Effect of a single small volume fluid bolus with balanced or un-balanced fluids on chloride and acid–base status: a prospective randomized pilot study (the FLURES-trial)

Objective To compare the short-term effects on acid base, electrolyte status and urine output of a single fluid bolus of saline to that of the balanced solution Plasmalyte ® in critically ill patients. Methods Prospective, randomized, controlled trial. Adult patients (≥ 18 years) admitted to the ICU receiving a fluid bolus were randomized to receive 1 L of saline (NaCl 0.9%, Baxter) or a balanced fluid [Plasmalyte ® (Baxter)]. Blood samples and urine output were collected just before (T0), just after (T1), 2 h after (T2) (only for urinary output) and three hours after termination of the fluid bolus (T4). The effect of fluid boluses on serum chloride, apparent strong ion difference, base excess, urinary output and blood pressure or vasopressor need were analyzed. Main results Patients who received a 1 L saline fluid bolus had a significant increase in serum chloride (1.60; 95% CI 1.10 to 2.10; P