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Ingrid Berling 29/09/2010 Epidemiology/pathophysiology Definitions/common Clinical evaluation Goals of treatment Pharmacotherapy Specific treatment types Prevalence of hypertension in Australia is 11% An estimated 30% of hypertensive patients are undiagnosed 29% of diagnosed patients are inadequately controlled Hypertensive crisis are uncommon, about 1-2% of the hypertensive population It is hypothesized that the final common pathway is a sudden increase in systemic vascular resistance (SVR) an increase in BP due to the action of circulating vasoconstrictors The ↑ BP damages the endothelium, leading to the release of local vasoconstrictors, such as endothelin, which cause further vasoconstriction Damage to the endothelium impairs auto-regulatory function. Further release of humoral vasoconstrictors perpetuates the “vicious circle.” JNC-VII, 2003; Normal: <120 over <80 Pre-hypertension: 120-139 over 80-89 Stage I: 140-159 over 90-99 Stage II: >160 over ≥ 100-109 Stage III: >180 over >110 JOINT NATIONAL COMMITTEE ON PREVENTION, DETECTION, EVALUATION AND TREATMENT OF HIGH BLOOD PRESSURE 1997/ 2003 A Hypertensive Emergency exists when acute elevation of blood pressure is associated with acute and ongoing organ damage to the kidneys, brain, heart, eyes or vascular system Does not specifically include BP levels, but Systolic >240mmHg Diastolic > 120 - 140mmHg REQUIRES IMMEDIATE BLOOD PRESSURE REDUCTION A Hypertensive Urgency exists when there is acute or chronic blood pressure elevation not associated with any observable acute organ damage This can be hard to distinguish on clinical evaluation alone. BP control over hours to days CVS o Acute MI o Acute LVF o Aortic dissection SAH RENAL o Glomerulonephritis o Collagen vascular disease PREGNANCY o PERIOPERATIVE o Coronary Bypass o Carotid endarterectomy o AAA stenting EXCESS CATECHOLAMINES o Phaeochromocytoma o withdrawal of anti-hypertensives o Toxicological • Interaction: MOAIs • Ingestions: Cocaine, cold medications • Glucocorticoid therapy CNS o Hypertensive encephalopathy o Stroke: Ischaemic, cerebral bleed, Pre-eclampsia and Eclampsia ENDOCRINE o Phaeochromocytoma crisis o thyrotoxicosis Hypertensive emergencies, look like EMERGENCIES. Therefore your approach is going to be simultaneous resuscitation and information gathering. Cardiovascular o Chest pain/syncope o Back pain o Dyspnoea Neurological o Seizures/altered MS o Focal weakness o Headache/visual disturbance Renal o Decreased UO o Bloody or frothy urine o Non-specific abdominal pain General o Malaise MI, unstable Angina, dissection Dissection Pulmonary Oedema, CHF Encephalopathy CVA/TIA Central nervous system compromise BP in both arms Fundoscopy examination Cardiovascular examination Neurological examination HTN Retinopathy (Keith-Wagner) Grade I o Mild arteriolar narrowing and sclerosis Grade II o Definite focal narrowing and AV nicking o Moderate to marked sclerosis of the arterioles Grade III o Retinal haemorrhages, exudates and cotton wool spots Grade IV o Severe grade III and papilledema FBC; schistocytes Electrolytes; Urea/creat Urinalysis; proteins B-hCG CXR ECG Head CT ? Urine drug screen Within 1-2 hrs. Lower MAP 20-25% Controlled environment Use IV titratible meds MAP = 1/3 SBP + 2/3 DBP Lancet, Hypertensive Emergencies, 2000; 356(9227):411-417 Maintains blood flow to vital organs, despite variations in systemic BP Classically maintained between MAP 60120mmHg However, in chronically hypertensive patients the curve is shifted to the right The average lower limit of auto-regulation is about 20-25% below the resting MAP. ↓ CO: inhibit contractility or decrease filling pressure ↓ filling pressure: Act on venous tone or blood volume ↓ PVR: relax smooth muscle of resistance vessels or interfere with systems that produce constriction (SNS) Vasodilators Adrenergic Inhibitors NITRATES Sodium nitroprusside (SNP) Nitroglcerin α+β BLOCKER Labetolol CALCIUM CHANNEL BLOCKERS Nicardipine β BLOCKER Esmolol ACE INHIBITOR Enlaprilat ARTERIAL VASODILATOR Hydralazine DOPAMINERGIC RECEPTOR AGONIST Fenoldopam DRUG DOSAGE (IV) ONSET/DUR ADV.EFF Nitroprusside 0.25-10 mcg/kg/min Instant/1-2 min Cyanide poisoning, Coronary steel Nitro-glycerine 5-100mcg/min 1-5 min/ 3-5min Flushing, headache, methaemoglobin Nicardipine (dihydropyridine) 5-15mg/hr. 5-10min/1-4hr Reflex tachycardia, flushing Hydralazine 10-20mg 5-15min/ 3-8hrs. Flushing, reflex tachycardia Enalapril 1.25-5mg IV q6hr 20-30min / 6hrs Hypotension, renal failure, hyperkalaemia DRUG DOSAGE ONSET/DUR Labetalol (α + β blocker) 20-80mg IV bolus 5-10min/3-6hrs every 10 mins, 2mg min IV infusion Heart block, Ortho-hypotension Avoid: heart failure, asthma Esmolol (β1 selective blocker) 200-500 mcg/kg/min for 4 mins, then 150300 mcg/kg/min Hypotension Avoid: heart failure, asthma 1-2 mins/ 10-20 min ADV.EFF DRUG DOSAGE ONSET/DUR ADV.EFF Clonidine 0.1-0.2 mg hr. Up to max 0.8mg in 24hrs. 30-60min/612hrs. Sedation Bradycardia dry mouth α2 agonist-centrally acting Results in a reduction in sympathetic outflow from the CNS The decrease in plasma norepinephrine is correlated directly with the hypotensive effect Reduction of BP is at the risk of causing hypo-perfusion of the peri-ischaemic area, resulting in an extension of the stroke. However, high BP can cause haemorrhagic transformation of infarct A Cochrane review examining 65 RCTs with 11,500 pts. Concluded that insufficient data exists to evaluate BP lowering post-stroke AHA guidelines: BP be reduced only if SBP>220 or DBP>120mmHg. (unless end-organ damage is due to BP) Labetalol and nitroprusside are agents of choice. Thrombolysis BP<185/110. (increased risk intracranial bleeding) No strong evidence for blood pressure management in intracerebral haemorrhage. In trials, nil adverse events from BP reduction of less than 20% Guidelines: decrease when MAP>130 or SBP>220. Labetalol and esmolol agents of choice. DO NOT use nitrates as they theoretically increase ICP Nimodipine decreases vasospasm that occurs due to chemical irritation of arteries by blood. Not recommended routinely due to high incidence of hypotension. Guidelines suggest SBP< 160 MAP <110 Labetalol and esmolol agents of choice. The aim is to reduce myocardial work and promote coronary blood flow, thus reducing ischaemia. IV GTN agent of choice (β-Blockers) Avoid hydralazine, as it increases myocardial oxygen demand. Usually associated with pulmonary oedema and diastolic/systolic dysfunction. Titrate until BP controlled and signs of heart failure alleviated. IV nitroprusside and GTN agents of choice. Symptoms: o Mental status change – somnolence, confusion, lethargy, stupor, coma, seizure o Headache – o Nausea and vomiting Hypertensive encephalopathy is a diagnosis of exclusion – thus, exclude the other possibilities! Only definitive criteria is a favourable response to BP reduction. However clinical improvement may lag behind BP improvement by hours to days Agent of choice – SNIP or labetalol Worsening of the dissection dependent on: o Level of elevated BP o Slope of the pulse wave. This increases the “shear force” on the dissection, leading to propagation of the dissection Goal is to reduce both the BP and the slope of the pulse wave! BP goal is SBP of 100-120 If patient presents with normal BP, still need to decrease the shear forces!! Labetalol IV SNIP + B-blocker!! o Do not use alone, as vasodilation causes reflex activation of SNS leading to enhanced ventricular contraction and increased aortic shear stress Do not use hydralazine, increased shear stress Labetalol traditional agent of choice, but experimental studies not positive for use. Nicardipine (or phentolamine in older texts) choice agent β-blocker - May be added to control tachycardia Not for use as sole agent – as may result in β-receptor antagonism and unopposed α adrenergic activity - ↑BP Benzodiazepines - May be helpful in cocaine/amphetamine Hypertensive encephalopathy Embolic CVA Hemorrhagic CVA SAH Nitroprusside, goal ~25 reduction Only if >220/120 or>185/110 for t-PA Labetalol for ~10-20% reduction Nimodipine 60 mg Q4hrs x 21 days Aortic dissection Acute LV failure Acute coronary syndrome Nitroprusside + Esmolol or Labetalol – SBP ~100 NTG, Lasix, MS04 for symptoms and ~1015% reduction NTG, MgS04, betablocker for symptom improvement Eclampsia and HELLP Goal DBP ~90; magnesium, hydralazine, labetalol, delivery! Catecholamine excess labetolol for ~25% reduction over several hours 3 quick questions A. Aortic dissection B. Thrombo-embolic CVA C. Hemorrhagic CVA D. Subarachnoid hemorrhage E. Hypertensive encephalopathy In all the other scenarios, such a precipitous drop in BP is likely to worsen outcome A. Aortic dissection – esmolol + SNIP B. Aortic dissection – labetalol C. Eclampsia – magnesium +/- hydralazine D. Pheochromocytoma – esmolol E. Acute LV failure - NTG Although use of Labetalol is controversial and possibly indicated, a pure beta-blocker like esmolol is grossly inappropriate in emergencies caused by catecholamine excess. A. Persistent BP >185/110 is a contraindication to thrombolytics B. Hemorrhagic CVAs tend to have higher BP than embolic C. Lowering the BP in the acute setting may worsen outcome D. If BP needs lowering in hemorrhagic CVA, SNIP is the agent of choice Nipride and other vasodilators are relatively contraindicated in hemorrhagic CVA as they may worsen ICP. Labetalol is the agent of choice IF BP needs to be lowered 1. Hoshide, S., et al., Hemodynamic cerebral infarction triggered by excessive blood pressure reduction in hypertensive emergencies. Journal of the American Geriatrics Society, 1998. 46(9): p. 1179-80. 2. Kitiyakara, C. and N.J. Guzman, Malignant hypertension and hypertensive emergencies. Journal of the American Society of Nephrology, 1998. 9(1): p. 133-42. 3. Epstein, M., Diagnosis and management of hypertensive emergencies. Clinical Cornerstone, 1999. 2(1): p. 41-54. 4. Kriegisteiner, S., et al., Hypertensive emergencies. Lancet, 2000. 356(9239): p. 1443. 5. Mansoor, G.A. and W.H. Frishman, Comprehensive management of hypertensive emergencies and urgencies. Heart Disease, 2002. 4(6): p. 358-71. 6. Vaughan, C.J. and N. Delanty, Hypertensive emergencies. Lancet, 2000. 356(9227): p. 411-7.
