Targeted mild hypercapnia after out-of-hospital cardiac arrest is associated with favourable cardiovascular effects. A sub-study of the TAME cardiac arrest trial.

Abstract

Purpose: Hypercapnic acidosis may elicit detrimental haemodynamic effects in critically ill patients. We aimed to investigate the consequences of targeted mild hypercapnia (TMH) versus targeted normocapnia (TN) on pulmonary vascular resistance and right ventricular function in patients resuscitated from out-of-hospital cardiac arrest (OHCA). Methods: Single-centre, prospective, sub-study of the Targeted Therapeutic Mild Hypercapnia After Resuscitated Cardiac Arrest (TAME) trial. Patients were randomised to TMH (PaCO2 = 6.7–7.3 kPa) or TN (PaCO2 = 4.7-6.0 kPa) for 24 hours. Haemodynamic assessment was performed with right heart catheterisation and serial blood-gas analyses every 4th hour for 48 hours. Results: We studied 84 patients. Mean pH was 7.24 (95 % CI 7.22–7.30) and 7.32 (95 % CI 7.31–7.34) with TMH and TN, respectively (P-group < 0.001). Pulmonary vascular resistance index (PVRI), pulmonary artery pulsatility index, and right atrial pressure did not differ between groups (P-group > 0.05). Mean cardiac index was higher with TMH (P-group < 0.001): 2.0 (95 % CI 1.85–2.1) vs 1.6 (95 % CI 1.52–1.76) L/min/m2. Systemic vascular resistance index was 2579 dyne-sec/cm-5/ m2 (95 % CI 2356–2830) with TMH, and 3249 dyne-sec/cm-5/ m2 (95 % CI 2930 – 3368) with TN (P-group < 0.001). Stroke volumes (P-group = 0.013) and mixed venous oxygen saturation (P-group < 0.001) were higher in the TMH-group. Conclusion: In resuscitated OHCA patients, targeting mild hypercapnia did not increase PVRI or worsen right ventricular function compared to TN. TMH comparatively improved cardiac performance and mixed venous oxygen saturation. Trial registration number: NCT03114033