Arterial-Venous Perfusion Without Anticoagulation to Reverse Accidental Hypothermia

------------------To investigate a means of rewarming individuals suffering from accidental hypothermia, five Yucatan swine were topically cooled to a core body temperature of 3QoC. No heparin or any other means of anticoagulation was administered. An extracorporeal circuit consisting of polyvinylchloride tubing, a Bio-Pump and an external stainless steel heat exchanger was utilized and primed with an albuminized Ringers solution. An arterial-venous circuit was employed with oxygenation being provided by the animals' lungs. A series of aliquots of blood were taken and analyzed for coagulation prior to cannulation, after stabilization of blood flows, at a rectal rewarming temperature of 32oC and post-decannulation. All subjects were effectively rewarmed to 34oC, with a mean perfusion time of 64.8 ± 8.5 minutes. Coagulation parameters showed very little alteration from the control values taken: PT (11.9 ± .5), PTT (16.0 ± .9), platelet count (456.0 ± 105.6) and normal fibrinogen levels. Necropsy examination revealed only minimal clot formation within either the extracorporeal circuit or the animals' vascular system. Our results support the hypothesis that circulatory assistance and ultimately, extracorporeal circulation may be possible without anticoagulation. Introduction----------------Every winter, numerous individuals living in the colder regions, suffer life-threatening hypothermia because of exposure to the elements. An accepted method of treating these victims is with extracorporeal circulation (ECC) and rewarming,I-3 necessitating the use of systemic anticoagulation. Should these individuals be the unfortunate recipients of traumatic insults, debilitating hemorrhage could be a result of Address correspondence to: Anthony J. DelRossi, MD, Head, Div. of Cardiothoracic Surgery, Cooper Hospital/University Medical Center, Three Cooper Plaza, Suite 411, Camden, NJ 08103 Volume 21, Number 3, Fall1989 the systemic anticoagulation.3.4 Complications of such devastating hemorrhage are thrombocytopenia, cerebral hemorrhage, and death due to exsanguination. The elimination of anticoagulations in this modality of therapy would be a major contribution in reducing the morbidity and mortality associated with this procedure. An experimental animal protocol was designed and executed testing the following hypothesis: the moderately hypothermic subject could be successfully rewarmed using a modified cardiopulmonary bypass technique which excludes anticoagulation. Materials and Methods•------------Five Yucatan miniature swine,6 with an approximate weight of 25 kilograms, were used. The animals were anesthetized using Acepromazine and Ketamine intramuscularly (IM); the appropriate level of surgical anesthesia was maintained with sodium pentobarbital intravenously (IV). One hundred percent oxygen was delivered through an endotracheal tube. When necessary, respirations were manually assisted with an Ambobag. A four-lead electrocardiogram (EKG) was placed on the anterior chest wall of the animal for continuous EKG monitoring throughout the procedure. An 18-gauge arterial pressure monitoring catheter was inserted into the animal's left femoral artery for arterial pressure recording and as an access for removal of blood for laboratory analysis. This consisted of activated clotting times (ACT), prothrombin time (PT), partial thromboplastin time (PTT), platelet count, fibrin split products, and fibrinogen level tests. The left femoral vein was cannulated as a vascular access for an intravenous infusion consisting of one gram of Lidocaine in 250cc of Dextrose 5% in water (D5W), which was allocated at a slow rate with the purpose of keeping arrhythmias at a minimum. Once the animal's right groin was dissected, the right femoral artery and vein were then cannulated for bypass. Subsequently, the animal was covered with ice and ice water in an effort to quickly reduce the core body temperature to between 28 and 3QoC. This was measured by means of an indwelling rectal temperature probe. Both the The Journal of Extra-Corporeal Technology 83