Failed Spinal Anaesthesia: Management and Airway Strategy

Quick Answer

Failed spinal anaesthesia occurs in 1-5% of caesarean sections, with complete failure reported in 0.5-1% of cases. When spinal anaesthesia fails to provide adequate surgical anaesthesia, the anaesthetist must rapidly decide between re-performing the spinal, converting to epidural, attempting a second spinal, or converting to general anaesthesia (GA). This decision depends on the urgency of surgery, extent of block failure, patient factors, and anaesthetist expertise. The safety of mother and baby is paramount—never allow maternal compromise or foetal distress to worsen while attempting repeated regional techniques. If converting to GA in obstetric patients, remember the increased risk of difficult intubation (10-fold higher than general population), rapid desaturation (reduced FRC, increased O₂ consumption), and need for left uterine displacement to prevent aortocaval compression.

Clinical Pearl: A "failed spinal" is an emergency that tests clinical judgment. The question is not "Can I get a working block?" but "Is it safe to keep trying?" If surgery is urgent or maternal/foetal status is deteriorating, convert to GA immediately rather than risk aspiration or foetal hypoxia.[1]

Definition and Classification of Spinal Failure

Types of Spinal Failure

[2,3,4]

Causes of Spinal Failure

Technical Factors (60-70% of failures)

Patient Factors (30-40% of failures)

[5,6,7]

Assessment of Failed Spinal

Immediate Assessment (2-5 minutes post-injection)

Sensory Testing:

• Test cephalad spread using ice or pinprick every 2 minutes
• Target: T4 level (nipple line) for caesarean section
• Document highest level achieved

Motor Assessment:

• Modified Bromage scale (0=full movement, 3=no movement)
• Expected: Grade 2-3 (inability to straight leg raise)

Sympathetic Block Assessment:

• Warm, dry lower limbs
• Absence of sweating
• May have hypotension (indicates some block present)

Decision Algorithm ("STOP-ACT" Framework)

S - Safety assessment (maternal/foetal status) T - Time available (urgency of surgery) O - Options evaluation (repeat regional vs GA) P - Plan execution (with backup plans)

A - Airway assessment (if GA needed) C - Communication (surgeon, patient, team) T - Timely decision (don't delay)

[8,9]

Management Options

Option 1: Repeat Spinal Anaesthesia

Indications:

• Complete failure with no block after 10-15 minutes
• No surgical urgency (category 3-4)
• Easy first attempt (good anatomy, no technical issues identified)
• No contraindications to GA if second spinal fails

Technique:

1. Full re-preparation: New sterile field, new equipment
2. Different interspace: Usually one space higher (L2-3 if L3-4 used)
3. Sitting position: Often easier second attempt
4. Reduced dose: Typically 75% of original dose (risk of high block if first dose partially absorbed)
5. Ultrasound: If available, confirm anatomy
6. Alternative technique: Consider paramedian approach if midline failed

Monitoring:

• Watch for high/total spinal (first dose may have partial effect)
• Be prepared for significant hypotension
• Have GA equipment immediately available

Contraindications:

• Surgical urgency (category 1-2)
• Maternal distress/deterioration
• Previous difficult spinal (multiple attempts already)
• Coagulopathy (risk of spinal haematoma with repeated attempts)

[10,11,12]

Option 2: Conversion to Epidural Anaesthesia

Indications:

• Partial block (some sensory/motor effect)
• Insufficient height or patchy block
• Time available (20-30 minutes to achieve surgical anaesthesia)
• Experienced practitioner with epidural expertise

Technique:

1. Place epidural at different level
2. Test dose (3 mL lignocaine with adrenaline) - watch for intrathecal/intravascular
3. Titrate local anaesthetic in 5 mL aliquots
4. Expect 15-20 minutes to surgical anaesthesia
5. Can add opioids (fentanyl) for intraoperative comfort

Advantages:

• Extends partial block
• Can titrate to desired level
• No dural puncture (reduced PDPH risk vs second spinal)

Disadvantages:

• Time required (not suitable for urgent cases)
• Risk of total spinal if subarachnoid placement unrecognised
• Requires expertise
• May still fail

[13,14]

Option 3: General Anaesthesia Conversion

Indications:

• Urgent surgery (category 1-2)
• Maternal or foetal compromise
• Multiple failed regional attempts
• Patient preference after informed discussion
• Contraindications to further regional attempts

Obstetric Airway Considerations:

Difficult Intubation Incidence:

• General population: 1.5-6%
• Obstetric patients: 3-8%
• Labouring women: Up to 10-12%
• Failed intubation: 1:250 to 1:500 obstetric GA

Rapid Sequence Induction Protocol:

1. Preparation:

   • Left uterine displacement (15-30° wedge)
   • Suction, working IV, pre-oxygenation
   • Backup airway equipment (LMA, video laryngoscope, difficult airway cart)

2. Pre-oxygenation:

   • 100% O₂ for 3 minutes or 8 vital capacity breaths
   • Head-up position (30°) if possible (reduces aspiration risk, improves FRC)

3. Cricoid pressure:

   • Controversial but commonly used
   • Release if impedes laryngoscopy or ventilation

4. Induction:

   • Thiopentone 4-5 mg/kg (historical standard, foetal protection)
   • Propofol 2-2.5 mg/kg (acceptable alternative)
   • Ketamine 1-1.5 mg/kg (if haemodynamic compromise)

5. Muscle relaxant:

   • Suxamethonium 1-1.5 mg/kg (fastest onset)
   • Rocuronium 1.2 mg/kg (if suxamethonium contraindicated; sugammadex ready)

6. Intubation:

   • First attempt best attempt (experienced practitioner)
   • Use short-handled laryngoscope (avoids breast compression)
   • Bougie or stylet ready
   • Video laryngoscopy if available (reduces intubation attempts)

7. Confirmation:

   • ETCO₂ waveform (essential)
   • Auscultation
   • Chest rise

8. Maintenance:

   • 50% N₂O/50% O₂ + volatile (reduces volatile requirement, foetal wellbeing)
   • Opioid after delivery (reduces uterine tone if given before)
   • Maintain uterine displacement until delivery

[15,16,17,18]

Failed Intubation in Obstetrics (Can't Intubate, Can Ventilate)

Immediate Response:

1. CALL FOR HELP (most important step)
2. Maintain oxygenation (life before airway)
   • Face mask ventilation with 100% O₂
   • Two-person technique if needed
   • Oral airway, left displacement
3. Do NOT persist with intubation attempts (>3 attempts = increased complications)
4. Insert supraglottic airway (LMA)
   • ProSeal LMA or Supreme preferred (gastric channel)
   • Provides definitive airway in 90-95%
5. Consider waking patient if:
   • Surgery not immediately life-threatening
   • LMA provides adequate ventilation
   • No foetal distress
6. Proceed with LMA if:
   • Surgery urgent
   • LMA provides adequate ventilation
   • Risk of aspiration deemed acceptable vs intubation trauma

Can't Intubate, Can't Ventilate (CICV):

Emergency Front-of-Neck Access (eFONA):

Scalpel Cricothyroidotomy Technique:

1. Extend neck (if not contraindicated)
2. Identify cricothyroid membrane
3. Transverse stab incision through membrane with #10 scalpel
4. Keep blade in place, turn 90° (handle to feet)
5. Insert bougie alongside blade, direction towards lungs
6. Advance cuffed tube (6.0) over bougie
7. Remove bougie, inflate cuff, confirm position
8. Secure tube

Key Points:

• Do not attempt if any ventilation possible
• Practice on models (regular training essential)
• Decision fatigue common—have clear trigger points

[19,20,21]

Option 4: Local Anaesthetic Infiltration

Indications:

• Emergency situation
• GA contraindicated (maternal cardiac disease, difficult airway predicted)
• Experienced surgeon willing to operate
• Supplement to weak spinal

Technique:

• Surgeon infiltrates field with lignocaine and adrenaline
• Systemic opioids essential (remifentanil infusion or large fentanyl doses)
• IV ketamine for supplementation
• Supplementary nitrous oxide if available

Limitations:

• Not suitable for all procedures
• Patient discomfort
• Surgeon-dependent
• May need conversion to GA anyway

[22]

Decision-Making Algorithm

When Spinal Fails—Decision Tree

SPINAL ANAESTHESIA FAILURE
         |
         v
Is surgery URGENT (Category 1-2)?
         |
    YES /    \ NO
       /      \
      v        v
Convert to GA  Is there TIME (20-30 min)?
IMMEDIATELY           |
                YES /   \ NO
                   /     \
                  v       v
            Attempt      Convert to GA
            Epidural     (Category 3-4)
                 |
                 v
          Epidural works?
                 |
            YES /  \ NO
               /    \
              v      v
           Proceed  Convert to GA
           with      or Second
           surgery   Spinal (if expert)

Key Decision Points

Convert to GA if ANY of the following:

• Category 1 (immediate threat to life)
• Category 2 (foetal distress, maternal haemorrhage)
• Failed two regional attempts already
• Maternal distress/inability to lie still
• Patient preference for GA
• Haemodynamic instability
• Predicted difficult airway BUT can bag-mask ventilate

Attempt second spinal if ALL of the following:

• Category 3-4 surgery
• Easy first spinal attempt (good landmarks)
• No maternal/foetal compromise
• First spinal clearly technical failure (no CSF obtained, wrong space)
• GA backup immediately available
• Experienced practitioner

Attempt epidural if:

• Partial block present
• Category 3-4
• 20-30 minutes available
• Experienced with epidural technique

[23,24]

Safety Priorities

Maternal Safety Priorities

1. Airway protection (avoid aspiration)
2. Adequate oxygenation (prevent hypoxia)
3. Haemodynamic stability (avoid hypotension)
4. Aortocaval compression avoidance (left tilt/wedge)
5. Adequate anaesthesia (awareness prevention)

Foetal Safety Priorities

1. Avoid maternal hypoxaemia (direct effect on foetus)
2. Maintain uteroplacental perfusion (avoid hypotension)
3. Minimise vasopressor use (uteroplacental constriction)
4. Timely delivery (prolonged distress)

[25,26]

Communication and Documentation

Team Communication

Inform immediately:

• Surgeon (urgency, plan, time required)
• Midwife/nurses (preparation for alternative plan)
• Second anaesthetist (if available—assistance with difficult airway)
• Operating department assistant (equipment needs)
• Neonatal team (if foetal distress, prepare for resuscitation)

Clear statements:

• "The spinal has failed. I need 10 minutes to attempt an epidural, or we need to proceed with GA."
• "This is a category 2 section. I recommend converting to GA for maternal safety."
• "I need help with airway management. Please call the senior anaesthetist."

Documentation Requirements

Essential documentation:

• Timing of initial spinal and block assessment
• Sensory/motor level achieved
• Reason for failure (if known)
• Decision-making process
• Technique of second procedure (if attempted)
• Conversion to GA details (intubation grade, attempts, Cormack-Lehane)
• Airway equipment used
• Any complications
• Staff present
• Follow-up plan

ANZCA PS55 requirement: All anaesthetic complications documented in patient record and incident reporting system.

[27,28]

Indigenous Health Considerations

Aboriginal and Torres Strait Islander Peoples

Access and Communication:

Remote Indigenous women may face unique challenges in the event of failed spinal:

• Language barriers may complicate rapid informed consent for conversion to GA
• Cultural birth practices may influence acceptance of GA
• Family involvement: Decision-making often involves family members—brief time may not allow full consultation

Practical Recommendations:

1. Pre-procedure counselling: Discuss possibility of failed spinal and GA conversion during pre-anaesthetic consultation
2. Aboriginal Health Workers: Involve in explaining procedures and obtaining consent
3. Telemedicine: For remote units, video link to specialist anaesthetist for decision support
4. Airway expertise: Ensure remote practitioners maintain obstetric airway skills through simulation

Risk Considerations:

• Aboriginal women may have higher rates of some risk factors (obesity, diabetes, higher parity)
• Remote location means retrieval to tertiary centre may take hours if complications occur
• Low threshold for consultant involvement in high-risk cases

[29,30,31]

Māori Health Considerations

Whānau-Centred Decision Making:

When spinal fails and urgent decisions required:

• Time pressure vs whānau consultation: Balance urgency with cultural need for family involvement
• Clear communication: Explain risks/benefits of options in accessible language
• Māori Health Workers: Support communication and cultural safety
• Respect for birth preferences: Some Māori women may have strong preferences for vaginal birth or avoiding GA

Equity in Care:

• Ensure Māori women have equal access to senior anaesthetic expertise
• Address barriers to follow-up (transport, childcare)
• Coordinate with Māori Health Services for postnatal support

[32,33,34]

ANZCA Final Exam Focus

Key Viva Questions

Q: "A spinal anaesthesia for caesarean section has failed—there is no sensory block 15 minutes after injection. Outline your management."

Model Answer: "My immediate response would be to assess the urgency of the situation and the wellbeing of both mother and foetus. If this is a category one or two caesarean section with foetal distress or maternal haemorrhage, I would proceed immediately to general anaesthesia without attempting further regional techniques.

For a non-urgent case, I have several options depending on the clinical circumstances. If the original spinal was technically straightforward and this is clearly a technical failure with no cerebrospinal fluid obtained, I would consider a second spinal at a different interspace, typically one level higher, using seventy-five percent of the original dose to avoid high block if the first dose was partially absorbed. I would perform this with full aseptic technique, in the sitting position, and with general anaesthesia equipment immediately available.

Alternatively, if there's partial block or time permits, I might attempt conversion to epidural anaesthesia, which would take fifteen to twenty minutes to achieve surgical anaesthesia. However, if I've already made two attempts, or if the mother is becoming distressed, or if there's any deterioration in maternal or foetal condition, I would convert to general anaesthesia immediately."

Q: "Why is airway management more challenging in obstetric patients compared to the general population?"

Model Answer: "Obstetric patients present multiple physiological and anatomical changes that increase airway management difficulty ten-fold compared to the general population. Physiologically, pregnancy increases oxygen consumption by twenty to thirty percent while functional residual capacity decreases by twenty percent due to the gravid uterus elevating the diaphragm. This combination means desaturation occurs much more rapidly during apnoea—typically within two to three minutes versus four to five minutes in non-pregnant patients.

Anatomically, pregnancy causes airway mucosal oedema due to capillary engorgement, making the airway friable and prone to bleeding during manipulation. Weight gain of ten to fifteen kilograms and breast enlargement can make both mask ventilation and laryngoscopy technically difficult, particularly with standard laryngoscope handles that may abut the chest. The Mallampati score often worsens during labour due to fluid retention and airway oedema.

These factors combine to produce a difficult intubation rate of three to eight percent in obstetric patients compared to one and a half to six percent in the general population, with failed intubation occurring in approximately one in two hundred and fifty to one in five hundred obstetric general anaesthetics. This is why we emphasise neuraxial techniques, left uterine displacement, head-up positioning, and having experienced practitioners for all obstetric general anaesthetics."

Q: "You have attempted intubation twice in a pregnant patient for caesarean section under general anaesthesia. Each attempt has been grade 3 Cormack-Lehane view, and the patient is now desaturating to 85%. What is your management?"

Model Answer: "This is a can't intubate, can ventilate scenario, which requires immediate cessation of intubation attempts and maintenance of oxygenation as the priority. I would call for help immediately, ensure left uterine displacement is maintained with a wedge, and perform two-handed facemask ventilation with one hundred percent oxygen using an oropharyngeal airway if needed. The goal is to restore oxygen saturation above ninety percent.

Once oxygenated, I would insert a supraglottic airway device, preferably a ProSeal or Supreme LMA which has a gastric drainage channel. This provides a definitive airway in approximately ninety percent of cases and allows me to proceed with surgery if urgent, or wake the patient if not. I would not persist with further intubation attempts as more than three attempts significantly increase morbidity.

If I cannot ventilate via facemask or LMA, this becomes can't intubate, can't ventilate, and I must proceed immediately to emergency front of neck access using the scalpel-bougie-cricothyroidotomy technique. I would use a number ten scalpel to make a transverse stab through the cricothyroid membrane, rotate the blade, railroad a bougie into the trachea, and then pass a six millimetre cuffed tube over it. This is a life-saving procedure that cannot be delayed.

Throughout, I must communicate clearly with the surgeon about the airway status and proceed with surgery only if the airway is secure and oxygenation stable."

SAQ Practice Question

Question (20 marks): A 32-year-old woman (BMI 38, 36 weeks gestation, G3P2) is undergoing emergency caesarean section for foetal bradycardia. Your spinal anaesthesia has failed—there is no sensory block 15 minutes after injection. The surgeon is scrubbed and ready to proceed.

a) What are your immediate priorities and decision-making considerations? (6 marks) b) Describe your technique for converting to general anaesthesia, including airway considerations specific to obstetrics (8 marks) c) If intubation proves difficult (Grade 3 Cormack-Lehane view) after two attempts, what is your management? (6 marks)

Model Answer:

a) Immediate priorities and decision-making (6 marks):

Assessment:

• Foetal bradycardia = Category 1 or 2 urgency (foetal compromise)
• 15 minutes elapsed = adequate time for spinal to work; this is true failure
• BMI 38 = increased difficult airway risk, reduced FRC, rapid desaturation
• G3P2 = multiparous, potential for rapid delivery

Priorities:

1. Maternal safety: Cannot risk aspiration or hypoxia with repeated spinal attempts
2. Foetal wellbeing: Delay risks foetal hypoxia/acidosis
3. Time critical: Category 1-2 surgery needs delivery within 30 minutes ideally

Decision: Convert to general anaesthesia immediately

• No time for second spinal (positioning, preparation, onset = 20+ min total)
• No time for epidural (15-20 min to surgical anaesthesia)
• Category 1-2 indication takes priority over regional preference

Communication:

• Inform surgeon: "Spinal failed, proceeding with GA for safety"
• Call for help: Second anaesthetist if available
• Inform theatre team: GA setup needed urgently
• Ensure neonatal team ready for potential compromised baby

b) General anaesthesia technique and obstetric airway considerations (8 marks):

Preparation:

1. Positioning: Left lateral tilt 15-30° (wedge under right hip) to avoid aortocaval compression
2. Pre-oxygenation:
   • 100% O₂ for 3 minutes or 8 vital capacity breaths
   • Head-up 30° if possible (reduces aspiration risk, improves FRC)
   • Denitrogenation essential (reduced FRC = rapid desaturation)
3. Suction: Working suction under pillow
4. Equipment:
   • Short-handled laryngoscope (avoids breast compression)
   • Bougie, stylet, video laryngoscope if available
   • ProSeal LMA ready (rescue device)
   • Difficult airway cart available

Rapid Sequence Induction: 5. Cricoid pressure: 10N awake, 30N after loss of consciousness (modify if needed) 6. Induction:

• Thiopentone 4-5 mg/kg IV (traditional choice, cerebral protection)
• OR propofol 2-2.5 mg/kg (acceptable alternative)
• Caution: Reduced dose may be needed if hypovolaemic

7. Muscle relaxant:
   • Suxamethonium 1-1.5 mg/kg (fastest onset, 45-60 sec)
   • Ensure fasciculations complete before laryngoscopy
8. Intubation:
   • First attempt best attempt—most experienced practitioner
   • Optimal external laryngeal manipulation (backward-upward-rightward pressure)
   • Bougie ready for grade 2b-3 view
   • Video laryngoscopy if available (improgrades view)

Confirmation and maintenance: 9. Confirmation (mandatory before proceeding):

• ETCO₂ waveform (colour change insufficient)
• Auscultation bilaterally
• Chest rise
• No gastric inflation sounds

10. Maintenance:
    • 50% N₂O/50% O₂ + volatile (sevoflurane/isoflurane)
    • Reduces volatile requirement
    • Opioid after delivery (morphine/fentanyl)
    • Maintain left displacement until delivery

Specific obstetric considerations:

• Difficult intubation risk: 3-8% (vs 1.5-6% general population)
• Rapid desaturation: FRC reduced 20%, O₂ consumption increased 20-30%
• Aspiration risk: Full stomach, reduced LES tone, emergency surgery
• Mucosal oedema: Airway friable, easy bleeding, difficult view
• Breast enlargement: May impede laryngoscope insertion

c) Difficult intubation management (Grade 3 after 2 attempts) (6 marks):

Immediate actions:

1. STOP intubation attempts (>3 attempts increases morbidity significantly)
2. Call for help (most important step)
3. Maintain oxygenation (life before airway):
   • 100% O₂ via facemask
   • Two-person technique if needed (one holds mask, one squeezes bag)
   • Oropharyngeal airway
   • Maintain left displacement

Rescue airway: 4. Insert supraglottic airway (ProSeal or Supreme LMA):

• Grade 3 view suggests laryngoscope not achieving view
• LMA inserted blindly often succeeds where direct laryngoscopy fails
• Ventilate through LMA to restore oxygenation
• Gastric channel allows stomach decompression

Decision point: 5. Assess ventilation:

• Can ventilate via LMA:
  • If foetal bradycardia ongoing AND surgery urgent: proceed with LMA (accept aspiration risk vs further hypoxia)
  • If time permits: wake patient, proceed with regional or awake fibreoptic
• Cannot ventilate: Emergency front-of-neck access

Emergency front-of-neck access (CICV scenario): 6. Scalpel-bougie-cricothyroidotomy:

• #10 scalpel: transverse stab through cricothyroid membrane
• Rotate blade 90° (handle toward feet)
• Insert bougie alongside blade, direction toward lungs
• Railroad 6.0 cuffed ETT over bougie
• Remove bougie, inflate cuff, confirm ETCO₂
• Secure tube

Communication: 7. Inform surgeon of airway status 8. Proceed with surgery ONLY if:

• Airway secure (ETT or LMA with adequate ventilation)
• Oxygenation stable
• Foetal compromise ongoing

Post-procedure: 9. Document:

• Intubation attempts (Cormack-Lehane grade each time)
• Airway equipment used
• Rescue technique
• Staff involved
• Complications

10. Follow-up:
    • Review with patient
    • Document in anaesthetic record
    • Incident report if appropriate
    • Plan for future pregnancies (difficult airway alert)

Summary and Key Takeaways

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