Hypertensive Emergency

Today we discussed a patient with a hypertensive emergency. Here are some key points:
1) Classification of HTN:

• HTNsive urgency: SBP>180 or DBP>120 without end-organ damage 
• HTNsive emergency: Acute severe hypertension with end organ damage
• Malignant HTN: Hypertension with papilledema, renal involvement or microangiopathic hemolytic anemia.

2) End organ damage in HTN (head to toe)

• CNS: Encephalopathy (confusion), seizures, intracranial hemorrhage, SAH, and lacunar infarcts. Radiographic finding called PRES (posterior reversible encephalopathy syndrome) characterized by posterior symmetric white matter edema seen on CT
• Optic: retinal hemorrhages, exudates, papilledema and vision loss
• Cardiac: acute MI, aortic dissection, acute heart failure with pulmonary edema
• Renal: AKI, hypertensive nephrosclerosis (over time)
• Hematologic: microangiopathic hemolytic anemia

3) HTNsive retinopathy:

• Mild — Retinal arteriolar narrowing related to vasospasm, arteriolar wall thickening or opacification, and arteriovenous nicking, referred to as nipping
• Moderate — Hemorrhages, either flame or dot-shaped, cotton-wool spots, hard exudates, and microaneurysms
• Severe — Some or all of the above, plus optic disc edema. The presence of papilledema mandates rapid lowering of the blood pressure.

4) Secondary causes of HTN: 

• Endocrine: Cushing's syndrome, pheochromocytoma, aldosterone producing tumour (Conn's syndrome), acromegaly, hyper/hypothyroidism (these do not typically present as emergency/urgency)
• Anatomic: Coarctation of the aorta
• Renal: Renal artery stenosis (atherosclerosis, fibromuscular dysplasia), renal parenchymal disease, polycystic kidney disease
• Drugs: Cocaine, MAOI and tyramine containing foods, rapid withdrawal of clonidine/propanolol
• Pregnancy: Pre-eclampsia and HELLP syndrome

5) Treatment goals:

• Hypertensive emergency: Lower the BP by 25% of the MAP in the first 24 hrs or until symptoms resolve (i.e. patient stops seizing)
• Hypertensive urgency: Safer to lower the BP over days to weeks

6) Practical treatment and specific situations:

• If HTN emergency consider admission to ICU for arterial line and monitored lowering of BP
• Labetalol 10mg IV bolus followed by infusion (can repeat bolus if necessary)
• Nitroprosuside 0.25-0.5mcg/kg/min (beware of cyanide toxicity if prolonged treatment >48hrs)
• Hydralazine (can cause reflex tachycardia, so better if pt beta blocked prior to starting)
• Catecholamine driven HTN (Cocaine, MAOI, Pheo): use an alpha blocker (phentolamine 5-10mg IV Q5-15 min). Beware of giving beta-blockers as this can result in unopposed alpha and worsening HTN
• Pre-eclampsia: labetalol IV and MgSO4
• Alcohol withdrawal: Benzodiazepines
• Aortic dissection: Avoid using vasodilators initially (i.e. nitroprusside) as this can cause a reflex tachycardia and sheer stress on the aorta. Start with beta blocker and add nitroprusside if BP still not well controlled.