Chemistry to study

Which PCO2 value would be seen in maximally compensated metabolic acidosis? 15mmHg 30mmHg 40mmHg 60mmHg

15mmHg *In metabolic acidosis, hyperventilation increases the ratio of bicarbonate to dissolved CO2. The extent of compensation is limited by the rate of both gas diffusion and diaphragm contraction. The lower limit is between 10 and 15 mm Hg PCO2, which is the maximum compensatory effect.

Which of the following values is the threshold critical value (alert or action level) for high plasma sodium? A. 150 mmol/L B. 160 mmol/L C. 170 mmol/L D. 180 mmol/L

160 mmol/L *The threshold for the low critical value for sodium is 120 mmol/L. This is associated with edema, hypervolemia, and circulatory overload.

Which of the following values is the threshold critical value (alert or action level) for low plasma potassium? A. 1.5 mmol/L B. 2.0 mmol/L C. 2.5 mmol/L D. 3.5 mmol/L

2.5 mmol/L *below that level there is a grave risk of cardiac arrhythmia, which can lead to cardiac arrest. The upper alert level for potassium is usually 6.5 mmol/L, except for neonatal and hemolyzed samples. Above this level, there is danger of cardiac failure.

Percentage of serum calcium that is ionized?

45%

Which of the following conditions will cause ERRONEOUS Ca results? Assume that the samples are collected and stored anaerobically, kept at 4C until measurement, and stored for no longer than 1 hour. A. Slight hemolysis during venipuncture B. Assay of whole blood collected in sodium oxalate C. Analysis of serum in a barrier gel tube stored at 4°C until the clot has formed D. Analysis of whole blood collected in sodium heparin, 20 U/mL (low-heparin tube)

Assay of whole blood collected in sodium oxalate. *Unlike Pi, the intracellular Ca level is not significantly different from plasma Ca, and Ca is not greatly affected by diet. --Whole blood collected with 5-20 U/mL heparin and stored on ice no longer than 2 hours is the sample of choice for Ca. --Blood gas syringes prefilled with 100 U/mL heparin should not be used b/c high heparin will cause low results. --Citrate, oxalate, and EDTA must not be used b/c they chelate Ca. --Serum may be used provided that the sample is iced, kept capped while clotting, and assayed w/in 2 hours (barrier gel tubes may be stored longer)

When measuring calcium with the complexometric dye o-cresolphthalein complexone, Mag is kept from interfering by:

Adding 8-hydroxyquinoline *Will chelate Mag so that it does not interfere in the calcium assay --When Mag is measured, EDTA is used to chelate Ca

Which of the following conditions is associated with hypokalemia? A. Addison's disease B. Hemolytic anemia C. Digoxin intoxication D. Alkalosis

Alkalosis *Causes K to move from extracellular fluid into the cells in exchange for H+ to compensate for alkalosis --Addison's disease, low levels of aldosterone and cortisol that promote reabsorption of Na and secretion of K, they will have hyperkal and hyponat. --Hemolytic anemia and digoxin intoxication cause release of intracellular K.

Which electrolyte measurement is least affected by hemolysis? A. Potassium B. Calcium C. Pi D. Magnesium

Calcium *Potassium phosphorus, and Mag are the major INTRAcellular ions, slight hemolysis will cause falsely elevated results.

Which formula is most accurate in predicting plasma osmolality?

Calculated Osmolality = 2(Na) + (glucose ÷ 20) + (BUN ÷ 3) *Reference = 275-95 Osm/kg

what role does CTx and NTx play in the management of osteoporosis?

Decreased urinary excretion indicates a positive response to treatment *used to monitor medications such as biphosphonates that inhibit bone resorption. DEXA scan, an x-ray procedure based on subtraction of surrounding tissue, is the most sensitive diagnostic test for osteoporosis and can show bone loss as small as 1%, but takes months before a DEXA scan shows increased bone remodeling following treatment.

Which of the following conditions is classified as normochloremic acidosis? Diabetic ketoacidosis Chronic pulmonary obstruction Uremic acidosis Diarrhea

Diabetic ketoacidosis *Bicarbonate deficit will lead to hyperchloremia unless the bicarbonate is replaced by an unmeasured anion. In diabetic ketoacidosis, acetoacetate and other ketoacids replace bicarbonate. The chloride remains normal or low and there is an increased anion gap.

Which of the following conditions is most likely to produce an elevated plasma potassium? A. Hypoparathyroidism B. Cushing's syndrome C. Diarrhea D. Digitalis overdose

Digitalis overdose *Causes K to leave cells and enter extracellular fluid --Hypoparathyroidism indirectly causes hypokalemia by inducing alkalosis via increased renal retention of phosphate and bicarbonate. --Cushing's syndrome (adrenal cortical hyperfunction) results in low potassium and elevated sodium

Which of the following conditions is associated with hyponatremia? A. Diuretic therapy B. Cushing's syndrome C. Diabetes insipidus D. Nephrotic syndrome

Diuretic therapy *Diuretics lower blood pressure by promoting water loss. This is accomplished by causing sodium loss from the proximal tubule and/or loop. Addison's disease, syndrome of inappropriate ADH release, burns, diabetic ketoacidosis, hypopituitarism, vomiting, diarrhea, and cystic fibrosis also cause hyponatremia

Which of the following conditions involving electrolytes is described correctly? A. Pseudohyponatremia occurs only when undiluted samples are measured B. Potassium levels are slightly higher in heparinized plasma than in serum C. Hypoalbuminemia causes low total calcium but does not affect Cai D. Hypercalcemia may be induced by low serum magnesium

Hypoalbuminemia causes low total calcium but does not affect Cai *When serum albumin is low, the equilibrium between bound and Cai is shifted, producing increased Cai . This inhibits release of PTH by negative feedback until the Cai level returns to normal. Potassium is released from platelets and leukocytes during coagulation, causing serum levels to be higher than plasma --Magnesium is needed for release of PTH, and PTH causes release of calcium and magnesium from bone. Therefore, hypocalcemia can be associated with either magnesium deficiency or magnesium excess. --Pseudohyponatremia is a measurement error caused by diluting samples containing excessive fat or protein. The colloids displace plasma water, resulting in less electrolytes being delivered into the diluent.

Which of the following conditions is associated with both metabolic and respiratory alkalosis? A. Hyperchloremia B. Hypernatremia C. Hyperphosphatemia D. Hypokalemia

Hypokalemia *Both a cause and result of alkalosis. In alkalosis, H+ ions may move from the cells into the extracellular fluid and potassium into the cells. In hypokalemia caused by overproduction of aldosterone, hydrogen ions are secreted by the renal tubules. This increase in net acid excretion results in metabolic alkalosis.

Osmal gap calculation

Measured osmolality- Calculated osmolality *Reference = 0-10 mOsm/kg

Which of the following is a marker for bone formation? A. Osteocalcin B. Tartrate resistant acid phosphatase (TRAP) C. Urinary pyridinoline and deoxypyridinoline D. Urinary C-telopeptide and N-telopeptide crosslinks (CTx and NTx)

Osteocalcin

Which of the following conditions is associated with a low serum magnesium? A. Addison's disease B. Hemolytic anemia C. Hyperparathyroidism D. Pancreatitis

Pancreatitis *Low mag can be caused by GI loss, like diarrhea and pancreatitis. --Hyperparathyroidism causes increased release of both Ca and Mag form bone --Addison's disease (adrenocorticosteroid deficiency) may be assoc. w/ increased Mag with hyperkalemia. --Hemolytic anemia causes increase release of Mag as well as K+ from damaged rbc's

The serum level of which of the following laboratory tests is decreased in both VDDR and VDRR? A. Vitamin D B. Calcium C. Pi D. Parathyroid hormone

Pi *Persons who have VDDR and VDRR have a low Pi, however: -Persons with VDDR have decreased serum Ca as well -PTH is increased in persons with VDDR b/c Ca is the primary stimulus for PTH release, but not in persons with VDRR. -The active form of vit. D, 1,25(OH)D, is low in type 1 but high in type 2 VDDR

Which of the following is the most accurate measurement of Pi in serum? A. Rate of unreduced phosphomolybdate formation at 340 nm B. Measurement of phosphomolybdenum blue at 680 nm C. Use of aminonaptholsulfonic acid to reduce phosphomolybdate D. Formation of a complex with malachite green dye

Rate of unreduced phosphomolybdate formation at 340nm

Which of the following conditions is associated with total body sodium excess? A. Renal failure B. Hyperthyroidism C. Hypoparathyroidism D. Diabetic ketoacidosis

Renal failure *In renal disease, serum sodium is often normal, although total body sodium is increased owing to fluid and salt retention.

Which electrolyte is least likely to be elevated in renal failure? A. Potassium B. Magnesium C. Inorganic phosphorus D. Sodium

Sodium *Reduced glomerular filtration coupled with decreased tubular secretion causes accumulation of potassium, magnesium, and inorganic phosphorus. Poor tubular reabsorption of sodium offsets reduced glomerular filtration.

Which electrolyte level best correlates with plasma osmolality? A. Sodium B. Chloride C. Bicarbonate D. Calcium

Sodium *Sodium and chloride are the major extracellular ions. Chloride passively follows sodium, making sodium the principal determinant of plasma osmolality.

Which statement best describes testing recommendations for vit. D? A. Vitamin D testing should be reserved only for those persons who demonstrate hypercalcemia of an undetermined cause B. Vitamin D testing should be specific for the 1,25(OH)D3 form C. Testing should be for total vitamin D when screening for deficiency D. Vitamin D testing should not be performed if the patient is receiving a vitamin D supplement

Testing should be for total vit. D when screening for deficiency *2 forms of vit. D, D2 and D3 that are formed when two hydroxyl groups are added, the first being at the 25 position by the liver and the second at the alpha-1 position by the kidney. --the majority of circulating vit. D in in the 25-hydroxylated form of D2 and D3, called 25(OH)D. --The plasma 25(OH)D concentration is an expression of both dietary and endogenous vit. D and is the most appropriate test for detecting nutritional vit. D deficiency

What is VDDR and VDRR?

VDDR - vitamin D dependent rickets (can be reversed by doses of vit. D) VDRR - vitamin D resistant rickets *rickets can result from dietary phosphate deficiency, vitamin D deficiency or an inherited disorder of either vitamin D or phosphorus metabolism

What role does vit. D measurement play in the management of osteoporosis?

Vitamin D deficiency is a risk factor for developing osteoporosis

What role does vitamin D measurement play in the management of osteoporosis?

Vitamin D deficiency is a risk factor for developing osteoporosis *Not used to diagnose, but can cause secondary osteoporosis, and together with low PTH, Ca, and estrogen are important risk factors. If one or more of these is abnormal, then bone resorption or remodeling may be abnormal, predisposing one to osteoporosis. Deficiency in vit. D also causes rickets, condition in which bones become soft owing to reduced deposition of hydroxyapatite.

How does vitamin D aid in the adsorption of calcium from the GI in the small intestine?

vitamin D is a hormone that tells the cells of the GI tract to make more Ca channels

Which of the following tests is consistently abnormal in osteoporosis? why?

High urine or serum N-telopeptide of type 1 collagen *serum/urinary Ca, total ALP, and vit. D are not sensitive or specific for osteoporosis and Ca and Ph are usually w/in limits. --Serum marks for osteoporosis include both N-telopeptide of type 1 collagen (NTx) and C-telopeptide of type 1 collagen (CCTx), they can be used to follow treatment with resorption antagonists (bisphosphonates) b/c they decrease significantly when therapy is successful.

Which of the following is the primary mechanism for vasopressin (ADH) release? A. Hypovolemia B. Hyperosmolar plasma C. Renin release D. Reduced renal blood flow

Hyperosmolar plasma *ADH is released by the posterior pituitary in response to increased plasma osmolality. Normally, this is triggered by release of aldosterone caused by ineffective arterial pressure in the kidney. Aldosterone causes sodium reabsorption, which raises plasma osmolality; release of ADH causes reabsorption of water, which increases blood volume and restores normal osmolality