Distribution of normal saline and 5% albumin infusions in cardiac surgical patients

Objective: To determine the relative distribution of fluid within the extracellular fluid volume (ECFV) and the effect on oxygen delivery after infusing either normal saline or 5% albumin in cardiac surgical patients. Design: Prospective, randomized, unblinded, interventional study. Setting: Cardiac surgical intensive care unit in a 450-bed teaching hospital. Patients: Postoperative cardiac surgical patients (n = 40). Interventions: Infusion of either normal saline or 5% albumin to a hemodynamic end point determined by the patient's clinician. Measurements and Main Results: Plasma volume (PV), ECFV, cardiac index, and arterial oxygen content were measured immediately before (baseline) and after each fluid infusion. PV and ECFV were measured by dilution of ¹³¹l-albumin and [³⁵S]sodium sulfate, respectively. Interstitial fluid volume (ISFV) was calculated as ECFV - PV. Baseline values for PV, ISFV, ECFV, and oxygen delivery index did not differ between treatment groups. Infusion of normal saline and 5% albumin increased PV by 9 ± 23% and 52 ± 84% of the volume infused, respectively (p < .05), whereas there was no significant difference between saline and albumin in the change in ISFV per volume infused. Only 5% albumin significantly increased cardiac index, although oxygen delivery did not change significantly after either infusion. Conclusions: In postoperative cardiac surgical patients, infusion of 5% albumin is approximately five times as efficient as a PV expander but has comparable effects on changes in ISFV and oxygen delivery relative to normal saline.