CARDIOPULMONARY RESUSCITATION Elfect 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 2week-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 these 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 recoil 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 minl 100 g 1 (50% and 17% of the values during cardiac arrest), respectively. With the continuous infusion of epinephrine (4 ,ug/kg/min) in another group of animals, MBF was significantly greater at 20 min of CPR and CBF and cerebral 02 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.min1.00 g, 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 02 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. Circulation 73, No. 4, 809-817, 1986. CARDIOPULMONARY RESUSCITATION (CPR) has been extensively studied in adult animals, -3 but until recently,4 there have been no previous laboratory studies of CPR in infant animals. Recent work in adult From the Departments of Anesthesiology/Critical Care Medicine and Medicine, Respiratory Division, The Johns Hopkins Medical Institutions, Baltimore. Supported by National Institutes of Health grant NS 20020. Address for correspondence: Dr. Charles L. Schleien, Department of Anesthesiology, Critical Care Medicine, The Johns Hopkins Hospital, 600 North Wolfe St., Baltimore, MD 21205. Received June 13, 1985; revision accepted Jan. 16, 1986. Vol. 73, No. 4, April 1986 animals suggests that CPR may generate aortic blood flow without causing direct cardiac compression. Experimental studies indicate that the increase in intrathoracic pressure caused by external chest compression produces an extrathoracic arterial-venous pressure gradient that generates extrathoracic blood flow.' In many studies of adult animals, conventional CPR produces only small changes in intrathoracic vascular pressures and correspondingly low levels of cerebral and myocardial blood flows.2 3 5 However, switching to simultaneous compression-ventilation CPR increases intrathoracic vascular pressures and cerebral 809 by gest on July 6, 2017 http://ciajournals.org/ D ow nladed from