Steroids Flashcards
WhatDescribe the carbon skeleton of a steroid
4 carbon rings
6-6-6-5 carbon skeleton
What three major classes of steroids are secreted by the adrenal cortex
Glucocorticoids
Mineralocorticoids
Androgens
Name a few areas in physiology where steroids play an important role?
Metabolism
- CHO
- Lipid
- Protein
- Nucleic acid
Modulation of the stress response
Regulation of immune response/inflammation
Electrolyte physiology
Behaviour
Describe the axis for cortisol production
Hypothalamus: CRH (corticotrophin releasing H)
Anterior pituitary: ACTH (Adrenocorticotrophic H)
Zona fasciculata of adrenal cortex: Cortisol
Cortisol then inhibits release of CRH and ACTH (negative feedback)
How much cortisol is normally produced by the body per day and by how much does this increase under stress (surgery/trauma/infection).
30 - 40 mg of cortisol per day
Can increase x 4 during surgery or in the post operative period if RA/GA used.
Maximal surgical stress: cortisol secretion increases to 100 - 200 mg persisting for up to 72 hours
What is an Addisonian crisis and how does this allow us to understand the role of steroids
FATAL MEDICAL EMERGENCY
Addisonian crisis = adrenal crisis = Acute severe adrenal insufficiency due to:
1. Haemorrhage in the adrenal gland
2. New stressful event in a patient with Addison’s disease or relative adrenal insufficiency
Characterised by:
- Severe low BP (low SVR and reduced LVSV in the presence of normal filling pressures)
- Hypoglycaemia
- Vomiting and diarrhoea
- Lethargy and convulsions
What are the indications for chronic steroid therapy
- Anti-inflammatory/Immunosupressive effects
- Primary or secondary adrenal insufficiency due to adrenal gland/pituitary/hypothalamic pathology
- Adrenalectomy patients
Can topical steroids supress the Hypothalmic-pituitary-adrenal access
Yes - inquire about topical preparations
How long can adrenal suppression persist after stopping steroids
months
When should supplemental cortisol to cover the stress response be given perioperatively
If the patient has been on > 10 mg prednisolone daily within the last 3 months
How can the pituitary-adrenal axis be tested
None of the available tests to determine return of normal adrenal responsiveness satisfy all the desirable criteria of safety, reliability, practicality and ease of administration.
- Morning cortisol (unreliable)
- Induce hypoglycaemia with insulin (dangerous)
- Acute stress cortisol level > 25 ug/dL = normal axis
- Synthacten test: ACTH 250ug –> double baseline cortisol = adequate axis
Tests are impractical and inaccurate so give steroids if steroids if > 10 mg of pred has been given within 3 months
What is the risk with abrupt stoppage of steroid therapy
can precipitate adrenal crisis
What is the dosing regimen for steroid supplementation
Hydrocortisone
- Minor Sx: Induction: 25 mg
- Moderate Sx: 25 mg + 25 mg qds IV x 4 doses
- Major Sx: 25mg + 25 mg qds IV x 12 doses
Compare the potency and half life of: prednisolone, methylprednisolone, hydrocortisone and dexamethasone
DRUG - Relative POTENCY - T1/2 (hours)
Hydrocortisone - 1 - 8 (1 mineralocorticoid)
Dexamethasone - 25 - 45 (0 mineralocorticoid)
Prednisolone - 4 - 24 (0.8 mineralocorticoid)
Methypred - 5 - 30 (0.5 mineralocorticoid)
E.g. dose equivalents:
Hydrocortisone: 100mg
Dexamethasone: 4mg
Prednisolone: 25mg
Methylpred: 20 mg
Potential risks associated with short term steroid supplementation are:
Hyperglycaemia Fluid retention Stress ulcers in gastrointestinal tract Psychiatric disturbance Aggravation of hypertension Delayed wound healing Infection
However, there is no definitive evidence to prove that short term steroid supplementation contributes to these effects.
