electrolyte and acid base balance (acute care common problems) Flashcards
what is normal range for urine sodium?
10-20 mEq/L
what is normal range for Na serum osm?
2x Na (2x 135-145)
how would you detect renal salt wasting? what does this mean?
urine sodium >20 mEq (increased- more sodium excretion in urine)– problem with kidneys because kidneys are supposed to retain sodium for water balance
if urine sodium low (<10mEq/L)
this suggests that kidneys are compensating for extrarenal fluid losses- general hypovolemic state from other sources, not a problem with the kidneys
hypotonic hyponatremia (serum osm < 280, Na <140)— how do you determine if hypervolemic or hypovolemic?
hypovolemic and if urine sodium < 10 mEq-> non renal causes: dehydration, diarrhea, vomiting
hypovolemic and if urine sodium >20: low volume and kidneys cannot conserve Na: d/t diuretics, ACE inhibitors, mineralocorticoid deficiency
hypervolemic and hypotonic- fluid overload- need to restrict water- edematous states, CHF, ESRD, liver disease
hypertonic hyponatremia: describe
serum osm > 290
hyperglycemia: usually from HHNK
osm high, sodium is low- osm are from other source: like glucose- causes fluid overload
tx: based on cause, tx underlying condition, if hypervolemic- water restriction, give NS or hypertonic NS with diuretics
hypernatremia
always hyperosm; deficiency of water,
due to excess water loss
excessive sodium intake is rare, occasionally it’s from NS fluid administration- iatrogenic
if hypovolemic- treat with NS or 1/2 NS
if euvolemic- treat with free water D5W
if hypervolemic- treat with free water and loop diuretics or dialysis
hypokalemia: causes
loop diuretics- not potassium sparing
diarrhea
excess renal loss and alkalosis
elevated serum epi in trauma patients
s/s: muscle weakness, fatigue, muscle cramps, constipation d/t smooth muslce involvement, severe- flaccid paralysis, tetany, rhabdo
ECG- decreased amplitude, broad T waves, PVCs, Vtach, Vfib
hyperkalemia
excess intake, renal failure, drugs (NSAIDS), hypoaldosteronism, cell death, acidosis causes shift of K to extracellular space- K increases 0.7mEq with each .1 drop in pH
symptoms: diarrhea, abdominal distension, flaccid paralysis
ECG changes- peaked T waves, only occurs in 50% of patients
Tx. kayexalate, insulin D50
calcium vs ionized calcium
normal calcium: 8.5-10.5 mg/dl
ionized calcium 4.5-5.5 mg/dl
ionized calcium doesn’t vary with albumin level- useful to measure when serum albumin not within normal range. 50% of calcium binds to albumin- so if low albumin, calcium level may appear normal but they’re really hypercalcemic
increases with acidemia, decreases with alkalemia
hypocalcemia
causes: hypoparathyroidism, hypomagnesemia, pancreatitis, renal failure, severe trauma, multiple blood transfusions
s/s: increased DTRs, cramping, Trousseau’s sign (carpopedal spasm), Chvostek’s sign, prolonged QT
how to test for Trousseau’s sign?
BP cuff inflated on arm, causes flexion at wrist/ hand joints due to arterial occlusion for a few minutes
hypocalcemia/ tetany
how to test for Chvostek’s sign
tap cheek- abnormal reaction - facial muscles contract due to hyperexcitability
hypocalcemia, tetany
hypercalcemia
cause: hyperparathyroidism, hyperthyroidism, vitamin D intoxication, prolonged immobilization, thiazide diuretics
s/s: muscle weakness, fatigue, depression, anorexia, n/v/ constipation, coma/ death (severe)
Tx: calcitonin if impaired renal function
NS with loop diuretics, dialysis in severe cases
respiratory acidosis
pH < 7.35, pCO2> 45 mg
CO2 retention- decreased ventilation
leads to confusion, lethargy, myoclonus, asterixis
respiratory alkalosis
hyperventilation - decreased pCO2, increased pH
s/s- decreased cerebral blood flow—> light headed, anxiety, paresthesia, peripheral tingling
tx underlying cause- slow hyperventilation,
if chronic alkalosis; may lead to metabolic acidosis
metabolic acidosis
low serum bicarb.
high anion gap- = acidosis
causes of increased anion gap/ metabolic acidosis
DKA, alcoholic ketoacidosis, lactic acidosis
causes of metabolic acidosis with normal anion gap
diarrhea, ileostomy, renal tubular acidosis, recovery from DKA
**GI losses- effects electrolyte abnormalities
DKA treatment and anion gap
you have to close the gap before you can stop the insulin infusion, because electrolyte abnormalities are normalizing. it indicates that lactic acid formation is not occurring; regulation of insulin and glucose levels
what is normal anion gap range?
4-12mmol/L
metabolic alkalosis
high bicarb, compensatory high CO2- to decrease pH
if CO2 > 55- superimposed respiratory acidosis
cause: post-hypercapnia alkalosis, NG suction, vomiting, diuretics
tx. correct volume deficit with NaCl and KCl
discontinue diuretics, famotidine in GI loss
acetazolamide if volume replacement is contraindicated
how to calculate anion gap?
Na + K+ Cl + HCO3 (bicarb)
