How to treat hypotension?

How to Treat Hypotension

Immediately identify and treat the underlying physiological cause of hypotension—vasodilation, hypovolaemia, bradycardia, or low cardiac output—rather than reflexively administering fluids, as only 50% of hypotensive patients are fluid-responsive. 1, 2

Critical First Step: Determine the Underlying Cause

The most important initial action is identifying which physiological derangement is causing hypotension, as treatment differs fundamentally based on etiology 1, 2. The four primary causes require distinct therapeutic approaches:

1. Vasodilation → Treat with vasopressors

• Norepinephrine is the first-line vasopressor for vasodilation-induced hypotension 2
• Phenylephrine is best when hypotension occurs with tachycardia, though it causes reflex bradycardia 1
• Norepinephrine dosing: Dilute 4 mg in 1,000 mL of 5% dextrose solution (4 mcg/mL concentration), start at 8-12 mcg/minute, then titrate to maintain systolic BP 80-100 mmHg 3
• In previously hypertensive patients, raise BP no higher than 40 mmHg below their baseline systolic pressure 3

2. Hypovolaemia → Treat with intravascular fluids (but only if fluid-responsive)

• Perform a passive leg raise (PLR) test before administering fluids to determine fluid responsiveness 1, 2
• An increase in cardiac output after PLR strongly predicts fluid responsiveness (positive likelihood ratio = 11, pooled specificity 92%) 1
• No increase in cardiac output after PLR indicates the patient will likely not respond to fluid (negative likelihood ratio = 0.13, pooled sensitivity 88%) 1
• If fluid-responsive, administer crystalloid, colloid, or blood products as appropriate 1
• In adults, give initial fluid bolus of 250-500 mL 2
• In children, give 10-20 mL/kg (maximum 1,000 mL) of normal saline 1, 2

3. Bradycardia → Treat with anticholinergics or chronotropes

• Atropine or glycopyrronium is first-line treatment for bradycardia-induced hypotension 1, 2
• Use epinephrine or isoprenaline if refractory to anticholinergics 1
• Consider pacing for profound bradycardia 1

4. Low Cardiac Output → Treat with positive inotropes

• Dobutamine or epinephrine is recommended for myocardial dysfunction causing low cardiac output 1, 2
• Dobutamine is specifically indicated for low cardiac output from myocardial dysfunction 1

Context-Specific Blood Pressure Targets

Blood pressure targets must be adjusted based on clinical context 4:

Perioperative Hypotension

• Maintain mean arterial pressure (MAP) ≥60 mmHg in at-risk surgical patients, as MAP <60-70 mmHg or systolic BP <90-100 mmHg is associated with acute kidney injury, myocardial injury, myocardial infarction, and death 4
• Increase MAP targets when venous or compartment pressures are elevated—add roughly the compartment pressure to your MAP target 1, 2

Trauma Without Brain Injury

• Use restricted volume replacement strategy targeting systolic BP 80-90 mmHg (MAP 50-60 mmHg) until major bleeding is controlled 1, 2
• Aggressive fluid resuscitation in trauma without brain injury increases mortality and should be avoided 1, 2

Severe Traumatic Brain Injury

• Maintain MAP ≥80 mmHg to ensure adequate cerebral perfusion 1, 2
• Do not use permissive hypotension in traumatic brain injury 1, 2

Monitoring Recommendations

• Continuous intraoperative arterial pressure monitoring reduces severity and duration of hypotension compared to intermittent monitoring 4, 2
• Central venous pressure monitoring is helpful in detecting occult blood volume depletion 3
• Titrate vasoactive agents to effect rather than using fixed doses 2

Pediatric-Specific Considerations

• Initial normal saline fluid bolus of 10-20 mL/kg (maximum 1,000 mL) 1
• Avoid additional fluid boluses in patients with cardiac dysfunction or volume overload signs (pulmonary edema) 1
• Consider early colloid solutions due to potential rapid capillary leak development 1

Critical Pitfalls to Avoid

• Do not reflexively give fluids without assessing fluid responsiveness—approximately 50% of hypotensive patients are not hypovolemic and require correction of vascular tone or inotropy instead 1, 2
• Avoid abrupt withdrawal of vasopressor infusions; reduce gradually 3
• When treating intraoperative hypertension, do so carefully to avoid causing hypotension 4
• Blood volume depletion should always be corrected as fully as possible before administering vasopressors, except in emergencies where intraaortic pressures must be maintained to prevent cerebral or coronary ischemia 3
• Postoperative hypotension is often unrecognized and may be more important than intraoperative hypotension because it is often prolonged and untreated 4