Geddes Leslie A, Roeder Rebecca A, Kemeny André, Otlewski Michael
Department of Biomedical Engineering, Purdue University, West Lafayette, IN 47907-2022, USA.
Am J Emerg Med. 2005 Mar;23(2):138-41. doi: 10.1016/j.ajem.2004.03.003.
The duration of untreated (no cardiopulmonary resuscitation) ventricular fibrillation (VF) needed to produce postdefibrillation pulseless electrical activity (PEA) was determined in 9 anesthetized swine ranging in weight from 20 to 30 kg. VF was induced electrically by a right ventricular catheter electrode, while arterial pressure and the electrocardiogram were recorded. VF was confirmed by the presence of VF waves in the electrocardiogram and a loss of pulsatile arterial pressure. VF was allowed to persist for 15-second increments (eg, 15, 30, 45, etc), after which defibrillation was achieved with transchest electrodes and the presence or absence of PEA was noted. If PEA was present, rhythmic chest compressions were applied to rescue the animal. Just after initiation of VF and just before defibrillation, VF wave frequency was measured. PEA was encountered in 100% of the trials after 180 seconds of VF. The threshold duration for PEA was 60 seconds. VF wave frequency decreased with the passage of time. At VF initiation, VF wave frequency (f0) ranged from 6 to 15 per second, with a mean of 10.1+/-2.1 per second. At 180 seconds (f180), the mean frequency was 4.0+/-0 per second. It was only possible to eliminate PEA and restore pumping in 1 animal when untreated VF lasted more than 180 seconds. There was no clear transition in the frequency of the VF waves with the passage of time that could predict the possibility of postdefibrillation PEA. Moreover, because of the different initial VF wave frequencies and the different rates of decrease with time, a measurement of VF wave frequency is unlikely to be informative on how long VF had been present. A consistent finding in this swine study of prolonged untreated VF was a rise in blood K+ which increased from a normal prefibrillation value of about 4 mEq/L to 8 to 12 mEq/L at 180 seconds. The longer the duration of VF, the higher the K+.
在9只体重为20至30千克的麻醉猪身上，测定了产生除颤后无脉电活动（PEA）所需的未治疗（无心肺复苏）室颤（VF）持续时间。通过右心室导管电极电诱导VF，同时记录动脉压和心电图。通过心电图中VF波的存在和搏动性动脉压的消失来确认VF。让VF持续15秒的增量（例如，15、30、45等），之后用经胸电极进行除颤，并记录是否存在PEA。如果存在PEA，则进行有节奏的胸外按压以抢救动物。在VF开始时和除颤前，测量VF波频率。在VF持续180秒后的所有试验中均出现了PEA。PEA的阈值持续时间为60秒。VF波频率随时间下降。在VF开始时，VF波频率（f0）范围为每秒6至15次，平均为每秒10.1±2.1次。在180秒时（f180），平均频率为每秒4.0±0次。只有当未治疗的VF持续超过180秒时，才有可能在1只动物身上消除PEA并恢复心脏泵血功能。随着时间的推移，VF波的频率没有明显的转变能够预测除颤后PEA的可能性。此外，由于初始VF波频率不同以及随时间下降的速率不同，测量VF波频率不太可能提供关于VF存在时长的有用信息。在这项关于延长未治疗VF的猪研究中，一个一致的发现是血钾升高，从室颤前约4 mEq/L的正常水平升至180秒时的8至12 mEq/L。VF持续时间越长，血钾越高。
