Waveforms of external defibrillators: analysis and energy contribution.

BACKGROUND AND OBJECTIVE: Defibrillation is the most important therapy for terminating ventricular fibrillation in cardiac arrest patients. In addition to performing defibrillation at the earliest possible time, appropriate pulse energy and optimal waveform seem to be crucial for success. Emergency medical service personnel use different defibrillators and rely on their similarity of energy content. This study examined the true pulse energy content and waveform of 17 commonly used defibrillators. METHODS AND RESULTS: Defibrillation energies were selected to be 30, 200 or 360 J and defibrillators were discharged into test resistors, simulating transthoracic impedances of 25, 50 or 100 Ohms. Pulse energy deviated by up to +23% or -29% from the selected energy. Pulse energy within the initial 8 ms ranged from 90 to 30% of total pulse energy. Fourteen defibrillators utilising damped sinusoidal waveforms produced a monophasic pulse when discharged into resistances of 50 Ohms and 100 Ohms. CONCLUSIONS: Defibrillators used at the same energy settings do not necessarily produce the same defibrillation pulse energy. All but one defibrillator actually use monophasic waveforms, leaving the potential advantage of biphasic waveforms unused. Energy accuracy of defibrillators needs to be improved, and biphasic waveforms should be used more.     

Increased frequency of thorax injuries with ACD-CPR.

A prospective, randomised out-of-hospital study in a two-tiered system with active compression-decompression (ACD) cardiopulmonary resuscitation (CPR) versus standard (STD) CPR in patients following non-traumatic cardiac arrest was planned to test the hypothesis that ACD-CPR by the first tier may increase the occurrence of ventricular fibrillation as compared with STD-CPR. Furthermore, in a later phase of the study, sternal and rib fractures induced by both CPR methods were determined by extensive autopsy. After enrolling 90 patients the study was terminated because of a high frequency of chest injuries found at autopsy. Forty-two patients received STD-CPR from the first tier and ACD-CPR from the second tier. Thirty-three patients received ACD-CPR only by the first and the second tier, while 15 patients received STD-CPR only from the first and second tiers. In order to obtain a sufficiently large control group for autopsy findings after STD-CPR, STD-CPR was performed in an additional 33 patients within a second period of 4 months. There was no improvement in the number of patients found in ventricular fibrillation after ACD-CPR as compared to STD-CPR performed by the first tier. In patients undergoing autopsy (n = 35) there were significantly more sternal fractures with ACD-CPR versus STD-CPR (14/15 vs. 6/20; P <0.005) and rib fractures (13/15 vs. 11/20; P < 0.05) In conclusion, ACD-CPR appears to cause more CPR-related injuries than does standard CPR, but as a result of a number of limitations on this study, this fact cannot be proven beyond doubt.     

犬50%Ⅲ度烧伤后早期脏器含水量的变化

本实验观察了犬50％Ⅲ度烧伤后不输液以及按Parkland公式立即和延迟补液后,主要脏器血管外水量、残留血液水量和总水量的变化,以检测补液迟早对组织含水量的影响。结果表明:50％Ⅲ度烧伤的狗,不管输液与否或迟早,多数脏器含水量均高于正常,特别是血管外水量增加较多,而残留血液水量大多增加不显著。表明烧伤后脏器含水量的增加,主要系组织水肿,而脏器充血或瘀血不显著。     

Vasopressin decreases endogenous catecholamine plasma concentrations during cardiopulmonary resuscitation in pigs

OBJECTIVE: The purpose of this study was to evaluate the effect of vasopressin vs. saline placebo on catecholamine plasma concentrations during cardiopulmonary resuscitation (CPR). DESIGN: Prospective, randomized laboratory investigation by using an established porcine CPR model with instrumentation for measurement of hemodynamic variables, vital organ blood flow, and return of spontaneous circulation. SETTING: University hospital laboratory. SUBJECTS: Sixteen domestic pigs. INTERVENTIONS: After 15 mins of untreated cardiac arrest and 3 mins of CPR, 16 pigs were randomized to be treated with either 0.8 U/kg vasopressin (n = 8) or placebo (normal saline; n = 8). Arterial epinephrine and norepinephrine plasma concentrations were sampled at prearrest, after 1.5 mins of chest compressions, and at 1.5 mins and 5 mins after drug administration during CPR. MEASUREMENTS AND MAIN RESULTS: In comparison with placebo pigs at 1.5 and 5 mins after drug administration, animals resuscitated with vasopressin had significantly (p < .01) higher mean +/- SEM left ventricular myocardial (131+/-27 vs. 10+/-1 mL x mins(-1) x 100 g(-1) and 62+/-13 vs. 9+/-2 mL x mins(-1) x 100 g(-1)); total cerebral (90+/-8 vs. 14+/-3 mL x mins(-1) x 100 g(-1) and 51+/-4 vs. 12+/-2 mL x mins(-1) x 100 g(-1)); and adrenal gland perfusion (299+/-36 vs. 38+/-7 mL x mins(-1) x 100 g(-1) and 194+/-23 vs. 29+/-5 mL x mins(-1) x 100 g(-1)). Significantly lower mean +/- SEM epinephrine concentrations in the vasopressin pigs compared with the placebo group were measured 1.5 mins and 5 mins after drug administration, (24167+/-7919 vs. 80223+/-19391 pg/mL [p < .01] and 8346+/-1454 vs. 71345+/-10758 pg/mL [p < .01]). Mean +/- SEM norepinephrine plasma concentrations in the vasopressin animals in comparison with placebo were at 1.5 and 5 mins after drug administration significantly lower (41729+/-13918 vs. 82756+/-9904 pg/mL [p = .01] and 10642+/-3193 vs. 62170+/-8797 pg/mL [p < .01]). CONCLUSIONS: Administration of vasopressin during CPR resulted in significantly superior vital organ blood flow, but significantly decreased endogenous catecholamine plasma concentrations when compared with placebo.     

The effectiveness of ERC advanced life support (ALS) provider courses for the retention of ALS knowledge

Purpose

Out-of-hospital emergency physicians in Austria need mandatory emergency physician training, followed by biennial refresher courses. Currently, both standardized ERC advanced life support (ALS) provider courses and conventional refresher courses are offered. This study aimed to compare the retention of ALS-knowledge of out-of-hospital emergency physicians depending on whether they had or had not participated in an ERC-ALS provider course since 2005.

Methods

Participants (n = 807) from 19 refresher courses for out-of-hospital emergency physicians answered eight multiple-choice questions (MCQ) about ALS based on the 2005 ERC guidelines. The pass score was 75% correct answers. A multivariate logistic regression analyzed differences in passing scores between those who had previously participated in an ERC-ALS provider course and those who had not. Age, gender, regularity of working as an out-of-hospital emergency physician and the self-reported number of real resuscitation efforts within the last 6 months were entered as control variables.

Results

Out-of-hospital emergency physicians who had previously attended an ERC-ALS provider course had a significantly higher chance of passing the MCQ test (OR = 1.60, p = 0.015). Younger age (OR = 0.95, p < 0.001), regular work as an out-of-hospital emergency physician (OR = 2.66, p < 0.001) and a higher number of self-reported resuscitations within the last 6 months (OR = 1.08, p = 0.002) were also significant predictors of passing the test.

Conclusion

Out-of-hospital emergency physicians that had attended an ERC-ALS provider course since 2005 had a higher retention of ALS knowledge compared to non-ERC-ALS course participants.