Diagnosis

Diagnosis is confirmed by plasma cortisol, ACTH levels and a negative Tetracosactrin (ACTH analogue) test, although treatment should begin on clinical suspicion. A dose of 250pg IV should produce a >200 nmol/l rise in plasma cortisol. In primary hypoadrenalism levels remain below 600 nmol/l. However, basline levels may be normal or elevated in the relative adrenal deficiency seen in sepsis and other critical illnesses. Dexamethasone may be used for steroid replacement for 48 h before an ACTH test is performed since other steroid treatments are detected in the plasma cortisol assay.

, abdominal pain, hypoglycaemia) , weight loss, postural hypotension,

Management

• Salt and water deficiency should be corrected urgently. Initial fluid replacement should be with colloid if there is hypotension, or evidence of poor tissue perfusion. Otherwise 4-5l/day 0.9% saline will be needed for several days.

• Fluid management should be carefully monitored to ensure adequate replacement without fluid overload.

• Glucocorticoid replacement should be with hydrocortisone 50-100 mg tds IV on day 1 then 20-50 mg tds on days 2-3. Hydrocortisone may be changed to equivalent doses of dexamethasone before the ACTH test has been performed.

• The relative hypoadrenalism related to sepsis can be treated with hydrocortisone 50 mg qds for 7 days, and then a reducing dose over the next 5-7 days. Studies have shown more rapid resolution of shock and an improved outcome in those showing a suboptimal response to synthetic ACTH, despite raised baseline levels.

Blood presure monitoring, p110; Central venous catheter—use, p114; Electrolytes

, p146; Calcium, magnesium and phosphate, p148; Crystalloids, p176; Colloids, p180; Steroids, p262; Fluid challenge, p274; Hypotension, p312; Diarrhoea, p340; Hyponatraemia, p418; Hypercalcaemia, p426; Hypoglycaemia, p438

P.449

£ Ovid: Oxford Handbook of Critical Care

Editors: Singer, Mervyn; Webb, Andrew R.

Title: Oxford Handbook of Critical Care, 2nd Edition

Copyright ©1997,2005 M. Singer and A. R. Webb, 1997, 2005. Published in the United States by Oxford University Press Inc

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