ORIGINAL CONTRIBUTION CPR, intravenous drug delivery; drug delivery, intravenous, in CPR; radioisotopes Comparison of Superior Vena Caval and Inferior Vena Caval Access Using a Radioisotope Technique During Normal Perfusion and Cardiopulmonary Resuscitation Recent studies of thoracic pressure changes during external cardiopulmo- nary resuscitation (CPR) suggest that there may be a significant difference in the rate of delivery of intravenous drugs when they are administered through the extrathoracic inferior vena cava (IVC) rather than the intra- thoracic superior vena cava (SVC). Comparison of delivery of a radionuclide given using superior and inferior vena caval access sites was made during normal blood flow and during CPR. Mean times from injection to peak emission count in each ventricle were determined. There were no significant differences between mean peak times for SVC or IVC routes during normal flow or CPR. When peak times were corrected for variations in cardiac out- put, there were no significant differences between IVC and SVC peak times during normal flow. During CPR, however, mean left ventricular peak time, when corrected for cardiac output, was significantly shorter (P < .05) when the SVC route was used. The mean time for the counts to reach half the ventricular peak was statistically shorter (P < .05) in both ventricles with the SVC route during the low flow of CPR. This suggests that during CPR, increased drug dispersion may occur when drugs are infused by the IVC route and thus may modify the anticipated effect of the drug bolus. These results suggest that during CPR, both the cardiac output and the choice of venous access are important variables for drug delivery. [Dalsey WC, Barsan WG, loyce SM, Hedges JR, Lukes SJ, Doan LA: Comparison of superior vena caval and inferior vena caval access using a radioisotope technique during norm.al perfusion and cardiopulmonary resuscitation. Ann Emerg Med Oc- tober 1984;13:881-884.] INTRODUCTION Drug therapy is an important aspect of advanced cardiac resuscitation, and rapid delivery to the site of action is considered critical. The most effective route of administration of pharmacologic agents during cardiopulmonary re- suscitation (CPR) has not been determined. Although central venous access may provide more rapid delivery than does peripheral venous access, i,2 it is unknown whether superior vena caval access is more effective than inferior vena caval access. Current guidelines for advanced CPR advocate the subclavian, internal jugular, and femoral routes for intravenous drug administration.S Recent evi- dence suggests that a significant percentage of blood flow during closed-chest CPR is generated by changes in intrathoracic pressure. 4 Venous valving oc- curs at the superior thoracic inlet during CPR, but it is unclear whether a valving mechanism exists at the diaphragmatic entrance to the thorax. If there is significant retrograde venous flow into the inferior vena cava during chest compressions, there may be a delay in drug delivery to the systemic circulation when agents are given by the femoral vein. This study was undertaken to determine whether there is a difference in the rate of delivery of drugs to the central circulation from the inferior vena cava (IVC) versus the superior vena cava (SVC) during both normal perfusion and external cardiac compression in a canine arrest model. Radionuclide- labeled albumin was used as a flow tracer to determine delivery times to the canine ventricles. William C Dalsey, MD* William G Barsan, MD* Steven M Joyce, MD* Jerris R Hedges, MD* Steven J Lukest Cincinnati, Ohio Lynnette A Doan, MD* Jacksonville, Florida From the Division of Emergency Medicine* and the Nuclear Medicine Laboratory,t University of Cincinnati, Cincinnati, Ohio; and the Division of Emergency Medicine, University Hospital of Jacksonville,* Jacksonville, Florida. Received for publication June 17, 1983. Revision received October 31, 1983. Accepted for publication December 20, 1983. Presented at the University Association for Emergency Medicine Annual Meeting in Boston, June 1983. Address for reprints: William G Barsan, MD, Division of Emergency Medicine, University of Cincinnati, 234 Goodman, ML #769, Cincinnati, Ohio 45267. 13:10 October 1984 Annals of Emergency Medicine 881/27