Is it worth packing the head with ice in patients undergoing deep hypothermic circulatory arrest?

Abstract

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was: Is it worth packing the head with ice in patients undergoing deep hypothermic circulatory arrest (DHCA)? Altogether more than 34 papers were found using the reported search, of which 7 represented the best evidence to answer the clinical question, 5 of which were animal studies, 1 was a theoretical laboratory study and 1 study looked at the ability to cool using circulating water 'jackets' in humans. There were no available human studies looking at the neurological outcome with or without topical head cooling with ice without further adjunct methods of cerebral protection. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. Four papers studied animals undergoing DHCA for 45 min-2 h depending on the study design, with or without packing the head with ice. The studies all demonstrated improved cerebral cooling when the head was packed with ice during DHCA. They also illustrated an improved neurological outcome, with better behavioural scores (P < 0.05), and in some, survival, when compared with animals whose heads were not packed in ice. One study examined selective head cooling with the use of packing the head with ice during rewarming after DHCA. However, they demonstrated worse neurological outcomes in these animals, possibly due to the loss of cerebral vasoregulation and cerebral oedema. One study involved a laboratory experiment showing improved cooling using circulating cool water in cryotherapy braces than by using packed ice. They extrapolated that newer devices to cool the head may improve cerebral cooling during DHCA. The final study discussed here demonstrated the use of circulating water to the head in humans undergoing pulmonary endarterectomy. They found that tympanic membrane temperatures could be maintained significantly lower than bladder or rectal temperatures when using circulating water to cool the head. We conclude that topical head cooling with ice is of use during DHCA but not during rewarming following DHCA and that it may be possible to advance topical head cooling techniques using circulating water rather than packed ice.

Highlights from the International Chronic Thromboembolic Pulmonary Hypertension Congress 2021

“…DHCA is required to perform PEA surgery. The general anaesthetic set-up for DHCA does not differ significantly from other complex surgery, and it must include meticulous heparinisation, gradual (slow) institution of hypothermia and external head cooling to avoid re-warming during DHCA [ 58 , 59 ]. Although steroids are commonly used for DHCA, there is no evidence that they provide additional neuroprotection or show a risk reduction in reperfusion injury after PEA surgery [ 60 ].…”

Perioperative Management in Pulmonary Endarterectomy

“…During DHCA, it is important to place a headcooling device to avoid rewarming of the superficial cerebral cortex. 100 There are many strategies to avoid cerebral ischemia during circulatory arrest; however, Vuylsteke et al showed that the neuroprotection of DHCA was comparable to antegrade cerebral perfusion and there was no difference in neurocognitive outcomes at 1 year in CTEPH patients undergoing PEA. 30 The use of steroids is routinely used for DHCA for aortic dissections and other complex cardiac surgery; however, there is no strong evidence that supports their benefits in terms of additional cerebral protection or reduction in lung reperfusion injury following PEA.…”

“…During DHCA, it is important to place a head-cooling device to avoid rewarming of the superficial cerebral cortex. 100 There are many strategies to avoid cerebral ischemia during circulatory arrest; however, Vuylsteke et al showed that the neuroprotection of DHCA was comparable to antegrade cerebral perfusion and there was no difference in neurocognitive outcomes at 1 year in CTEPH patients undergoing PEA. 30…”

Perioperative management of thoracic and thoracoabdominal aneurysms

“…Application of topical cooling to the head is performed in some centres to minimise passive warming, although the benefits of this have been extrapolated from studies in animals. 10 Where used, particular care should be taken to protect the patient's eyes. Opinions vary on the degree of hypothermia required.…”