Classic Journal Review: The OPALS Study

The Ontario Prehospital Advanced Life Support (OPALS) Study

Background: Sudden cardiac arrest is common and, obviously, very bad. In the US, there are about 500,000 cardiac arrests each year. About half of these cardiac arrests are OHCA and the survival rate is pretty poor. The most recent survival estimates put it at 7 – 9.5% in most communities. About 10-12 years ago, the American Heart Association built the 4-step “chain-of-survival.”

• Step One – Early access to emergency care
• Step Two – Early CPR
• Step Three – Early defibrillation

There is little debate about these three steps as the sum of the data supports that they lead to better outcomes.

The 4^th step in the chain, however, is slightly more controversial; early advanced care. This basically means rapid access to ACLS type resuscitation skills (intubation and intravenous drug therapy). Despite it being the 4^th step, ACLS has little evidence to defend it. 

Clinical Question: What was the effect on survival in OHCA of adding ACLS to BLS?

Article: Stiell IG et al. Advanced Cardiac Life Support in Out-of-Hospital Cardiac Arrest. NEJM 2004; 351: 647-56. PMID: 15306666

Population: All persons > 16 yo who had an OHCA and for whom resuscitation was attempted.

Intervention: Advanced-life-support program whereby paramedics were trained in intubation, IV line placement, and IV medication administration.

Control: Basic-life-support – defibrillation + CPR

Outcome (Primary): Survival to hospital discharge (defined as patient leaving hospital alive).

Outcome (Secondary): ROSC, admission to hospital, and cerebral performance category.

Design: Multicenter, controlled clinical trial that was conducted in a before and after model.

Excluded: < 16, persons who were dead, patients with trauma, disorders of clearly noncardiac cause.

Primary Results

• 5638 patients over 48 months in 17 communities and 11 hospitals
• 1391 Rapid-defibrillation phase (no ACLS) over 12 months
• 4247 Advanced-life-support phase over 36 months
• Initial cardiac rhythm not significantly different between groups.
• Medications (ACLS phase)
  • Epinephrine 95.8%
  • Atropine 87.3%
  • Lidocaine 23.6%

Critical Findings

• ROSC: 12.9% vs. 18.0% (absolute change 5.1% p < 0.001)
• Admission to hospital 10.9% vs. 14.6% (absolute change 3.7% p < 0.001)
• Survival to hospital discharge 5.0% vs. 5.1% (absolute change 0.1% p 0.83)
• Survivors’ Cerebral-performance category level 1 – 78.3% vs. 66.8% (p 0.73)

Strengths:

• Large, multicenter trial
• Study asked a clear clinical question that was patient centered
• Minimal exclusions increasing applicability
• Outcome measures were objective reducing bias
• Follow up was complete and appropriately long

Limitations:

• Non-randomized
• Non-blinded

Authors Conclusions: “The results of the OPALS study did not show any incremental benefit of introducing a full advanced-life-support program to an emergency-medical services system of optimized rapid defibrillation.”

Clinical Bottom Line: The institution of ACLS into OHCA care improved the rate of ROSC without improving the return of neurologic function (RONF). Increasing ROSC without improving RONF means that there are more patients “alive” without good neurologic outcomes. This is not the goal of OHCA management. Epinephrine, the cornerstone drug in ACLS, in its current recommended regimen may be a major culprit in getting back the heart but not the brain.

Bottom Line: Addition of an advanced life support algorithm to BLS management did not increase the survival to hospital discharge for patients with OHCA.

For More on This Topic Checkout:

• The Skeptics’ Guide to EM: SGEM#64 – Classic EM Papers (OPALS Study)
• emDocs.net: Epinephrine in Cardiac Arrest

Post Peer Reviewed By: Salim Rezaie (Twitter: @srrezaie)