Volume of intraoperative normal saline versus lactated Ringer's solution on acute kidney injury: A secondary analysis of the SOLAR trial.

Unlabelled: Postoperative acute kidney injury (AKI) is common after non-cardiac surgery. Normal saline and lactated Ringer's solution are both used for volume replacement during surgery. Normal saline decreases renal blood flow and causes hyperchloremic acidosis whereas lactated Ringer's does not. The incidence of AKI is similar with modest volumes of each fluid. But it remains unclear whether larger volumes of normal saline provoke AKI.

Objective: Evaluate whether intraoperative crystalloid volume modifies the relationship between the AKI risk and treatment group.

Design: Secondary analysis of a single-center multiple cross-over cluster trial.

Setting: Intraoperative care.

Patients: We enrolled 8616 adults who had colorectal or orthopedic surgery at a large academic institution.

Interventions: Clusters of patients were alternately assigned to intraoperative normal saline or lactated Ringer's solution.

Measurements: The primary outcome was the incidence of acute kidney injury (AKI) as a function of intraoperative crystalloid volume (0-1, 1-2, 3-4, or 4+ liters) and the type of crystalloid. Our secondary outcome was the change in postoperative serum chloride concentration during the first 24 h.

Main Results: The risk of AKI did not differ significantly in patients given 0-1, 1-2, or 3-4 L saline or lactated Ringers solutions. In contrast, patients given 2-3 or > 4 L of lactated Ringer's solution had a higher risk of AKI than those given saline. Patients assigned to normal saline had progressively greater plasma chloride concentrations than those given lactated Ringer's across all volume categories.

Conclusions: While saline administration clearly causes volume-dependent hyperchloremia, we found no evidence to support the theory that large volumes of saline provoke AKI. Therefore, either fluid seems reasonable for intraoperative use.