Final Answer:
In the scenario of a 1-year-old boy presenting with SVT (Supraventricular Tachycardia), the most effective vagal maneuver to treat this rhythm would be option C: Blow on the patient's face with a straw.
Step-by-step explanation:
In the context of treating SVT in a 1-year-old child, vagal maneuvers aim to stimulate the vagus nerve, which can help interrupt the abnormal electrical circuit causing the rapid heart rate. Option C, blowing on the patient's face with a straw (also known as the "infant Valsalva maneuver"), involves the application of mild, controlled air pressure on the face, creating a reflex response that stimulates the vagus nerve. This maneuver is considered safe and effective in pediatric patients, particularly infants, to alleviate SVT.
The action of blowing on the face with a straw induces a Valsalva-like effect by increasing intra-thoracic pressure and stimulating the vagus nerve. This stimulation can lead to a series of reflex responses, including transiently slowing down the heart rate by inhibiting the conduction of electrical impulses through the atrioventricular node. It is crucial to perform this maneuver gently and cautiously in pediatric patients to avoid causing distress or harm.
The other options listed—external ocular pressure (option A), applying ice to the face (option B), and performing carotid massage (option D)—are less suitable or potentially unsafe in pediatric patients, especially infants. They may involve increased risks of injury or are less likely to produce the desired vagal response without posing potential harm. Hence, the application of controlled blowing on the patient's face with a straw remains the most appropriate and effective vagal maneuver in managing SVT in a 1-year-old child.