Out of Hospital Cardiac Arrest- Keeping It Real With Really Limited Resources
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Out of Hospital Cardiac Arrest (OHCA) care is a resource-intensive endeavor. This can really strain a treatment team especially when personnel are low. Whether that be in a rural community ED or a busy city setting with lots of call-outs- we all can be strained for personnel resources. In this blog and associated podcast we review the data on where we should focus our attention and how to best care for these patients in a low resource setting.
The Pillars of Cardiac Arrest Care
We need to know what matters first, so we know what is fluff. The two pillars of cardiac arrest care (the things that save lives) are:
High Quality CPR
Early and efficient defibrillation
The resource intensive parts of care, and areas where we can do things more simply (by the literature anyway) are:
Manpower (chest compressions)
Vascular Access
Airway
Ultrasound
1. Man (or woman) Power
Mechanical devices vs standard compression-
In the modern day the big question with regard to CPR is man vs machine. Are mechanical devices equal to or better than manual compressions? The best data we have is from a 2015 meta-analysis by Gates in Resusitation. This was a systematic review and meta-analysis of five randomized trials comparing mechanical CPR to manpowered CPR. It included: ASPIRE ’06 (AutoPulse), Semkal ’11 (LUCAS), LINC ’14 (LUCAS), CIRC ’14 (AutoPulse) and Paramedic ’15 (LUCAS). It is important to note this was an update of a 2013 Cochrane review with many older devices that included a load-distributing band style. The new piston style devices (picture the Lucas or Lucas 2) were more heavily weighted in the Gates study. In the end they concluded the “data do not suggest that mechanical chest compression devices are superior to manual chest compression.” In sum, we feel these devices are not superior, but likely equal, to manual compressions. In a low resource, low personnel setting, these piston style devices are the way to go.
2. Vascular Access
With regard to access, the big question is whether patients need an IV, or is an IO adequate? In this area there is a bit of data:
Reades in 2011 (Pubmed) performed a paramedic-based study where they looked at three access locations- tibial IO, humeral IO and peripheral IV. Before study execution, paramedics were trained in a cadaver lab on the proper IO insertion techniques. In their six month enrollment timeframe, 182 OHCA patients were randomized to one of the three access sites.
They found tibial IO outperformed both humeral IO and peripheral IV in the measurable end points of first attempt success (primary outcome), time to access success, and time to first medication administration. The humeral IO had significantly higher displacement rates than either tibial IO or peripheral IV. It is important to note 13 (out of 182) protocol violations favored tibial IO, which may point to the paramedics’ preference in access type.
But this is not patient-centered data…
When we start looking at this we see an apples and oranges comparison.
This retrospective cohort study in Washington state examined their EMS cases of OHCA. The EMS personnel were not given special instruction but were told to follow their standard protocol in ACLS and vascular access (explained to typically be attempts at an IV and, if unsuccessful, insert an IO).
They looked at 1,021 IV OHCA (82%) and 220 IO OHCA (18%) cases. It is important to note, the baseline characteristics of the two groups were not the same. The IO group tended to be younger, female, have an unwitnessed arrest, noncardiac cause, and have an initial rhythm that was non-shockable. Aside from age and gender these differences all portend a worse prognosis.
When looking at patients with data on time from call to vascular access (data they weirdly never reported), they found IO was associated with lower rates of ROSC and survival to hospital admission. There was no difference in rates of survival to hospital discharge.
This was a secondary analysis of the ROC PRIMED study (which looked at impedance devices and delayed vs early rhythm analysis). This study plucked out the patients who got IO access only and compared them to IV access OHCA patients. They had 660 patients who got IO as their first and only attempt. To avoid confounding, they excluded patients who had a failed attempt at either IV or IO. They compared the 660 patients who got IO only to the 1,2495 who got IVs only (5% of the group got IOs and 95% IVs). The two groups were not similar at baseline. They tried to do a propensity score match analysis of similar IV patients to IOs to compensate for this.
In the end, they found IO to be associated with worse rates of ROSC, survival to hospital discharge and neurologically intact survival. This article has come under criticism given its low rate of IO use and unmatched group comparisons.
BOTTOM LINE- With these articles we see the IO group was not the same as the IV group. Right now we don’t have good patient-centered data. We know the IO was faster and easier, but it begs the question - which access saves lives and brains? See our review of the Paramedic 2 trial for a deeper dive on that.
3. Airway
Do all OHCA patients need to be intubated? Does intubation hinder the rest of the resusitation? These questions have been looked at in several studies, three of which are worth reviewing.
This France and Belgium based study examined bag mask ventilation (BVM) vs endotracheal intubation (ETI) in OHCA. Its aim was to assess non-inferiority of BVM to ETI in OHCA. The airway technique was randomly assigned and there were approximately 1000 patients per group. It assumed a ~1% improvement in favorable neurologic outcomes at 28 days between BVM and ETI would show non-inferiority.
The primary outcome of favorable functional survival (CPC 1-2) was 4.3% in the BVM group and 4.2% in the ETI group. This did not meet the 1% difference needed to show non-inferiority. The rate of ROSC was higher in the ETI group (38.9% vs 34.2%).
It also noted the rate of difficulty with airway management was higher in the BVM group (18% BVM vs 13% ETI). Airway technique failure was also higher for BVM (6.7% BVM vs 2.1% ETI). This was in the setting of ETI being the backup to BVM and bougie assisted intubation, supraglottic airway, or video assisted intubation being backup to ETI. That may have driven earlier declaration of failure in the BVM group.
Benger (AIRWAYS 2) SGA vs ETI Aug ‘18
This England based study randomized paramedics to use either supraglottic airway (SGA, the igel) or ETI as their primary advanced airway device in patients with OHCA. Medics could deviate from this if they thought it was in the patient’s best interest.
There were 4100 patients in the ETI group, 4800 in the SGA group. The primary outcome was good neurologic survival (modified rankin scale 0-3) and the hypothesis was that a SGA would result in better functional outcomes when compared to ETI.
There was no difference between groups in the primary outcome of a neurologically intact survival (6.4% in SGA vs 6.8% in ETI). The SGA group was significantly more likely to achieve ventilation in two attempts or less. If the medic was assigned to ETI they were less likely to use advanced airway techniques and more patients crossed over to the SGA device intervention than the other way around.
BOTTOM LINE- From these three articles we can see that BVM may be equitable to ETI with regard to outcomes in OHCA, but getting a good mask seal is hard. The supraglottic devices are likely equitable and much of the data shows them to be easier to place. When resources are low, go supraglottic and move on.
4. Ultrasound
Ultrasound (US) in cardiac arrest has a couple associated questions:
Does US improve outcomes in cardiac arrest?
Does US help prognostic cardiac arrest patients?
A non-randomized, protocol-driven prospective trial looking at patients with cardiac arrest both out of hospital and in the Emergency Department. The authors’ aim was to determine whether cardiac activity on US during ACLS is associated with improved survival. They chose to investigate only PEA and asystolic patients.
All ultrasounds were preformed during pauses in CPR and were quickly executed (averaging around 4.5 seconds). The authors looked at possible characteristics of the arrest that could be associated with ROSC, survival to admission and survival to discharge, with attention to cardiac activity on US (performed at the beginning of ACLS). Roughly 1/3 of PEA/asystole patients had cardiac activity on US, meaning 2/3 did not.
The study found the presence of cardiac activity was positively associated with ROSC, survival to admission, and survival to discharge. Other associated characteristics included PEA (vs asystole), female gender, and the presence of a shockable rhythm at any time.
Reviewed 24 cases of cardiac arrest that were video recorded. They assessed 110 pauses in CPR, looking to see if POCUS was associated with increased pause duration.
They found that it was indeed associated with longer pauses (mean 19 seconds vs 14 seconds and median 17 seconds vs 11 seconds). There was significantly longer pauses when the person performing the POCUS was also running the code. There was an association with shorter length of pause if the POCUS person was fellowship trained in US.
This article described a structured approach to US use in PEA. They recommend using the Cardiac Arrest Sonographic Assessment (CASA) structure, which purposefully targets reversible causes of PEA that can be treated to improve mortality. They suggest 1) an assessment for pericardial tamponade 2) assessment for right heart strain, and finally 3) an assessment of cardiac activity. Each assessment should take <10 seconds and would occur after a two minute round of properly executed ACLS.
BOTTOM LINE- US can help outcomes in a few select PEA patients and can definitely help prognosticate when there is the presence or absence of cardiac activity. Clattenburg showed us, however, that US can be a time suck and keep us away from high quality CPR. To prevent this, we should have a structured approach.
