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1 This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier s archiving and manuscript policies are encouraged to visit:

Resuscitation (2008) 79, 387 390 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/resuscitation COMMENTARY Termination : A guide to interpreting the literature Laurie J.

Richard Verbeek b,f a Prehospital and Transport Medicine Research Program, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada b Division of Emergency Medicine, Department of Medicine,

2 Resuscitation (2008) 79, available at journal homepage: COMMENTARY Termination : A guide to interpreting the literature Laurie J. Morrison a,b,c,, Blair L. Bigham a,d, Alex Kiss e, P. Richard Verbeek b,f a Prehospital and Transport Medicine Research Program, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada b Division of Emergency Medicine, Department of Medicine, University of Toronto, Toronto, Ontario, Canada c Department of Health Policy, Management and Evaluation, University of Toronto, Toronto, Ontario, Canada d Institute of Medical Science, School of Graduate Studies, University of Toronto, Toronto, Ontario, Canada e Department of Research Design and Biostatistics, Institute for Clinical and Evaluative Sciences, Toronto, Ontario, Canada f Sunnybrook Osler Centre for Prehospital Care, Sunnybrook Health Sciences Centre, Canada Received 6 February 2008; received in revised form 11 July 2008; accepted 17 July 2008 KEYWORDS Emergency medical services; Cardiopulmonary resuscitation; Resuscitation orders; Medical ethics; Paramedic Summary Introduction: Prehospital termination rules are used to decide on one of two actions: to continue resuscitation and to hospital or to terminate resuscitation. The literature is confusing as some rules are derived with survival as the outcome of interest (predicting when to and reporting sensitivity and negative predictive value) and other rules use death (predicting when to terminate resuscitation and reporting specificity and positive predictive value). Very few publish the EMS rate when the rule is applied; the outcome of interest to EMS services. Methods: We propose to review the test characteristics and rates of the decision rules published between 1966 and Results: We identified 9 analyses of 6 termination rules; 1 inhospital, and 5 prehospital (2 advance and 3 basic life providers). The inhospital and the basic life rules were derived using survival whereas the rules were derived using death. The rate was published in two studies. When all the rules were reanalysed for death the specificity varied from 90.2% to 100%, the positive predictive value from 99.5% to 100% and the rate varied from 37% to 91%. Conclusion: We suggest that the diagnostic test characteristics of termination rules should be reported with death as the primary outcome which identifies for the paramedics futile resuscitations that should be terminated in the field. We also emphasize the need to report rates to provide the EMS services with an implementation benchmark Elsevier Ireland Ltd. All rights reserved. A Spanish translated version of the summary of this article appears as Appendix in the final online version at doi: /j.resuscitation Corresponding author at: Prehospital and Transport Medicine Research Program, C753, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, Ontario, Canada M4N 3M5. Tel.: ; fax: address: laurie.morrison@sunnybrook.ca (L.J. Morrison) /$ see front matter 2008 Elsevier Ireland Ltd. All rights reserved. doi: /j.resuscitation

3 388 L.J. Morrison et al. Table 1 Survival considered as the positive outcome TOR decision rule Survived Died Transport a b a+ b Terminate c d c+ d a + c b+ d a+ b + c + d Invited commentary Termination (TOR) for out-of-hospital nontraumatic cardiac arrest by prehospital care providers reduces burdens on the health care system, improves public safety by reducing lights-and-sirens s, and eases hardships of grieving families. Numerous clinical prediction rules have been derived and validated to determine which patients will not benefit from resuscitation efforts beyond those available in the field. These rules aim to reduce the number of futile cases ed to hospital while ensuring no potential survivor is pronounced dead at the scene. TOR clinical decision rules are used to decide on one of two actions; either to terminate resuscitation at the scene or to continue resuscitation while ing the patient to a receiving hospital. The outcome of the decision is similarly reported in one of two ways; either the patient died or survived to discharge. It is important to note that in order to validate TOR rules, all patients to whom the rule is applied must be ed regardless of the decision the rule indicates. This allows for the identification of patients who would have survived despite a TOR rule indicating a decision to terminate resuscitation. As with many other clinical decision rules, TOR rules can be considered a diagnostic test and can be reported using a typical 2 2 diagnostic test results table. In the literature, the operating characteristics of TOR clinical decision rules have been reported in two ways. This is confusing for readers to understand, for scientists to conduct comparisons, and for EMS services who wish to implement the rules. The first way of reporting this has been to consider survival as the positive outcome (Table 1). From the conventional perspective of a diagnostic test, this approach attempts to predict survival. This approach recommends for patients who may benefit from continued resuscitation. As a perfect test from a prehospital point of view, no patients would fall into box c and the sensitivity as well as the negative predictive value of the rule would be 100%. This perspective describes a clinical predication rule to continue to resuscitate rather than to terminate resuscitation. Table 2 Death considered as a positive outcome TOR decision rule Died Survived Terminate a b a+ b Transport c d c+ d a + c b+ d a+ b + c + d Table 3 Termination publications: the rules Publication Cohort ROSC Initial rhythm Witnessed status Bystander CPR Additional Unwitnessed NA Non-shockable initial rhythm No ROSC after 10 min van Walraven et al. 7 Inhospital Not EMS witnessed NA No shock prior to Verbeek et al. 4 and Morrison et al. 3 life a Prehospital basic NO ROSC prior to NA NA PEA or Asystole after 20 min of No ROSC after 20 min Cone et al. 5 Prehospital resuscitation No shock prior to Unwitnessed No bystander CPR NO ROSC prior to Morrison et al. 2 Prehospital NA NA Non-shockable rhythm after 1 min Non-shockable initial rhythm NO ROSC after 1 min NA Asystole NA Call response interval >8 min Ong et al. 6 Prehospital basic life Ong et al. 6 Prehospital basic life a Same termination rule. Verbeek et al. 4 (derivation study) and Morrison et al. 3 (prospective validation study).

4 Termination : A guide to interpreting the literature 389 Table 4 Analytical approach in termination publications Publication Predicts PPV Specificity NPV Sensitivity van Walraven Survival NR 100 et al. 7 Verbeek et al. 4 Survival Cone et al. 5 Death Morrison et Death al. 3 Morrison et Survival al. 2 Ong et al. 6 Survival Various The second way of reporting has been to consider death as the positive outcome (Table 2). This approach attempts to predict death. It recommends termination for patients who have no hope of survival despite continued resuscitation. As a perfect test from a prehospital point of view no patients would fall into box b and the specificity as well as the positive predictive value of the rule would be 100%. This perspective describes a rule that aids in the decision to terminate resuscitation rather than to continue resuscitation. We suggest that the second way of reporting is more in keeping with the recommendations in the American Heart Association Emergency Cardiac Care guidelines which state it is unethical for an EMS system to not permit EMS responders to stop resuscitative efforts. 1 A termination rule should be reported from this perspective and facilitate this decision making process. We have published three papers examining TOR rules, 2 4 two of which reported from the perspective of continuing to resuscitate and one from the more appropriate perspective of termination. We appreciate that it is difficult to compare TOR prediction rules when clinical decision rules are not uniformly presented. A review of the literature has identified nine analyses of TOR clinical decision rules in six publications. 2 7 For completeness of this review, Table 3 outlines the six different rules. Table 4 represents the perspective from which the TOR rule was described in each original publication while Table 5 presents the nine analyses reworked to solve for death as the positive outcome of interest for interpretation of the diagnostic tests. Also we calculated the resulting rate as the operational outcome of interest to EMS operators, included in some but not all of the literature. We propose standard reporting of clinical prediction rules for Termination of Resuscitation. We suggest that the ideal TOR clinical decision rule would recommend the termination efforts for patients who will not survive the cardiac arrest; reporting specificity and negative predictive value. In addition, we recommend that each rule should report the rate; the outcome of interest for EMS operators. This published outcome permits those who implement the rule to evaluate their service performance. Table 5 Clinical decision tools: predicting death in out-of-hospital cardiac arrest Original articles Other validations Verbeek (Ong) 6 Petrie (Ong) 6 Marsden (Ong) 6 Morrison BLS 2 (N = 4673) Morrison ALS 2 (N = 4673) Verbeek 4 (N = 662) Cone 5 (N = 501) Morrison BLS 3 (N = 1240) van Walraven 7 (N = 1077) Predicts death Died Survived Died Survived Died Survived Died Survived Died Survived Died Survived Died Survived Died Survived Died Survived Terminate , Transport , , Specificity PPV Sensitivity NPV Transport rate NA (%) NA: not applicable as this study was based on inhospital cardiac arrests.

5 390 L.J. Morrison et al. Conflict of interest statement None. References 1. ECC Committee Subcommittees and Task Forces of the American Heart Association. American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation 2005;112(24 Suppl.):IV1 203 [reprint in Pediatrics May;117(5):e ; PMID: ]. 2. Morrison LJ, Verbeek PR, Vermeulen MJ, et al. Derivation and evaluation of a termination clinical prediction rule for advanced life providers. Resuscitation 2007;74(2): Morrison LJ, Visentin LM, Kiss A, et al. Investigators TOR. Validation of a rule for termination in out-of-hospital cardiac arrest. New Eng J Med 2006;355(5):478 87, see comment. 4. Verbeek PR, Vermeulen MJ, Ali FH, Messenger DW, Summers J, Morrison LJ. Derivation of a termination-of-resuscitation guideline for emergency medical technicians using automated external defibrillators. Acad Emerg Med 2002;9(7):671 8 [see comment]. 5. Bailey ED, Wydro GC, Cone DC. Termination in the prehospital setting for adult patients suffering nontraumatic cardiac arrest. National Association of EMS Physicians Standards and Clinical Practice Committee. Prehospital Emerg Care 2000;4(2): Ong MEH, Jaffey J, Stiell I, Nesbitt L, Group OS. Comparison of termination-of-resuscitation guidelines for basic life : defibrillator providers in out-of-hospital cardiac arrest. Ann Emerg Med 2006;47(4): van Walraven C, Forster AJ, Stiell IG. Derivation of a clinical decision rule for the discontinuation of in-hospital cardiac arrest resuscitations. Arch Intern Med 1999;159(2): [see comment].

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