USMLE/COMLEX 2 - Hypertension Pathophysiology

Here are key facts for USMLE Step 2 CK & COMLEX-USA Level 2 from the Blood Pressure Regulation and Hypertension tutorial, as well as points of interest at the end of this document that are not directly addressed in this tutorial but should help you prepare for the boards. See the tutorial notes for further details and relevant links.

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1. Mean arterial pressure is determined by cardiac output and total peripheral resistance. 2. Hypertension results from increased cardiac output and/or increased total peripheral resistance. 3. Cardiac output is the product of heart rate and stroke volume. 4. Stroke volume is determined by preload and contractility. 5. Blood volume contributes to preload via increased venous return. 1. Antidiuretic hormone (vasopressin):

• Vasoconstrictor
• Increases sodium and water retention
• Clinical relevance: implicated in volume-dependent hypertension

2. Aldosterone:

• Similar effects to ADH
• Clinical relevance: primary hyperaldosteronism as a cause of secondary hypertension

3. Angiotensin II:

• Direct effects: vasoconstriction and increased sodium/water retention
• Indirect effects: stimulates release of norepinephrine, ADH, and aldosterone
• Clinical relevance: multiple antihypertensive drug classes target this system

4. Norepinephrine:

• Increases heart rate, contractility, and vasoconstriction
• Clinical relevance: sympathetic hyperactivity in hypertension

1. Hypertensive urgency: Blood pressure >180/120 mmHg without end-organ damage 2. Hypertensive emergency: Blood pressure >180/120 mmHg WITH end-organ damage 3. Clinical presentation: Severe headache, confusion, visual impairment, chest pain, dyspnea, nausea/vomiting, anxiety, seizures 4. Management approach: Different based on presence/absence of end-organ damage

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1. Renin-Angiotensin-Aldosterone System (RAAS):

• Clinical significance: Primary target for antihypertensive medications
• Angiotensin II breaks down bradykinin (vasodilator)
• Therapeutic implication: ACE inhibitors both reduce angiotensin II and increase bradykinin

2. Kidney's Role in Hypertension:

• Sodium and water retention affects blood volume
• Clinical application: Salt-sensitive patients require dietary sodium restriction
• Therapeutic implication: Diuretics effective in volume-dependent hypertension

3. Vascular Remodeling:

• Hypertension produces damage leading to vascular changes
• Clinical significance: Elevated endothelin and reduced nitric oxide
• Therapeutic implication: Long-standing hypertension may be more resistant to treatment

4. Salt Sensitivity:

• Clinical relevance: Patients with salt-sensitive hypertension develop elevated BP with high sodium intake
• Therapeutic implication: Dietary modifications crucial for these patients

1. Aldosterone-secreting tumors:

• Mechanism: Increased blood volume and preload
• Clinical presentation: Hypertension with hypokalemia
• Diagnostic approach: Plasma aldosterone to renin ratio

2. Environmental and Genetic Factors:

• Multiple factors affect components of BP regulation
• Clinical application: Family history and lifestyle assessment essential in workup
• Therapeutic implication: Lifestyle modifications as foundation of treatment

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Below is information not explicitly contained within the tutorial but important for USMLE Step 2 CK & COMLEX Level 2. 1. Antihypertensive medication classes:

• ACE inhibitors: Target angiotensin II formation
• ARBs: Block angiotensin II receptor
• Diuretics: Reduce blood volume
• Calcium channel blockers: Induce vasodilation
• Beta-blockers: Reduce heart rate and contractility

2. Special population considerations:

• Pregnancy: Preeclampsia risk assessment and management
• Elderly: Risk of orthostatic hypotension with treatment
• Diabetes: Tighter BP goals and medication preferences

3. Prevention of complications:

• Left ventricular hypertrophy
• Stroke
• Chronic kidney disease
• Aortic dissection

1. Patient with salt-sensitive hypertension:

• Presentation: BP fluctuations with dietary sodium changes
• Approach: Low-sodium diet, diuretic therapy

2. Hypertensive emergency management:

• Initial assessment: Evaluate for end-organ damage
• Immediate approach: Gradual BP reduction to prevent cerebral hypoperfusion
• Medication selection based on presenting complication