Physiologic effects of intravenous fluid administration in healthy volunteers

Dose regimens in perioperative fluid management are rarely evidence based. Therefore, we investigated responses to an IV fluid infusion in healthy volunteers to assess basic physiologic effects of a fluid infusion per se. In a prospective, double-blinded, cross-randomized study, 12 healthy volunteers with a median age of 63 yr (range, 59 - 67 yr) received an infusion of lactated Ringer's solution 40 mL/kg (median, 2820 mL) or 5 mL/kg (median, 353 mL; background infusion) in random order on two separate occasions. The study was designed to mimic the perioperative course with preoperative fasting, infusion of the fluid over 3 h in the morning, and additionally 24-h hospitalization under standardized conditions. Primary outcome assessments were pulmonary function (spirometry), exercise capacity (submaximal treadmill test), balance function (Balance-Master(R)), and weight. Infusion of 40 mL/kg of lactated Ringer's solution compared with the background infusion (5 mL/kg) resulted in a significant decrease in pulmonary function and a significant weight gain of median 0.85 kg (range, -0.2-1.6 kg; P = 0.003) persisting 24 h after the infusion. Exercise capacity and balance function were not influenced by fluid administration. These findings may serve as a basis for clinical studies applying the same type of fluid in different amounts to determine the optimal amount of perioperative fluid in various surgical procedures.