Phenytoin is a neurologic and cardiac depressant and is one of the most dangerous medications we administer intraoperatively. For status epilepticus, the maximum rate of IV administration is 50 mg/min (for children, 1 to 3 mg/kg/min up to a max of 50 mg/min). Because we generally give the medication prophylactically in the operating room, it is recommended to administer phenytoin much more slowly in anesthetized patients (e.g., max. 10 to 20 mg/min). Elderly patients and patients with cardiovascular disease should also receive the medication more slowly. If phenytoin is given rapidly IV, asystole and cardiovascular collapse is possible, but more commonly hypotension, bradycardia, and cardiac dysrhythmias are seen. These effects may be related to the diluent (propylene glycol) and may be minimized by using fosphenytoin. The dose must also be adjusted in those with hypoalbuminemia and liver disease. It is advised that the medication be diluted in normal saline to a final concentration of 1 to 10 mg/mL and be administered with an infusion pump. Extravasation of this medication can cause severe soft tissue injury, and it is therefore recommended to inject phenytoin into
a large vein through a large-gauge IV catheter. Be sure to flush the line before and after administration with normal saline. This medication may be piggybacked, but there is a high potential for precipitation in the presence of other medications, so a 0.22-µm filter should be used.

Protamine is administered frequently in cardiac and vascular anesthesia to reverse the anticoagulant effects of heparin. Administer protamine slowly, no faster than 50 mg over 10 minutes. Severe hypotension, bradycardia, pulmonary hypertension, and an anaphylactic reaction can result if protamine is given by IV push. Patients at increased risk of severe reactions include diabetics taking insulin, patients with fish sensitivities, men who have undergone vasectomy, and patients who have been previously exposed to protamine. Dilution of the medication is not necessary.