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Hypotension and Hypertension

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HYPERTENSION

Definition and Classification

Types

• No identifiable single cause
• Linked to genetics, diet (sodium), obesity, physical inactivity, stress, and aging

• Renovascular disease (renal artery stenosis)
• Chronic kidney disease (CKD)
• Primary aldosteronism
• Pheochromocytoma
• Obstructive sleep apnea
• Thyroid disorders
• Drug-induced (NSAIDs, oral contraceptives, stimulants)

Pathophysiology

• Increased sympathetic nervous system activity
• Renin-Angiotensin-Aldosterone System (RAAS) overactivation - angiotensin II causes vasoconstriction and sodium/water retention
• Endothelial dysfunction - reduced nitric oxide, increased endothelin
• Increased sodium retention by the kidneys (pressure-natriuresis curve shift)
• Structural arterial changes (arteriosclerosis, reduced compliance)

Risk Factors

• Age (risk doubles each decade after 55)
• Hypertension is a 2.5-fold risk factor for PAD in men and a 3.9-fold risk in women (Kannel and McGee, 1985)
• Obesity, diabetes, dyslipidemia, smoking
• Family history

Target Organ Damage (Complications)

Treatment

• DASH diet (low sodium, high potassium/fruits/vegetables)
• Weight loss, regular aerobic exercise
• Limit alcohol, smoking cessation

• Thiazide diuretics (e.g., chlorthalidone, hydrochlorothiazide)
• ACE inhibitors (e.g., lisinopril, ramipril) - preferred in CKD, diabetes, heart failure
• Angiotensin Receptor Blockers (ARBs) (e.g., losartan) - ACE inhibitor intolerant patients
• Calcium channel blockers (e.g., amlodipine) - particularly effective in elderly and Black patients
• Beta-blockers - preferred in heart failure with reduced EF, post-MI

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HYPOTENSION

Definition

• 458.0 - Orthostatic (postural) hypotension
• 458.1 - Chronic hypotension (permanent, idiopathic)
• 458.2 - Iatrogenic hypotension (due to medical treatment)
• 458.8/458.9 - Other/unspecified

Types and Causes

• Volume depletion (dehydration, hemorrhage, diuretics)
• Autonomic failure: Shy-Drager syndrome (multiple system atrophy), Riley-Day syndrome, diabetic autonomic neuropathy, Guillain-Barré, amyloidosis, AIDS, alcoholic neuropathy
• Drugs: antihypertensives, diuretics, nitrates, CCBs, alpha-blockers, L-dopa, tricyclic antidepressants, MAOIs, sildenafil, opiates, phenothiazines
• (Bradley and Daroff's Neurology in Clinical Practice)

• Most common cause of transient hypotension leading to syncope
• Affects 20-25% of young people
• Triggered by emotional stimuli, pain, prolonged standing, heat, venipuncture
• Features: pallor, diaphoresis, nausea, bradycardia

• Septic shock: hypotension + vasopressor requirement + lactate > 2 mmol/L (Sepsis-3 definition, per Rosen's Emergency Medicine)
• Anaphylaxis: histamine-mediated massive vasodilation
• Neurogenic shock: spinal cord injury/trauma, spinal anesthesia - loss of sympathetic vasomotor tone

• Hemorrhage (trauma, GI bleed, ruptured aortic aneurysm)
• Volume depletion (burns, vomiting, diarrhea, pancreatitis)
• Signs of hypoperfusion: tachycardia, dusky/mottled skin, delayed capillary refill, altered mental state, low urine output, elevated lactate, low central venous O2 saturation

• Massive MI, severe heart failure, arrhythmias, cardiac tamponade, tension pneumothorax
• Cardiac failure causing systemic hypoperfusion with lactic acidosis and organ dysfunction

• Vasodilators (nitrates, hydralazine) - especially in RV infarction, hypertrophic obstructive cardiomyopathy, aortic stenosis
• Over-diuresis

Clinical Features

• Dizziness, lightheadedness, blurred vision (cerebral hypoperfusion)
• Weakness, fatigue, pallor, diaphoresis
• Oliguria (renal hypoperfusion)
• Chest pain (cardiac ischemia)
• Altered consciousness, syncope (severe)

Management

• Increase fluid/salt intake; compression stockings
• Avoid precipitating drugs
• Fludrocortisone (mineralocorticoid - increases sodium retention)
• Midodrine (alpha-1 agonist - increases vascular tone)
• Droxidopa (norepinephrine prodrug) - approved for neurogenic orthostatic hypotension

1. Ensure adequate ventilation/oxygenation
2. Immediate hemorrhage control (direct pressure, REBOA)
3. Isotonic crystalloid infusion (10-20 mL/kg)
4. Packed red blood cell (PRBC) transfusion if perfusion is poor and hemorrhage control is delayed
5. Balanced transfusion (PRBCs : FFP : platelets) for massive hemorrhage
6. Treat coincident dysrhythmias

• IV fluid resuscitation
• Vasopressors (norepinephrine is first-line) if hypotension persists despite adequate fluid resuscitation
• Antibiotics within 1 hour
• Source control

• Treat underlying cause (revascularization in STEMI)
• Vasopressors/inotropes (dobutamine, norepinephrine)
• Mechanical circulatory support (IABP, Impella) in refractory cases

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Quick Comparison Table

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Hypothyroidism and Hyperthyroidism

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The Thyroid Axis (Background)

• Primary thyroid disease: problem is in the gland itself
• Secondary: problem in the pituitary (low TSH)
• Tertiary: problem in the hypothalamus (low TRH)

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HYPERTHYROIDISM

Definition

Causes

• TSH-secreting pituitary adenoma (PitNET)

Pathophysiology

1. Hypermetabolic state - increased basal metabolic rate, heat production, weight loss despite increased appetite
2. Beta-adrenergic overstimulation - tachycardia, tremor, anxiety, diarrhea, sweating
3. Cardiac effects - increased contractility and output → tachycardia, palpitations, cardiomegaly, atrial fibrillation; in severe/chronic cases: high-output heart failure, thyrotoxic cardiomyopathy
4. Bone resorption - osteoporosis and fracture risk (thyroid hormone stimulates osteoclasts)
5. Sympathetic nervous system overactivity - nervous system features below

Clinical Features (Robbins Pathology)

• Exophthalmos (proptosis) - due to accumulation of loose connective tissue and GAGs behind the orbit (NOT just sympathetic activation); severity does not parallel thyroid dysfunction
• Pretibial myxedema - non-pitting, waxy skin thickening over the shins
• Thyroid acropachy - clubbing + periosteal new bone formation (rare)

Diagnosis

• In secondary hyperthyroidism (pituitary adenoma): TSH is normal or elevated (paradoxical)
• "T3 toxicosis": free T4 may be normal - must measure T3 directly

Treatment

• Beta-blockers (propranolol 60-80 mg every 4h, or atenolol) - control tachycardia and adrenergic symptoms; propranolol also inhibits peripheral T4→T3 conversion

• Methimazole (preferred; once-daily dosing) - first-line for most patients
• Propylthiouracil (PTU) - preferred in pregnancy (1st trimester), thyroid storm (also blocks T4→T3 conversion), and methimazole allergy; avoid in children

• Radioactive iodine (RAI / I-131) - most common definitive treatment; causes ablation of thyroid tissue; contraindicated in pregnancy
• Surgery (thyroidectomy) - for large goiters, compressive symptoms, malignancy suspicion, pregnancy, or patient preference
• Both RAI and surgery often result in hypothyroidism requiring lifelong levothyroxine

• Mild: artificial tears, smoking cessation, selenium 100 mcg bid
• Moderate-severe: IV methylprednisolone (500 mg weekly x6, then 250 mg weekly x6)
• Non-responsive: orbital decompression surgery; teprotumumab (anti-IGF-1R monoclonal antibody)

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Thyroid Storm (Thyrotoxic Crisis)

1. PTU 500-1000 mg loading dose, then 250 mg every 4h (drug of choice - also blocks T4→T3 conversion)
2. One hour later: Stable iodide (SSKI 5 drops every 6h) - Wolff-Chaikoff effect (delay prevents iodine from being used to make new hormone)
3. Propranolol 60-80 mg PO every 4h (or 2 mg IV every 4h) - controls heart rate; also inhibits T4→T3; use esmolol IV if titration needed
4. Glucocorticoids - hydrocortisone 300 mg IV bolus, then 100 mg every 8h (reduces hormone release, inhibits conversion, covers adrenal insufficiency)
5. Supportive: cooling, IV fluids, oxygen, cholestyramine (sequesters thyroid hormones in gut), antibiotics if infection, ICU monitoring

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HYPOTHYROIDISM

Definition

Causes

• Pituitary failure (low TSH) - e.g., pituitary adenoma, Sheehan syndrome
• Hypothalamic failure (low TRH) - e.g., craniopharyngioma

Hashimoto's Thyroiditis (Autoimmune Hypothyroidism)

• CD8+ cytotoxic T-cell destruction of thyrocytes
• Cytokine-mediated injury (IFN-γ)
• Autoantibodies: anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin antibodies

Pathophysiology

1. Reduced basal metabolic rate - generalized "slowing" of all body functions
2. Reduced sympathetic tone - opposite of hyperthyroid picture
3. Accumulation of hyaluronic acid and GAGs in tissues - myxedema (non-pitting edema)
4. Hyponatremia - impaired free-water excretion
5. Dyslipidemia - reduced LDL receptor expression → elevated LDL and total cholesterol

Clinical Features

Diagnosis

• Subclinical hypothyroidism: Normal free T4, mildly elevated TSH. Management controversial; consider treatment if anti-TPO positive (will likely progress to overt hypothyroidism)
• In secondary hypothyroidism (pituitary): TSH is low or inappropriately normal despite low free T4

Treatment

• Full replacement dose: 1.6 mcg/kg/day orally
• Elderly or those with coronary artery disease: start at 12.5-25 mcg/day and increase by 12.5-25 mcg every 2-3 months to avoid precipitating angina or MI
• Monitor TSH 6-8 weeks after each dose change; target TSH within normal range
• In pregnancy: requirements increase by ~30-50%; TSH should be kept 0.1-2.5 mIU/L

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Myxedema Coma

1. LT4 IV bolus 200-400 mcg as loading dose, then 1.6 mcg/kg/day IV (25% less than oral dose due to better IV bioavailability)
2. + Liothyronine (T3) 5-20 mcg IV loading dose, then 2.5-10 mcg every 8h (T4→T3 conversion is impaired in myxedema - use lower doses in elderly/cardiac patients)
3. Hydrocortisone 50 mg IV every 6h (adrenal reserve is impaired in severe hypothyroidism)
4. Ventilatory support - usually needed for first 48h; monitor ABGs
5. Warming - external warming ONLY if temp <30°C (risk of cardiovascular collapse otherwise); use space blankets
6. Avoid hypotonic fluids - worsen hyponatremia; use hypertonic saline only for severe hyponatremia
7. Broad-spectrum antibiotics pending exclusion of infection
8. Minimize sedatives - metabolism impaired; use reduced doses
9. ICU admission

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Side-by-Side Comparison

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