Therapeutic Hypothermia for Increased Intracranial Pressure after Decompressive Craniectomy: A Single Center Experience

Anaesthetic management in a cat undergoing emergency craniotomy for meningioma excision

Case summary

A 15-year-old female spayed domestic shorthair cat underwent an emergency craniotomy to remove an intracranial meningioma causing marked midline shift, caudal transtentorial and foramen magnum herniation. Because intracranial structures are enclosed in the cranium, any volume-occupying lesions might raise intracranial pressure (ICP), compromising cerebral perfusion.

Relevance and novel information

This case report discusses the anaesthetic management of a cat that presented with marked bradycardia and concomitant hypotension. Cushing's reflex (CR) is a well-recognised cardiovascular reflex following sudden ICP increase, and it features an irregular breathing pattern and increased arterial blood pressure with reflex bradycardia. However, CR is reported to have a low sensitivity for the detection of raised ICP in humans with traumatic brain injury. In a previous study reporting seven cats undergoing surgical removal of intracranial meningioma, ICP was measured in four cases and, in these patients, CR was not observed during surgery. Because bradycardia was not secondary to hypertension, in this case, it might have been the result of direct compression of the nucleus of the vagus nerve. Based on the literature search, there is paucity of reports of cardiovascular changes in cats with increased ICP and their perianaesthetic management.

Systematic review exploring the effect of therapeutic hypothermia on patients with intracranial hypertension

Background:

Intracranial hypertension is found in patients with various neurological and neurosurgical conditions such as subarachnoid hemorrhage (more than 50% of the patients have intracranial pressure > 20 mmHg at some point during their hospital stay), traumatic brain injury, and stroke. Various modalities are used to control intracranial hypertension, therapeutic hypothermia is one of them. This systematic review aims to assess the efficacy of therapeutic hypothermia in controlling intracranial hypertension in an adult patient.

Methods:

A systematic review of the literature published between one patient 1990 and 2020 was conducted. Four databases were searched including CINAHL, PubMed, the Cochrane Library, and EMBASE using keywords traumatic brain injury, intracranial pressure, randomized and controlled trials, and the effect of therapeutic hypothermia on intracranial hypertension.

Results:

All of the studies included in this review were randomized controlled trials. Most of the studies provided their sample demographics. Sample sizes ranged from 14 to 501. Of the 12 studies, five of them were from the United Kingdom, three of them were from China, two from North America, one from India, and one from Japan.

Conclusion:

Treating intracranial hypertension with therapeutic hypothermia may be beneficial according to a few studies but it is also associated with many adverse effects. Both the groups suffered from adverse events which were higher in the hypothermic group. However, these adverse events can be managed in any health-care setting. To treat the patients with therapeutic hypothermia, one (the managing team) should be competent enough to manage the adverse effects.

The impact of hypothermia on serum potassium concentration: A systematic review

BACKGROUND

Blood potassium is the main prognostic biomarker used for triage in hypothermic cardiac arrest. The aim of this review was to assess the impact of hypothermia on blood potassium levels and compare the underlying pathophysiological theories.

METHODS

The Medline electronic database was searched via PubMed for articles published from January 1970 to December 2016. The search strategy included studies related to hypothermia and potassium levels. The relevant literature on clinical studies and experimental studies was reviewed by the authors.

RESULTS

Among the 50 studies included in the review, 39 (78%) reported a decrease in blood potassium levels upon hypothermia onset. Hypothermic hypokalaemia is linked to an intracellular shift rather than an actual net loss. The intracellular shift is caused by a variety of factors such as enhanced functioning of Na+K+ATPase, beta-adrenergic stimulation, pH and membrane stabilisation in deep hypothermia. In contrast, hypothermia can act as an aggravating factor in severe trauma with hyperkalaemia being an indicator of an irreversible state of cell death. An increase in the blood potassium level during hypothermia may result from a lack of enzyme functioning at cold temperatures and blocked active transport.

CONCLUSION

Hypothermia causes an initial decrease of potassium levels; however, the final stage of hypothermic cardiac arrest can induce hyperkalaemia due to cell lysis and final depolarisation. Better understanding the physiopathology of potassium levels during accidental hypothermia could be critically important to better select patients who could benefit from aggressive resuscitation therapy such as extracorporeal cardiopulmonary resuscitation.