SAMIR EL ANSARYICU PROFESSOR

AIN SHAMSCAIRO

Global Critical Carehttps://www.facebook.com/groups/1451610115129555/#!/groups/145

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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.

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

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

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

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

SIADHsigns 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

SIADHlab 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

SIADHlab values

• Urine osmolality is inappropriately high, can range b/t 300-1400

mosm/L

• CVP is high from free water retention

SIADHTreatment

• 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

SIADHtreatment 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

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

Central DIcauses

• Head trauma

• Brain neoplasms

• Congenital CNS defects

• CNS infections

• CNS hypoxia

• ADH secretion also decreased by certain drugs: EtOh, demerol, MSO4, dilantin, barbiturates, glucocorticoids

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

Central DISigns/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

Central DILab values

• Hypernatremia, Na >150-160

• High serum osmolality (normal 270)

• Urine Na < 20 mmol/L

• Low urine osmolality (very dilute urine)

Central DITreatment

• 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

Cerebral Salt Wasting

Causes:

• CNS damage

• Closed head injury

• CNS surgery

• CNS tumors

• CNS infections, meningitis

Cerebral Salt Wasting

• Signs/symptoms:

–Polyuria

–Wt loss

–Dehydration/hypovolemia

–Hypotension

–Low CVP

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

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

DI SIADH CSWUrine 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

GOOD LUCK

SAMIR EL ANSARY

ICU PROFESSOR

AIN SHAMS

CAIRO

elansarysamir@yahoo.com

Global Critical Carehttps://www.facebook.com/groups/1451610115129555/#!/groups/145

1610115129555/ Wellcome in our new group ..... Dr.SAMIR EL ANSARY