What Are the Most Common Complications of Spinal Anesthesia?

Spinal anesthesia—also known as subarachnoid block—is a widely used neuraxial technique for surgical procedures involving the lower abdomen, pelvis, and lower extremities. While generally safe and effective, it carries several well-documented complications. The most common adverse effects include hypotension, bradycardia, post-dural puncture headache (PDPH), urinary retention, and transient neurological symptoms.

Hypotension is the most frequent hemodynamic complication, occurring in up to 30–80% of patients depending on patient factors and anesthetic technique. It results primarily from sympathetic blockade-induced vasodilation and reduced systemic vascular resistance, often compounded by decreased venous return and cardiac output. Prophylactic intravenous fluid loading and prompt administration of vasopressors—such as phenylephrine or ephedrine—are standard preventive and management strategies.

Bradycardia, particularly in patients with intact vagal tone or those undergoing procedures involving the perineum or lower abdomen, may arise due to unopposed parasympathetic activity following high thoracic sympathetic blockade. In severe cases, this can progress to sinus arrest or asystole, necessitating immediate atropine administration and readiness for advanced cardiac life support.

Post-dural puncture headache affects approximately 1–3% of patients overall but rises significantly—up to 25–30%—with larger-gauge or cutting-tip needles. It typically presents as an orthostatic headache within 24–48 hours after spinal puncture and resolves spontaneously in most cases within days to weeks. Conservative management includes hydration, caffeine, and analgesics; refractory cases may require an epidural blood patch.

Urinary retention occurs in roughly 10–25% of patients, especially after prolonged blocks or when sensory levels extend above T10. It reflects temporary impairment of sacral parasympathetic outflow to the detrusor muscle and usually resolves spontaneously within hours to a day. Catheterization may be necessary if bladder distension or discomfort develops.

Transient neurological symptoms—including back pain, radicular leg pain, or paresthesias—are reported in 1–5% of cases and are typically self-limiting, resolving within days to weeks. Though rare, more serious complications such as cauda equina syndrome, spinal hematoma, or meningitis must be recognized promptly and managed emergently.