Severe hyponatraemia Detlef Bockenhauer

Objectives To provide an overview of hyponatraemia by giving case scenarios Aetiology Assessment management

Why is the sodium low? Too little salt –Weight should be decreased –Signs of dehydration/volume depletion Too much water –Weight should be stable or increased –Oedema forming states

Too much water Identify defect in water excretion –Low GFR--neonates, renal insufficiency –Enhanced proximal reabsorption-- CHF, Low albumin [Cirrhosis, Nephrosis, Enteropathy ] –Defect in ascending limb function-- diuretics, intrinsic lesions –Inability to turn off ADH-- SIADH

Too little salt Identify source of salt loss –Gi: diarrhea/vomiting –Skin: sweat, CF –CSF: drainage –Tears: –Kidney: salt losing nephropathy/adrenal insufficiency

case 1 6-months old boy with astrocytoma Receives vincristine and carboplatin 10 days later presents for routine follow-up Examination: well perfused, wt: 4.7 kg (+0.2 kg), BP: 82 mmHg date04/01/2007 serum sodium125 serum osmolality255 urine sodium32 urine osmolality677

Diagnosis? Too much water? Too little salt? Too much water?Too little salt?

U na high U osm < P osm U Na Low U osm > P osm Clinical euvolemic or edematous Increased body weight Too much water Water overload U Na High U osm = P osm U Na High U osm > P osm Heart failure Nephrosis Cirrhosis Enteropathy Low albumin Diuretics Intrinsic renal disease PKD SIADH Na Serum

Further course date weight BP in out serum sodium serum osmolality urine sodium urine osmolality sodium in (mmol/kg)

Key message Sodium is reabsorbed to preserve intravascular volume and in response to renal perfusion Kidney does not sense or detect serum sodium

Treatment Fluid restriction vaptans

Hyponatraemia-case 2 11-months old girl referred for assessment of hyponatraemia, first noted incidentally during investigations for viral illness and confirmed several times subsequently Examination: well perfused, BP: 90 mmHg biochemistriesplasmaurineunit Sodium12145 mmol/l osmolality mOsmol/kg Creatinine0.017<1.0 mmol/l

Diagnosis? Too much water? Too little salt? Too much water?Too little salt?

U na high U osm < P osm U Na Low U osm > P osm Clinical euvolemic or edematous Increased body weight Too much water Water overload U Na High U osm = P osm U Na High U osm > P osm Heart failure Nephrosis Cirrhosis Enteropathy Low albumin Diuretics Intrinsic renal disease PKD SIADH Na Serum

Family History Mother and maternal grandmother were known to have had hyponatraemia. Maternal uncle has developmental delay and recurrent hyponatraemia (often with seizures) Mum and grandmother “don’t drink”

Diagnosis? Nephrogenic Syndrome of inappropriate antidiuresis X-linked inherited Gain-of-function in AVPR2: R137C/L Females usually less affected

AJKD, 2012 Apr;59(4):566-8

Treatment Intuitiv by patients! ?Increased osmotic load during infancy (urea)

Case 3 14-week old girl, presents with 5-week history of vomiting and unusual weight gain (1.1 kg over past 2 weeks) Examination: generalised pitting oedema, BP: 120 mmHg, weight 6 kg (75 th %ile) biochemistriesplasmaurineunit Sodium99<5 mmol/l osmolality mOsmol/kg Creatinine mmol/l Albumin88.6 g/l

Diagnosis? Too much water? Too little salt? Too much water?Too little salt?

U na high U osm < P osm U Na Low U osm > P osm Clinical euvolemic or edematous Increased body weight Too much water Water overload U Na High U osm = P osm U Na High U osm > P osm Heart failure Nephrosis Cirrhosis Enteropathy Low albumin Diuretics Intrinsic renal disease PKD SIADH Na Serum

Treatment Underlying condition Diuretics NOT salt

Case 4 11 y old boy with CKD 5 due to cortical necrosis comes for live-related transplant Develops massive diuresis post transplant, up to 60 ml/kg/h As per protocol, losses are replaced with ½ NS ml/ml 4-h post transplant, he develops a generalised seizure

Ped Neph 2009 Jun;24(6):1231-4

treatment Depends on chronicity The lower the sodium the more likely this is longstanding Aimed at underlying problem Acute symptomatic cases: 2 ml/kg (max 100 ml) of 3% NaCl (repeat if needed)

Conclusions Disorders of water are reflected in plasma sodium SIADH and cerebral salt wasting are biochemically indistinguishable Kidneys do not sense sodium concentration, just perfusion A Uosm=Posm in the face of hyponatraemia and water overload is inappropriate Treatment aimed at underlying defect and depends on chronicity