Practice Cases in primary care laboratory medicine

Monitoring renal function in hypertension

BMJ 2006; 333 doi: (Published 26 October 2006) Cite this as: BMJ 2006;333:896
  1. Una Martin, senior lecturer in clinical pharmacology (,
  2. Jamie J Coleman, specialist registrar in clinical pharmacology1
  1. 1 Department of Clinical Pharmacology, Division of Medical Sciences, University of Birmingham, Birmingham B15 2TH
  1. Correspondence to: U Martin
  • Accepted 18 September 2006

Several classes of antihypertensive drugs can cause a fall in glomerular filtration rate and a rise in serum potassium and creatinine concentrations. Appropriate monitoring during treatment of hypertension allows potentially serious underlying conditions to be identified and adverse events avoided.

We present two typical cases seen in a hospital hypertension clinic that illustrate the role of measurement of electrolytes and renal function in patients treated with angiotensin inhibitors (angiotensin converting enzyme (ACE) inhibitors and angiotensin II receptor antagonists) or potassium sparing diuretics. Both cases highlight the need to identify patients at increased risk of developing difficulties when taking such antihypertensive drugs and the need to target increased monitoring in at-risk patients.

Case 1

A 64 year old woman was referred to a hypertension clinic with a blood pressure of 180/110 mm Hg. Her biochemical profile was normal (serum creatinine concentration 102 µmol/l, urea 6.4 mmol/l, potassium 4.2 mmol/l, sodium 139 mmol/l). Treatment started with amlodipine 5 mg, and when she was reviewed, six weeks later, her blood pressure was 165/95 mm Hg. Perindopril 4 mg was added, and one week later her blood pressure was 144/70 mm Hg. However, her renal function showed some deterioration, with slight rises in serum creatinine concentration (110 µmol/l) and urea concentration (9.3 mmol/l). A month later the patient's blood pressure control remained good (140/70 mm Hg), but there was further deterioration in renal function (creatinine of 143 µmol/l, urea 10.4 mmol/l). A further month later, she was normotensive (139/71 mm Hg) with no further change in renal function (creatinine 143 µmol/l, urea 11 mmol/l).

In view of the deterioration in her renal function, she was investigated with a renal ultrasound scan followed by enhanced renal magnetic resonance angiogram. A short tight stenosis of the left renal artery was diagnosed. A nuclear medicine renal scan showed that …

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