European Resuscitation Council Guidelines for Resuscitation ... - CPR

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18 de 0ctubre de 2010 www.elsuapdetodos.com1296 C.D. Deakin et al. / Resuscitation 81 (2010) 1293–1304contact. Use of bare-metal paddles alone creates high transthoracicimpedance and is likely to increase the risk of arcing and worsencutaneous burns from defibrillation.Electrode positionNo human studies have evaluated the electrode position as adeterminant of ROSC or survival from VF/VT cardiac arrest. Transmyocardialcurrent during defibrillation is likely to be maximalwhen the electrodes are placed so that the area of the heart thatis fibrillating lies directly between them (i.e. ventricles in VF/VT,atria in AF). Therefore, the optimal electrode position may not bethe same for ventricular and atrial arrhythmias.More patients are presenting with implantable medical devices(e.g., permanent pacemaker, implantable cardioverter defibrillator(ICD)). Medic Alert bracelets are recommended for these patients.These devices may be damaged during defibrillation if current isdischarged through electrodes placed directly over the device. 59,60Place the electrode away from the device (at least 8 cm) 59 or use analternative electrode position (anterior-lateral, anterior-posterior)as described below.Transdermal drug patches may prevent good electrode contact,causing arcing and burns if the electrode is placed directly over thepatch during defibrillation. 61,62 Remove medication patches andwipe the area before applying the electrode.Placement for ventricular arrhythmias and cardiac arrestPlace electrodes (either pads or paddles) in the conventionalsternal-apical position. The right (sternal) electrode is placed tothe right of the sternum, below the clavicle. The apical paddleis placed in the left mid-axillary line, approximately levelwith the V6 ECG electrode or female breast. This position shouldbe clear of any breast tissue. It is important that this electrodeis placed sufficiently laterally. Other acceptable pad positionsinclude• Placement of each electrode on the lateral chest walls, one on theright and the other on the left side (bi-axillary).• One electrode in the standard apical position and the other on theright upper back.• One electrode anteriorly, over the left precordium, and the otherelectrode posteriorly to the heart just inferior to the left scapula.It does not matter which electrode (apex/sternum) is placed ineither position.Transthoracic impedance has been shown to be minimisedwhen the apical electrode is not placed over the female breast. 63Asymmetrically shaped apical electrodes have a lower impedancewhen placed longitudinally rather than transversely. 64Placement for atrial arrhythmiasAtrial fibrillation is maintained by functional re-entry circuitsanchored in the left atrium. As the left atrium is located posteriorlyin the thorax, electrode positions that result in a moreposterior current pathway may theoretically be more effectivefor atrial arrhythmias. Although some studies have shown thatantero-posterior electrode placement is more effective than thetraditional antero-apical position in elective cardioversion of atrialfibrillation, 65,66 the majority have failed to demonstrate any clearadvantage of any specific electrode position. 67,68 Efficacy of cardioversionmay be less dependent on electrode position when usingbiphasic impedance-compensated waveforms. 56 The followingelectrode positions all appear safe and effective for cardioversionof atrial arrhythmias:• Traditional antero-apical position.• Antero-posterior position (one electrode anteriorly, over the leftprecordium, and the other electrode posteriorly to the heart justinferior to the left scapula).Respiratory phaseTransthoracic impedance varies during respiration, being minimalat end-expiration. If possible, defibrillation should beattempted at this phase of the respiratory cycle. Positive end expiratorypressure (PEEP) increases transthoracic impedance and shouldbe minimised during defibrillation. Auto-PEEP (gas trapping) maybe particularly high in asthmatics and may necessitate higher thanusual energy levels for defibrillation. 69Electrode sizeThe Association for the Advancement of Medical Instrumentationrecommends a minimum electrode size of for individualelectrodes and the sum of the electrode areas should be a minimumof 150 cm 2 . 70 Larger electrodes have lower impedance, but excessivelylarge electrodes may result in less transmyocardial currentflow. 71For adult defibrillation, both handheld paddle electrodes andself-adhesive pad electrodes 8–12 cm in diameter are used andfunction well. Defibrillation success may be higher with electrodesof 12 cm diameter compared with those of 8 cm diameter. 54,72Standard AEDs are suitable for use in children over the age of 8years. In children between 1 and 8 years use paediatric pads withan attenuator to reduce delivered energy or a paediatric mode ifthey are available; if not, use the unmodified machine, taking careto ensure that the adult pads do not overlap. Use of AEDs is notrecommended in children less than 1 year.Coupling agentsIf using manual paddles, disposable gel pads should be used toreduce impedance at the electrode–skin interface. Electrode pastesand gels can spread between the two paddles, creating the potentialfor a spark and should not be used. Do not use bare electrodes withoutgel pads because the resultant high transthoracic impedancemay impair the effectiveness of defibrillation, increase the severityof any cutaneous burns and risk arcing with subsequent fire orexplosion.www.elsuapdetodos.comPads versus paddlesSelf-adhesive defibrillation pads have practical benefits overpaddles for routine monitoring and defibrillation. 73–77 They aresafe and effective and are preferable to standard defibrillationpaddles. 72 Consideration should be given to use of self-adhesivepads in peri-arrest situations and in clinical situations wherepatient access is difficult. They have a similar transthoracicimpedance 71 (and therefore efficacy) 78,79 to manual paddles andenable the operator to defibrillate the patient from a safe distancerather than leaning over the patient as occurs with paddles. Whenused for initial monitoring of a rhythm, both pads and paddlesenable quicker delivery of the first shock compared with standardECG electrodes, but pads are quicker than paddles. 80When gel pads are used with paddles, the electrolyte gelbecomes polarised and thus is a poor conductor after defibrillation.This can cause spurious asystole that may persist for 3–4 min whenused to monitor the rhythm; a phenomenon not reported withself-adhesive pads. 74,81 When using a gel pad/paddle combinationconfirm a diagnosis of asystole with independent ECG electrodesrather than the paddles.
Fibrillation waveform analysisIt is possible to predict, with varying reliability, the success ofdefibrillation from the fibrillation waveform. 82–101 If optimal defibrillationwaveforms and the optimal timing of shock delivery canbe determined in prospective studies, it should be possible to preventthe delivery of unsuccessful high energy shocks and minimisemyocardial injury. This technology is under active developmentand investigation but current sensitivity and specificity is insufficientto enable introduction of VF waveform analysis into clinicalpractice.CPR versus defibrillation as the initial treatmentA number of studies have examined whether a period of CPRprior to defibrillation is beneficial, particularly in patients withan unwitnessed arrest or prolonged collapse without resuscitation.A review of evidence for the 2005 guidelines resulted inthe recommendation that it was reasonable for EMS personnelto give a period of about 2 min of CPR (i.e. about five cyclesat 30:2) before defibrillation in patients with prolonged collapse(>5 min). 1 This recommendation was based on clinical studieswhere response times exceeded 4–5 min, a period of 1.5–3 minof CPR by paramedics or EMS physicians before shock deliveryimproved ROSC, survival to hospital discharge 102,103 and one yearsurvival 103 for adults with out-of-hospital VF/VT compared withimmediate defibrillation. In some animal studies of VF lasting atleast 5 min, CPR before defibrillation improved haemodynamicsand survival. 103–106 A recent ischaemic swine model of cardiacarrest showed a decreased survival after pre-shock CPR. 107In contrast, two randomized controlled trials, a period of1.5–3 min of CPR by EMS personnel before defibrillation did notimprove ROSC or survival to hospital discharge in patients with outof-hospitalVF/VT, regardless of EMS response interval. 108,109 Fourother studies have also failed to demonstrate significant improvementsin overall ROSC or survival to hospital discharge with aninitial period of CPR, 102,103,110,111 although one did show a higherrate of favourable neurological outcome at 30 days and one yearafter cardiac arrest. 110The duration of collapse is frequently difficult to estimate accuratelyand there is evidence that performing chest compressionswhile retrieving and charging a defibrillator improves the probabilityof survival. 112 For these reasons, in any cardiac arrest theyhave not witnessed, EMS personnel should provide good-qualityCPR while a defibrillator is retrieved, applied and charged, but routinedelivery of a pre-specified period of CPR (e.g., 2 or 3 min) beforerhythm analysis and a shock is delivered is not recommended.Some EMS systems have already fully implemented a pre-specifiedperiod of chest compressions before defibrillation; given the lackof convincing data either supporting or refuting this strategy, it isreasonable for them to continue this practice.In hospital environments, settings with an AED on-site andavailable (including lay responders), or EMS-witnessed events,defibrillation should be performed as soon as the defibrillatoris available. Chest compressions should be performed until justbefore the defibrillation attempt (see Section 4 advanced lifesupport). 113The importance of early, uninterrupted chest compressions isemphasised throughout these guidelines. In practice, it is often difficultto ascertain the exact time of collapse and, in any case, CPRshould be started as soon as possible. The rescuer providing chestcompressions should interrupt chest compressions only for ventilations,rhythm analysis and shock delivery, and should resumechest compressions as soon as a shock is delivered. When two rescuersare present, the rescuer operating the AED should apply theelectrodes whilst CPR is in progress. Interrupt CPR only when it is18 de 0ctubre de 2010 www.elsuapdetodos.comC.D. Deakin et al. / Resuscitation 81 (2010) 1293–1304 1297necessary to assess the rhythm and deliver a shock. The AED operatorshould be prepared to deliver a shock as soon as analysis iscomplete and the shock is advised, ensuring no rescuer is in contactwith the victim.Delivery of defibrillationOne-shock versus three-stacked shock sequenceA major change in the 2005 guidelines was the recommendationto give single rather than three-stacked shocks. This was becauseanimal studies had shown that relatively short interruptions inexternal chest compression to deliver rescue breaths 114,115 or performrhythm analysis 33 were associated with post-resuscitationmyocardial dysfunction and reduced survival. Interruptions inexternal chest compression also reduced the chances of convertingVF to another rhythm. 32 Analysis of CPR performance during outof-hospital34,116 and in-hospital 35 cardiac arrest also showed thatsignificant interruptions were common, with chest compressionscomprising no more than 51–76% 34,35 of total CPR time.With first shock efficacy of biphasic waveforms generallyexceeding 90%, 117–120 failure to cardiovert VF successfully is morelikely to suggest the need for a period of CPR rather than a furthershock. Even if the defibrillation attempt is successful in restoring aperfusing rhythm, it is very rare for a pulse to be palpable immediatelyafter defibrillation and the delay in trying to palpate a pulsewill further compromise the myocardium if a perfusing rhythm hasnot been restored. 40Subsequent studies have shown a significantly lower handsoff-ratiowith the one-shock protocol 121 and some, 41,122,123 butnot all, 121,124 have suggested a significant survival benefit fromthis single-shock strategy. However, all studies except one 124 werebefore-after studies and all introduced multiple changes in the protocol,making it difficult to attribute a possible survival benefit toone of the changes.When defibrillation is warranted, give a single shock and resumechest compressions immediately following the shock. Do not delayCPR for rhythm reanalysis or a pulse check immediately after ashock. Continue CPR (30 compressions:2 ventilations) for 2 minuntil rhythm reanalysis is undertaken and another shock given (ifindicated) (see Section 4 advanced life support). 113 This singleshockstrategy is applicable to both monophasic and biphasicdefibrillators.If VF/VT occurs during cardiac catheterisation or in the earlypost-operative period following cardiac surgery (when chest compressionscould disrupt vascular sutures), consider delivering upto three-stacked shocks before starting chest compressions (seeSection 8 special circumstances). 125 This three-shock strategy mayalso be considered for an initial, witnessed VF/VT cardiac arrest ifthe patient is already connected to a manual defibrillator. Althoughthere are no data supporting a three-shock strategy in any of thesecircumstances, it is unlikely that chest compressions will improvethe already very high chance of return of spontaneous circulationwhen defibrillation occurs early in the electrical phase, immediatelyafter onset of VF.www.elsuapdetodos.comWaveformsHistorically, defibrillators delivering a monophasic pulse hadbeen the standard of care until the 1990s. Monophasic defibrillatorsdeliver current that is unipolar (i.e. one direction of current flow)(Fig. 3.1). Monophasic defibrillators were particularly susceptibleto waveform modification depending on transthoracic impedance.Small patients with minimal transthoracic impedance receivedconsiderably greater transmyocardial current than larger patients,
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