The Effects of Whole Body Cooling Following Traumatic Brain Injury

Abstract

Introduction: Prevention of secondary brain injury is key in the management of severe traumatic brain injury in intensive care. A raised temperature post traumatic brain injury is considered by many to be a potential insult, although the evidence from animal and human studies is ambiguous. Due to lack of evidence for induced hypothermia, the aim of current clinical temperature management following severe traumatic brain injury is often the 'middle ground' or maintained normothermia. In our intensive care unit a step wise cooling protocol is initiated in the event of a rise in temperature. Preliminary work from our unit suggested that reduction of measured temperature during cooling is variable, and may be associated with changes in physiological parameters. In order to investigate this further, we carried out a detailed observational study to observe the effects of whole body cooling on brain temperature and on certain physiological and biochemical parameters. The aim was to observe for any effects of cooling that could contribute to secondary injury. In addition, we undertook a patient review to examine for possible relationships between raised temperature, the length of time temperature was raised, and clinical outcome, in a larger set of patients. These two studies, the patient review and observational study, constitute the work performed for this thesis. Methods: Patient Review - All patients admitted following a severe traumatic brain injury over a 12 month period were eligible for inclusion in the study. The case notes of each patient were reviewed and assessed at three time points. At admission the initial temperature reading was noted. At the other two time points patients were only included if they remained on ICU. Peak temperature and the length of time temperature was raised were noted. Analysis was performed using logistic regression to look for a relationship with outcome.Observational study - This more detailed study took place over the same time period and involved a small cohort of patients with brain temperature monitoring who did not require immediate surgical intervention. A maximum of two cooling episodes were studied in each recruited patient. Changes in brain temperature, ICP, CPP, S100b, IL-6 and TNF-alpha were monitored during the recruitment period and more frequently during studied cooling episodes. In addition BIS monitoring was performed during studied cooling episodes.Results: Patient review - There was no evidence in our population of patients that a raised temperature or the length of time a temperature was raised was associated with an increased risk of death. Observational study - All methods of temperature reduction were observed to be poorly effective at reducing brain temperature. There were observed changes in the monitored physiological and biochemical parameters that may have been directly related to the cooling process and may be clinically significant.Discussion - Further laboratory and clinical studies are required to unlock the enigma of brain temperature management following severe traumatic brain injury. Further studies into the use of surface cooling and gastric lavage should be undertaken to fully assess their potential risks and benefits. In the United Kingdom and Ireland there is a need for a consensual approach to temperature management.

Date of Award	1 Aug 2011
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Charmaine Childs (Supervisor) & Philippa Tyrrell (Supervisor)