Cortisol response to general anaesthesia for medical imaging in children.

OBJECTIVE: The cortisol response to surgical stress has been frequently studied, and recommendations developed for steroid replacement in adrenally insufficient patients. There are currently no guidelines, however, for adrenal hormone replacement during anaesthesia alone. The objective of this study was to characterize the normal cortisol response to general anaesthesia in the absence of a surgical procedure in children.
DESIGN: Prospective observational study. PATIENTS: Thirty-seven children (aged 0.5-7 years) without known endocrine disease or cranial neoplasms undergoing outpatient magnetic resonance imaging, under general anaesthesia for investigation of nonacute problems in a tertiary referral paediatric hospital. MEASUREMENTS: Serum cortisol and salivary cortisol were measured before and after anaesthesia and during recovery.
RESULTS: The mean cortisol level was 303 (± 117) nmol/l at induction, 396 (± 241) nmol/l at emergence from anaesthesia and 584 (± 218) nmol/l during recovery. A stress response (increase in serum cortisol >550 nmol/l) occurred in 23% of children at emergence and in 52% of children at recovery. Eight children (31%) actually demonstrated a decrease in cortisol levels during anaesthesia, without an increase in complications. Mean salivary cortisol levels were 6.5 ± 4.8 nmol/l before induction, 23.5 ± 13.8 nmol/l at emergence from anaesthesia and 26.9 ± 21.6 nmol/l during recovery. A stress response (an increase in salivary cortisol greater than seven-fold) occurred in 26% of children during the study.
CONCLUSIONS: While some children demonstrated a rise in their cortisol levels in response to anaesthesia without surgery, the response was variable and often more pronounced during recovery. There was consistently no classic stress response.