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Three Part Question

In [patients who go into VF post-cardiac surgery], what is the success rate of each subsequent [defibrillatory shock] to return [cardiac output]?

Clinical Scenario

A 78-year-old patient has returned to your intensive care following a quadruple coronary arterial bypass graft. The operation note states that the targets were very small and there is some lateral ST segment elevation on the monitor. One hour post-surgery he suddenly goes into ventricular fibrillation. The nurses start to massage the patient. You place external pads on the patient and deliver a single 150 J biphasic shock which is unsuccessful. You start to charge for a second shock but the nurses who have just gone on a resuscitation update course recommence cardiac massage and tell you that he needs 2 min of massage. You are aware that a graft may be kinked or occluded or there may be a tamponade and, thus, do not want to delay reopening, but to not want to reopen after a single failed shock, and later resolve to look up how many shocks we should perform prior to reopening.

Search Strategy

Medline 1950 to August 2007 using OVID Interface.
[exp cardiac surgical procedures/OR exp thoracic surgical procedures/OR exp thoracic surgery/] AND [exp ventricular fibrillation/OR exp Tachycardia, Ventricular/] AND [exp Electric Countershock/OR Heart Arrest/OR exp Cardiopulmonary Resuscitation/]. Embase 1980 to August 2007 [exp Heart sugery/OR exp Thorax Surgery] AND [exp heart ventricle Fibrillation/OR exp Heart Ventricle Tachycardia/] AND [exp heart arrest/OR exp resuscitation/OR exp cardioversion/]. All references searched from Section 2 and 3 of the European Resuscitation Council Guidelines for Resuscitation 2005
Cochrane Database of Systematic reviews was searched on 28th of August 2007 using the search term 'resuscitation' searched. Cochrane Controlled Trials register searched on 28th of August 2007 using the search term 'resuscitation'.

Search Outcome

Four hundred and eighty-six abstracts were identified from Medline, 352 abstracts from Embase, 28 papers from the Cochrane database of systematic reviews and 155 from the Cochrane controlled trials register. There were 162 references in sections 2 and 3 of the ERC guidelines. From these studies, 15 represented the best evidence on the topic

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Szili-Torok et al, 2002, The Netherlands	14 patients with ICD's (mean age 63±14 yrs) were randomised into two groups of different transthoracic defibrillation. 50 episodes of VF, with mean duration of 13±3.4s analysed. 27 episodes received a sequence of 100J then 200J biphasic rectilnear shocks, 23 treated with a sequence of 150 then 360J monophasic damped sine shocks.	Prospective randomised controlled trial.( Level 2, Good)	First shock efficacy	92% with 100J biphasic shock (25 episodes). 61% with 150J monophasic shock (14 episodes).	Small patient group. Few patients to compare for the second shock efficacy. Patients had either coronary artery disease or cardiomyopathy and were not post-surgical.
			Second shock efficacy	100% with 200J biphasic shock (2 episodes). 95% with 360J monophasic shock (4 episodes).
			Most effective waveform for first and second shocks.	Low-energy biphasic shocks. Overall success rate of: Biphasic shocks: 93% Monophasic shocks: 64%
Higgens et al, 2004, USA	96 patients (mean age 70±10 yrs). 77 in VF for mean of 16±5s and 19 in ventricular tachycardia. VF/VT electrically induced in patients undergoing EP testing or testing for ICD. First shock efficacy of 150J biphasic shocks delivered to VF patients evaluated and compared to historical control group (68 patients, mean age 69±12 yrs, in VF for mean 19±9s,) treated with 200J monophasic shock.	Prospective cohort study. (level 3, Good)	First shock efficacy - for VF.	97.4% with 150J biphasic shock (75/77). 89.7% with 200J monophasic shock (61/68).	ICD patients received shock from ICD as primary shock, whereas, EP group received the biphasic shock as primary shock. Patients who received biphasic shock were compared to a patient group not selected in the same time period. A range of post-shock rhythms were accepted as reversion from VF. Patients are not post-surgical and their VF is induced rather than spontaneous.
			Second shock efficacy – for VF.	100% with 150J biphasic shock (2/2).
			Most effective waveform	150J biphasic shocks are equivalent to monophasic.
Steill et al, 2007, Canada	The BIPHASIC study 3 year study involving 221 out-of-hospital cardiac arrest patients received 1 or more biphasic shocks from AED¡¯s that were randomly programmed to give fixed lower energy (114 patients) (150-150-150J) or escalating higher energy (107 patients) (200-300-360J) regimes. Initial rhythm in 92.3% was VT/VF, 206 were in VF. Mean age of patients 66 yrs.	Randomised, triple-blinded controlled trial (Level 1, Good)	Efficacy of fixed lower versus escalating higher shocks.	Multiple shocks (¡Ý2): 106 patients. Overall VF termination rate for multiple shocks: Fixed lower: 71.2% (51 patients). Escalating higher: 82.5% (55 patients).	Out of hospital cardiac arrest only, excluded patients who suffered cardiac arrest in hospital. Patients are not post-surgical. Does not specify success of second/third shock, instead it gives an overall success of multiple-shock patients.
			First shock success of VF termination within 5s.	1 shock only: 103 patients. Fixed lower (150J): 86.8% Escalating higher (200J): 88.8%
Morrison et al, 2005, Canada	The ORBIT Study AED's were randomised to produce biphasic (RLB) shocks (120-150-200J) or monophasic damped sine (MDS) (200-300-360J). 313 patients in cohort, of which 169 had initially shockable rhythm and 144 were not initially shockable. Of the 212 patients, 83 received MDS and 86 RLB.	Prospective randomised controlled trial. (level 1, Excellent)	Shock success (conversion at 5 s to an organised rhythm) for First shock.	RLB: 22.9% (19/83) MDS: 12.2% (10/82)	Patients shocked regardless of arrest rhythm. Out-of-hospital patients. Non-surgical patients.
			Second shock	RLB: 26.9% (18/67) MDS: 21.9% (16/73)
			Third shock.	RLB: 16.3% (8/49) MDS: 3.5% (2/57)
Martens et al, 2001, Belgium	338 out-of-hospital cardiac arrests. 115 presented with VF with mean age of 65 yrs. AED's were randomly assigned either impedance-compensated biphasic truncated exponential (ICBTE) (150-150-150J) or monophasic truncated exponential (MTE)/monophasic damped sine (MDS) (200-200-360J).	Randomised controlled trial.( Level 1, Good)	Defibrillation efficacy (VF termination for at least 5s) with: less than or equal to 3 shocks.	Biphasic: 98% (53/54) MTE: 67% (32/48) MDS: 77% (10/13)	Out-of-hospital patients only. Small patient group (115). Non-surgical patients.
			less than or equal to 2 shocks	Biphasic: 96% (52/54) MTE: 60% (29/48) MDS: 77% (10/13)
			First shock	Biphasic: 96% (52/54) MTE: 54% (26/48) MDS: 77% (10/13)
			Kruskal-Wallis test	Direct comparison between ICBTE and MDS show biphasic shocks have significantly greater shock efficacy for 1/2/3 shocks (p<0.05).
Schwartz et al, 2003, Austria	Study between Feb 2000 and Jan 2001. 91 patients (mean age 66.5 yrs) undergoing cardiac surgery were randomly assigned to either a control group that received monophasic damped sine wave shocks (41) or treatment group that received biphasic truncated exponential waveform shocks (50) intra-operatively if they entered VF. Each group received ascending shock energies (2, 5, 7, 10 and 20J) until defibrillation occurred. Surgeon blinded to shock waveform.	Prospective randomised controlled trial. (level 2,Good)	Cumulative % success at shock strength: 1st shock (2J)	Monophasic: 7.3% Biphasic: 16.7%	Does not focus on the number of shocks, but rather the waveform of the shock delivered. Patients are undergoing surgery rather than post-surgical. Shock delivery is intra-operative rather than transthoracic. Removal of aortic clamp was trigger for VF, rather than spontaneous VF. Results not specific to one operation, but 4 different cardiac procedures.
			2nd shock (5J)	Monophasic: 22.0% (9/41) Biphasic: 52.1% (25/50)
			3rd Shock (7J)	Monophasic: 34.1% Biphasic: 66.7%
			4th Shock (10J)	Monophasic: 51.2% Biphasic: 75.0%
			5th shock (20J)	vMonophasic: 75.6% Biphasic: 83.3%
Edelson et al, 2006, USA	Study conducted between March 2002 and Dec 2005. 60 in-hospital and out-of-hospital patients (mean age 65±16yrs) who entered VF were delivered a trans-thoracic biphasic shock with variable compression depth and pre-shock pause.	Prospective multi-centre cohort study ( Level 2, Good)	First shock success (removal of VF for at least 5 s)	73% (44) (with 8s pre-shock pause).	Focus on pre-shock pause (time between last chest compression and first shock), compression depth and other factors affecting first shock success. Includes both in- and out-of-hospital arrests therefore a single conclusion from one group cannot be determined. Low patient number to draw significant conclusions from.
			Optimal pre-shock pause and compression depth.	Longer pre-shock pause and shallower compression depth associated with significantly decreased first shock success.
van Alem et al, 2003, The Netherlands	Study between Jan 2000 and June 2002. 120 out-of-hospital patients (mean age 66.5 yrs) who entered VF received either a biphasic truncated exponential shock (BTE) or monophasic damped sine shock (MDS) of 200J. AED's (identical in shape, size and design) programmed for BTE or MDS were randomly assigned to responders. 51 patients received BTE and 69 received MDS. Second and third shocks were 200 and 360J for both BTE and MDS protocols.	Prospective randomised double blinded trial. ( Level 2, Good )	First shock success (removal of VF and return of organised rhythm for at least 2 QRS complexes within 1min).	Biphasic: 69% (35/51) Monophasic: 45% (31/69)	Out-of-hospital cardiac arrests included, no in-hospital patients. Lack of data on subsequent shocks delivered to those patients in whom the first shock failed and VF persisted.
			Termination of VF at 5s after 1st shock.	Biphasic: 98% (50/51) Monophasic: 91% (63/69)
Carpenter et al, 2003, USA	Study between Jan 1999 and Aug 2002. 366 out-of-hospital cardiac arrest patients presenting in VF received either a monophasic damped sine (MDS) shock (193 patients, mean age 67yrs), biphasic truncated exponential (BTE) shock (105 patients, mean age 67yrs) or monophasic truncated exponential (MTE) shock (68 patients, mean age 64yrs) .	Retrospective cohort study. ( Level 4, Excellent)	First shock success (removal of organised rhythm and minimum of 2 QRS complexes within 5s of shock)	MDS: 83.9% (162/193) MTE: 63.2% (43/68) BTE: 89.5% (94/105)	The study is not a randomised controlled trial. Pre-hospital setting only, no patients in-hospital or post-surgical. Cumulative data only regarding second and third shock success.
			less than or equal to 2 shocks	MDS: 92.2% (178/193) n= 16 MTE: 75.0% (51/68) BTE: 96.2% (101/105)
			less than or equal to 3 shocks	MDS: 95.9% (185/193) MTE: 85.3% (58/68) BTE: 97.1% (102/105)
Cammarata et al, 2006, USA	In 60 domestic pigs, VF was electrically induced, 1 min CPR delivered followed by up to 3 sequential 150J biphasic shocks.	Experimental study. (Level 6, Excellent)	First shock success (restoration of spontaneous circulation).	80% (48/60)	Study limited to pigs, therefore, cannot be directly applied to humans. Absence of ischaemic heart disease in the pigs.
			Second shock success	15% (9/60) Reduced capability to restore spontaneous circulation due to time required to for rhythm analysis and recharging AED.
			Third shock success	5% (3/60) As above
			Resuscitation protocol	To deliver a single shock or at most 2 shocks prior to resuming chest compressions.
Nieman et al, 2000, USA	In 38 pigs, VF was induced for 5 min, after which, 18 received monophasic truncated exponential (MTE) shocks (200-300-360J) and 20 received biphasic truncated exponential (BTE) shocks (150-150-150J). 5 pigs, 3 from BTE and 2 from MTE groups required more than 3 shocks.	Experimental study. (level 6, Excellent)	Successful defibrillation (termination of VF regardless of post-shock rhythm) at First shock	MTE: 61% (11/18) BTE: 50% (10/20)	Pigs were in VF for 5 minutes, which is unlikely in patients on CICU, but more likely in out-of-hospital arrests. Unable to base practice on studies involving pigs. Small number of pigs in the study. VF induced rather than spontaneous. Post-shock rhythm not recorded.
			Second shock	MTE: 22% (4/18) BTE: 30% (6/20)
			Third shock	MTE: 0 BTE: 5% (1/20)
Schneider et al, 2000, Germany	115 out-of-hospital cardiac arrest patients who presented in VF received either 150-150-150J biphasic shocks (54 patients, mean age 67±13yrs) or 200-200-360J monophasic shocks (61 patients, mean age 66±14yrs) from an AED previously randomly assigned to either waveform.	Multi-centre randomised controlled trials. (level 1, Good)	Defibrillation (termination of VF for greater than or equal to 5s) in the first series of less than or equal to 3 shocks.	Monophasic: 69% (42/61) Biphasic: 98% (53/54)	Out-of-hospital cardiac arrests. Variable causes of arrests. Small patient group. Discontinuous AED user including flight attendants and police officers, therefore variation in expertise. Out-of-hospital patients only. Variation in the time between arrest and application of pads and subsequent first shock delivery. Patients undergoing ICD surgery, ICD replacement, or ICD testing. Patients first received a transvenous shock which if unsuccessful was followed by a transthoracic shock. Induced VF as opposed to spontaneous therefore shorter interval between start of VF and first shock compared to in-hospital patients. Patients included who presented in VT as well as VF, therefore not a complete reflection of in-hospital cardiac arrests. Shock considered successful if 5s post-shock, the rhythm was non-shockable, (includes asystole), and therefore shock success is not reversion to sinus rhythm.
			Defibrillation with less than or equal to 2 shocks.	Monophasic: 64% (39/61) Biphasic: 96% (52/54)
			Defibrillation with 1 shock.	Monophasic: 59% (36/61) Biphasic: 96% (52/54)
			Total patients defibrillated.	Monophasic: 84% (49/58) Biphasic: 100% (54/54)

Comment(s)

Current guidelines from the European Resuscitation Council state that 2 min should be left between attempts at cardioversion for patients who arrest and go into ventricular fibrillation or ventricular tachycardia (VF/VT). But in patients post-cardiac surgery, prompt chest reopening is known to improve outcomes, thus, waiting for 2 min between each shock may result in a delay that may impair outcome should cardioversion prove unsuccessful. Therefore, having a protocol for the number of attempts at defibrillation prior to reopening the chest is of paramount importance. In eight studies, monophasic shocks were compared to biphasic shocks, and in all these papers, biphasic shocks were found to be more successful or equivalent to monophasic shocks at defibrillation. In five of these comparative studies, the success at the first attempt at defibrillation was between 86 and 98%. In contrast, two of the studies [8, 9] showed relatively lower first shock success rates ranging from 16.7 to 22.9%. However, in one of the latter studies by Schwartz et al., intra-operative shocks were delivered during cardiac surgery on 91 patients, therefore, the first shock energy was lower at 2 J compared to the higher energies (100–150 J) used for the transthoracic delivery in the other studies. Two animal studies were performed. Cammarata et al. induced VF in 60 pigs, then delivered three sequential 150 J biphasic shocks. The first shock success was 80%, which steeply declined to 15% success for the second shock and further dropped to 5% for the third shock success. These results strongly suggest that a maximum of three shocks should be delivered to patients in VF/VT, as after this point, the chance of successful defibrillation is very small. The second study was by Nieman et al., who induced VF in 38 pigs, who either received three escalating monophasic shocks (200-300-360 J) or fixed biphasic shocks (150 J). Both shock waveforms displayed a similar reduction in shock success from first to third shocks. The first shock success was 50% for biphasic shocks, followed by 30% for second shock and 5% at third shock. The results of both papers suggest that the fourth shock success would be below 5%. These animal studies have the obvious limitation of involving pigs as the subjects, however, in combination (98 pigs) the similar pattern of reduction from first to third shock success indicates that proceeding to a fourth shock would not be beneficial to patients in VF. Of course we must acknowledge the wide range of papers from which we obtained these data, including papers looking at ICDs, electrophysiological studies, all the way to out-of-hospital arrests and animal studies and we must furthermore acknowledge that the success of a second shock after 2 min of CPR has not yet been reported in any paper that we found. However, when the data are combined from all 15 papers, although not all record the second and third shock success, the average success rate of sequential shocks declines from 77.6% for the first shock, 34.8% for the second shock and to 13.9% for third shock success. Data on fourth shock success was only recorded in one paper. Overall, the data suggest that the likelihood of conversion from VF/VT to an organised rhythm declines dramatically from first to second shock, and declines further from second to third shock, which indicates that proceeding to reopening after the third shock is preferable due to the minimal chance of fourth shock success. Mackay et al. reported the results of 79 chest reopenings over six years and found that the major determinant of survival was chest reopening within 10 min.

Clinical Bottom Line

We conclude that due to the importance of minimising the delay to chest reopening, three shocks should be quickly delivered. If these do not succeed the chance of a 4th shock succeeding is likely to be less than 10% and, thus, immediate chest reopening should be performed. (This is a Class-IIa recommendation using ILCOR guideline recommendations.)

References

1. Handley AJ, Koster R, Monsieurs K et al. European Resuscitation Council Guidelines for Resuscitation 2005: Section 2: adult basic life support and use of automated external defibrillators. Resuscitation 2005; 67S1:S7–23.
2. Deakin CD, Nolan JP. European Resuscitation Council Guidelines for Resuscitation 2005: Section 3 Electrical therapies: automated external defibrillators, defibrillation, cardioversion and pacing. Resuscitation 2005; 67S1:S25–37.
3. Szili-Torok T, Theuns D, Verblaauw T et al. Transthoracic defibrillation of short-lasting ventricular fibrillation: a randomised trial for comparison of the efficacy of low-energy biphasic rectilinear and monophasic damped sine shocks. Acta Cardiologica 2002; 57:329–334.
4. Higgins SL, O'Grady SG, Banville I et al. Efficacy of lower-energy biphasic shocks for transthoracic defibrillation: a follow-up clinical study. Prehospital Emergency Care 2004; 8:262–267.
5. Steill IG, Walker RG, Nesbitt LP et al. BIPHASIC Trial: a randomised comparison of fixed lower versus escalating higher energy levels for defibrillation in out-of-hospital cardiac arrest. Circulation 2007; 115:1511¨C1517.
6. Morrison LJ, Dorian P, Long J et al. Out-of-hospital cardiac arrest rectilinear biphasic to monophasic damped sine defibrillation waveforms with advanced life support intervention trial (ORBIT). Resuscitation 2005; 66:149–157.
7. Martens PR, Russell JK, Wolcke B et al. Optimal response to cardiac arrest study: defibrillation waveform effects. Resuscitation 2001; 49:233¨C243.
8. Schwartz B, Bowdle A, Jett K et al. Biphasic shocks compared with monophasic damped sine wave shocks for direct ventricular defibrillation during open-heart surgery. Anesthesiology 2003; 98:1063–1069.
9. Edelson DP, Abella BS, Kramer-Johansen J et al. Effects of compression depth and pre-shock pause predict defibrillation failure during cardiac arrest. Resuscitation 2006; 71:137–145.
10. van Alem AP, Chapman FW, Lank P et al. A prospective randomised and blinded comparison of first shock success of monophasic and bisphasic waveforms in out-of-hospital cardiac arrest. Resuscitation 2003; 58:17–24.
11. Carpenter J, Rea TD, Murray JA et al. Defibrillation waveform and post-shock rhythm in out-of-hospital ventricular fibrillation cardiac arrest. Resuscitation 2003; 59:189¨C196.
12. Cammarata G, Weil MH, Csapoczi P et al. Challenging the rationale of three sequential shocks for defibrillation. Resuscitation 2006; 69:23–27.
13. Nieman JT, Burian D, Garner D et al. Monophasic versus biphasic transthoracic countershock after prolonged ventricular fibrillation in a swine model. J Am Coll Cardiol 2000; 36:932–938.
14. Schneider T, Martens PR, Paschen H et al. Multicentre, randomised controlled trial of 150J biphasic shocks compared with 200- to 360J monophasic shocks in the resuscitation of out-of-hospital cardiac arrest victims. Circulation 2000; 102:1780¨C1787.
15. Gliner BE, Jorgenson DB, Poole JE et al. Treatment of out-of-hospital cardiac arrest with a low-energy impedance-compensating biphasic waveform automatic external defibrillator. Biochemical Instrumentation and Technology 1998; 32:631–644.
16. Bardy GH, Marchlinski FE, Sharma AD et al. Multicenter comparison of truncated biphasic shocks and standard damped sine wave monophasic shocks for transthoracic ventricular defibrillation. Circulation 1996; 94:2507–2514.
17. White R, Blackwell TH, Russell JK et al. Transthoracic impedance does not affect defibrillation, resuscitation or survival in patients with out-of-hospital cardiac arrest treated with a non-escalating biphasic waveform defibrillator. Resuscitation 2005; 64:63–69.
18. Mackay JH, Powell SJ, Osgathorp J et al. Six-year prospective audit of chest reopening after cardiac arrest. Eur J Cardiothorac Surg 2002; 22:421–425.
19. Morley PT, Zaritsky A. The evidence evaluation process for the 2005 International Consensus Conference on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations. Resuscitation 2005; 67:167–170.