Blood Gas
Which of the following contributes the most to the serum total CO2?
a) PCO2
b) dCO2
c) HCO3-
d) Carbonium ion
c) HCO3-
Given the following serum electrolyte data, determine the anion gap.
Na = 132 mmol/L; Cl = 90 mmol/L; HCO3- = 22 mmol/L
a) 12 mmol/L
b) 20 mmol/L
c) 64 mmol/L
d) Cannot be determined
b) 20 mmol/L
Anion gap = Na - (HCO3- + Cl)
Which of the following cardiac markers is consistently increased in persons who exhibit unstable angina?
a) Troponin C
b) Troponin T
c) CK-MB
d) Myoglobin
b) Troponin T
Persons with unstable angina (angina at rest)who have an elevated TnT are at about 8 times greater risk of having an MI within the next 6 months.
Which anticoagulant is the choice for blood gas studies?
a) Sodium citrate, 3.2%
b) Lithium heparin, 100U/mL blood
c) Sodium Citrate, 3.8%
d) Ammonium oxalate, 5.0%
b) Lithium heparin, 100U/mL blood
Which test provides the earliest warning of increased risk of coronary artery disease?
a) Glycogen phosphorylase-BB
b) TnT
c) Ischemia modified albumin
d) High-sensitivity C-reactive protein
d) High-sensitivity C-reactive protein
High-sensitivity C-reactive protein (hs-CRP) is an ultrasensitive CRP assay that accurately measures CRP below 1 mg/L. CRP is an acute phase protein increased in inflammation. Levels of CRP at the upper end of the reference range (up to 10mg/L) signal low-grade inflammation, which occurs in the asymptomatic phase of ACS.
Which of the following effects result from exposure of a normal arterial blood sample in room air?
a) PO2 increased, PCO2 decreased, pH increased
b) PO2 decreased, PCO2 increased, pH decreased
c) PO2 increased, PCO2 decreased, pH decreased
d) PO2 decreased, PCO2 decreased, pH decreased
a) PO2 increased, PCO2 decreased, pH increased
When exposed to air, blood releases CO2 gas and gains O2 and blood becomes alkaline.
Calculate the osmolal gap.
BUN = 22 mg/dL; Glucose = 160 mg/dL; Na = 150 mmol/L; Osmolality result from osmometer = 325 mOsm/Kg
28 mOsm/Kg
Osmolal gap = measured osmo - calculated osmo
Calculated osmo = 2(Na) + (glucose/18) + (BUN/2.8)
A physician calls to request a CK on a sample already sent to the laboratory for coagulation studies. The sample is 2-hour-old citrated blood and has been stored at 4°C. The plasma shows very slight hemolysis. What is the best course of action and the reason for it?
a) Perform the CK assay on the sample because no interferent is present
b) Reject the sample because it is slightly hemolyzed
c) Reject the sample because it has been stored too long
d) Reject the sample because the citrate will interfere
d) Reject the sample because the citrate will interfere
Given the following, calculate the P/F ratio. Does this indicate acute respiratory failure?
FiO2 = 90%
PO2 = 80 mmHg
P/F = 89
The P/F is <300, indicating acute respiratory failure.
Which of the statements below regarding total CK is true?
a) Levels are unaffected by strenuous exercise
b) Levels are unaffected by repeated intramuscular injections
c) Highest levels are seen in Duchenne's muscular dystrophy
d) The enzyme is highly specific for heart injury
c) Highest levels are seen in Duchenne's muscular dystrophy
Total CK is neither sensitive nor specific for acute MI. An infarct can occur without causing an elevated total CK level. Exercise and intramuscular injections cause a significant increase in total CK.
A patient's blood gas results are as follows:
pH = 7.26; PCO2 = 60 mmHg; HCO3- = 29 mmol/L
These results would be classified as:
a) Metabolic acidosis
b) Metabolic alkalosis
c) Respiratory acidosis
d) Respiratory alkalosis
c) Respiratory acidosis
Which of the following conditions will cause an increased anion gap?
a) Diarrhea
b) Hypoaldosteronism
c) Hyperkalemia
d) Renal failure
d) Renal failure
In renal failure, retention of phosphates and sulfates cause the anion gap.
A patient's CK-MB is reported as 18 μg/L and the total CK as 500 IU/L. What is the CK relative index?
a) 0.10%
b) 3.2%
c) 10.0%
d) 30.0%
b) 3.2%
CKI = (CK-MB/Total CK) x 100
A patient's blood gas results are:
pH= 7.50; HCO3-= 40mmol/L; PCO2= 55mmHg
These result indicate:
a) Respiratory acidosis
b) Metabolic alkalosis
c) Respiratory alkalosis
d) Metabolic acidosis
b) Metabolic alkalosis
Metabolic alkalosis is partially compensated for by increased PCO2.
Which of the following statements regarding the clinical use of CK-MB is true?
a) CK-MB becomes elevated before myoglobin and troponin I (TnI) after an acute MI
b) CK-MB levels are normal in cases of cardiac ischemia
c) Mass unit assays are more sensitive than electro phoretic methods
d) An elevated CK-MB level is always accompanied by an elevated total CK level
c) Mass unit assays are more sensitive than electro phoretic methods
Immuno-chemical methods for measuring CK-MB are more sensitive than electrophoresis.
a) Bicarbonate deficiency
b) Excessive retention of dissolved CO2
c) Accumulation of volatile acids
d) Hyperaldosteronism
a) Bicarbonate deficiency
Metabolic acidosis is caused by bicarbonate deficiency and metabolic alkalosis by bicarbonate excess. Respiration acidosis is caused by PCO2 retention and respiratory alkalosis is caused by PCO2 loss.
A serum/plasma contaminated with EDTA is easily recognized by .....
a) increase K, decrease Ca
a) decrease K, increase Ca
a) increase K, increase Ca
a) decrease K, decrease Ca
a) increase K, decrease Ca
Which statement best describes the clinical utility of B-type natriuretic peptide (BNP)?
a) Levels >= 100pg/mL are associated with the early stage of the acute coronary syndrome
b) A positive test indicates prior myocardial damage caused by acute MI that occurred within the last 3 months
c) A normal test result helps rule out congestive heart failure in persons with symptoms associated with coronary insufficiency
d) A level above 100 pg/mL supports a diagnosis of unstable angina
c) A normal test result helps rule out congestive heart failure in persons with symptoms associated with coronary insufficiency
At a cutoff of <100 pg/mL, the BNP test is effective in ruling out CHF. In addition, persons with ischemia who have an increased BNP are at greater risk for MI.
What is the blood pH when the partial pressure of carbon dioxide (PCO2) is 60 mmHg and the bicarbonate level is 18 mmol/L?
a) 6.89
b) 7.00
c) 7.10
d) 7.30
c) 7.10
pH = 6.1 + log18(0.03x60) = 6.1 + log18/1.8
pH = 6.1 + log10 = 6.1 + 1
= 7.10
In an nonmyocardial as opposed to a myocardial cause of an increased serum or plasma CK-MB, which would be expected?
a) An increase in CK-MB that is persistent
b) An increase in the percentage of CK-MB as well as the concentration
c) The presence of increased troponin I
d) A more modest increase in total CK than in CK-MB
a) An increase in CK-MB that is persistent
In some noncardiac causes of elevated plasma CK-MB such as muscular dystrophy, there is a persistent elevation of both total CK and CK-MB. TnI (and TnT) are cardiac-specific markers.
Which would be consistent with partially compensated respiratory acidosis?
a) pH increased; PCO2 increased; Bicarbonate increased
b) pH increased, PCO2 decreased; Bicarbonate decreased
c) pH decreased, PCO2 decreased; Bicarbonate decreased
d) pH decreased, PCO2 increased; Bicarbonate increased
d) pH decreased, PCO2 increased; Bicarbonate increased
Bicarbonate is retained in partially compensated respiratory acidosis, helping to compensate for the retention of PCO2. The compensatory component always moves in the same direction.
In diabetes insipidus, the serum osmo is _____ and the urine osmo is _____.
a) decreased, increased
b) increased, decreased
c) decreased, decreased
d) increased, increased
b) increased, decreased
Diabetes insipidus: Body produces too much urine and isn't able to properly retain water. Serum Na is increased due to excess free water losses. Decreased ADH.
Which set of the following laboratory results is most likely from a patient who has suffered an acute MI? Reference intervals are below.
a) Total CK = 760 U/L, CK-MB = 16 μg/L, CK index = 2.1%
b) Total CK = 170 U/L, CK-MB = 14 μg/L, CK index = 8.2%
c) Total CK = 160 U/L, CK-MB 4 μg/L, CK Index = 2.5%
d) Total CK = 80 U/L, CK-MB 2 μg/L, CK Index = 2.5%
Normal Ranges: Total CK = 10-110 U/L, CK-MB = 1-6 μg/L, CK Index = 1-2.5%
b) Total CK = 170 U/L, CK-MB = 14 μg/L, CK index = 8.2%
C and D can be excluded because CK-MB is not increased. A and B have CK-MB levels above the URL; however, patent A has CK index under 2.5% and five- to tenfold elevation of total CK. These results indicate release of a small amount of CK-MB from skeletal muscle rather than from cardiac muscle.
Which set of results is consistent uncompensated metabolic acidosis?
a) pH= 7.34; HCO3-= 18mmol/L; PCO2= 32mmHg
b) pH= 7.25; HCO3-= 15mmol/L; PCO2= 35mmHg
c) pH= 7.30; HCO3-= 16mmol/L; PCO2= 28mmHg
d) pH= 7.45; HCO3-= 22mmol/L; PCO2= 40mmHg
b) pH= 7.25; HCO3-= 15mmol/L; PCO2= 35mmHg
Metabolic acidosis is caused by bicarbonate deficit. If uncompensated, the respiratory system is not excreting CO2 at an increased rate; pH and bicarbonate are low, but PCO2 is normal.
What is the typical time course for plasma myoglobin following an acute MI?
a) Abnormal before 1 hour; peaks within 3 hours; returns to normal in 8 hours
b) Abnormal before 3 hour; peaks within 6 hours; returns to normal in 18 hours
c) Abnormal before 3 hour; peaks within 12 hours; returns to normal in 36 hours
d) Abnormal before 6 hour; peaks within 24 hours; returns to normal in 72 hours
c) Abnormal before 3 hour; peaks within 12 hours; returns to normal in 36 hours
After acute MI, myoglobin usually rises above the cutoff within 1-3 hours, peaks within 8-12 hours, and returns to normal within 36 hours. Since myoglobin is the first marker to become normal after an acute MI, it should measured on admission and, if negative, measured again 2-4 hours later. If both samples are below the cutoff, the probability of an occurrence of an acute MI is low.