Intramuscular adrenaline to improve outcomes following cardiac arrest – An experimental porcine study

To investigate early intramuscular adrenaline as an add-on treatment for cardiac arrest in a clinically relevant porcine model. We hypothesized that intramuscular adrenaline would improve return of spontaneous circulation (ROSC) compared to placebo. 36 pigs (38-42 kg) were subjected to hypoxia induced cardiac arrest for 3.5 minutes. During resuscitation, the pigs were randomized to either 0.125 mg/kg (0.125 ml/kg) intramuscular adrenaline or placebo 0.125 ml/kg normal saline. Both groups underwent basic life support followed by advanced life support including intravenous adrenaline 5 minutes after intramuscular adrenaline. Pigs achieving ROSC underwent one hour of intensive care. The primary outcome was ROSC. The ROSC rate was 4/18 (22%) in the placebo group and 4/18 (22%) in the intervention group (OR = 1.00 95%CI [0.15;6.55], p = 1.00). There was no difference in coronary perfusion pressure or cerebral oxygen tension (difference: 0.71 mmHg [95%CI: -7.25; 8.67], p = 0.86 difference: 3.0 mmHg [95%CI: -7.68; 13.69], p = 0.57). Adrenaline blood concentrations were significantly higher in the intervention group 30 minutes (difference: 9.44 nmol/L [95%CI: 3.42; 15.5] p =0.009) and 60 minutes after ROSC (difference: 15.9 nmol/L [95%CI: 8.51; 23.4] p =0.002). There was a significantly higher cardiac output in the intervention group 60 minutes after ROSC (difference: 2.58 L/min [95%CI: 0.78; 4.37] p = 0.013). Early intramuscular injection of adrenaline 5 minutes prior to intravenous adrenaline did not increase the ROSC rate but resulted in a prolonged absorption with higher adrenaline levels at 30 and 60 minutes after ROSC.