Favorable outcome after experimental cardiac arrest for 15min without preceding anticoagulation

Objectives: State-of-the-art cardiopulmonary resuscitation (CPR) restores circulation with inconsistent blood-flow and pressure. The use of extracorporeal circulation (ECC) following CPR opens the opportunity to gain more control over blood flow and pressure and is used more frequently. In animal experiments investigating CPR with ECC, administration of heparin before induced cardiac arrest (CA) is usual, but a major point of objection, since preliminary heparin administration in patients undergoing unobserved CA is not possible. In this study we investigate options for use of ECC without preceding heparinization after experimental 15min normothermic CA.

Methods: 12 pigs (54±3kg BW) were exposed to normothermic CA for 15min after induction of ventricular fibrillation. Cannulas for peripheral ECC were positioned during CA. Thereafter, ECC was started for 60 minutes yielding an arterial pressure of 70–80mmHg and a flow of 70–80ml/kgBW/min. 6 pigs received no anticoagulant before start of ECC. In 3 pigs, cannulas were flushed with heparinized saline after positioning during CA and further 3 pigs received heparin-coated cannulas. Pigs were weaned off ECC after 60min and allowed to regain consciousness. Neurologic recovery was assessed daily by a scoring system (Neurologic Deficit Score (NDS): 0=normal; 500=brain death) while MRI and brain histology were performed on day 7 after CA.

Results: All animals survived with continuous neurologic recovery from mildly depressed gait performance after 48 hours (NDS=10±15 without heparin and 18±16 with flushed or heparinized cannulas, p=0.43) until complete recovery on day 7 (NDS=0±0). 5/6 animals with no anticoagulant before start of ECC and 3/3 animals with heparinized cannulas showed moderate thrombus formation at the head of the venous cannula, but without functional relevance. No animal of the flushed-cannula group revealed clots. Ischemia-sensitive brain areas presented mild changes in MRI and brain histology in all animals, but no signs of infarction due to clots or emboli.

Conclusion: This study demonstrates that preliminary administration of heparin is not necessary for survival or neurologic recovery after experimental cardiac arrest and resuscitation using ECC. Heparin flushing seems sufficient to avoid thrombus formation in the cannulas. These findings may pave the way for use of ECC in patients undergoing sudden death.