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Sudden cardiac arrest outside the hospital — value of defibrillators in ambulances
Resuscitation. 21 (1991) 283-288
283
Elsevier Scientific Publishers Ireland Ltd.
Sudden cardiac arrest outside the hospital of defibrillators in ambulances Christian Torp-Pedersen,
value
Erling Birk Madsen* and Asger Pedersen**
Department of Cardiology, Glostrup County Hospital, DK-2600 Glostrup (Denmark)
(Received January 28th, 1991; accepted February 4th, 1991)
In a region with a population of 250 000 people, all emergency calls for cardiac arrest were prospectively registered during a period of 6 years. Timing of events were carefully registered as were treatment and the participation of 3 ambulances equipped with detibrillators. When time until initial treatment of cardiac arrest was below 5 min, 12% could be resuscitated and discharged alive. This figure decreased to 2% in the period between 5 and 10 min and was zero to above 10 min. Similarly, a reasonable 12% of patients experiencing ventricular fibrillation at a public place could be resuscitated and discharged alive whereas only 5% of ventricular fibrillation occurring at the patients home could be successfully resuscitated. Asystolia was rarely treated successfully. Faster treatment improved results much and 63% of patients having ventricular fibrillation in the emergency room left hospital alive. Results of cardioversion in ambulances did not depend on time from initiation of cardiac arrest, but all patients receiving cardioversion later than IO min died without regaining consciousness. The results were compared with other more effective programs. The study region apparently had much fewer cardiac arrest than a similar region in Seattle, U.S.A. In those cases where treatment could be initiated within 5 min, results ware comparable.
Resuscitation -
Ventricular fibrillation -
Cardiac arrest -
Mobile coronary care unit
INTRODUCTION
Mobile coronary care units (MCU) have been introduced in a large number of places in an effort to reduce the mortality of sudden cardiac arrest. Important elements in various programs have been introduction of defibrillators in ambulances, organisation of very short response times, and teaching resuscitation to the population. The efficacy of these programs has varied considerably. In Seattle [l-3], very intensive programs were developed involving defibrillators in ambulances manned by highly trained paramedics, education of the adult population and average response times after cardiac arrest of only 3 min. Eleven to twenty-three percent of cases of cardiac arrest could be discharged from hospital alive. In another
Address all correspondence and reprint requests io: Christian Torp-Pedersen, Department of Cardiology P, Gentofte Hospital, DK-2900 Hellerup, Denmark. *Current address: Medicinsk afd. B, Rigshospitalet, DK-2100 Kdbenhavn 0, Denmark. **Current address: Mundtsvej 9, DK-3520 Farum, Denmark.
03OO-9572/91/303.50 0 1991 Elsevier Scientific Publishers Ireland Ltd. Printed and Published in Ireland
284
organisation in Ohio and Michigan [4] a program with an average response time of 4.4 min was developed and 8% of cases could be discharged alive. A number of less extensive programs have demonstrated less promising results [6-91. Although it is generally accepted that quick basic as well as advanced treatment is necessary for a succesful outcome after cardiac arrest, the importance of each aspect of the organisation is not yet clear. In Glostrup we have for a number of years conducted a program with deflbrillators in ambulances as the most important aspect. We have analysed the results in detail and compared the results with more intensive programs. PATIENTS
AND
METHODS
Glostrup county hospital receives all cardiac emergencies from a population of 250 000 people. The region is part of the city of Copenhagen. All cardiac arrests were prospectively registered in detail. Ambulance personnel registered the time from cardiac arrest until arrival of ambulance and transport time. The time from cardiac arrest until arrival of ambulance was considered unknown if a call is not immediately put through. The diagnosis of cardiac arrest as ventricular fibrillation, asystole or other type was made from the first available ECG in an ambulance or in the emergency room. In the study period from January 1977 to December 1982, 1262 cardiac arrests were registered in the emergency room of the hospital. Of these, 613 cases were primary cardiac arrest defined as cardiac arrest unprecedented by other serious conditions such as accidents, bleeding or poisoning. Of the patients with primary cardiac arrest, 243 were acute myocardial infarction demonstrated at autopsy or by elevated cardiac enzymes, 280 were other cases of ischemic heart disease, 2 cases were AVblock, and in 88 cases, no certain diagnosis could be made. There were 5 ambulances in the region manned with 3 people and with detibrillators installed in the ambulance. The ECG was transmitted by radio to the coronary care unit of the hospital where it was interpreted by trained nurses. Ambulance personnel if necessary delivered DC shock. All ambulances had pure oxygen installed and the personnel was well trained in performance of close-chest cardiac massage and manual ventilation. We have used the following nomenclature for the result of treatment in ambulances and emergency room. Died. Patients who died before leaving the emergency room. Resusc. died unconscious. Patients who were resuscitated and who later died without having contact with surroundings. Resusc. cer. dam. Patients who were resuscitated and later discharged from hospital with cerebral damage. This damage was always of such severity that patients could not resume normal activities. Resusc. awake died. Patients who were resuscitated and later died before discharge. Some level of undetected brain damage may have been present in these cases. Resusc. disch. OK. Patients who were resuscitated and discharged without apparent brain damage. These patients could all resume normal activities. Statistical analysis of contingency tables was performed with the Chi2 test.
285
Table 1. In 61 I of 613 cases, the place of cardiac arrest and the fate of the patient were known. In two cases, the place of arrest was unknown. One patient was discharged without cerebral damage, the other died unconscious. The place of cardiac arrest are the patients home, public place - streets, shops, offices etc., ambulances and emergency room. See Materials and Methods for abbreviations. Place of arrest
Type
N
Died (W
Resusc. died unconscious
Resusc. cer. Resusc. (“XJ)dam. (%) awake died
Home Home Public place Public place Ambulance Ambulance Emergency room Emergency room
AS VF AS VF AS VF AS VF
284 II9 83 45 29 22 22 I9
95 76 92 69 55 41 41 11
4 I6 6 I6 21 36 36 I6
0.3 3 0 0 0 0 0 0
0 0
0
2 7 IO 5 II
Resusc. (‘%I)disch. OK 0 5
2 I3 I7 30 I8 63
RESULTS
In the period from 1977 to 1982, a total of 38 patients were resuscitated and discharged alive. Of these cardiac arrests, 22 took place outside of the hospital, the remaining in the emergency room. In Table I, we have shown the fate of the patients dependent on place of cardiac arrest. The chances of success are much higher in case of ventricular fibrillation (P < 0.001) and chances also highly dependent on the place of cardiac arrest (P < 0.001). Of the 57 1 cases with sudden cardiac arrest taking place outside hospital, 258 were transported in ambulances equipped with delibrillators and 313 in ambulances without defibrillators. The fate of the patient dependent on the type of ambulance and the time from cardiac arrest until start of treatment is shown in Table II. Apparently the results are similar. This reflects in part that only a minority of ambulances reached the patient within 5 min of cardiac arrest. Also the two groups of patients are not directly comparable. In cases of obvious cardiac emergency, an ambulance equipped with a defibrillator was preferably sent.
Table II. Transport in ambulances with and without defibrillators. See Materials and Methods for abbreviations. Results Died (%) Resusc. died unconscious (‘%I) Resusc. cer. dam. (‘K) Resusc. awake, died (‘!!) Disch. OK (xp) Total (0%)
+ n = 270 84 4 I 0.4 0.4 100
- n = 217 86 4 I I 0 100
286 Table III. Influence of time until initiation of treatment. For 571 cardiac arrests taking place outside hospital, the results are shown to be dependent on the time until treatment was initiated. Bystanders did not initiate treatment. The table includes patients treated in ambulances without as well as with detibrillators installed. See Materials and Methods for abbreviations. Results
Time until initiation of treatment of cardiac arrest O-S min 150 ptt.
Died (%) Resusc. died unconscious (“XI) Resusc. cer. dam. (%) Resusc. awake, died (%) Disch. OK (%) Total
5-10 min 191 ptt.
> 10 min 61 ptt.
Unknown 169 ptt.
70 15 1 1 12
90 7 1 0 2
92 7 2 1 0
92 7 0 0 0
100
100
100
100
Table III shows, for all 571 cases of sudden cardiac arrest taking place outside the hospital, the fate of the patients as dependent on the time from start of cardiac arrest until initial treatment by ambulance drivers with closed-chest cardiac massage and manual ventilation. Bystanders did not in any case initiate this treatment. As expected, time until treatment is a very important predictor of favorable outcome. DC shock was delivered in the ambulances in 85 cases. The results of these are shown in Table IV. A minority of patients received DC shock in cases that were later interpreted as asystole. The DC shock was considered successful if it resulted in a palpable pulse. There was sinus rhythm all cases but one which was a 3rd degree atrio ventricular block and an escape rhythm. A total of 12 patients were treated successfully in the ambulance and, of these, 7 could be discharged without cerebral damage (all treated within 10 min of cardiac arrest); 5 died without regaining consciousness (treated in the interval 5-15 min).
Table IV. Results of 85 attempts of cardioversion in ambulances. During 6 years, DC was attempted in 85 cases out of 336 patients treated in ambulances equipped with a defibrillator. The table shows the ECG diagnosis as ventricular fibrillation (VF) or asystolia (AS). DC was considered succesful if it resulted in a palpable pulse. There was no statistical dependency of success with time (P = 0.96). Diagnosis/results
Time until initiation of treatment &5 min 24 ptt.
AsystoliaIno effect (%) VFDC unsuccessful (%) VF/DC results in AS (%) VFLDC successful (%) Total (%)
5-10 min 43 ptt.
> 10 min 13 ptt.
Unknown 5 ptt.
13 38 33 17
16 0 26 14
23 46 15 15
20 60 20 0
100
100
100
100
281 DISCUSSION
Compared to very intensive programs, the results presented here are not impressive. In one Seattle program [4], 34% of cardiac arrest could be primarily resuscitated and 17% could be discharged alive. In those cases where response times in our region were below 5 min (Table III), the results were comparable and 12% could be discharged without cerebral damage. Due to low average response times we were also able to achieve success rates comparable to Seattle (Table I) when cardiac arrest took place in public places or in ambulances. From these results we conclude that the different success rates between the two programs is caused by different response times. A program must be able to achieve response times below 5 min if a high success rate is to be obtained. We have previously demonstrated [lo] that basic resuscitation consisting of external cardiac massage and manual ventilation is of limited value and that advanced treatment of cardiac arrest must be initiated within 10 min of cardiac arrest if there is to be any chance of resuscitation without cerebral damage. Installation of detibrillators in ambulances is therefore a necessary component of any effective program. In the present program, ambulances with delibrillators reached the patients relatively late and, over 6 years, only 7 patients receiving DC shock in ambulances could be discharged from hospital without apparent brain damage. Primary resuscitation was not very dependent on time and many patients had treatable ventricular fibrillation more than 15 minutes after cardiac arrest. If defibrillators were installed in all ambulances in our region a larger proportion of patients treated within 10 min could successfully be resuscitated. A reasonably optimistic figure based on our own results and those from Seattle is that 17% of patients treated within 5 min and 10% of those treated in the interval from 5-10 min can be successfully resuscitated. Installation of defibrillators in all ambulances would therefore be expected to result in 45 patients resuscitated and discharged without cerebral damage, twice the present number. This result is not impressive over a period of 6 years and emphasizes that installation of defibrillators in ambulances as the only measure is not very effective. The region studied in one Seattle program (31 is of similar size as our region. Over a period of 6 years, they would have registered 2792 cardiac arrests outside hospital. Of these, 949 would primarily be resuscitated and 475 would leave hospital alive. In our region, only 571 cardiac arrests were registered outside hospital, and if delibrillators were installed in all ambulances only 45 patients would be expected to leave hospital without cerebral damage. In Seattle, they do not distinguish between patients leaving hospital with or without cerebral damage, but from our results it is apparent that only few patients are discharged with severe cerebral damage. If all cardiac arrests in our region could receive advanced treatment within 5 min, 17”/ or 97 patients would be expected to leave hospital alive. Thus, a program similar to Seattle would in our region have a much more limited effect. The reason for this vast difference is not readily apparent. Social differences or differences in the frequency of ischemic heart disease may contribute. An important consequence of this observation is that the effect of a program in one region cannot be used to calculate the expected effect in other places.
288 CONCLUSION
Installation of defibrillators in ambulances have little benefit in resuscitation of cardiac arrest unless measures are also taken to ensure initiation of therapy within 5 min. The potential impact of a program for treatment of out of hospital cardiac arrest should be evaluated locally since the frequency of emergency calls due to cardiac arrest apparently varies greatly in different places. REFERENCES L.A. Cobb, R.S. Baum, H. Alvarez and W.A. Schaffer, Resuscitation from out-of hospital ventricular fibrillation: 4 years follow-up, Circulation 51-52 (Suppl. 3) 223-228 + Discussion (1975) 229-235. 2 M.S. Eisenberg, A. Hallstrom and L. Bergner, Long-term survival after out-of-hospital cardiac arrest, N. Engl. J. Med. 306 (1982) 134@--1343. 3 MS. Eisenberg, L. Bergner and A. Hallstrom, Out-of-hospital cardiac arrest: improved survival with paramedic services. Lancet April (1986) 812-815. 4 S. Goldstein, J.R. Landis, R. Leighton, G. Ritter, CM. Vasu. A. Lantis and R. Serokman. Characteristics of the resuscitated out-of-hospital cardiac arrest victim with coronary heart disease, Circulation, 64 (1981) 977-984. 5 R.G. Thompson, A.P. Hallstrom and L.A. Cobb, Bystander-initiated cardiopulmonary resuscitation in the management of ventricular fibrillation, Ann. Intern. Med., 90 (1979) 737-740. 6 P. Siltanen, S. Sundberg and I. Hytonen, Impact of a mobile coronary care unit on the sudden coronary mortality in a community, Acta Med. Stand., 205 (1979) 195-200. 7 N.J. Vetter, Pocock and D.G. Julidan, Measuring the effect of a mobile coronary care unit upon the community, Br. Heart J., 41 (1979) 418425. 8 J. Rokkedal Nielsen, L. Pind Rasmussen, E.M. Damsgaard and M. Dalsgaard, Hjertestop uden for hospita. En retrospektiv undersdgelse i Frederecia, Ugeskrift for Laeger, I44 (1982) 1998-2001. 9 A. Pedersen, Ki Saunama and E. Kjdller, Langtidsmonitorering. I. In: Nordisk symposium. Ischaemisk Hjertesygdom. Editors: L. Wilhelmsen. A. Vedin and C. Wilhelmsson, Goteborg, 1979, pp. 120-129. IO C. Tarp-Pedersen, E. Birk-Madsen and A. Pedersen, The time factor in resuscitation initiated by ambulance drivers, Eur. 1. Cardiol.,lO (1989) 555-557. 1
283
Elsevier Scientific Publishers Ireland Ltd.
Sudden cardiac arrest outside the hospital of defibrillators in ambulances Christian Torp-Pedersen,
value
Erling Birk Madsen* and Asger Pedersen**
Department of Cardiology, Glostrup County Hospital, DK-2600 Glostrup (Denmark)
(Received January 28th, 1991; accepted February 4th, 1991)
In a region with a population of 250 000 people, all emergency calls for cardiac arrest were prospectively registered during a period of 6 years. Timing of events were carefully registered as were treatment and the participation of 3 ambulances equipped with detibrillators. When time until initial treatment of cardiac arrest was below 5 min, 12% could be resuscitated and discharged alive. This figure decreased to 2% in the period between 5 and 10 min and was zero to above 10 min. Similarly, a reasonable 12% of patients experiencing ventricular fibrillation at a public place could be resuscitated and discharged alive whereas only 5% of ventricular fibrillation occurring at the patients home could be successfully resuscitated. Asystolia was rarely treated successfully. Faster treatment improved results much and 63% of patients having ventricular fibrillation in the emergency room left hospital alive. Results of cardioversion in ambulances did not depend on time from initiation of cardiac arrest, but all patients receiving cardioversion later than IO min died without regaining consciousness. The results were compared with other more effective programs. The study region apparently had much fewer cardiac arrest than a similar region in Seattle, U.S.A. In those cases where treatment could be initiated within 5 min, results ware comparable.
Resuscitation -
Ventricular fibrillation -
Cardiac arrest -
Mobile coronary care unit
INTRODUCTION
Mobile coronary care units (MCU) have been introduced in a large number of places in an effort to reduce the mortality of sudden cardiac arrest. Important elements in various programs have been introduction of defibrillators in ambulances, organisation of very short response times, and teaching resuscitation to the population. The efficacy of these programs has varied considerably. In Seattle [l-3], very intensive programs were developed involving defibrillators in ambulances manned by highly trained paramedics, education of the adult population and average response times after cardiac arrest of only 3 min. Eleven to twenty-three percent of cases of cardiac arrest could be discharged from hospital alive. In another
Address all correspondence and reprint requests io: Christian Torp-Pedersen, Department of Cardiology P, Gentofte Hospital, DK-2900 Hellerup, Denmark. *Current address: Medicinsk afd. B, Rigshospitalet, DK-2100 Kdbenhavn 0, Denmark. **Current address: Mundtsvej 9, DK-3520 Farum, Denmark.
03OO-9572/91/303.50 0 1991 Elsevier Scientific Publishers Ireland Ltd. Printed and Published in Ireland
284
organisation in Ohio and Michigan [4] a program with an average response time of 4.4 min was developed and 8% of cases could be discharged alive. A number of less extensive programs have demonstrated less promising results [6-91. Although it is generally accepted that quick basic as well as advanced treatment is necessary for a succesful outcome after cardiac arrest, the importance of each aspect of the organisation is not yet clear. In Glostrup we have for a number of years conducted a program with deflbrillators in ambulances as the most important aspect. We have analysed the results in detail and compared the results with more intensive programs. PATIENTS
AND
METHODS
Glostrup county hospital receives all cardiac emergencies from a population of 250 000 people. The region is part of the city of Copenhagen. All cardiac arrests were prospectively registered in detail. Ambulance personnel registered the time from cardiac arrest until arrival of ambulance and transport time. The time from cardiac arrest until arrival of ambulance was considered unknown if a call is not immediately put through. The diagnosis of cardiac arrest as ventricular fibrillation, asystole or other type was made from the first available ECG in an ambulance or in the emergency room. In the study period from January 1977 to December 1982, 1262 cardiac arrests were registered in the emergency room of the hospital. Of these, 613 cases were primary cardiac arrest defined as cardiac arrest unprecedented by other serious conditions such as accidents, bleeding or poisoning. Of the patients with primary cardiac arrest, 243 were acute myocardial infarction demonstrated at autopsy or by elevated cardiac enzymes, 280 were other cases of ischemic heart disease, 2 cases were AVblock, and in 88 cases, no certain diagnosis could be made. There were 5 ambulances in the region manned with 3 people and with detibrillators installed in the ambulance. The ECG was transmitted by radio to the coronary care unit of the hospital where it was interpreted by trained nurses. Ambulance personnel if necessary delivered DC shock. All ambulances had pure oxygen installed and the personnel was well trained in performance of close-chest cardiac massage and manual ventilation. We have used the following nomenclature for the result of treatment in ambulances and emergency room. Died. Patients who died before leaving the emergency room. Resusc. died unconscious. Patients who were resuscitated and who later died without having contact with surroundings. Resusc. cer. dam. Patients who were resuscitated and later discharged from hospital with cerebral damage. This damage was always of such severity that patients could not resume normal activities. Resusc. awake died. Patients who were resuscitated and later died before discharge. Some level of undetected brain damage may have been present in these cases. Resusc. disch. OK. Patients who were resuscitated and discharged without apparent brain damage. These patients could all resume normal activities. Statistical analysis of contingency tables was performed with the Chi2 test.
285
Table 1. In 61 I of 613 cases, the place of cardiac arrest and the fate of the patient were known. In two cases, the place of arrest was unknown. One patient was discharged without cerebral damage, the other died unconscious. The place of cardiac arrest are the patients home, public place - streets, shops, offices etc., ambulances and emergency room. See Materials and Methods for abbreviations. Place of arrest
Type
N
Died (W
Resusc. died unconscious
Resusc. cer. Resusc. (“XJ)dam. (%) awake died
Home Home Public place Public place Ambulance Ambulance Emergency room Emergency room
AS VF AS VF AS VF AS VF
284 II9 83 45 29 22 22 I9
95 76 92 69 55 41 41 11
4 I6 6 I6 21 36 36 I6
0.3 3 0 0 0 0 0 0
0 0
0
2 7 IO 5 II
Resusc. (‘%I)disch. OK 0 5
2 I3 I7 30 I8 63
RESULTS
In the period from 1977 to 1982, a total of 38 patients were resuscitated and discharged alive. Of these cardiac arrests, 22 took place outside of the hospital, the remaining in the emergency room. In Table I, we have shown the fate of the patients dependent on place of cardiac arrest. The chances of success are much higher in case of ventricular fibrillation (P < 0.001) and chances also highly dependent on the place of cardiac arrest (P < 0.001). Of the 57 1 cases with sudden cardiac arrest taking place outside hospital, 258 were transported in ambulances equipped with delibrillators and 313 in ambulances without defibrillators. The fate of the patient dependent on the type of ambulance and the time from cardiac arrest until start of treatment is shown in Table II. Apparently the results are similar. This reflects in part that only a minority of ambulances reached the patient within 5 min of cardiac arrest. Also the two groups of patients are not directly comparable. In cases of obvious cardiac emergency, an ambulance equipped with a defibrillator was preferably sent.
Table II. Transport in ambulances with and without defibrillators. See Materials and Methods for abbreviations. Results Died (%) Resusc. died unconscious (‘%I) Resusc. cer. dam. (‘K) Resusc. awake, died (‘!!) Disch. OK (xp) Total (0%)
+ n = 270 84 4 I 0.4 0.4 100
- n = 217 86 4 I I 0 100
286 Table III. Influence of time until initiation of treatment. For 571 cardiac arrests taking place outside hospital, the results are shown to be dependent on the time until treatment was initiated. Bystanders did not initiate treatment. The table includes patients treated in ambulances without as well as with detibrillators installed. See Materials and Methods for abbreviations. Results
Time until initiation of treatment of cardiac arrest O-S min 150 ptt.
Died (%) Resusc. died unconscious (“XI) Resusc. cer. dam. (%) Resusc. awake, died (%) Disch. OK (%) Total
5-10 min 191 ptt.
> 10 min 61 ptt.
Unknown 169 ptt.
70 15 1 1 12
90 7 1 0 2
92 7 2 1 0
92 7 0 0 0
100
100
100
100
Table III shows, for all 571 cases of sudden cardiac arrest taking place outside the hospital, the fate of the patients as dependent on the time from start of cardiac arrest until initial treatment by ambulance drivers with closed-chest cardiac massage and manual ventilation. Bystanders did not in any case initiate this treatment. As expected, time until treatment is a very important predictor of favorable outcome. DC shock was delivered in the ambulances in 85 cases. The results of these are shown in Table IV. A minority of patients received DC shock in cases that were later interpreted as asystole. The DC shock was considered successful if it resulted in a palpable pulse. There was sinus rhythm all cases but one which was a 3rd degree atrio ventricular block and an escape rhythm. A total of 12 patients were treated successfully in the ambulance and, of these, 7 could be discharged without cerebral damage (all treated within 10 min of cardiac arrest); 5 died without regaining consciousness (treated in the interval 5-15 min).
Table IV. Results of 85 attempts of cardioversion in ambulances. During 6 years, DC was attempted in 85 cases out of 336 patients treated in ambulances equipped with a defibrillator. The table shows the ECG diagnosis as ventricular fibrillation (VF) or asystolia (AS). DC was considered succesful if it resulted in a palpable pulse. There was no statistical dependency of success with time (P = 0.96). Diagnosis/results
Time until initiation of treatment &5 min 24 ptt.
AsystoliaIno effect (%) VFDC unsuccessful (%) VF/DC results in AS (%) VFLDC successful (%) Total (%)
5-10 min 43 ptt.
> 10 min 13 ptt.
Unknown 5 ptt.
13 38 33 17
16 0 26 14
23 46 15 15
20 60 20 0
100
100
100
100
281 DISCUSSION
Compared to very intensive programs, the results presented here are not impressive. In one Seattle program [4], 34% of cardiac arrest could be primarily resuscitated and 17% could be discharged alive. In those cases where response times in our region were below 5 min (Table III), the results were comparable and 12% could be discharged without cerebral damage. Due to low average response times we were also able to achieve success rates comparable to Seattle (Table I) when cardiac arrest took place in public places or in ambulances. From these results we conclude that the different success rates between the two programs is caused by different response times. A program must be able to achieve response times below 5 min if a high success rate is to be obtained. We have previously demonstrated [lo] that basic resuscitation consisting of external cardiac massage and manual ventilation is of limited value and that advanced treatment of cardiac arrest must be initiated within 10 min of cardiac arrest if there is to be any chance of resuscitation without cerebral damage. Installation of detibrillators in ambulances is therefore a necessary component of any effective program. In the present program, ambulances with delibrillators reached the patients relatively late and, over 6 years, only 7 patients receiving DC shock in ambulances could be discharged from hospital without apparent brain damage. Primary resuscitation was not very dependent on time and many patients had treatable ventricular fibrillation more than 15 minutes after cardiac arrest. If defibrillators were installed in all ambulances in our region a larger proportion of patients treated within 10 min could successfully be resuscitated. A reasonably optimistic figure based on our own results and those from Seattle is that 17% of patients treated within 5 min and 10% of those treated in the interval from 5-10 min can be successfully resuscitated. Installation of defibrillators in all ambulances would therefore be expected to result in 45 patients resuscitated and discharged without cerebral damage, twice the present number. This result is not impressive over a period of 6 years and emphasizes that installation of defibrillators in ambulances as the only measure is not very effective. The region studied in one Seattle program (31 is of similar size as our region. Over a period of 6 years, they would have registered 2792 cardiac arrests outside hospital. Of these, 949 would primarily be resuscitated and 475 would leave hospital alive. In our region, only 571 cardiac arrests were registered outside hospital, and if delibrillators were installed in all ambulances only 45 patients would be expected to leave hospital without cerebral damage. In Seattle, they do not distinguish between patients leaving hospital with or without cerebral damage, but from our results it is apparent that only few patients are discharged with severe cerebral damage. If all cardiac arrests in our region could receive advanced treatment within 5 min, 17”/ or 97 patients would be expected to leave hospital alive. Thus, a program similar to Seattle would in our region have a much more limited effect. The reason for this vast difference is not readily apparent. Social differences or differences in the frequency of ischemic heart disease may contribute. An important consequence of this observation is that the effect of a program in one region cannot be used to calculate the expected effect in other places.
288 CONCLUSION
Installation of defibrillators in ambulances have little benefit in resuscitation of cardiac arrest unless measures are also taken to ensure initiation of therapy within 5 min. The potential impact of a program for treatment of out of hospital cardiac arrest should be evaluated locally since the frequency of emergency calls due to cardiac arrest apparently varies greatly in different places. REFERENCES L.A. Cobb, R.S. Baum, H. Alvarez and W.A. Schaffer, Resuscitation from out-of hospital ventricular fibrillation: 4 years follow-up, Circulation 51-52 (Suppl. 3) 223-228 + Discussion (1975) 229-235. 2 M.S. Eisenberg, A. Hallstrom and L. Bergner, Long-term survival after out-of-hospital cardiac arrest, N. Engl. J. Med. 306 (1982) 134@--1343. 3 MS. Eisenberg, L. Bergner and A. Hallstrom, Out-of-hospital cardiac arrest: improved survival with paramedic services. Lancet April (1986) 812-815. 4 S. Goldstein, J.R. Landis, R. Leighton, G. Ritter, CM. Vasu. A. Lantis and R. Serokman. Characteristics of the resuscitated out-of-hospital cardiac arrest victim with coronary heart disease, Circulation, 64 (1981) 977-984. 5 R.G. Thompson, A.P. Hallstrom and L.A. Cobb, Bystander-initiated cardiopulmonary resuscitation in the management of ventricular fibrillation, Ann. Intern. Med., 90 (1979) 737-740. 6 P. Siltanen, S. Sundberg and I. Hytonen, Impact of a mobile coronary care unit on the sudden coronary mortality in a community, Acta Med. Stand., 205 (1979) 195-200. 7 N.J. Vetter, Pocock and D.G. Julidan, Measuring the effect of a mobile coronary care unit upon the community, Br. Heart J., 41 (1979) 418425. 8 J. Rokkedal Nielsen, L. Pind Rasmussen, E.M. Damsgaard and M. Dalsgaard, Hjertestop uden for hospita. En retrospektiv undersdgelse i Frederecia, Ugeskrift for Laeger, I44 (1982) 1998-2001. 9 A. Pedersen, Ki Saunama and E. Kjdller, Langtidsmonitorering. I. In: Nordisk symposium. Ischaemisk Hjertesygdom. Editors: L. Wilhelmsen. A. Vedin and C. Wilhelmsson, Goteborg, 1979, pp. 120-129. IO C. Tarp-Pedersen, E. Birk-Madsen and A. Pedersen, The time factor in resuscitation initiated by ambulance drivers, Eur. 1. Cardiol.,lO (1989) 555-557. 1