Helicopter transport is entrenched in our systematic management of trauma. It is glamorized on television, and retrospective National Trauma Data Bank studies seem to suggest survival improvement – and those with head injury seem to benefit most.
But, these NTDB studies encompass heterogenous populations and are challenged in creating truly equivalent control groups. This study, on the other hand, is a single-center experience, allowing greater consistency across divided cohorts. In a novel approach, these authors collected all HEMS trauma transfer requests to their facility across their 30-county catchement area – and specifically looked at occasions when weather precluded HEMS. This therefore created two cohorts of patients eligible for HEMS, with a subset that was transported by ALS due to chance events. The paramedic crews manning the HEMS and ALS transfers were staffed by the same company, and therefore had roughly equivalent training.
This created a cohort of 2,190 HEMS transports and 223 ground transports. Across ISS, GCS, initial transfusion requirements, and vital signs, the two groups had generally minor differences. However, there was some potentially important variability of initial operative intervention upon arrival at the Level 1 trauma center – 27.4% of HEMS underwent craniotomy, compared with 15.4% of ALS transfers. Based on multivariable logistic regression, type of transport did not enter into a best fit model of survival – and, thus, there was no difference (9.0% vs 8.1% mortality) between HEMS or ALS transport of trauma patients, despite the additional hour added from call time to arrival at the Level 1 trauma center.
Unfortunately, there are potentially critical flaws in their methods for patient selection. They report 3,901 patients had a request for trauma transfer – but the number of patients transferred by HEMS or ALS only sums to 2,398. An additional 49 were transported by BLS. Then, another 208 died while awaiting transfer. How many of these 208 died during weather delays awaiting ALS? Are those deaths, in some fashion, related to the paucity of craniotomies performed on ALS transports? And, what of the other 965 patients?
I tend to agree with their conclusion – HEMS is expensive and far over-utilized for patients who receive no particular benefit from the time savings. However, I’m not sure this analysis includes all the data needed to be reliable evidence.
“When birds can’t fly: An analysis of interfacility ground transport using advanced life support when helicopter emergency medical service is unavailable”
http://www.ncbi.nlm.nih.gov/pubmed/25058262