November 18, 2017
Frusemide Test for Hyperaldosteronism Minimize

Frusemide test for hyperaldosteronism

Indication

This test may be used as a screening test for hyperaldosteronism in hypertensive patients since hypokalaemia is an irregular finding.

Contraindication

The only risks are the potential effects of cessation of anti-hypertensive therapy.

Principle

Aldosterone is normally regulated by the renin-angiotensin system which is in turn regulated by renal blood flow. If subjects are rendered hypovolaemic/hypotensive, the renin-angiotensin system should be stimulated. This does not occur in states of inappropriate aldosterone secretion.

Side effects

none

Preparation

Ideally patients should stop taking diuretics, NSAIDs and anti-hypertensive agents (ACE inhibitors, betablockers and calcium channel blockers) 2 weeks prior to this investigation, and oestradiol and spironolactone for 6 weeks prior. There are variable opinions on the absolute need for cessation of drug therapy but our experience is that spironolactone can be quite misleading with elevations in PRA even in patients with proven aldosterone producing adenomata.

Requirements

  1. Frusemide 40 mg tabs x 2
  2. Li heparin blood tubes x 2

Procedure

day 1

0900-1100 h

patient should remain upright and ambulant
at 1100 h take blood for plasma renin activity

day 2

1800 h

give Frusemide 40 mg tab

Day 3

0900 h

give Frusemide 40 mg tab

 

0900-1100 h

patient should remain upright and ambulant
at 1100 h take blood for plasma renin activity

Interpretation

Failure of PRA to rise above 1.5 nmol/L/hr indicates primary hyperaldosteronism.

Sensitivity and Specificity

This test separates all forms of mineralocorticoid excess from other forms of hypertension but does not indicate the cause ie bilateral adrenal hyperplasia, adrenal adenoma, idiopathic hyperaldosteronism, apparent mineralocorticoid excess, DOC producing adenoma, etc.

References

  • Valloton MB. Primary aldosteronism. Part I Diagnosis of primary hyperaldosteronism. Clin Endocrinol 1996;45:47-52.
  • Weinberger MH, Grim CE, Hollified JW, Kem DC, Ganguly A, Kramer NJ, Yune HY, Wellman H, Donohue JP. Primary aldosteronism. Diagnosis, localization and treatment. Ann Intern Med 1979;90:386-395
  

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