Neuraxial Anesthesia: A Comprehensive Overview
Neuraxial anesthesia refers to techniques that deliver local anesthetics in close proximity to the spinal cord, including spinal, epidural, and combined spinal-epidural approaches, providing effective anesthesia and analgesia with significant advantages over general anesthesia in many clinical scenarios. 1
Types of Neuraxial Anesthesia
Spinal Anesthesia
- Involves injection of local anesthetic directly into the subarachnoid space
- Provides rapid, dense sensory and motor blockade
- Time-limited effect (unless continuous technique used)
- Pencil-point spinal needles should be used instead of cutting-bevel needles to minimize risk of postdural puncture headache 1
Epidural Anesthesia
- Local anesthetic delivered into the epidural space
- Allows for continuous infusion through catheter placement
- Provides more gradual onset compared to spinal anesthesia
- Can be used for prolonged analgesia during labor and delivery or postoperatively
- Dilute concentrations of local anesthetics with opioids should be used to minimize motor block 1
Combined Spinal-Epidural (CSE)
- Combines advantages of both techniques
- Provides rapid onset from spinal component with ability to extend duration through epidural catheter
- Particularly useful when labor duration is anticipated to be longer than the analgesic effects of spinal drugs 1
Indications
Obstetric procedures:
- Labor analgesia
- Cesarean delivery
- Postpartum tubal ligation 1
Lower extremity and lower abdominal surgeries:
- Orthopedic procedures below the umbilicus
- Urologic procedures
- Lower abdominal surgeries 2
Special populations:
- Patients with respiratory disease
- Patients at high risk for airway complications
- Patients who wish to avoid general anesthesia 1
Clinical Benefits
- Reduced mortality and morbidity: Meta-analyses show a 29% decrease in the risk of perioperative mortality when neuraxial anesthesia replaces general anesthesia 1
- Decreased pulmonary complications: 55% reduction in pneumonia risk when replacing general anesthesia 1
- Avoidance of airway manipulation: Particularly important during the COVID-19 pandemic to reduce aerosol generation 1
- Superior postoperative analgesia: Reduces opioid requirements and associated side effects 2
- Reduced risk of deep vein thrombosis: Beneficial effect on coagulation 3
Pharmacology of Neuraxial Medications
Local Anesthetics
- Amide local anesthetics (lidocaine, bupivacaine, ropivacaine, levobupivacaine) are most commonly used
- Newer enantiomer-specific compounds (ropivacaine, levobupivacaine) provide similar efficacy to bupivacaine with reduced cardiotoxicity 4
- Duration of action varies by agent:
- Short-acting: lidocaine (1-2 hours)
- Medium-acting: mepivacaine (2-3 hours)
- Long-acting: bupivacaine, ropivacaine, levobupivacaine (3-4+ hours)
Adjuvant Medications
- Opioids: Morphine, fentanyl, and sufentanil are most commonly used; extend duration and quality of analgesia 5
- Alpha-2 agonists: Clonidine and dexmedetomidine prolong block duration and enhance analgesia 5
- Vasoconstrictors: Epinephrine prolongs local anesthetic effect by reducing vascular uptake 5
- Steroids: Dexamethasone may prolong block duration 5
Technical Considerations
Patient Positioning
- Lateral decubitus: Patient lies on side with knees drawn to chest
- Sitting: Particularly useful for obese patients or when identifying midline is difficult
- Prone: Rarely used, primarily for specific procedures
Equipment
- Sterile preparation with antiseptic solution
- Appropriate needles:
- Spinal: 22-27G, preferably pencil-point design
- Epidural: 17-18G Tuohy needle
- Ultrasound guidance may improve success rates and reduce complications 2
Complications and Management
Common Complications
Hypotension: Due to sympathetic blockade
- Management: IV fluids, vasopressors (phenylephrine, ephedrine)
Post-dural puncture headache:
- Prevention: Use pencil-point needles, smaller gauge needles 1
- Management: Hydration, caffeine, analgesics, epidural blood patch if severe
Inadequate block:
- Management: Supplemental analgesia, conversion to general anesthesia if necessary
Serious Complications
Local anesthetic systemic toxicity (LAST):
- Prevention: Aspiration, test dose, incremental injection
- Management: Lipid emulsion therapy, supportive care 2
Neurological injury:
- Prevention: Careful technique, avoiding paresthesias
- Incidence: Extremely rare with proper technique
Infectious complications:
- Prevention: Strict aseptic technique
- Includes epidural abscess, meningitis (rare) 1
Special Considerations
Contraindications
- Absolute: Patient refusal, infection at injection site, coagulopathy, increased intracranial pressure
- Relative: Sepsis, hypovolemia, pre-existing neurological disease
Coagulation Status
- Important to rule out thrombocytopenia before neuraxial procedures
- Follow institutional guidelines for anticoagulant management
- Platelet count of 75,000 x 10^6/L or above is generally acceptable for neuraxial procedures 1
COVID-19 Considerations
- Neuraxial anesthesia is preferred over general anesthesia when possible during the COVID-19 pandemic
- Reduces risk of aerosol generation and viral transmission
- Standard PPE (minimum droplet precautions) recommended for providers 1
Practical Applications in Resource-Limited Settings
Neuraxial anesthesia offers particular advantages in resource-limited settings:
- Lower cost compared to general anesthesia
- Reduced need for advanced airway equipment
- Lower risk of perioperative mortality
- Relatively easy to teach and perform 6
Conclusion
Neuraxial anesthesia provides effective surgical anesthesia and analgesia with significant advantages over general anesthesia in many clinical scenarios. The choice of technique should be based on the surgical procedure, patient factors, and provider expertise. When properly performed with appropriate patient selection, neuraxial techniques offer excellent safety profiles with significant benefits for perioperative outcomes.