by prof dr samie alanasary prof of icu ain shams university

1. 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
Treatment
• 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
elansarysamir@yahoo.com