FEATURE SURGERY 059 The crucial role of
TherapeuTic hypoThermia in posT cardiac arresT care
By: Ralph Marktanner and Hubert Hon, Sheikh Khalifa Medical City managed by Cleveland Clinic (SKMC), Abu Dhabi, UAE
INTRODUCTION Cardiac arrest (CA) remains a condition associated with high morbidity and mortality due to cerebral ischemic injury despite successful resuscitation. CA survival remains unchanged over the last years despite better access to public defibrillators and increasing efforts to improve CPR skills of the general population as potential first responders. Overall, only 10% of victims of out-of-hospital cardiac arrest (OOHCA) are discharged alive from hospitals and recovery is rare without residual neurological damage. Many CA survivors remain in a vegetative state for the rest of their lives, with major impact on life quality for both the patients and relatives placing significant burden on families and healthcare financial resources.
HISTORICAL BACKGROUND The medical understanding, that decreasing a patient’s core temperature is beneficial for certain critical conditions was identified by Hippocrates (460-377 BC), who advised to surround badly wounded soldiers with snow and ice. D.J. Larrey (1766-1842), a military physician in the Napoleonic Wars and private physician of Napoleon Bonaparte observed, that wounded soldiers died earlier when put close to a campfire, compared to those who were not rewarmed. In the 1960’s, Dr. Peter Safar (1924-2003), an Austrian-American pioneer in emergency and resuscitation medicine and known as the ‘father of
other critical care conditions that could possibly benefit from cooling e.g. traumatic brain and spinal cord injury and postpartum asphyxia. Research was also conducted to control possible complications associated with cooling, and pharmacological aspects, timing and duration of the cooling period.
TECHNICAL ASPECTS OF COOLING Cooling can be applied either externally (surface cooling) or internally (invasive cooling). In the early days of clinical therapeutic hypothermia (TH) application, patients mostly received a combination of internal cooling via infusion of cold fluids in order to achieve rapid cooling induction and external cooling, such as application of coldpacks or icebags to the patient’s surface in order to maintain the decreased temperature. There was a huge variation in clinical practice to achieve temperature decline and maintain the hypothermic state. Methods include cold-water immersion, urinary bladder flushes and peritoneal lavage. These variations in external and internal cooling techniques are very labour-intensive. They are also associated with complications such as freezing injuries, increased shivering response and are unsatisfactorily inaccurate in terms of targeting and maintaining a defined hypothermic temperature range or achieving a controlled rewarming phase. Today, a variety of easy to operate purpose designed cooling devices are available, using either a surface cooling or invasive cooling
“only 10% of vicTims of ouT of hospiTal cardiac arresT (oohca) are discharged alive from hospiTals”
cardiopulmonary resuscitation’ recommended we not only think of resuscitation as an attempt to reestablish cardiopulmonary functions, but to understand we are resuscitating the brain as well at the same time. To quote Dr. Safar: “Saving the heart and lungs would have little value, if the brain was not similarly protected”. Dr. Safar promoted the application of hypothermia in his heart/lung resuscitation algorithm published in 1964 for post CA care in order to achieve better recovery of the ischemic brain. In 2002, two landmark studies affirming the beneficial role of post
CA cooling were published in the New England Journal of Medicine. Both studies applied similar methodologies, where mortality rates and neurological outcomes were compared between post CA patients treated either with a period of mild hypothermia or were provided only with conservative management. Both studies demonstrated clear survival and neurological outcome benefits. These publications created world-wide interest in post CA cooling and initiated further clinical and experimental studies. Further research was also stimulated in
approach. Furthermore, several portable devices are now available for deployment at the CA scene in order to start cooling as early as possible. All of these devices add a tremendous level of convenience and confidence for healthcare providers in order to make cooling quick, reliable and easy to use.
CURRENT GUIDELINES AND RECOMMENDATIONS In 2003, an advisory statement by the Advanced Life Support Task Force of the International Liaison Committee on Resuscitation (ILCOR) recommended, unconscious adult patients with spontaneous circulation after OOHCA be cooled to 32°C to 34°C for 12 to 24 hours when the initial rhythm was ventricular fibrillation (VF). It was furthermore stated that such cooling may also be beneficial for other rhythms or in-hospital CA. Despite this clear statement, an internet based survey published in 2006 to report the utilization of TH after resuscitation from CA among physicians in the US, the UK and Finland found 74% of US respondents and 64% of non-US respondents had never
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