Definition of Hypertensive Emergency
When seeing a patient with high BP, our experts recommend the following questions be used to differentiate true hypertensive emergencies from less urgent presentations:
- is there acute end-organ dysfunction and/or damage?
- is the dysfunction attributable to the elevated blood pressure (or will the elevated BP likely to make the dysfunction worse)?
- is altering the BP necessary to improve the organ dysfunction?
If the answer is “Yes”, this may be a hypertensive emergency. If not, these patients with high BP can be treated on an individualized basis, less aggressively.
The two categories of hypertensive emergencies
- Microvascular disorders (e.g. encephalopathy, pre-eclampsia/eclampsia), which are characterized by small vessel dysregulation, with endothelial damage and local inflammation
- “Macro” vascular disorders (i.e. CHF, aortic dissection, stroke, subarachnoid hemorrhage)
How does Hypertensive Encephalopathy present?
Suspect hypertensive encephalopathy when the patient has severe hypertension (usually >180/110), severe headache +/- vomiting.
Symptoms progress to confusion and altered mental status.
Retinopathy may be present, and seizures can occur.
The diagnosis is confirmed by normal CT plus cerebral function improvement with a decrease in the blood pressure.
The treatment goal is diastolic BP between 100-105 within 2-6 hours. Don’t lower the BP more than 20% in the first hour!
TREATING THE ELEVATED BLOOD PRESSURE
General principles for lowering BP rapidly in the ED
- Blood pressure should almost never be rapidly lowered (except in aortic dissection).
- Lower pressure by no more than 25%, to avoid ischemia in organs auto-regulated to higher BP.
- Therapies that correct the cause (e.g. phentolamine if the BP is elevated by catecholamines) will be most effective.
- Monitor the symptoms to determine whether the BP has been adequately lowered.
IV Drug choices for Hypertensive Emergencies
There are 3 major categories:
1. B-blockers: Labetolol is useful for most hypertensive emergencies. Give a 20mg slow IV push, then double the dose q10 min, up to 300mg. Be cautious in patients with asthma or COPD, and hepatic failure. Esmolol has quicker onset/offset, and may be safer in patients with mildly reactive airways.
2. Vasodilators: Nitroglycerin is great for ACS and pulmonary edema, but arterio-dilates only at high doses. Therefore for CHF patients, use higher doses to produce afterload reduction. Nitroprusside dilates both arteries and veins, but generates cyanide w prolonged use of high doses as it breaks down. Starting dose is 0.3–0.5mcg/min, and max dose is 2 mcg/min (less in renal pts). Hydralazine also dilates arteries, but has less predictable effects, and raises HR. Phentolamine (an a1 blocker) arterio-dilates to counteract catecholamines (i.e. cocaine, pheochromocytoma).
3. Calcium channel blockers: Dihydropyridine CCBs lower blood pressure by vasodilation (i.e. amlodipine, nifedipine, and nicardipine in USA). The phenylalkylamine class of CCBs mainly have negative inotropic and negative chronotropic effects (i.e. diltiazem and verapamil)
Subarachnoid Hemorrhage & Intracranial Hemorrhage Blood Pressure Management
Patients with subarachnoid hemorrhage (SAH) and intracranial hemorrhage (ICH) may rebleed if BP is too high, and may stroke if BP drops too rapidly.
Our experts recommend slow BP reduction only if necessary, and diligent correction of other metabolic disturbances (hyperglycemia, acidosis, fever, etc).
Should INTERACT 2 trial change practice for blood pressure management in subarachnoid hemorrhage?
While INTERACT 1 showed lowering BP slows hematoma growth, INTERACT 2 (full pdf) showed no benefit.
INTERACT 2 study suggested blood pressure may be safely reduced to systolic of 140, but no benefit was shown for re-bleeding.
Therefore, our experts suggest using AHA guidelines, (see below) which suggest at target systolic BP of 160.
If you decide to lower the BP, avoid nitroprusside, because it causes a relative decrease in cerebral perfusion pressure, due to a peripheral shunt effect.
Each patient should be approached individually.
Use labetolol or nifedipine, go slowly, and monitor closely.
Patients with ICH are at high risk for ischemia with BP reduction. The AHA guidelines divide patients into 3 groups:
- For SBP >200 or MAP >150 —consider lowering BP by IV infusion under close monitoring
- ICH with suspected raised ICP and high BP — get ICP monitoring first, before lowering BP
- SBP >180 or MAP >130 but no suspicion of high ICP — consider a slower, more modest BP reduction using IV medications
Does the choice of antihypertensive drug affect mortality and morbidity?
According to a Cochrane review of 15 RCTs (869 pts), there was no evidence that any class of IV antihypertensive drugs reduces mortality/morbidity, and no superiority was found among drug classes.
The CLUE trial has since shown advantages of nicardipine (less hypotension, bradycardia and AV blocking were observed) over labetolol for treatment of acute hypertension with end organ damage.
Drug of choice for hypertensive encephalopathy, aortic dissection & eclampsia?
Dr. Yaphe recommended labetolol for most situations (see above for dose).
Our experts recommend using the drug you are most familiar with, if the clinical context is appropriate.
How to manage patients with high BP and impaired renal function
If creatinine is high, check urine for proteinuria or active sediment, and the CBC and retinas for other indications of acute renal failure.
It may be impossible to tell if renal failure is acute if no recent bloodwork is available.
For these patients, our experts recommend very close followup with an internist, or hospital admission for further workup.
Use caution and an individualized approach.
Management of Elevated Blood Pressure in Congestive Heart Failure (CHF)
Start with high doses of nitroglycerine (see above for explanation) to achieve arterial dilatation.
Give up to 6 sublingual doses while IV drip is being prepared.
Non-invasive positive pressure (NIPPV) ventilation is also key to managing the pulmonary edema. see Episode 4 on Acute Congestive Heart Failure
Tips for a true Hypertensive Emergency – Aortic Dissection
BP can be very high, so verify and monitor by an arterial line in the right radial artery.
If target HR of 60 and systolic BP of
Use diltiazem if a B-blocker cannot be used.
Pearl: if aortic root is involved (check for a new murmur!) avoid B-blockers, as tamponade may be imminent.
*note nicardipine is an option in aortic dissection, however it is not available in Canada
Blood Pressure Management in Eclamplia & Pre-eclampsia
Pre-eclampsia is BP >160 /110, along with proteinuria (or low platelets, elevated LFT or Cr) or pulmonary, liver, cerebral or visual symptoms, in a patient >20 weeks pregnant.
Eclampsia is the same, but with seizures.
Labetolol is best for BP reduction along with Mg+, although hydralazine (5mg IV slow push over 1-2 minutes, repeat 5-10mg prn) can be used as a second line (*note that hydralazine has an unpredictable effect on blood pressure and should not be used as a first line medication)
Give 2g/hr IV Mg+ for seizure prophylaxis.
Goal is still only 25% BP reduction, and consult OB as delivery is the definitive Rx!
Now Test Your Knowledge