During surgery, there is an increased potential for arrhythmias when catecholamines are given with:
A. halothane (Fluothane)
B. digoxin (Lanoxin)
C. bupivacaine (Marcaine)
D. lidocaine (Xylocaine)
Correct Answer: A. halothane (Fluothane)
Arrhythmias are a result of an interaction that can occur with halothane and catecholamines. Halothane is a clear, heavy, and colorless liquid with a sweet and non-irritating odor. Halothane’s structure is that of an alkane. It has primarily been used clinically as an inhalational anesthetic. Cardiorespiratory instability (i.e., hypotension, bradycardia), sensitizing the myocardium to catecholamine-induced arrhythmias, and mild liver dysfunction are relatively common side effects of halothane. Arrhythmias are especially common in neonates and children after the administration of halothane, particularly bradyarrhythmias. Other choices do not interact with halothane to cause arrhythmias.
Option B: Digoxin toxicity is clinically relevant as it can lead to fatal cardiac arrhythmias. The estimated frequency is at about 0.8 to 4% of patients on steady digoxin therapy. The rate of toxicity increases as serum digoxin concentration reaches over 2.0 ng/ml. However, toxicity can also occur at lower levels, especially in the setting of other risk factors such as low body weight, advanced age, decreased renal function, and hypokalemia.
Option C: Rarely, patients can exhibit toxicity to bupivacaine in doses much lower than the suggested upper limits of dosing. This toxicity appears to be due to a rare condition related to l-carnitine deficiency. Patients affected may exhibit cardiac toxicity at doses as low as 1.1 mg kg of bupivacaine injected cutaneously. Case reports exist describing these cases of low dose toxicity in patients later discovered to be deficient in l-carnitine.
Option D: Signs and symptoms of mild toxicity become apparent at plasma levels greater than 5 mcg/mL, beginning with slurred speech, tinnitus, circumoral paresthesia, and feeling faint. Above 10 mcg/mL, the patient may experience seizures or loss of consciousness. The myocardium and central nervous system are further depressed at 15 mcg/mL, progressing to cardiac arrhythmias, respiratory arrest, and cardiac arrest above 20 mcg/mL.