Effect of epinephrine on cerebral and myocardial perfusion in an infant animal preparation of cardiopulmonary resuscitation

We assessed the efficacy of conventional cardiopulmonary resuscitation (CPR) in 2-week-old piglets. We determined intrathoracic vascular pressures, cerebral (CBF) and myocardial blood flows (MBF), and cerebral oxygen uptake during conventional CPR in this infant animal preparation and contrasted the results with those of previous work on adult animals. We further examined the effects of the infusion of epinephrine on these pressures and flows and on cerebral oxygen uptake, which has not been previously evaluated in adult preparations. Conventional CPR was performed on pentobarbital-anesthetized piglets with a 20% sternal displacement with the use of a pneumatic piston compressor. Chest ricoil was incomplete, leading to an 18% to 27% reduction in anteroposterior diameter during the relaxation phase. Aortic and right atrial pressures in excess of 80 mm Hg were generated. These pressures are greater than those generally obtained in adult animals with similar percent pulsatile displacements. CBF and MBF were also initially greater than those reported in adult animals undergoing conventional CPR. However, when CPR was prolonged beyond 20 min, aortic pressure fell and CBF and MBF declined to the near-zero levels seen in adult preparations. At 5 min of CPR, CBF and MBF were 24 ± 7 and 27 ± 7 ml·min^-1·100 g^-1 (50% and 17% of the values during cardiac arrest), respectively. With the continuous infusion of epinephrine (4 μg/kg/min) in another group of animals, MBF was significantly greater at 20 min of CPR and CBF and cerebral O₂ uptake were greater at 35 min of CPR as a result of higher perfusion pressures. At 5 min of CPR, CBF and MBF were 46 ± 9 and 65 ± 16 ml·min^-1·100 g^-1, respectively. CBF and cerebral oxygen uptake were maintained at prearrest levels for 20 min of CPR. Epinephrine did not appear to have an adverse effect on cerebral oxygenation because cerebral O₂ extraction was lower in the epinephrine group. In conclusion, we found that the infusion of epinephrine in a piglet preparation of CPR increased MBF, CBF, and cerebral oxygen uptake by selective vasoconstriction of other vascular beds. Compared with adult preparations, conventional CPR in infant piglets generated higher intrathoracic vascular pressures, MBF, and CBF, which may be related to the change in chest shape seen in this infant CPR preparation.