The nurse evaluates the effects of warfarin by monitoring what lab test?

Choice A rationale

Assessing pulses and blood pressure is crucial before administering an antiarrhythmic agent because these drugs can affect heart rate and blood pressure, requiring close monitoring to prevent adverse effects.

Choice B rationale

While assessing breath sounds is important in overall patient care, it is not the priority before administering antiarrhythmic agents as these drugs primarily affect the cardiovascular system.

Choice C rationale

Assessing mental status is important in patient care, but it is not the priority before administering an antiarrhythmic agent, as these medications primarily influence cardiovascular parameters.

Choice D rationale

Assessing urine output is vital for monitoring kidney function and fluid balance, but it is not the priority before administering an antiarrhythmic agent, which mainly affects heart rhythm and blood pressure.

Choice A rationale

Magnesium plays a role in muscle relaxation but is not primarily responsible for muscle contraction. It helps in stabilizing the muscle membrane by acting as a natural calcium blocker. Deficiency in magnesium can lead to muscle cramps and spasms, but it does not directly cause muscle contraction and relaxation processes.

Choice B rationale

Chloride is an essential electrolyte involved in maintaining fluid balance and acid-base balance, but it does not directly influence muscle contraction and relaxation. It works in conjunction with sodium to regulate osmotic pressure and acid-base balance.

Choice C rationale

Calcium is crucial for muscle contraction. It is released from the sarcoplasmic reticulum within the muscle cells and binds to troponin, causing a conformational change that allows actin and myosin to interact and generate contraction. During relaxation, calcium ions are pumped back into the sarcoplasmic reticulum.

Choice D rationale

Hydrogen ions are involved in pH balance and acid-base regulation but do not directly affect muscle contraction and relaxation. Excess hydrogen ions (acidosis) can impair muscle function, but they are not the primary factor in muscle contraction processes.