Bioelectrical impedance analysis as a predictor for survival in patients with systemic inflammatory response syndrome

Objectives

Noninvasive bioelectrical impedance analysis (BIA) measures resistance, reactance and the derived phase angle (phi, degrees). A low phase angle has been associated with an altered cellular membrane function [1]. In septic shock patients, a phase angle of less than 4° has been reported to be associated with increased mortality [2]. Furthermore a low phase angle was highly correlated with mortality in patients with AIDS [3] and burns [4]. In our study we examined the prognostic value of the phase angle using BIA in patients with systemic inflammatory response syndrome (SIRS).

Design

Prospective clinical observational study.

Measurements

Thirty consecutive patients (11 female, 19 male, median age of 67 [16.5] years) were included after admission to the intensive care unit, all of whom met two or more SIRS criteria. SIRS was defined using the criteria suggested by ACCP/SCCM guidelines. Severity of illness was characterised according to the Acute Physiology and Chronic Health Evaluation (APACHE) II. Noninvasive impedance analysis was performed using a tetra polar hand-to-foot BIA measuring device (BIA 2000, Data input) as resistance (Ohms) and reactance (Ohms). The derived phase angle was calculated as arc tan(reactance/resistance). Two diagnostic electrodes were attached to the hand and two diagnostic electrodes were attached to the ipsilateral foot. All measurements were performed in supine position of the patient with special care taken that arms and legs did not touch the rest of the body or any grounding object. The joints were semiflexed. Data are presented as median and interquartile range (IQR). Fisher's exact test was performed to compare a phase angle of more than 4° at inclusion day with the 28 day mortality and APACHE II scores between survivors and nonsurvivors. P < 0.05 was considered significant.

Results

After 28 days, out of the 30 patients investigated 10 had died and 20 were survivors. The APACHE II score on inclusion day of the survivors was 11 (7.0) compared with 16 (6.8) in nonsur-vivors (P = 0.87). In seven out of the 20 survivors a phase angle of more than 4° was measured on the first study day, whereas in all patients who died the phase angle was smaller than 4° (P = 0.038).

Conclusion

These results demonstrate that, in patients developing SIRS, an initial phase angle of more than 4° may be significantly correlated with survival.