ICU predictors of morbidity after major trauma

Introduction

ICU injured patients often experience a condition of tissue hypoperfusion due to low cardiac output and oxygen delivery (DO₂). The imbalance between oxygen demand and DO₂ could be responsible for an anaerobic metabolism that is correlated with poor outcome. Several authors demonstrated that traditional (that is, serum lactate, base deficit) and oxygen-derived and carbon dioxide-derived parameters of anaerobiosis are helpful indicators of bad outcome in trauma patients. We aimed to identify predictors of morbidity in our ICU trauma patients.

Methods

Data for 175 adult trauma patients (age mean 50 ± 18.5 years) admitted to our ICU were prospectively collected from May 2006 and April 2007. Seventy hemodynamic, ventilatory, and metabolic parameters were evaluated within 3 hours after ICU admission. Accordingly to the GIVITI (Italian Group for the Evaluation of Interventions in ICU) database definitions, complications were defined as one or more organ dysfunctions or failures occurring during the ICU stay. Multivariate and receiver operating characteristic (ROC) curve analyses were applied.

Results

Morbidity was 40.5%. The Simplified Acute Physiology Score II, a high CO₂ production (VCO₂), and a low DO₂/VCO₂ ratio were significant in the multivariate analysis (Table 1). The DO₂/VCO₂ ratio was the best predictor of morbidity. Its cutoff value for morbidity was 3, and its area under the ROC curve was 0.87 (sensitivity 82%, specificity 75%). The ICU stay was longer for complicated patients (4.4 vs 14.5 days, P < 0.001), and mortality was higher (9% vs 22%, P < 0.001).

Table 1 Multivariate analysis results

Conclusion

This study demonstrated that the DO₂/VCO₂ ratio correlated well with morbidity. This ratio represents the imbalance between oxygen demand and delivery. The ratio might be continuously monitored in critically ill patients to assess an anaerobiosis state. This ratio together with the SAPS II ratio could predict complications in trauma patients.