Calcium entry blockers: Uses and implications for anesthesiologists
The Ca++ entry blockers are valuable new drugs in the treatment of many cardiovascular diseases. Because of the prevalence of these diseases, anesthesiologists will anesthetize many patients maintained on Ca++ antagonists and will wish to administer them to some patients under their care. Verapamil and nifedipine are available for use in the United States. Verapamil is useful for the treatment of supraventricular arrhythmias, whereas nifedipine and verapamil are indicated in the treatment of coronary vasospasm. There is no good information regarding whether or not the drugs need to be discontinued for a specific interval before anesthesia. Our clinical experience with both compounds is that they may be continued safely right up to the morning of surgery. Both nifedipine and verapamil are potent vasodilators and must be administered with caution during anesthesia and in the perioperative period, especially in patients with impaired ventricular function and/or hypovolemia. Additionally, verapamil may produce varying degrees of A-V block and must be given very carefully in patients anesthetized with enflurane, isoflurane, and halothane, in patients with A-V nodal block, or in patients maintained on beta-adrenergic blocking drugs. There is little experience to guide the anesthesiologist in the perioperative use of these drugs, but their potential uses are great. The calcium channel blockers are an important addition to our formulary, with many of their uses in anesthesiology yet to be confirmed or discovered.