SERUM POTASSIUM CONCENTRATION AS A PREDICTOR OF RESUSCITATION OUTCOMEIN HYPOTHERMIC CARDIAC-ARREST

The purpose of this study was to determine whether serum potassium con centration (S-K) can predict resuscitation outcome in a canine model o f severe hypothermic cardiac arrest. Fifteen adult mongrel anesthetize d dogs were immersed to the neck in a 4 degrees C water bath and venti lated with room air, with ventilation halved at 45 min and stopped at 90 min. After cardiac arrest, 14 of the dogs were kept in the water ba th for periods of 2-7 h, and another was held in arrest for 13 h. Foll owing 10 min of closed chest cardiopulmonary resuscitation (CPR) (simu lating a short transport time to a hospital), animals were placed on c ardiopulmonary bypass and rapidly rewarmed. With appearance of ventric ular fibrillation, animals were defibrillated up to three times. Stand ard advanced cardiac life support was initiated at a core temperature (T-C) of 30 degrees C. Eight of the 15 dogs had return of spontaneous circulation (ROSC), at T-C ranging from 30.4 to 36.5 degrees C. The ei ght dogs with ROSC did not differ from the seven without ROSC in time to arrest (128 +/- 48 versus 128 +/- 23 min) (mean +/- SD) or T-C at a rrest (18.1 +/- 2.2 versus 17.9 +/- 3.1 degrees C), but had higher T-C at the end of the arrest period (9.7 +/- 3.0 versus 5.2 +/- 2.0 degre es C), reflecting a shorter arrest period in the dogs with ROSC (225 /- 95 versus 420 +/- 193 min). S-K (mEq liter(-1)) did not differ betw een dogs with and without ROSC at baseline (3.5 +/- 0.4 versus 3.7 +/- 0.4) or at arrest (3.4 +/- 0.7 versus 4.3 +/- 2.2), but there was a t rend toward higher S-K at the end of arrest in the group without ROSC (4.6 +/- 1.5 versus 9.4 +/- 6.3; range 3.2-7.8 versus 3.5-21.4; p = .0 53). S-K was similar after 10 min of CPR in the groups with and withou t ROSC (6.6 +/- 2.9 versus 9.0 +/- 2.4; range 2.5-11.1 versus 4.5-11.0 ; p = .107). S-K after 10 min of CPR was higher in some animals with R OSC (9.6 and 11.1) than in others which did not have ROSC (4.5 and 7.9 ). We conclude that very high S-K following prolonged hypothermic card iac arrest may be suggestive of an inability to resuscitate. However, S-K after both prolonged hypothermic cardiac arrest and a brief period of CPR is not a good predictor of resuscitation using cardiopulmonary bypass rewarming in an animal model.