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43 Cards in this Set
- Front
- Back
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What's a normal urine osm?
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50-1000
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If someone has a normal serum osmolality, can you have an abnormal urine osmolality?
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NO!
Not necessarily |
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What's normal urine output?
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less than 4L
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What will happen in diabetes insipidus in a water depletion state?
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Increase in plasma osmolality with a non-increase in urine osmolality.
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Where does diabetes insipidus originate, generally?
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From the hypothalamus; ADH deficiency
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What is defective in diabetes insipidus?
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ADH secretion
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What is the most common cause of diabetes insipidus? Other causes?
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Trauma secondary to surgery
Neoplasm Idiopathic Familial |
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What is the effect of diabetes insipidus on urine osmolality?
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You can't concentrate it!
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How do people with diabetes insipidus maintain proper water balance?
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Drinking a TON!
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What happens if someone with DI has limited access to water?
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Hypernatremia
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What is the effect of an impaired thirst center in the context of diabetes insipidus?
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TROUBLE!
The person can't perform the minute-minute regulation of thirst, so they're either volume lowered or expanded chronically. |
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How do you go about making a diagnosis of DI?
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Water deprivation test
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What are the different types of diabetes insipidus?
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Pituitary DI
Nephrogenic DI Primary polydipsia |
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What happens in pituitary DI?
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Unable to concentrate urine despite hyperosmolar serum
After dDAVP injection, Uosm increases |
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What happens in nephrogenic DI?
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Unable to increase urine osmolality after water deprivation and after dDAVP
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What happens in primary polydipsia?
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Should concentrate the urine normally following water deprivation
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What are causes of nephrogenic DI?
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Familial
Renal disease Hypercalcemia Hypokalemia Lithium therapy |
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What occurs in SIADH?
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Sydrome of inappropriate ADH
Secretion of ADH despite water retention and plasma hypotonicity |
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What's the most common cause of hyponatremia?
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SIADH
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What are the causes of SIADH/
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CNS disorders
Malignant tumors secreting ADH Pulmonary disease Drugs |
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What kind of tumor commonly secretes ADH?
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SCC of the lung
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How do pulmonary disorders cause SIADH?
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Stimulation of low-pressure receptors in the chest to cause secretion of ADH
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What happens in the pathophysiology of SIADH?
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You continue to drink despite an ability to dilute urine and excrete excess water.
Volume expansion and hypotonicity New steady state is attained, but only after significant water retention has occurred |
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Why don't people with SIADH get hypertnsive?
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They distribute the water across the whole body, not just inside the vascular system
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When do you start to see neurologic abnormalities in SIADH?
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When the sodium levels is below 120
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What are symptoms that a patient can have when the sodium is between 110 and 120?
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Confusion and Lethargy
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What kinds of symptoms can a patient have if they've got a sodium that's below 110?
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Convulsions
Coma DEATH! |
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What determines the severity of symptoms in SIADH?
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Absolute level
Rate of fall Rate of fall is MORE IMPORTANT! If someone goes to 140 to 120 over a couple of days will be SIGNIFICANTLY more symptomatic than someone who makes the same fall over a month |
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What are the electrolyte states of a patient with SIADH?
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Hypotonic
Hyponatremic Inappropriately hypertonic urine |
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What is the relationship between urine osm and serum osm, usually?
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Urine osm > serum osm
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Other than SIADH, what are causes of hyponatremia?
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Hyperglycemia
Hyperlipidemia |
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How does hyperglycemia cause hyponatremia?
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Glucose doesn't cross the cell membrane without insulin. People get hyperglycemic without inuslin.
Because there's so much glucose in the extracellular space, you get water that's drawn out there, diluting the sodium, causing problems with sodium balance. |
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What are some conditions that can stimulate ADH secretion?
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Volume depletion
Heart failure Cirrhosis Nephrotic syndrome Hypothyroidism Cortisol deficiency |
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What's the overall pattern for the evaluation of someone with SIADH?
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1. Patient has to be hypotonic, hyponatremic, with inappropriately hypertonic urine
2. Exclude other causes of hyponatremia 3. Evaluate for conditions known to stimulate ADH |
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What's the treatment for SIADH?
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1. Hypertonic taline
2. Conivaptan 3. DON'T CORRECT THE HYPONATREMIA TOO RAPIDLY! |
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Why does giving normal saline to someone with SIADH cause problems?
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The kidneys are ALREADY concentrating the urine to around 500 meq/L
They'll take the 300 meq/L of sodium that you give it and excrete it in less volume than you put in. So, instead of giving them electrolytes, you're worsening the hyponatremia and exacerbating the problems. Don't kill patients! |
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What is the mechanism of conivaptan?
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IV ADH V2 receptor antagonist
Promotes water excretion, increases osmolality |
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Where in the brain will you cause problems with a rapid correction of sodium?
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Pons.
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What's the upper limit for sodium correction?
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5. meq/hr
12 meq/day |
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How do you treat chronic SIADH/
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1. Treat the underlying disorder
2. WATER RESTRICTION! 3. Tolvaptan 4. Drugs which cause nephrogenic diabetes insipidus. |
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What's the mechanism of tolvaptan?
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Orally active V2 receptor inhibitor.
$$$$$$$$ |
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What kinds of drugs can cause nephrogenic DI?
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Democlocycline
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Which patients with heart failure need water restriction?
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People who have problems with serum sodium.
It depends on their baroreceptor status and how it effects their ADH functioning. THIS IS IMPORTANT!!!!!! |
