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

date 04/01/2007

serum sodium 125

serum osmolality 255

urine sodium 32

urine osmolality 677

Diagnosis?

• Too much water?

• Too little salt?

Too much water?Too little salt?

Una highUosm < Posm

UNa Low Uosm > Posm

Clinical euvolemic or edematousIncreased body weight

Too much water

Water overload

UNa HighUosm = Posm

UNa High Uosm > Posm

Heart failureNephrosisCirrhosisEnteropathyLow albumin

DiureticsIntrinsic renal diseasePKD

SIADH

NaSerum

Further course

date 9.1.07 13.1. 16.1. 21.1weight 4.44 4.87 4.9 4.86BP 90 120 120 145in 462 836 917 707out 395 593 700 486serum sodium 126 133 135 139serum osmolality 256 257 275 284urine sodium 152 158 268 313urine osmolality 657 569 610 744sodium in (mmol/kg) 10 15 19 14

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

biochemistries plasma urine unit

Sodium 121 45 mmol/l

osmolality 249 252 mOsmol/kg

Creatinine 0.017 <1.0 mmol/l

Diagnosis?

• Too much water?

• Too little salt?

Too much water?Too little salt?

Una highUosm < Posm

UNa Low Uosm > Posm

Clinical euvolemic or edematousIncreased body weight

Too much water

Water overload

UNa HighUosm = Posm

UNa High Uosm > Posm

Heart failureNephrosisCirrhosisEnteropathyLow albumin

DiureticsIntrinsic renal diseasePKD

SIADH

NaSerum

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 (75th %ile)

biochemistries plasma urine unit

Sodium 99 <5 mmol/l

osmolality 214 450 mOsmol/kg

Creatinine 0.021 1.0 mmol/l

Albumin 8 8.6 g/l

Diagnosis?

• Too much water?

• Too little salt?

Too much water?Too little salt?

Una highUosm < Posm

UNa Low Uosm > Posm

Clinical euvolemic or edematousIncreased body weight

Too much water

Water overload

UNa HighUosm = Posm

UNa High Uosm > Posm

Heart failureNephrosisCirrhosisEnteropathyLow albumin

DiureticsIntrinsic renal diseasePKD

SIADH

NaSerum

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