A nurse is assessing a client suspected of having cardiac tamponade. Which of the following findings indicates the presence of pulsus paradoxus?

A. Creatine kinase (CK) test: While creatine kinase isoenzymes, including CK-MB, can be elevated following myocardial infarction (MI), they are not specific to cardiac muscle injury. CK is found in various tissues throughout the body, so elevated levels can also indicate damage to skeletal muscle or brain tissue, among other sources.

B. Creatine kinase-myocardial band (CK-MB) test: CK-MB is a cardiac-specific isoform of creatine kinase, and elevated levels can indicate myocardial injury, particularly in the context of an acute MI. However, troponin T is a more sensitive and specific marker for myocardial injury.

C. Brain natriuretic peptide (BNP) test: Brain natriuretic peptide is primarily used in the diagnosis and management of heart failure. While elevated BNP levels can indicate heart muscle strain or stress, they are not specific markers for acute myocardial infarction or early injury to the cardiac muscle.

D. Troponin T test: This is the correct answer. Troponin T is a highly specific marker for cardiac muscle injury. Elevated troponin levels can be detected within hours of myocardial infarction and persist for several days, making it an essential tool in the diagnosis of acute coronary syndromes, including myocardial infarction. Troponin T is considered one of the gold standard biomarkers for detecting early injury to the cardiac muscle.

Pulseless electrical activity (PEA) refers to a situation in which an electrocardiogram (ECG) shows electrical activity in the heart, but there is no effective mechanical activity and no palpable pulse. PEA can result from various underlying conditions that impair cardiac function or compromise circulation.

A. Hypertension: Hypertension, or high blood pressure, is not typically a direct cause of PEA. While uncontrolled hypertension can contribute to cardiovascular disease and increase the risk of cardiac events such as myocardial infarction, it is not a direct cause of PEA.

B. Hypovolemia: Hypovolemia, or low blood volume, is a common cause of PEA. Reduced circulating blood volume leads to decreased preload and inadequate filling of the heart chambers, impairing cardiac output. This can result in ineffective cardiac contractions and the development of PEA.

C. Hypoxia: Hypoxia, or inadequate oxygenation of tissues, is a significant cause of PEA. Insufficient oxygen delivery to the myocardium impairs cardiac function and can lead to ineffective cardiac contractions. Without adequate oxygenation, the heart is unable to generate sufficient mechanical force to maintain circulation, resulting in PEA.

D. Hyperkalemia: Hyperkalemia, or elevated levels of potassium in the blood, can cause PEA by disrupting cardiac electrical activity. Excessive potassium ions in the extracellular fluid alter the normal myocardial action potential, leading to cardiac conduction abnormalities and potential arrhythmias, including PEA.

E. Hypernatremia: Hypernatremia, or elevated levels of sodium in the blood, is not typically a direct cause of PEA. While severe hypernatremia can lead to neurological symptoms and dehydration, it does not directly impair cardiac electrical activity or mechanical function to the extent that it causes PEA.

F. Hyperthermia: Hyperthermia, or elevated body temperature, is not typically a direct cause of PEA. While extreme hyperthermia can lead to cardiovascular complications such as heat stroke, it is not a common cause of PEA unless it is associated with severe systemic metabolic derangements.