2023.1 Day 2 VIVA 7

Regional Anaesthesia

A 70 year old man is having an elective total knee replacement. He has a preference to be awake for the procedure. You do a thorough pre-operative assessment on this patient and he is deemed safe to proceed in Scenarioville.

What pertinent contraindications would you consider for a spinal anaesthetic?

• Infection at the insertion site (e.g., cellulitis, abscess).

• Severe hypovolaemia or shock, as this can exacerbate hypotension following spinal block.

• Allergy to local anaesthetics (e.g., amide or ester group).

• Increased intracranial pressure (e.g., from space-occupying lesions, head trauma).

• Severe coagulopathy (e.g., INR >1.5, platelet count <50,000).

What are the relative contraindications to spinal anaesthesia?

• Obesity: Difficult anatomical landmarks and risk of failed block.

• Pre-existing neurological conditions (e.g., multiple sclerosis, severe spinal deformities).

• Uncooperative or anxious patients: Difficult to achieve correct positioning.

• Severe spinal arthritis or stenosis: May make needle placement challenging.

• Infection elsewhere in the body: Sepsis can increase the risk of systemic infection from neuraxial procedures.

What are the potential complications of spinal anaesthesia, both immediate and delayed?

Immediate complications:

• Hypotension (due to sympathetic blockade).

• Bradycardia (due to vagal effects).

• Post-dural puncture headache (PDPH).

• Total spinal anaesthesia (rare, but complete respiratory paralysis).

• Nerve injury (though rare, can cause permanent damage).

Delayed complications:

• Chronic back pain.

• Infection/meningitis (due to improper technique or sterile field).

• Postoperative neurological symptoms (e.g., foot drop, bladder dysfunction).

How would you perform a spinal block for this patient?

Patient positioning:

• Sitting position (patient sitting up with legs dangling) or lateral decubitus position (side-lying).

• Ensure flexion of the lumbar spine to widen the intervertebral spaces.

Needle insertion:

• Insert the spinal needle at the L3-L4 or L4-L5 intervertebral space, aiming slightly cephalad.

• Confirm correct placement by aspirating for cerebrospinal fluid (CSF) or using a loss of resistance technique.

Local anaesthetic dose:

• Typically bupivacaine 0.5% (8-12 mg), or a mixture of bupivacaine and fentanyl. Adjust doses for age, weight, and comorbidities.

Adequacy of block:

• Bromage score (0-3 scale) for motor block:

  • Bromage 0: No motor block (patient should have full leg movement).

  • Bromage 3: Complete block (inability to move legs).

• Sensory block: Pinprick test or cold test to assess dermatomal levels (aim for T10 for lower abdominal surgery).

What would you do if you are unable to locate the intrathecal space initially?

• First step: Change needle angle slightly (usually more cephalad or caudad) or adjust the patient’s position (e.g., flexing the back more).

• Second step: Try inserting the needle at a different intervertebral space.

• Third step: Consider using a paramedian approach if the midline is difficult to locate due to anatomical variations.

• Alternative technique: If necessary, attempt a combined spinal-epidural (CSE) or use ultrasound to visualize the midline or intervertebral space.

• If all attempts fail, consider using general anaesthesia or regional techniques (e.g., epidural anaesthesia).

How would you approach the patient who becomes anxious and complains of discomfort during wound closure?

Assess the situation:

• Confirm if the patient is truly in pain or just anxious. Ask about the level of discomfort.

• Check for any inadequate anaesthesia, such as incomplete block or technical problems (e.g., catheter displacement).

Address the pain or anxiety:

• Local infiltration: Inject additional local anaesthetic (e.g., bupivacaine 0.25%-0.5%) into the wound area if not yet done.

• Inhaled nitrous oxide (Entonox) for mild sedation or to relieve anxiety.

• Opioids: Administer IV morphine (2-5 mg) or fentanyl (25-50 mcg IV) if additional analgesia is needed.

• Consider ketamine (low dose) if opioid needs are high.

• If pain persists despite these measures, consider sedation with propofol or dexmedetomidine for better control.

How would you manage airway obstruction due to oversedation in the PACU?

Immediate airway manoeuvres:

• Head tilt-chin lift or jaw thrust to open the airway.

• Suction to clear any secretions or debris that could be obstructing the airway.

• Oxygen: Administer 100% oxygen via a non-rebreather mask.

Use of airway adjuncts:

• Insert an oropharyngeal or nasopharyngeal airway if the patient remains unresponsive but without complete obstruction.

Bag-mask ventilation:

• If the patient remains hypoxic or cannot maintain their airway, consider bag-mask ventilation (using two-person technique if needed).

Advanced airway management:

• If the patient’s oxygenation doesn’t improve, consider laryngeal mask airway (LMA) or intubation if necessary, depending on the severity of obstruction.

• Sedation reversal: Administer flumazenil (if benzodiazepines were used) or naloxone (if opioids were overadministered).