Abstract 197: Initial Base Deficit and Arterial Carbon Dioxide Level Associated with Survival in Postarrest Patients

Abstract

Introduction: Serial arterial blood gases (ABG) are typically monitored in post-arrest patients treated with therapeutic hypothermia (TH). The relationship between arterial carbon dioxide (PaCO 2 ) levels, degree of base deficit (BD), neurologic outcome, and survival is unclear. Hypothesis: Lower PaCO 2 , as a surrogate for hyperventilation, and larger BD, correlating with ongoing acidosis, may be associated with decreased survival and worse neurologic outcomes in post-arrest TH patients. Methods: We conducted a retrospective chart review of post-arrest patients treated with TH from the PATH database representing 11 institutions. Demographic variables were analyzed using chi-square tests. Unadjusted logistic regression analyses were performed to assess the relationship between hypocapnea (PaCO 2 < 30 mmHg), normocapnea (PaCO 2 30-45 mmHg), hypercapnea (PaCO 2 > 45 mmHg), mean BD, with respect to mortality or neurologic outcome at 1 st post-arrest ABG and at 6 hrs, 12 hrs, and 24 hrs post-arrest. Results: A total of 179 patients were enrolled. Patients were 59.6 ± 16.4 years, 54% male, and VF/VT was present in 31% of patients. Sixty-six (37%) survived to discharge, of which 76% (50/66) had a good neurologic outcome (CPC 1 or 2). Survivors had a lower mean initial PCO 2 value than non-survivors (49.0 vs. 57.5 mmHg; p=0.03); survival was significantly higher in patients who had normocapnea (51%) on their initial ABG when compared to those who were hypocapneic (25%) or hypercapneic (28%) (p=0.007), however, there was no significant difference in survival at the other time points. When adjusting for gender and initial rhythm, hypocapnea and hypercapnea had lower odds for survival in comparison to normocapnea (OR 0.23, 95% CI 0.03-2.01, p=0.18 and OR 0.72, 95% CI 0.35-1.5, p=0.38). Survivors had less severe BD than non-survivors at initial ABG (-8.0 vs. -11.3; p=0.005) and at all subsequent time points. There was no difference between PCO 2 or BD values between patients with good vs. bad neurologic outcomes. Conclusions: Patients who were normocapneic on initial ABG had improved survival. Survivors had lower initial PaCO 2 levels and less severe BD than non-survivors. There was no difference in PaCO 2 or BD values in patients with good vs. poor neurologic outcomes.