A nurse is collecting data for a client who experienced a myocardial infarction prior to a cardiac arrest. Which of the following laboratory tests will identify early injury to the cardiac muscle?
Creatine kinase-myocardial band (CK-MB) test
Troponin T test
Brain natriuretic peptide (BNP) test
Creatine kinase (CK) test
The Correct Answer is B
A. Creatine kinase-myocardial band (CK-MB) test: While CK-MB is also a marker of myocardial injury, it is less specific than troponin and can be elevated in other conditions, such as muscle injury.
B. Troponin T test. The Troponin T test is highly specific and sensitive for myocardial injury and is considered the gold standard for diagnosing a myocardial infarction. Troponin levels rise within hours of cardiac muscle injury and remain elevated for days, providing an early and reliable indicator of cardiac muscle damage.
C. Brain natriuretic peptide (BNP) test. BNP levels are used to assess heart failure and do not indicate acute cardiac muscle injury.
D. Creatine kinase (CK) test. CK measures overall muscle injury, not specific to cardiac muscle.
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Correct Answer is B
Explanation
A. Bounding peripheral pulses: Hypokalemia typically causes weak, thready pulses rather than bounding ones.
B. Decreased deep-tendon reflexes: Hypokalemia can cause muscle weakness and decreased deep-tendon reflexes due to impaired neuromuscular function.
C. Hyperactive bowel sounds: Hypokalemia generally causes decreased or hypoactive bowel sounds due to slowed smooth muscle contraction.
D. Restlessness: Restlessness is not a typical sign of hypokalemia; hypokalemia more commonly causes weakness, lethargy, or fatigue.
Correct Answer is D
Explanation
A. Creatinine phosphokinase (CPK): CPK levels peak within 24 hours after an MI and return to normal within 2-3 days.
B. Myoglobin: Myoglobin rises within hours but returns to normal within 24 hours after MI.
C. Creatinine kinase-MB (CK-MB): CK-MB peaks 12-24 hours post-MI and returns to baseline within 2-3 days.
D. Troponin T: Troponin T remains elevated for up to 10-14 days after an MI, providing long-term evidence of myocardial injury.