Table 1.
Baseline Characteristics of the Patients.*
| Characteristic | Balanced Crystalloids (N = 6708) | Saline (N = 6639) |
|---|---|---|
| Median age (IQR) — yr | 54 (37–67) | 53 (37–67) |
| Female sex — no. (%) | 3507 (52.3) | 3379 (50.9) |
| Race — no. (%)† | ||
| White | 5159 (76.9) | 5189 (78.2) |
| Black | 1335 (19.9) | 1251 (18.8) |
| Other | 214 (3.2) | 199 (3.0) |
| Median Elixhauser Comorbidity Index score (IQR)‡ | 7 (3–14) | 7 (3–14) |
| Admission service — no. (%) | ||
| Medicine services | ||
| General medicine | 4747 (70.8) | 4687 (70.6) |
| Cardiology | 303 (4.5) | 321 (4.8) |
| Neurology | 117 (1.7) | 144 (2.2) |
| Surgery services | ||
| General surgery | 1278 (19.1) | 1211 (18.2) |
| Trauma | 263 (3.9) | 276 (4.2) |
| Median baseline serum creatinine (IQR) — mg/dl | 0.84 (0.71–0.95) | 0.85 (0.71–0.94) |
| Source of baseline creatinine — no. (%) | ||
| Measured value in medical record | 4405 (65.7) | 4276 (64.4) |
| Calculated value by equation | 2303 (34.3) | 2363 (35.6) |
| Initial kidney function in ED | ||
| Serum creatinine | ||
| Mean — mg/dl | 1.32±1.42 | 1.31±1.36 |
| Median (IQR) — mg/dl | 0.93 (0.77–1.33) | 0.93 (0.77–1.32) |
| ≥1.5 mg/dl — no. (%) | 1246 (18.6) | 1240 (18.7) |
| End-stage renal disease with long-term renal-replacement therapy — no. (%) | 126 (1.9) | 109 (1.6) |
| Stage 2 or higher acute kidney injury — no./total no. (%)§ | 643/6582 (9.8) | 631/6530 (9.7) |
| Initial serum electrolytes in ED | ||
| Sodium — mmol/liter | 137.2±4.2 | 137.4±4.3 |
| Chloride — mmol/liter | 102.8±5.4 | 103.1±5.6 |
| Potassium — mmol/liter | 4.1±0.7 | 4.1±0.7 |
| Bicarbonate — mmol/liter | 22.7±3.8 | 22.8±3.7 |
| Blood urea nitrogen — mg/dl | 20±16 | 20±16 |
Plus–minus values are means ±SD. There were no significant differences in baseline characteristics between the two groups, except for initial serum sodium (P = 0.006) and chloride (P = 0.003). To convert the values for creatinine to micromoles per liter, multiply by 88.4. To convert the values for blood urea nitrogen to millimoles per liter, multiply by 0.357. ED denotes emergency department, and IQR interquartile range.
Race was reported by patients or their surrogates and recorded in the electronic health record as a part of routine clinical care.
The Elixhauser Comorbidity Index score summarizes the burden of a patient’s coexisting conditions. Scores range from −19 to 89, with higher scores indicating a profile of coexisting conditions that is more strongly associated with in-hospital death.24
Acute kidney injury was defined according to the Kidney Disease: Improving Global Outcomes creatinine criteria. Patients with end-stage renal disease who were receiving long-term renal-replacement therapy at the time of ED arrival were not eligible for the outcome of acute kidney injury.