SIADH, DI, Cerebral Salt SIADH, DI, Cerebral Salt WastingWasting

By Tracy Merrill MDBy Tracy Merrill MD

Feb 24, 2003Feb 24, 2003

SIADH:SIADH:

• = Syndrome of Inappropriate ADH = Syndrome of Inappropriate ADH Secretion Secretion

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

SIADH: SIADH: causescauses

• Irritation of CNS: meningitis, Irritation of CNS: meningitis, encephalitis, brain tumors, brain encephalitis, brain tumors, brain hemorrhage, hypoxic insult, trauma, hemorrhage, hypoxic insult, trauma, brain abscess, Guillain Barre, brain abscess, Guillain Barre, hydrocephalushydrocephalus

• Pulmonary disorders: pneumonia, Pulmonary disorders: pneumonia, asthma, positive end expiratory asthma, positive end expiratory pressure ventilation, CF, TB, pressure ventilation, CF, TB, pneumothoraxpneumothorax

SIADH: SIADH: causes continuedcauses continued

• Drugs: vincristine, vinblastine, Drugs: vincristine, vinblastine, opiates, carbamazepime, opiates, carbamazepime, cyclophosphamidecyclophosphamide

• Unregulated tumor production of Unregulated tumor production of ADH-like peptides: oat cell lung ADH-like peptides: oat cell lung carcinoma for example, Ewings carcinoma for example, Ewings sarcoma, carcinoma of duodenum, sarcoma, carcinoma of duodenum, pancreas, thymuspancreas, thymus

SIADH: SIADH: function of ADHfunction of ADH

• = antidiuretic hormone = vasopressin= antidiuretic hormone = vasopressin• ADH is made in the supra-optic nuclei in the ADH is made in the supra-optic nuclei in the

hypothalamus, stored in the posterior hypothalamus, stored in the posterior pituitarypituitary

• Normally released into the bloodstream when Normally released into the bloodstream when osmo-receptors detect high plasma osmolalityosmo-receptors detect high plasma osmolality

• At the kidney, attaches to receptors in the At the kidney, attaches to receptors in the collecting ducts, opens up water channels collecting ducts, opens up water channels

• Water is passively reabsorbed along the Water is passively reabsorbed along the kidney’s medullary concentration gradientkidney’s medullary concentration gradient

SIADH: SIADH: signs and symptomssigns and symptoms

• Decreased/low urine outputDecreased/low urine output• Signs of hyponatremia: lethargy, Signs of hyponatremia: lethargy,

apathy, disorientation, muscle cramps, apathy, disorientation, muscle cramps, anorexia, agitationanorexia, agitation

• Signs of water toxicity: nausea, Signs of water toxicity: nausea, vomiting, personality changes, vomiting, personality changes, confused, combativeconfused, combative

• If Na < 110 mEq/L, seizures, bulbar If Na < 110 mEq/L, seizures, bulbar palsies, hypothermia, stupor, comapalsies, hypothermia, stupor, coma

SIADH: SIADH: lab valueslab values

• Serum Na < 135 (Na is diluted by Serum Na < 135 (Na is diluted by excessive free water re-absorption)excessive free water re-absorption)

• Serum osmolality low, normal is ~ 270Serum osmolality low, normal is ~ 270

• Urine Na is inappropriately high, >20 Urine Na is inappropriately high, >20 mmol/L, actually losing Na in urine instead mmol/L, actually losing Na in urine instead of retaining it of retaining it

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

• CVP is high from free water retentionCVP is high from free water retention

SIADH: SIADH: treatmenttreatment

• Fluid restriction, ¾ maintenanceFluid restriction, ¾ maintenance• If symptomatic, may actually need to If symptomatic, may actually need to

replace NaCl, can use hypertonic replace NaCl, can use hypertonic saline for example: 300cc/m2 of 1 ½ saline for example: 300cc/m2 of 1 ½ % NS% NS

• Diuretics such as lasix Diuretics such as lasix • Treat underlying disorder, for example Treat underlying disorder, for example

usually resolves after removal of lung usually resolves after removal of lung carcinomascarcinomas

SIADH: SIADH: treatment cont…treatment cont…

• Demeclochlorotetracycline, blocks Demeclochlorotetracycline, blocks ADH receptors in the renal collecting ADH receptors in the renal collecting ducts ducts

• In severe cases, hemodialysisIn severe cases, hemodialysis

• Warning, if increase Na too fast, at Warning, if increase Na too fast, at risk for pontine myelinolysisrisk for pontine myelinolysis

• Max correction of 15mEq in 24 hours Max correction of 15mEq in 24 hours

DI = Diabetes InsipidusDI = Diabetes Insipidus

• Definition: inability to effectively conserve Definition: inability to effectively conserve urinary waterurinary water

• Central: ADH not made or not released in Central: ADH not made or not released in the hypothalamic-pituitary axisthe hypothalamic-pituitary axis

• Nephrogenic: ADH is released but not Nephrogenic: ADH is released but not detected by the receptors in the kidney detected by the receptors in the kidney collecting ducts, often a sex-linked collecting ducts, often a sex-linked recessive condition, also due to renal recessive condition, also due to renal pathology, electrolyte disorders, drugspathology, electrolyte disorders, drugs

Central DI: Central DI: causescauses

• Head traumaHead trauma• Brain neoplasmsBrain neoplasms• Congenital CNS defectsCongenital CNS defects• CNS infectionsCNS infections• CNS hypoxiaCNS hypoxia• ADH secretion also decreased by ADH secretion also decreased by

certain drugs: EtOh, demerol, MSO4, certain drugs: EtOh, demerol, MSO4, dilantin, barbiturates, glucocorticoidsdilantin, barbiturates, glucocorticoids

DI:DI:

• Make sure distinguish DI from conditions in Make sure distinguish DI from conditions in which the presence of non-absorbable, which the presence of non-absorbable, osmotically active solutes in the renal osmotically active solutes in the renal tubules prevent water re-absorption.tubules prevent water re-absorption.

• Example: glucose loss in the urine of Example: glucose loss in the urine of diabetics will decrease the tubule- diabetics will decrease the tubule- medullary concentration gradient and medullary concentration gradient and even though ADH is there, water won’t get even though ADH is there, water won’t get passively reabsorbedpassively reabsorbed

Central DI: Central DI: signs/symptomssigns/symptoms

• PolyuriaPolyuria

• Dehydration, may not be readily Dehydration, may not be readily apparent b/c of hyper-osmolarity, apparent b/c of hyper-osmolarity, fluid shifts from cells to intravascular fluid shifts from cells to intravascular spaces and maintains blood spaces and maintains blood pressure, CVPpressure, CVP

• Weight loss is a better measure of Weight loss is a better measure of fluid statusfluid status

Central DI: Central DI: Lab valuesLab values

• Hypernatremia, Na >150-160Hypernatremia, Na >150-160

• High serum osmolality (normal 270)High serum osmolality (normal 270)

• Urine Na < 20 mmol/L Urine Na < 20 mmol/L

• Low urine osmolality (very dilute Low urine osmolality (very dilute urine)urine)

Central DI: Central DI: treatmenttreatment

• Increase po or IV free H20 Increase po or IV free H20 consumption, use hypotonic salineconsumption, use hypotonic saline

• Volume replacement cc for ccVolume replacement cc for cc

• Vasopressin/ ADH administration Vasopressin/ ADH administration (bolus or drip 1.5-2.5 mU/kg/hr)(bolus or drip 1.5-2.5 mU/kg/hr)

• Of course, treat underlying causeOf course, treat underlying cause

Cerebral Salt WastingCerebral Salt Wasting

• Causes: CNS damageCauses: CNS damage– Closed head injuryClosed head injury– CNS surgeryCNS surgery– CNS tumorsCNS tumors– CNS infections, meningitisCNS infections, meningitis

Cerebral Salt WastingCerebral Salt Wasting

• Signs/symptoms:Signs/symptoms:– PolyuriaPolyuria– Wt lossWt loss– Dehydration/hypovolemiaDehydration/hypovolemia– HypotensionHypotension– Low CVPLow CVP

Cerebral Salt WastingCerebral Salt Wasting

• Lab values: Lab values: – Hyponatremia due to excessive renal Na Hyponatremia due to excessive renal Na

lossloss– High urine Na, > 20 mmol/LHigh urine Na, > 20 mmol/L– Increased plasma ANP, atrial natriuretic Increased plasma ANP, atrial natriuretic

peptide, b/c of low volume statuspeptide, b/c of low volume status– Inappropriately normal or low aldosterone Inappropriately normal or low aldosterone

and ADH levels despite high ANPand ADH levels despite high ANP

Cerebral Salt WastingCerebral Salt Wasting

• Treatment:Treatment:– Volume for volume replacement of urine Volume for volume replacement of urine

Na losses Na losses – When dc’d from hospital, most will still When dc’d from hospital, most will still

need oral Na supplementation for a need oral Na supplementation for a period of timeperiod of time

DIDI SIADHSIADH CSWCSWUrine Urine OutputOutput

polyuricpolyuric decreaseddecreased polyuricpolyuric

Serum NaSerum Na highhigh lowlow lowlow

Urine NaUrine Na lowlow highhigh highhigh

Serum osmSerum osm highhigh lowlow Can be low Can be low or normalor normal

Urine osmUrine osm lowlow highhigh Can be low Can be low or normalor normal

CVPCVP Can be Can be normal or normal or lowlow

highhigh lowlow