Journal Mobile

CJ Thompson, RK Crowley
Journal Issue: 
Volume 39: Issue 2: 2009




Hyponatraemia is the most common electrolyte abnormality in hospital inpatients,  and  is  associated  with  complications  such  as  seizures,  increased mortality and prolonged hospitalisation. The risk of symptoms, complications and death  increases  with  severity  of  hyponatraemia. A  wide  variety  of  illnesses  and therapies can cause hyponatraemia, and the treatment of the underlying condition is  always  important.  There  are  three  main  pathophysiological  causes  of  hyponatraemia. Hypovolaemic hyponatraemia is characterised by clinical and biochemical evidence  of  dehydration  and  is  best  treated  by  intravenous  sodium  chloride solution. Hypervolaemic hyponatraemia presents with fluid overload, which usually requires  diuretic  therapy.  Euvolaemic  hyponatraemia,  of  which  the  syndrome  of inappropriate antidiuretic hormone secretion is an example, is traditionally treated with fluid restriction, although the new vasopressin antagonists, the vaptans, show great  potential  for  future  therapy.  An  accurate  diagnosis  of  the  cause  of hyponatraemia  is  necessary  for  appropriate  treatment.  Severe  hyponatraemia  is potentially  life-threatening  and,  if  cerebral  irritation  is  present,  intensive  therapy with  saline  infusion  may  be  necessary;  because  of  the  risk  of  central  pontine myelinolysis,  this  should  always  be  given  under  specialised,  highly  experienced direction.  Plasma  sodium  should  be  checked  every  two  hours,  and  the  rate  of elevation of plasma sodium concentration should not exceed 0.5 mmol/l/h.