The effect of different chloride concentrations in intravenous fluids on patient outcomes

Objective

A controversial, but poorly studied aspect of fluid resuscitation is whether the chloride (Cl) concentration of the fluid is important. We performed a systematic review of the literature to determine the effect of different Cl concentrations in intravenous (IV) fluids on the outcome of critically ill patients.

Data sources

Studies were identified by MEDLINE search combining the medical subject heading 'Fluid Therapy' with the index terms: saline, lactate, Ringer's, and Hartmann's. Bibliographies were hand-searched for additional references.

Study selection

We selected studies based on the following inclusion criteria: randomized, controlled trials comparing IV fluids of different Cl concentration in patients requiring volume resuscitation. We classified the fluids as 'standard Cl' (154 mEq/l) or 'low Cl' (< 154 mEq/l). Studies comparing: fluids of different tonicities; crystalloids with colloids; or IV with oral therapy were excluded.

Data extraction

We extracted quantitative information regarding the type of crystalloid used, mortality, hemodynamic changes, acid-base balance, coagulation, and any other studied endpoint.

Results

Of 451 articles identified, seven met inclusion criteria (489 patients, 24–230 patients/study). Five compared normal saline (NS) (Na 154 mEq/l, Cl 154 mEq/l) with lactated Ringer's (Na 131 mEq/l, Cl 111 mEq/l), one compared NS with Plasmalyte 148 (Na 140 mEq/l, Cl 98 mEq/l), and one compared Hespan (Na 154 mEq/l, Cl 154 mEq/l) with Hextend (Na 143 mEq/l, Cl 124 mEq/l). In the four studies that reported mortality, only three deaths occurred. Two studies evaluated hemodynamics (changes in pulse pressure, pulse rate, duration of shock) and found no difference between crystalloids. All five studies that evaluated metabolic changes found statistically significant increases in serum Cl, decreases in pH, and larger base deficits with standard Cl versus low Cl solutions.

Conclusions

Limited data from randomized clinical trials consistently suggest that resuscitation with standard concentrations of chloride results in metabolic acidosis, but there is insufficient evidence to draw conclusions about the effect on mortality.