Lab Flashcards
Why do we measure sodium levels
basic assessment of fluid status, and free water
Changes in sodium levels can cause
changes in mental status particularly in the elderly,
focal neuro déficits
seizures
a more rapid change in sodium level the greater the risk
this is due to fluid shifts in the skull
causes of hypernatremia
free water loss
sources of free water loss
urine, sweat, resp, GI
how to correct hypernatremia
given free water slowly, you can correct the na as quickly as it occurred
who gets hypernaremia
dementia patients, no thirst sense
ICU patients
Causes of hyponatremia
(pseudo-hyponatremia : high triglycerides, high blood sugars)
- hypothyroidism, hypoaldosteronism (hypoadrenal)
- Hypervolemic (CHF, cirrhosis) diuresis.. leave alone
- Euvolemic (SIADH) (PNA, Lung CA).. restrict free water
- Hypovolemic (The Brain prioritizes volume over Na and releases ADH in hypovolemic state) give fluids (NS)
What does aldosterone do?
Released by the kidneys in order to maintain NA and fluid.. retains NA and fluid and excretes potassium
Hypoaldosteronism: Addison’s disease, spironolactone, ACE, ARB—- high K and low sodium
Hyperaldoteronism: adrenal tumor.. high potassium
Causes of hyperkalemia
AKI
AKI
AKI soon to come
-hypoaldosterone state: Addison’s disease, spironolactone, ACE, ARB
- Hypoinsulin (K can not get into the cell.. once you give insulin K will drop)
- cellular injury, rhabdo, tumor lysis
treatment of hyperkalemia
Acutely: insulin and dextrose, beta agonist (albuterol)
sub-acute: kayexalte plus BM
Causes of Hypokalemia
- decreased gut absorption (diarrhea not vomiting)
- Increased loss through kidneys (diuretics: loop, HCTZ)
- Hyperaldosterone
- Hypomag (cannot hold onto K.. mostly seen in ETOH abuse)
- increased cellular entry ( beta agonist, Alkalosis)
Low bicarb means…
- decrease imply one of two types of metabolic acidosis, but always check the gap NA- (CL+Bicarb)
Main causes of Gap acidosis
if the gap is high there is extra acids.. there is often a life threatening process causing a gap
SAD
Shock/sepsis: lactate
AKI: kidneys can not get rid of acid (indication for dialysis)
DKA: ketones
Causes of Non gap acidosis and what does it look like
- bicarb is low but the CL is high so there is no increase in the gap… LOSS OF BICARB
- diarrhea- bicarb rich fluids from the pancreas
- dehydration- especially after saline given
- RTA (renal tubal acidosis)
Creatinine
it is a muscle breakdown product of creatine, its released from muscle into the plasma in a fairly steady state
- roughly a marker for GFR marker of kidney function
- it is related to muscle mass
- 1.3 might be normal for a big muscle man, and 1.0 might be high for elderly women with low muscle mass
the relationship between Creatinine and GFR and how to use creatine
is curvilinear… a change from 1.0-1.2 implies a much bigger change in GRF than 6-7
- convert to GFR using MDRD
- tread over time
- use in the context of the patient.. urine output and volume overload
causes of creatinine
only AKI
BUN
Not as good as creatinine, helps to suggest prerenal
- byproduct of protein degradation
- Low– not much.. maybe poor nutritional status
- high– think AKI.. maybe GI bleed, TPN
Mag.. why do we check it
- when low can lead to hypocalcemia and hypokalemia
- arrhythmias when mag low
- check in patients at risk for arrhythmias and patients asa risk for hypomag.. ETOH abuse
causes of hypomag
- renal losses ( diuresis, loop)
- ETOH abuse.. chronic.. mag wasting by the kidneys
- Tacrolimis
why is calcium important
stabilizes electrochemical gradients across cells
- allows cells that rely on action potentials to work
so critical for normal functioning of muscles cells ( heart, skeletal, smooth) and neurons
calcium homeostasis
controlled by the parathyroid hormone which works on
- kidneys- to increase calcium absorption and excrete phos
- Gut- increased calcium absorption and excrete phos
- Bone- releases calcium and phos from the bone
high phos levels stimulate PTH
High calcium levels turn of PTH
signs and symptoms of hypercalcemia
- excessively stabilizes electrically active cells
- slows smooth muscle cells and nerve cells
- also leads to increase risks of stone formation
- depressed
primary hyperparathyroid
- a single small adenoma on one of the four glands
- secretes excess PTH
- usually slight elevations in calcium
- typically in middle aged women
- usually not a problem but worry about osteoporosis fractures
secondary hyperparathyroidism
- kidney disease patients
- kidneys can not remove excess phosphate
- continued hyperphos stimulates PTH release
- mild hypercalcemia with hyperphos
- risk is severe damage to bone health
- treatment: phos binders
hypercalcemia of malignancy
- extremely high calcium– 12-13
- cancer cells secrete a hormone that looks like PTH
– lung cancers in particular
real PTH is actually low
