Supraphysiological concentrations of sodium and chloride are present in routinely used intravenous fluids. It is widely understood that the use of 0.9% saline and other chloride-rich solutions in critically ill patients causes metabolic acidosis, decreases the strong ion difference, and may lead to worse outcomes. In this month’s issue of Critical Care Medicine, Nor’azim Yunos and colleagues from Melbourne, Australia, conducted a prospective, open-label, before-and-after study to investigate the biochemical effects when chloride-rich solutions such as 0.9% saline, Gelofusine, or Albumex 4 are restricted.
The study was conducted in a multidisciplinary ICU, and 1,644 patients admitted over the course of 15 months were included. After a 3-month washout period, ICU staff were not allowed to use 0.9% saline; only Hartmann’s solution, Plasma-Lyte 148, or Albumex 20 were administered (intervention group).
Significant reductions in the use of chloride-rich solutions were found after the washout period. The incidence of severe hyperchloremia (2.3% vs. 6.2%, p<0.001) and hypernatremia (0.2% vs. 0.9%, p<0.001) were significantly lower in the intervention group; however, a significantly greater incidence of metabolic alkalosis and alkalemia was found in the intervention group (14.7% vs. 10.5%, p<0.001). Fluid costs decreased from $15,077 to $3,915. The time-weighted standard base excess increased from 0.5 (+/- 4.5) to 1.8 (+/- 4.7) in the intervention group. The authors concluded that restriction of chloride-rich solutions was associated with a significant decease in the incidence of metabolic acidosis, hypernatremia, and severe hyperchloremia; however, the incidence of metabolic alkalosis was increased.
There are a few limitations worth noting. Not all solutions used in this study are available in the U.S. For example, a gelatin colloid, Gelofusine was used in the control group, and this colloid is not widely used in North America (although it is similar to other colloidal preparations). No exclusion criteria were applied, thus possibly improving the external validity of the study, but the biochemical effects of chloride restriction may not be the same for all patients. The implications for the biochemical changes in this study remain unknown. It is not clear if metabolic alkalosis, versus metabolic acidosis, leads to worse outcomes in the critically ill, and the authors plan to undertake future studies to help answer this question.
Concise Critical Appraisal is a regular feature authored by SCCM member Samuel M. Galvagno Jr., DO. Each installment highlights journal articles most relevant to the critical care practitioner.