Do We Successfully Achieve Therapeutic Hypothermia?

Abstract

spontaneous circulation, but remain unconscious.[1] The recommendation for TH is largely based on the results of two randomized, prospective studies. One of these studies involved the use of a mattress to deliver cold air and ice packs to induce TH at 32-34℃ for 24 hours in five European countries. After TH, rewarming was performed slowly. Fifty-five percent of the hypothermia group demonstrated good neurological outcome, whereas only 39% of the control group exhibited good neurological outcome.[2] In another study conducted in Australia, ice packs were placed around the head and body of patients to induce TH at a targeted temperature of 33℃ for 12 hours, and active rewarming began at 18 hours. Induced TH resulted in improved neurological outcome in 49% of the hypothermia group, while the same outcome was seen in only 26% of the control group.[3] In these two studies, induced TH effectively improved neurological outcome in patients with ventricular fibrillation out-of-hospital cardiac arrest. However, it has not yet been established whether TH is an effective treatment strategy for CA patients presenting with nonshockable rhythm, such as pulseless electric activity and asystole.[4,5] In addition, researchers are divided in their opinions on various elements of TH, including appropriate target temperature, cooling methods and period, and rewarming speed, calling for further studies. When performing TH, we strive to take a simple and minimally invasive approach in order to cool the body quickly and easily. External cooling techniques such as cooling blankets and helmets or ice bags are typically used at the beginning of treatment. Endovascular cooling has also been used to provide faster cooling and a steady maintenance phase via a cooling catheter introduced into the central venous system and a water-circulating cooling device. Different cooling methods vary in times of initiation of cooling, achievement of the target temperature and maintenance of TH. However, neurological recovery and mortality rates do not appear to vary significantly based on the cooling method used.[6,7] Recently, amid increasing recognition of its fast cooling effect, a large-volume (30 mL/kg), ice-cold (4℃) intravenous fluid infusion is widely used in the early stage of TH along with other cooling methods.[8] Rates of cooling and rewarming are the most important factors to consider when performing