What to do if hypotension occurs after an operation?

Management of Postoperative Hypotension

For postoperative hypotension, perform a passive leg raise (PLR) test to assess fluid responsiveness - if positive, administer IV fluids; if negative, use vasopressors targeting a systolic blood pressure ≥90 mmHg or mean arterial pressure ≥65 mmHg. 1

Initial Assessment and Monitoring

• Perform a structured bedside assessment to determine the etiology of hypotension and evaluate for signs of end-organ dysfunction 1, 2
• Consider hypotension clinically significant when systolic blood pressure <90 mmHg or mean arterial pressure <65-70 mmHg 1
• Implement more frequent blood pressure monitoring (every 15 minutes initially) in patients with postoperative hypotension 1, 2
• Consider continuous hemodynamic monitoring if hypotension persists or worsens, as this can detect nearly twice as much hypotension compared to intermittent monitoring 1

Fluid Responsiveness Assessment

• Perform a passive leg raise (PLR) test, which strongly predicts fluid responsiveness with 88% sensitivity and 92% specificity 1
• A positive PLR test (increased cardiac output or blood pressure with leg elevation) indicates that the patient will likely respond to fluid administration 1
• Only about 50-54% of hypotensive postoperative patients are actually fluid responsive, making assessment crucial before fluid administration 1

Management Algorithm

For Fluid Responsive Patients (Positive PLR Test):

• Administer crystalloid fluids (e.g., lactated Ringer's solution) in 250-500 mL boluses 1, 3
• Reassess after each bolus to avoid fluid overload 1
• Target systolic blood pressure ≥90 mmHg or mean arterial pressure ≥65 mmHg 1

For Non-Fluid Responsive Patients (Negative PLR Test):

• Initiate vasopressor therapy rather than continuing fluid administration 1, 2
• Norepinephrine is the preferred first-line vasopressor 4:
  • Dilute 4 mg in 1000 mL of 5% dextrose solution (4 mcg/mL)
  • Start at 2-3 mL/minute (8-12 mcg/minute) and titrate to effect
  • Maintenance dose typically ranges from 0.5-1 mL/minute (2-4 mcg/minute) 4
• Administer vasopressors through a large vein, preferably central, to avoid extravasation 4

Special Considerations

• For patients with preoperative hypertension, the threshold for hypotension-related harm may be higher than 90 mmHg systolic 1
• The risk of organ injury increases with longer durations of hypotension 1
• Consider phenylephrine in patients with tachycardia, as it can produce reflex bradycardia 1
• Epinephrine (0.05-2 mcg/kg/min) can be considered for patients with poor cardiac output 5
• In hemorrhagic shock, control the source of bleeding as the primary intervention while maintaining a target systolic blood pressure of 80-90 mmHg (permissive hypotension) until definitive control is achieved 3, 6

Common Pitfalls to Avoid

• Do not automatically treat hypotension with fluid boluses without assessing fluid responsiveness, as approximately 50% of hypotensive postoperative patients are not fluid responsive 1
• Avoid abrupt withdrawal of vasopressors; taper gradually once blood pressure stabilizes 4
• Do not delay treatment of symptomatic hypotension while waiting for diagnostic tests 1
• Recognize that postoperative hypotension often goes undetected and may last longer than intraoperative hypotension, potentially causing more harm 1

Monitoring Response to Treatment

• Continue frequent monitoring until blood pressure stabilizes 1
• Assess for signs of improved tissue perfusion (improved mental status, urine output, capillary refill) 1
• Consider transfer to a higher level of care if hypotension persists despite initial interventions 1, 2