Targeted Temperature Management in Cardiac Arrest: An Updated Narrative Review

Abstract

The established benefits of cooling along with development of sophisticated methods to safely and precisely induce, maintain, monitor, and reverse hypothermia have led to the development of targeted temperature management (TTM). Early trials in human subjects showed that hypothermia conferred better neurological outcomes when compared to normothermia among survivors of cardiac arrest, leading to guidelines recommending targeted hypothermia in this patient population. Multiple studies have sought to explore and compare the benefit of hypothermia in various subgroups of patients, such as survivors of out-of-hospital cardiac arrest versus in-hospital cardiac arrest,

Effectiveness of Induced Hypothermia on the Prognosis of Post-cardiac Arrest Patients: A Scoping Literature Review

“…A study done by Kashiwagi et al showed that plasma BNP levels significantly increased more than five-fold during TH but heart failure did not worsen; this study can give further insight on improving newer therapeutics under TTM [ 13 ]. If a survivor is comatose, TTM should be considered regardless of the initial presenting rhythm; TTM has shown certain cardioprotective effects like preserving left ventricular function, protecting contractility, and preventing microvascular obstruction [ 14 ]. Delaying the time to initiate TTM after the ROSC increases the mortality of patients by 20% [ 15 ].…”

“…A CA survivor bears the risk of neuronal injury via hypoxic-ischemic insult and reperfusion damage, hypothermia mainly preserves high phosphate substrates such as adenosine triphosphate and maintains the pH in the brain [ 15 ]. Hypothermia improves neurogenesis, angiogenesis, and gliogenesis after injury; preserves the integrity of the blood-brain barrier and aquaporin channels [ 14 ]. Lee et al in Korea proved that despite the increase in downtime of more than 30 minutes to achieve the ROSC and age less than 70 years, TTM improved neurological outcomes of out-of-hospital CA patients, the effectiveness of hypothermia shouldn’t be ruled out of post-resuscitation care [ 16 ].…”

“…The clear difference in the mechanism between both methods points out that SCDs have an increased risk of temperature fluctuations; errors in SCDs can lead to intermittent brain hyperthermia [ 28 ]. ICDs offer better temperature control during rewarming and less shivering, however, intravascular catheter placement is expensive and carries a risk of thrombosis, insertion-related bleeding, and bloodstream infection which can lead to sepsis and shock [ 18 , 14 ]. A combination of SCD and ICD has shown better results in attaining rapid cooling, maintaining control of target temperature, and minimizing shivering.…”

“…The current method used is the measurement of the temperature of blood using a pulmonary artery catheter considered the gold standard. Other methods used to monitor temperature include bladder, rectum, esophagus, and tympanic membrane sites but they carry a risk of time lag between recorded temperature and actual core temperature due to constant temperature changes in the induction phase [ 14 , 12 ].…”

“…During this phase core body temperature is cautiously raised at the rate of 0.15°C-0.25°C per hour until it is higher than 36°C and controlled by rewarming devices as spontaneous rewarming exacerbates neurological injury and can lead to the risk of post-TTM hyperthermia [ 12 ]. Duration of rewarming depends on the prognosis of patients and response to TTM during induction, it can start from 12-24 hours after initiating induction and take up to 8 hours [ 12 , 14 ]. The rewarming phase should be done slowly to avoid spikes in intracranial pressure, this will cause hypothermia-induced vasoconstriction to reduce and a change to hypovolemia with hypotension is seen.…”