Cerebral salt wasting and siadh

by prof dr samie alanasary prof of icu ain shams university

1. SIADH DI Cerebral Salt Wasting SAMIR EL ANSARY ICU PROFESSOR AIN SHAMS CAIRO

2. SIADH Syndrome of Inappropriate ADH Secretion Definition: levels of ADH are inappropriately elevated compared to body’s low osmolality , and ADH levels are not suppressed by further decreases in blood osmolality .

3. SIADH Causes Irritation of CNS meningitis , encephalitis, brain tumors, brain hemorrhage, hypoxic insult, trauma, brain abscess, Guillain Barre , hydrocephalus Pulmonary disorders pneumonia, asthma, positive end expiratory pressure ventilation, CF, TB, pneumothorax

4. SIADH causes Drugs: vincristine , vinblastine , opiates, carbamazepime , cyclophosphamide Unregulated tumor production of ADH-like peptides: oat cell lung carcinoma for example, Ewings sarcoma, carcinoma of duodenum, pancreas, thymus

5. SIADH function of ADH Antidiuretic hormone = vasopressin ADH is made in the supra-optic nuclei in the hypothalamus , stored in the posterior pituitary Normally released into the bloodstream when osmo -receptors detect high plasma osmolality

6. SIADH function of ADH At the kidney, attaches to receptors in the collecting ducts , opens up water channels Water is passively reabsorbed along the kidney’s medullary concentration gradient

7. SIADH signs and symptoms Decreased / low urine output Signs of hyponatremia : lethargy, apathy, disorientation, muscle cramps, anorexia, agitation Signs of water toxicity: nausea, vomiting, personality changes, confused, combative If Na < 110 mEq /L , seizures, bulbar palsies, hypothermia, stupor, coma

8. SIADH lab values Serum Na < 135 (Na is diluted by excessive free water re-absorption) Serum osmolality low, normal is ~ 270 Urine Na is inappropriately high, >20 mmol /L, actually losing Na in urine instead of retaining it

9. SIADH lab values Urine osmolality is inappropriately high, can range b/t 300-1400 mosm /L CVP is high from free water retention

10. SIADH Treatment Fluid restriction , ¾ maintenance If symptomatic, may actually need to replace NaCl , can use hypertonic saline for example: 300cc/m2 of 1 ½ % NS Diuretics such as lasix Treat underlying disorder , for example usually resolves after removal of lung carcinomas

11. SIADH treatment cont… Demeclochlorotetracycline , blocks ADH receptors in the renal collecting ducts In severe cases , hemodialysis Warning, if increase Na too fast, at risk for pontine myelinolysis Max correction of 15mEq in 24 hours

12. DI = Diabetes Insipidus Definition: inability to effectively conserve urinary water Central: ADH not made or not released in the hypothalamic-pituitary axis Nephrogenic : ADH is released but not detected by the receptors in the kidney collecting ducts, often a sex-linked recessive condition, also due to renal pathology, electrolyte disorders, drugs

13. Central DI causes Head trauma Brain neoplasms Congenital CNS defects CNS infections CNS hypoxia ADH secretion also decreased by certain drugs: EtOh , demerol , MSO4, dilantin , barbiturates, glucocorticoids

14. DI Make sure distinguish DI from conditions in which the presence of non-absorbable, osmotically active solutes in the renal tubules prevent water re-absorption. Example: glucose loss in the urine of diabetics will decrease the tubule- medullary concentration gradient and even though ADH is there, water won’t get passively reabsorbed

15. Central DI Signs/symptoms Polyuria Dehydration, may not be readily apparent b/c of hyper- osmolarity , fluid shifts from cells to intravascular spaces and maintains blood pressure, CVP Weight loss is a better measure of fluid status

16. Central DI Lab values Hypernatremia , Na >150-160 High serum osmolality (normal 270) Urine Na < 20 mmol /L Low urine osmolality (very dilute urine)

17. Central DI T reatment Increase po or IV free H20 consumption, use hypotonic saline Volume replacement cc for cc Vasopressin/ ADH administration (bolus or drip 1.5-2.5 mU /kg/hr) Of course, treat underlying cause

18. Cerebral Salt Wasting Causes: CNS damage Closed head injury CNS surgery CNS tumors CNS infections, meningitis

19. Cerebral Salt Wasting Signs/symptoms: Polyuria Wt loss Dehydration/ hypovolemia Hypotension Low CVP

20. Cerebral Salt Wasting Lab values: Hyponatremia due to excessive renal Na loss High urine Na, > 20 mmol /L Increased plasma ANP, atrial natriuretic peptide, b/c of low volume status Inappropriately normal or low aldosterone and ADH levels despite high ANP

21. Cerebral Salt Wasting Treatment: Volume for volume replacement of urine Na losses When dc’d from hospital, most will still need oral Na supplementation for a period of time

22. DI SIADH CSW Urine Output polyuric decreased polyuric Serum Na high low low Urine Na low high high Serum osm high low Can be low or normal Urine osm low high Can be low or normal CVP Can be normal or low high low

23. GOOD LUCK SAMIR EL ANSARY ICU PROFESSOR AIN SHAMS CAIRO [email protected]