CC Jan 2018 SIADH (Syndrome of inappropriate antidiuretic hormone)

echoecho's version from 2018-03-11 23:07


Question Answer
The syndrome of SIADH was first described in 1957 in what type of patients?patients noted to have IMPAIRED ability to excrete FREE WATER in the urine
A postulated antidiuretic hormone named ______ _______(that was secreted from the posterior pituitary in response to either what)?1) arginine vasopressin (AVP) 2) to either an ABSOLUTE water deficit (hypovolemia) or a relative deficit (elevated serum osmolality in a euvolemic patient)
In euvolemic patients (those WITHOUT clinical signs of volume depletion such as orthostatic decreases in BP, decreased skin turgor, increased pulse rate, dry mucus membranes), AVP secretion is normally completely suppressed when serum osmolality falls below ______ mOsm/L?284
*** SIADH maya be diagnosed when there is evidence of AVP activity in the ABSENCE of these physiologic stimuli; in other words, in euvolemic patients with ____ or ___-____ serum osmolality?low; low-normal
SIADH is one of the most common causes of ______ and should be considered in all euvolemic patients with unexplained hyponatremia?hyponatremia
Are measurements of plasma arginine vasopressin (AVP) required? Why or why not?1) no 2) the assay is not widely available and results are delayed
In rare cases, SIADH is caused by an activating ______ of the AVP receptor in the kidney; in such cases what are the levels of plasma AVP?undetectable
*** List the criteria required to make the dx of SIADH?1) clinical euvolemia 2) low serum osmolality 3) concentrated urine
If the patient's volume status is uncertain, what therapeutic trial can be attempted to treat possible hypovolemic hyponatremia with evaluation for SIADH only if hyponatremia persists?hydration with normal saline
List the criteria for dx of SIADH as to serum osmolality, urine osmolality and urine sodium?1) serum osmolality (<270 or < 275 mOsm/L --> normal 275-290 mOsm/L. Expert opinion varies 2) urine osmolality (> 100 mOsm/L ---> normal 300-900 mOsm/L). Does not need to exceed serum osmolality 3) urine sodium (> 40 mEQ/L ----> normal 40-220 mEQ/L). May be lower in patients with very low sodium intake
What 3 conditions must be ruled out before working up SIADH, why?1) if a patient is receiving diuretics, it can cause NATRIURESIS and increase urine osmolality 2) both hypothyroidism and adrenal insufficiency can prevent normal suppression of AVP
SIADH was first described in patients with ____ cancer, but other causes have been identified like what?1) lung 2) nonmalignant pulmonary disease 3) infectious, malignant or traumatic insults to the CNS
What common-prescribed drugs can cause SIADH?1) SSRI 2) anticonvulsants 3) antipsychotics 4) NSAIDS
*** In the absence of an obvious cause, some authors recommend imaging what parts of the body to r/o occult malignancy or other lesions?1) brain 2) chest 3) abdomen 4) pelvis
Management of SIADH-associated hyponatremia depends on both the ______ and the ______ of the condition?1) acuity 2) severity
Offending meds should be d/c if possible and underlying medical causes should be addressed, true or false?true
It is important to consider the risks of extreme hyponatremia as well as the risk of osmotic ________ _________ syndrome from over rapid correction of hponatremia?osmotic demyelination
What symptoms are most likely when severe hyponatremia (sodium level < 125 mEq/L) develops over a period of < 48 hours?confusion, seizures, impaired consciousness
What is initial treatment of acute symptomatic hyponatremia?IV infusion of hypertonic (3%) saline
*** An increase in the sodium level of ___ to ____ mEQ/L is considered adequate to reverse cerebral edema associated with acute hyponatremia?4; 6
*** Patients with chronic hyponatremia are at risk of what syndrome if the hyponatremia is corrected too rapidly; therefore, if the duration of hyponatremia is uncertain, the sodium level be measured ______, with a goal of increasing the level by no more than ___ to ____ mEQ/L in a 24 hour period?1) frequently 2) 8; 12
When should hypertonic saline be stopped?when acute symptoms improve
*** In patients with chronic, asymptomatic hyponatremia, the initial treatment is what?fluid restriction
In patients with mild to moderate, persistent hyponatremia despite fluid restriction, decisions about additional therapy should balance the risks of ongoing hyponatremia, how so?for example fall risk or cognitive impairment with risks of medical therapy for SIADH
Describe Demeclocycline (Declomycin)?1) induces renal resistance to the effects of AVP 2) used as a second-line agent when fluid restriction fails to correct hyponatremia 3) does not have FDA approval 4) risks (nephrotoxicity and photosensitivity)
Name two meds that have FDA approval for treatment of hyponatremia?Vasopressin receptor antagonists = 1) conivaptan (Vaprisol) 2) Tolvaptan (Samsca)
Which of the above two meds is only available in IV form and inidicated in hospitalized patients? Which can be administered orally but should only be initiated in a hospital setting where sodium levels can be monitored frequently? What are the risks of these agents?1) Convaptan 2) Tolvaptan 3) osmotic demyelination from over rapid correction, dehydration and drug interactions
Trials of the above meds included very few pts w/ severe asymptomatic hyponatremia, so what are not well characterized?risks and benefits
Because of risks of dehydrations, vasopressin receptor antagonist therapy should not be used in what type of patient?patients that are fluid restricted
*** SUMMARY = When is SIADH considered to be the cause of the hyponatremia?in hyponatremic, euvolemic patients with low serum osmolality and a concentrated urine
*** SUMMARY = Rapid correction of hyponatremia can result in what?osotic demyelination syndrome
*** SUMMARY = Hypertonic saline may be used for the treatment of severe hyponatremia. What is usually sufficient for mild cases?fluid restrictions
*** SUMMARY = Close monitoring of the patient's clinic status and of the ______ level are essential in the management of SIADH and hyponatremia.