Researchers from the Iberian-American Paediatric Cardiac Arrest Study Network challenge the evidence base behind defibrillation shock dose recommendations in children.
In a study of in-hospital pediatric cardiac arrest due to VT or VF, clinical outcome was not related to the cause or location of arrest, type of defibrillator and waveform, energy dose per shock, number of shocks, or cumulative energy dose, although there was a trend to better survival with higher doses per shock. 50% of children required more than the recommended 4J per kg and in over a quarter three or more shocks were needed to achieve defibrillation.
OBJECTIVE: To analyze the results of cardiopulmonary resuscitation (CPR) that included defibrillation during in-hospital cardiac arrest (IH-CA) in children.
METHODS: A prospective multicenter, international, observational study on pediatric IH-CA in 12 European and Latin American countries, during 24 months. Data from 502 children between 1 month and 18 years were collected using the Utstein template. Patients with a shockable rhythm that was treated by electric shock(s) were included. The primary endpoint was survival at hospital discharge. Univariate logistic regression analysis was performed to find outcome factors.
RESULTS: Forty events in 37 children (mean age 48 months, IQR: 7-15 months) were analyzed. An underlying disease was present in 81.1% of cases and 24.3% had a previous CA. The main cause of arrest was a cardiac disease (56.8%). In 17 episodes (42.5%) ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT) was the first documented rhythm, and in 23 (57.5%) it developed during CPR efforts. In 11 patients (27.5%) three or more shocks were needed to achieve defibrillation. Return of spontaneous circulation (ROSC) was obtained in 25 cases (62.5%), that was sustained in 20 (50.0%); however only 12 children (32.4%) survived to hospital discharge. Children with VF/pVT as first documented rhythm had better sustained ROSC (64.7% vs. 39.1%, p=0.046) and survival to hospital discharge rates (58.8% vs. 21.7%, p=0.02) than those with subsequent VF/pVT. Survival rate was inversely related to duration of CPR. Clinical outcome was not related to the cause or location of arrest, type of defibrillator and waveform, energy dose per shock, number of shocks, or cumulative energy dose, although there was a trend to better survival with higher doses per shock (25.0% with <2Jkg(-1), 43.4% with 2-4Jkg(-1) and 50.0% with >4Jkg(-1)) and worse with higher number of shocks and cumulative energy dose.
CONCLUSION: The termination of pediatric VF/pVT in the IH-CA setting is achieved in a low percentage of instances with one electrical shock at 4Jkg(-1). When VF/pVT is the first documented rhythm, the results of defibrillation are better than in the case of subsequent VF/pVT. No clear relationship between defibrillation protocol and ROSC or survival has been observed. The optimal pediatric defibrillation dose remains to be determined; therefore current resuscitation guidelines cannot be considered evidence-based, and additional research is needed.
Some patients with severe refractory heart failure are kept alive thanks to implantable pumps such as the left ventricular assist device (LVAD). Many emergency physicians are likely to be unfamiliar with these but could encounter patients who have them. One particular peculiarity is that latter generation devices maintain non-pulsatile flow and provide or assist cardiac output independent of cardiac rhythm. In extreme situations patients can have life-sustaining cardiac outputs without palpable pulses or even audible heart sounds.
A great example of how weird this can get is provided by a case of a 66 year male with an LVAD (HeartMate II (Thoratec Corporation)) who presented due to spontaneous discharge of his internal cardioverter-defibrillator (ICD). He was alert but had no pulses, and no detectable blood pressure using both a manual sphygmomanometer and an automated non-invasive blood pressure device. His 12 lead showed ventricular fibrillation. An invasive blood pressure showed a mean arterial pressure (mAP) of 80 mmHg. Several hours later his VF was successfully terminated and his mAP remained 80 mmHg
Some interesting points made by the authors include:
CPR was unnecessary in this guy but in cases of severe RV dysfunction it might need to be done to provide flow into the LV.
A danger of CPR in patients with an LVAD is the risk of damage to the device or ventricular rupture
LVAD use is significantly increasing so we can expect to encounter more episodes of previously impossible presentations to our emergency departments.
Optimal medical treatment, cardiac resynchronization, and the use of an implantable cardioverter defibrillator are established therapies of severe congestive heart failure. In refractory cases, left ventricular assist devices are more and more used not only as bridging to cardiac transplantation but also as destination therapy. Ventricular arrhythmias may represent a life-threatening condition and often result in clinical deterioration in patients with congestive heart failure. We report a case of asymptomatic sustained ventricular fibrillation with preserved hemodynamics caused by a nonpulsatile left ventricular assist device. Consecutive adequate but unsuccessful discharges of the implantable cardioverter defibrillator were the only sign of the usually fatal arrhythmia, prompting the patient to consult emergency services. Electrolyte supplementation and initiation of therapy with amiodarone followed by external defibrillation resulted in successful restoration of a stable cardiac rhythm after 3.5 hours.
Should we shock with 2J/kg or 4J/kg in Paediatric Defibrillation? The answer seems to be ‘we still don’t know’. Don’t worry – just follow the guidelines (reproduced for you at the bottom) OBJECTIVE To examine the effectiveness of initial defibrillation attempts. We hypothesized that (1) an initial shock dose of 2 ± 10 J/kg would be less effective for terminating fibrillation than suggested in published historical data and (2) a 4 J/kg shock dose would be more effective. PATIENTS AND METHODS This was a National Registry of Cardiopulmonary Resuscitation prospective, multisite, observational study of in-hospital pediatric (aged 18 years) ventricular fibrillation or pulseless ventricular tachycardia cardiac arrests from 2000–2008. Termination of ventricular fibrillation or pulseless ventricular tachycardia and event survival after initial shocks of 2 J/kg were compared with historic controls and a 4 J/kg shock dose.
RESULTS Of 266 children with 285 events, 173 of 285 (61%) survived the event and 61 of 266 (23%) survived to discharge. Termination of fibrillation after initial shock was achieved for 152 of 285 (53%) events. Termination of fibrillation with 2 ± 10 J/kg was much less frequent than that seen among historic control subjects (56% vs 91%; P < .001), but not different than 4 J/kg. Compared with 2 J/kg, an initial shock dose of 4 J/kg was associated with lower rates of return of spontaneous circulation (odds ratio: 0.41 [95% confidence interval: 0.21–0.81]) and event survival (odds ratio: 0.42 [95% confidence interval: 0.18–0.98]). CONCLUSIONS The currently recommended 2 J/kg initial shock dose for in-hospital cardiac arrest was substantially less effective than previously published. A higher initial shock dose (4 J/kg) was not associated with superior termination of ventricular fibrillation or pulseless ventricular tachycardia or improved survival rates. The optimal pediatric defibrillation dose remains unknown. Effect of defibrillation energy dose during in-hospital pediatric cardiac arrest Pediatrics. 2011 Jan;127(1):e16-23
Here’s what the guidelines say: Many AEDs have high specificity in recognizing pediatric shockable rhythms, and some are equipped to decrease (or attenuate) the delivered energy to make them suitable for infants and children <8 years of age. For infants a manual defibrillator is preferred when a shockable rhythm is identified by a trained healthcare provider (Class IIb, LOE C). The recommended first energy dose for defibrillation is 2 J/kg. If a second dose is required, it should be doubled to 4 J/kg. If a manual defibrillator is not available, an AED equipped with a pediatric attenuator is preferred for infants. An AED with a pediatric attenuator is also preferred for children <8 year of age. If neither is available, an AED without a dose attenuator may be used (Class IIb, LOE C). AEDs that deliver relatively high energy doses have been successfully used in infants with minimal myocardial damage and good neurological outcomes Pediatric Basic Life Support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Full text document
From the new 2010 resuscitation guidelines:
For attempted defibrillation of children 1 to 8 years of age with an AED, the rescuer should use a pediatric dose-attenuator system if one is available. If the rescuer provides CPR to a child in cardiac arrest and does not have an AED with a pediatric dose-attenuator system, the rescuer should use a standard AED. For infants (<1 year of age), a manual defibrillator is preferred. If a manual defibrillator is not available, an AED with pediatric dose attenuation is desirable. If neither is available, an AED without a dose attenuator may be used.
One of the key changes in international resuscitation guidelines between the 2000 and 2005 has been to minimise potentially deleterious hands-off time, so that CPR is interrupted less for pulse checks and DC shocks.
These two approaches have been compared in a randomised controlled trial of 845 patients in France requiring out of hospital defibrillation, in which the control group were shocked using AEDs with prompts based on the 2000 guidelines (3 stacked shocks before CPR resumed, and pulse checks done), and the intervention group were shocked using devices that prompted according to the 2005 guidelines, in which there were fewer and shorter intervals for which the AED required the rescuer to stay clear of the patient (single shocks, no pulse checks).
There was no difference in the primary endpoint of survival to hospital admission (43.2% versus 42.7%; p=0.87), or in survival to hospital discharge (13.3% versus 10.6%; p=0.19). The study was not powered to assess one year survival. In the authors’ words: “our randomized controlled trial now provides more definitive evidence that this combination of Guidelines 2005 CPR protocol changes does not measurably improve outcome. Although the protocol changes accomplish the desired effect of increasing chest compressions, they may also cause other effects, such as earlier refibrillation and more time spent in VF, with as yet unknown consequences.”
Interestingly the Cardio-pump was used in this study to provide chest compressions, which is an active compression-decompression device, potentially limiting the generalisability of the findings to manual compression-only CPR situations. Potential bias was also introduced by the exclusion of patients in whom consent from relatives was not obtained. Nevertheless it’s good to see such rigorous clinical research applied to this area. DEFI 2005. A Randomized Controlled Trial of the Effect of Automated External Defibrillator Cardiopulmonary Resuscitation Protocol on Outcome From Out-of-Hospital Cardiac Arrest Circulation. 2010;121:1614-1622
No rescuer or bystander has ever been seriously harmed by receiving an inadvertent shock while in direct or indirect contact with a patient during deﬁbrillation. New evidence suggests that it might even be electrically safe for the rescuer to continue chest compressions during deﬁbrillation if self-adhesive deﬁbrillation electrodes are used and examination gloves are worn. This paper reviews the existing evidence, but warns more deﬁnite data are needed to make absolutely sure that there is no risk before deﬁbrillation safety recommendations are changed.
A blanket made of nonconducting material was used to allow CPR to continue during defibrillation of arrested swine. Coronary perfusion pressure was maintained when the blanket was used
but fell when there was a hands-off interruption for defibrillation. Also, the defibrillation threshold was significantly lower when the blanket was used. A good idea, although even the authors point out that “Thus far, medical literature has not reported any rescuer or bystander serious injury from receiving an inadvertent shock while in direct or indirect contact with a patient while performing CPR“ The resuscitation blanket: A useful tool for “hands-on” defibrillation Resuscitation. 2010 Feb;81(2):230-23
No rescuer or bystander has ever been seriously harmed by receiving an inadvertent shock while in direct or indirect contact with a patient during deﬁbrillation. New evidence suggests that it might even be electrically safe for the rescuer to continue chest compressions during deﬁbrillation if self-adhesive deﬁbrillation electrodes are used and examination gloves are worn. This paper reviews the existing evidence, but warns more deﬁnite data are needed to make absolutely sure that there is no risk before deﬁbrillation safety recommendations are changed. Is external defibrillation an electric threat for bystanders? Resuscitation. 2009 Apr;80(4):395-401