Pharmacological and Parenteral Therapies Q 9
The 6-month-old client with a ventral septal defect is receiving Digitalis for regulation of his heart rate. Which finding should be reported to the doctor?
A. Blood pressure of 126/80
B. Blood glucose of 110 mg/dL
C. Heart rate of 60 bpm
D. Respiratory rate of 30 per minute
Correct Answer: C. Heart rate of 60 bpm
A heart rate of 60 in the baby should be reported immediately. The dose should be held if the heart rate is below 100 bpm. Digoxin has vagomimetic effects on the AV node. By stimulating the parasympathetic nervous system, it slows electrical conduction in the atrioventricular node, therefore, decreases the heart rate. The rise in calcium levels leads to prolongation of phase 4, and phase 0 of the cardiac action potential thus increases the refractory period of the AV node. Slower conduction through the AV node carries a decreased ventricular response.
Option A: It increases the force of contraction of the heart by reversibly inhibiting the activity of the myocardial Na-K ATPase pump, an enzyme that controls the movement of ions into the heart. Digoxin induces an increase in intracellular sodium that will drive an influx of calcium in the heart and cause an increase in contractility. Cardiac output increases with a subsequent decrease in ventricular filling pressures.
Option B: Electrocardiogram changes seen with digoxin demonstrate a downsloping ST-segment depression, also known as a “reverse check” sign. The ST segments may appear “scooped” without abnormal Q waves or T wave inversions. Regular intake of digoxin results in changes such as a decreased QT interval, prolongation of the PR interval and T wave inversion or flattening. In the case of overdose, the patient should receive digoxin immune fab.
Option D: The prescriber needs to check levels with any recent change in medication. The kidneys excrete approximately 70% of digoxin in direct proportion to the patient’s glomerular filtration rate. The physician must request regular electrocardiograms and bloodwork to assess for renal function, and electrolytes require close monitoring.