electrolyte and acid base balance (acute care common problems)

Question 1

what is normal range for urine sodium?

Answer 1

10-20 mEq/L

Question 2

what is normal range for Na serum osm?

Answer 2

2x Na (2x 135-145)

Question 3

how would you detect renal salt wasting? what does this mean?

Answer 3

urine sodium >20 mEq (increased- more sodium excretion in urine)– problem with kidneys because kidneys are supposed to retain sodium for water balance

Question 4

if urine sodium low (<10mEq/L)

Answer 4

this suggests that kidneys are compensating for extrarenal fluid losses- general hypovolemic state from other sources, not a problem with the kidneys

Question 5

hypotonic hyponatremia (serum osm < 280, Na <140)— how do you determine if hypervolemic or hypovolemic?

Answer 5

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

Question 6

hypertonic hyponatremia: describe

Answer 6

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

Question 7

hypernatremia

Answer 7

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

Question 8

hypokalemia: causes

Answer 8

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

Question 9

hyperkalemia

Answer 9

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

Question 10

calcium vs ionized calcium

Answer 10

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

Question 11

hypocalcemia

Answer 11

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

Question 12

how to test for Trousseau’s sign?

Answer 12

BP cuff inflated on arm, causes flexion at wrist/ hand joints due to arterial occlusion for a few minutes
hypocalcemia/ tetany

Question 13

how to test for Chvostek’s sign

Answer 13

tap cheek- abnormal reaction - facial muscles contract due to hyperexcitability
hypocalcemia, tetany

Question 14

hypercalcemia

Answer 14

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

Question 15

respiratory acidosis

Answer 15

pH < 7.35, pCO2> 45 mg
CO2 retention- decreased ventilation
leads to confusion, lethargy, myoclonus, asterixis

Question 16

respiratory alkalosis

Answer 16

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

Question 17

metabolic acidosis

Answer 17

low serum bicarb.

high anion gap- = acidosis

Question 18

causes of increased anion gap/ metabolic acidosis

Answer 18

DKA, alcoholic ketoacidosis, lactic acidosis

Question 19

causes of metabolic acidosis with normal anion gap

Answer 19

diarrhea, ileostomy, renal tubular acidosis, recovery from DKA
**GI losses- effects electrolyte abnormalities

Question 20

DKA treatment and anion gap

Answer 20

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

Question 21

what is normal anion gap range?

Answer 21

4-12mmol/L

Question 22

metabolic alkalosis

Answer 22

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

Question 23

how to calculate anion gap?

Answer 23

Na + K+ Cl + HCO3 (bicarb)