Therapeutic hypothermia following out-of-hospital cardiac arrest (OHCA): an audit of compliance at a large Australian hospital

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1 Anaesth Intensive Care 2012; 40: Therapeutic hypothermia following out-of-hospital cardiac arrest (OHCA): an audit of compliance at a large Australian hospital S. A. McGloughlin*, A. Udy, S. O Donoghue, H. Bandeshe, J. R. Gowardman** Department of Intensive Care, Royal Brisbane Hospital, Herston, Queensland, Australia Summary Therapeutic hypothermia (TH) is now largely considered the standard of care for patients following out-ofhospital cardiac arrest caused by ventricular arrhythmias, although the effective implementation of TH for individual patients can be challenging. This study aimed to document the effectiveness of TH when it is used at the discretion of treating physicians and not under the auspices of a research trial or protocol. A retrospective review of intensive care unit admissions over a four-year period detected 43 patients appropriate for TH. In the emergency department, only 20% of patients had TH commenced. Forty-four percent of patients required angiography in the cardiac catheterisation laboratory. It took, on average, 595 minutes for patients to reach their goal temperature, which was not reached at all in 13% of patients. Nineteen patients (44%) had a positive neurological outcome while 24 patients (56%) either died or had a poor neurological outcome. Without the control of a hospital protocol it was apparent that the implementation of TH in patients with an out-of-hospital cardiac arrest in our institution was inadequate. We recommend that TH is undertaken within the framework of a protocol that encompasses all the relevant departments. Key Words: therapeutic hypothermia, cardiac arrest: neurological outcome Therapeutic hypothermia (TH) is considered a key component of care for patients following out-of-hospital cardiac arrest (OHCA) caused by ventricular fibrillation. The effectiveness of TH has been demonstrated in clinical trials that commenced therapeutic cooling both in the pre-hospital care setting 1 and on arrival in the emergency department (ED) 2. The benefit of TH after cardiac arrest on inhospital mortality and neurological outcome has been confirmed in systematic reviews 3,4, although there is some debate within the intensive care community as to the use of TH 5. The institution of mild hypothermia (32 34 C) is now included in international guidelines on the management of cardiac arrest, including those of the International Liaison Committee on Resuscitation, the European Resuscitation Council and the Australian Resuscitation Council 6 8. TH is defined by the Australian Resuscitation Council as the cooling of a comatose adult patients, * BSc (Hons), FRACP, FCICM, BMed, MPH&TM, PGDip (ECHO), Consultant Intensivist. MB, ChB, FCICM, Consultant Intensivist. MB, ChB, FANZCA, FCICM, Consultant Intensivist. BSc, BEng, Database Manager. ** MB, ChB, FRACP, FCICM, Senior Intensivist. Address for correspondence: Dr S. A. McGloughlin. S.McGloughlin@alfred.org.au Accepted for publication on June 4, with spontaneous circulation after an out-of-hospital ventricular fibrillation cardiac arrest, to C for hours 8. However, for it to be effective intervention, hospitals must be able to implement appropriate TH in individual patients in a rapid and effective manner outside a research study protocol. Sunde and Storm demonstrated the effectiveness of TH with a target temperature of 33 C when outcomes of patients treated with hypothermia were compared to historical controls in terms of mortality benefits and a decreased length-of-stay 9,10. TH adds other challenges in regard to cooling patients during other vital components of post-cardiac arrest care, including percutaneous coronary intervention. TH has, however, been successfully implemented in patients who are undergoing percutaneous coronary intervention and even intra-aortic balloon counterpulsation 11. The practical implementation of TH (32 34 C) adds considerable complexity to the care of patients post-ohca. Oddo 12 demonstrated a benefit of TH on outcomes despite a median delay of five hours from arrival in the ED before a goal temperature of 33 C was reached. The aim of this study was to document the effectiveness of the implementation of TH when the treatment is under the control and discretion of treating physicians and not the auspices of a prospec-

2 Compliance with therapeutic hypothermia after OHCA 845 tive trial or even a hospital-specific protocol. We did this by documenting the neurological outcome of postcardiac arrest patients treated with TH, the success of the provision of hypothermia to these patients in terms of proportion of time they were maintained in their goal temperature range and the time it took for patients to reach their goal temperature. MATERIALS AND METHODs Setting This retrospective observational study was undertaken in a large quaternary hospital, a major referral centre for the region. The local institutional human research ethics committee approved the study. The facility has a fully-equipped ED with on-site specialist cover in addition to an active interventional cardiology service. The intensive care unit (ICU) provides 30 beds with a full range of organ support modalities. Patient cohort All patients admitted to the ICU after sustaining an OHCA between 1 January 2004 and 1 January 2008 were screened for inclusion in the study. Only those patients with documented ventricular fibrillation or ventricular tachycardia as the primary cause and with an altered level of consciousness, no meaningful motor response elicited and thus intubated after return of spontaneous circulation were included. Other forms of OHCA were excluded. Aspects of care delivered All patients were initially admitted to the ED where, after assessment and commencement of appropriate therapy (including verification of initial rhythm from pre-hospital records, resuscitation, stabilisation and institution of both cardiac-specific and general supportive therapies), they were transferred to the ICU via the cardiac catheterisation laboratory (CCL), if needed. The decision as to whether a patient required cardiac catheterisation was based on clinical assessment from a consultant cardiologist including review of the patient s initial cardiac rhythm, current electrocardiogram and clinical status. During the period of the review, TH was not under the auspices of a study designed protocol, although it was generally accepted as a core component of care for patients meeting the above criteria 5. Excluded patients were those with significant haemodynamic instability, including cardiogenic shock, or those in whom the prognosis was thought to be extremely poor. Induction of TH was at the discretion of the treating physician. Pre-hospital therapeutic hypothermia is not performed in our region. Available methods included cooling blankets, ice packs and cold intravenous fluids. TH as an intervention was assessed in this study outside a treatment protocol, and therefore both the duration of TH (12 24 hours) and the specific goal temperature were at the discretion of the treating intensivist. In all cases this goal temperature was between 32 and 34 C. The core temperature was recorded in the ICU from calibrated bladder catheters or nasopharyngeal probes (Foley-Temp or Mon-a-therm Thermistor temperature probe, Tyco Healthcare, Pleasanton, CA, USA). Data acquisition A thorough chart review was completed for each patient meeting inclusion criteria. Baseline information included age, sex and chronic disease status. Data was then collected for the time patients were under the care of the ambulance service, the ED, the ICU and, if appropriate, the coronary care team. In each instance, data was also collected as to the method of cooling, effectiveness of TH (time to onset of temperature less than 34 C), and the percentage of time in the first 12 or 24 hours of treatment that the patient s temperature was maintained in the target range. Neurological outcome was assessed at patient discharge from the hospital and was based on the Glasgow Outcome Scale (GOS). The outcome was considered unfavourable if patients scored 1 3 and good if they scored Statistical analysis Continuous data are presented as mean (standard deviation [SD]). Categorical data are presented as counts and/or percentages. An independent Student s t-test was employed to compare the mean fraction of time spent at goal temperature during the therapeutic window as a function of neurological outcome. A p value <0.05 was considered statistically significant. RESULTS Between 1 January 2004 and 1 January 2008, 178 patients were admitted to the ICU with a diagnosis of cardiac arrest. Eighty-four of these had suffered an in-hospital arrest and 12 patients had been transferred from another institution and were therefore excluded. Another 38 patients did not meet the inclusion criteria and were also excluded, leaving 43 patients in which data was available. The characteristics of these 43 patients are presented in Table 1. The mean age was 60.5±14.41 years with an average time to return of spontaneous circulation of 19.7±11.45 minutes. Despite being considered a core component of care, TH was discussed and commenced in ED in

3 846 S. A. McGloughlin, A. Udy et al only 20% of the patients studied. Patients arrived in the ICU on average three hours and 51 minutes after their arrival in the ED, although this fell to a mean of three hours and 16 minutes for patients who did not need coronary angiography (24 patients). In the ED only four patients (9%) reached their documented goal temperature. In the ICU all patients except two were treated with TH aiming for a goal temperature of C. Passive cooling via a cooling blanket and ice was used in all TH patients. Paralysis with muscle relaxants and sedation with opiates and benzodiazepines was used to aid cooling by reducing shivering in all except five patients. It took on average nine hours and 55 minutes (595 minutes) for patients to reach their goal temperature after their admission to the ED. The cumulative proportion of patients reaching their target temperature range per hour after their arrival in ED is Table 1 Characteristics of included patients (n=43) Characteristic Number (%) Male 38 (88%) History of ischemic heart disease 16 (37%) VF arrest 42 (98%) Witnessed arrest 39 (90%) Received bystander CPR 41 (95%) Intubated at scene 37 (86%) VF=ventricular fibrillation, CPR=cardiopulmonary resuscitation. demonstrated in Figure 1. Fifty percent of patients had reached their goal temperature 12 hours after admission to the ED. Thirteen percent of patients did not reach their goal temperature within the prescribed period of therapy. Nineteen patients (44%) were transferred to the CCL before the ICU and 13 of these patients had therapeutic angioplasty performed. Documentation of patients temperatures and vital signs was often incomplete in the CCL, and the records do not indicate any systematic efforts to maintain TH in any patient. This may simply indicate poor documentation but may demonstrate that during this period efforts to maintain TH were suspended. In the ICU, patients were maintained at their goal temperature for only 51% of the prescribed period, whether 12 or 24 hours as per the treating physician. When time in the ED, CCL and ICU are taken into account, patients were maintained at the goal temperature of between C for a mean of only 43.2% of their prescribed time. Twenty-two patients (51%) died while in hospital and two other patients had an unfavourable outcome in that they were severely disabled on hospital discharge (GOS 3). Therefore, 19 (44%) had a good outcome in that they were either discharged or were capable of independent care (GOS 4 or 5). Patients who had a good outcome spent more time on average at their goal temperature (52.7% of the therapeutic window), compared with those who had an unfavourable outcome (35.8%, P <0.05). Figure 2 displays the mean time patients spent at their goal Cumulative percentage of patients reaching goal temperature Hours post-admission to ED Figure 1: Cumulative percentage of patients reaching goal temperature following admission to ED. ED=emergency department.

4 Compliance with therapeutic hypothermia after OHCA 847 Mean percentage of time at goal temperature Favourable Unfavourable Favourable Unfavourable Cardiac catheterisation No cardiac catheterisation Figure 2: Mean percentage of time at goal temperature related to outcome. temperature referenced to outcome and to need for cardiac catheterisation. Five patients who had an unfavourable outcome never reached the goal temperature, whereas no patient in the good outcome group did not reach the goal temperature. From the retrospective data available it was difficult to attribute side-effects to TH. Six patients developed sepsis while in the ICU as defined by a systemic inflammatory response syndrome which was treated with antibiotics, and 12 patients developed an arrhythmia that required intervention of either electrical defibrillation or an anti-arrhythmic medication such as amiodorone. DISCUSSION This study demonstrates the difficulty of implementing TH in a major teaching hospital. The landmark studies which led to the recommendation of TH were aggressive in instituting TH either in the ambulance or in the ED 1,2. In the study by Bernard et al, patients were aimed to be cooled for 12 hours with active rewarming at 18 hours. From the published data, not only did the study lead to a significant improvement in neurological outcome but the study protocol was successful in implementing this therapy in a group of highly selected patients as demonstrated by their mean temperature data at six (32.7 C) and 12 hours (33.1 C) after admission (target 33 C) 1. In the study performed by the Hypothermia After Cardiac Arrest Study Group, the target temperature was between C with the aim of maintaining this for a period of 24 hours 2. In addition, the goal was to reach this temperature within four hours of the return of spontaneous circulation, although the median reported time to reach goal temperature was eight hours and in 19 of the 137 patients the target temperature was not reached at all. Fifty-five percent of patients who were treated with hypothermia had a favourable neurological outcome as opposed to 39% in the normothermia group 2. TH has not been universally adopted. In a survey of Canadian emergency and intensive care physicians, the use of TH in cardiac arrest patients was only 68% 14. However in the UK, 85% of ICUs were using TH in the treatment of cardiac arrest patients 15. Multiple reasons for the variable uptake have been suggested, including significant logistical and staffing problems and the lack of standardised protocols 16. Additionally, the evidence supporting its role is conflicted 5 7. Our study suggests that relying on physicians to implement an appropriate evidence-based treatment such as TH in OHCA does not lead to its effective use in terms of reaching satisfactory therapeutic goals. Without reaching these therapeutic goals it is unlikely that any potential benefits in regard to mortality and neurological outcome can be obtained. In this audit the time to reach goal temperature was 595 minutes (9.9 hours), which is significantly longer than the previously mentioned major studies. A major retrospective review in Scandinavian ICUs found that the average time to commencement of TH was 90 minutes and the time to reach goal temperature was 260 minutes 17. This raises the question of whether alternative devices should be used to expedite cooling. In a European review of 19 ICUs, 79% of 650

5 848 S. A. McGloughlin, A. Udy et al patients who were treated for cardiac arrest received TH. Of the patients treated with TH, 75% were cooled with an endovascular device. The time to initiate cooling was significantly longer in patients who received endovascular cooling as opposed to more passive methods 16. More complex cooling methods are likely to complicate the process further and may even postpone the commencement of TH. Of note, Whitfield et al in an Australian institution was able to manage TH within six hours using infusion of cold saline in 90% of patients 18. As patients progress through the care of ambulance officers, the ED, the ICU and the CCL when required, early onset of TH may be difficult to institute. Despite this hurdle, a number of authors have demonstrated effective use of TH while patients are in the CCL 11,19,20. In our institution, the use of TH in this setting was significantly less effective than in the ICU. It is apparent that while patients are undergoing cardiac catheterisation, their temperature needs to be documented, and that the supervising anaesthetist or intensivist could possibly institute more active therapeutic measures to initiate or maintain TH. A number of adverse events have been reported from TH, including an increased risk of infection, coagulopathy, hyperglycaemia and arrhythmias. In this retrospective study we reviewed the risk of infection and arrhythmias in those patients who were treated with TH. The incidence of both of these complications was consistent with those published in previous studies. Due to the retrospective nature of this study only very limited conclusions can be made as regards such complications. Despite the noted limitations, the neurological outcome of patients in our study appeared consistent with those from previous major studies and published audits. However, the actual implementation of TH was relatively poor; if the application of this intervention is improved, the neurological outcomes of our patients may also improve. The systematic review by Holzer suggested that the number needed to treat for one additional patient to leave hospital with a favourable neurological outcome is between four and It is therefore vital that TH be implemented, in the appropriate clinical scenario, in a manner that is efficient and safe. This review shows that implementation of this intervention (as patients move from the ambulance, through the ED to the ICU) needs significant improvement. The process needs to be commenced earlier, be communicated more effectively and documented appropriately. As the effects of TH are potentially so significant, the development of a protocol for individual facilities is vital and likely to improve the implementation and process of this important therapy 21. Perhaps this review s most important finding is that the implementation of a potentially life-saving intervention which requires the co-operation and efforts of a multitude of physicians and departments may require the institution of a specific and agreed-upon protocol. References 1. Bernard SA, Gray TW, Buist MD, Jones BM, Silvester W, Gutteridge G et al. Treatment of comatose survivors of outof-hospital cardiac arrest with induced hypothermia. N Engl J Med 2002; 346: Hypothermia after Cardiac Arrest Study Group. Mild therapeutic hypothermia to improve the neurologic outcome after cardiac arrest. N Engl J Med 2002; 346: Cheung KW, Green RS, Magee KD. Systematic review of randomized controlled trials of therapeutic hypothermia as a neuroprotectant in post cardiac arrest patients. CJEM 2006; 8: Holzer M, Bernard SA, Hachimi-Idrissi S, Roine RO, Sterz F, Mullner M. Hypothermia for neuroprotection after cardiac arrest: systematic review and individual patient data metaanalysis. 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