“A patient with known adrenal insufficiency secondary to hypopituitarism who is undergoing a period of stress such as illness or surgery should be given intravenous corticosteroids.
For moderate-risk procedures such as vascular or orthopedic operations, 50 mg of hydrocortisone is recommended.
For major surgery, such as open heart surgery or an esophagectomy, 100 mg of hydrocortisone would be needed.
These doses can be repeated every 8 hours until the patient is stable and is able to take his usual oral maintenance dose.” ABFM
Reference
Arch Surg 2008;143(12):1222-1226. https://www.ncbi.nlm.nih.gov/pubmed/19075176
Med Clin North Am. 2009 Sep;93(5):1031-47. https://www.ncbi.nlm.nih.gov/pubmed/19665618