Relationship Between Epidural Steroid Dose and Suppression of Hypothalamus-Pituitary-Adrenal Axis

Abstract

Background: The suppression of hypothalamic-pituitary-adrenal (HPA) axis is a common complication associated with epidural steroid injections (ESIs). However, the effect of different doses is unknown. Objectives: The primary objective was to compare the differences in the duration of HPA suppression following treatment with different doses of ESI; triamcinolone acetate (TA) 40 mg and TA 20 mg. The secondary objectives were to compare the extent of salivary cortisol (SC) reduction, the incidence of adrenal insufficiency (AI), and the differences in a numeric rating scale (NRS) depending on the varying levels of TA dose used for ESI. Study Design: A double-blind, parallel-group, randomized controlled trial. Setting: Pain clinics in a university hospital. Methods: The patients were treated with TA epidurally and divided into 2 groups (T20 and T40) depending on the dose of TA (20 mg and 40 mg). The SC concentration was measured before and after ESI to calculate the duration of HPA axis suppression, the extent of SC concentration reduction, and the SC recovery rate. Additionally, NRS and adrenocorticotropic hormone stimulation tests were used. Results: Thirty patients were analyzed. The T40 group showed longer HPA suppression (19.7 ± 3.1 days) compared with that of the T20 group (8.0 ± 2.4 days). The recovery rate of the T40 group was lower than that of the T20 group (P < 0.015). However, there was no difference in the extent of reduction in SC concentration after ESI, the occurrence of AI, and pain reduction. Limitations: There were selection bias and no placebo control. Conclusions: Although the difference in pain relief according to the ESI dose is not significant, the HPA suppression is prolonged with a higher dose than a lower dose, and the recovery is slower. Therefore, the time interval between consecutive ESIs should be adjusted depending on the steroid dose to ameliorate the adverse effects of steroids. Key words: Adrenal insufficiency, adverse effects, cushing’s syndrome, epidural injections, glucocorticoids, optimal dosage, pituitary-adrenal system, salivary cortisol