The effect of base station contact on ambulance destination

ORIGINAL CONTRIBUTION ambulance, diversion; base station

T h e Effect of B a s e S t a t i o n C o n t a c t on Ambulance Destination Concern has been raised that a single medical control base station serving a metropolitan area may preferentially divert ambulance patients to the, base station hospital. Such concern m a y discourage the development of regional medical control systems. During the first six months of 1988, a retrospective cross-sectional analysis was made of all advanced life support (ALS) ambulance transports and all contacts to the single base station, known as Medical Resource Hospital (MRH). Destinations of all ALS ambulance calls dispatched through the county's 911 dispatch center were analyzed to determine whether the destinations were affected by M R H contact. There were •2,396 transports to 17 area hospitals with 1,272 (10.3%) of these requiring MRH contact. We hypothesized that if M R H contact did not affect destination, the proportion of all non-MRH ALS ambulance patients received by each hospital from the 911-dispatched group would equal the proportion of patients received by each hospital after MRH contact. Five hospitals received a statistically significant (P < .003) different percentage of M R H contact patients than their proportion of 911dispatched patients would have predicted. The three that received more were community hospitals in outlying areas. The remaining two were a large referral hospital and a smaller community hospital located in the urban area. The MRH hospital did not have a significantly different percentage of 911-dispatched patients after M R H contact. Similarly, destinations of specific ALS ambulances (two serving in the MRH ambulance catchment area and four in distant catchment areas) were evaluated. M R H did not receive a statistically higher proportion of ambulance patients from either group after M R H contact than the 911 dispatch proportion would have predicted. We found no evidence of preferential diversion of patients to the base station hospital. [Neely KW, Norton R, Bartkus E, Schriver J: The effect of base station contact on ambulance destination. Ann Emerg Med August 1990;19:906~909.]

Keith W Neely, MPA, EMT-P Robert Norton, MD Ed Bartkus, EMT-P John Schriver, MD, FACEP Portland, Oregon From the Division of Emergency Medicine, Oregon Health Sciences University, Portland. Received for publication August 28, 1989, Revision received December 27, 1989. Accepted for publication February 26, 1990. Study support was provided by the Multnomah County Office of Emergency Medical Services. Address for reprints: Keith Neely, MPA, EMT-P, Division of Emergency Medicine, Oregon Health Sciences University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97201-5566.

INTRODUCTION On-line medical control provided by base stations located in an emergency medical services (EMS) system area is essential3 A variety of medical control models exists and ranges from paramedics calling the patient's receiving hospital for medical advice to identifying designated base station hospitals that provide medical direction to a specific set of advanced life support (ALS) units within a larger EMS jurisdiction to a single base station serving a large metropolitan area. Base station personnel interact closely with ALS units, providing medical direction, continuing medical education, and performing quality assurance activities. Concern has been raised that this close working relationship may preferentially influence patient destinations toward the base station hospital. Such concern may discourage the development of a single on-line regional medical control system for an EMS service area~ This study measured the impact that base station contact has on patient destination in an urban EMS system with a single base station. Both the methods and results of this study are relevant to EMS systems that want to address the potential nonpatient-care influence of on-line medical control.

19:8 August 1990

Annals of Emergency Medicine

906/99

BASE STATION Neely et al

METHODS During the first 28 weeks of 1988, a review was conducted of all transports by ALS ambulances originating in Multnomah County, Oregon, and of all contacts by these same ALS crews to the county's single base station, k n o w n as M e d i c a l Resource Hospital (MRH). Transport data came from the Multnomah County Office of EMS, which tracks the number of transports each M u l t n o m a h County ALS unit makes daily to each of the regional hospitals. Multnomah C o u n t y has a central 911 dispatch center that records destinations of all a m b u l a n c e s dispatched by the 911 center. Excluded from consideration were dispatches that did not result in transport. Base s t a t i o n c o n t a c t data were taken from MRH logs and included ALS unit number, hospital destination of the ambulance, and nature of the problem requiring MRH contact. These logs are c o m p l e t e d by the MRH physician at the time of paramedic contact. All MRH contacts d u r i n g the s t u d y p e r i o d were reviewed. Paramedics operate under uniform prehospital care protocols established by a medical advisory board. These protocols require MRH c o n t a c t for c e r t a i n m e d i c a l p r o b l e m s and encourage MRH contact whenever the paramedic desires additional medical direction. Paramedics generally contact MRH because they are facing complex management problems. Management of cardiac patients, patients with cardioputmonary arrest, and patients with respiratory distress represent almost one half of the calls to MRH (Table 1). Contacts with MRH also address patient disposition when patients refuse t r a n s p o r t or when p a r a m e d i c s wish to pronounce cardiac arrest patients dead in the field. Patient refusals and p a t i e n t s who were pron o u n c e d d e a d in t h e f i e l d w e r e excluded from the survey; also excluded were patients who were entered into the regional trauma syst e m and w h o were, by p r o t o c o l , transported to one of two designated trauma centers. D a t a were o r g a n i z e d into seven four-week time periods corresponding to the reporting periods of the M u l t n o m a h C o u n t y 911 d i s p a t c h center. The Multnomah County data provided the number of patients each 100/907

TABLE 1. Nature and distribution of all MRH calls and of MRH contacts involving ambulance diversions MRH (1,272) Nature Altered mental status Anaphylaxis Cardiac Cardiac arrest

N

%

105

8.3

Divert N 2

% 4.2

8

0.6

1

2.1

233

18.3

5

10.6

77

6.0

0

--

Hypertensive emergency

0

0

--

Hypothermia

1

0

Near-drowning

1

0

_

10

0.8

1

2.1

Poisoning or overdose

157

12.3

4

8.5

Respiratory

304

23.9

12

25.5

Seizures

110

8.6

9

19.1"

4

0.3

0

174

13.7

8

17

Other

71

5.6

5

10.6

Unknown

17

1.3

0

Obstetric emergency

Toxic exposure Trauma

*Statistically significant MRH, Medical Resource Hospital; divert, ambulance diversions.

hospital received during each period. From this, a proportion of ambulance transports (Ptrans) to each hospital was derived by dividing the number each hospital received by the total n u m b e r of t r a n s p o r t s d u r i n g the study period. Patient transports with MRH contact were excludcd from the Ptrans ratio. The MRH data for the same time p e r i o d s were s i m i l a r l y organized. The n u m b e r of ALS-transported pat i e n t s each h o s p i t a l received after paramedics made contact with MRH was divided by the total number of MRH contacts during the study period. T h i s p r o p o r t i o n (Pmrh) was compared with Ptrans. The null hypothesis was that base station contact has no influence on ambulance d e s t i n a t i o n ; therefore, there would be no statistically significant difference between Ptrans and Pmrh. That is, base station contact should not alter general patient transportation patterns. The MRH data were further assessed by r e v i e w i n g all MRH logs documenting an ALS unit diversion that was either learned of or decided on during MRH contact. A diversion was defined as any instance in which a change of hospital destination was Annals of Emergency Medicine

noted in the log. A separate data set was created that examined original hospital destination, actual hospital d e s t i n a t i o n , n a t u r e of the p a t i e n t problem, and reason for diversion. A g a i n , t h e p r o p o r t i o n of M R H i n v o l v e d d i v e r s i o n s (Pdivert) each hospital received was calculated by dividing the number of diverted patients each hospital received by the total number of hospital diversions. Pmrh was then compared with Ptrans. The null hypothesis was that there would be no significant difference between Pdivert and Ptrans if MRH had no influence on the hospital destination during a diversion. Proportions for all hospitals were compared by X2 analysis. P < .05 was considered significant. When a difference was found, each hospital's proportion was individually reassessed using x 2 analysis with correction for the m u l t i p l e c o m p a r i s o n s by the Bonferroni m e t h o d (P = .05/17 .003). To e v a l u a t e the p o s s i b i l i t y that MRH contact might exert a selective effect on ALS u n i t s closest to the MRH, an a n a l y s i s was also performed that considered specific ALS units. Destinations with and without M R H c o n t a c t for the two ambu19:8 August 1990

TABLE 2. Relationship between all transports to the various metropolitan hospitals and hospital destinations after M R H contact Hospital A No. of patients Ptrans(N) 95% CI No. of patients Pmrh(N)

895 (8.0) 7.5 8.5 78 (6.1)

B

C

D

E

48 232 2,021 920 (0.4)(2.1)(18.2)(8.3) 0.3 0.5

1.8 2.4

17.5 18.9

7.8 8.8

F 476 (4.3) 3.9 4.7

41" 24 177" 91 37 (3.2)(1.9)(13.9)(7.2)(2.9)

G

H

I

M (MRH)

N

1,429 (12.8)

410 (3.7)

2.0 2.6

12.2 13.4

3.4 4.0

68 16" 161 159 131" 35 (5.3)(1.3)(12.7)(12.5)(10.3)(2.8)

134 (10.5)

53 (4.2)

496 33 1,248 (4.5)(0.3)(11.1) 4.1 4.9

0.2 0.4

10.5 11.7

J 1,366 (12.3) 11.7 12.9

K

L

818 256 (7.4)(2.3) 6.9 7.9

O

X

420 56 (3.8)(0.5) 3.5 4.1

Total 11,124

0.4 0.6

26* 2 (2.0)(2.0)

0.95% CI

4.8 7.4

0.2 4.2

1.2 2.7

12.0 15.8

5.8 8.6

2.8 3.0

4.1 6.5

0.7 1.9

10.9 14.5

10.7 14.3

8.6 12.0

3.7 2.9

8.8 12.2

3.1 5.3

1.2 2.8

P

.025

.000

.643

.001 .202

.025

.171 .000

.174

.842

.000

.327

.037

.41

.002 .087

1,233

0.0 0.4

*Statistically significant. MRH, Medical Resource Hospital; Ptrans, patients transported; Pmrh, hospital destinations after MRH contact; CI, confidence interval.

TABLE 3. Relationship between all transports to the various metropolitan hospitals and patients diverted during MRH contact Hospital A No. of patients Ptrans (N)

B

C

D

895- 48 232 2,021 (8.0) (0.4)(2.1)(18.2)

95% Ct

7.5 8.5

0.3 0.5

No. of patients Pdivert (N)

1 3* (2.1) (6.4)

0.95% CI

0.0 11.3

1.3 17.5

,157

E

F

G

H

920 476 496 33 (8.3) (4.3) (4.5)(0.3)

1.8 2.4

17.5 18.9

7.8 8.8

3.9 4.7

4.1 4.9

0

7 (14.9)

3 1 4 (6,4) (2.1) (8.5)

0 7.6

6.2 28.3

1,3 17,5

0 2.4 1 1 . 3 20.4

. 0 0 0 . 3 2 2 .623

.663

.481 . 2 0 8 . 7 0 9

I

J

K

L

M (MRH)

1 , 2 4 8 1,366 818 256 1,429 (11.1) (12.3) (7.4) (2.3) (12.8)

0.2 0.4

10.5 11.7

0

9 (19.1)

0 7.6

11.7 12.9

6.9 7.9

2.0 2.6

12.2 t3.4

N

O

X

410 420 56 (3.7) (3.8) (0.5) 3.4 4.0

3.5 4.1

Total 11,124

0.4 0.6

3 2 3 5 ( 6 . 4 ) (4.2) (6.4) (10.6)

1 3 2* (2.1) (6.4) (4.2)

9.2 33.3

1.3 17.5

0.5 1.3 1 4 . 5 17.5

3.6 23.1

0 11.3

.138

.234

. 4 4 4 .069

.689

.582 3.74

47

1.3 0.5 17.5 14.5 .000

*Statistically significant (P < .003). MRH, Medical Resource Hospital; Ptrans, patients transported; Pdivert, patients diverted; CI, confidence interval.

lances stationed closest to the MRH were compared with the destinations of four ALS units, each of which was stationed closest to other hospitals in the northern, central, and eastern portions of the county. The proportions of patients transported to the closest hospital with and without MRH contact were examined to detect a higher proportion of transports to the MRH by units stationed close to the MRH. P < .05 was considered significant for this analysis.

RESULTS During the 28-week study period, 12,396 ambulance transports originated in Muhnomah County. These patients were distributed among 17 hospitals w i t h i n the t h r e e - c o u n t y metropolitan area. Of these transports, 1,272 (10.3%) generated an MRH c o n t a c t (Table 2). Of these 19:8 August 1990

1,272 MRH contacts, 47 (3.7%) documented MRH involvement in hospital diversions (Table 3). Five hospitals received a statistically significant (P < .003) proportion of MRH contact patients that was higher than their proportion of 911-dispatched patients would have predicted. Three that received a higher percentage were community hospitals in outlying areas. The remaining two were a large referral hospital and a smaller c o m m u n i t y hospital, both located in the urban area. The MRH base station hospital received its expected proportion. For the sample size used and the conservative c~-value of .003, there was a less than 17% chance that a 30% increase in transports to the base stat i o n h o s p i t a l w o u l d h a v e been missed. There were 47 hospital diversions Annals of Emergency Medicine

identified involving MRH. These calls originated from all quadrants of M u h n o m a h County and were distributed among 14 hospitals. Patient problem categories included altered mentation, anaphylaxis, cardiac disorders, obstetric disorders, overdose, respiratory distress, seizures, nontrauma-system injury, and " o t h e r " problems. Patients w i t h seizures were dfverted more than their proportion of total MRH calls would have predicted (P < .05) (Table 1). We also hypothesized that the proportion of transported patients each hospital received (Ptrans) would predict the proportion each hospital received of the 47 diverted patients (Pdivert). There was a statistically significant difference (P < .003) for one hospital that received more diverted patients than its Ptrans would have predicted. This hospital was 908/10t

BASE STATION Neely et al

also one of the o u t l y i n g facilities that received a higher proportion of M R H contact patients. T h e M R H f a c i l i t y received 10.5% of patients after M R H contact (Pmrh) and 10.6% of Pdivert (Table 3). Statistical significance was also noted for hospital X (Table 3), w h i c h represents three other facilities (each receiving too few 9 1 1 - d i s p a t c h e d p a t i e n t s to w a r r a n t its o w n identifier) and two p a t i e n t s d i v e r t e d during M R H contact. T h e M R H also received 12.8% of the total dispatch p o p u l a t i o n that did not require MRH contact (Ptrans). N o n e of t h e a m b u l a n c e s studied transported a significantly greater proportion of patients to the closest h o s p i t a l after M R H c o n t a c t (Table 4).

TABLE 4. Patients taken by specific a m b u l a n c e s to hospitals located closest to their stations

EMS Unit

Closest Hospital

Transports After MRH Contact (%)*

Transport Excluding MRH Contact (%)t

1

D

37/90 (40)

405/1,083 (37)

2

I

18/45(40)

272/800

(34)

3

d

36/93(39)

224/734

(31)

4

M

06/25 (24)

45/222

(20)

5

M

19/70 (27)

78/376

(21)

6

O

03/34 (09)

83/460

(18)

Hospital M is Medical Resource Hospital. There is no statistical significance between percent of transports after MRH contact and transports excluding MRH contact. *Numerator equals transports to closest hospital after MRH contact. Denominator equals total MRH contacts made by each unit. INumerator equals total transports (excluding MRH contacts) by each unit to its closest hospital. Denominator equals total transports made by each unit during the study period.

DISCUSSION T h i s study, w h i c h was f o l l o w i n g up on a study previously done in this c o m m u n i t y , 2 shows that a single regional base s t a t i o n does n o t necessarily directly or indirectly divert pat i e n t s to t h e f a c i l i t y o p e r a t i n g t h e base station. The finding that several o u t l y i n g f a c i l i t i e s received a higher p r o p o r t i o n of t r a n s p o r t s w i t h M R H contact suggests that both the param e d i c s and base s t a t i o n p h y s i c i a n s identified certain critical patients o r i g i n a t i n g in t h e o u t l y i n g areas as needing transport to closer hospitals. T h e single f a c i l i t y t h a t r e c e i v e d a higher percentage of patients specifically d i v e r t e d d u r i n g M R H c o n t a c t m a y have been a s t a t i s t i c a l outlier; o n l y t h r e e of 47 d i v e r t e d p a t i e n t s w e n t to t h a t f a c i l i t y . C o n s i d e r i n g v o l u m e , M R H d i r e c t i o n to d i v e r t critically ill patients did not greatly increase transports to that hospital. We c o n d u c t e d t h i s s t u d y in res p o n s e to p o l i t i c a l d i f f i c u l t i e s encountered during e s t a b l i s h m e n t of a single base station. We suspect other c o m m u n i t i e s also w i l l be p l a g u e d w i t h political suspicions and intrigue when they consider a single, regional base station. U n f o u n d e d a r g u m e n t s suggesting t h a t the single base station might significantly alter the h o s p i t a l d e s t i n a t i o n of p r e h o s p i t a l patients should be anticipated. Having operated a single urban EMS s y s t e m base station for several years, we have found numerous a d v a n t a g e s . A single group of b a s e station physicians is more likely to provide consistent on-line medical direction. 3 Moreover, we believe skill

102/909

and experience is necessary to comm u n i c a t e h e l p f u l i n f o r m a t i o n to paramedics during m o m e n t s of high stress. C o n t i n u e d exposure to onqine radio c o m m u n i c a t i o n s is n e c e s s a r y to u n d e r s t a n d the unique quality of radio t r a n s m i s s i o n s . G o o d l i s t e n i n g s k i l l s are e s p e c i a l l y n e c e s s a r y to c o m p r e h e n d a prehospital report, determine precisely what the param e d i c is asking, d e t e r m i n e w h a t the l i k e l y t r e a t m e n t options are, and det e r m i n e w h a t additional information is n e e d e d f r o m t h e p a r a m e d i c s to proceed w i t h t r e a t m e n t . These decisions are often m a d e in seconds. We also believe that an e l e m e n t of t r u s t is d e v e l o p e d w h e n ALS crews c o m m u n i c a t e to and become familiar w i t h t h e s a m e base s t a t i o n p h y s i cians. This trust facilitates decisions to carry out field t r e a t m e n t . Access i b i l i t y of o n - l i n e m e d i c a l a d v i c e data to all regional h e a l t h - c a r e providers also facilitates trust in the single base station concept. We find that p h y s i c i a n education is also easier w i t h fewer physicians and f a c i l i t i e s involved. Protocol changes are e a s i l y a s s i m i l a t e d by t h i s base station's 12 physicians. Data gathering and EMS s y s t e m research are easier to accomplish. Review of a single b a s e s t a t i o n d a t a base m a k e s EMS s y s t e m evaluation m o r e practical in this system. In our EMS system, concern about the n o n m e d i c a l influence of the single base station is alleviated by a performance-based contract w i t h the reg i o n a l EMS s y s t e m t h a t s p e l l s o u t s t a n d a r d s for p h y s i c i a n r e s p o n s e

Annals of Emergency Medicine

t i m e s to radio calls and base station p h y s i c i a n c o n t i n u i n g e d u c a t i o n and t h a t requires p a r a m e d i c conferences sponsored by M R H and quality assura n c e for M R H . In a d d i t i o n , it has been our experience that m a n y param e d i c s and h o s p i t a l e m e r g e n c y dep a r t m e n t s m o n i t o r t h e r a d i o frequency used by MRH; any inappropriate-sounding patient diversion to t h e base s t a t i o n h o s p i t a l w o u l d i m m e d i a t e l y be heard, thus providing a n o t h e r s y s t e m c h e c k a g a i n s t inappropriate diversions. CONCLUSION O u r regional single h o s p i t a l base s t a t i o n d i v e r t s few a m b u l a n c e patients; d i v e r t e d p a t i e n t s are n o t selectively or indirectly diverted to the base station hospital. We believe that advantages of a single base station include ease of research, physician education, consistency of on-line medical a d v i c e , q u a l i t y a s s u r a n c e , a n d higher level of p h y s i c i a n radio skills. Concerns about base station account a b i l i t y and i n a p p r o p r i a t e roles ass u m e d by a single base station can be alleviated through performance cont r a c t s and o t h e r s y s t e m - m o n i t o r i n g activities.

REFERENCES

1. American College of Emergency Physicians: Medical control of prehospital emergency medical services. Ann Emerg Med 1982;11:387. 2. Waddington N, Neely K, Barmache M, et ah The effect of on-line medical control centralization on ambulance destination. J Emerg Med 1987;5:299-303. 3. Thompson S, Schriver J: A survey of pre-hospital care paramedic/physician communication for Muhnomah County (Portland), Oregon. J Emerg Med 1984;i:412-428. 19:8 August 1990