Don't forget the defibrillator in the dialysis unit

Charles A. Herzog

Cardiovascular Special Studies Center, United States Renal Data System and University of Minnesota, Minneapolis, MN, USA

Correspondence and offprint requests to: C. A. Herzog, MD, 914 South 8th Street, Suite D-206, Minneapolis, MN 55404, USA. Email: cherzog{at}usrds.org

Keywords: dialysis; kidney; death

Dialysis patients are a group at extraordinarily high risk for mortality. The death rate for prevalent US dialysis patients in 1999–2001 was 235 deaths/1000 patient-years [1]. Cardiac disease is the major cause of death, accounting for 43% of all-cause mortality [1]. Dialysis patients have poor long-term survival after acute myocardial infarction, with a 2 year mortality of 74%, which is essentially unchanged over the past two decades [2,3]. Approximately 20% of cardiac deaths in US dialysis patients are attributed to acute myocardial infarction [1]. The single largest cause of death in dialysis patients, however, is potentially ascribable to arrhythmic mechanisms as 61% of cardiac deaths in the United States Renal Data System (USRDS) database are due to ‘cardiac arrest, cause unknown’ or arrhythmia.

Cardiac arrest in dialysis patients is an event characterized by high short-term mortality. Karnik et al. [4] reported that the 48 h mortality of 400 dialysis patients with cardiac arrest was 60%. Cardiopulmonary resuscitation (without access to rapid defibrillation) in dialysis patients has been associated with very poor survival: 92% in-hospital death and 97% 6 month mortality in 74 patients reported by Moss et al. [5] and 100% in-hospital mortality for 24 patients in a paper by Lai et al. [6]. In a USRDS cohort study of dialysis patients hospitalized after cardiac arrest in 1996–2001, the 30 day mortality was 68% and the 1 year mortality was 85% [3]. As these cohort data apply to patients who were admitted alive to hospital, they imply that the overall survival in cardiac arrest is even worse, as many patients likely could not be successfully resuscitated out of hospital.

There are a multiplicity of factors implicated in the peculiar vulnerability of dialysis patients to sudden cardiac death. Ischaemic heart disease, including acute myocardial infarction, certainly plays a major role in the aetiology of cardiac arrest. Other aetiological factors rendering ESRD patients susceptible to arrhythmic death include left ventricular hypertrophy, electrolyte shifts in haemodialysis patients (particularly during haemodialysis), and abnormalities in myocardial ultrastructure and function, including endothelial dysfunction, interstitial fibrosis, and decreased coronary perfusion reserve [7–10].

At the Cardiovascular Special Studies Center of USRDS, we have analysed the outcome of a cohort of incident dialysis patients (1995–1999) surviving at least 1 year after dialysis initiation [3]. There were 130 379 patients with diabetes as the primary cause of ESRD. In these patients the cardiac arrest rate was 110 events/1000 patient years in the first follow-up year (corresponding to 2 years after dialysis initiation), and it rose progressively to 208 events/1000 patient years at year 4 (i.e. 5 years after dialysis initiation). In diabetic ESRD patients surviving 5 years, the cumulative risk of cardiac arrest is at least 50%. The risk of cardiac arrest increases in a non-proportional manner related to dialysis vintage: these data imply that at some basic level, ESRD is indeed ‘bad’ for the heart.

The non-physiological delivery of conventional thrice-weekly haemodialysis schedules may magnify the risk of cardiac arrest. Bleyer et al. [11] reported a 50% increased frequency of sudden and cardiac death on Monday (for patients dialysing Monday, Wednesday and Friday) and similar findings on Tuesday (for patients receiving haemodialysis on Tuesday, Thursday and Saturday). Using data from Fresenius Medical Care North America, Karnik et al. [4] have confirmed that Monday is the most likely day for cardiac arrests in haemodialysis patients. A contributing factor to the risk of cardiac arrest is low potassium dialysate. In a case control comparison by Karnik et al. [4], patients with cardiac arrest were nearly twice as likely to have been dialysed against a 0 or 1.0 mEq/l potassium dialysate on the day of cardiac arrest.

Although most cardiac arrests do not occur during the delivery of haemodialysis, the heightened risk of sudden cardiac death in the dialysis unit and potential for successful treatment should prompt nephrologists to implement measures designed to decrease the lethality of cardiac arrest in the dialysis unit. Karnik et al. [4] have reported a cardiac arrest rate of 7 per 100,000 haemodialysis sessions. Becker et al. [12] have described the epidemiology of outpatient cardiac arrest in Seattle and King County from 1990 to 1996 (using ambulance data). There were 47 cardiac arrests in dialysis centres, with an annual incidence of 0.75. Linda Becker has generously shared with me her unpublished dialysis-specific data. There were 41 witnessed events, and bystander cardiopulmonary resuscitation (CPR) was administered in 41 patients. In 29 patients (62%) the cardiac rhythm was ventricular fibrillation or ventricular tachycardia. The overall survival to hospital discharge was 30%; in patients with ventricular tachycardia or ventricular fibrillation it was 38%. These survival statistics provide a compelling case for the availability of defibrillators in all dialysis units, as they reflect ambulance crews, and not on-site defibrillator capability. The mortality rate is ~10% per minute in the first 5 min after cardiac arrest (even with CPR), and survival is uncommon after 10 min without successful therapy—this is the justification for mandatory on-site defibrillator capability, as ambulance response times will always be problematic.

The most cost-effective means of providing on-site defibrillator capability in dialysis centres is the use of automatic external defibrillators (AEDs). AEDs are intended to be used in non-medical settings by non-medical operators; their use in dialysis centres is ideal, as they do not require advanced medical training. AEDs are currently widely used in diverse non-medical settings in the US: casinos, health clubs, athletic facilities, and all commercial jet aircraft. It is noteworthy that the newest Dialysis Outcome Quality Initiative (DOQI) practice guidelines of the National Kidney Foundation relating to the treatment of cardiovascular disease in dialysis patients mandate the presence of defibrillators in all dialysis centres (NKF National Meeting, 30 April 2004, Chicago, IL, USA).

Most cardiac arrests in haemodialysis patients do not occur during the delivery of dialytic therapy. Implantable cardioverter defibrillators (ICDs) might provide the best protection against sudden cardiac death, as they do not require the event to occur in a witnessed setting. A prospective, randomized clinical trial testing the efficacy of ICDs for the reduction of sudden cardiac death and all-cause mortality would be logical in dialysis patients. Based on observational data and the relatively low cost, reliability and simplicity of AEDs, it is logical to mandate on-site capability for rapid defibrillation (including staff trained to use AEDs) in dialysis centres. Ultimately, AEDs may not be as effective as implantable devices, but they are a good first step for improving the survival of dialysis patients. Don't forget the defibrillator in the dialysis unit.

Conflict of interest statement. Charles A. Herzog has received research support from Medtronic and has also served as a consultant to Guidant and Minntech (Contel Medical).



   References
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  1. US Renal Data System. USRDS 2003 Annual Data Report. National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, USA, 2003
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  3. US Renal Data System. USRDS 2002 Annual Data Report. National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD, 2002
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