ADVANC<strong>IN</strong>G THE STANDARD OF CARE:Cardiovascular and Neurovascular EmergenciesSubarachnoid HemorrhageAneurysmal SAH is the one type of neurovascularemergency of which clinicians should absolutely treatelevated blood pressure. Patients with aneurysmalSAH, who do not receive definitive treatment for theiraneurysm, have a risk of rebleeding of 20% at 2 weeksand 30% at one month. 17 While there is little evidencethat uncontrolled blood pressure increases that risk,the potential is all too logical. Clearly, extremes ofblood pressure at admission (MAP> 130 or
<strong>HYPERTENSION</strong> <strong>MANAGEMENT</strong> <strong>IN</strong>ACUTE NEUROVASCULAR EMERGENCIESNicardipine has been shown to be as effective assodium nitroprusside in controlling blood pressure,but requires fewer dose titrations and does not increaseICP. It has therefore supplanted sodium nitroprussideas a treatment for acute neurovascular emergencies.Dosage is individualized based on the severity of thepatient’s hypertension and the goals for therapy. Forgradual reduction in blood pressure, initiate therapy5.0 mg/hr. If desired blood pressure reduction isnot achieved at this dose, the infusion rate may beincreased by 2.5 mg/hr every 15 minutes up to amaximum of 15.0 mg/hr, until desired blood pressurereduction is achieved. For more rapid blood pressurereduction, initiate therapy at 5.0 mg/hr then the infusionrate may be increased by 2.5 mg/hr every 5 minutesup to a maximum of 15.0 mg/hr, until desired bloodpressure reduction is achieved. Following achievementof the blood pressure goal, the infusion rate shouldbe decreased to 3 mg/hr. For maintenance, the rate ofinfusion should be adjusted as needed to achieve thedesired response.Nicardipine is contraindicated in patients withadvanced aortic stenosis because part of thetherapeutic effect of nicardipine is secondary toreduced afterload. Reduction of diastolic pressurein these patients may worsen rather than improvemyocardial oxygen balance. 20LabetalolLabetalol is an adrenergic receptor blocking agent thathas both selective α 1 - and nonselective β-adrenergicreceptor blocking actions in a single drug. In humans,the ratios of α- to β-blockade have been estimatedto be approximately 1:3 and 1:7 following oral andintravenous administration, respectively. Labetalolproduces dose-related falls in blood pressure withoutreflex tachycardia and without significant reductionin heart rate, presumably through a mixture of its α-blocking and β-blocking effects.For hypertensive emergencies labetalol is given aseither repeated intravenous boluses or as a continuousinfusion. For repeat bolus dosing, labetalol injectionshould begin with a 10-20 mg dose (which correspondsto 0.125-0.25 mg/kg for an 80-kg patient) by IVinjection over a 2-minute period. While much of thepackaging of the agent lists 20 mg as the initial dose,many clinicians begin with a 10 mg dose to ensuresafety of bolus therapy before proceeding to a 20mg dose. Immediately before the injection and at 5and 10 minutes after injection, supine blood pressureshould be measured to evaluate response. Additionalinjections of 40 or 80 mg can be given at 10-minuteintervals until a desired supine blood pressure isachieved or a total of 300 mg of labetalol has beeninjected. The maximum effect usually occurs within5 minutes after each injection. A continuous infusioncan also be given at 2 mg/min and titrated. The halflifeof labetalol is 5 to 8 hours. In the ED, initial bolustherapy followed by infusion may be required.Labetalol is contraindicated in bronchial asthma,overt cardiac failure, greater than first degree heartblock, cardiogenic shock, severe bradycardia, andother conditions associated with severe and prolongedhypotension. 21EsmololEsmolol is a b1-selective (cardioselective) adrenergicreceptor blocking agent with rapid onset, a veryshort duration of action, and no significant intrinsicsympathomimetic or membrane stabilizing activityat therapeutic dosages. Its elimination half-life afterintravenous infusion is approximately 9 minutes.Esmolol inhibits the b1 receptors located chieflyin cardiac muscle, but this preferential effect is notabsolute and at higher doses it begins to inhibit b2receptors located chiefly in the bronchial and vascularmusculature.An initial loading dose of 0.5 milligrams/kg (500micrograms/kg) infused over a minute durationfollowed by a maintenance infusion of 0.05milligrams/kg/min (50 micrograms/kg/min) for thenext 4 minutes is recommended. After the 4 minutesof initial maintenance infusion (total treatmentw w w . e m c r e g . o r g67
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