Major surgery and critical illness produce a potentially life-threatening systemic inflammatory response, which is counterbalanced by changes in adrenocorticotrophic hormone (ACTH) and cortisol. The body’s stress response system, known as the hypothalamic-pituitary-adrenal (HPA) axis, controls the production of these hormones as a vital part of patients’ response to surgery, but researchers have found that there is no simple graded HPA response to cardiac surgery. 

Research by experts at the Universities of Birmingham and Bristol shows cardiac surgery causes major dynamic changes in concentration of ACTH and cortisol, as well as their pattern of secretion. Using novel mathematical techniques, researchers developed a model of HPA axis activity that predicts the physiological mechanisms responsible for different patterns of cortisol secretion. 

They found that the HPA axis response can be classified into one of three dynamic phenotypes: single-pulse, two-pulse and multiple-pulse dynamics. These patterns may reflect underlying physiological differences in each person’s HPA axis, but inflammation caused by surgery also appears to be contributing to changes in at least one of these patterns, the single pulse phenotype, suggesting that patients showing this dynamic could be experiencing the greatest inflammatory response to cardiac surgery. 

Read the full Universdity of Bristol press release

Paper: ‘Modelling the dynamic interaction of systemic inflammation and the hypothalamic-pituitary-adrenal (HPA) axis during and after cardiac surgery,’ by Daniel Galvis, Eder Zavala, Jamie J. Walker, Thomas Upton, Stafford L. Lightman, Gianni D. Angelini, Jon Evans, Chris A. Rogers , Kirsty Phillips and Ben Gibbison in Royal Society Interface.