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Cardiac arrhythmias may arise spontaneously, or they may be associated with myocardial ischemia, respiratory depression, metabolic disorders, or other physiological derangements. Some anesthetic agents can cause or contribute to arrhythmias, particularly in susceptible individuals. Arrhythmias may be divided based on rate into tachyarrhythmias and bradyarrhythmias, or based on location of origin – supraventricular ectopic rhythm generation versus ventricular arrhythmias. Some cardiac rhythm abnormalities such as premature ventricular contractions and premature atrial contractions occur spontaneously in an otherwise normal population and require no intervention. Likewise, certain instances of tachycardia (mild, associated with anxiety) and bradycardia (due to chronic treatment with beta‐blockers, or in a competitive athlete) may be within acceptable limits. Any arrhythmia that is symptomatic, that carries a risk of conversion to a more dangerous cardiac rhythm, or that is accompanied by hemodynamic instability should be promptly addressed, however. If the arrhythmia is attributable to an underlying physiological disturbance, efforts should be made to treat the underlying condition. Otherwise, the management strategies for cardiac arrhythmias include pharmacological interventions or cardioversion/defibrillation.

Tachycardia due to stress, anxiety, or pain usually responds to a deepening of anesthesia and additional analgesia. The administration of a beta‐adrenergic blocking medication can be considered for refractory cases. Selective beta‐1 medications are preferred so as to avoid undesirable bronchoconstriction. Esmolol is a beta blocker with a fast onset and short acting duration. Metoprolol is another beta‐1‐selective medication with a longer acting duration. Both are available for IV use and may be titrated to effect. In general, beta blockers are best avoided in patients with low cardiac output states such as acute MI or acute exacerbation of congestive heart failure due to negative inotropic effects. When tachycardia is secondary to hypotension, hypovolemia, or fever, it is preferable to treat the underlying physiological derangement.

For cases of paroxysmal supraventricular tachycardia, vagal maneuvers may be attempted first. These include ice packs applied to the face or Valsalva maneuver. Pharmacological intervention involves the medication adenosine. Supraventricular tachycardias that do not respond to drug therapy or wide complex tachycardia (ventricular tachycardia) should be treated with synchronized/unsynchronized cardioversion (electric shock). Cardioversion is also preferred for tachycardia associated with hemodynamic instability. Cardiac rhythms associated with cardiac arrest, i.e., ventricular fibrillation or pulseless electrical activity, should be treated according to the ACLS protocols.

Bradycardia, defined as a heart rate <60 bpm, may occur in sinus rhythm (sinus bradycardia) or as a result of heart block (atrial–ventricular dissociation). Any new onset of heart block is cause for evaluation by a specialist. Chronic heart block can be a stable condition in patients with cardiac pacemakers. Sinus bradycardia during ambulatory anesthesia can be a sign of myocardial depression and is cause for concern. It may be treated with atropine or glycopyrrolate (both vagolytics), or with sympathomimetic drugs such as ephedrine or epinephrine.