Hypertensive Crisis

1) Overview of Hypertensive Crises:

a. Hypertensive urgency: various definitions of exact BP, but usually > 180 systolic or > 120 diastolic, without any symptoms of end-organ damage.  (Headache and blurry vision alone generally do NOT count as end-organ damage)
b. Hypertensive emergency: same, but symptoms of end organ damage:

• Neuro: Hypertensive encephalopathy and PRES (posterior reversible encephalopathy syndrome), Stroke: Ischemic, Intraparenchymal bleed, and Subarachnoid bleed, Papilledema and retinal hemorrhages
• CV: Acute MI/ACS, Acute LV dysfunction/flash pulmonary edema, Acute aortic dissection
• Renal: Acute renal failure, hematuria, proteinuria
• Heme: Microangiopathic hemolytic anemia  - thought to be due to vascular injury (endothelial damage -> fibrinoid necrosis in arterioles/capillaries) causing shearing of the RBCs over the fibrin strands (thanks to Meera for looking this up!)

2) Etiologies of hypertensive crises:  always think, why is this patient so hypertensive?

• Med noncompliance in baseline hypertensive pts - probably the most common cause, especially if pts are on drugs like clonidine, metoprolol that can have rebound effect when stopped abruptly
• Severe anxiety - although typically still in baseline hypertensive patients
• Drugs - Cocaine, Methamphetamines.
• Renovascular disease, e.g. renal artery stenosis
• Endocrine causes - Pheochromocytoma

3) Management of hypertensive crises

• HTN urgency - goal to reduce BP to <160/100 gradually, over days, using PO meds
• HTN emergency - reduce BP over minutes to hours.  Typically use IV drips for rapid effect and titration. Do NOT aggressively reduce MAP by more than 25% acutely, or can precipitate ischemic crises (Stroke, MI).  EXCEPTION to this is Aortic dissection, where goal is to rapidly reduce BP to ~100-120s, using IV beta blockers (i.e. labetolol, esmolol).  Also, sometimes with intraparenchymal cerebral bleeds due to HTN, may want to be aggressive about BP control as well.

Intravenous Drips for Hypertensive Emergency

• Nitroprusside: both an arteriolar and venodilator, acts via nitric oxide and stimulation of cGMP pathway, leading to vasodilation.  Drug of choice for most hypertensive crises, given high efficacy, short half-life and easily titratable.  Main concern is cyanide toxicity (altered mental status, lactic acidosis, clinical deterioration) esp with renal insufficiency.  Typically needs arterial-line for close BP monitoring.
• Nitroglycerin: venodilator > arteriolar dilator.  Does not cause cyanide toxicity, unlike nitroprusside.  Main problems are headache, also concern for increased ICP.  Often, DOC in pts with hypertension and coronary ischemia, also good for CHF due to reduction in preload.
• Esmolol - cardio-selective beta blocker, can be given as IV bolus or as continuous drip.  May be drug of choice for acute aortic dissections (to decrease shear stress)
• Labetalol - both a beta and alpha blocker, can be given as IV bolus or as continuous drip. 
• Nicardipine - calcium channel blocker that can be given as IV drip.  Often used with HTN and subarachnoid bleeds (to decrease vasospasm).

(Chanu Rhee MD, 9/9/10)