Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.652032
Title: Activation of the hypothalamic-pituitary-adrenal axis during cardiac surgery: the effect of surgical stress and cardio-pulmonary bypass
Author: Gibbison, Ben
ISNI:       0000 0004 5357 9618
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2014
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Abstract:
Glucocorticoids form an essential part of the response to major surgery and critical illness. Both inappropriately low and excessively high levels of glucocorticoid in this context lead to raised morbidity and mortality. Controversy still exists over who these patients are, how they might be diagnosed and when, how and what to treat them with. Simple control of endogenous glucocorticoids is well known and is regulated by a negative feedback system comprising the hypothalamus, the pituitary and the adrenal gland (the HPA axis). It is widely known that cortisol is secreted in a diurnal rhythm; levels are low during periods of sleep and rise to a peak just before waking. Underlying this diurnal rhythm is an ultradian rhythm of discrete pulses. It was previously thought that these pulses were due to a 'pulse generator'. However, recent work has shown that it is inherent within the system and as a result of the feedforward-feedback properties of adreno-corticotrophic hormone (ACTH) and cortisol. Pulsatility is important; transcription of cortisol responsive genes 'pulse' in-time with pulses of cortisol and non-pulsatile cortisol replacement in those with absolute deficiency is associated with an excess mortality. No previous study has examined ultradian rhythms of cortisol at and around the time of major surgery. Coronary artery surgery can be performed with (on-pump) or without (offpump) the use of cardiopulmonary bypass (CPB). Off-pump surgery is associated with lower levels of systemic inflammation as measured by markers, although this does not translate into improved long-term outcomes. Previous work using point measures of cortisol and ACTH after cardiac surgery has shown that both cortisol and ACTH rise by the end of surgery, with cortisol remaining elevated, but ACTH being 'suppressed' by 24 hours post surgery - a so called 'disconnect' between the pituitary and adrenal glands.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.652032  DOI: Not available
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