Findings on the portable chest radiograph correlate with fluid balance in critically ill patients

Abstract

Study objectives: Fluid balance concerns occur daily in critically ill patients, complicated by difficulties assessing intravascular volume. Chest radiographs (CXRs) quantify pulmonary edema in acute lung injury (ALI) and total blood volume in normal subjects. We hypothesized that CXRs would reflect temporal changes in fluid balance in critically ill patients.

Design: Standardized scoring of 133 supine, portable, anteroposterior CXRs. Outcomes included subjective and objective measures of intravascular volume and pulmonary edema.

Setting: Academic university medical center and affiliated Veterans Affairs hospital.

Patients: Thirty-seven patients with ALI receiving mechanical ventilation blindly randomized to treatment with diuretics and colloids or dual placebo for 5 days.

Measurements and results: Treated patients experienced a 3.3-L diuresis and 10-kg weight loss during the 5-day period. A significant correlation was observed in all patients between changes in vascular pedicle width (VPW) and net intake/output (r = 0.50, p = 0.01) or weight (r = 0.51, p = 0.01). The correlation between VPW and fluid balance was greatest for weight changes in the treatment group alone (r = 0.71, p = 0.005). Pulmonary artery occlusion pressure correlated highly with changes in VPW (r = 0.70, p < 0.001). After day 1, CXRs revealed significant between-group differences in VPW without changes in cardiothoracic ratio or subjective measures of edema. The proportion of patients with VPW < 70 mm did not differ at baseline but was significantly more in the treatment group on all subsequent days (p < 0.05).

Conclusions: We conclude that temporal fluid balance changes are reflected on commonly utilized portable CXRs. Objective radiographic measures of intravascular volume may be more appropriate indicators of fluid balance than subjective measures, with VPW appearing most sensitive. If systematically quantitated, serial CXRs provide a substantial supplement to other clinically available data for the purpose of fluid management in critically ill patients.