ORIGINAL CONTRIBUTION cardiac arrest, prehospital; CPR, bystander
Prehospital Cardiac Arrest: The Impact of Witnessed Collapse and Bystander CPR in a Metropolitan EMS System With Short Response Times Objective: Numerous studies have shown initiation of bystander CPR to significantly improve survival from prehospitai cardiac arrest. However, in emergency medical services (EMS) systems with very short response times, bystander CPR has not been shown to impact outcome. The purpose of this study was to determine the effect of bystander CPR on survival from out-of-hospital cardiac arrest in such a system. Design: Prehospital, hospital, and death certificate data from a medium-sized metropolitan area were retrospectively analyzed for adult, nontraumatic cardiac arrest during a 16-month period. Results: A total of 298 patients met study criteria. One hundred ninetyfive arrests (65.4%) were witnessed, and 103 (34.6%) were unwitnessed. Twenty-five witnessed victims (12,8%) were discharged alive, whereas no unwitnessed victims survived (P < .001). Patients suffering a witnessed episode of ventricular fibrillation/tachycardia (VF/VT) were more likely to survive (21.9%) than were other patients (2.0%, P < .0001). Among witnessed patients, initiation of bystander CPR was associated with a significant improvement in survival (20.0%) compared with the no-bystander CPR group (9.2%, P < .05). Bystander CPR was also associated with improved outcome when witnessed patients with successful prehospital resuscitation were evaluated as a group; 18 had bystander CPR, of whom 13 (72.2%) survived compared with only 12 of 38 patients with no bystander CPR (31.6%, P < .01). Conclusion: Our data revealed improved survival rates when bystander CPR was initiated on victims of witnessed cardiac arrest in an EMS system with short response times. [Spaite DW, Hanlon T, Criss EA, Valenzuela TD, Wright AL, Keeley KT,, Meislin HW: Prehospital cardiac arrest: The impact of witnessed collapse and bystander CPR in a metropolitan EMS system with short response times. Ann Emerg Med November 1990;19:1264-1269.]
Daniel W Spaite, MD, FACEP* Teresa Hanlon, MD* Elizabeth A Criss, RN* Terence D Valenzuela, MD, FACEP*¢ A Larry Wright, PhDt Kevin T Keeley, CEP!: Harvey W Meislin, MD, FACEP* Tucson, Arizona From the Arizona Emergency Medicine Research Center, College of Medicine;* and Department of Mathematics,¢ University of Arizona; and the Tucson Fire Department,¢ Tucson, Arizona. Received for publication December 4, 1989. Revision received July 2, 1990. Accepted for publication July 12, 1990. Presented at the Annual Meeting of the National Association of EMS Physicians in San Francisco, June 1989, Address for reprints: Daniel W Spaite, MD, FACER Section of Emergency Medicine, Arizona Health Sciences Center, 1501 North Campbell, Tucson, Arizona 85724.
INTRODUCTION Survival from out-of-hospital cardiac arrest has been linked to rapid emergency medical services (EMS) response and early defibrillation. Mo Studies also demonstrate an improved outcome in witnessed events compared with unwitnessed events.Z,s, 9-14 The effect of initiation of CPR by lay-bystanders on outcome has also been evaluated.Z-4,9,13,ls-zo However, bystander CPR has not been shown to improve outcome in EMS systems with very short response times. 4 This study evaluated the effect of witnessed collapse and bystander CPR on the outcome of adults in nontraumatic cardiac arrest in such a system. METHODS Tucson, Arizona, is a medium-sized metropolitan area with a population of approximately 360,000. The Tucson Fire Department responds to all 911 calls requesting medical assistance within the city limits (149 square miles). An engine company with basic life support (BLS) personnel on board is dispatched for all medical complaints; if the nature of the call is such that advanced life support (ALS) may be required, a unit with two paramedics on board is dispatched simultaneously. There are 17 BLS and eight ALS units in the city with mean response times of 3.0 and 5.0 rain-
19:11 November t990
Annals of Emergency Medicine
1264/59
PREHOSPITAL CARDIAC ARREST Spaite et al
utes, respectively. Ninety-three percent of all ALS responses systemwide occur within eight minutes of dispatch. Response time is defined as the total elapsed time from the initial 911 call to the communications center until arrival of the unit onscene. Prehospital first-care forms are completed for all EMS encounters and provide extensive patient information. The data are subsequently checked for completeness and accuracy by paramedic supervisors and then manually entered into a mainf r a m e c o m p u t e r . This r e p o r t i n g mechanism, which is a modification of the Uniform Fire Incident Reporting System, has been reported in detail elsewhere. ~1 The data base contains extensive demographic information and medical parameters for each patient cared for by Tucson Fire Department personnel. The information is retrievable for any desired combination of variables. This analysis consisted of a retrospective evaluation of all episodes of adult (18 years old or older), nontraumatic cardiac arrest occurring during the 16-month period of June 1, 1987, through September 30, 1988, in which prehospital resuscitation was attempted. Patient data collected for this evaluation included age, sex, initial m o n i t o r e d r h y t h m , w h e t h e r event was witnessed, whether CPR was initiated by a bystander, and prehospital outcome. The initial monitored rhythm was interpreted by the paramedics and was n o t verified by a p h y s i c i a n . "Witnessed arrest" was defined as collapse seen or heard by someone. "Prehospital outcome," or patient's clinical status, was successful preh o s p i t a l r e s u s c i t a t i o n (return of spontaneous circulation in the field), unsuccessful prehospital resuscitation (no return of spontaneous circulation in the field), or resuscitation not attempted (in consultation with base station physician). Patients in w h o m r e s u s c i t a t i o n was not attempted (outcome 3) were excluded from the study. Survival was defined as being discharged alive from the hospital. This information was available from the statistics division of the Arizona Dep a r t m e n t of H e a l t h Services and from hospital records. Statistical evaluation consisted of X2 analysis (Yates' correction) with a 60/1265
TABLE 1. Successful prehospita] resuscitation and outcome for witnessed and unwitnessed cardiac arrest
Arrest
Successful Prehospital Resuscitation Patients N (%)
Witnessed 195 56 (28.7) Unwitnessed 103 2 (1.9) All patients 298 58 (19.5) *Left ED with spontaneous circulation.
Admitted to Hospital Alive* N (%)
Discharged Alive N (%)
48 (24.6) 1 (1.0) 49 (16.4)
25 (12.8) 0 (0) 25 (8.4)
TABLE 2. Associations between witnessed arrest, bystander CPR, prehospita] resuscitation, and outcome
Witnessed Arrest Yes Yes No No
Bystander CPR
No. of Patients
Yes No Yes No
65 130 21 82
No. With Successful Prehospital Resuscitation (%) 18 38 0 2
(27.7) (29.2) (0) (2.4)
No. Discharged Alive (%) 13 12 0 0
(20.0) (9.2) (0) (0)
TABLE 3. Association of variables with bystander CPR among witnessed arrest patients
Variable
Bystander CPR
No Bystander CPR
Mate N (%) 38/64 (59.4) 83/129 (64.3) Mean age (yr) 65.0 68.0 Mean response time (min) 4.6 4.8 Response time ~< 8 min (N) (%) 60/64 (93.7) 121/129 (93.8) Mean scene time (min) 13 7 14.9 VF/VT (N) (%) 36/64 (56.2) 59/129 (45.7) Intubation (N) (%) 52/64 (81.3) 104/129 (80.6) Defibrillation (N) (%) 32/64 (50.0) 65/129 (50.4) IV line (N) (%) 48/64 (75.0) 94/129 (72.9) Epinephrine (N) (%) 42/64 (65.6) 87/129 (67.4) Lidocaine (N) (%) 8/64 (12.5) 17/129 (13.2) Atropine (N) (%) 22/64 (34.4) 42/129 (32.6) VF/VT, initial rhythm of ventricular fibrillation or ventricular tachycardia.
P < .05 considered statistically significant. Annals of Emergency Medicine
P .608 .216 .645 .762 .170 .222 .929 .919 .886 .928 .924 .930
RESULTS Two hundred ninety-eight patients 19:11 November 1990
Initial Rhythms
Initial Monitored Rhythms 130 120 110 100 90 80 70 60 50 40 30 20 10 0
Witnessed vs Unwitnessed
60
50 ¢~ o
40 s0
13_ 2 0
10 VF
VT
Asystole
VF/VT
EMD
Rhythms
1
Rhythm
TABLE 4. Outcome among w~tnessed patients with successful prehospital resuscitation
Outcome
No. With Bystander CPR (%)
No. With No Bystander CPR (%)
Total (%)
Survived Died Total
13 (72.2) 5 (27.8) 18 (100)
12 (31.6) 26 (68.4) 38 (100)
25 (44.6) 31 (55.4) 56 (100)
met study criteria. One hundred eighty-eight patients (63.1%) were men, and 110 (36.9%) were women. Mean patient age was 67 years (range, 20 to 99 years). O n e h u n d r e d n i n e t y - f i v e arrests {65.4%) w e r e w i t n e s s e d , a n d 103 (34.6%) were unwitnessed. Patients w i t h o u t spontaneous circulation on arrival at the emergency department died regardless of whether their collapse was witnessed. Fifty-eight patients (19.5%) were alive on arrival at the ED (successful prehospital resuscitation). Of 195 w i t n e s s e d arrests, 28.7% were alive on arrival, whereas only 1.9% of 103 u n w i t n e s s e d patients were alive (P < .0001; Table 1). Witnessed patients were also m u c h m o r e likely to be a d m i t t e d to the hospital (P < .0001) and discharged alive (P < .001) than were u n w i t nessed patients; no unwitnessed victims of cardiac arrest survived to be discharged from the hospital. Bystander CPR was initiated on 86 patients (28.9%). T h e f r e q u e n c y of b y s t a n d e r CPR (as d o c u m e n t e d by the first arriving EMS unit) was significantly greater a m o n g witnessed patients than among unwitnessed 19:11 November 1990
Asystole
(33.3% vs 20.4%, respectively; P < .025). I n i t i a t i o n of b y s t a n d e r CPR was not associated with an increased likelihood of successful prehospital r e s u s c i t a t i o n a m o n g w i t n e s s e d patients (bystander CPR, 27.7%; no bystander CPR, 29.2%; P > .75; Table 2). However, bystander CPR was ass o c i a t e d w i t h an i m p r o v e m e n t in survival in witnessed patients (P .05). Comparison of numerous other demographic and treatment-related parameters revealed no differences between the CPR and no-CPR cohorts (Table 3). T h e o u t c o m e s of the 56 witnessed victims of cardiac arrest w h o were resuscitated successfully in the field are given (Table 4). In this group, patients receiving bystander CPR were m u c h more likely to survive ( 7 2 . 2 % ) t h a n were the no-bystander CPR patients (31.6%, P .01). The m o s t c o m m o n initial r h y t h m was ventricular fibrillation (VF), occurring in 127 patients (42.6%, Figure 1). Three patients (1.0%) were in ventricular tachycardia (VT). Witnessed patients were m o r e likely to be in VF/VT (49.2%) t h a n u n w i t n e s s e d Annals of Emergency Medicine
EMD
2
FIGURE 1. Cardiac rhythms of patients on arrival of paramedics are shown; 43.6% of patients were in VF or VT. FIGURE 2. Cardiac rhythms for witnessed and unwitnessed arrests are shown. Note that xadtnessed patients were more likely to be VF/VT and less likely to be in asystole than unwitnessed patients. v i c t i m s (33.0%, P < .01; Figure 2) and m u c h less likely to be in asystole (20.5%) t h a n u n w i t n e s s e d p a t i e n t s (43.7%, P < .0001). A trend toward increased frequency of VF/VT in patients receiving bystander CPR (52.3%) compared with patients not receiving bystander CPR (40.1%) was noted (P < .06; Figure 3). Initial r h y t h m was a significant predictor of survival (Figure 4 and Table 5). Witnessed victims of VF/VT were m u c h m o r e likely to survive (21.9%) than were witnessed patients w i t h i n i t i a l r h y t h m s of a s y s t o l e (2.5%, P < .01) or electromechanical dissociation (5.1%, P < .005). With all variables considered, the subset of patients m o s t likely to survive comprised witnessed victims of VF/VT in w h o m bystander CPR was initiated (30.6% vs 5.3%, P < .0001). DISCUSSION Prehospital cardiac arrest accounts for a vast n u m b e r of deaths each year in the United States. 2,22 A voluminous a m o u n t of literature exists regarding demographics, epidemiology, and factors that affect o u t c o m e for victims of sudden death. 1-6,9A3,22-28 Studies have s h o w n a u n i v e r s a l l y poor outcome for cardiac arrest vic~"~'~,,=uv~u
PREHOSPITAL CARDIAC ARREST Spaite et al
Initial R h y t h m s BCPR vs No BCPR
60
R h y t h m s A m o n g S u r v i v o r s of Witnessed Cardiac Arrest
30
50 20
4o o
30
#_ 2O 10 VF/VT
Asystole
O
EMD
Rhythms
FIGURE 3. Cardiac rhythms for pa-
tients with and without bystander CPR. There was a strong trend toward increased frequency of VF/VT in p a t i e n t s w i t h b y s t a n d e r CPR w h e n c o m p a r e d w i t h the no-bystander CPR group (P < .06). FIGURE 4. Percent survival for wit-
nessed patients with each presenting rhythm. *Note that witnessed victims of asystole or EMD were much less likely to survive than witnessed patients with an initial r h y t h m of VF/VT.
t i m s w i t h r h y t h m s other than VF or VT. 1 4,9,10,12,15,22,26,29-31 N u m e r o u s investigators have d e m o n s t r a t e d that the p r i m a r y s y s t e m c o m p o n e n t res u l t i n g i n s u c c e s s f u l o u t c o m e is rapid response of EMS personnel w h o c a n d e f i b r i l l a t e VF/VT. 1,2,7-12,30-33 O t h e r s y s t e m p a r a m e t e r s such as init i a t i o n of b y s t a n d e r CPR, w i t n e s s e d versus unwitnessed arrest, scene time, response time, and level of personnel training have also been studi e d . 1-6,9,1o,13,14,2o,23-26 H o w e v e r , these p a r a m e t e r s m a y vary in importance depending on m u l t i p l e systemspecific parameters. 16 In an effort to m o r e fully understand these issues, we evaluated the i m p a c t of two variables on the outcome of sudden death in an EMS syst e m w i t h short response times.
Witnessed Versus Unwitnessed Arrest T h e i n c i d e n c e of a d o c u m e n t e d w i t n e s s to cases of cardiac arrest has ranged from 41% to 82%.~,4,9,m, la,2o N u m e r o u s studies have reported im-
62/1267
~ VF/VT
Asystole*
EMD*
Rhythm
4
TABLE 5. Initial rhythms in patients with successful prehospita]
resuscitation
No. With Successful Prehospital Resuscitation (%)
Initial Rhythm VF/VT Asystole EMD Total
39 3 16 58
(67.2) (5.2) (27.6) (100)
No. Discharged Alive (%) 21 (84.0) 1 (4.0) 3 (12.0) 25 (100)
TABLE 6. Variables associated with witnessed arrest
Correlation
Variable
Positive Positive Positive Positive Positive Negative
Successful prehospital resuscitation Admitted alive to hospital Survival Bystander CPR VFNT Asystole
proved o u t c o m e for v i c t i m s of witn e s s e d collapse c o m p a r e d w i t h unw i t n e s s e d collapse.2,5,9~l¢ 34 S o m e investigators have studied only w i t n e s s e d arrest, a s s u m i n g t h a t ess e n t i a l l y all survivors are in this subgroup of patients. 1sA6,32 T h e variables associated w i t h witn e s s e d a r r e s t a r e g i v e n (Table 6). There was a very strong correlation b e t w e e n w i t n e s s e d a r r e s t and survival; all u n w i t n e s s e d v i c t i m s in our series died. T h e current literature reflects a belief that this is due to ear-
Annals of EmergencyMedicine
P < < < < <
Prehospital Cardiac Arrest: The Impact of Witnessed Collapse and Bystander CPR in a Metropolitan EMS System With Short Response Times Objective: Numerous studies have shown initiation of bystander CPR to significantly improve survival from prehospitai cardiac arrest. However, in emergency medical services (EMS) systems with very short response times, bystander CPR has not been shown to impact outcome. The purpose of this study was to determine the effect of bystander CPR on survival from out-of-hospital cardiac arrest in such a system. Design: Prehospital, hospital, and death certificate data from a medium-sized metropolitan area were retrospectively analyzed for adult, nontraumatic cardiac arrest during a 16-month period. Results: A total of 298 patients met study criteria. One hundred ninetyfive arrests (65.4%) were witnessed, and 103 (34.6%) were unwitnessed. Twenty-five witnessed victims (12,8%) were discharged alive, whereas no unwitnessed victims survived (P < .001). Patients suffering a witnessed episode of ventricular fibrillation/tachycardia (VF/VT) were more likely to survive (21.9%) than were other patients (2.0%, P < .0001). Among witnessed patients, initiation of bystander CPR was associated with a significant improvement in survival (20.0%) compared with the no-bystander CPR group (9.2%, P < .05). Bystander CPR was also associated with improved outcome when witnessed patients with successful prehospital resuscitation were evaluated as a group; 18 had bystander CPR, of whom 13 (72.2%) survived compared with only 12 of 38 patients with no bystander CPR (31.6%, P < .01). Conclusion: Our data revealed improved survival rates when bystander CPR was initiated on victims of witnessed cardiac arrest in an EMS system with short response times. [Spaite DW, Hanlon T, Criss EA, Valenzuela TD, Wright AL, Keeley KT,, Meislin HW: Prehospital cardiac arrest: The impact of witnessed collapse and bystander CPR in a metropolitan EMS system with short response times. Ann Emerg Med November 1990;19:1264-1269.]
Daniel W Spaite, MD, FACEP* Teresa Hanlon, MD* Elizabeth A Criss, RN* Terence D Valenzuela, MD, FACEP*¢ A Larry Wright, PhDt Kevin T Keeley, CEP!: Harvey W Meislin, MD, FACEP* Tucson, Arizona From the Arizona Emergency Medicine Research Center, College of Medicine;* and Department of Mathematics,¢ University of Arizona; and the Tucson Fire Department,¢ Tucson, Arizona. Received for publication December 4, 1989. Revision received July 2, 1990. Accepted for publication July 12, 1990. Presented at the Annual Meeting of the National Association of EMS Physicians in San Francisco, June 1989, Address for reprints: Daniel W Spaite, MD, FACER Section of Emergency Medicine, Arizona Health Sciences Center, 1501 North Campbell, Tucson, Arizona 85724.
INTRODUCTION Survival from out-of-hospital cardiac arrest has been linked to rapid emergency medical services (EMS) response and early defibrillation. Mo Studies also demonstrate an improved outcome in witnessed events compared with unwitnessed events.Z,s, 9-14 The effect of initiation of CPR by lay-bystanders on outcome has also been evaluated.Z-4,9,13,ls-zo However, bystander CPR has not been shown to improve outcome in EMS systems with very short response times. 4 This study evaluated the effect of witnessed collapse and bystander CPR on the outcome of adults in nontraumatic cardiac arrest in such a system. METHODS Tucson, Arizona, is a medium-sized metropolitan area with a population of approximately 360,000. The Tucson Fire Department responds to all 911 calls requesting medical assistance within the city limits (149 square miles). An engine company with basic life support (BLS) personnel on board is dispatched for all medical complaints; if the nature of the call is such that advanced life support (ALS) may be required, a unit with two paramedics on board is dispatched simultaneously. There are 17 BLS and eight ALS units in the city with mean response times of 3.0 and 5.0 rain-
19:11 November t990
Annals of Emergency Medicine
1264/59
PREHOSPITAL CARDIAC ARREST Spaite et al
utes, respectively. Ninety-three percent of all ALS responses systemwide occur within eight minutes of dispatch. Response time is defined as the total elapsed time from the initial 911 call to the communications center until arrival of the unit onscene. Prehospital first-care forms are completed for all EMS encounters and provide extensive patient information. The data are subsequently checked for completeness and accuracy by paramedic supervisors and then manually entered into a mainf r a m e c o m p u t e r . This r e p o r t i n g mechanism, which is a modification of the Uniform Fire Incident Reporting System, has been reported in detail elsewhere. ~1 The data base contains extensive demographic information and medical parameters for each patient cared for by Tucson Fire Department personnel. The information is retrievable for any desired combination of variables. This analysis consisted of a retrospective evaluation of all episodes of adult (18 years old or older), nontraumatic cardiac arrest occurring during the 16-month period of June 1, 1987, through September 30, 1988, in which prehospital resuscitation was attempted. Patient data collected for this evaluation included age, sex, initial m o n i t o r e d r h y t h m , w h e t h e r event was witnessed, whether CPR was initiated by a bystander, and prehospital outcome. The initial monitored rhythm was interpreted by the paramedics and was n o t verified by a p h y s i c i a n . "Witnessed arrest" was defined as collapse seen or heard by someone. "Prehospital outcome," or patient's clinical status, was successful preh o s p i t a l r e s u s c i t a t i o n (return of spontaneous circulation in the field), unsuccessful prehospital resuscitation (no return of spontaneous circulation in the field), or resuscitation not attempted (in consultation with base station physician). Patients in w h o m r e s u s c i t a t i o n was not attempted (outcome 3) were excluded from the study. Survival was defined as being discharged alive from the hospital. This information was available from the statistics division of the Arizona Dep a r t m e n t of H e a l t h Services and from hospital records. Statistical evaluation consisted of X2 analysis (Yates' correction) with a 60/1265
TABLE 1. Successful prehospita] resuscitation and outcome for witnessed and unwitnessed cardiac arrest
Arrest
Successful Prehospital Resuscitation Patients N (%)
Witnessed 195 56 (28.7) Unwitnessed 103 2 (1.9) All patients 298 58 (19.5) *Left ED with spontaneous circulation.
Admitted to Hospital Alive* N (%)
Discharged Alive N (%)
48 (24.6) 1 (1.0) 49 (16.4)
25 (12.8) 0 (0) 25 (8.4)
TABLE 2. Associations between witnessed arrest, bystander CPR, prehospita] resuscitation, and outcome
Witnessed Arrest Yes Yes No No
Bystander CPR
No. of Patients
Yes No Yes No
65 130 21 82
No. With Successful Prehospital Resuscitation (%) 18 38 0 2
(27.7) (29.2) (0) (2.4)
No. Discharged Alive (%) 13 12 0 0
(20.0) (9.2) (0) (0)
TABLE 3. Association of variables with bystander CPR among witnessed arrest patients
Variable
Bystander CPR
No Bystander CPR
Mate N (%) 38/64 (59.4) 83/129 (64.3) Mean age (yr) 65.0 68.0 Mean response time (min) 4.6 4.8 Response time ~< 8 min (N) (%) 60/64 (93.7) 121/129 (93.8) Mean scene time (min) 13 7 14.9 VF/VT (N) (%) 36/64 (56.2) 59/129 (45.7) Intubation (N) (%) 52/64 (81.3) 104/129 (80.6) Defibrillation (N) (%) 32/64 (50.0) 65/129 (50.4) IV line (N) (%) 48/64 (75.0) 94/129 (72.9) Epinephrine (N) (%) 42/64 (65.6) 87/129 (67.4) Lidocaine (N) (%) 8/64 (12.5) 17/129 (13.2) Atropine (N) (%) 22/64 (34.4) 42/129 (32.6) VF/VT, initial rhythm of ventricular fibrillation or ventricular tachycardia.
P < .05 considered statistically significant. Annals of Emergency Medicine
P .608 .216 .645 .762 .170 .222 .929 .919 .886 .928 .924 .930
RESULTS Two hundred ninety-eight patients 19:11 November 1990
Initial Rhythms
Initial Monitored Rhythms 130 120 110 100 90 80 70 60 50 40 30 20 10 0
Witnessed vs Unwitnessed
60
50 ¢~ o
40 s0
13_ 2 0
10 VF
VT
Asystole
VF/VT
EMD
Rhythms
1
Rhythm
TABLE 4. Outcome among w~tnessed patients with successful prehospital resuscitation
Outcome
No. With Bystander CPR (%)
No. With No Bystander CPR (%)
Total (%)
Survived Died Total
13 (72.2) 5 (27.8) 18 (100)
12 (31.6) 26 (68.4) 38 (100)
25 (44.6) 31 (55.4) 56 (100)
met study criteria. One hundred eighty-eight patients (63.1%) were men, and 110 (36.9%) were women. Mean patient age was 67 years (range, 20 to 99 years). O n e h u n d r e d n i n e t y - f i v e arrests {65.4%) w e r e w i t n e s s e d , a n d 103 (34.6%) were unwitnessed. Patients w i t h o u t spontaneous circulation on arrival at the emergency department died regardless of whether their collapse was witnessed. Fifty-eight patients (19.5%) were alive on arrival at the ED (successful prehospital resuscitation). Of 195 w i t n e s s e d arrests, 28.7% were alive on arrival, whereas only 1.9% of 103 u n w i t n e s s e d patients were alive (P < .0001; Table 1). Witnessed patients were also m u c h m o r e likely to be a d m i t t e d to the hospital (P < .0001) and discharged alive (P < .001) than were u n w i t nessed patients; no unwitnessed victims of cardiac arrest survived to be discharged from the hospital. Bystander CPR was initiated on 86 patients (28.9%). T h e f r e q u e n c y of b y s t a n d e r CPR (as d o c u m e n t e d by the first arriving EMS unit) was significantly greater a m o n g witnessed patients than among unwitnessed 19:11 November 1990
Asystole
(33.3% vs 20.4%, respectively; P < .025). I n i t i a t i o n of b y s t a n d e r CPR was not associated with an increased likelihood of successful prehospital r e s u s c i t a t i o n a m o n g w i t n e s s e d patients (bystander CPR, 27.7%; no bystander CPR, 29.2%; P > .75; Table 2). However, bystander CPR was ass o c i a t e d w i t h an i m p r o v e m e n t in survival in witnessed patients (P .05). Comparison of numerous other demographic and treatment-related parameters revealed no differences between the CPR and no-CPR cohorts (Table 3). T h e o u t c o m e s of the 56 witnessed victims of cardiac arrest w h o were resuscitated successfully in the field are given (Table 4). In this group, patients receiving bystander CPR were m u c h more likely to survive ( 7 2 . 2 % ) t h a n were the no-bystander CPR patients (31.6%, P .01). The m o s t c o m m o n initial r h y t h m was ventricular fibrillation (VF), occurring in 127 patients (42.6%, Figure 1). Three patients (1.0%) were in ventricular tachycardia (VT). Witnessed patients were m o r e likely to be in VF/VT (49.2%) t h a n u n w i t n e s s e d Annals of Emergency Medicine
EMD
2
FIGURE 1. Cardiac rhythms of patients on arrival of paramedics are shown; 43.6% of patients were in VF or VT. FIGURE 2. Cardiac rhythms for witnessed and unwitnessed arrests are shown. Note that xadtnessed patients were more likely to be VF/VT and less likely to be in asystole than unwitnessed patients. v i c t i m s (33.0%, P < .01; Figure 2) and m u c h less likely to be in asystole (20.5%) t h a n u n w i t n e s s e d p a t i e n t s (43.7%, P < .0001). A trend toward increased frequency of VF/VT in patients receiving bystander CPR (52.3%) compared with patients not receiving bystander CPR (40.1%) was noted (P < .06; Figure 3). Initial r h y t h m was a significant predictor of survival (Figure 4 and Table 5). Witnessed victims of VF/VT were m u c h m o r e likely to survive (21.9%) than were witnessed patients w i t h i n i t i a l r h y t h m s of a s y s t o l e (2.5%, P < .01) or electromechanical dissociation (5.1%, P < .005). With all variables considered, the subset of patients m o s t likely to survive comprised witnessed victims of VF/VT in w h o m bystander CPR was initiated (30.6% vs 5.3%, P < .0001). DISCUSSION Prehospital cardiac arrest accounts for a vast n u m b e r of deaths each year in the United States. 2,22 A voluminous a m o u n t of literature exists regarding demographics, epidemiology, and factors that affect o u t c o m e for victims of sudden death. 1-6,9A3,22-28 Studies have s h o w n a u n i v e r s a l l y poor outcome for cardiac arrest vic~"~'~,,=uv~u
PREHOSPITAL CARDIAC ARREST Spaite et al
Initial R h y t h m s BCPR vs No BCPR
60
R h y t h m s A m o n g S u r v i v o r s of Witnessed Cardiac Arrest
30
50 20
4o o
30
#_ 2O 10 VF/VT
Asystole
O
EMD
Rhythms
FIGURE 3. Cardiac rhythms for pa-
tients with and without bystander CPR. There was a strong trend toward increased frequency of VF/VT in p a t i e n t s w i t h b y s t a n d e r CPR w h e n c o m p a r e d w i t h the no-bystander CPR group (P < .06). FIGURE 4. Percent survival for wit-
nessed patients with each presenting rhythm. *Note that witnessed victims of asystole or EMD were much less likely to survive than witnessed patients with an initial r h y t h m of VF/VT.
t i m s w i t h r h y t h m s other than VF or VT. 1 4,9,10,12,15,22,26,29-31 N u m e r o u s investigators have d e m o n s t r a t e d that the p r i m a r y s y s t e m c o m p o n e n t res u l t i n g i n s u c c e s s f u l o u t c o m e is rapid response of EMS personnel w h o c a n d e f i b r i l l a t e VF/VT. 1,2,7-12,30-33 O t h e r s y s t e m p a r a m e t e r s such as init i a t i o n of b y s t a n d e r CPR, w i t n e s s e d versus unwitnessed arrest, scene time, response time, and level of personnel training have also been studi e d . 1-6,9,1o,13,14,2o,23-26 H o w e v e r , these p a r a m e t e r s m a y vary in importance depending on m u l t i p l e systemspecific parameters. 16 In an effort to m o r e fully understand these issues, we evaluated the i m p a c t of two variables on the outcome of sudden death in an EMS syst e m w i t h short response times.
Witnessed Versus Unwitnessed Arrest T h e i n c i d e n c e of a d o c u m e n t e d w i t n e s s to cases of cardiac arrest has ranged from 41% to 82%.~,4,9,m, la,2o N u m e r o u s studies have reported im-
62/1267
~ VF/VT
Asystole*
EMD*
Rhythm
4
TABLE 5. Initial rhythms in patients with successful prehospita]
resuscitation
No. With Successful Prehospital Resuscitation (%)
Initial Rhythm VF/VT Asystole EMD Total
39 3 16 58
(67.2) (5.2) (27.6) (100)
No. Discharged Alive (%) 21 (84.0) 1 (4.0) 3 (12.0) 25 (100)
TABLE 6. Variables associated with witnessed arrest
Correlation
Variable
Positive Positive Positive Positive Positive Negative
Successful prehospital resuscitation Admitted alive to hospital Survival Bystander CPR VFNT Asystole
proved o u t c o m e for v i c t i m s of witn e s s e d collapse c o m p a r e d w i t h unw i t n e s s e d collapse.2,5,9~l¢ 34 S o m e investigators have studied only w i t n e s s e d arrest, a s s u m i n g t h a t ess e n t i a l l y all survivors are in this subgroup of patients. 1sA6,32 T h e variables associated w i t h witn e s s e d a r r e s t a r e g i v e n (Table 6). There was a very strong correlation b e t w e e n w i t n e s s e d a r r e s t and survival; all u n w i t n e s s e d v i c t i m s in our series died. T h e current literature reflects a belief that this is due to ear-
Annals of EmergencyMedicine
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