Administration of sodium bicarbonate during cardiopulmonary resuscitation increases the frequency of cardiac gas on postmortem CT estimated to be CO2

•Hypercapnia increases the frequency of cardiac gas (CG) on postmortem CT (PMCT).•CG on PMCT was frequently found in the sodium bicarbonate (SB) administration group.•Administraton of SB may generate extra carbon dioxide during resuscitation. Cardiac gas (CG) on immediate postmortem computed tomography (PMCT) after cardiopulmonary resuscitation (CPR) is associated with high blood carbon dioxide (CO2 ) levels. This study investigated whether administration of sodium bicarbonate (SB) during CPR generates extra blood CO2 , judging from CG findings on immediate PMCT. We enrolled 210 nontraumatic cardiopulmonary arrest (CPA) patients (101 men, 109 women) who were transported to our hospital and could not be resuscitated. They underwent arterial blood gas analysis (BGA) during CPR and immediate PMCT after failed resuscitation and were assigned to a CG-negative or a CG-positive group based on the PMCT findings. CG on immediate PMCT was detected in 106 patients (50.4%). Significant differences were not observed in the demographic variables between the CG-negative and CGpositive groups. Both pH and the partial pressure of arterial oxygen were significantly lower in the CG-positive group than in the CG-negative group, and the partial pressure of arterial carbon dioxide was significantly higher in the CG-positive group than in the CG-negative group. Among the administered infusions and medications, only SB demonstrated a significant difference in the frequency of administration between the CG-negative and CG-positive groups. The positive CG rate in the SB group (44/67, 66%) was significantly higher than that in the non-SB group (62/143, 43%). The administration of SB during CPR was associated with an increased frequency of CG on immediate PMCT, suggesting that administration of SB during CPR generates extra blood CO2.