Management of Hypotension

Step 1: Classify the Type of Shock

General Principles (All Shock Types)

1. Airway & Oxygenation: Supplemental O₂ for all patients. Intubate early for severe hypotension, acidosis, or respiratory distress — do not delay for a trial of non-invasive ventilation.
2. IV access: Large-bore peripheral or central access.
3. Monitor: Arterial line for continuous BP; consider right heart catheterization when starting vasoactive agents in cardiogenic shock.
4. Treat the cause: The definitive intervention is always etiology-specific (e.g., PCI for cardiogenic shock from MI, decompression for tension pneumothorax, source control for sepsis).

1. Hypovolemic Shock

• Isotonic crystalloids (normal saline or Ringer's lactate) — at least 30 mL/kg IV in sepsis-induced hypoperfusion; guided by hemodynamic response in hemorrhagic shock.
• Blood products for hemorrhage: packed RBCs; balanced transfusion (1:1:1 ratio of RBC:FFP:platelets) in massive hemorrhage.
• Vasopressors may be needed transiently while resuscitation proceeds but carry caution (increase afterload, risk of ischemia if underfilled).
• Control the source of bleeding.

2. Cardiogenic Shock

• Small fluid bolus may be tried cautiously — but aggressive fluids worsen pulmonary edema.
• Vasopressors & Inotropes (titrated to BP and mixed venous O₂ saturation):

• Revascularization (PCI) is the only intervention that consistently reduces mortality in cardiogenic shock from acute MI — outcomes are best within 6 hours of onset.
• Intra-aortic balloon pump (IABP): reduces systolic afterload, augments diastolic perfusion pressure — randomized trials show no mortality benefit with routine use; reserved for bridging to definitive therapy.
• Mechanical circulatory support (e.g., LVAD) if IABP fails.

3. Obstructive Shock

• Tension pneumothorax: immediate needle decompression → chest tube.
• Cardiac tamponade: pericardiocentesis.
• Massive PE: thrombolysis or catheter-directed therapy (systemic tPA if no contraindications); anticoagulation.
• Vasopressors and volume expansion are temporizing measures only.

4. Distributive Shock (Septic/Neurogenic/Anaphylactic)

Septic Shock

• Norepinephrine is preferred over dopamine — the SOAP II trial (1679 patients) showed similar mortality but significantly more arrhythmias with dopamine; subgroup analysis showed improved survival with NE in cardiogenic shock.
• In vasodilatory shock, a target MAP of 65 mmHg is standard; lowering the target to 60–65 mmHg by reducing vasopressors is not clearly superior to standard care.
• Permissive hypotension strategies should be applied cautiously.

Anaphylactic Shock

• Epinephrine IM (0.3–0.5 mg, 1:1000) into the lateral thigh — first-line.
• IV fluids for volume depletion.
• Antihistamines (H1 + H2), corticosteroids as adjuncts.
• Second dose of epinephrine if no response within 5–15 min.

Neurogenic Shock (spinal cord injury)

• IV fluids first.
• Vasopressors (norepinephrine or phenylephrine) to restore vascular tone.
• Target MAP 85–90 mmHg for the first 7 days in acute spinal cord injury.

5. Orthostatic Hypotension (Chronic / Non-Shock)

Non-pharmacologic (first-line):

• Change positions gradually; sit briefly before standing.
• Increase fluid intake (2–2.5 L water/day) and salt (1–2 tsp daily or salt tablets 0.5–1.0 g).
• Avoid hot environments, alcohol, large carbohydrate-rich meals.
• Physical countermaneuvers: leg crossing, squatting, calf raises.
• Compression stockings (≥15–20 mmHg) or abdominal binder.
• Bolus water drinking (500 mL) for acute rescue — pressor effect within 5–10 min.
• Elevate head of bed 30–45°.

Pharmacologic:

Key Vasopressor Drug Comparison Summary

Non-Pharmacological Management of Hypotension

1. Patient Education & Aggravating Factor Removal

• Review and adjust medications that worsen hypotension: diuretics, antihypertensives, tricyclic antidepressants, antipsychotics, dopamine agonists, alpha-blockers, nitrates, sildenafil.
• Address correctable comorbidities: iron deficiency, vitamin B12/D deficiencies, anaemia, dehydration, frailty.
• Educate the patient about the mechanism — understanding triggers helps enormously with self-management.

2. Positional & Behavioural Measures

Postural Precautions

• Rise slowly: sit at the edge of the bed for 30–60 seconds before standing; dangle the legs first.
• Avoid Valsalva maneuvers (straining at stool, heavy lifting) — these transiently reduce venous return.
• Urinate sitting down or use a urinal — avoids the combination of straining and standing.
• Avoid prolonged standing: shift weight, move around rather than standing still.

Environmental Avoidance

• Avoid hot, humid environments (cause cutaneous vasodilation — the main exacerbating factor in warm weather).
• Avoid prolonged hot baths or showers — warm water causes vasodilation; consider cooler showers or bathing seated.
• Avoid alcohol (a powerful vasodilator) — if consumed, restrict to the evening before bedtime.

3. Physical Countermaneuvers

4. Fluid & Salt Loading

Water (Bolus Drinking)

• 500 mL (16 oz) of plain water drunk rapidly is a potent acute pressor maneuver.
• BP rises by 30–40 mmHg on average (occasional patients see +80 mmHg or more).
• Onset: ~5 minutes; peak: 30–40 minutes; duration: ~90 minutes.
• Works via a spinal sympathoexcitatory reflex triggered by portal osmoreceptors — this effect is present only when baroreflex regulation is impaired (aging, neurodegenerative disorders).
• Hypotonic (plain) water works best — sugar or salt in beverages attenuates the pressor effect.
• Ideal timing:
  • Immediately on waking (before standing)
  • Before meals in postprandial hypotension
  • Before activities requiring prolonged standing

Chronic Fluid Intake

• Target 2–3 L of water/day to maintain adequate plasma volume.
• Monitor weight and BP; check 24-hour urinary sodium before and after starting a salt load.

Dietary Sodium

• Target 6–10 g of sodium/day (approximately 2 g salt three times daily, or 1–2 teaspoons added to food).
• Raising 24-hour urinary sodium to ~185 mmol is a reasonable target.
• Works chronically by expanding extracellular fluid volume.
• Available as salt tablets (0.5–1.0 g); may cause abdominal discomfort.
• POTS patients typically need 2 g at 8 AM and 2 g at 2 PM (covers waking hours when upright; duration of action ~4–5 hours).
• Contraindicated in heart failure, severe hypertension, or renal failure.

5. Dietary Modifications

• Eat smaller, more frequent meals low in carbohydrates — postprandial hypotension (occurring within 2 hours of eating) is driven by insulin-triggered splanchnic vasodilation.
• Avoid large carbohydrate-rich or high-sugar meals — sweets and desserts are the most potent BP depressants.
• Avoid alcohol with meals — the combination of postprandial vasodilation and alcohol-induced vasodilation is especially dangerous.
• Plan activities before eating rather than after (e.g., shopping first, then eating).
• Caffeine (coffee/tea) in the morning can blunt postprandial hypotension — useful as an adjunct.

6. Compression Garments

• Graduated compression stockings: high-waist (thigh-high) stockings providing ≥15–20 mmHg compression reduce venous pooling in the legs, increase venous return, and raise BP.
  • Must be applied before getting out of bed — put on while still lying down.
  • Remove when lying down (to preserve effectiveness in the upright posture).
  • Disadvantage: inconvenient; many patients find them uncomfortable, particularly in warm climates.
  • Best reserved for special occasions (e.g., when prolonged standing is required) in patients who find daily use impractical.
• Abdominal binder: very effective at reducing splanchnic blood pooling (the largest venous reservoir).
  • Often more practical than full-length stockings.
  • Particularly useful in neurogenic OH.

7. Exercise & Physical Conditioning

• Deconditioning worsens OH — patients should not stop exercising.
• Preferred modes:
  • Recumbent or seated exercise (recumbent cycling, rowing)
  • Water aerobics / water jogging in shoulder-deep water — water reduces the gravitational pull on blood volume to ~¼ of its normal value, allowing exercise with minimal orthostatic stress.
  • Swimming pool exercise preferred; cooler water temperatures are better (warm water → cutaneous vasodilation).
• Caution: great care when exiting the pool — full gravitational pull returns with a vasodilated muscular (and possibly cutaneous) system.
• Orthostatic (tilt) training for recurrent reflex syncope:
  • Lean upright with back against a wall, feet ~30 cm from the wall (simulating ~70° head-up tilt).
  • Duration: 10–20 minutes, once or twice daily.
  • Performed on carpeted floor away from sharp furniture.
  • Evidence: promising in open-label trials; worth attempting for OH and POTS as well.

8. Sleeping Position

• Elevate the head of bed by 30–45° (using bed risers, wedge pillow, or raising the headboard).
• Prevents nocturnal supine hypertension, which causes pressure diuresis and volume loss during sleep → worsened morning OH.
• Reduces overnight diuresis by maintaining mild head-up tilt, thereby preserving intravascular volume on waking.
• Also stimulates the renin-angiotensin-aldosterone system overnight, providing some volume protection.

Summary Framework

Step 1:  Remove aggravating factors (drugs, comorbidities)
Step 2:  Patient education (positional awareness, trigger avoidance)
Step 3:  Fluid & salt loading (2–3 L water/day; 6–10 g Na/day)
Step 4:  Dietary modification (small meals, low-carb, avoid alcohol)
Step 5:  Compression garments (abdominal binder ± thigh-high stockings)
Step 6:  Physical countermaneuvers (leg crossing, squatting, tiptoes)
Step 7:  Exercise prescription (recumbent/pool-based)
Step 8:  Head-of-bed elevation (30–45°)
Step 9:  Orthostatic training (tilt training for reflex syncope/POTS)
         ↓ if still symptomatic
         Pharmacological therapy