Revised resuscitation guidelines: adrenaline versus adrenaline/vasopressin in a pig model of cardiopulmonary resuscitation--a randomised, controlled trial

BACKGROUND: Synergistic effects of adrenaline (epinephrine) and vasopressin may be beneficial during cardiopulmonary resuscitation. However, it is unknown whether either adrenaline alone or an alternating administration of adrenaline and vasopressin is better for restoring vital organ perfusion following basic life support (BLS) according to the revised algorithm with a compression-to-ventilation (c/v) ratio of 30:2. MATERIAL AND METHODS: After 4min of ventricular fibrillation, and 6min of BLS with a c/v ratio of 30:2, 16 pigs were randomised to receive either 45microg/kg adrenaline, or alternating 45microg/kg adrenaline and 0.4U/kg vasopressin, respectively. RESULTS: Coronary perfusion pressure (mean+/-S.D.) 20 and 25min after cardiac arrest was 7+/-4 and 5+/-3mm Hg after adrenaline, and 25+/-2 and 14+/-3mm Hg after adrenaline/vasopressin (p<0.001 and <0.01 versus adrenaline), respectively. Cerebral perfusion pressure was 23+/-7 and 19+/-9mm Hg after adrenaline, and 40+/-10 and 33+/-7mm Hg after adrenaline/vasopressin (p<0.001 and <0.01 versus adrenaline), and cerebral blood flow was 30+/-10 and 27+/-11% of baseline after adrenaline, and 65+/-40 and 50+/-31% of baseline after adrenaline/vasopressin (p<0.05 versus adrenaline), respectively. Return of spontaneous circulation (ROSC) did not differ significantly between the adrenaline group (0/8) and the adrenaline/vasopressin group (3/8). CONCLUSION: Adrenaline/vasopressin resulted in higher coronary and cerebral perfusion pressures, and cerebral blood flow, while ROSC was comparable.     

Tertiary centres have improved survival compared to other hospitals in the Copenhagen area after out-of-hospital cardiac arrest

Aims

Out-of-hospital cardiac arrest (OHCA) has been reported to carry very varying morbidity and mortality. However, it remains unclear whether this is caused by intrinsic factors of the OHCA or due to the level of in-hospital care. The aim of this study is to compare 30-day and long-term mortality after OHCA at tertiary heart centres and non-tertiary university hospitals.

Methods and results

Data from the Copenhagen OHCA registry from June 2002 through December 2010 included a total of 1218 consecutive patients treated by the same mobile emergency care unit (MECU) with either return of spontaneous circulation (ROSC) or on-going resuscitation (n = 53) at hospital arrival. The MECU transported patients to the nearest hospital unless an ECG on scene suggested ST-segment elevation myocardial infarction, in which case patients were transported to the nearest tertiary centre for acute coronary angiography. Therefore, patients with ST-elevation myocardial infarction (n = 198) were excluded from the analysis. 30-day mortality was 56% vs. 76% and long term (up to 8 years) mortality was 78% vs. 94% for tertiary and non-tertiary hospitals, respectively, both p < 0.001. Multivariate analysis showed that admission to a non-tertiary hospital was independently associated with increased risk of death (HR = 1.32, 95% CI: 1.09–1.59, p = 0.004). Exclusion of patients with on-going resuscitation at admission resulted in HR = 1.34 (1.11–1.62), p = 0.003. A matched pair propensity score analysis of 255 patients confirmed the results of the proportional hazard analysis (HR = 1.35, 95% CI: 1.11–1.65 p = 0.003).

Conclusion

Admission to tertiary centres is associated with lower mortality rates after OHCA compared with non-tertiary hospitals.     

Perfluorocarbon induced intra-arrest hypothermia does not improve survival in a swine model of asphyxial cardiac arrest

Background

Pulseless electrical activity is an important cause of cardiac arrest. Our purpose was to determine if induction of hypothermia with a cold perfluorocarbon-based total liquid ventilation (TLV) system would improve resuscitation success in a swine model of asphyxial cardiac arrest/PEA.

Methods

Twenty swine were randomly assigned to control (C, no ventilation, n = 11) or TLV with pre-cooled PFC (n = 9) groups. Asphyxia was induced by insertion of a stopper into the endotracheal tube, and continued in both groups until loss of aortic pulsations (LOAP) was reached, defined as a pulse pressure less than 2 mmHg. The TLV animals underwent asphyxial arrest for an additional 2 min after LOAP, followed by 3 min of hypothermia, prior to starting CPR. The C animals underwent 5 min of asphyxia beyond LOAP. Both groups then underwent CPR for at least 10 min. The endpoint was the resumption of spontaneous circulation maintained for 10 min.

Results

Seven of 9 animals achieved resumption of spontaneous circulation (ROSC) in the TLV group vs. 5 of 11 in the C group (p = 0.2). The mean pulmonary arterial temperature was lower in total liquid ventilation animals starting 4 min after induction of hypothermia (TLV 36.3 ± 0.2 °C vs. C 38.1 ± 0.2 °C, p < 0.0001). Arterial pO₂ was higher in total liquid ventilation animals at 2.5 min of CPR (TLV 76 ± 12 mmHg vs. C 44 ± 2 mmHg; p = 0.03).

Conclusion

Induction of moderate hypothermia using perfluorocarbon-based total liquid ventilation did not improve ROSC success in this model of asphyxial cardiac arrest.     

Effects of sustained abdominal aorta compression on coronary perfusion pressures and restoration of spontaneous circulation during cardiopulmonary resuscitation in swine

Objectives

The present study was undertaken to explore whether sustained abdominal aorta compression-cardiopulmonary resuscitation (SAAC-CPR), as a means, can raise coronary perfusion pressure (CPP) as well as restoration of spontaneous circulation (ROSC) during CPR. In the present study, we hypothesised that SAAC-CPR elevates CPP during CPR and improves ROSC, without causing liver laceration.

Methods

Animals were randomised into one of two groups (Standard CPR and SAAC-CPR). Ten domestic swine (22-25 kg) were anaesthetised, intubated and mechanically ventilated. Ventricular fibrillation was induced, and after 3 min of untreated ventricular fibrillation, the animals were treated with standard CPR (with simplex chest compression (SCC) and epinephrine) or SAAC-CPR (SCC with sustained abdominal aorta compression, without epinephrine). CPP and ROSC were compared.

Results

SCC with sustained abdominal aorta compression (SCC + SAAC) significantly increased CPP in comparison with SCC during CPR (p < 0.05). The increase in CPP with SCC + SAAC is equivalent to that achieved with epinephrine (p > 0.05). All animals in the standard CPR and SAAC-CPR groups restored spontaneous circulation. No liver damage was found in post-mortem examinations of the swine subjects.

Conclusions

During CPR, non-invasive SAAC can rapidly and reversibly raise the CPP as much as can epinephrine and is especially suitable for out-of-hospital CPR.     

Increased survival after EMS witnessed cardiac arrest. Observations from the Resuscitation Outcomes Consortium (ROC) Epistry—Cardiac arrest

Background

Out of hospital cardiac arrest (OHCA) is common and lethal. It has been suggested that OHCA witnessed by EMS providers is a predictor of survival because advanced help is immediately available. We examined EMS witnessed OHCA from the Resuscitation Outcomes Consortium (ROC) to determine the effect of EMS witnessed vs. bystander witnessed and unwitnessed OHCA.

Methods

Data were analyzed from a prospective, population-based cohort study in 10 U.S. and Canadian ROC sites. Individuals with non-traumatic OHCA treated 04/01/06-03/31/07 by EMS providers with defibrillation or chest compressions were included. Cases were grouped into EMS-witnessed, bystander witnessed, and unwitnessed and further stratified for bystander CPR. Multiple logistic regressions evaluated the odds ratio (OR) for survival to discharge relative to the EMS-witnessed group after adjusting for age, sex, public/private location of collapse, ROC site, and initial ECG rhythm. Of 9991 OHCA, 1022 (10.2%) of EMS-witnessed, 3369 (33.7%) bystander witnessed, and 5600 (56.1%) unwitnessed.

Results

The most common initial rhythm in the EMS-witnessed group was PEA which was higher than in the bystander- and unwitnessed groups (p < 0.001). The adjusted OR (95% CI) of survival compared to the EMS-witnessed group was 0.41, (0.36, 0.46) in bystander witnessed with bystander CPR, 0.37 (0.33, 0.43) in bystander witnessed without bystander CPR, 0.17 (0.14, 0.20) in unwitnessed with bystander CPR and 0.21 (0.18, 0.24) in unwitnessed cases without bystander CPR.

Conclusions

Immediate application of prehospital care for OHCA may improve survival. Efforts should be made to educate patients to access 9-1-1 for prodromal symptoms.     

Coronary perfusion pressure during external chest compression in pseudo-EMD, comparison of systolic versus diastolic synchronization

Background

The fraction of cardiac arrest patients presenting with pulseless electrical activity is increasing, and it is likely that many of these patients have pseudo-electromechanical dissociation (P-EMD), a state in which there is residual cardiac contraction without a palpable pulse. The efficacy of cardiopulmonary resuscitation (CPR) with external chest compression synchronized with the P-EMD cardiac systole and diastole has not been fully evaluated.

Hypothesis

During external chest compression in P-EMD, the coronary perfusion pressure (CPP) will be greater with systolic synchronization compared with diastolic phase synchronization.

Methods

A porcine model of P-EMD induced by progressive hypoxia with peak aortic pressures targeted to 50 mmHg was used. CPR chest compressions were performed by either load distributing band or vest devices. Paired 10 s intervals of systolic and diastolic synchronization were performed randomly during P-EMD, and aortic, right atrial and CPP were compared.

Results

Stable P-EMD was achieved in 8 animals, with 2.6 ± 0.5 matched synchronization pairs per animal. Systolic synchronization was association with increases in relaxation phase aortic pressure (41.7 ± 8.9 mmHg vs. 36.9 ± 8.2 mmHg), and coronary perfusion pressure (37.6 ± 11.7 mmHg vs. 30.2 ± 9.6 mmHg). Diastolic synchronization was associated with an increased right atrial pressure (6.7 ± 4.1 mmHg vs. 4.1 ± 5.7 mmHg).

Conclusion

During P-EMD, synchronization of external chest compression with residual cardiac systole was associated with higher CPP compared to synchronization with diastole.     

叹息样呼吸与猪心肺复苏过程中血流动力学变化的研究

目的 研究CPR的病理生理过程,探讨叹息样呼吸对CPR过程中血流动力学的影响.方法 12头北京长白猪,体质量(30±1)kg,麻醉后气管插管,机械通气,连续记录实时呼吸参数.股动脉置管测量主动脉压(AOP),并抽取动脉血;肺动脉漂浮导管置测最右心房压(RAP)及心输出量(CO).以程控电刺激制作室颤(VF)模型.VF4 min后进行标准30:2 CPR 12 min,记录相关参数.结果 CPR过程中pH,PaCO2及乳酸逐渐升高,而PaO2逐渐降低,但PaO2在整个实验过程中均大于50mmHg.10只动物出现叹息样呼吸,但随时间推移逐渐减弱;未出现叹息样乎吸的2只动物均未复苏成功.标准心外按压在多数动物均可产生大干死腔量(VD)的被动通气,但其潮气量随时间推移逐渐减少.因此人工通气在总分钟通气量中所占比例逐渐增加.CO、冠脉灌注压(CPP)与叹息样呼吸分钟通气量(MVg)呈正相关(r分别等于0.736,0.721,P＜0.01);RAP与MVg呈负相关(r=-0.744,P＜0.01).结论 标准CPR能够维持机体12min的氧合;心外按压能够产生大于VD的被动通气;叹息样呼吸可以通过增加CO、CPP及降低RAP产生对自主循环的恢复产生有益的生理作用.

Abstract：

Objective Gasp was defined as a pathology respiration during cardiac arrest. This study was to investigate its effect on hemodynamics during CPR. Method Twelve domestic pigs, weighening (30 ± 1) kg,were anaesthetized. After tracheal intubation and mechanical ventilation, continuous respiratory variables were recorded. An artery catheter was inserted for reference blood samples and measuring aortic artery pressure (AOP).Right atrial pressure (RAP) and cardiac output (CO) were detected by Swan-Ganz catheter. Ventricular fibrillation (VF) was induced by programmed electrical stimulation instruments. After 4 minutes untreated VF, standard 30:2 CPR was done for 12 minutes and the parameters were recorded. Results pH, PaCO2 and lactic acid increased and PaO2 decreased progressively during CPR, whereas PaO2 was up to 50mmHg during the whole protocol. Gasps were observed in 10 animals, but weaken gradually; the left 2 animals with no gasp did not restore of spontaneous circulation (ROSC). Standard CPR could produce passive ventilation more than dead space (VD), but its tidal volume decreased gradually, which led to the percentage of rescue ventilation increased progressively. Positive correlations were found between CO, coronary perfusion pressure (CPP) and minute ventilation of gasps (MVg) (r was 0.736 and 0.721 respectively, both P ＜0.01); negative correlation were found between RAP and MVg (r= -0. 744, P ＜ 0.01). Conclusions Standard CPR could maintain 12 minutes oxygenation of body; compressions could produce enough passive ventilation more than VD; gasps were benefit to ROSC by increasing CO, CPP and decreasing RAP.     

腹部提压法对窒息性心搏骤停猪复苏效果的实验研究

目的 比较胸外按压心肺复苏(CC-CPR)与腹部提压心肺复苏(ALC-CPR)对窒息性心搏骤停猪复苏时血流动力学指标和呼吸指标的影响,初步评价腹部提压法对窒息性心搏骤停猪的复苏效果.方法 健康家猪30只,按随机数字表法分为两组,每组15只.建立窒息性心搏骤停模型,分别实施CC-CPR和ALC-CPR.窒息前10 min开始连续记录心电图(ECG)、脉搏血氧饱和度(SpO2)、呼气末二氧化碳分压(PEICO2)、主动脉收缩压(SBP)、舒张压(DBP)、中心静脉压(CVP)和潮气量(VT)直至实验结束;计算主动脉平均动脉压(MAP)、冠状动脉灌注压(CPP)和分钟通气量(MV);分别在窒息前10 min、窒息后10 min及复苏后5、10、20 min抽取动脉血查血气.观察两组动物的自主循环恢复(ROSC)率、24 h存活率和24 h后神经功能缺损评分.结果 两组窒息前10 min和窒息后10 min各项指标均无明显差异.复苏后2min,CC-CPR组MAP( mm Hg,1 mm Hg=0.133 kPa)和CPP(mm Hg)高于ALC-CPR组(MAP:43.60±12.91比33.40±6.59,P＜0.05;CPP:21.67±11.28比11.80±4.16,P＜0.01);ALC-CPR组VT(ml)和MV( L/min)高于CC-CPR组(VT:111.67±18.12比56.60±7.76; MV:11.17±1.81比5.54±0.79,均P＜0.01).在复苏后5、10、20 min,ALC-CPR组pH值、动脉血氧分压(PaO2,mm Hg)和动脉血氧饱和度(SaO2)均升高,HCO3-(mmol/L)、剩余碱(BE,mmol/L)均降低,且均高于CC-CPR组(复苏20 min时pH值:7.16±0.16比7.01±0.14; PaO2:82.73±13.20比58.33±17.77;HCO3-:27.71±3.11比21.04±3.62; BE:-4.78±4.30比-10.23±2.12;SaO2:0.893±0.088比0.764±0.122),动脉血二氧化碳分压(PaCO2,mm Hg)、K+(mmol/L)和乳酸(Lac,mmol/L)均明显低于CC-CPR组(复苏20 min时PaCO2:49.40±15.60比79.80±15.35;K+:7.18±1.76比8.55±1.02;Lac:8.17±1.46比10.39±1.92),差异均有统计学意义(P＜0.05或P＜0.01).ALC-CPR组ROSC率、24 h存活率明显高于CC-CPR组(ROSC率:80.0％比26.7％,P＜0.01;24h存活率:60.0％比13.3％,P＜0.05),24 h神经功能评分(分)低于CC-CPR组(1.11±0.33比3.50±0.70,P＜0.01).结论 在窒息性心搏骤停猪的复苏早期,ALC-CPR较CC-CPR更具优势.     

Tilting for perfusion: Head-up position during cardiopulmonary resuscitation improves brain flow in a porcine model of cardiac arrest

IntroductionCerebral perfusion is compromised during cardiopulmonary resuscitation (CPR). We hypothesized that beneficial effects of gravity on the venous circulation during CPR performed in the head-up tilt (HUT) position would improve cerebral perfusion compared with supine or head-down tilt (HDT).MethodsTwenty-two pigs were sedated, intubated, anesthetized, paralyzed and placed on a tilt table. After 6 min of untreated ventricular fibrillation (VF) CPR was performed on 14 pigs for 3 min with an automated CPR device called LUCAS (L) plus an impedance threshold device (ITD), followed by 5 min of L-CPR + ITD at 0° supine, 5 min at 30° HUT, and then 5 min at 30° HDT. Microspheres were used to measure organ blood flow in 8 pigs. L-CPR + ITD was performed on 8 additional pigs at 0°, 20°, 30°, 40°, and 50° HUT.ResultsCoronary perfusion pressure was 19 ± 2 mmHg at 0° vs. 30 ± 3 at 30° HUT (p < 0.001) and 10 ± 3 at 30° HDT (p < 0.001). Cerebral perfusion pressure was 19 ± 3 at 0° vs. 35 ± 3 at 30° HUT (p < 0.001) and 4 ± 4 at 30° HDT (p < 0.001). Brain–blood flow was 0.19 ± 0.04 ml min⁻¹ g⁻¹ at 0° vs. 0.27 ± 0.04 at 30° HUT (p = 0.01) and 0.14 ± 0.06 at 30° HDT (p = 0.16). Heart blood flow was not significantly different between interventions. With 0, 10, 20, 30, 40 and 50° HUT, ICP values were 21 ± 2, 16 ± 2, 10 ± 2, 5 ± 2, 0 ± 2, −5 ± 2 respectively, (p < 0.001), CerPP increased linearly (p = 0.001), and CPP remained constant.ConclusionDuring CPR, HDT decreased brain flow whereas HUT significantly lowered ICP and improved cerebral perfusion. Further studies are warranted to explore this new resuscitation concept.     

窒息心脏骤停动物模型中碳酸氢钠对复苏的影响

目的 研究碳酸氢钠(sodium bicarbonate,SB)在窒息心脏骤停(asphyxiation cardiac arrest,ACA)动物模型中对复苏预后的影响.方法 32只五指山幼猪随机(随机数方法)平均分成SB组(n=16)和对照组(n=16),通过在呼吸末堵塞气管插管方法制作窒息型的心脏骤停模型,在成功制作心脏骤停模型后8 min后行标准心肺复苏.SB组在复苏即刻予以SB(1.0 mEq/kg稀释到40 mL)静脉推注,对照组予以40 mL生理盐水静脉推注.比较两组实验动物的自主循环恢复(return of spontaneous circulation,ROSC)率,复苏前和复苏后6h内血压,心排血量(cardiac output,CO)血液pH值,血清钠离子浓度变化.在基础状态以及复苏后6h利用正电子发射型计算机断层显像(positron emission tomography,PET)测定左心室心肌代谢最大标准化摄取值(themaximum standardized uptake value,SUVmax).结果 SB组复苏成功率(10/16)较对照组复苏成功率(8/16)高,6h生存时间均值SB组较对照组长(3.63±0.76) hvs.(2.45±0.70)h,但差异均无统计学意义;两组实验动物在复苏前后血清钠离子比较差异无统计学意义;复苏后6h两组左心室心肌代谢SUVmax比较:SB组较对照组要高(1.32±0.20)vs.(1.10±0.14),P=0.035.结论 窒息心脏骤停在复苏过程中使用SB可能会增加复苏成功率以及改善复苏后心肌代谢,且没有发生高钠血症.     

The effects of an automatic,low pressure and constant flow ventilation device versus manual ventilation during cardiovascular resuscitation in a porcine model of cardiac arrest

Background

Cardiac arrest is an important cause of mortality. Cardiopulmonary resuscitation (CPR) improves survival, however, delivery of effective CPR can be challenging and combining effective chest compressions with ventilation, while avoiding over-ventilation is difficult. We hypothesized that ventilation with a pneumatically powered, automatic ventilator (Oxylator^®) can provide adequate ventilation in a model of cardiac arrest and improve the consistency of ventilations during CPR.

Methods/results

Twelve pigs (∼40 kg, either sex) underwent 3 episodes each of cardiac arrest and resuscitation consisting of 30 s of untreated ventricular fibrillation, followed by 5 min of CPR, defibrillation, and ∼30 min of recovery. During CPR in each episode, pigs were ventilated in 1 of 3 ways in random balanced order: manual ventilation using AMBU bag (12 breaths/min), low pressure Oxylator^® (maximum airway pressure 15 cmH₂O with 20 L/min constant flow in automatic mode [Ox15/20]), or high pressure Oxylator^® (maximum airway pressure 20 cmH₂O with 30 L/min constant flow in automatic mode [Ox20/30]). During CPR, both Ox15/20 and Ox20/30 resulted in higher levels of positive end expiratory pressure than manual ventilation. Ox15/20 ventilation also resulted in higher arterial pCO₂ than manual ventilation. Ox20/30 ventilation yielded higher arterial pO₂ and a lower arterial–alveolar gradient than manual ventilation. All pigs were successfully defibrillated, and no measured haemodynamic variables were different between the groups.

Conclusion

Ventilation with an automatic ventilation device during CPR is feasible and provides adequate ventilation and comparable haemodynamics when compared to manual bag ventilation.     

Extended series of cardiac compressions during CPR in a swine model of perinatal asphyxia

Background

The rationale for a compression to ventilation ratio of 3:1 in neonates with primary hypoxic, hypercapnic cardiac arrest is to emphasize the importance of ventilation; however, there are no published studies testing this approach against alternative methods. An extended series of cardiac compressions offers the theoretical advantage of improving coronary perfusion pressures and hence, we aimed to explore the impact of compression cycles of two different durations.

Materials and methods

Newborn swine (n = 32, age 12-36 h, weight 2.0-2.7 kg) were progressively asphyxiated until asystole occurred. Animals were randomized to receive compressions:ventilations 3:1 (n = 16) or 9:3 (n = 16). Return of spontaneous circulation (ROSC) was defined as a heart rate ≥100 beats min⁻¹.

Results

All animals except one in the 9:3 group achieved ROSC. One animal in the 3:1 group suffered bradycardia at baseline, and was excluded, leaving us with 15 animals in each group surviving to completion of protocol. Time to ROSC (median and interquartile range) was 150 s (115-180) vs. 148 s (116-195) for 3:1 and 9:3, respectively (P = 0.74). There were no differences in diastolic blood pressure during compression cycles or in markers of hypoxia and inflammation. The temporal changes in mean arterial blood pressure, heart rate, arterial blood gas parameters, and systemic and regional oxygen saturation were comparable between groups.

Conclusion

Neonatal pigs with asphyxia-induced cardiac arrest did not respond to a compression:ventilation ratio of 9:3 better than to 3:1. Future research should address if alternative compression:ventilation ratios offer advantages over the current gold standard of 3:1.     

Managing cardiac arrest with refractory ventricular fibrillation in the emergency department: Conventional cardiopulmonary resuscitation versus extracorporeal cardiopulmonary resuscitation

AimRefractory ventricular fibrillation, resistant to conventional cardiopulmonary resuscitation (CPR), is a life threatening rhythm encountered in the emergency department. Although previous reports suggest the use of extracorporeal CPR can improve the clinical outcomes in patients with prolonged cardiac arrest, the effectiveness of this novel strategy for refractory ventricular fibrillation is not known. We aimed to compare the clinical outcomes of patients with refractory ventricular fibrillation managed with conventional CPR or extracorporeal CPR in our institution.MethodThis is a retrospective chart review study from an emergency department in a tertiary referral medical center. We identified 209 patients presenting with cardiac arrest due to ventricular fibrillation between September 2011 and September 2013. Of these, 60 patients were enrolled with ventricular fibrillation refractory to resuscitation for more than 10 min. The clinical outcome of patients with ventricular fibrillation received either conventional CPR, including defibrillation, chest compression, and resuscitative medication (C-CPR, n = 40) or CPR plus extracorporeal CPR (E-CPR, n = 20) were compared.ResultsThe overall survival rate was 35%, and 18.3% of patients were discharged with good neurological function. The mean duration of CPR was longer in the E-CPR group than in the C-CPR group (69.90 ± 49.6 min vs 34.3 ± 17.7 min, p = 0.0001). Patients receiving E-CPR had significantly higher rates of sustained return of spontaneous circulation (95.0% vs 47.5%, p = 0.0009), and good neurological function at discharge (40.0% vs 7.5%, p = 0.0067). The survival rate in the E-CPR group was higher (50% vs 27.5%, p = 0.1512) at discharge and (50% vs 20%, p = 0. 0998) at 1 year after discharge.ConclusionsThe management of refractory ventricular fibrillation in the emergency department remains challenging, as evidenced by an overall survival rate of 35% in this study. Patients with refractory ventricular fibrillation receiving E-CPR had a trend toward higher survival rates and significantly improved neurological outcomes than those receiving C-CPR.     

Different roles of nitric oxide synthase isoforms in cardiopulmonary resuscitation in pigs

The purpose of the present study was to identify the roles of the three nitric oxide synthase (NOS) isoforms on whole body ischemia-reperfusion injury during cardiopulmonary resuscitation (CPR) with periodic acceleration (pGz) in pigs. Thirty-two anesthetized pigs (27.6+/-3.4 kg) were monitored for hemodynamics and selected echocardiographic variables. Twenty minutes after NOS inhibition or placebo administration, ventricular fibrillation (VF) was induced and remained untreated for 3 min, followed by CPR with pGz for 15 min, plus 3 min of manual chest compressions and defibrillation attempt. Four groups were studied: (1) saline control; (2) L-NAME (non-selective NOS inhibitor); (3) aminoguanidine (inducible NOS inhibitor); (4) TRIM (neuronal NOS inhibitor). Return of spontaneous circulation (ROSC) to 180 min occurred in 6/8 controls, 4/8 L-NAME, 7/8 aminoguanidine, and 2/8 TRIM animals. The L-NAME group had significantly lower organ blood flow, impaired cardiac function, but higher vascular tone than control group. The aminoguanidine group had the highest organ blood flows and survival rate. Six out of eight TRIM treated animals had initial return of heartbeat; however, with impaired heart contractility and could not survive more than 20 min of ROSC. This study reveals the differential role of endogenous NO produced from the three NOS isoforms during pGz-CPR. Both endothelial and neuronal NOS derived NO show predominantly protective effects while inducible NOS derived NO plays a detrimental role in pGz-CPR. The present study has shown that cardiac arrest and resuscitation appears to be associated with a different expression of NOS isoforms which appear to affect resuscitation outcomes differently.     

A tourniquet assisted cardiopulmonary resuscitation augments myocardial perfusion in a porcine model of cardiac arrest

ObjectiveDuring cardiopulmonary resuscitation (CPR), myocardial blood flow generated by chest compression rarely exceeds 35% of its normal level. Cardiac output generated by chest compression decreases gradually with the prolongation of cardiac arrest and resuscitation. Early studies have demonstrated that myocardial blood flow during CPR is largely dependent on peripheral vascular resistance. In this study, we investigated the effects of chest compression in combination with physical control of peripheral vascular resistance assisted by tourniquets on myocardial blood flow during CPR.MethodsVentricular fibrillation was induced and untreated for 7 min in ten male domestic pigs weighing between 33 and 37 kg. The animals were then randomized to receive CPR alone or a tourniquet assisted CPR (T-CPR). In the CPR alone group, chest compression was performed by a miniaturized mechanical chest compressor. In the T-CPR group, coincident with the start of resuscitation, the thin elastic tourniquets were wrapped around the four limbs from the distal end to the proximal part. After 2 min of CPR, epinephrine (20 μg/kg) was administered via the femoral vein. After 5 min of CPR, defibrillation was attempted by a single 150 J shock. If resuscitation was not successful, CPR was resumed for 2 min before the next defibrillation. The protocol was continued until successful resuscitation or for a total of 15 min. Five minutes after resuscitation, the elastic tourniquets were removed. The resuscitated animals were observed for 2 h.ResultsT-CPR generated significantly greater coronary perfusion pressure, end-tidal carbon dioxide and carotid blood flow. There was no difference in both intrathoracic positive and negative pressures between the two groups. All animals were successfully resuscitated with a single shock in both groups. There were no significant changes in hemodynamics observed in the animals treated in the T-CPR group before-and-after the release of tourniquets at post-resuscitation 5 min.ConclusionsT-CPR improves myocardial and cerebral perfusion during CPR. It may provide a new and convenient method for augmenting myocardial and cerebral blood flow during CPR.     

Intra-arrest selective brain cooling improves success of resuscitation in a porcine model of prolonged cardiac arrest

Aims of study

We have previously demonstrated that early intra-nasal cooling improved post-resuscitation neurological outcomes. The present study utilizing a porcine model of prolonged cardiac arrest investigated the effects of intra-nasal cooling initiated at the start of cardiopulmonary resuscitation (CPR) on resuscitation success. Our hypothesis was that rapid nasal cooling initiated during “low-flow” improves return of spontaneous resuscitation (ROSC).

Methods

In 16 domestic male pigs weighing 40 ± 3 kg, VF was electrically induced and untreated for 15 min. Animals were randomized to either head cooling or control. CPR was initiated and continued for 5 min before defibrillation was attempted. Coincident with starting CPR, the hypothermic group was cooled with a RhinoChill™ device which produces evaporative cooling in the nasal cavity of pigs. No cooling was administrated to control animals. If ROSC was not achieved after defibrillation, CPR was resumed for 1 min prior to the next defibrillation attempt until either successful resuscitation or for a total of 15 min.

Main results

Seven of eight animals in the hypothermic group (87.5%) and two of eight animals in control group (25%) (p = 0.04) were successfully resuscitated. At ROSC, brain temperature was increased from baseline by 0.3 °C in the control group, and decreased by 0.1 °C in the hypothermic animals. Pulmonary artery temperature was above baseline in both groups.

Conclusion

Intra-nasal cooling initiated at the start of CPR significantly improves the success of resuscitation in a porcine model of prolonged cardiac arrest. This may have occurred by preventing brain hyperthermia.     

Out-of-hospital cardiac arrest from air embolism during sexual intercourse: case report and review of the literature

We report the successful resuscitation of a 38-year-old woman in cardiac arrest following heterosexual intercourse 7 days after spontaneous abortion and an instrumental uterine evacuation. The collapse was thought to be due to venous air embolism (VAE). Her survival neurologically intact was attributed to appropriate first aid, pre-hospital and subsequent hospital intensive care. Neither a case of an out-of-hospital air embolism where the patient made a good recovery, nor a case of miscarriage followed by collapse from air embolism has been reported in the literature. Air embolism is a very infrequent cause of out-of-hospital cardiac arrest with a high mortality rate. Predominant causal reasons are severe penetrating neck or thoracic injuries and sexual activities in pregnancy, when air can pass into the damaged veins in the wall of the uterus and lead to total obstruction in the heart. Diagnostics and management techniques for venous air embolism are discussed. Air embolism should be included in the differential diagnosis for all young women in cardiac arrest, particularly when occurring during sexual activity. Instructions in risks of sexual intercourse during pregnancy and the puerperium should become part of pregnant women's education.     

Association of delay to first intervention with return of spontaneous circulation in a swine model of cardiac arrest

OBJECTIVE: No single drug improves survival after cardiac arrest, despite success in animal studies. We sought to determine the duration of circulatory arrest after which maximal drug treatment and a rescue shock would fail to achieve return of spontaneous circulation (ROSC). DESIGN/SUBJECTS: Retrospective analysis of 271 swine (20-30 kg) resuscitation attempts during ventricular fibrillation. Protocols were divided into five categories: immediate countershock, cardiopulmonary resuscitation (CPR) with standard-dose drugs, CPR alone, CPR and high-dose epinephrine (CPR+HDE) (0.1 mg/kg), and CPR with a drug cocktail (CPR+DC) of propanolol (1 mg), epinephrine (adrenaline) (0.1 mg/kg) and vasopressin (40IU). Time to first CPR, time to first drug administration, time to first shock, and protocol were examined as predictors of ROSC using logistic regression with Hosmer-Lemeshow test of fit. Probability of ROSC was calculated from logistic curves. MAIN RESULTS: ROSC occurred in 119 of the 271 swine (44%). Time to first drug and the CPR+DC group were predictors of ROSC. Time to first CPR, the CPR+DC group, and the CPR+HDE group were also predictors of ROSC. Time to first rescue shock, the CPR+DC group, and the CPR+HDE groups were predictors of ROSC. In the CPR+DC group, 50% ROSC occurred at a first CPR time of 13.4 min, first drug time of 14.1 min and first rescue shock time of 17.5 min. CONCLUSIONS: Pre-shock delivery of CPR+DC increases the likelihood of ROSC, and reaches 50% with a time of drug delivery of 14.1 min. ROSC rates of 50% may be achievable using an optimized resuscitation in experimental CPR.     

Early coronary revascularization improves 24 h survival and neurological function after ischemic cardiac arrest. A randomized animal study

Background

Survival after out-of-hospital cardiac arrest (OHCA) remains poor. Acute coronary obstruction is a major cause of OHCA. We hypothesize that early coronary reperfusion will improve 24 h-survival and neurological outcomes.

Methods

Total occlusion of the mid LAD was induced by balloon inflation in 27 pigs. After 5 min, VF was induced and left untreated for 8 min. If return of spontaneous circulation (ROSC) was achieved within 15 min (21/27 animals) of cardiopulmonary resuscitation (CPR), animals were randomized to a total of either 45 min (group A) or 4 h (group B) of LAD occlusion. Animals without ROSC after 15 min of CPR were classified as refractory VF (group C). In those pigs, CPR was continued up to 45 min of total LAD occlusion at which point reperfusion was achieved. CPR was continued until ROSC or another 10 min of CPR had been performed. Primary endpoints for groups A and B were 24-h survival and cerebral performance category (CPC). Primary endpoint for group C was ROSC before or after reperfusion.

Results

Early compared to late reperfusion improved survival (10/11 versus 4/10, p = 0.02), mean CPC (1.4 ± 0.7 versus 2.5 ± 0.6, p = 0.017), LVEF (43 ± 13 versus 32 ± 9%, p = 0.01), troponin I (37 ± 28 versus 99 ± 12, p = 0.005) and CK-MB (11 ± 4 versus 20.1 ± 5, p = 0.031) at 24-h after ROSC. ROSC was achieved in 4/6 animals only after reperfusion in group C.

Conclusions

Early reperfusion after ischemic cardiac arrest improved 24 h survival rate and neurological function. In animals with refractory VF, reperfusion was necessary to achieve ROSC.