BoardsBridgeSpinal Anesthesia-Induced Hypotension (SAIH): Prevention & Management
Sympatholysis from neuraxial block → vasodilation, splanchnic pooling, possible bradycardia. Phenylephrine first-line; epinephrine 0.1–1 µg/kg for severe hypotension + bradycardia.
Sympatholysis from spinal block lowers SVR and pools blood in the splanchnic venous bed; phenylephrine is first-line vasopressor; severe hypotension with severe bradycardia requires incremental epinephrine 0.1–1 µg/kg IV.
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Phenylephrine first-line; epinephrine 0.1–1 µg/kg IV (~20–200× below ACLS) for severe hypotension + severe bradycardia
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Key numbers
- Phenylephrine: 50–100 µg IV bolus; infusion 25–50 µg/min
- Ephedrine: 5–10 mg IV bolus
- Epinephrine for severe hypotension + bradycardia under SA: 0.1–1 µg/kg IV (~20–200× below ACLS)
- Bupivacaine for lateralized single-injection SA: 3.5–8 mg IT
- SAIH incidence: ~36% young adults → ~75% patients over age 50
- Pre-block hydration 250–2000 mL: not routinely recommended
Uri Rozen, MD — Licensed Physician, Israel
Source guidelines: Ferre Spinal Hypotension Adults 2020 · Millers Anesthesia 10 Ch25 Local Anesthetics · Millers Anesthesia 10 Ch41 Spinal Epidural AND Caudal Anesthesia · Millers Anesthesia 10 Ch38 Renal Pathophysiology AND Treatment FOR Perioperative Ischem
Re-review cadence: 12 months from reviewed date.
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