![]() Electrocardiogram (ECG) should demonstrate a P wave preceding each QRS complex with a fixed PR interval. ![]() The rate is regular and rarely exceeds 160 beats/minute. Sinus tachycardia is a sinus node–driven heart rate greater than 100 beats/minute. ![]() In patients with intrinsic cardiac disease, treatment should proceed with atropine (0.5 mg IV), chronotropes (e.g., ephedrine, dopamine), or cardiac pacing.Glycopyrrolate (0.2 to 0.6 mg IV) or ephedrine (5 to 10 mg IV) may be given for hemodynamically stable bradycardia, the latter may be more appropriate for settings of brief surgical stimulation of the vagus. Atropine (0.5 mg IV) or low-dose epinephrine (10 to 50 μg IV) may be needed if the patient is hypotensive. Bradycardia due to increased vagal tone requires discontinuation of the provocative stimulus.Verify adequate oxygenation and ventilation.Increased vagal tone occurs with traction on the peritoneum or spermatic cord pressure on the globe via the oculocardiac reflex pressure near the brainstem during craniotomies for posterior fossa lesions direct pressure on the vagus nerve or carotid sinus during neck or intrathoracic surgery acute distension of the peritoneal cavity during laparoscopy centrally mediated vagal response from anxiety or pain (vasovagal reaction) and valsalva maneuvers.Medications such as succinylcholine (especially in young children via a direct cholinergic effect), anticholinesterases, β-adrenergic blockers, calcium channel blockers, digoxin, and synthetic narcotics (e.g., fentanyl and remifentanil).Intrinsic cardiac disease such as sick sinus syndrome or acute MI (particularly inferior wall MI).With very slow rates, atrial and ventricular ectopic escape beats or rhythms may occur. Unless there is severe underlying heart disease, hemodynamic changes are minimal. Sinus bradycardia is a sinus node–driven heart rate of less than 60 beats/minute.
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