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Unwitnessed Out-of-Hospital Cardiac Arrest: Is Resuscitation Worthwhile?
EMS/ORIGINAL CONTRIBUTION
Unwitnessed Out-of-Hospital Cardiac Arrest: Is Resuscitation Worthwhile? I
From the Helsinki Qty Emergency Medical Services, Helsinki, Finland.
Markku Kuisma,MD, MQ Kai Jaara, MD
Receivedfor publicationdune 25, 1996. Revision receiveddanuary 17, 1997. Acceptedfor publication February 5, 1997. Supported by the Laerdal Foundation and the Finnish Society of Intensive Care. Copyright © by the American College of Emergency Pt~ysicians.
Study objective: Todetermine the epidemiology of unwitnessed out-of-hospital cardiac arrest and the factors associated with survival after resuscitation using the Utstein style data collection. Methods: We conducted a prospective cohort study in a 525,000population city served by a single EMS system comprising a tiered response with physicians in the field. We studied consecutive unwitnessed out-of-hospital cardiac arrests that occurred between January 1, 1994, and December 31, 1995. We determined survival from cardiac arrest to discharge from hospital and the factors associated with survival. Results: Of the 809 patients for whom resuscitation was considered, 205 (25.3%) had sustained unwitnessed arrests. Cardiac origin of arrest was verified in 52% of cases, The most common noncardiac causes of arrest were trauma, intoxication, near-drowning, and hanging. In 150 patients (73.2%) the presenting rhythm was asystole, in 28 (13.6%)it was putseless electrical activity, and in 27 (13.2%) it was ventricular fibrillation. Resuscitation was attempted in 162 cases, 59 (36.4%) of whom demonstrated return of spontaneous circulation; 45 (27,8%) were hospitalized alive, and 8 (4.9%) were discharged. The survivors represented 6.7% of all out-of-hospital cardiac arrest survivors during the study period. Survival was most likely if patients presented with pulseless electrical activity; none of the patients with asystole of cardiac origin survived. Sex (P=.032), age (inverse relationship, P=.O004), scene of collapse (P=.042), and interval from call receipt to arrival of first responders (P=.004) were associated with survival. In a logistic-regression model, near-drowning remained an independent factor of survival (odds ratio, 15.5; 95% confidence interval, 1.2 to 200). A routine priority dispatching protocol differentiated cardiac arrest patients with survival potential from those who already had irreversible signs of death. Conclusion: This survey shows that survival after unwitnessed out-of-hospital cardiac arrest is unlikely with an initial response of basic life support alone. Withdrawal of resuscitation should be
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considered if an adult victim of unwitnessed cardiac arrest is found in asystole and the arrest is of obvious cardiac origin. [Kuisma M, Jaara K: Unwitnessed out-of-hospital cardiac arrest: Is resuscitation worthwhile? Ann EmergMedJuly 1997;30:6975.]
INTRODUCTION Witnessed collapse, in contrast to unwitnessed collapse, has been shown to be a major determinant of survival after sudden out-of-hospital cardiac arrest. 1-3 Patients who sustain unwitnessed arrests, in whom the survival rate is low despite the effort expended in resuscitation attempts, represent approximately one third of the total cardiac arrest population. 2 However, some subgroups among the population of unwitnessed cardiac arrest may benefit from resuscitation. In this study our goal was to report the epidemiology of unwitnessed cardiac arrest and factors associated with survival after resuscitation according to the Utstein style.4
MATERIALS AND METHODS HeMnki, the capital of Finland, has a population of 525,000 and a geographic area of 590 km 2. On workdays the population swells by approximately 10%. Approximately one third of the population is younger than 16 years (16%) or older than 65 years (13.9%). The Helsinki 112 Dispatching Center which receives calls for medical, fire, and rescue emergencies--dispatches 34,000 urgent medical calls annually.3 The center also serves the surrounding province of Uusimaa, increasing the population served to 1,000,000. Dispatch is criteria based and computer aided. The dispatchers, who are full-time employees, must pass a medical dispatching course. Most dispatchers can coach callers in performing CPR. Dispatching during the call is routinely used. The three-tiered EMS system is responsible for urgent calls. The system depends on close administrative and functional cooperation between the HeMnki City Rescue Department and the health authority. Nonurgent calls are addressed by two private enterprises. The city is divided into eight areas, each with its own rescue station. The first tier comprises seven ambulances and eight fire engines (used as first-responder units) staffed with EMTs capable of defibrillation, insertion of intravenous lines, and intubation of adult cardiac arrest victims. Members of the first-responder unit activate an automated electrical defibrillator on arrival at the patient's side to register the exact time at which they reached the patient. The defibrillator clocks are synchronized with
79
the time at the dispatching center; synchronization is checked daily. Three advanced life support (ALS) units staffed with EMTs trained at the ALS level make up the second tier. These EMTs are capable of administering intravenous medication. The third tier is the nontransporting, physician-staffed mobile ICU (MICU). One physician is always in the field in this EMS system. In addition to field work, physicians are responsible for medical direction, education, and qualityimprovement programs in the EMS system. The calls are classified in four categories; D, nonurgent; C, urgent cases in which the patient must be reached within 20 minutes (neither lights nor siren); B, urgent cases with medium or unknown risk (lights and siren; handled by basic life support [BLS] units, ALS units, or both); and A, high-risk calls (eg, severe chest pain, high-energy trauma, cardiac arrest), in which the nearest unit and the MICU are dispatched simultaneously The response times for first the responding units in A and B categories are the same. During simultaneous priority A calls, one of the ALS units (medical supervisor) is dispatched and the MICU informed. The MICU is responsible for 2,700 calls and 6,000 consultations each year. Resuscitation is conducted in accordance with the guidelines of American Heart Association.5 EMTs begin resuscitation when no irreversible signs of death are evident. Special education in the detection of death is provided for EMTs. Do-not-resuscitate (DNR) decisions are made by the physician on duty. Excluding hypothermia and trauma cases, patients are stabilized completely in the field, and efforts are ceased in the field when the patient demonstrates no response to resuscitation measures. Patients are transported to four receiving hospitals: two secondary and one tertiary care facility for adult patients and one tertiary care facility " for children. In cardiac arrest a first-responder unit and the MICU are dispatched (priority A) if the collapse is witnessed (or cannot be clearly proved to have been unwitnessed), in every case of pediatric cardiac arrest, variably in arrests of external origin (depending on estimated delays), and when bystanders have initiated CPR. Otherwise, in cases of unwitnessed cardiac arrest, only a first-response unit is dispatched (normally priority B, but when elbow rigor is present, priority C) with the assumption that irreversible signs of death are already present and the patient in question is not a candidate for resuscitation. This protocol, in use since late 1980s, is based on the Helsmki Cardiac Arrest Register. 6 The study plan was approved by the Ethics Committee of the Helsinki Health Department. All patients who sustained unwimessed out-of-hospital cardiac arrests within the city limits but with no irreversible signs of death (depen-
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dent lividity, rigor morris, decapitation, or decomposition), between January 1, 1994, and December 31, 1995, were included in the study. Cardiac arrest was classified as unwitnessed when the collapse was neither seen nor heard. Data were prospectively collected according to the Utstein style. 4 The MICU physician on duty completed a special study form during each event; the form was logged on the next weekday by the study investigators. In cases of simultaneous calls the forms were completed by the medical supervisor and the MICU physician together. Arrests were classified as having been el cardiac origin in the [ollowing circumstances: acute myocardial infarction, ischemic heart disease without acute myocardial damage, aortic stenosis, cardiomyopathy, or primary ventricular arrhythmia; if no cause for cardiac arrest was found during hospital examination or at autopsy. Arrest was classified as being of noncardiac origin on the basis of autopsy findings and hospital records (computed tomography scans, blood analysis). The times for the arrival of a first responding unit, the arrival of an ALS unit, and the arrival of the MICU at the patient's side, as well as the time elapsed before return of spontaneous circulation, were recorded. The moment of call receipt was registered as "time zero," whereas in the Utstdn recommendations time zero begins at the time of collapse. This modification, which is not yet a standard, was recently published and discussed. 6 All data were saved in a special computer file (StatView 4.0 for Macintosh). The end points of the study were death and survival to discharge. Data were obtained from hospital records by the investigators. The quality of secondary survival at the time of discharge was judged on the basis of overall performance category.4 Overall performance is divided into five categories: 1, good overall performance; 2, moderate overall disability; 3, severe overall disability; 4, vegetative state; and 5, death. Statistical analysis to detect factors related to survival was performed by a statistician. P values for background factors and confounders were calculated with the exact Z 2 test (nonparametric) and Student's t test (parametric). We applied an unconditional logistic-regression model for survivors of near-drowning with the use of the SAS program package. The following confounders were included in the model: age (>50 years/<50 years), sex, time elapsed before arrival of the first-response unit (>8 minutes/<8 minutes), and bystander CPR (no/yes). RESULTS
The total number of deaths from all causes in Helsinki during the study period was 1,012/100,000 inhabitants/year. Resuscitation was considered (no irreversible signs of death)
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for 809 out-of-hospital patients, 205 of whom (25.3%) sustained unwitnessed cardiac arrest. The mean_+SD age of the patients was 56.7+21.2 years; 144 (70.2%) were men. Eight (3.9%) were younger than 16 years. In 162 of the 205 cases, resuscitation was attempted, and 59 of the 162 (36.4%) demonstrated ROSC. Forty-five patients (27.8%) were hospitalized alive, and 8 (4.9°/0) were hospitalized and discharged. The median age of the survivors was 37.5 years. Of the eight survivors, five were discharged home with OPC 1, one to a rehabilitation center with OPC 2~ and two to a chronic care facility with OPC 3. Arrest was of cardiac origin in two survivors and brought on by neardrowning in three (two of them hypothermic), intoxication in two, and hanging in one. Three of the survivors were children (two near-drownings and the hanging case). Survivors of unwitnessed cardiac arrest represented 6.7% of the 120 survivors of out-of-hospital cardiac arrest during the study period. Figures 1 and 2 show the cardiac arrests on the Utstein template. Table 1.
Comparison of survival and resuscitation data in 162 cardiac arrest patients in whom resuscitation was attempted and collapse unwitnessed. Parameters
Survivors
Nonsurvivors
Sex Male Female
Age (years) [mean_+SD] Cause of arrest Cardiac Noncardiac
.032 3 5 32.4_+17.3
112 42 59.1_+20.6
2 6
9t 63
3 5
34 120
1 0 5 2
82 6 57 9
1 4 3
26 t08 19
Bystander CPR Yes No
.042
Initial rhythm VF Asystole PEA
.0004 .057
.311
Scene of collapse Home Work Public Health care facility
P
.132
Interval from call (minutes) [mean_+SD] To arrival of first-responder unit To arrival of ALS unit To arrival of MICU To ROSC
6.6_+1.3
8.5__+4.9
.004
11.7_+6.0 11.7_+6.0 21.4+13.0
13.2_+7.1 15,1_+7.8 19.8_+8.3
.554 .230 .448
~1",ventricuiartachycardia. Intervalswere calculatedfrom the time the call was receivedto the arrivalat the patient'saide.
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Table 1 describes the distributions of background factors and confounders between survival and death in the 162 patients in whom resuscitation was attempted. Sex (P=.032), age (an inverse relationship; P=.0004), scene of collapse (P=.042) and interval from call receipt to arrival of a firstresponse unit at the patient's side (P=.004) were associated with survival. In the logistic-regression model the odds ratio Figure 1.
Unwitnessed cardiac arrests, placed in the Utstetn template. ]
1. Populationservedby EMS ] N=525,000
V
2. Confirmedunwitnessedcardiac arrestsconsideredfor resuscitation N=205
and confidence interval for survivors of near-drowning in 162 patients--confounding by age, sex, time of arrival of a first-responder unit, and bystander CPR were 15.5 and 1.2 to 200, respectively. During the study period a first-responder unit only was dispatched for an unwitnessed cardiac arrest (see protocoI in Materials and Methods section) in 736 cases with the assumption that these patients would already have irreversible signs of death and therefore would not be candidates for CPR. The mean+-SD interval from call receipt to the arrival of a first-responder unit at the patient's side was 8.0+_4.5 minutes. The dispatching priority was B in 649 cases and C in 87. Of these patients, 718 (97.6%) had irreversible signs of death on the arrival of a first-responder unit. In the remaining 18 cases resuscitation was initiated because irreversible signs of death were not detected, but none of these patients survived. Arrest was of cardiac origin in 107 (52.2%) cases; a detailed list of causes is shown in Table 2. The presenting rhythm was ventd'cular fibrillation (VF) in 27 patients
4. Resuscitationattempted r
n=162
Figure 2.
Analysis of subgroup of unwitnessed cardiac arrests of noncardiac origin from Figure 1.
5. Cardiacorigin of arrest n=93
6. Non-cardiacorigin of arrest n=69
q
6. Noncardiacorigin of arrest J n=69
J
12. Initian=57rhythm lasystole
10. InitiaVE ln=24 rhythm
] 11. Init~rhythm n=O
~
~ 13. Other initial rhythms n=12 -
15. AchievedROSC n=34
~.
i ;rts
died in field
)
_
12. Initial rhythm asystole n=56
~_~
Initial rhythm VF n=3
er achievedROS0"~ n=44
11. InitiaTrhythm] V=T0 j
13.0t--her initialn=lrhythms O
[
~. AchievedROSC n=25
18.Admitte:=t; ICU/ward] ~ . Admittedto ICU/ward n=23 ]
~
V d in h
n=21
]
~
20. Dischargedalive / n=2
l
Subgroupanalysisfor black6 (noncardiacoriginof arrest)is presentedin Figure2.
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'V
I
20. Dischargedalive 1 n=6
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(13.2%), asystole in 150 (73.2%), and pulseless electrical activity (PEA) in 28 (13.6%), with survival rates of 3.7% (1 of 27), 3.6% (4 of 112), and 13.0% (3 of 23), respectively. None of the patients with cardiac arrest of cardiac origin and asystole as the initial rhythm survived. Collapse occurred at home in 110 patients, in a public place in 76, at work in 7, and in a health care facility in 12. Bystander CPR was initiated in 22.8% (37/162); 3 patients survived. The corresponding figure for the entire unwitnessed population was 20.0% (41 of 205). The mean_+SD intervals between call receipt and arrival of the first-responder unit, the ALS unit, and the MICU at the patient's side were 8.3+4.6, 12.8+6.9, and 14.5_+7.6 minutes, respectively. Time elapsed from call receipt to ROSC was 20.3+8.6 minutes. The patient received first-responder care within 7 minutes in 48% of cases and within 10 minutes in 79%. ALS care was rendered within 10 minutes in 43% of cases and within 15 minutes in 71%. In seven cases access to the patient was not available (locked door, patient underwater, or fire), and as a consequence intervals were prolonged. Resuscitation was not attempted, on the decision of the physician on duty. in 43 cases. The reason for the DNR order was severe trauma in 16 cases, estimated long collapse-tocall interval in 20, multiple chronic diseases (information provided by a patient card immediately available at home or by family members) in 4, and a combination of these factors in 3. DISCUSSION
Survival of unwitnessed out-of-hospital cardiac arrest was low (4.9% of patients were discharged alive from the hospital) as expected, although not so near zero as the rates in most studies (Table 3). The survivors represented a small subset of all survivors of out-of-hospital cardiac arrest (6.7%), in accordance with the findings of most previous studies. 2,3,~,s In only one study have the survivors of unwimessed cardiac arrest been reported to represent a remarkable proportion of all survivors, but the overall survival rate was low (10%) in that study as well. 9 It is notable that most of the survivors in our study had arrests of noncardiac origin. Neurologic sequelae were recorded in three of the eight survivors, although they might have occurred in all survivors as a result of the urLwimessed nature of the arrests and the consequent delays in the start of effective resuscitation efforts. Factors associated with survival in unwitnessed cardiac arrests have been studied in nursing home residents, lo None of the patients with unwitnessed arrests survived, compared with 12.5% of patients who had witnessed arrests. Resus-
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citation attempts were discouraged in unwitnessed cardiac arrests if the initial rhythm was asystole or electromechanical dissociation. In this study, age, female sex, time elapsed before arrival a first-responder unit, and scene of collapse were statistically significant variables on univariate analysis. On logistic regression, near-drowning remained an independent factor of survival but the confidence intervals were wide. The proportion of unwitnessed arrests of noncardiac origin was markedly higher than that in the general cardiac arrest population. 6 This is explained partly by the fact that suicide attempts (eg, intoxication [drug overdose or smoke inhalation] and hanging) are a substantial proportion of the unwimessed-arrest population. Asystole was the presenting rhythm in 73% of the patients in our study; only 13% had VE In one previous study the proportion of patients in whom VF was the initial rhythm was markedly higher. 2 This high percentage (33%) may be partly explained by the inclusion and definition criteria. Response intervals specific for different EMS systems are not believed to play a major role in the documented rhythm distribution of unwitnessed cardiac arrests. In our EMS system we have recorded VF as the initial rhythm in 65% of witnessed cardiac 6 (the overall incidence of VF is high despite relatively long mean response times--7.0 and 10.3 minutes for the first-responder and ALS units, respectively). Asystole recorded by first responders, especially in unwitnessed arrests of cardiac origin, is merely an indicator of a long interval between collapse and rhythm registration and, therefore, death. Table 2. Cat~ses of arrest in 205 unwitnessed out-of-hospital cardiac arrests. Cause of Arrest
No. (%)
Cardiac Noncardiac
107 (52.2) 98 (47,8)
Trauma Intoxication Near-drowning Hanging Nontraamatic bleeding* SIDS Carbon monoxide intoxication Pneumonia Choking Malignancy Pulmonaryembolism Other
21 (10,2) 16 (7.8) 10 (4.9) 10 (4.9) 7 (3.4) 5 (2.4) 5 (2,4) 5 (2.4) 4 (2.0) 4 (2.0) 3 (1.5) 8 (3.9)
SIDS, sudden infant death syndreme. *Aortic rupture or gastrointestinal bleeding.
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from prolonged cardiac arrest is not rare. In our study three of the survivors from all age groups were school-aged children. Most out-of-hospital cardiac arrests occur at home, but survival is more likely in arrests that occur outside the home. ~r Outside the home, arrests are more often witnessed, or at least detected more quickly, and the time elapsed before the start of CPR is shorter. In unwitnessed cardiac arrests occurring in public places in an urban environment, it might be speculated that survival potential is greater than that for the unwitnessed-arrest population as a whole because of earlier detection. This hypothesis was supported by our results; seven of the eight survivors had collapsed outside the home. The purpose of criteria-based dispatch is to dispatch an appropriate level of care on the basis of what has happened and the patient's status. The allocation of scarce ALS resources plays an important role. The authors of two recent studies showed the power of criteria-based dispatch in reducing futile ALS calls safely and in increasing the availability of units to incidents requiring ALS. 1s,~9 However, in cardiac arrests ALS is usually dispatched, and criteria-based dispatch has not been reported to have been used to limit response in cases of cardiac arrests. Our dispatching protocol has been in use in the Helsinki EMS system since the 1980s. In clearly unwitnessed adult cardiac arrests, m which CPR is not being performed, only BLS is dispatched. Without this priority dispatching, cardiac arrest calls for ALS units would be doubled and, consequently, their availability for other calls requiring ALS would be diminished. Only 2.4% of cases (n=18), classified as clearly unwitnessed with following BLS response, did not have secondary signs of
Survival was most likely (13%) when PEA was the first rhythm recorded. In a large series from Gothenburg, Sweden, 2% of patients survived to discharge. 1t In another recent study, survival was 6.9% for patients with an initial rhythm of PEA. t2 It seems that the probabilities of survival according to initial rhythm in witnessed cases do not directly apply to unwitnessed arrests. Response time intervals in this study were longer than those in most urban US EMS systems; this could negatively affect survival rates. On the other hand, survival of bystanderwitnessed VF of cardiac origin in the same EMS system was 32.5% in 1994, 6 a rate not much different from that reported from Seattle33 One major reason for long response times is the recording system used. In almost every previous study timing has ended when the unit has arrived at the scene, whereas in this study the end point was arrival at the patient's side. The interval between scene arrival and arrival at the patient's side can be relatively lengthy for various reasons (muhistory buildings, locked doors, no guidance). Patients who sustain unwitnessed cardiac arrests are not as likely to receive bystander-initiated CPR as patients who sustain witnessed arrests. 2 In our study, bystander CPR was not a prognostic factor, although bystander CPR was found in one report to independently influence survival in unwitnessed cardiac arrest. > It seems bystander CPR is most effective in witnessed arrests of cardiac origin in maintaining the heart in VF until defibrillation and other definitive treatments can be performed. >5 In pediatric cardiac arrest, unwitnessed collapse is not a negative prognostic factor, and almost half the survivors have sustained unwitnessed arrests. ~6 The brains of children are not as sensitive to hypoxia as adult brains, and recovery Table 3.
Previous studies with data o/unwitnessed out-@hospital cardiac arrest.
Study Stueven eta[, 19899 Spaite et al, 1 9 9 0 2 Becket et al, 19913 Lembardi et al, 19947 Grubb et al, 19958
Inclusion Criteria All adult cardiac arrests but those caused by trauma and poisoning Nontraumatic adult cardiac arrests Adult cardiac arrests of cardiac origin Adult cardiac arrests of cardiac origin Patients hospitalized alive
Sample Size
% of All Cardiac Arrests
No. Admitted to Hospital (%)
No. Discharged
Proportionof All
(%)
2,311
54.8
NA
Survivors (%)
230 {10.0)
230/533 (43.2)
103
34.6
1 (1.0)
0
(]/25 (0)
1,445
44.9
NA
4 (.3)
4/55 (7.2)
788
33.8
NA
3 (.4)
3/52 (5.8)
21
10.6"
21 (NA)
7 (NA)
7/83 (8.4)
NA, not available. *Proportioncalculatedfrom the patientsadmittedto the hospital. Calculationshavebeenmadeon the basisof figures givenin these publications.
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death on arrival of a first responding unit, and the first responding unit had to ask for ALS. Subgroup analysis revealed that only one patient might have benefitted from an earlier ALS response. That analysis was based on the Helsinki Cardiac Arrest Register; each patient's initial rhythm, any delays, and the cause of cardiac arrest were retrospectively compared with the register data from survivors in this EMS system. However, the protocol was not studied in a controlled fashion and therefore recommendations concerning dispatching cannot be given on the basis of this study's findings. A controlled study is needed to investigate whether ALS resources can be allocated cost-effectively and safely in cardiac arrests. In our study, resuscitation was not initiated, on the decision of the physician on duty, in 21% of unwitnessed cases. None of these patients had a prewritten DNR order, and the DNR decision was based on survival potential (eg, disease history and delays before the arrival of EMS personnel). In our opinion the medical directors of EMS systems should consider giving DNR instructions for patients in categories that, under current knowledge, have no chance of survival. One such group, as shown by our findings, is unwitnessed adult cardiac arrest patients with arrest of obvious cardiac origin who present with asystole as the initial rhythm and who have prolonged response times. Our survey shows that survival after unwitnessed out-ofhospital cardiac arrest is unlikely with BLS-only initial response unless the cause of arrest is near-drowning or the patient is a child. Withdrawal of resuscitation should be considered if an adult victim of unwitnessed cardiac arrest is found in asystole and the arrest is obviously of cardiac origin. We found the Utstein style of data reporting applicable for the collection of data from unwitnessed out-ofhospital cardiac arrests. Originally unwitnessed, as well as noncardiac, arrests are classified as exit categories in the Utstein recommendations. 4 We chose to present the unwitnessed-arrest subgroup also in the template model to produce comparable data of this subset, in which approximately one third of out-of-hospital CPR resources are invested.
5. American Heart Association: Guidelines far cardiopu/monaryresuscitation and emergencycardiac care: Recommendationsof the 1992 national conference. JAMA 1992;268:2251-2275. 6. Kuisma M, M9~tt~ T: Out-of-hospital cardiac arrests in Helsinki: Utstain style reporting. Heart 1996;76:18-23. 7. Lambardi G, Gallagher J, Gennis P: Outcome of out-of-hospitat cardiac arrest in New York City: The pre-hespital arrest survival evaluation {PHASE)study. JAMA 1994;271:678-683. 8. Grubb NR, Elten RA, Fox KAA: In-hospital mortality after out-of-hospital cardiac arrest. Lancet 1995;346:417-421. 9. Stueven HA, Waite EM, Traiane P, et al: Prehospital cardiac arrest; A critical analysis of factors affecting survival. Resuscitation1989;17:251-259. 10. Ghusn HF, Teasdale TA, Pope PE, et ab Older nursing home residents have cardiac arrest survival rate similar to that of older persons living in the community. J Am GeriatrSac 1995;43:520527. 11. Herlitz J, Ekstr6m L, Wennerblom B, et ab Survival among patients with out-of-hospital cardiac arrest found in electromechanical dissociation. Resuscitation1995;29:97-106. 12. Pepa PE, Levine RL, Fromm RE, at al: Cardiac arrest presenting with rhythms other than ventricular fibrillation: Contribution of resuscitative efforts toward total survivership. Crit CareMefl 1993;21:1838-1843. 13. EisenbergMS, Cummins RO, Larsee MP: Numerators, denominators, and survival rates: Reporting survival from out-of-hospital cardiac arrest. Am J ErnergMed 1991;9:544-546. 14. Martens PR, Mullie A, Calle P, et al: Influence on outcome after cardiac arrest of time elapsed between call for help and start of bystander basic CPR.Resuscitation1993;25:227-234. 15. Swor RA, Jackson RE, Cynar M. et al: Bystander CPR,ventricular fibrillation, and survival in witnessed, unmonitored out-of-hospital cardiac arrest. Ann EmergMed 1995;25:780-784. 16. Kuisma M, Suominen P, Korpela R: Paediatric cut-of-hospital cardiac arrests: Epidemioiagy and outcome. Resuscitation1995;30:141-150. 17, Litwin PE, EisenbergMS, Hallstrom AP, et ab The location of collapse and its effect on survival from cardiac arrest. Ann EmergMed 1987;16:787-791. 18, CurkaPA, PepePE, Ginger VF, et ah Emergencymedical services priority dispatch. Ann Emerg Med 1993;22:1688-1695. 19. Culley LL, Henwood OK, Clark JJ, et al: Increasing the efficiency of emergencymedical services by using criteria based dispatch. Ann EmergMef11994;24:867-872. We thank Per Rosenberg, MD, PhD, for valuable comments; Anneli Ojaj~Jrvi, MSc, for statistical review; and the Laerdal Foundation and Finnish Society of Intensive Care for financial support.
Reprint no. 47/1/81675 Address for reprints: Markku Kuisma, MD, MQ Helsinki City EMS Agricolankatu 15 A FINO0530 Helsinki Finland
REFERENCES 1. EisenbergMS, Hadas E, Nuri I, et al: Sudden cardiac arrest in Israeb Factors associated with successful resuscitation. Am J EmergMed 1988;4:319-323. 2. Spaite DW, Haolon T, Criss EA, et ab Prehospital cardiac arrest: The impact of witnessed collapse and bystander CPR in a metropolitan EMS system with short response times. Ann Emerg Meal1990,19:1264-1269. 3. Becker LB, Ostrander MP, BaiTott J, et al: Outcome of CPR in a large metropolitan area: Where are the survivors?Ann EmergMed 1991;29:355-361. 4. Cummins RO, Chamberlain DA, Abramsen NS, et al: Recommendedguidelines for uniform reporting of data from out-of-hospital cardiac arrest: The Utstein style. Ann EmergMed 1991;20:861-874.
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Unwitnessed Out-of-Hospital Cardiac Arrest: Is Resuscitation Worthwhile? I
From the Helsinki Qty Emergency Medical Services, Helsinki, Finland.
Markku Kuisma,MD, MQ Kai Jaara, MD
Receivedfor publicationdune 25, 1996. Revision receiveddanuary 17, 1997. Acceptedfor publication February 5, 1997. Supported by the Laerdal Foundation and the Finnish Society of Intensive Care. Copyright © by the American College of Emergency Pt~ysicians.
Study objective: Todetermine the epidemiology of unwitnessed out-of-hospital cardiac arrest and the factors associated with survival after resuscitation using the Utstein style data collection. Methods: We conducted a prospective cohort study in a 525,000population city served by a single EMS system comprising a tiered response with physicians in the field. We studied consecutive unwitnessed out-of-hospital cardiac arrests that occurred between January 1, 1994, and December 31, 1995. We determined survival from cardiac arrest to discharge from hospital and the factors associated with survival. Results: Of the 809 patients for whom resuscitation was considered, 205 (25.3%) had sustained unwitnessed arrests. Cardiac origin of arrest was verified in 52% of cases, The most common noncardiac causes of arrest were trauma, intoxication, near-drowning, and hanging. In 150 patients (73.2%) the presenting rhythm was asystole, in 28 (13.6%)it was putseless electrical activity, and in 27 (13.2%) it was ventricular fibrillation. Resuscitation was attempted in 162 cases, 59 (36.4%) of whom demonstrated return of spontaneous circulation; 45 (27,8%) were hospitalized alive, and 8 (4.9%) were discharged. The survivors represented 6.7% of all out-of-hospital cardiac arrest survivors during the study period. Survival was most likely if patients presented with pulseless electrical activity; none of the patients with asystole of cardiac origin survived. Sex (P=.032), age (inverse relationship, P=.O004), scene of collapse (P=.042), and interval from call receipt to arrival of first responders (P=.004) were associated with survival. In a logistic-regression model, near-drowning remained an independent factor of survival (odds ratio, 15.5; 95% confidence interval, 1.2 to 200). A routine priority dispatching protocol differentiated cardiac arrest patients with survival potential from those who already had irreversible signs of death. Conclusion: This survey shows that survival after unwitnessed out-of-hospital cardiac arrest is unlikely with an initial response of basic life support alone. Withdrawal of resuscitation should be
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considered if an adult victim of unwitnessed cardiac arrest is found in asystole and the arrest is of obvious cardiac origin. [Kuisma M, Jaara K: Unwitnessed out-of-hospital cardiac arrest: Is resuscitation worthwhile? Ann EmergMedJuly 1997;30:6975.]
INTRODUCTION Witnessed collapse, in contrast to unwitnessed collapse, has been shown to be a major determinant of survival after sudden out-of-hospital cardiac arrest. 1-3 Patients who sustain unwitnessed arrests, in whom the survival rate is low despite the effort expended in resuscitation attempts, represent approximately one third of the total cardiac arrest population. 2 However, some subgroups among the population of unwitnessed cardiac arrest may benefit from resuscitation. In this study our goal was to report the epidemiology of unwitnessed cardiac arrest and factors associated with survival after resuscitation according to the Utstein style.4
MATERIALS AND METHODS HeMnki, the capital of Finland, has a population of 525,000 and a geographic area of 590 km 2. On workdays the population swells by approximately 10%. Approximately one third of the population is younger than 16 years (16%) or older than 65 years (13.9%). The Helsinki 112 Dispatching Center which receives calls for medical, fire, and rescue emergencies--dispatches 34,000 urgent medical calls annually.3 The center also serves the surrounding province of Uusimaa, increasing the population served to 1,000,000. Dispatch is criteria based and computer aided. The dispatchers, who are full-time employees, must pass a medical dispatching course. Most dispatchers can coach callers in performing CPR. Dispatching during the call is routinely used. The three-tiered EMS system is responsible for urgent calls. The system depends on close administrative and functional cooperation between the HeMnki City Rescue Department and the health authority. Nonurgent calls are addressed by two private enterprises. The city is divided into eight areas, each with its own rescue station. The first tier comprises seven ambulances and eight fire engines (used as first-responder units) staffed with EMTs capable of defibrillation, insertion of intravenous lines, and intubation of adult cardiac arrest victims. Members of the first-responder unit activate an automated electrical defibrillator on arrival at the patient's side to register the exact time at which they reached the patient. The defibrillator clocks are synchronized with
79
the time at the dispatching center; synchronization is checked daily. Three advanced life support (ALS) units staffed with EMTs trained at the ALS level make up the second tier. These EMTs are capable of administering intravenous medication. The third tier is the nontransporting, physician-staffed mobile ICU (MICU). One physician is always in the field in this EMS system. In addition to field work, physicians are responsible for medical direction, education, and qualityimprovement programs in the EMS system. The calls are classified in four categories; D, nonurgent; C, urgent cases in which the patient must be reached within 20 minutes (neither lights nor siren); B, urgent cases with medium or unknown risk (lights and siren; handled by basic life support [BLS] units, ALS units, or both); and A, high-risk calls (eg, severe chest pain, high-energy trauma, cardiac arrest), in which the nearest unit and the MICU are dispatched simultaneously The response times for first the responding units in A and B categories are the same. During simultaneous priority A calls, one of the ALS units (medical supervisor) is dispatched and the MICU informed. The MICU is responsible for 2,700 calls and 6,000 consultations each year. Resuscitation is conducted in accordance with the guidelines of American Heart Association.5 EMTs begin resuscitation when no irreversible signs of death are evident. Special education in the detection of death is provided for EMTs. Do-not-resuscitate (DNR) decisions are made by the physician on duty. Excluding hypothermia and trauma cases, patients are stabilized completely in the field, and efforts are ceased in the field when the patient demonstrates no response to resuscitation measures. Patients are transported to four receiving hospitals: two secondary and one tertiary care facility for adult patients and one tertiary care facility " for children. In cardiac arrest a first-responder unit and the MICU are dispatched (priority A) if the collapse is witnessed (or cannot be clearly proved to have been unwitnessed), in every case of pediatric cardiac arrest, variably in arrests of external origin (depending on estimated delays), and when bystanders have initiated CPR. Otherwise, in cases of unwitnessed cardiac arrest, only a first-response unit is dispatched (normally priority B, but when elbow rigor is present, priority C) with the assumption that irreversible signs of death are already present and the patient in question is not a candidate for resuscitation. This protocol, in use since late 1980s, is based on the Helsmki Cardiac Arrest Register. 6 The study plan was approved by the Ethics Committee of the Helsinki Health Department. All patients who sustained unwimessed out-of-hospital cardiac arrests within the city limits but with no irreversible signs of death (depen-
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dent lividity, rigor morris, decapitation, or decomposition), between January 1, 1994, and December 31, 1995, were included in the study. Cardiac arrest was classified as unwitnessed when the collapse was neither seen nor heard. Data were prospectively collected according to the Utstein style. 4 The MICU physician on duty completed a special study form during each event; the form was logged on the next weekday by the study investigators. In cases of simultaneous calls the forms were completed by the medical supervisor and the MICU physician together. Arrests were classified as having been el cardiac origin in the [ollowing circumstances: acute myocardial infarction, ischemic heart disease without acute myocardial damage, aortic stenosis, cardiomyopathy, or primary ventricular arrhythmia; if no cause for cardiac arrest was found during hospital examination or at autopsy. Arrest was classified as being of noncardiac origin on the basis of autopsy findings and hospital records (computed tomography scans, blood analysis). The times for the arrival of a first responding unit, the arrival of an ALS unit, and the arrival of the MICU at the patient's side, as well as the time elapsed before return of spontaneous circulation, were recorded. The moment of call receipt was registered as "time zero," whereas in the Utstdn recommendations time zero begins at the time of collapse. This modification, which is not yet a standard, was recently published and discussed. 6 All data were saved in a special computer file (StatView 4.0 for Macintosh). The end points of the study were death and survival to discharge. Data were obtained from hospital records by the investigators. The quality of secondary survival at the time of discharge was judged on the basis of overall performance category.4 Overall performance is divided into five categories: 1, good overall performance; 2, moderate overall disability; 3, severe overall disability; 4, vegetative state; and 5, death. Statistical analysis to detect factors related to survival was performed by a statistician. P values for background factors and confounders were calculated with the exact Z 2 test (nonparametric) and Student's t test (parametric). We applied an unconditional logistic-regression model for survivors of near-drowning with the use of the SAS program package. The following confounders were included in the model: age (>50 years/<50 years), sex, time elapsed before arrival of the first-response unit (>8 minutes/<8 minutes), and bystander CPR (no/yes). RESULTS
The total number of deaths from all causes in Helsinki during the study period was 1,012/100,000 inhabitants/year. Resuscitation was considered (no irreversible signs of death)
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for 809 out-of-hospital patients, 205 of whom (25.3%) sustained unwitnessed cardiac arrest. The mean_+SD age of the patients was 56.7+21.2 years; 144 (70.2%) were men. Eight (3.9%) were younger than 16 years. In 162 of the 205 cases, resuscitation was attempted, and 59 of the 162 (36.4%) demonstrated ROSC. Forty-five patients (27.8%) were hospitalized alive, and 8 (4.9°/0) were hospitalized and discharged. The median age of the survivors was 37.5 years. Of the eight survivors, five were discharged home with OPC 1, one to a rehabilitation center with OPC 2~ and two to a chronic care facility with OPC 3. Arrest was of cardiac origin in two survivors and brought on by neardrowning in three (two of them hypothermic), intoxication in two, and hanging in one. Three of the survivors were children (two near-drownings and the hanging case). Survivors of unwitnessed cardiac arrest represented 6.7% of the 120 survivors of out-of-hospital cardiac arrest during the study period. Figures 1 and 2 show the cardiac arrests on the Utstein template. Table 1.
Comparison of survival and resuscitation data in 162 cardiac arrest patients in whom resuscitation was attempted and collapse unwitnessed. Parameters
Survivors
Nonsurvivors
Sex Male Female
Age (years) [mean_+SD] Cause of arrest Cardiac Noncardiac
.032 3 5 32.4_+17.3
112 42 59.1_+20.6
2 6
9t 63
3 5
34 120
1 0 5 2
82 6 57 9
1 4 3
26 t08 19
Bystander CPR Yes No
.042
Initial rhythm VF Asystole PEA
.0004 .057
.311
Scene of collapse Home Work Public Health care facility
P
.132
Interval from call (minutes) [mean_+SD] To arrival of first-responder unit To arrival of ALS unit To arrival of MICU To ROSC
6.6_+1.3
8.5__+4.9
.004
11.7_+6.0 11.7_+6.0 21.4+13.0
13.2_+7.1 15,1_+7.8 19.8_+8.3
.554 .230 .448
~1",ventricuiartachycardia. Intervalswere calculatedfrom the time the call was receivedto the arrivalat the patient'saide.
71
UNWITNESSED ARREST
Kuisma&Jaara
im
Table 1 describes the distributions of background factors and confounders between survival and death in the 162 patients in whom resuscitation was attempted. Sex (P=.032), age (an inverse relationship; P=.0004), scene of collapse (P=.042) and interval from call receipt to arrival of a firstresponse unit at the patient's side (P=.004) were associated with survival. In the logistic-regression model the odds ratio Figure 1.
Unwitnessed cardiac arrests, placed in the Utstetn template. ]
1. Populationservedby EMS ] N=525,000
V
2. Confirmedunwitnessedcardiac arrestsconsideredfor resuscitation N=205
and confidence interval for survivors of near-drowning in 162 patients--confounding by age, sex, time of arrival of a first-responder unit, and bystander CPR were 15.5 and 1.2 to 200, respectively. During the study period a first-responder unit only was dispatched for an unwitnessed cardiac arrest (see protocoI in Materials and Methods section) in 736 cases with the assumption that these patients would already have irreversible signs of death and therefore would not be candidates for CPR. The mean+-SD interval from call receipt to the arrival of a first-responder unit at the patient's side was 8.0+_4.5 minutes. The dispatching priority was B in 649 cases and C in 87. Of these patients, 718 (97.6%) had irreversible signs of death on the arrival of a first-responder unit. In the remaining 18 cases resuscitation was initiated because irreversible signs of death were not detected, but none of these patients survived. Arrest was of cardiac origin in 107 (52.2%) cases; a detailed list of causes is shown in Table 2. The presenting rhythm was ventd'cular fibrillation (VF) in 27 patients
4. Resuscitationattempted r
n=162
Figure 2.
Analysis of subgroup of unwitnessed cardiac arrests of noncardiac origin from Figure 1.
5. Cardiacorigin of arrest n=93
6. Non-cardiacorigin of arrest n=69
q
6. Noncardiacorigin of arrest J n=69
J
12. Initian=57rhythm lasystole
10. InitiaVE ln=24 rhythm
] 11. Init~rhythm n=O
~
~ 13. Other initial rhythms n=12 -
15. AchievedROSC n=34
~.
i ;rts
died in field
)
_
12. Initial rhythm asystole n=56
~_~
Initial rhythm VF n=3
er achievedROS0"~ n=44
11. InitiaTrhythm] V=T0 j
13.0t--her initialn=lrhythms O
[
~. AchievedROSC n=25
18.Admitte:=t; ICU/ward] ~ . Admittedto ICU/ward n=23 ]
~
V d in h
n=21
]
~
20. Dischargedalive / n=2
l
Subgroupanalysisfor black6 (noncardiacoriginof arrest)is presentedin Figure2.
72
'V
I
20. Dischargedalive 1 n=6
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UNWITNESSED ARREST Kuisma & Jaara
i
(13.2%), asystole in 150 (73.2%), and pulseless electrical activity (PEA) in 28 (13.6%), with survival rates of 3.7% (1 of 27), 3.6% (4 of 112), and 13.0% (3 of 23), respectively. None of the patients with cardiac arrest of cardiac origin and asystole as the initial rhythm survived. Collapse occurred at home in 110 patients, in a public place in 76, at work in 7, and in a health care facility in 12. Bystander CPR was initiated in 22.8% (37/162); 3 patients survived. The corresponding figure for the entire unwitnessed population was 20.0% (41 of 205). The mean_+SD intervals between call receipt and arrival of the first-responder unit, the ALS unit, and the MICU at the patient's side were 8.3+4.6, 12.8+6.9, and 14.5_+7.6 minutes, respectively. Time elapsed from call receipt to ROSC was 20.3+8.6 minutes. The patient received first-responder care within 7 minutes in 48% of cases and within 10 minutes in 79%. ALS care was rendered within 10 minutes in 43% of cases and within 15 minutes in 71%. In seven cases access to the patient was not available (locked door, patient underwater, or fire), and as a consequence intervals were prolonged. Resuscitation was not attempted, on the decision of the physician on duty. in 43 cases. The reason for the DNR order was severe trauma in 16 cases, estimated long collapse-tocall interval in 20, multiple chronic diseases (information provided by a patient card immediately available at home or by family members) in 4, and a combination of these factors in 3. DISCUSSION
Survival of unwitnessed out-of-hospital cardiac arrest was low (4.9% of patients were discharged alive from the hospital) as expected, although not so near zero as the rates in most studies (Table 3). The survivors represented a small subset of all survivors of out-of-hospital cardiac arrest (6.7%), in accordance with the findings of most previous studies. 2,3,~,s In only one study have the survivors of unwimessed cardiac arrest been reported to represent a remarkable proportion of all survivors, but the overall survival rate was low (10%) in that study as well. 9 It is notable that most of the survivors in our study had arrests of noncardiac origin. Neurologic sequelae were recorded in three of the eight survivors, although they might have occurred in all survivors as a result of the urLwimessed nature of the arrests and the consequent delays in the start of effective resuscitation efforts. Factors associated with survival in unwitnessed cardiac arrests have been studied in nursing home residents, lo None of the patients with unwitnessed arrests survived, compared with 12.5% of patients who had witnessed arrests. Resus-
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3 0 : 1 ANNALS OF EMERGENCY MEDICINE
citation attempts were discouraged in unwitnessed cardiac arrests if the initial rhythm was asystole or electromechanical dissociation. In this study, age, female sex, time elapsed before arrival a first-responder unit, and scene of collapse were statistically significant variables on univariate analysis. On logistic regression, near-drowning remained an independent factor of survival but the confidence intervals were wide. The proportion of unwitnessed arrests of noncardiac origin was markedly higher than that in the general cardiac arrest population. 6 This is explained partly by the fact that suicide attempts (eg, intoxication [drug overdose or smoke inhalation] and hanging) are a substantial proportion of the unwimessed-arrest population. Asystole was the presenting rhythm in 73% of the patients in our study; only 13% had VE In one previous study the proportion of patients in whom VF was the initial rhythm was markedly higher. 2 This high percentage (33%) may be partly explained by the inclusion and definition criteria. Response intervals specific for different EMS systems are not believed to play a major role in the documented rhythm distribution of unwitnessed cardiac arrests. In our EMS system we have recorded VF as the initial rhythm in 65% of witnessed cardiac 6 (the overall incidence of VF is high despite relatively long mean response times--7.0 and 10.3 minutes for the first-responder and ALS units, respectively). Asystole recorded by first responders, especially in unwitnessed arrests of cardiac origin, is merely an indicator of a long interval between collapse and rhythm registration and, therefore, death. Table 2. Cat~ses of arrest in 205 unwitnessed out-of-hospital cardiac arrests. Cause of Arrest
No. (%)
Cardiac Noncardiac
107 (52.2) 98 (47,8)
Trauma Intoxication Near-drowning Hanging Nontraamatic bleeding* SIDS Carbon monoxide intoxication Pneumonia Choking Malignancy Pulmonaryembolism Other
21 (10,2) 16 (7.8) 10 (4.9) 10 (4.9) 7 (3.4) 5 (2.4) 5 (2,4) 5 (2.4) 4 (2.0) 4 (2.0) 3 (1.5) 8 (3.9)
SIDS, sudden infant death syndreme. *Aortic rupture or gastrointestinal bleeding.
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UNWITNESSED ARREST Kuisma & Jaara
i
from prolonged cardiac arrest is not rare. In our study three of the survivors from all age groups were school-aged children. Most out-of-hospital cardiac arrests occur at home, but survival is more likely in arrests that occur outside the home. ~r Outside the home, arrests are more often witnessed, or at least detected more quickly, and the time elapsed before the start of CPR is shorter. In unwitnessed cardiac arrests occurring in public places in an urban environment, it might be speculated that survival potential is greater than that for the unwitnessed-arrest population as a whole because of earlier detection. This hypothesis was supported by our results; seven of the eight survivors had collapsed outside the home. The purpose of criteria-based dispatch is to dispatch an appropriate level of care on the basis of what has happened and the patient's status. The allocation of scarce ALS resources plays an important role. The authors of two recent studies showed the power of criteria-based dispatch in reducing futile ALS calls safely and in increasing the availability of units to incidents requiring ALS. 1s,~9 However, in cardiac arrests ALS is usually dispatched, and criteria-based dispatch has not been reported to have been used to limit response in cases of cardiac arrests. Our dispatching protocol has been in use in the Helsinki EMS system since the 1980s. In clearly unwitnessed adult cardiac arrests, m which CPR is not being performed, only BLS is dispatched. Without this priority dispatching, cardiac arrest calls for ALS units would be doubled and, consequently, their availability for other calls requiring ALS would be diminished. Only 2.4% of cases (n=18), classified as clearly unwitnessed with following BLS response, did not have secondary signs of
Survival was most likely (13%) when PEA was the first rhythm recorded. In a large series from Gothenburg, Sweden, 2% of patients survived to discharge. 1t In another recent study, survival was 6.9% for patients with an initial rhythm of PEA. t2 It seems that the probabilities of survival according to initial rhythm in witnessed cases do not directly apply to unwitnessed arrests. Response time intervals in this study were longer than those in most urban US EMS systems; this could negatively affect survival rates. On the other hand, survival of bystanderwitnessed VF of cardiac origin in the same EMS system was 32.5% in 1994, 6 a rate not much different from that reported from Seattle33 One major reason for long response times is the recording system used. In almost every previous study timing has ended when the unit has arrived at the scene, whereas in this study the end point was arrival at the patient's side. The interval between scene arrival and arrival at the patient's side can be relatively lengthy for various reasons (muhistory buildings, locked doors, no guidance). Patients who sustain unwitnessed cardiac arrests are not as likely to receive bystander-initiated CPR as patients who sustain witnessed arrests. 2 In our study, bystander CPR was not a prognostic factor, although bystander CPR was found in one report to independently influence survival in unwitnessed cardiac arrest. > It seems bystander CPR is most effective in witnessed arrests of cardiac origin in maintaining the heart in VF until defibrillation and other definitive treatments can be performed. >5 In pediatric cardiac arrest, unwitnessed collapse is not a negative prognostic factor, and almost half the survivors have sustained unwitnessed arrests. ~6 The brains of children are not as sensitive to hypoxia as adult brains, and recovery Table 3.
Previous studies with data o/unwitnessed out-@hospital cardiac arrest.
Study Stueven eta[, 19899 Spaite et al, 1 9 9 0 2 Becket et al, 19913 Lembardi et al, 19947 Grubb et al, 19958
Inclusion Criteria All adult cardiac arrests but those caused by trauma and poisoning Nontraumatic adult cardiac arrests Adult cardiac arrests of cardiac origin Adult cardiac arrests of cardiac origin Patients hospitalized alive
Sample Size
% of All Cardiac Arrests
No. Admitted to Hospital (%)
No. Discharged
Proportionof All
(%)
2,311
54.8
NA
Survivors (%)
230 {10.0)
230/533 (43.2)
103
34.6
1 (1.0)
0
(]/25 (0)
1,445
44.9
NA
4 (.3)
4/55 (7.2)
788
33.8
NA
3 (.4)
3/52 (5.8)
21
10.6"
21 (NA)
7 (NA)
7/83 (8.4)
NA, not available. *Proportioncalculatedfrom the patientsadmittedto the hospital. Calculationshavebeenmadeon the basisof figures givenin these publications.
74
ANNALS OF EMERGENCY MEDICINE 30:1 .JULY 1997
UNWITNESSED ARREST K:uisma & Jaara
I
death on arrival of a first responding unit, and the first responding unit had to ask for ALS. Subgroup analysis revealed that only one patient might have benefitted from an earlier ALS response. That analysis was based on the Helsinki Cardiac Arrest Register; each patient's initial rhythm, any delays, and the cause of cardiac arrest were retrospectively compared with the register data from survivors in this EMS system. However, the protocol was not studied in a controlled fashion and therefore recommendations concerning dispatching cannot be given on the basis of this study's findings. A controlled study is needed to investigate whether ALS resources can be allocated cost-effectively and safely in cardiac arrests. In our study, resuscitation was not initiated, on the decision of the physician on duty, in 21% of unwitnessed cases. None of these patients had a prewritten DNR order, and the DNR decision was based on survival potential (eg, disease history and delays before the arrival of EMS personnel). In our opinion the medical directors of EMS systems should consider giving DNR instructions for patients in categories that, under current knowledge, have no chance of survival. One such group, as shown by our findings, is unwitnessed adult cardiac arrest patients with arrest of obvious cardiac origin who present with asystole as the initial rhythm and who have prolonged response times. Our survey shows that survival after unwitnessed out-ofhospital cardiac arrest is unlikely with BLS-only initial response unless the cause of arrest is near-drowning or the patient is a child. Withdrawal of resuscitation should be considered if an adult victim of unwitnessed cardiac arrest is found in asystole and the arrest is obviously of cardiac origin. We found the Utstein style of data reporting applicable for the collection of data from unwitnessed out-ofhospital cardiac arrests. Originally unwitnessed, as well as noncardiac, arrests are classified as exit categories in the Utstein recommendations. 4 We chose to present the unwitnessed-arrest subgroup also in the template model to produce comparable data of this subset, in which approximately one third of out-of-hospital CPR resources are invested.
5. American Heart Association: Guidelines far cardiopu/monaryresuscitation and emergencycardiac care: Recommendationsof the 1992 national conference. JAMA 1992;268:2251-2275. 6. Kuisma M, M9~tt~ T: Out-of-hospital cardiac arrests in Helsinki: Utstain style reporting. Heart 1996;76:18-23. 7. Lambardi G, Gallagher J, Gennis P: Outcome of out-of-hospitat cardiac arrest in New York City: The pre-hespital arrest survival evaluation {PHASE)study. JAMA 1994;271:678-683. 8. Grubb NR, Elten RA, Fox KAA: In-hospital mortality after out-of-hospital cardiac arrest. Lancet 1995;346:417-421. 9. Stueven HA, Waite EM, Traiane P, et al: Prehospital cardiac arrest; A critical analysis of factors affecting survival. Resuscitation1989;17:251-259. 10. Ghusn HF, Teasdale TA, Pope PE, et ab Older nursing home residents have cardiac arrest survival rate similar to that of older persons living in the community. J Am GeriatrSac 1995;43:520527. 11. Herlitz J, Ekstr6m L, Wennerblom B, et ab Survival among patients with out-of-hospital cardiac arrest found in electromechanical dissociation. Resuscitation1995;29:97-106. 12. Pepa PE, Levine RL, Fromm RE, at al: Cardiac arrest presenting with rhythms other than ventricular fibrillation: Contribution of resuscitative efforts toward total survivership. Crit CareMefl 1993;21:1838-1843. 13. EisenbergMS, Cummins RO, Larsee MP: Numerators, denominators, and survival rates: Reporting survival from out-of-hospital cardiac arrest. Am J ErnergMed 1991;9:544-546. 14. Martens PR, Mullie A, Calle P, et al: Influence on outcome after cardiac arrest of time elapsed between call for help and start of bystander basic CPR.Resuscitation1993;25:227-234. 15. Swor RA, Jackson RE, Cynar M. et al: Bystander CPR,ventricular fibrillation, and survival in witnessed, unmonitored out-of-hospital cardiac arrest. Ann EmergMed 1995;25:780-784. 16. Kuisma M, Suominen P, Korpela R: Paediatric cut-of-hospital cardiac arrests: Epidemioiagy and outcome. Resuscitation1995;30:141-150. 17, Litwin PE, EisenbergMS, Hallstrom AP, et ab The location of collapse and its effect on survival from cardiac arrest. Ann EmergMed 1987;16:787-791. 18, CurkaPA, PepePE, Ginger VF, et ah Emergencymedical services priority dispatch. Ann Emerg Med 1993;22:1688-1695. 19. Culley LL, Henwood OK, Clark JJ, et al: Increasing the efficiency of emergencymedical services by using criteria based dispatch. Ann EmergMef11994;24:867-872. We thank Per Rosenberg, MD, PhD, for valuable comments; Anneli Ojaj~Jrvi, MSc, for statistical review; and the Laerdal Foundation and Finnish Society of Intensive Care for financial support.
Reprint no. 47/1/81675 Address for reprints: Markku Kuisma, MD, MQ Helsinki City EMS Agricolankatu 15 A FINO0530 Helsinki Finland
REFERENCES 1. EisenbergMS, Hadas E, Nuri I, et al: Sudden cardiac arrest in Israeb Factors associated with successful resuscitation. Am J EmergMed 1988;4:319-323. 2. Spaite DW, Haolon T, Criss EA, et ab Prehospital cardiac arrest: The impact of witnessed collapse and bystander CPR in a metropolitan EMS system with short response times. Ann Emerg Meal1990,19:1264-1269. 3. Becker LB, Ostrander MP, BaiTott J, et al: Outcome of CPR in a large metropolitan area: Where are the survivors?Ann EmergMed 1991;29:355-361. 4. Cummins RO, Chamberlain DA, Abramsen NS, et al: Recommendedguidelines for uniform reporting of data from out-of-hospital cardiac arrest: The Utstein style. Ann EmergMed 1991;20:861-874.
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