What medications are used to treat hypotension?

Medications for Treating Hypotension

Norepinephrine is the first-line vasopressor for treating hypotension, particularly in distributive shock, while fluid resuscitation with crystalloids should be initiated first in hypovolemic states. 1

Understanding Hypotension

Hypotension is defined as systolic blood pressure <90 mmHg, mean arterial pressure (MAP) <65 mmHg, or a significant drop from baseline. The treatment approach depends on the underlying cause of hypotension:

Initial Assessment

• Determine shock type: hypovolemic, cardiogenic, distributive, or obstructive
• Assess fluid status using physical examination, ultrasound, or passive leg raise test
• Evaluate for end-organ hypoperfusion (altered mental status, decreased urine output, elevated lactate)

Treatment Algorithm by Cause

1. Hypovolemic Hypotension

• First-line: Balanced crystalloids (10-20 mL/kg) 2
• Second-line: Blood products if hemorrhagic
• Target: MAP ≥65 mmHg (or higher if chronically hypertensive) 1

2. Distributive Shock (Sepsis, Anaphylaxis)

• First-line: Norepinephrine (0.05-2 mcg/kg/min) 1
• Second-line: Vasopressin (up to 0.03 UI/min) to reduce norepinephrine requirements 1
• Third-line: Epinephrine as a single agent 1

3. Cardiogenic Shock

• First-line: Inotropes (dobutamine 2-20 μg/kg/min) 1
• Second-line: Norepinephrine if persistent hypotension with tachycardia 1
• Third-line: Dopamine if bradycardia present 1

4. Obstructive Shock

• Address underlying cause (tension pneumothorax, cardiac tamponade, pulmonary embolism)
• Support with fluids and vasopressors as bridge to definitive treatment

Specific Medications for Hypotension

Vasopressors

1. Norepinephrine (0.05-2 mcg/kg/min)

   • First-line for most types of shock after adequate fluid resuscitation
   • Potent α1-adrenergic effects with moderate β1 effects
   • Increases SVR and maintains cardiac output

2. Phenylephrine (0.5-9 mcg/kg/min)

   • Pure α1-agonist
   • Indicated for hypotension from vasodilation 3
   • Best for situations with tachycardia (causes reflex bradycardia)
   • Useful in afterload-dependent states (aortic stenosis, mitral stenosis) 1

3. Vasopressin (up to 0.03 UI/min)

   • Adjunct to norepinephrine in refractory shock
   • May reduce norepinephrine requirements and renal replacement needs 1

4. Epinephrine (0.05-0.5 mcg/kg/min)

   • Alternative to norepinephrine + dobutamine combination
   • Potent α and β effects
   • Can cause tachycardia, arrhythmias, and increased lactate

5. Dopamine (3-20 mcg/kg/min)

   • Dose-dependent effects:
     • 3-5 mcg/kg/min: primarily dopaminergic (renal)
     • 5-10 mcg/kg/min: β1-adrenergic (inotropic)

     • 10 mcg/kg/min: α-adrenergic (vasopressor)

   • Consider only in bradycardic hypotensive patients 1

Inotropes

1. Dobutamine (2-20 mcg/kg/min)

   • Primary inotrope for cardiogenic shock
   • β1-adrenergic effects increase cardiac output
   • May cause vasodilation and worsen hypotension if used alone

2. Milrinone (0.375-0.75 mcg/kg/min)

   • Phosphodiesterase III inhibitor
   • Inotropic and vasodilatory effects
   • Useful in right ventricular failure and pulmonary hypertension

Special Considerations

• Chronically hypertensive patients: May require higher MAP targets (75-85 mmHg) 2
• Elderly patients: May benefit from lower MAP targets (60-65 mmHg) 2
• Trauma patients: Consider permissive hypotension (SBP 80-90 mmHg) until bleeding is controlled 2
• Cardiogenic shock with β-blocker toxicity: Consider levosimendan or PDE III inhibitors 1

Pitfalls to Avoid

1. Overaggressive fluid resuscitation: Only ~50% of postoperative hypotensive patients respond to fluid boluses 1

   • Use passive leg raise test to assess fluid responsiveness
   • Excessive fluids can worsen outcomes in certain conditions

2. Delayed vasopressor initiation: Don't wait for "complete" fluid resuscitation before starting vasopressors in severe shock

3. Inappropriate vasopressor selection:

   • Avoid phenylephrine in cardiogenic shock
   • Avoid pure vasopressors in hypovolemic states before adequate volume resuscitation

4. Ignoring underlying causes: Always search for and treat the primary cause of hypotension (bleeding, sepsis, cardiac dysfunction)

5. Failure to monitor response: Continuously assess MAP, heart rate, urine output, mental status, and lactate clearance to guide therapy

By following this algorithm and selecting the appropriate medication based on the underlying cause of hypotension, you can effectively restore adequate tissue perfusion and improve patient outcomes.