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Awetahagn Abreha CHAPTER 40 ANAESTHESIA AND ADRENAL INSUFFICIENCY Outline: General structure Adrenal cortex Guidelines for the use of steroid replacement therapy Adrenal medulla 1

Ch 40 Anaesthesia and Adrenal Insufficiency

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Page 1: Ch 40 Anaesthesia and Adrenal Insufficiency

AwetahagnAbreha

CHAPTER 40

ANAESTHESIA AND ADRENAL INSUFFICIENCY

Outline:

General structure

Adrenal cortex

Guidelines for the use of steroid replacement therapy

Adrenal medulla

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Page 2: Ch 40 Anaesthesia and Adrenal Insufficiency

AwetahagnAbreha

GENERAL STRUCTURE

The adrenal gland has two separate parts: the cortex (70%) and the medulla (30%). Each develops from a different type of embryological tissue and has its own distinct functions.

ADRENAL CORTEX

The adrenal cortex produces three types of hormones.

Glucocorticoids which have an effect on carbohydrates, fat and protein metabolism. They also have an anti-inflammatory action. Cortisol is the principal glucocorticoid and is essential for many physiological processes. It must be replaced if deficient. Hydrocortisone hemisuccinate, dexamethasone and prednisolone are examples of drugs used for steroid replacement therapy.

Mineralocorticoids which control sodium retention and potassium excretion. They are secreted in response to a reduction in plasma sodium concentration due to low intake or following surgery, trauma and haemorrhage. Aldosterone is the principal mineralocorticoid.

Sex hormones which are secreted by the adrenal cortex. Abnormalities of androgen secretion are usually genetic and interfere with normal growth and sexual characteristics in childhood. Corticosteroid therapy (synthetic glucocorticoids and mineralocorticoids)Steroids are used in the treatment of many disease states (e.g. asthma, ulcerative colitis). They are used for their anti-allergic and anti-inflammatory action. The output of the adrenal gland is controlled by the pituitary gland, which secretes the hormone ACTH (adrenocorticotrophic hormone). This is secreted in response to the circulating steroids. If the steroid level in the blood is low, then more ACTH is secreted and the

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Page 3: Ch 40 Anaesthesia and Adrenal Insufficiency

AwetahagnAbrehaadrenal gland is stimulated to put out more steroids. If the steroid level is high (for instance, if the patient is on steroid therapy) the output of ACTH falls and the adrenal gland can atrophy. In a stressful state (e.g. anaesthesia or surgery) this gland cannot increase its output of steroid as demanded, so the blood pressure falls and the patient may collapse. Adrenal reserve is diminished in Addison's disease, after bilateral adrenalectomy and during current or previous steroid therapy.

GUIDELINES FOR THE USE OF STEROID THERAPY PERI–OPERATIVELY

Check carefully whether patient has a history of steroid therapy. Some diseases are associated with the use of steroids (e.g. rheumatoid arthritis or asthma).

Patients who have had steroid therapy for longer than 2 weeks in the 3 months before major surgery or are currently taking steroids, should be given steroid cover peri-operatively. Hydrocortisone 25mg 1V is given at induction in the adult patient.

Patients having minor surgery should not require any further supplement and should then continue with their regular preoperative dose.

Patients having intermediate surgery. A total of 125mg hydrocortisone should be given on the first day of surgery. If the patient is not currently taking steroids this should be sufficient to cover previous use. Those who are currently taking steroids should then recommence their usual dose.

Patients having major surgery involving no oral intake post-operatively. Patients currently taking steroid therapy should be continued on hydrocortisone 100mg / day (25mg 6hrly IV). When oral intake recommences they should be restarted on their previous dose of prednisolone.

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Page 4: Ch 40 Anaesthesia and Adrenal Insufficiency

AwetahagnAbreha

ADRENAL MEDULLA

The adrenal medulla is responsible for the synthesis and excretion of catecholamines. (See Chapter 5 The Autonomic nervous system).

The output from the medulla is mainly adrenaline (80-90%) with noradrenaline (10-20%). It also produces dopamine. The medulla acts as a sympathetic ganglion and has no parasympathetic innervation.

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