Inspiratory-cycle instillation of endotracheal epinephrine in porcine arrest.

Objective: To compare timed inspiratory-cycle endotracheal (ET) instillation of epinephrine (EPI) with instillation during apnea during CPR.

Methods: Prospective randomized laboratory comparison of two ET-EPI instillation techniques in 24 preadolescent anesthetized and paralyzed Yucatan swine (mean weight 10.3 +/- 1.5 kg) with apnea-induced hypoxic and hypercarbic cardiopulmonary arrest. After 8 minutes of cardiopulmonary arrest and 1 minute of CPR, 500 microgram(s) (50 +/- 7 microgram(s)/kg) of radiolabeled ET EPI was either administered timed to a ventilator inpspiratory cycle (IN, n = 15) or injected during apnea (DA, n = 9) using a monitoring lumen built into the sidewall of the ET tube. Injection technique was carefully controlled regarding ET-tube position, dilution, flush, and pressure-limited mechanical ventilations. CPR was resumed and continued for 5 minutes. If resuscitation occurred, monitoring was continued for one hour. Outcome variables included pulmonary EPI distribution pattern (DIST), plasma exogenous and total EPI levels, successful resuscitation, and hemodynamic response.

Results: Bilateral DIST occurred in 58% of the pigs, with significantly more bilateral DISTs for IN versus DA pigs (p = 0.01). Plasma radiolabeled exogenous EPI counts were significantly greater for IN versus DA pigs (p = 0.03). Total plasma EPI levels rose significantly above baseline over time within each group, but showed no difference between the IN and DA groups at any time point. Successful resuscitation occurred in 21% of the pigs, with no difference between IN and DA pigs (p = 0.38).

Conclusion: When other aspects of ET EPI instillation are optimized and controlled during porcine hypoxic-hypercarbic arrest, timed inspiratory-cycle installation of ET EPI (50 microgram(s)/kg) results in an improved bilateral DIST and greater exogenous EPI absorption. However, in this severe pediatric asphyxial arrest model using a 50-microgram(s)/kg dose, inspiratory-cycle instillation does not improve the resuscitation rate or hemodynamic response over currently recommended instillation during apnea.