Purpose of the study
Arterial carbon dioxide tension (pCO2) is a possible modifiable parameter that could contribute to survival after cardiac arrest. The purpose of our study was to determine pCO2 and pH in our patient population. 
Materials and methods
We performed a retrospective study in adult patients after non-asphyxial out-of-hospital or in-hospital cardiac arrest, who were admitted in 2015 and 2016. We collected data on the highest pCO2, the lowest pH and the highest lactate in the first 24 hours after admission. 
Results 
We included 153 patients. 109 (71.2%) were males, mean age was 64±13 years, and 62 (40.5%) patients survived to hospital discharge. We observed no significant differences in pCO2 between survivors and non-survivors (7.1±2.2 kPa vs. 7.3±2 kPa, p=0.62), and a significantly lower pH (7.2±0.1 vs. 7.1±0.1, p<0.0001) and higher lactate (4.9±3.1 mmol/l vs. 8.5±5.5 mmol/l, p<0.0001) in non-survivors. We observed hypocapnia (pCO2<4 kPa) in 1.6% of survivors and 1.1% of non-survivors, normocapnia (pCO2 4.5-6 kPa) in 19.4% vs. 14.3%, mild hypercapnia (pCO2 6.5-8 kPa) in 38.7% vs. 16.5% and severe hypercapnia (pCO2>8 kPa) in 19.4% vs. 25.3%. We observed a trend towards lower mortality in patients with mild hypercapnia (OR 0.3 [95% CI 0.13-0.67, p=0.003]). Severe acidosis (pH<7.1) and hyperlactatemia (lactate>4 mmol/l) were observed in 12.9% and 47.5%% of survivors, and 30.8% and 69% of non-survivors, and were associated with a trend towards greater mortality (OR 3.0 [95% CI 1.26-7.13, p=0.01], and OR 1.9 [95% CI 0.86-4.49, p=0.11], respectively).   
Conclusions
Derangements in arterial pCO2 and pH are common in survivors after cardiac arrest, however, it seems that metabolic acidosis associated with hyperlactatemia, and not elevated pCO2 contributed to mortality in our patient population.

2 - Association of arterial carbon dioxide and pH with hospital mortality after cardiac arrest