Abstract


Background
The stress response to surgery varies in accordance with the nature and degree of tissue damage. Hypoadrenal patients require additional steroids to replicate the cortisol responses of euadrenal patients. It is necessary to study the cortisol stress response to inform recommendations for steroid replacement in such patients. Previous studies investigating this subject were conducted using older, less-specific assays for cortisol, did not classify the surgery in terms of its severity, or only investigated surgeries of a defined severity/type (1,2,3).

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Background
The stress response to surgery varies in accordance with the nature and degree of tissue damage. Hypoadrenal patients require additional steroids to replicate the cortisol responses of euadrenal patients. It is necessary to study the cortisol stress response to inform recommendations for steroid replacement in such patients. Previous studies investigating this subject were conducted using older, less-specific assays for cortisol, did not classify the surgery in terms of its severity, or only investigated surgeries of a defined severity/type (1,2,3).

Question
What is the cortisol response of euadrenal patients to surgery of varied severity, as assessed by modern assays?

Methods
Patients undergoing elective surgery at ICHNT were enrolled prospectively in an observational study (median age 56.1, 46 male, 47 female). The subtypes of surgery were as follows: upper gastrointestinal 11%, hepatopancreatobiliary 37%, general 6%, head and neck 40%, cardiothoracic 6%. Serum samples were taken at: 8am on the day of surgery; at anaesthetic induction; 1hr; 2hr; 4hr; 8hr thereafter, and; daily at 8am until post-operative day 5 or hospital discharge. The samples were assayed for cortisol (Abbott Architect immunoassay), cortisol binding globulin (CBG – Biosource immunoassay). Free cortisol index (FCI) was calculated as the ratio of cortisol to CBG. Surgical severity was classified in accordance with POSSUM scoring.

Results
Ninety-three patients were classified according to operative severity: Major/Major+ (n=37), Moderate (n=33), and Minor (n=23). Peak cortisol positively correlated to surgical severity: Major/Major+ median 680 (range 375–1452), Moderate 581 (270–1009), and Minor 574 (262–1066) nmol/L (Kruskal-Wallis test, P=0.0031). CBG fell acutely during surgery (mean reduction 21-23%), leading to an increased FCI (mean increase 61-76%); the magnitudes of these effects positively correlated to surgical severity.

Conclusions
Our study is the first to study the cortisol stress to surgery and its relationship to surgical severity. An observed reduction in peak cortisol compared to previous studies is likely due to improvements in surgical and anaesthetic technique and cortisol assays. Our data support a reduction in recommended steroid doses for hypoadrenal patients and a graded approach according to surgical severity, so as to minimise the deleterious effects of over-replacement.

Disclosures
No relevant disclosures: all authors

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