JOURNAL CLUB PODCAST DECEMBER 2022
DR DANNY MARHABA DR JIUN KAE PUI PROFESSOR PETER CAMERON
Welcome to the December Journal Club Podcast. We are again joined by Professor Peter Cameron, Academic Director for the Alfred Emergency and Trauma Centre and Dr Jiun Kae Pui, Emergency Consultant at Alfred Emergency and Trauma Centre.
This month we discuss the benefit of reduced FiO2 for patients following cardiac arrest and the use of double-sequetial-external-defibrillation vs vector change in VF.
EFFECT OF LOWER VS HIGHER OXYGEN SATURATION TARGETS ON SURVIVAL TO HOSPITAL DISCHARGE AMONG PATIENTS RESUSCITATED AFTER OUT-OF-HOSPITAL CARDIAC ARREST. THE EXACT RANDOMIZED CLINICAL TRIAL
READ IT HERE
CLINCIAL QUESTION:
Does reducing FiO2 after cardiac arrest to target SpO2 90-94% in the out of hospital setting improve survival at hospital discharge?
BACKGROUND
Hyperoxia after OOHCA has been implicated in worse outcomes, leading to advocacy against hyperoxia (1). Does this evidence extend to the early post-arrest environment, or should early hyperoxia be tolerated for the initial resuscitation, transport and investigations?
STUDY DESIGN & PICO
DESIGN
Open Label Randomized Controlled Trial.
POPULATION
Unconscious adults ≥ 18 years of age, with ROSC following OOHCA with SpO2 ≥95% while receiving oxygen of 10L/min or 100% FiO2 if intubated.
INTERVENTION
Oxygen reduced initially to 4LPM to achieve peripheral SpO2 of 90-94%.
COMPARISON
Higher flow oxygen to achieve peripheral SpO2 of 98-100%.
OUTCOME
Primary:
Survival to hospital discharge
Secondary Outcomes
A collection of findings including rearrest, hypoxia out-of-ICU, survival to ICU discharge, and hospital LOS.
FINDINGS
Survival to discharge was not improved in the arm with reduced oxygen targets (90-94%).
AUTHORS' CONCLUSIONS
Among patients achieving ROSC after out-of-hospital cardiac arrest, targeting an oxygen saturation of 90% to 94%, compared with 98% to 100%, until admission to the ICU did not significantly improve survival to hospital discharge.
JOURNAL CLUB THOUGHTS
The lower target of SpO2 90-94% did not improve survival. In fact, there was a signal to harm with an absolute survival difference of 9.6%, and an odds ratio of 0.68 reaching P = 0.05 in favour of the early hyperoxia arm (the actual number was 0.0496 however JAMA requires this be rounded up to 0.05.
When looking at the secondary outcome of hypoxia, there was a clear increased likelihood of hypoxia when targeting the lower SpO2. Intuitively this makes sense, hypoxia is more likely with lower initial oxygen targets, and early hypoxia after OOHCA can cause worse outcomes.
Though we know that hyperoxia is harmful, hypoxia is probably worse. In the undifferentiated patient after OOHCA, who is undergoing transport and initial investigations – it is prudent to provide a higher oxygenation target in the early 1-2 until transport, resuscitation and initial investigations are attained.
Typically, researchers will exert a great degree of effort to avoid stopping a trial early. One reason is because the results often vary in both directions as the trial progresses, this is why a pre-determined stop point is optimal – so that the trial is not stopped as soon as a 0.05 limit is reached (in either direction).
Recruitment in this trial was challenged by varying ethics requirements across states, which changed during the course of recruitment – as well as the COVID pandemic due to changes of protocols in oxygen provision.
SHOULD PREHOSPITAL CLINICIANS INCORPORATE DOUBLE-SEQUENTIAL-EXTERNAL-DEFIBRILLATION OR A VECTOR CHANGE IN REFRACTORY VFIB ARREST?
READ IT HERE
CLINCIAL QUESTION:
Should prehospital clinicians incorporate double-sequential-external-defibrillation or a vector change in refractory VFib arrest?
BACKGROUND
Double-Sequential-External-Defibrillation (DSED) has been proposed as an intervention to improve the likelihood of achieving return of spontaneous circulation (ROSC) from refractory ventricular fibrillation (VF) (2), without damaging the involved defibrillators (3). Reducing time to ROSC, is one component of the pursuit to increase neurologically intact survival in patients with out-of-hospital-cardiac-arrest (OOHCA).
STUDY DESIGN & PICO
DESIGN
Open-label cluster randomised controlled trial.
POPULATION (TARGET)
Patients ≥18 years of age who suffered an OOHCA in VF or VT, which persisted despite 3 standard anterolateral defibrillations with 2-minute intervals.
INTERVENTION 6 prehospital cohorts, crossing over to vector change antero-posterior defibrillation, or to one-person DSED.
COMPARISON
Standard ALS including standard anterolateral defibrillation.
OUTCOME
Primary outcome
Survival to Hospital Discharge
Secondary outcomes
Termination of VF
ROSC
Modified Rankin Scale Score ≤2
WHAT WERE THE FINDINGS?
Primary Outcome
38/125 (30.4% of) patients in the DSED arm survived, compared with 31/143 (21.7%) in the Vector Change arm, and 18/135 (13.3%) in the standard treatment arm. The adjusted relative risk (aRR) of both DSED and Vector Change arms demonstrated a statistically significant increase in survival when compared to standard treatment.
Secondary Outcomes
All secondary outcomes in the DSED arm reached statistically significance, from termination of VF (aRR 1.25, CI 1.09 – 1.44) to likelihood of ROSC (aRR 1.72, CI 1.22 – 2.42), to proportion of MRS ≤ 2 at discharge (aRR 2.21, CI 1.26 – 3.88).
Only likelihood of termination of VF in the vector change arm reached statistical significance (aRR 1.18, CI 1.03 – 1.36).
AUTHORS' CONCLLUSIONS
Among patients with refractory ventricular fibrillation, survival to hospital discharge occurred more frequently among those who received DSED or VC defibrillation than among those who received standard defibrillation.
JOURNAL CLUB THOUGHTS
A 30% survival under any intervention for patients with a refractory VF arrest is a high survival percentage.
CLINICAL BOTTOM LINE
This is a practice-changing trial - in patients with a refractory VF or VT arrest, who fail to respond to standard defibrillation where other interventions (such as E-CPR) are unavailable, it would be prudent to make use of a vector change or DSED to improve patient outcomes.
DR DANNNY MARHABA
Emergency Registrar
Danny is an Emergency Medicine Registrar at the Emergency and Trauma Centre and the current Senior Registrar for research. He trained in regional NSW before moving back to Melbourne to complete his training at the Alfred.
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