Basic Versus Advanced Life Support Ambulances for Out-of-Hospital Medical Emergencies
*Prachi Sanghavi, Harvard University
Keywords: multilevel, instrumental variables, propensity scores, emergency medicine
Most Medicare patients seeking emergency medical transport are treated by ambulance providers trained in Advanced Life Support (ALS). Evidence supporting the superiority of ALS over Basic Life Support (BLS) is limited. We compared effects of ALS and BLS on outcomes after out-of-hospital medical emergencies. We analyzed claims from a 20% sample of Medicare beneficiaries from non-rural counties between 2006-2011 with major trauma, stroke, acute myocardial infarction (AMI), or respiratory failure. To address unmeasured confounding, we exploited variation in geographic penetration in ALS rates across counties, using instrumental variables analysis. In particular, we predicted the probability of ALS use for each patient as a function of ALS rates in each county for patients with other diagnoses, using a multilevel, multivariate model. Survival to 90 days for trauma, stroke, cardiac arrest, and AMI patients was higher with BLS than ALS; respiratory failure patients did not exhibit differences in survival. ALS is associated with substantially higher mortality for several acute medical emergencies compared to BLS, and may harm patients through delayed hospital care and iatrogenic injury.