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Problem solving in clinical practice: the sick infant with low sodium and high potassium
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  • Published on:
    Authors response to e-Letter: "Be careful how quickly you correct hyponatraemia"
    • Yincent Tse, Consultant Paediatric Nephrologist Great North Children's Hospital, Newcastle Upon Tyne
    • Other Contributors:
      • Timothy Cheetham, Consultant Paediatric Endocrinologist

    Thank you for highlighting the recommendation for avoiding too rapid correction of hyponatraemia and the need for close monitoring of urinary electrolytes. The focus of the article (problem solving in clinical practice) was the differential diagnosis rather than the nuances of management but we agree that regular assessment of urinary electrolytes will help to guide fluid management in the sick hyponatraemic baby. The importance of focusing on urine content as well as blood electrolytes has been an important component of clinical practice in our unit for many years (1).

    In our experience infants recover very quickly after the initial resuscitation and can frequently be fed enterally within a matter of hours. Osmotic demyelination syndrome is very uncommon in paediatric practice (an interesting story in itself) and one wonders whether there are more subtle differences in outcome that can be linked to initial management. The reality (we suspect) is that many hyponatraemic babies are managed without close, detailed regular scrutiny of urinary electrolytes and perhaps this is a topic for further study.

    Dr Smith and Maderazo rightly states that ‘Healthy kidneys can cut urinary sodium losses to almost zero’ however please note that babies with adrenal disorders such as 21-hydroxylase deficiency often require relatively high doses of mineralocorticoid as well as sodium supplements for several months.

    1. Coulthard MG. Will changing maintenance intravenous f...

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    Conflict of Interest:
    None declared.
  • Published on:
    Be careful how quickly you correct hyponatraemia
    • Graham C Smith, Consultant Paediatric Nephrologist University Hospital of Wales
    • Other Contributors:
      • Susanna Maderazo, Senior Clinical Fellow in Paediatrics

    Dear Sir,

    We read with interest the problem solving article by Tse et al. looking at the management of infants presenting with hyponatraemia plus hyperkalaemia1. They recommend the administration of intravenous 0.9% NaCl to correct hyponatraemia until oral feeds can be given. We are concerned that this protocol will produce a rise in serum [Na+] faster than recommended. The guidance is that once any acute symptoms have been addressed the rise in serum [Na+] should not exceed 8 mmol/L/day in order to minimise the risk of developing Osmotic Demyelination Syndrome (ODS). Certainly the rise should be less than 10-12 mmol/L in any 24-hour period or 18 mmol/L in any 48-hour period2.

    No specific comment is made about the speed of correction of the serum sodium concentration in case 1 other than that there was "gradual resolution of both the hyponatraemia and hypokalaemia". However in case 2 the serum sodium concentration is said to have normalised within 48 hours. The starting sodium concentration was 108 mmol/L and the normal quoted as 133-146 mmol/L so the minimum rate of rise was 12.5 mmol/L/day, exceeding the recommended rate of rise.

    As illustrated by the two cases, these patients usually present with extracellular fluid (ECF) contraction and require replacement of the ECF volume deficit. This should be with a fluid that matches the electrolyte composition of the ECF but we tend to only cater for a normal ECF [Na+] and use 0.9% NaCl. However i...

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    Conflict of Interest:
    None declared.