Electrolyte Abnormalities Flashcards
Hyponatremia is defined by a serum Na of what?
Serum Na <135
Hyponatremia is very common especially in which popultions?
hospitalized, ICU patients
ADH is released in response two which two stimuli?
Osmotic stimuli from increases in serum osmolarity detected by osmoreceptors in the anterior hypothalamus
non-osmotic stimuli from decreases in BP or BV detected by aterial baroreceptors
What are some other non-osmotic stimuli for ADH release?
Baroreceptors
Nausea
Hypoxia
Pain
Medications
Pregnancy
Hyponatremia results primarily from increases in what?
increases in TBW, not changes in sodium
(can be from increase in fluid intake or decrease in water excretion)
What are the clinical manifestations of hyponatremia?
depends on severity and acuity, most asymptomatic until levels are <125
- headache
- fatigie
- dizziness
- nausea
- seizures
- cerebral edema
What is necessary when working up hyponatremia to minimize confusion on the underlying etiology?
a systematic approach
Acute hyponatremia is a low Na level for how long?
<48hours
chronic >48hrs or unknown duration
What are the two steps of approaching hyponatremia?
- measure serum osmlarity to determine if hypotonic, isotonic or hypertonic hyponatremia is present
- if hypotonic hyponatremia is present, then assess volume status by measuring random urine Na and urine osmolarity
When assessing for hyponatremia, it is important that all labs be drawn (apart or simultaneously?)
simultaneously
best to avoid treatment until labs are drawn
What are some exam findings indicative of hypovolemia?
hypotension
orthostatic VS +
tachycardia
poor cap refill
dry mucosa
flat JV
decreased urine output
>50% collapse of IVC during echo
What are some exam findings of hypervolemia?
hypertension
sacral or LE edema
JVD
dilated IVC on echo
What is a diagnosis of exclusion after ruling out cortisol deficiency, hypothyroidism and other causes?
What is the most common malignancy associated with this?
SIADH
Small cell lung cancer
What drugs are associated with SIADH?
antidepressents
anti convulsants
antipsychotics
cyclophosphamide
opiates
MDMA
What presents as a true hyponatremia with euvolemia and urine osm > 300?
SIADH
How to treat acute hyponatremia?
can have rapid correction of Na with little risk of ODS
how is chronic hyponatremia treated?
careful of rapid correction as pt is at higher risk of ODS
goal is to raise serum Na by 8-10mEq/day with no more than 18mEq/L within the first 48hrs
For symptomatic hyponatremic patients give what to raise Na quickly (acute setting)?
Give hypertonic saline 3% solution
(raise it to 3-4 mEq/L to stop symptoms and then slowly raise back to normal)
If Na is correcting too quickly, how can you lower it back to acceptable level to avoid ODS?
D5W
DDAAVP
d/c some therapies that may be raising Na too fast
Besides hypertonic saline for SIADH, what else is used in treatment?
Water restriction
Furosemide
Salt/urea tablets
What are four severe complications of hyponatremia?
Seizures
coma
Death from uncal herniation
ODS