38
AMBULANCE DIVERSION
Scheulen et al. • IMPACT OF AMBULANCE DIVERSION POLICIES
T
ABLE 1. Ambulance Arrival Rate (Patients/Hr) to the
cies should be selective, each aimed at controlling
flow to a specific portion of the EMS system.1 While
of growing interest, the literature is limited in its
analysis of the impact of diversion policies. Much
of the initial literature is limited to discussion of
the underlying causes for ED diversion, but does
not examine the issue from a regional level.2–4 The
Maryland state EMS system provides for a number
of diversion policies, including policies aimed at
controlling patient flow for trauma centers and
specialty centers (burn, eye, hand trauma), as well
as general hospital bypass policies.
Emergency Department while Off Alert, Maryland, 1996
Geographic Area
Region
Acuity/Priority
Urban
Suburban
Rural
Total
1
2
3
0.08
0.18
0.42
0.11
0.24
0.43
0.07
0.21
0.28
0.09
0.20
0.40
TOTAL
0.68
0.79
0.56
0.70
ber of low-acuity priority 3 patients, while in rural
areas a lower number of priority 3 patients were
transported. However, in all areas, priority 3 pa-
tients accounted for the largest patient group.
Differences in the arrival rates of priority 1 pa-
tients when the EDs in any of the areas under re-
view were on yellow alert were minimal and sta-
tistically indiscernible (Table 2). In rural areas,
yellow alert did not affect the arrival rates of pa-
tients in any category (priority 1, 2, and 3). How-
ever, in the urban and suburban areas, priority 2
and 3 patients were diverted in significant vol-
umes.
The diversion pattern for red alert is different
from that of yellow alert (Table 3). At the regional
level, the overall impact of red alert is significantly
greater than the impact of yellow alert, reducing
patient flow to the ED by 0.4 patient/hr vs a re-
duction of 0.18 patient/hr under yellow alert. The
impact of red alert was that patients of all priori-
ties, 1, 2, and 3, were diverted in significant num-
bers in all areas under study. Low-acuity patients
were diverted from the ED in significant numbers
despite the stated purpose of red alert, to control
the flow of patients requiring monitored or ICU
bed care.
The high diversion rate for low-acuity patients
by an alert status aimed at controlling ICU volume
caused us to further assess the potential impact of
red alert. Our review of patients arriving by am-
bulance to the study hospital revealed 703 trans-
ported patients during the 31 selected days. Of
those, 593 patients had medical complaints, and
397 of these patients were EMS priority 2 or 3. Of
the 397 medical priority 2 or 3 patients, 124
(31.2%) required hospital admission and only six
(1.5%) required hospital admission to an ICU; an
additional eight required admission to a telemetry
monitored bed.
The data suggest that the use of diversion pol-
icies aimed at controlling ED volume does, as in-
tended, divert a small but significant number of
lower-acuity patients from the ED when it is over-
taxed. Also as intended, there is no change in the
arrival rate of patients with potentially life-threat-
ening emergencies. It is also apparent that out-of-
hospital providers in rural areas are commonly
forced to ignore the alert status of local hospitals
since there are few, if any, alternatives within a
reasonable distance (<15 minutes transport time).
What was surprising was the relatively low num-
ber of patients apparently diverted. It is a com-
monly held tenet among ED providers that alerts
aimed specifically at managing ED volume do, in
fact, divert significant patient volume. Our study
suggests that overall, about one patient is diverted
for each five hours on alert. While statistically sig-
nificant, this alert may not be providing the antic-
ipated or required relief in all settings.
The impact of the alert aimed at controlling
ICU volume (red alert) was greater and more gen-
eralized than expected. Patients of all acuities
were being diverted from hospitals on red alert,
including patients requiring outpatient ED care or
general hospital admission and not admission to
ICU beds.
Recalling that red alert is intended to divert pa-
tients who may require ICU admission, one must
question the value of diverting priority 2 and 3 pa-
tients, since it is generally believed that those pa-
tients only infrequently require admission to in-
tensive care areas. The minimal likelihood for
admission of priority 2 and 3 patients to ICU beds
was confirmed by our review of ambulance run
sheet data that examined the disposition of prior-
ity 2 and 3 patients delivered to an academic urban
medical center. Of the patients (priority 2 and 3)
delivered, approximately 31.2% required admis-
sion to inpatient units; however, only 1.5% re-
quired admission to ICU beds. An additional 1.8%
required admission to a telemetry monitored bed.
DISCUSSION
It is incumbent upon an EMS system to consider This would suggest that the risk of removing red
efficient utilization of resources. For this reason, it alert is minimal; if red alert were eliminated or
is common for systems to create diversion policies never used, there would exist a 3% chance of hav-
that are meant to control patient flow. These poli- ing a patient arrive who would require either a
Smiles
