When should the catheter be removed after a single‑shot spinal with 12.5 µg fentanyl and 15 mg hyperbaric bupivacaine in an 83‑year‑old patient undergoing hip surgery?

When to Remove Intrathecal Catheter After Single-Shot Spinal with Fentanyl 12.5 mcg and Bupivacaine 15 mg

There is no intrathecal catheter to remove after a single-shot spinal anesthetic—the spinal needle is withdrawn immediately after drug injection, and the block will resolve spontaneously based on the pharmacokinetics of the medications used.

Understanding the Clinical Scenario

Your question appears to conflate two distinct techniques:

• Single-shot spinal anesthesia: A one-time injection through a spinal needle that is immediately removed after drug administration 1, 2
• Intrathecal catheter placement: A catheter threaded through the needle and left in place for continuous or intermittent dosing 3

For the 83-year-old hip surgery patient receiving 15 mg hyperbaric bupivacaine plus 12.5 mcg fentanyl as a single-shot spinal, the needle is withdrawn immediately after injection—there is no catheter to manage.

Expected Duration of Spinal Block

Sensory and Motor Block Timeline

• Onset: Sensory block develops within 5-10 minutes of injection 1
• Peak effect: Maximum sensory level achieved by 10-15 minutes 3
• Duration of surgical anesthesia: 90-150 minutes with 12-15 mg hyperbaric bupivacaine 1, 2
• Complete motor block resolution: Typically 2-4 hours post-injection 4
• Return to baseline sensory function: 3-5 hours post-injection 2

Enhanced Analgesia from Fentanyl

• Postoperative analgesia extension: Intrathecal fentanyl 12.5-25 mcg prolongs pain relief by approximately 3 hours beyond the local anesthetic alone 2, 5
• Complete analgesia duration: With 12.5 mcg fentanyl added to bupivacaine, expect 130 ± 30 minutes of complete pain-free time 5
• Effective analgesia duration: Approximately 192 ± 75 minutes until first opioid requirement 5

If an Intrathecal Catheter Were Actually Placed

Should you have inadvertently placed an intrathecal catheter (recognized by CSF aspiration with positive glucose testing 3), the removal timing differs significantly:

Guideline-Based Removal Timing

• Remove at the earliest opportunity after delivery/procedure completion to minimize risks of accidental overdose and infectious complications 3
• Maximum recommended indwelling time: 24-36 hours post-delivery in obstetric patients 3
• If unwitnessed disconnection occurs: Remove immediately due to increased infection risk 3

Safety Monitoring Before Removal

• Document motor block resolution using the Bromage scale before considering removal 6
• Ensure hemodynamic stability and absence of ongoing neuraxial medication requirements 3
• Verify adequate hemostasis if patient is receiving anticoagulation 7

Anticoagulation Considerations for This Elderly Hip Surgery Patient

Timing of Prophylactic Anticoagulation After Spinal Needle Removal

• Prophylactic LMWH (enoxaparin): Wait at least 6 hours after spinal needle removal before first dose 6
• If traumatic needle placement (bloody tap): Extend waiting period to 24 hours before starting LMWH 6
• Unfractionated heparin: Can resume 6 hours after needle removal 6

Critical Safety Window

• Perform neurological assessment at 4 hours post-procedure to detect early signs of epidural hematoma 6
• Assess straight-leg raising and document any progressive neurological deficits 6
• Immediate MRI required if any new motor or sensory deficits develop, as epidural hematoma causes irreversible damage if not evacuated within 8-12 hours 6

Common Pitfalls to Avoid

• Do not confuse single-shot spinal with continuous spinal catheter techniques—they have entirely different management protocols 3
• Do not delay thromboprophylaxis beyond 6 hours in this high-risk elderly hip fracture patient unless there was traumatic needle placement 6, 8
• Do not discharge the patient until motor block has completely resolved and ambulation is safe 4
• Monitor for urinary retention, which occurs in approximately 17% of elderly patients receiving spinal anesthesia with fentanyl 4

Expected Side Effects in This Population

• Pruritus: More common with intrathecal fentanyl (occurs in elderly patients) 1
• Oxygen desaturation: Lower SaO₂ observed with fentanyl 25 mcg in geriatric patients 1
• Cognitive function: Preserved with this dose combination in elderly patients 1
• Urinary retention: May require catheterization in 17% of cases 4