How to manage hypotension?

Management of Hypotension

Immediately assess the underlying cause of hypotension using passive leg raise (PLR) testing to determine fluid responsiveness, then treat with IV fluids if PLR-positive or vasopressors if PLR-negative, while avoiding reflexive fluid administration in the approximately 50% of hypotensive patients who are not hypovolemic. 1, 2

Initial Assessment and Cause Determination

Perform bedside hemodynamic assessment to identify the physiological mechanism:

• Hypovolemia - inadequate preload 1
• Vasodilation - reduced vascular tone 1
• Bradycardia - inadequate heart rate 1
• Low cardiac output - myocardial dysfunction 1

Use passive leg raise (PLR) testing as the primary diagnostic tool - an increase in cardiac output after PLR strongly predicts fluid responsiveness with a positive likelihood ratio of 11 and pooled specificity of 92%, while no increase in cardiac output classifies patients who will not respond to fluids with a negative likelihood ratio of 0.13 and pooled sensitivity of 88%. 2

Critical pitfall: Typical signs and symptoms of suspected hypovolemia (oliguria, tachycardia) are NOT predictive of fluid responsiveness - only 54% of postoperative patients with suspected hypovolemia actually respond to fluid boluses, meaning the reflexive approach of giving IV fluids is inappropriate approximately 50% of the time. 2, 1

Treatment Algorithm Based on PLR Testing

If PLR Test is Positive (Fluid Responsive)

Administer crystalloid fluid resuscitation:

• Adults: 250-500 mL bolus of normal saline or lactated Ringer's solution 1
• Children: 10-20 mL/kg bolus (maximum 1,000 mL), with up to 30 mL/kg in the first hour if needed 2
• Reassess after each bolus - if hypotension persists after adequate fluid administration, switch to vasopressor therapy 2

Avoid excessive fluid administration in patients with:

• Cardiac dysfunction or signs of volume overload (pulmonary edema) 2
• Capillary leak syndrome - consider early use of colloid solutions in these cases 2

If PLR Test is Negative or Hypotension Persists After Fluids

Initiate vasopressor therapy - norepinephrine is first-line:

• Norepinephrine: Initial infusion rate of 2-3 mL per minute (8-12 mcg per minute), titrated to effect 3, 4
• Target mean arterial pressure (MAP) ≥65 mmHg or systolic BP 80-100 mmHg 1, 3
• Add vasopressin if hypotension persists on norepinephrine alone 1

Alternative vasopressor considerations:

• Phenylephrine: Reserve for hypotension with tachycardia only, as it causes reflex bradycardia especially in preload-independent states 2, 1
• Dopamine: Can be used at 2-5 mcg/kg/min initially, increasing by 5-10 mcg/kg/min increments up to 20-50 mcg/kg/min, but norepinephrine is preferred 5

If Low Cardiac Output is Identified

Administer positive inotropes:

• Dobutamine or epinephrine as first-line inotropic agents 1, 3
• Add norepinephrine if hypotension persists despite inotropic support 1

If Bradycardia is Present

Treat with anticholinergics:

• Atropine or glycopyrronium as first-line therapy 1

Context-Specific Management

Anaphylaxis-Related Hypotension

Epinephrine is the definitive treatment:

• Intramuscular epinephrine 1:1000: 0.2-0.5 mL (0.01 mg/kg in children, max 0.3 mg) into deltoid or anterolateral thigh every 5 minutes as needed 2
• Place patient in recumbent position with elevated lower extremities 2
• Administer large volumes of crystalloid - may require 1-2 L in adults at 5-10 mL/kg in first 5 minutes 2
• For refractory hypotension: Consider epinephrine infusion (1 mg in 250 mL D5W = 4 mcg/mL, infused at 1-4 mcg/min) only after failure of multiple IM doses 2

Postoperative Hypotension

Treat symptomatic hypotension immediately:

• For positive PLR test: IV fluid is appropriate 2
• If preload augmentation not needed: Vasopressor or inotropic support is indicated 2
• Consider transfer to higher level of care if hypotension persists despite initial interventions or requires multiple vasoactive agents 2

Traumatic Brain Injury

Maintain MAP ≥80 mmHg to ensure adequate cerebral perfusion - permissive hypotension should NOT be used 1

Trauma Without Brain Injury

Use restricted volume replacement:

• Target systolic BP 80-90 mmHg until major bleeding is controlled 1
• Avoid aggressive fluid resuscitation as it increases mortality 1

Orthostatic Hypotension (Chronic Management)

Non-pharmacological measures first:

• Exclude exacerbating drugs, educate on behavioral strategies, increase fluid and salt intake 1, 6

Pharmacological treatment:

• Midodrine: First-line drug, dosed individually up to 10 mg two to four times daily 1, 6
• Fludrocortisone: Alternative first-choice, initially 0.05-0.1 mg daily, titrated to 0.1-0.3 mg daily with mandatory serial monitoring of electrolytes and renal function 1, 6

Critical pitfall: Balance increasing standing BP against avoiding marked supine hypertension - do not increase doses if symptomatic hypotension occurs 1

Monitoring and Titration

Administer vasoactive agents targeted to effect, not fixed doses:

• Use intra-arterial monitoring for precise BP targeting when available 1
• Continuous intraoperative arterial pressure monitoring reduces severity and duration of hypotension compared to intermittent monitoring 1
• Monitor urine output, cardiac output, and end-organ perfusion continuously 2, 5

When discontinuing vasopressor infusions:

• Gradually decrease the dose while expanding blood volume with IV fluids to prevent marked hypotension 5, 4
• Sudden cessation may result in marked hypotension 5

Critical Pitfalls to Avoid

• Do not give reflexive fluids without PLR testing - approximately 50% of hypotensive patients are not hypovolemic and require vasopressor/inotropic support instead 2, 1
• Do not use phenylephrine in bradycardic patients - it causes reflex bradycardia 2, 1
• Do not use permissive hypotension in traumatic brain injury - maintain MAP ≥80 mmHg 1
• Do not administer additional fluid boluses in patients with cardiac dysfunction or volume overload signs 2, 1
• Do not infuse dopamine or norepinephrine through small peripheral veins - extravasation causes tissue necrosis 5, 4
• Do not add sodium bicarbonate to dopamine - it is inactivated in alkaline solution 5