Timing of CPR cycles (2 min vs other) (BLS #346): Systematic Review

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This Review is a draft version prepared by ILCOR, with the purpose to allow the public to comment and is labeled “Draft for Public Comment". The comments will be considered by ILCOR. The next version will be labelled “draft" to comply with copyright rules of journals. The final Review will be published on this website once a summary article has been published in a scientific Journal and labeled as “final”.

Conflict of Interest Declaration

The ILCOR Continuous Evidence Evaluation process is guided by a rigorous ILCOR Conflict of Interest policy. The following Task Force members and other authors were recused from the discussion as they declared a conflict of interest: (none applicable)

The following Task Force members and other authors declared an intellectual conflict of interest and this was acknowledged and managed by the Task Force Chairs and Conflict of Interest committees: (none applicable)

CoSTR Citation

Hung K, Castren M, Kudenchuk P, Mancini MB, Avis S, Brooks S, Chung S, Considine J, Hatanaka T, Nishiyama C, Perkins G, Ristagno G, Semeraro F, Smith C, Smyth M, Morley P, Olasveengen TM -on behalf of the International Liaison Committee on Resuscitation BLS Life Support Task Force.

Timing of CPR cycles (2 min vs other) Consensus on Science with Treatment Recommendations [Internet] Brussels, Belgium: International Liaison Committee on Resuscitation (ILCOR) Basic Life Support Task Force, 2019 Jan 1. Available from: http://ilcor.org

Methodological Preamble

The continuous evidence evaluation process for the production of Consensus on Science with Treatment Recommendations (CoSTR) started with a systematic review of basic life support conducted by Kevin Hung and Maaret Castren, with involvement of clinical content experts. Evidence for adult literature was sought and considered by the Basic Life Support Adult Task Force. These data were taken into account when formulating the Treatment Recommendations.

PICOST

The PICOST (Population, Intervention, Comparator, Outcome, Study Designs and Timeframe)

Population: Adults and children who are in cardiac arrest in any setting

Intervention: Pausing chest compressions at another interval

Comparators: Pausing chest compressions every two minutes to assess the cardiac rhythm

Outcomes: Survival to hospital discharge with good neurological outcome and survival to hospital discharge were ranked as critical outcomes. Return of spontaneous circulation (ROSC) was ranked as an important outcome.

Study Designs: Randomized controlled trials (RCTs) and non-randomized studies (non-randomized controlled trials, interrupted time series, controlled before-and-after studies, cohort studies) are eligible for inclusion.

Timeframe: All years and all languages were included as long as there was an English abstract; unpublished studies (e.g., conference abstracts, trial protocols) were excluded. Literature search updated to Sept, 2019.

There were two studies that indirectly addressed the comparison of interest. Both had different risk of bias, were confounded by a variety of factors and proved too different to combine in a meta-analysis.

Consensus on Science

Data were derived from two Randomized Controlled Trials (RCTs) whose principal focus was on the period of time allotted for CPR before the first rhythm analysis. Assessment of the time interval for CPR between subsequent rhythm evaluations and outcome were not formally reported analyses in either study. Rather, published data allowed for an ad hoc analysis by evidence evaluation experts appointed by ILCOR of the information available from the trials that indirectly addressed this question. Outcomes were not adjusted for possible confounders.

3 min vs 1 min

In the Wik study,(Wik 2003 289) the control group (1 min group) included patients that received immediate defibrillation (up to three stacked shocks) for VF/VT followed by 1 min of CPR patients in refractory VF/VT, and 3 minutes of CPR for patients that were in non-shockable rhythms following initial 1-3 shocks. The intervention group (3 min group) included patients that received immediate defibrillation (up to three stacked shocks) for VF/VT followed by 3 minutes of CPR regardless of post-shock rhythm.

For the critical outcome of survival to hospital discharge with favourable neurological outcome (O), we identified low-certainty evidence (downgraded for risk of bias and imprecision) from 1 RCT (Wik 2003 289) enrolling 200 adult out-of-hospital cardiac arrests (P), which observed no benefit from intervention (I) when compared to control treatment (C) (RR, 1.68; 95%CI, 0.85–3.32; P = 0.13; absolute risk reduction [ARR], -7.77%; 95% CI, −17.70% to 2.41%, or 78 more patients/1000 survived with the intervention [95% CI, 18 fewer patients/1000 to 230 more patients/1000 survived with the intervention])

For the critical outcome of survival to hospital discharge (O), we identified low-certainty evidence (downgraded for risk of bias and imprecision) from 1 RCT (Wik 2003 289) enrolling 200 adult out-of-hospital cardiac arrests (P), which observed no benefit from intervention (I) when compared to control treatment (C) (RR, 1.52; 95%CI, 0.83–2.77; P = 0.17; absolute risk reduction [ARR], -7.53%; 95% CI, −18.09% to 3.35%, or 60 more patients/1000 survived with the intervention [95% CI, 19 fewer patients/1000 to 203 more patients/1000 survived with the intervention])

For the important outcome of return of spontaneous circulation (O), we identified low-certainty evidence (downgraded for risk of bias and imprecision) from 1 RCT (Wik 2003 289) enrolling 200 adult out-of-hospital cardiac arrests (P), which observed no benefit from intervention (I) when compared to control treatment (C) (RR, 1.22; 95%CI, 0.92–1.50; P = 0.16; absolute risk reduction [ARR], -9.94%; 95% CI, −23.22% to 3.87%, or 25 more patients/1000 survived with the intervention [95% CI, 9 fewer patients/1000 to 69 more patients/1000 survived with the intervention])

1 min vs 2 min

In the Baker study,( Baker 2008 79) the control group (2 min group) included patients that were enrolled in a separate RCT after implementation of new guidelines introducing single shocks, 30:2 CPR and 2 min CPR cycles between defibrillations. The intervention group (1 min group) included patients that were enrolled in a separate RCT before implementation of new guidelines, and were therefore treated with stacked shocks (up to three in refractory VF/VT), 15:2 CPR and 1 min CPR cycles between defibrillations sequences. The change in guidelines happened 380 days into a 2 year long trial.

For the critical outcome of survival to hospital discharge (O), we have identified very-low-certainty evidence (downgraded for risk of bias, indirectness and imprecision) from 1 RCT (Baker 2008 79) enrolling 202 adult out-of-hospital cardiac arrests (P), which showed no benefit from intervention (I) when compared to control treatment (C) (RR, 0.49; 95%CI, 0.23–1.06; P = 0.06; absolute risk reduction [ARR], -9.23%; 95% CI, −0.49% to 18.45%, or 58 fewer patients/1000 survived with the intervention [95% CI, 88 fewer patients/1000 to 7 more patients/1000 survived with the intervention])

For the important outcome of return of spontaneous circulation (O), we have identified very-low-certainty evidence (downgraded for risk of bias, indirectness and imprecision) from 1 RCT (Baker 2008 79) enrolling 202 adult out-of-hospital cardiac arrests (P), which showed no benefit from intervention (I) when compared to control treatment (C) (RR, 0.95; 95%CI, 0.73–1.24; P = 0.71; absolute risk reduction [ARR], −2.60%; 95% CI, −11.04% to 16.113%, or 6 fewer patients/1000 survived with the intervention [95% CI, 31 fewer patients/1000 to 27 more patients/1000 survived with the intervention]).

Treatment Recommendations

We suggest against pausing chest compressions at another interval compared to pausing chest compressions every two minutes to assess the cardiac rhythm (weak recommendation, low quality evidence).

Justification and Evidence to Decision Framework Highlights

This topic was prioritised for review by the BLS Task Force as it had not been updated since 2015, at which time no direct evidence addressing this topic was identified. This largely also remains the case in 2020. Although the current review identified two older studies (from 2003 and 2008) which indirectly included comparisons between groups with different CPR durations, each had significant limitations. Both studies were designed to primarily address the question of CPR vs. defibrillation first, and the certainty of evidence derived from these studies to support recommendations on the optimal duration of CPR before a scheduled rhythm analysis was seriously confounded and therefore low.

In making the suggestion to pause chest compressions every two minutes to assess cardiac rhythm, we placed a high value on being consistent with previous recommendations and the absence of any signal emerging from the limited indirect evidence evaluated in this report to implicate a need for change. The BLS Task Force acknowledges that every change in guidelines comes with a significant risk and cost as CPR educators and providers are asked to change current practice and implement new treatment strategies for complex and high stress medical emergencies.

Knowledge Gaps

Current knowledge gaps include but are not limited to:

  • Does the optimal CPR interval between rhythm analyses differ for patients with different initial cardiac rhythms?
  • Does the duration between collapse and EMS arrival affect the optimal interval?
  • Do different intervals interfere with the overriding goal of minimising interruptions in chest compressions?
  • What is the relationship between rescuer fatigue, chest compression quality, and the optimal interval?

Attachments

Evidence-to-Decision Table: BLS-346 Timing of CPR cycles Et D

References

Baker PW, Conway J, Cotton C, Ashby DT, Smyth J, Woodman RJ, Grantham H; Clinical Investigators. Defibrillation or cardiopulmonary resuscitation first for patients with out-of-hospital cardiac arrests found by paramedics to be in ventricular fibrillation? A randomised control trial. Resuscitation. 2008;79(3):424-31.

Wik L, Hansen TB, Fylling F, Steen T, Vaagenes P, Auestad BH, Steen PA. Delaying defibrillation to give basic cardiopulmonary resuscitation to patients with out-of-hospital ventricular fibrillation: a randomized trial. JAMA. 2003 Mar 19;289(11):1389-95.


CPR

Discussion

GUEST
John Stewart RN, MA (265 posts)
I believe it is important to keep in mind the history of this topic. The 2-min post-shock CC protocol was instituted in 2005 not primarily to provide circulation for pulselessness after successful shocks; rather, it was clearly adopted to mitigate the harm of the lengthy “hands-off” periods for repeated rhythm analysis required by automated external defibrillators (AEDs). There is evidence that this strategy does improve survival when AEDs are used. However, its appropriateness for resuscitative attempts using manual defibrillators is highly questionable. If defibrillation results in the quick return of a perfusing rhythm, 2 additional min of CCs poses a risk of harm to the victim. Based on prior evidence for the efficacy of "stacked" shocks, a 2-min delay in giving a second shock for continuing VF could significantly decrease the likelihood of success. Claims of long intervals of pulselessness after successful shocks are dubious: one study found that delays of 2 min for return of a palpable pulse were common--if the first pulse check did not occur until the two-minute mark! The blanket recommendation for 2 min (or indeed any interval) of CCs before rhythm analysis and pulse check obscures a relative disadvantage of AEDs; it stands as a case of undue influence of the medical device industry over guidelines development.
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