A nurse is caring for a client who has myasthenia gravis. The nurse should recognize that this disease is caused by which of the following types of hypersensitivities?

Hypokalemia is a low serum potassium level, usually below 3.5 mEq/L. It can be caused by diuretics that increase potassium excretion, such as thiazides or loop diuretics. Potassium is essential for normal muscle and nerve function, and hypokalemia can impair cardiac, skeletal, and smooth muscle activity. Symptoms of hypokalemia include fatigue, weakness, muscle cramps, arrhythmias, constipation, and hyporeflexia.

1. Dyspnea is difficulty or labored breathing that can be caused by various respiratory or cardiac conditions, such as asthma, pneumonia, pulmonary edema, or heart failure. It is not a specific sign of hypokalemia, although severe hypokalemia can affect respiratory muscle function and cause respiratory failure.
2. Oliguria is a reduced urine output, usually less than 400 mL per day or 30 mL per hour. It can be caused by various renal or fluid balance disorders, such as acute kidney injury, dehydration, or shock. It is not a specific sign of hypokalemia, although severe hypokalemia can impair renal function and cause renal failure.
3. Pitting edema is a swelling of the tissues that leaves an indentation when pressed with a finger. It can be caused by various fluid retention disorders, such as heart failure, liver cirrhosis, or nephrotic syndrome. It is not a specific sign of hypokalemia, although severe hypokalemia can affect fluid and electrolyte balance and cause edema.

The P wave is the first wave on the ECG strip and represents the electrical activity of the atria. It reflects the depolarization of the atrial myocardium, which is the process of changing the electrical charge of the cardiac cells from negative to positive, triggering a contraction. The P wave precedes the QRS complex, which represents ventricular depolarization, and the T wave, which represents ventricular repolarization.

The other options are not correct because:

a. Slow repolarization of ventricular Purkinje fibers. This statement is incorrect because it describes the U wave, which is a small and sometimes invisible wave that follows the T wave on the ECG strip. It reflects the repolarization of the ventricular Purkinje fibers, which are specialized cardiac cells that conduct electrical impulses to the ventricles. The U wave is more prominent in conditions that cause hypokalemia, such as diuretic use or vomiting.

c. Early ventricular repolarization. This statement is incorrect because it describes the ST segment, which is the flat line between the QRS complex and the T wave on the ECG strip. It reflects the early phase of ventricular repolarization, which is the process of restoring the electrical charge of the cardiac cells to negative after a contraction. The ST segment can be elevated or depressed in conditions that cause myocardial ischemia or injury, such as angina or myocardial infarction.

d. Ventricular depolarization. This statement is incorrect because it describes the QRS complex, which is the largest and most visible wave on the ECG strip. It reflects the depolarization of the ventricular myocardium, which triggers a ventricular contraction. The QRS complex follows the P wave and precedes the T wave on the ECG strip.