HHE Emergency care supplement 2018 - Page 20

emergency and critical care Targeted temperature management for cardiac arrest This review aims to look at the theory behind targeted temperature management and how it is applied clinically, with attention to new research in this field and its impact on patient survival and neurological recovery Ben Avery MBBS BSc (Hons) MRCP Specialist Registrar Anaesthetics Melinda Brazier MBBS FRCA FFICM Consultant Anaesthesia and Critical Care St Peter’s Hospitals NHS Trust, UK In England in 2013, there were 28,000 cases where emergency medical services (EMS) were called to attempt resuscitation for out of hospital cardiac arrest (OHCA). 1 Other large studies give an incidence of OHCA of approximately 80 per 100,000 patient years. 2 Worldwide, this figure is significantly higher than in Asia but falls slightly behind the USA and Australia. 2 These numbers are only the amount of cases where EMS were called to OHCA, not how many were treated, or indeed how many had a cardiac cause, or how many of those with cardiac cause were found to be in ventricular fibrillation (VF). This is important as there are positive survival rates associated with VF cases of OHCA versus any other. 3 Mild therapeutic hypothermia (MTH), or targeted temperature management (TTM) as it is now more commonly known, has been established for the post-resuscitation care of OHCA since two pivotal studies in 2002. 4,5 In the UK, it is incorporated into Resuscitation Council guidelines as the fourth link in the chain of survival (post-resuscitation care; Figure 1). This was supported by the International Liaison Committee on Resuscitation (ILCOR) in 2015. 6 This review aims to look at the theory behind TTM and how it is applied clinically, with attention to new research in this field and what impact TTM has on patient survival and neurological recovery. Previous work and history Hippocrates and the Persian army had already commented on the protective nature of cold for centuries before Napoleon’s chief surgeon, Dominique Jean Larrey, documented that injured soldiers kept closer to the fire died more frequently than those kept away. 7 Studies from the middle of the 20th century looked into MTH following both severe head injury and cardiac arrest, 8,9 but the results were uncertain and not incorporated into standard practice. Pivotal case reports exist of survival from acute hypothermia with intact neurology, possibly none more dramatic than that of Anna Bagenholm, trapped under the ice in Norway for 80 minutes after a skiing accident in 1999, and surviving to this day to work as a doctor. Her core temperature was recorded at 13.7°C on arrival at hospital, and her heart started after slow rewarming on cardiac bypass. It is only in the last 15–20 years that studies have progressed to looking not only at survival rates post-OHCA but also what degree of neurological deficit exists after TTM is instigated. Mechanism of protection Understanding that the damage to the brain occurs after cardiac arrest from hypoxia is paramount. There is no substitute for early recognition, early CPR and early defibrillation as laid out by the Resuscitation Council to reduce figure 1 Chain of survival – Resuscitation Council Early recognition and call for help To prevent cardiac arrest Early CPR To buy time 20 HHE 2018 | hospitalhealthcare.com Early defibrillation To restart the heart Post resuscitation care To restore quality of life