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29-year old woman with hypokalaemia.

Discussion in 'Case Studies' started by J.P.C. Peper, Jul 13, 2012.

  1. J.P.C. Peper

    J.P.C. Peper Bronze Member

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    A 29-year old woman, who’s been known to have anorexia nervosa for many years, has also suffered from hypokalaemia for some time now. At the beginning, her serum potassium levels fluctuated, but the past three years they’ve been proven low at every blood test. Recently, in a two-monthly interval, she had blood tests again, and the results were as follows:

    - sodium: 146 and 147 mmol/l.
    - potassium: 2,4 and 2,3 mmol/l.
    - chloride: 104 and 102 mmol/l.
    - bicarbonate: 30 and 31 mmol/l.

    Also, her urine samples contained in two consecutive days an average amount of 110 mmol of sodium and 64 mmol of potassium, each day. Her blood pressure has been about 140/100 mm Hg for years and she’s never had ankle swelling. Her weight is 49 kg and she’s 1,75 m in length. She’s always denied the use of diuretics or laxatives. Although the hypokalaemia has been present for a long time now, the cause has never been investigated.

    Questions.

    1. What’s the most likely cause of the hypokalaemia?

    2. Assuming it’s not possible to treat the underlying cause, what’s the best intervention to treat this chronic form of hypokalaemia?
     

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  2. oosandy

    oosandy Well-Known Member

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    base on early hypertension, lean body it must be primary hyperaldosteronism. treat the hypertension and block the aldosteron activity.
     


  3. J.P.C. Peper

    J.P.C. Peper Bronze Member

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    Answers.

    1.

    The amount of potassium in the urine samples is normal, and by that I mean normal for people with a regular diet. Since this potassium excretion takes place when her plasma potassium is low, there has to be a renal problem resulting in loss of potassium. We now have two points that we can use to determine the cause of her hypokalaemia: her history of anorexia nervosa and the hypertension.

    Patients with anorexia nervosa usually present with a slight hypokalaemia, but sometimes the hypokalaemia is more serious because of frequent vomiting. Also, these patients tend to use diuretics when they can. This can in both cases result in alkalosis (which she has, based on the high plasma-bicarbonate).

    So this may be the answer, and it might also explain why doctors never bothered to find the cause of her electrolyte problem. However, there are at least two findings that make this possibility less likely: the hypertension and the sodium and chloride plasma concentrations. In both frequent vomiting and the use of diuretics, there is a (slight) lack of NaCl, resulting in a loss of volume (not fitting the hypertension). In response to this, stimulation of ADH would result in low or very low chloride and sodium plasma concentrations. In this case however, the sodium and chloride levels are both normal.

    Therefore, it’s more likely we’re dealing with an elevated circulating volume with secondary suppression of ADH, which typically fits a primary mineralcorticoid surplus (e.g. due to primary hyperaldosteronism (most commonly Conn’s syndrome) or excessive consumption of liquorices). In this case, the patient turned out to have primary hyperaldosteronism due to adrenal gland hyperplasia.

    2.

    In hyperaldosteronism due to adrenal gland hyperplasia, treating the cause isn’t really an option. There are two possible therapeutic measures: one is to administer potassium, and the other to inhibit the excessive potassium excretion. Supplying her with potassium, however, barely has any effect; even in healthy people, consuming more potassium-rich food has almost no long-term effect on the plasma potassium concentration. This was proven in this patient’s case, as well.

    Inhibiting the potassium excretion therefore makes more sense. This can be done by giving an aldosteron-antagonist. In other renal causes of potassium loss, like Bartter’s syndrome or the use of thiazide diuretics, amiloride or indometacine can be used.

    Literature.

    ’Klinische nefrologie’ (De Jong et al.) (4th edition); a Dutch medical book on nephrology.
     

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