Arterial minus end-tidal CO₂ as a prognostic factor of hospital survival in patients resuscitated from cardiac arrest

Aims: The purpose of this study was to determine the clinical value of arterial minus end-tidal CO₂ [P(a-et)CO₂] and alveolar dead space ventilation ratio (V_dA/V_t) as indicators of hospital mortality in patients that have been resuscitated from cardiac arrest at emergency department. Materials and methods: Forty-four patients with a return of spontaneous circulation (ROSC) after cardiac arrest were studied in the emergency department of a university teaching hospital from March 2004 to February 2006. Mean arterial pressure (MAP), serum lactate, arterial blood gas studies, end-tidal CO₂ (EtCO₂), P(a-et)CO₂, and V_dA/V_t were evaluated at 1 h after ROSC. We compared these variables between hospital survivors and non-survivors. Results: The rates of ventricular fibrillation and pulseless ventricular tachycardia in hospital survivors were higher than those of non-survivors (53.0 and 9.7%, respectively, p = 0.002). Hospital survivors had significantly higher MAP, lower serum lactate, lower P(a-et)CO₂, and lower V_dA/V_t value than non-survivors. Receiver operator characteristic (ROC) curves of serum lactate, P(a-et)CO₂, and V_dA/V_t showed significant sensitivity and specificity for hospital mortality. Specifically, lactate ≥10.0 mmol/L, P(a-et)CO₂ ≥ 12.5 mmHg, and V_dA/V_t ≥ 0.348 were all associated with high hospital mortality (p = 0.000, 0.001 and 0.000, respectively). Conclusions: This study showed that high serum lactate, high P(a-et)CO₂ and high V_dA/V_t during early ROSC in cardiac arrest patients suggest high hospital mortality. If future studies validate this model, the P(a-et)CO₂ and V_dA/V_t may provide useful guidelines for the early post-resuscitation care of cardiac arrest patients in emergency departments.