Endotracheal intubation versus supraglottic airway insertion in out-of-hospital cardiac arrest

Resuscitation, Volume 83, Issue 9, September 2012, Pages 1047–1048

To simplify airway management and minimise interruptions to cardiopulmonary resuscitation (CPR) chest compression, there has been an increase in the use of supraglottic airway (SGA) devices instead of endotracheal intubation (ETI) as the primary airway adjunct in out-of-hospital cardiac arrest (OHCA). For this research the authors compared the outcomes of patients receiving ETI with those receiving SGA following OHCA.

A secondary analysis of data from the multicenter Resuscitation Outcomes Consortium (ROC) PRIMED trial was undertaken with adult non-traumatic OHCA receiving successful SGA insertion (King Laryngeal Tube, Combitube, and Laryngeal Mask Airway) or successful ETI studied. The primary outcome was survival to hospital discharge with satisfactory functional status (Modified Rankin Scale ≤3). Secondary outcomes included return of spontaneous circulation (ROSC), 24-h survival, major airway or pulmonary complications (pulmonary oedema, internal thoracic or abdominal injuries, acute lung injury, sepsis, and pneumonia). Using multivariable logistic regression, the authors studied the association between out-of-hospital airway management method (ETI vs. SGA) and OHCA outcomes, adjusting for confounders.

Of 10,455 adult OHCA, 8487 (81.2%) received ETI and 1968 (18.8%) received SGA. Survival to hospital discharge with satisfactory functional status was4.7% for ETI, compared with 3.9% for SGA. Compared with successful SGA, successful ETI was associated with increased survival to hospital discharge, ROSC and 24-h survival. ETI was not associated with secondary airway or pulmonary.

In this secondary analysis of data from the trial, ETI was associated with improved outcomes when compared with SGA insertion after OHCA.

Following the various published research studies which states that pre-hospital tracheal intubation can be associated with no benefit or is harmful this article could be welcomed by some as good news, providing the more evidence for they importance of paramedic intubation, but it may not be as simple as that.

The clinical trial was never intended to be used for the evaluation of airway management techniques and did not record such variables as time of airway insertion (for example before or after ROSC), number of airway attempts, whether the airway was displaced during resuscitation or transportation and interruptions to chest compressions. Likewise, the decision to intubate over the use of a SGA was left to the decision of the attending paramedic (no randomised trial) and, as the SGA is still thought to by some as a failed intubation device, could be the reason that a SGA was used, without intubation being attempted, in only 12.2% of cases. While taking this into consideration, this is a trial involving a large number of patients – over 10,000 – and the authors might have found some evidence in favour for the, often argued subject of whether paramedics should intubate.

It is clear that more research, not only randomised comparisons on airway devices with minimal variables (yes, I know how hard this is in the cardiac arrest situation but large number studies may reduce the effect of such variables) is required, but also a comparison on the different types of SGA device. As SGAs used to be considered as a failed intubation tool, the disadvantages were sometimes accepted, however with the increased use, or especially when considered as a primary adjunct, the risks associated with a SGA should be considered. In animal models it has been shown that there has been 15–50% decrease in carotid blood flow observed with the use of SGA (King LT, LMA and Combitube) compared with ETI, thought to be caused by the cuff and/or balloons applying pressure on the carotid artery. If this is found to be true in humans, this could affect neurological outcome and survival.  Other reported complications associated with Combitube use including aspiration pneumonitis, airway and esophageal injuries, and cranial nerve injury, similar adverse events may be possible with King LT or LMA use in OHCA.

One study which should provide interesting reading is the randomised trial of the I-gel versus LMA Supreme versus standard care in OHCA currently being undertaken within the UK (http://www.controlled-trials.com/ISRCTN18528625/18528625), especially as the I-gel does not have an inflatable cuff or balloon which not only decreases the time of insertion but could also reduce the pressure on the carotid artery when compared with other SGA devices.

Airway management is only a part of the resuscitation attempt, studies face a huge number of variables which could affect survival and ROSC, for example, the time taken until CPR started and first shock, the training and experience levels of paramedics, any difficult extrication causing prolonged interruptions to chest compressions, hyperventilation (both during CPR and post ROSC) and the use of therapeutic hypothermia. Until we have more evidence which clearly identifies the most appropriate airway management technique, I believe we should continue doing what we already know that improves ROSC and survival, for example:

  • Early recognition of cardiac arrest and ambulance activation;
  • Early CPR by bystanders and community responders;
  • Minimise time to first shock through the use of public access defibrillators, community responders and rapid ambulance response;
  • Good quality CPR with minimal interruptions and frequent changes to CPR providers to prevent tiring, this may also include the use of mechanical CPR devices but more research on these would be nice;
  • Utilisation of appropriate airway management devices without causing interruptions to compressions, this may be either an ETI or SGA, but the important thing is that chest compressions are not interrupted and hypoxia minimised during airway management attempts. Where resources are limited, it may be appropriate for a SGA device to be inserted very early while chest compressions are being undertaken and then when/ if ROSC is obtained, changed to a ET tube for the transportation phase and ROSC management strategy; and
  • Use of adrenaline, yes, the jury is still out on this but studies have shown that it can increase the likelihood of ROSC. Once we have ROSC, strategies such as therapeutic hypothermia, maintenance of blood pressure and arrhythmias, adequate ventilation and oxygenation (including the use of end-tidal capnography) and transport to PCI capable centres, where appropriate, should become our focus.

http://www.sciencedirect.com/science/article/pii/S0300957212002705

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