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68 Cards in this Set

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how do you analyzed ABG values?
1. pH indicates alkalosis or acidosis
2. look at CO2 level in conjunction with pH
3. look at bicarb level relative to the pH
T/F: the body does NOT compensate beyond a normal pH
true
common causes of respiratory acidosis?
1. COPD
2. asthma
3. drugs (eg. opioids, benzos, barbiturates, etoh, other resp. depressants)
4. chest wall problems (paralysis, pain)
5. sleep apnea
common causes of metabolic acidosis?
1. etoh
2. DKA
3. uremia
4. lactic acidosis (eg. sepsis, shock, bowel ischemia)
5. methanol, ethylene glycol
6. aspirin, salicylate o/d
7. diarrhea
8. carbonic anhydrase inhibitors
common causes of respiratory alkalosis?
1. anxiety, hyperventilation
2. aspirin, salicylate o/d
common cause of metabolic alkalosis?
1. diuretics (ex. carbonic anhydrase inhibitors)
2. vomiting
3. volume contraction
4. antacid abuse, milk-alkali syndrome
5. hyperaldosteronism
what type of acid/base disturbance does aspirin o/d cause? other sx? improve disturbance?
1. resp. alkalosis and metabolic acidosis

2. look for coexisting tinnitus, hypoglycemia, vomiting, hx of "swallowing several pills"

3. alkalization of urine (with bicarb) speeds secretion
what happens to blood gas of pts with chronic lung conditions?
- pH may be alkaline during day b/c they breathe better when awake
- also, the compensatory metabolic alkalosis can become the primary problem in pts. just recovering from bronchitis or other resp. d/o
what type of heart problem can be caused by sleep apnea (and other chronic lung conditions)?
R sided heart failure (cor pulmonale)
how do you treat a pt with acidosis?
DON'T give bicarb

first give IV fluids and correct the underlying d/o

if all measures fail and pH < 7.0, then bicarb may be given
what is pH of a typical asthmatic pt during an attack?
slightly alkalotic

if not, you should wonder why and consider intubation
if pt with asthma attack goes from alkalotic to acidotic, what are next steps?
1. prepare for elective intubation
2. continue aggressive med tx with beta-2 agonists, steroids and O2
what are symptoms of hyponatremia?
1. lethargy
2. mental status changes, confusion
3. anorexia
4. seizures
5. cramps
6. coma
causes of hypovolemic hyponatremia?
1. dehydration
2. diuretics
3. diabetes
4. Addison's disease/hypoaldosteronism (low K+)
causes of euvolemic hyponatremia?
1. SIADH
2. psychogenic polydipsia
3. oxytocin use
causes of hypervolemic hyponatremia?
1. heart failure
2. nephrotic syndrome
3. cirrhosis
4. toxemia
5. renal failure
how do you tx hyponatremia?

think hypovolemic vs. euvolemic vs. hypervolemic
hypovolemic: normal saline

euvolemic and hypervolemic: water/fluid restriction; may need diuretics for hypervolemic
what medication is needed if water restriction fails to treat SIADH?
demeclocycline, which induces nephrogenic diabetes insipidus
what happens if hyponatremia is corrected too quickly?
brainstem damage: central pontine myelinolysis
when do you use hypertonic saline in hyponatremic pts?
when pt has seizures from severe hyponatremia; otherwise 99% of time, use normal saline
what causes false, or spurious hyponatremia?
1. hyperglycemia; once glu > 200mg/dl, then sodium decr. by 1.6mEq/L for each rise of 100 mg/dL
2. hyperproteinemia
3. hyperlipidemia

** in these cases, lab value is low, but total body sodium is nl **
cause of hyponatremia in post-op pts?
combo of pain and narcotics (cause SIADH) with overaggressive administration of IV fluids;

rare cause may be adrenal insufficiency - in this case, potassium is high and BP is low
what is the classic cause of hyponatremia in pregnant pts about to deliver?
oxytocin; it has an antidiuretic hormone-like effect
what are signs and sx of hypernatremia?
same as in hyponatremia: mental status changes, confusion, hyperreflexia, seizures and/or coma
what causes hypernatremia?
- most common cause is dehydration or free water loss
- look for diuretics, diabetes insipidus, diarrhea, renal disease and iatrogenic causes (too much hypertonic IV fluids)
- sickle cell disease, which may lead to renal damage and isosthenuria
what is isosthenuria?
inability to concentrate urine
how do you treat hypernatremia?
- water replacement using normal saline
- once hemodynamically stable, then switch to 1/2 NS

- do NOT use 5% dextrose in water (D5W) for hypernatremia
what are the signs and sx of hypokalemia?
- muscle weakness (paralysis and ventilatory failure)
- when smooth muscles are affected, then ileus and/or hypotension
- heart findings: loss of T-wave or T-wave flattening, U waves, premature ventricular anbd atrial complexes, ventricular and atrial tachyarrhythmias
effect of pH on serum potassium?
change in pH causes cellular shift
- alkalosis causes hypokalemia
- acidosis causes hyperkalemia

if pH is deranged, first treat that before addressing the potassium
describe interaction between potassium and digitalis.
heart of pt on digitalis is VERY sensitive to potassium levels;

monitor K+ levels on all pts taking digitalis (especially is they also take diuretics!!)
how replace potassium?
- correct slowly
- try orally first; if IV is needed, don't give more than 20 mEq/hr
- keep on EKG as you correct potassium
what if hypokalemia remains even after giving significant amount of potassium?
- check magnesium; low Mg levels means body can't retain K+

- correct Mg++ if necessary
signs and sx of hyperkalemia?
- weakness and paralysis can occur

- cardiac: tall, peaked T-waves, widening of QRS, prolongation of PR interval, loss of P-waves, sine-wave pattern EKG; arrhythmias include asystole and V-fib
what causes hyperkalemia?
- renal failure (acute or chronic)
- severe tissue destruction (release intracellular K+)
- hypoaldosteronism
- medications (potassium-sparing diuretics, beta-blockers, NSAIDs, ACE inhibitors)
- adrenal insufficiency (also associated with low sodium and low blood pressure)
what are three signs of adrenal insufficiency?
- hyperkalemia
- hyponatremia
- low BP
what do you do if asymptomatic pt has hyperkalemia?
- repeat the labs; sample may have hemolyzed showing a false hyperkalemia
in general, what is the best tx for hyperkalemia?
- decr. potassium intake
- oral sodium polystyrene resin
what's the first thing to do with hyperkalemia?
check for cardiotoxicity
what is tx for hyperkalemia if K+ is>6.5 and/or cardio toxicty is apparent (more than peaked T waves)?
1. give calcium gluconate (cardio protective)
2. sodium carbonate (alkalosis pushes K+ back into cells)
3. glucose with insulin (insulin pushes K+ back into cells)
what effect does a beta-2 agonist have on K+?
pushes back into cells
what do you do with a hyperkalemic pt with renal failure or if tx fails to bring K+ lower?
prepare to institute dialysis
signs and sx of hypocalcemia?
- neuro findings; esp. tetany
- Chvostek's sign (tap on facial nerve to elicit contraction of facial muscles)
- Trousseau's sign (inflation of tourniquet or BP cuff causes hand muscle (carpopedal) spasms)
- other signs & sx: depression, encephalopathy, dementia, laryngospasm, convulsions/seizures
- QT-prolongation on EKG
what are the signs and sx of hypercalcemia?
- often asymptomatic and discovered by routine lab tests
- when symptomatic:
1. Bones (bone changes such as osteopenia and pathologic fractures)
2. Stones (kidney stones and polyuria)
3. Groans (abdominal pain, anorexia, constipation, ileus, nausea, vomiting)
4. Psychiatric Overtones (depression, psychosis, delirium, confusion)

also QT shortening on EKG; peptic ulcer disease and pancreatitis are more common in pts with hypercalcemia
first step if calcium is too low?
- check for low albumin; decreased protein-bound fraction, but ionized fraction is OK
- ie. is this 'TRUE' hypocalcemia?
how do you correct for low albumin when calculating Ca++?
for every decrease of albumin below 4 g/dl, correct Ca++ by adding 0.8 mg/dl to given Ca++ value
causes of hypocalcemia?
1. DiGeorge's syndrome (tetany 24-48 hrs after birth, absent thymic shadow on x-ray)
2. renal failure (think vitamin D metabolism)
3. hypoparathyroidism (watch for postthyroidectomy pt)
4. vitamin D deficiency
5. pseudohypoparathyoidism
6. acute pancreatitis
7. renal tubular acidosis
signs and sx of pseudohypoparathyroidism?
1. short fingers
2. short stature
3. mental retardation
4. normal levels of PTH with end-organ unresponsiveness to PTH
what is relationship between low calcium and low magnesium?
can't correct hypocalcemia until hypomagnesemia is corrected
what does alkalosis do to ionized Ca++ fraction?
causes to go into the cell
when do you see alkalosis causing Ca++ to go back into cell?
hyperventilation/anxiety syndromes

pt eliminates too much CO2, becomes alkalotic, develops perioral and extremity tingling
what is relationship between calcium and phosphorous?
- levels move in opposite directions
how do you address calcium and phosphorous levels in chronic renal failure pts?
- raise Ca++ levels with vitamin D and Ca++ supplements
- restrict phosphorous
most common cause of hypercalcemia in outpatients?
hyperparathyroidism
most common cause of hypercalcemia in inpatients?
- malignancy
- vitamin A or D intoxication
- sarcoidosis, thiazide diuretics, familial hypocalciuric hypercalcemia (look for low urinary calcium), and immobilization
- hyperproteinemia leads to high protein-bound Ca++, but normal ionized fraction
why treat asymptomatic hypercalcemia?
- avoid nephrocalcinosis and renal failure due to Ca++ deposits in kidney
- avoid bone disease due to loss of Ca++
how treat hypercalcemia?
- give IV fluids to hydrate
- then, give furosemide (ie. loop diuretic) to cause Ca++ diuresis

- other tx: phosphorous, calcitonin, disphosphonates (eg. etidronate), plicamycin, or prednisone
what diuretic is contraindicated in hypercalcemia?
thiazide diuretic
in what clinical scenario do you usually see hypmagnesemia?
alcoholism

Mg is wasted through the kidneys
signs and sx of hypomagnesemia?
similar to those of hypocalcemia (prolonged QT interval on EKG and possible tetany)
what are signs and sx of hypermagnesemia?
- first is a decrease in DTRs
- then, hypotension and resp failure
in what clinical scenario do you see hypermagnesemia?
- classically iatrogenic in pregnant pts given magnesium sulfate for preeclampsia
- also common in pts with renal failure
how treat hypermagesemia?
- stop any Mg++ infusion
- ABC's and intubate if necessary
- furosemide if need to have Mg diuresis
- last resort is dialysis
what is clinical scenario for hypophosphatemia?
pts with uncontrolled diabetes (esp. DKA) and alcoholics
signs and sx of hypophosphatemia?
- neuromuscular disturbances (encephalopathy, weakness)
- rhabdomyolysis (esp in alcoholics)
- anemia, WBC and platelet dysfunction
what is IV fluid of choice in trauma pts?
1. Ringer's lactate
2. normal saline
what is IV fluid of choice in nontrauma, hypovolemic pts?
normal saline or Ringer's lactate (regardless of other electrolyte probs)

first fill the tank, then correct imbalances that the kidney can't correct
what is maintenance fluid for pts who aren't eating?
1/2 NS with 5% dextrose in adults

1/4 or 1/3 NS with 5% dextrose in kids (because of renal differences)
what should be added to IV fluids of pts who aren't eating?
potassium chloride, 10 or 20 mEq, added to a liter of IV fluid daily to prevent hypokalemia

assume that the baseline is normal