline than with electrolyte-free fluid.

Methods: Pooled data were analyzed from four studies in which a mean of 1.25 L of either 0.9% saline or an electrolyte-free irrigating fluid containing glycine, mannitol, and sorbitol was given by intravenous infusion on 80 occasions to male volunteers and patients scheduled for transurethral prostatic surgery. The distribution of the infused fluid was analyzed with a population volume kinetic model based on frequently measured hemodilution and the urinary excretion.

Results: Electrolyte-free fluid distributed almost twice as fast and was excreted four times faster than 0.9% saline. The distribution half-life was 6.5 and 10.6 min for the electrolyte-free fluid and saline, respectively, and the elimination half-lives (by urinary excretion) from the plasma volume were 21 and 87 min. Simulation showed that the plasma volume expansion was twice as great from 0.9% saline than from electrolyte-free fluid.

Conclusions: Isotonic (0.9%) saline expands the plasma volume by twice as much as occurs with electrolyte-free irrigating fluids. This difference might explain why signs of cardiovascular overload are the most commonly observed adverse effects when saline is absorbed during endoscopic surgery.