Spinal anesthesia provides dense surgical block for procedures below the umbilicus. The technique involves injection of local anesthetic into the subarachnoid space, producing rapid-onset sensory, motor, and sympathetic blockade. Understanding baricity, patient positioning, and hemodynamic management is critical for safe and effective spinal anesthesia practice.
Hyperbaric bupivacaine 0.75% is the most commonly used agent: 7.5–15 mg for lower extremity/abdominal surgery
Onset 3–5 minutes; duration 90–150 minutes depending on agent and dose
Sympathectomy extends 2–6 dermatomes above sensory block, causing vasodilation and hypotension
Post-dural puncture headache (PDPH) risk reduced with pencil-point needles (Whitacre, Sprotte)
Absolute contraindications: patient refusal, infection at insertion site, coagulopathy, severe hypovolemia
Pre-load or co-load with 500–1000 mL crystalloid and have phenylephrine infusion ready before placing a spinal for cesarean delivery. Vasopressor prophylaxis reduces the incidence and severity of spinal-induced hypotension more effectively than fluid alone.
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