Implementing Hypothermia After Cardiac Arrest
Pedro Kurtz, MD*
Columbia University Medical Center
New York, New York, USA
Stephan A. Mayer, MD, FCCM*
Neurological Institute of New York
New York, New York, USA
Induction of therapeutic mild hypothermia (32 to 34°C) improves survival and neurological outcomes after cardiac arrest (CA). In 2002, two landmark studies were published from Europe and Australia in which patients were cooled following out-of-hospital CA.1,2 After these studies, the International Liaison Committee on Resuscitation (ILCOR) included hypothermia in its recommendations for comatose survivors of CA due to ventricular fibrillation (VF).3 Despite the strength of the available data, recent surveys assessing current intensive care unit (ICU) practices consistently show disappointing rates of hypothermia utilization in this patient population.4-6
Of 2,248 physicians who responded to a Web-based survey, most of whom were from the United States (91%), 74% said they had never used hypothermia in the postresuscitation period.4 The main reasons for nonuse were:
• Insufficient data available
• Technically too difficult to implement
• Not included in Advanced Cardiac Life Support (ACLS) guidelines
The Data
Two main trials support the use of mild hypothermia after CA: the multicenter European Hypothermia After Cardiac Arrest (HACA) trial1 and a single-center trial from Melbourne, Australia.2 Both trials included patients with out-of-hospital CA due to VF or pulseless ventricular tachycardia (VT) and excluded patients with refractory cardiogenic shock. The HACA trial randomized 275 patients and cooled the treatment group to 32 to 34°C for 24 hours. The primary endpoint of good neurological outcome and secondary endpoint of 6-month survival improved in the hypothermia group compared to the standard therapy group (55% vs 39%, p=0.009; and 59% vs 45%, p=0.02, respectively). The smaller trial from Australia included 77 patients cooled to 33°C for 12 hours. Again, good outcomes (patients discharged to home or to a rehabilitation facility) were more frequent in the treatment arm compared to controls (49% vs 25%, p=0.046, respectively).
The benefit of hypothermia for CA observed in these trials has been replicated in single-center studies describing the integration of cooling protocols into routine ICU clinical practice. A retrospective Swiss study of 43 patients cooled after CA due to VF, which included those with cardiogenic shock, showed higher rates of good outcome at hospital discharge compared to matched controls (56% vs 26%, p=0.004).7 A similar retrospective study compared 32 cooled CA patients with antecedent controls. Again, survival at hospital discharge was higher in the hypothermia group (56% vs 36%, p=0.04).8 These single-center reports reinforce the feasibility and clinical impact of implementing hypothermia protocols after CA in real-life ICU settings.
The European Resuscitation Council (ERC) published results of a registry established to monitor developments in medical practice after the ILCOR recommendations for hypothermia in the post resuscitation period. Of 650 patients admitted after CA and entered into the registry, 462 (79%) were treated with therapeutic hypothermia. Of these, 347 (75%) were cooled with an endovascular device and 25% with other methods of surface cooling and cold fluids.9
The Education Gap
Interestingly, U.S. physicians who responded to the Web survey also reported that technical difficulty prevented them from using hypothermia. This may reflect an “education gap” as until very recently, therapeutic hypothermia was not considered part of routine ICU practice. Older methods of surface cooling, such as ice packs and conventional cooling blankets, can be very labor intensive, messy and inefficient. Newer surface and intravascular cooling devices are more efficient and can simplify the cooling process. These devices enable faster induction and steadier maintenance of hypothermia, can ease the process of rewarming, and can reduce nursing workload. The main challenge in using these methods is control of shivering, which dramatically increases cerebral and systemic metabolic demand, increases cardiovascular stress, and causes discomfort.
Even with intensivists on board and modern devices available, cooling patients after CA can prove to be challenging. Organizing a multiprofessional, multidisciplinary effort across many departments is key. Implementing a hypothermia protocol for CA patients demands a coordinated effort involving the emergency department (ED), the ICU, the neurological ICU, nursing staff and hospital administration.
Initial measures of cooling, such as cold fluids,10 can be initiated in the ED until transfer to an ICU or the cardiac catheterization lab is possible. The ICU must be equipped with traditional or new devices for surface or intravascular cooling, and staff should be trained in their use to induce and maintain mild hypothermia.
The Implementation
Columbia University, New York, NY, USA, implemented a plan to address common problems in cooling CA patients. A “cool” pager was assigned to the neurological ICU fellow, who was notified every time a potential hypothermia patient was admitted to the ED. The pager was linked to the myocardial infarction beeper and cardiology fellow. To integrate ED and neurological ICU services and improve referral, emergency medicine residents began rotating in the neurological ICU and following patients cooled after CA. Finally, in the neurological ICU, nursing and medical staff received intense bedside training and continuing education reinforcing the concepts of shivering management and highlighting potential problems in hypothermia.
The criteria for cooling CA patients at Columbia University are shown in Table 1. The decision to cool usually is made by a consensus among the ICU, cardiology, and ED teams. The keys to success are prompt recognition by the ED staff as resuscitation proceeds, a prompt response by the ICU team, and a multiprofessional care team that is proficient and experienced in the application of hypothermia in the ICU.
References
1. The Hypothermia after Cardiac Arrest Study Group: Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest. N Engl J Med. 2002; 346:549.
2. Bernard SA, Gray TW, Buist MD, et al: Treatment of comatose survivors of out-ofhospital cardiac arrest with induced hypothermia. N Engl J Med. 2002; 346:557.
3. Nolan JP, Morley PT, Hoek TL, et al: Therapeutic hypothermia after cardiac arrest: An advisory statement by the Advancement Life support Task Force of the International Liaison committee on Resuscitation. Resuscitation. 2003; 57:231.
4. Merchant RM, Soar J, Skrifvars MB, et al. Therapeutic hypothermia utilization among physicians after resuscitation from cardiac arrest. Crit Care Med. 2006; Jul;34(7):1935.
5. Wolfrum S, Radke PW, Pischon T, et al. Mild therapeutic hypothermia after cardiac
arrest. A nationwide survey on the implementation of the ILCOR guidelines in German intensive care units. Resuscitation. 2007; 72, 207.
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6. Laver SR, Padkin A, Atalla A, et al. Therapeutic hypothermia after cardiac arrest: a survey of practice in intensive care units in the United Kingdom. Anaesthesia. 2006; Sep;61(9):873.
7. Oddo M, Schaller MD, Feihl F, et al. From evidence to clinical practice: effective implementation of therapeutic hypothermia to improve patient outcome after cardiac arrest. Crit Care Med. 2006; Jul;34(7):1865.
8. Belliard G, Catez E, Charron C, et al. Efficacy of therapeutic hypothermia after out-of-hospital cardiac arrest due to ventricular fibrillation. Resuscitation. 2007 Nov;75(2):252.
9. Arrich J and The European Resuscitation Council Hypothermia After Cardiac Arrest Registry Study Group. Clinical application of mild therapeutic hypothermia after cardiac arrest. Crit Care Med. 2007; Apr;35(4):1041.
10. Bernard S, Buist M, Monteiro O, et al.: Induced hypothermia using large volume, ice-cold intravenous fluid in comatose survivors of out-of-hospital cardiac arrest: A preliminary report. Resuscitation. 2003; 56:9.
Disclosures
* Authors have no disclosures to report
