Final answer:
The initial dose of atropine in symptomatic bradycardia with a HR of 42 bpm and BP of 80/60 is 0.5 mg IV. Additional doses of 0.5 mg may be given up to a total of 3 mg, with continuous monitoring.
Step-by-step explanation:
The initial dose of atropine for a patient exhibiting symptomatic bradycardia with a heart rate (HR) of 42 beats per minute (bpm), who is diaphoretic and hypotensive with a blood pressure (BP) of 80/60, would be 0.5 milligrams (mg) administered intravenously. If there is no response, additional doses may be given every 3-5 minutes, up to a total of 3 mg. It is essential to monitor the patient continuously for vital signs, ECG changes, and symptom relief.
Atropine acts as an antagonist to muscarinic acetylcholine receptors, thereby inhibiting parasympathetic stimulation on the heart. This results in an increase in heart rate and can improve the symptoms related to bradycardia, such as dizziness, fatigue, and hypotension. The goal of atropine administration is to elevate the HR to a faster rate that can adequately maintain blood flow to vital organs. In general, for most individuals, symptoms diminish as the HR is raised above 50 bpm, and significant relief is observed as it approaches normal sinus rhythm, within the range of 60-100 bpm.