Thursday, February 28, 2013

Bringing the OR to the ER: Administration of Nicardipine as an IV Bolus

I made a comment once on Twitter that if I ever became a physician, the specialty I would go into would be anesthesiology. Why? Anesthesiologists have time and again done such innovative things with medications in the operating room that have made their way into the practice of emergency medicine. One example that comes to mind is the use of intravenous lipid emulsion therapy for the treatment of various toxicological emergencies. Another instance is the use of push-dose vasopressors for the short-term management of hypotension or as a bridge to vasopressor infusion therapy and/or while central line access is obtained.

In an earlier blog post, I discussed my experience with nicardipine for the management of blood pressure in the setting of neurological emergencies. Many of the studies that I have found regarding this have looked at using a continuous IV infusion of nicardipine that is titrated based on the observed blood pressure response.

So you can imagine my reaction when I discovered that the use of nicardipine as an IV bolus for the short-term management of hypertension originated from anesthesia. I thought to myself, “Those anesthesiologists have gone and done it again!” But you are probably thinking to yourself, “Wait…administration of nicardipine as an IV bolus??”

Many of the studies that have evaluated the use of bolus dosing for IV nicardipine were conducted in the perioperative setting. Bolus dosing of IV nicardipine has been used for anesthetized patients undergoing surgical procedures to control and maintain intraoperative and postoperative hemodynamic stability. Another common use of bolus dosing of IV nicardipine in the OR is for the attenuation of the increase in blood pressure associated with laryngoscopy and endotracheal intubation for patients who have undergone anesthetic induction. A great review article here highlights the results of some of these studies.

The doses that were studied in these patient populations varied between weight-based dosing (20 to 80 mcg/kg) and fixed dosing (0.25, 0.5, 1, and 2 mg). One study demonstrated a dose-dependent response associated with the use of bolus dosing of IV nicardipine and the effects on mean arterial pressure, systolic blood pressure, and diastolic blood pressure. The mean time for maximum response varied from 66 seconds to 101 seconds, depending on the dose administered.

A theoretical benefit that I can envision with the use of bolus dosing of IV nicardipine is the rapid control of blood pressure while the effects of the continuous infusion kick in. One situation where it may prove to be of some potential value is in the management of hypertension in the setting of neurological emergencies. Another setting is in the management of acute aortic dissection in patients whose blood pressure is not controlled with the use of β-blocker (i.e. esmolol) monotherapy.

Unfortunately, there have not been any trials conducted that have evaluated the use of bolus dosing of IV nicardipine in patients who are not going elective procedures, and so the applicability for patients in the emergency department is relatively limited without evidence from case studies or randomized, controlled clinical trials. Maybe one day, such studies will be performed for the acute control of blood pressure in these and other situations that are encountered in the emergency department setting. Perhaps like intravenous lipid emulsion therapy and push-dose vasopressors, bolus dosing of IV nicardipine will make its way into the practice of emergency medicine and will be heralded as one of those therapies where clinicians will wonder, “How come we never thought about using this before?” Time will tell.