Intraoperative hypotension is typically defined as:
MAP (Mean Arterial Pressure) < 65 mmHg** (most commonly used threshold) Systolic BP < 90 mmHg Reduction >20-30% from baseline
Even brief episodes of MAP < 65 mmHg can be harmful.
IOH is associated with increased risk of: Myocardial injury and infarction Acute kidney injury Stroke Delirium Increased 30-day mortality
The duration and severity both matter—even short episodes (< 5 minutes) at very low pressures can cause organ injury.
Common causes of intraoperative hypotension:
Anesthetic-related:
Vasodilation from inhaled or IV anesthetics
Sympathetic blockade (spinal/epidural anesthesia)
Opioid-induced bradycardia and vasodilation
Patient-related:
Hypovolemia (inadequate fluid replacement, bleeding) Cardiac dysfunction Medications (ACE inhibitors, beta-blockers, diuretics)
Surgical factors:
Blood loss Pneumoperitoneum Surgical manipulation-carotid sinus, bowel traction
Prevention:
Goal-directed fluid therapy Consider discontinuing ACE inhibitors/ARBs preoperatively Gradual induction of anesthesia
Treatment:
Fluid bolus for hypovolemia Vasopressors: phenylephrine (pure alpha agonist), ephedrine (mixed effects), norepinephrine for persistent hypotension
Inotropes if cardiac dysfunction present Reduce anesthetic depth if appropriate Address underlying cause-stop bleeding, adjust positioning
Proactive management rather than waiting to treat established hypotension, as prevention appears to improve outcomes.