Cancellation of responding ALS units by BLS providers: a national survey

In many emergency medical services (EMS) systems, personnel without advanced life support (ALS) training are authorized to cancel responding ALS units before the ALS personnel arrive and examine the patient. This study was conducted to examine these cancellations in major U.S. cities.

A survey was mailed to the physician medical directors of the EMS services of the 125 largest U.S. cities, with telephone follow-up of nonresponders. The survey requested information on system structure, and on policies governing cancellation of responding ALS units by non-ALS personnel.

Ninety-four cities responded (75%), from 35 states. Nineteen systems (20%) are all-ALS with no basic life support (BLS) tier, and these were eliminated. Of the remaining 75 systems, eight (11%) use BLS ambulances (BLS-A), 35 (47%) use BLS first responders (BLS-FR), and 32 (43%) use both. Of these 75 systems, 60 (80%) allow cancellation of responding ALS units by BLS personnel. Only 24 of these (40%) have written protocols for such cancellations, and only 12 of those (50%) involve specific medical criteria, with two (8%) relying on the best judgment of the BLS personnel with no medical criteria, and another eight (33%) allowing cancellation only for logistic reasons. Of the 60 systems that permit cancellation, 13 (22%) perform some type of medical oversight review of all such calls, 26 (43%) review some such calls (median 10%, range 2-80% for the 19 systems specifying a percentage), 15 (25%) do not review any, and six did not specify.

Fewer than half of the surveyed EMS systems that permit non-ALS personnel to cancel responding ALS units use written protocols to guide these decisions, and only half of those protocols utilize specific medical criteria. Medical oversight review of these calls is highly variable, with many systems reviewing few or none of these cancellations.