What is the recommended protocol for spinal block anesthesia?

Spinal Block Anesthesia Protocol

Pre-Procedure Preparation and Patient Assessment

For spinal anesthesia, use pencil-point (atraumatic) needles of 25 gauge or smaller to minimize post-dural puncture headache risk to less than 1%. 1

• Perform aspiration through the needle to confirm cerebrospinal fluid (CSF) presence before drug administration 1
• Test aspirate for glucose when clear fluid is obtained; glucose-positive fluid confirms intrathecal placement 1
• Calculate safe maximum local anesthetic dose before beginning the procedure 1

Drug Selection and Dosing by Surgical Site

Lower Extremity Surgery (Hip, Knee, Below-Knee Procedures)

Administer bupivacaine 0.5% hyperbaric 10-12.5 mg (2-2.5 ml) targeting T10 block level for hip replacement or L1-L2 level for procedures below the knee. 2, 3

• Hyperbaric solutions produce more predictable blocks with fewer high blocks compared to isobaric solutions 2
• For unilateral procedures (e.g., knee arthroscopy), use lateral positioning during injection to target the surgical side 2
• Expected onset: 10-20 minutes; duration: 2-4 hours 1

Abdominal Surgery

Target T4-T6 block level for upper abdominal procedures and T10 level for lower abdominal surgery. 2

• Bupivacaine 0.5% hyperbaric 12.5-15 mg is appropriate for most abdominal cases 2

Perineal/Perianal Procedures

Target S2-S4 block level using sitting position during injection with lower doses of hyperbaric local anesthetic. 2

• Sitting position during injection facilitates sacral spread 1

Day Surgery Procedures

Use low-dose techniques with shorter-acting agents: hyperbaric prilocaine 2% or 2-chloroprocaine to facilitate faster recovery. 1, 2

• Restrict intravenous fluids to no more than 500 ml to reduce urinary retention risk 1
• Patients should achieve return of sensation to S4-5, plantar flexion at pre-operative strength, and proprioception in the big toe before mobilization 1

Intraoperative Monitoring Protocol

Monitor blood pressure non-invasively every 5 minutes for the first 30 minutes after injection, then every 15 minutes until block regression begins. 1

• Assess block height every 5 minutes until no further extension is observed 1
• Watch for signs of high block: increasing agitation, significant hypotension, bradycardia, upper limb weakness, dyspnoea, or difficulty speaking 1
• Have vasopressors, fluids, supplemental oxygen, and airway equipment immediately available 1

Critical Safety Considerations

High/Total Spinal Block Management

High or total spinal block occurs in approximately 1 in 4,367 cases and requires immediate cardiovascular and respiratory support. 1, 3

• Support circulation with vasopressors and fluids 1
• Provide supplemental oxygen and prepare for tracheal intubation if respiratory compromise develops 1
• Total spinal anesthesia requires immediate airway management 2

Common Pitfalls to Avoid

Never assume catheter position based on inability to aspirate CSF—failure to aspirate does not exclude intrathecal placement. 1

• Avoid intrathecal lidocaine in lithotomy position due to significant risk of transient neurologic symptoms 4
• Limit attempts to 4 maximum, as multiple attempts significantly increase complication risk 3
• Ensure clear labeling and documentation to prevent inadvertent administration of epidural doses intrathecally 1, 3

Post-Procedure Recovery Assessment

Test for straight-leg raise at 4 hours from time of injection; if unable to perform, immediate comprehensive evaluation is required. 3

• First-stage recovery criteria: patient awake, protective airway reflexes returned, pain controlled 1
• Mobilization criteria: return of S4-5 sensation, plantar flexion at baseline strength, big toe proprioception intact 1
• Provide written discharge instructions including expected duration of blockade and post-dural puncture headache management 1

Adjuvant Medications

Combine local anesthetic with morphine 0.1-0.2 mg intrathecally for superior analgesia and duration compared to local anesthetic alone. 1

• This combination provides lasting postoperative analgesia in major orthopedic procedures 1
• Avoid spinal clonidine as it is less effective than morphine and carries risks of hypotension, sedation, and bradycardia 1

Alternative Local Anesthetics

Ropivacaine is approximately half as potent as bupivacaine for spinal anesthesia and requires double the dose for equivalent effect, but offers no clear advantage over bupivacaine and has a higher incidence of back pain (28%). 5, 6

Levobupivacaine provides similar block characteristics to bupivacaine but with shorter recovery times (sensory 175±57 min vs longer with bupivacaine), allowing earlier postoperative neurological examination. 7