A secondary study using data from the ROC PRIMED study suggests there could be something to the warnings about using supraglottic airways (LMAs) for airways in out-of-hospital cardiac arrests. Supraglottic airways were associated with increased mortality.
For the last five years or so, the supraglottic airways (SGAs) have increasingly been used as the preferred airway in out-of-hospital cardiac arrests (OHCA).
Then, in early 2012, Resuscitation published a small animal study by Segal et al. demonstrating significantly (15-50%) reduced carotid blood flow in pigs being resuscitated with a SGA for an airway as compared to traditional ETI-resuscitation.
That decreased carotid blood flow could result in increased mortality and worse functional outcome in the OHCA patients who get SGAs instead of traditional endotracheal intubation.
The study, by Segal et al, generated some controversy on the medical blogs. For the most comprehensive and accessible discussion about SGAs in OHCA you should listen to the EMcritpodcast here. Don’t forget to read the comments field.
ROC PRIMED was a large OHCA trial comparing early vs late ECG analysis as well as ITD vs placebo. The trial was stopped early for futility and became yet another huge, expensive and inconclusive cardiac arrest study that remains controversial. Interestingly, the study protocol did not dictate what airway the EMS were to use. As a consequence there is outcome data from OHCA airway management using both ETI and SGA. The secondary study used that data to explore if the airway used affects outcome.
The secondary analysis included OHCA patients who had successful out-of-hospital airways. Either they had traditional ETI one of three SGAs (King LT, Combitube and LMA). Primary outcome was survival to hospital discharge with a satisfactory functional status, defined as a Modified Rankin Scale score of 3 or more.
The study identified 8487 (81,2%) successful ETIs and 1968 (18,8%) successful SGAs. Of the SGAs 63% were King LTs, 20,5% were Combitube and 16,6% were LMAs.
Survival to hospital discharge with satisfactory functional status was 4,7% in the ETI group compared to 3,9% in the SGA group. This was considered a moderate association.
There were also stronger associations between ETI and ROSC and 24h survival.
Take home message
Supraglottic airways in out-of-hospital cardiac arrests might actually be associated with increased mortality and worse functional outcomes.
Studies like this have huge limitations. Even so, paying attention might pay off. ALS algorithms have in the past changed as a result of weaker evidence than this.
Resuscitation. 2012 Sep;83(9):1061-1066. Epub 2012 Jun 1. Endotracheal intubation versus supraglottic airway insertion in out-of-hospital cardiac arrest. Wang HE, Szydlo D, Stouffer JA, Lin S, Carlson JN, Vaillancourt C, Sears G, Verbeek RP, Fowler R, Idris AH, Koenig K, Christenson J,Minokadeh A, Brandt J, Rea T; The ROC Investigators.