Therapeutic Hypothermia after Out-of-Hospital Cardiac Arrest - implementation and clinical management
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Background: With the publication of two randomized controlled trials (RCTs) in 2002, therapeutic hypothermia (TH) was re-introduced in postresuscitation care of comatose out-of-hospital cardiac arrest (OHCA) patients. Many issues, however, were unresolved, including implementation protocol, cooling technique, clinical management, implications of TH treatment on prognostic accuracy and therapeutic benefit in subgroups of OHCA excluded from the initial RCTs. Objectives: We wanted to study the implementation of therapeutic hypothermia into daily practice, provide information on clinical management, including differences in cooling techniques and test application in elderly OHCA patients excluded in earlier trials.
Subjects: We evaluated the clinical management of adult comatose OHCA patients who were treated in our ICU (paper I and IV). In paper II we surveyed our intensive care nursing staff with regard to key nursing aspects of different cooling methods and devices. In paper III, ICU consultants were assessed on their prognostic approach in OHCA patients treated with TH.
Methods: In paper I we retrospectively compared OHCA patients treated with TH with a historic control group of OHCA patients fulfilling the TH inclusion criteria. We collected Utstein template data, as well as data on ICU-and hospital length of stay (LOS), incidence of adverse events, and outcome at hospital discharge and after one year. In paper II an anonymous survey was conducted with our intensive care nursing (ICN) staff, assessing ease of application, hygiene, work load, noise level and visual patient monitoring of four different cooling methods. In paper III we used a semi-structured telephone interview to conduct a nation-wide survey of the prognostication approach of comatose OHCA patients involving timing, methods, involved specialties and rating of prognostic methods. In paper IV we retrospectively studied outcome variables in all adult OHCA patients treated with TH in our ICU over a six-year period, who fulfilled the Hypothermia After Cardiac Arrest study (HACA) criteria with exception of the upper age limit. Results: With our simple cooling protocol we achieved 100% implementation and successful attainment of target temperature (TT) in 89% of patients (paper I). However, it took median 7, 5 hours (1-10 h) to reach TT, which was maintained for median 10 hours (6-19h). Demographics, Utstein template data, ICU and hospital LOS did not differ significantly between the two groups. Insulin resistance and hypokalemia were significantly more frequent in the TH group, whereas seizures were observed more frequent in the normothermia group. The TH group showed significantly higher rates of survival to hospital discharge (59% vs. 32%, p = 0, 05). In paper IV we found that although older age influenced outcome, over half of OHCA patients older than 75 years showed favorable outcome at hospital discharge. The four cooling methods used in our department differed significantly regarding key nursing aspects (paper II). Our simple cooling method scored high regarding ease of application and noise level, but low in work load and hygiene. The CoolGard and ArticSun systems scored highest in work load and hygiene. Only 53% of ICNs were satisfied with their initial training and merely 10% felt adequately prepared at the time when TH was introduced. In paper III we found that even after introduction of TH, prognostication after OHCA was performed within 48 hours in the majority of patients. More than one specialty was involved, using mainly clinical neurological examination (100%), prehospital data (76%), cerebral computer tomography (CCT) (58%) and electroencephalography (EEG) (52%) findings. Somatosensory evoked potentials (SSEP) (8%), biochemical markers (8%) and magnetic resonance imaging (MRI) (8%) only played a minor role. Only one ICU used a standardized protocol.
Conclusions: Our simple external cooling protocol could be rapidly implemented, was safe, cheap and feasible, but not optimal with regard to accurate temperature management (paper I). Key nursing elements differed significantly among available cooling methods (paper II). Even though age influences outcome, more than half of our OHCA population older than 75 years showed good outcome. The limitation of patient eligibility for TH treatment should not be based on age alone (paper IV). Despite frequent use of TH, prognostication after OHCA was executed early, mainly based on clinical examination, prehospital data, CCT and EEG results. SSEP seems to be underused and underrated, whereas the clinical accuracy of CCT, prehospital data and EEG seems to be overrated (paper III).