Successful resuscitation of patients with shock often requires infusion of large volumes of crystalloid. Although “dilution acidosis” has been described in animal models1 and in human anecdotes, systematic examination of this phenomenon was only recently reported in children with shock.2 After receiving Institutional Review Board approval, we examined the medical records of adults admitted with a primary diagnosis of shock to Bridgeport Hospital during 19 months. Ninety-eight patients required > 1 L of normal saline (NS) administered in ≤ 1 h. Of these, 59 had sufficient data to enable computation of acid-base status, and 17 (28.8%) developed hyperchloremic metabolic acidosis (HMA) in the first 24 h. All arterial blood gases were analyzed for acid-base status by a blinded senior nephrology fellow using a nomogram-based, acid-base calculator (http://www.medcalc.com/acidbase.html). Anion gap (AG) acidosis was defined as metabolic acidosis with AG > 12 mEq/L after correction for serum albumin. When metabolic acidosis was present with AG ≤ 12 mEq/L, patients were categorized as having HMA. When AG was > 12 mEq/L, the “delta-delta” (ie, measured AG sufficient to explain the drop in bicarbonate from 24 mEq/L) was computed to ascertain whether HMA coexisted with the AG acidosis. There was no significant difference in the presence of chronic kidney disease or diabetes in patients with or without HMA. A total of 94.1% of patients had septic shock. Overall, the amount of NS administered in the 24 h ranged from 3 to 11.8 L for the HMA group compared with 0.3 to 17.2 L for the non-HMA group (median 6 vs 3 L, P = .002) (Table 1). Patients with HMA received fluids at a higher rate (276.2 vs 183.5 mL/h, P = .002). An infused volume of ≥ 4 L NS predicted HMA with a sensitivity of 82% and a specificity of 64%. In multiple logistic regression models, HMA at 24 h was highly associated with infused NS ≥ 4 L (OR, 13.9; 95% CI, 2.3-85.2). Age, diuretic use, chronic kidney disease, lactic acidosis, and bicarbonate infusion were not associated with HMA.