Effect of intravenous lactated Ringer's solution infusion on the circulating lactate concentration

Objectives We prevlously discovered that small amounts of lactated Ringer's solution, which are inadequately cleared from an intravenous catheter, falsely increase the circulating lactate concentration in blood samples collected from that catheter. That finding prompted us to test the hypothesis that intravenous lactated Ringer's solution, infused at a rate used in resuscltation, would increase the circulating lactate concentration. Design A prospective, randomized, double-blinded, placebocontrolled study. Setting A critical care research laboratory. Subjects Twenty-four normal, healthy, adult volunteer subjects. Interventions Two intravenous catheters were placed. One was used for the infusion of the test solution and the other catheter was used for blood sampling. Blood samples were serially collected for the determination of blood lactate concentrations. Measurements and Main Results Twenty-four healthy adult volunteers were randomized to receive a 1-hr infusion of either lactated Ringer's solution (n = 6), 0.9% saline (n = 6), 5% dextrose in lactated Ringer's solution (D5 RL) (n = 6), or 5% dextrose in water (D5 W) (n = 6). Each subject received nothing by mouth after midnight. At 0800 hrs, catheters were inserted and each subject received 1 L of the assigned solution over 1 hr. Throughout the study, the subjects were at rest. Three-millillter samples of venous blood were collected before, during (at 15, 30, 45, and 60 mins), and after (at 90, 120, and 240 mins) the infusion. Blood samples were placed on ice immediately after collection and analyzed within 5 mins of collection. Lactate concentrations were determined using an ion-selective, amperometric electrode, which we have previously validated. Lactate concentrations were compared between subjects receiving lactated Ringer's solution vs. subjects receiving normal saline. A similar comparison was made between subjects receiving D5 RL vs. D5 W at similar time points during the study. There were no clinically or statistically significant differences in lactate values at the time points studied in those subjects receiving lactated Ringer's solution vs. Those persons receiving normal saline (p > .05; n = 12; Student-Newman-Keuls' multiple comparison test) or those subjects receiving D5 W vs. those subjects infused with D5 RL (p >.05; n = 12; Student-Newman-Keuls' multiple comparison test). In no case did the circulating lactate values exceed 2 mmol/L (the upper limit of normal). Conclusions The short-term infusion of lactated Ringer's solution in normal adults (hemodynamically stable) does not falsely increase circulating lactate concentrations when 1 L is given over 1 hr. Therefore, clinicians should not disregard increased lactate concentrations in patients receiving a rapid infusion of lactated Ringer's solution. (Crit Care Med 1997; 25:1851-1854)