blood pressure management in acute stroke pat melanson, md mcgill university
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BLOOD PRESSURE MANAGEMENT IN ACUTE
STROKE
Pat Melanson, MD
McGill University
“Brain Attack”
• Paradigm shift - End of nihilism
• Early effective interventions
• Time-sensitive disease
• Chain of recovery
• Stroke units and stroke centers
Stroke Protocols
• Aspiration pneumonia, UTI’s• DVT prophylaxis• Glucose control• Fever control• BP management–avoidance of overtreatment
Cases
• Ischemic CVA, BP 225/105 (145)• Hemorrhagic CVA, BP 215 /110 (145)
–Would you actively lower the BP?–What target or threshold level?–What drug ?–Which drugs should be avoided?
Lowering BP in Acute Stroke: Pros
• Chronic hypertension
• Rebleed/ increase hematoma size
• Cerebral edema, Raised ICP
• Hemorrhagic transformation–Decrease bleeding with t-PA
Lowering BP in Acute Stroke: Cons
• Acute hypertension is self-limited
• RISK OF ISCHEMIA
–Reflex response to maintain CBF
– Ischemic penumbra
–Shift in autoregulation curve
–More sensitive to BP decreases
Cerebral Blood Flow• CBF = CPP / CVR
• CPP = MAP - ICP
• MAP = DBP + 1/3 PP
• Cerebral autoregulation– normal between 50 - 150
– 70/40 to 200/130
50 150
Cerebral Autoregulation
CBF50
ml/100g/min
MAP
20
Cerebral Autoregulation
• MAP below lower limit
– hypoperfusion with ischemia
• MAP above upper limit
– “breakthrough” vasodilation
– Segmental pseudospasm (“sausage-string”)
– fluid extravasation
Cerebral Autoregulation• Shift to right
–Chronic hypertensives
– ICH, SAH, Ischemic infarct
– Trauma
–Cerebral edema
–Age, atherosclerosis
• Some hypertensives suffer decrease CBF at MAP higher than 120 (160/100)
How far can BP be safely lowered?
• Lower limit usually 25% below MAP
• 50% of chronic hypertensives reached lower autoregulation limit with 11 to 20% reduction in MAP
• 50% had lower limit above usual mean– Kanaeko et al; J Cereb Blood Flow Metab 3:S51,1983
• Most ischemic complications develop with reductions greater than 20 - 30 %
Initial Lowering of BP : Therapeutic Guidelines
• Do not lower BP more than 15 % over the first 1 to 2 hours unless necessary to protect other organs
• Decreasing to DBP of 110 or patients “normal” levels may not be safe
• Further reductions should be very gradual ( days)
• Follow neuro status closely
Pharmacologic Therapy
Drugs Best Avoided• Direct-acting cerebral vasodilators– adversely affect CBF– potential to increase ICP– shift autoregulation curve to the right
• Nitroglycerine• Nitroprusside• Hydralazine• Calcium Channel Blockers
Nifedipine• Peripheral, cerebral and coronary
arteriolar vasodilation
• Rapid onset of antihypertensive effect – 5-20 minute onset
– peak effect in 30-60 min
– duration 4-5 hr
• Potential severe hypotension
• Several case reports of cerebral or myocardial ischemia after rapid decrease
Sublingual Nifedipine
• “Should a Moratorium be Placed on Sublingual Nifedipine capsules given for hypertensive emergencies and pseudoemergencies?”
– Grossman, Messerli, Grodzicki, Kowey– JAMA, 276 : 1328 - 1331,1996
Recommended Antihypertensives
• Beta-blockers
• Alpha-blockers
• ACE inhibitors
• Clonidine
Labetalol
• Combined , adrenergic blockade
• Usual contraindications to -blockade
• Rapidly effective when given IV;
• Onset < 5 min, peak 5-10 min, duration 2-6 hr (sometimes longer)
• 5 - 10 mg iv q10 minutes
ACE inhibitors• IV enalaprilat, oral captopril potentially
useful for acute BP reduction
• Difficult to titrate (sometimes ineffective,sometimes excessive BP )
• Positive effects on cerebral autoreg.
• Captopril 12.5 mg S/L
Recommendations
• MAP of 140 - 145 (220/120)
• Max decrease of 15 % MAP
• Avoid direct acting vasodilators
• Avoid sublingual nifedipine
• Labetalol, Captopril
• Cautious reduction with frequent neurologic exams
Pharmacological Elevation of BP in Acute Stroke
• Pharmacological elevation of blood pressure in acute stroke: Clinical effects and safety. Rordorf, Stroke 1997; 28:2133– Retrospective review of 63 patients– Ischemic stroke with normal BP– 30 received phenylephrine (alpha-agonist)– 10 demonstrated a BP threshold
• Improved outcome
Recommendations
• MAP of 140 - 145 ( 220/120)
• Avoid direct acting vasodilators
• Avoid sublingual nifedipine
• Alpha or beta blockers, ACEI
• Cautious reduction with frequent neurologic exams
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