Low salt BM 2019 MMC

125-135 Nausea Malaise < 120 Headache Lethargy Obtundation Siezure Coma Chronic  less severe Chronic adaptation important  CSF , K loss and then organic solutes  24 hours

CSF Nausea Malaise Headache Lethargy Seizures Coma Respiratory depression The adaptive process takes 24 hours The correct of organic solute concentration is much slower and rapid correct  osmotic demyelination especially in premenopausal women and children Cell water K+ Organic solutes (1/3) CSF

5.2 vs 1.3% @ 30 days 1.8% vs 0.7% 7.4% vs 4.6% 3.7% vs 1.5% 75000 hyponatreamia 800000 normal 5.2 vs 1.3% @ 30 days 1.8% vs 0.7% 7.4% vs 4.6% 3.7% vs 1.5%

8 – 10 mmol/L in 24 hours 18 in 48 hours

Primary Polydipsia overwhelms kidney

Serum osmolarity and sodium concentration in plasma water is normal The sodium concentration per litre of plasma is reduced Asymptomatic = tonicity is maintained Tonicity maintained = sodium per Liter of plasma is reduced (but normal per liter of plasma water)

Glucose increases serum osmolarity and is an effective osmole ( i Glucose increases serum osmolarity and is an effective osmole ( i.e it doesn’t freely enter cells) Water moves into plasma and dilutes sodium Neurologic symptoms not from low sodium For ethanol / urea  ineffective but some contribution Patients with hyponatreamia in these patients as likely to develop symptoms

Severe hypertonic hyponatreamia due to dilution

Symptom Severity Acute or Chronic Mild Moderate Severe < 120 mEq/L 24 - 48 hours Symptom Severity Seizures Obtunded Coma Respiratory Arrest

Hypotonic hyponatremia Hypovolemia Oedematous Low urine Na < 25 Low urine Na > 40 GIT loss ‘Third space’ Diuretics Urine Chloride >25 Diuretics Primary adrenal insufficiency ‘Cerebral salt wasting’ Urine chloride < 25 Vomiting Associated M. Alk Heart failure Cirrhosis End stage renal disease

Euvolemic Hypotonic hyponatremia High urine sodium > 40 High urine osmolality > 100 Low urine sodium < 25 Low urine osmolality < 100 SIADH Primary polydipsia Beer potomania Rapid correct of hypovolemia with saline Reversal of SIADH after stopping drug GC replacement in adrenal insufficiency Surreptitious diuretic use Severe hypothyroidism Cortisol deficiency

Chlorpropamide Carbamazepine Oxcarbazepine IV cyclophosphamide SSRI Vincritine Haloperidol Valproate NSAIDS Alpha interferon Amiodarone MTX opiates CNS Stroke Bleed Tumour Infection Trauma Psychosis Malignancy Lung Small cell

< 105 Hypokalemia Alcoholism Malnutrition Liver disease Premenopausal women Young children

6/6 8/24 ABC Stop offending drugs Reverse the cause Treat hypovolemia with saline or 3% saline if severe Treat seizures with benzo 8/24 8-10 mEq/L in 24 hours Acute Severe: 4-6 mEq/L will reverse most severe symptoms in 6 hours 50-100ml aliquots of 3% Saline over 10 minutes Max 300mls 6/6