Flashcards in Dysnatremias Deck (106)
What is hypernatremia?
Sodium over 145
What are the 2 main phases of hypernatremia?
Generation and maintenance
What are 2 forms of generation phase of hypernatremia?
1. Loss of later
2. Gain of salt (sodium ingestion via salt tabls and infant formula, mineralocorticoid excess, and iatrogenic via IV fluids, dialysis, tube feeds, and TPN)
What are 2 forms of the maintenance phase of hypernatremia?
1. Failure to drink water
2. Inability to sense thirst
Are hyper and hypo natremia issues with salt?
NO they are issues with water
General view of hypernatremia?
Loss of water leading to dehydration
-If patient can take in H20 normally, it shoudl correct itself
What is hypernatremia most often caused by?
A loss of water either renal or extra renal
What are 2 renal causes for loss of water leading to hypernatremia?
1. Diabetes insipidus
2. Osmotic diuresis
What are the 2 types of diabetes insipidus?
Describe central DI?
Inability of brain to release ADH
-Caused by brain injury (iatrogenic (surgery), trauma, tumors, ischemic insults, infections)
-Kidneys are normal
Does central DI respond to ADH when supplied?
Describe nephrogenic DI?
Inability of kidney to respond to ADH
-The collecting tubules are impermeable to water (can be caused by chronic lithium use, congenital, or demeclocycline)
-Other causes of poor response to ADH include hypercalcemia, loop diuretics, hypokalemia, sickle cell
What is the 1st step to diagnosing DI?
Water restriction test...this differentiates psychogenic polydipsia, CDI, and NDA
In the water restriction test, what is seen if the patient has hyponatremia due to psychogenic polydipsia?
There is a progressive increase in the urine osmolarity
What is seen in the water restriction test if the patient has NDI or CDI?
NOTHING...no change in urine osmolarity
What will happen if you give ADH to someone with CDI?
THe urine osmolarity will increase
What will happen if you give ADH to someone with NDI?
No change in urine osmolarity
What will happen if you give ADH to someone with psychogenic polydipsia?
No change in urine osmolarity
What is the treatment for psychogenic polydipsia?
What is the treatment for CDI?
What is the treatment for NDI?
Diuretics...thiazide with K-sparing will increase water resorption in ADH independent regions of the kidney
What are 3 causes of osmotic diuresis?
2. Post-obstructive (can't void... like in BPH)
3. Mannitol: Diuretic that makes you pee a lot... have to keep up with fluid intake
Generally, what is happening in osmotic diuresis?
You are peeing out lots of water and become hypernatremia (you need to drink H20)...
What are 3 sources of extra renal loss of water?
1. Skin losses: Burns
2. Pulmonary Losses: Advanced COPD, breating too fast/too often
3. GI losses: Acute diarrhea, IBD
What are signs and symptoms of hypernatremia?
Confusion, lethargy, weakness, seizure, coma
What is the risk in treating hypernatremia?
The speed of correction
What is the speed of correction in chronic (over 48 hours) asymptomatic hypernatrmia?
Don't excees 0.5mEq/L/hr
What is the speed of correction in acute (less than 48 hours) symptomatic hypernatremia?
1-1.15 mEq/L/hr until symptoms improve, then slow the rate to 0.5mEw/L/hr
Why do we recheck Na levels frequently when correcting them?
Want to avoid an undesirable rate