What are the guidelines for administering spinal anesthesia to patients undergoing surgery?

Guidelines for Administering Spinal Anesthesia in Surgical Patients

Spinal anesthesia is recommended as a primary anesthetic technique for appropriate surgical procedures, particularly in day surgery, lower extremity, perineal, and lower abdominal procedures, with specific dosing and technique considerations to minimize complications and optimize patient outcomes.

Indications and Patient Selection

• FDA-approved indications: Subarachnoid injection for the production of spinal anesthesia in adults 1

• Recommended surgical procedures:

  • Lower extremity and perineal procedures (e.g., TURP, vaginal hysterectomy)
  • Lower abdominal procedures (e.g., abdominal hysterectomy, tubal ligation)
  • Cesarean section and vaginal delivery
  • Day surgery procedures 2
  • Laparoscopic procedures in high-risk patients 3
  • Lumbar spine surgeries in high-risk patients 4

• Contraindications 1:

  • Intravenous regional anesthesia (Bier Block)
  • Septicemia
  • Severe hemorrhage, hypotension or shock
  • Clinically significant arrhythmias (e.g., complete heart block)
  • Known hypersensitivity to bupivacaine or amide-type local anesthetics
  • Local infection at the site of proposed lumbar puncture
  • Pre-existing CNS diseases (pernicious anemia, poliomyelitis, syphilis, tumor)
  • Coagulopathies or anticoagulant therapy

Pre-procedure Assessment

• Complete pre-anesthetic assessment focusing on:

  • Cardiovascular conditions
  • Respiratory issues
  • Metabolic disorders
  • Current medications and allergies
  • Airway assessment 5

• Ensure availability of:

  • Oxygen
  • Cardiopulmonary resuscitative equipment and drugs
  • Personnel resources for managing potential complications 1

Technique and Administration

1. Patient positioning:

   • Sitting position is often preferred for neuraxial techniques in obese patients 2
   • For unilateral procedures, consider lateral position with surgical site dependent when using hyperbaric solutions 2

2. Needle selection:

   • Use smaller gauge (25G) pencil-point needles to reduce post-dural puncture headache incidence to <1% 2

3. Medication preparation:

   • Visually inspect solution for particulate matter and discoloration
   • Avoid mixing with other local anesthetics 1

4. Administration procedure:

   • Aspirate for blood and cerebrospinal fluid before injection
   • Avoid rapid injection
   • Ensure patient has indwelling IV catheter for adequate access
   • Use the lowest effective dose to avoid high motor block 1

5. Dosing guidelines 1:

   • Vaginal delivery: Starting dose 6 mg (0.8 mL)
   • Lower extremity/perineal procedures: 7.5 mg (1 mL)
   • Lower abdominal procedures: 12 mg (1.6 mL)
   • Cesarean section: 7.5-10.5 mg (1-1.4 mL)

6. For day surgery:

   • Use low-dose local anesthetic techniques
   • Consider shorter-acting agents (hyperbaric prilocaine 2%, 2-chloroprocaine)
   • Target dosing to surgical site (e.g., lateral for unilateral procedures) 2

Monitoring and Management

• Intraoperative monitoring:

  • Constant monitoring of cardiovascular and respiratory vital signs
  • Monitor patient's level of consciousness
  • Assess block height at least every 5 minutes until no further extension is observed 2

• Hemodynamic management:

  • Be prepared to treat hypotension with vasopressors and fluids
  • Restrict IV fluids to no more than 500 ml to reduce urinary retention risk in day surgery 2
  • Monitor for signs of high block: increasing agitation, significant hypotension, bradycardia, upper limb weakness, dyspnoea 2

• Respiratory considerations:

  • Provide supplemental oxygen during spinal anesthesia 2
  • Be prepared for respiratory support if high block occurs 2

Post-procedure Care

• Recovery criteria for day surgery patients after spinal anesthesia 2:

  • Return of sensation to peri-anal area (S4-5)
  • Plantar flexion of foot at pre-operative strength levels
  • Return of proprioception in the big toe

• Discharge considerations:

  • Patients may be discharged with residual motor/sensory blockade if:
    • The limb is protected
    • Appropriate support is available at home
    • Written instructions are provided 2

• Analgesic planning:

  • Implement analgesic plan before block wears off
  • Consider premedication with oral analgesics and postoperative oral analgesics with written instructions 2

Special Considerations

1. Obese patients:

   • Sitting position recommended for neuraxial techniques
   • Tilt bed toward operator so patient naturally leans forward
   • Leave at least 5 cm catheter in epidural space to reduce migration risk
   • Calculate local anesthetic dose using lean body weight 2

2. Elderly patients:

   • Reduced doses of intrathecal bupivacaine (<10 mg) to reduce hypotension
   • Cautious use of sedation 2
   • Avoid long-acting benzodiazepines 2

3. High-risk patients:

   • Spinal anesthesia may be safer than general anesthesia for certain high-risk patients
   • Associated with better hemodynamic stability and reduced postoperative morbidity 4, 6

Potential Complications and Management

• Post-dural puncture headache:

  • Reduced with smaller gauge and pencil-point needles
  • Include information on post-dural puncture headache in discharge instructions 2

• High or total spinal block:

  • Support circulation with vasopressors and fluids
  • Provide supplemental oxygen
  • Be prepared for tracheal intubation and ventilation if necessary 2

• Hypotension:

  • More problematic in obese patients who are less tolerant of lying flat
  • Use appropriate fluid loading and vasoconstrictors tailored to individual requirements 2

• Catheter migration:

  • Failure to aspirate CSF does not exclude positioning within subarachnoid space
  • Always use slow and incremental dosing when giving any top-up 2

By following these guidelines, spinal anesthesia can be safely and effectively administered for appropriate surgical procedures, with careful consideration of patient factors, proper technique, and vigilant monitoring to minimize complications and optimize outcomes.