Prone Positioning for Surgery

Quick Answer

Prone positioning is essential for posterior spinal, neurosurgical, and some plastic/ENT procedures. Physiological effects: Reduced cardiac output (10-20% decrease), increased central venous pressure, decreased pulmonary compliance (30-35% reduction), and increased intra-abdominal pressure. Key concerns: Postoperative vision loss (POVL) from ischaemic optic neuropathy (0.05-1% incidence), endotracheal tube complications, brachial plexus and peripheral nerve injuries, pressure injuries, and abdominal compartment syndrome. Airway management: Secure fixation essential; risk of tube kinking, dislodgement, or endobronchial migration during turning. Positioning requirements: Proper support with chest rolls or Jackson table to allow abdomen to hang free; padding of all bony prominences; eye protection with no direct orbital pressure. Monitoring: Direct pressure on eyes must be avoided; check position every 20 minutes; maintain mean arterial pressure >65 mmHg. Emergency preparedness: Difficult CPR access; may require CPR in prone position or rapid supination; defibrillator pads placed anteriorly before turning. [1-25]

Indications and Surgical Access

Common Procedures Requiring Prone Position

Spinal Surgery:

• Posterior cervical decompression and fusion
• Thoracic and lumbar laminectomy/discectomy
• Posterior spinal instrumentation and fusion
• Scoliosis correction
• Vertebroplasty/kyphoplasty

Neurosurgery:

• Posterior fossa craniotomy
• Occipital craniotomy
• Cervical cord procedures
• Brainstem surgery

Other Specialties:

• Plastic surgery: Dorsal flap procedures, decubitus ulcer repair
• ENT: Transoral procedures, skull base surgery
• Orthopaedics: Posterior shoulder procedures
• Vascular: Lumbar sympathectomy

Positioning Variations

Standard Prone:

• Patient lies face down on operating table
• Head turned to side or supported in neutral position
• Arms at sides or on arm boards
• Hips and knees slightly flexed

Concorde Position (Reverse Trendelenburg Prone):

• Prone with head elevated
• Reduces venous congestion and bleeding
• Better surgical access for cervical spine

Knee-Chest/Jackknife:

• Hips flexed, knees on chest supports
• Abdomen hangs freely
• Excellent decompression of abdominal vessels
• Used for rectal/perineal surgery

Park Bench Position (Semi-Prone):

• Lateral decubitus with forward tilt
• Used for lateral cervical spine or combined approaches

Physiological Effects of Prone Positioning

Cardiovascular System

Hemodynamic Changes:

• Reduced venous return: Compression of IVC and abdominal veins when abdomen not free
• Decreased cardiac output: 10-20% reduction typically, up to 30% with abdominal compression
• Increased central venous pressure: CVP rises due to increased intrathoracic pressure
• Reduced stroke volume: Due to decreased preload
• Compensatory mechanisms: Tachycardia and increased systemic vascular resistance

Effect of Abdominal Compression:

• Without proper support: Significant abdominal compression occurs
• Increases intra-abdominal pressure to 15-30 mmHg or higher
• Further reduces venous return and cardiac output
• Elevates diaphragm, reducing FRC

Jackson Table Effect:

• Allows abdomen to hang freely between supports
• Minimizes cardiovascular compromise
• Maintains near-normal hemodynamics
• Gold standard for prolonged spinal procedures

Respiratory System

Mechanical Changes:

• Decreased compliance: Chest wall compliance reduced by 30-35%
• Increased airway pressures: Peak and plateau pressures rise
• Reduced FRC: Functional residual capacity decreases
• Diaphragm position: More cephalad with abdominal compression

Ventilation-Perfusion Matching:

• Prone position improves V/Q matching in ARDS
• In anaesthetized prone surgery: variable effects
• Dependent lung zones (anterior in prone) receive better perfusion
• May improve oxygenation in some patients

Prone vs. Supine in Healthy Patients:

• With proper positioning (Jackson table): Minimal respiratory impairment
• With abdominal compression: Significant impairment
• Obese patients: More severe respiratory compromise

Intra-Abdominal Pressure Effects

Measurement and Significance:

• Normal IAP: 5-7 mmHg
• Prone without support: 12-20 mmHg
• Abdominal compartment syndrome: >20 mmHg (some definitions >12 mmHg with organ dysfunction)

Consequences of Elevated IAP:

• Reduced renal perfusion and urine output
• Impaired venous return from lower extremities
• Reduced mesenteric and hepatic perfusion
• Increased airway pressures
• Risk of abdominal compartment syndrome in prolonged cases

Prevention:

• Use chest rolls or Jackson table (not both simultaneously)
• Position rolls under chest at nipple line
• Ensure abdomen hangs freely
• Consider IAP monitoring in prolonged high-risk cases

Airway Management

Endotracheal Tube Considerations

Secure Fixation:

• Tape ETT securely before turning prone
• Use waterproof tape or commercial fixation device
• Consider changing to nasal ETT for some procedures
• Armored (reinforced) ETT reduces kinking risk

Tube Positioning:

• Secure ETT to side of mouth, not midline
• Ensure no tension on tube after positioning
• Check ETT depth mark at teeth/lips before and after turning
• Confirm bilateral breath sounds after positioning

Kinking and Dislodgement Risk:

• Cervical flexion may cause tube kinking
• Excessively long ETT may advance into bronchus with neck flexion
• Movement during surgery may loosen fixation
• Edema may cause extubation difficulty

Airway Access in Prone Position

Limited Access:

• Oral access severely restricted once prone
• Laryngoscopy essentially impossible without turning supine
• Alternative airway devices must be immediately available

Supraglottic Airway Rescue:

• LMA can be inserted prone if ETT fails or dislodges
• Proseal or Supreme LMA provides better seal and gastric access
• Cannot intubate through standard LMA prone

Emergency Airway Management:

• If airway lost: Attempt LMA insertion
• If unsuccessful: Must turn supine for definitive airway
• This takes time and requires coordination
• Risk of surgical site contamination during emergency turn

Extubation Strategy

Before Turning Supine:

• Some centres extubate prone (controversial)
• Requires awake, cooperative patient
• Risk if reintubation needed
• Most centres turn supine before extubation

Supine Extubation:

• Turn supine carefully with surgical team
• Check leak around ETT (assesses airway oedema)
• Assess for tongue/facial oedema
• Extubate fully awake with intact reflexes
• Have difficult airway equipment ready

Postoperative Vision Loss (POVL)

Incidence and Mechanisms

Incidence:

• Overall POVL after prone surgery: 0.05-1%
• Ischaemic optic neuropathy (ION): Most common cause
• Central retinal artery occlusion (CRAO): Less common
• Cortical blindness: Rare

Ischaemic Optic Neuropathy (ION):

• Anterior ION: Anterior to lamina cribrosa, visible on fundoscopy
• Posterior ION: Posterior to lamina cribrosa, more common postoperatively
• Mechanism: Reduced perfusion to optic nerve
• Risk factors: Hypotension, anemia, prolonged duration, blood loss, Trendelenburg component, obesity

Pathophysiology:

• Elevated intraocular pressure (IOP) from prone positioning
• Reduced perfusion pressure = MAP - IOP
• Increased CVP transmitted to ophthalmic veins
• Venous congestion of optic nerve head
• Systemic hypotension further reduces perfusion

Risk Factors for POVL

Patient Factors:

• Male gender
• Obesity (BMI >30)
• Smoking history
• Hypertension
• Diabetes mellitus
• Vascular disease
• Anemia (hematocrit <30%)
• Small cup-to-disc ratio
• Glaucoma

Surgical/Anaesthetic Factors:

• Prolonged duration (>6 hours)
• Significant blood loss (>1000 mL)
• Hypotension (MAP <65 mmHg sustained)
• Trendelenburg positioning (worse with prone-Trendelenburg)
• Large fluid shifts/volume resuscitation
• Vasopressor use

Prevention Strategies

Positioning:

• Head position: Neutral, not dependent below heart level
• Reverse Trendelenburg: 10° head-up reduces venous congestion
• Headrest: Horseshoe or foam headrest avoiding orbital pressure
• Mayfield head holder: Three-pin fixation, no orbital contact
• Frequent checks: Verify eye position every 20 minutes

Hemodynamic Management:

• Maintain MAP >65 mmHg, higher in hypertensive patients
• Avoid prolonged hypotension
• Keep hemoglobin >80-100 g/L (consider >100 in high-risk)
• Arterial line for continuous monitoring
• Judicious fluid administration (avoid excessive crystalloid)

Surgical Considerations:

• Staged procedures if anticipated >6 hours
• Minimize blood loss
• Head elevation when surgically feasible
• Regular breaks to relieve pressure if possible

Monitoring:

• Direct visualization of eyes when feasible
• Mirror systems for continuous monitoring
• Ensure no direct orbital pressure
• Document eye checks regularly

Recognition and Management

Early Signs:

• Patient reports vision change on waking
• Unilateral or bilateral vision loss
• May be painless
• Variable visual field defects

Immediate Actions:

• Urgent ophthalmology consultation
• MRI/MRA to rule out cortical or vascular cause
• Optimize hemodynamics
• Consider IOP-lowering agents if elevated
• High-dose steroids (controversial for ION)

Prognosis:

• Variable; some recovery possible over weeks to months
• Permanent vision loss in many cases
• Early recognition and intervention may improve outcomes
• Prevention is paramount

Eye Protection and Orbital Safety

Proper Eye Protection Technique

Preparation:

• Apply lubricating eye ointment before positioning
• Ensure eyes fully closed with tape or shields
• No direct pressure on globe or orbit
• Protect from dependent edema and trauma

Head Support Options:

Horseshoe Headrest:

• Supports forehead and malar eminences
• Orbits hang free in center
• Risk: Movement can cause orbital contact
• Requires frequent monitoring

Foam Headrests:

• Conforms to face shape
• Cutouts for eyes, nose, mouth
• Risk: Facial edema may compress orbit
• Less stable than horseshoe

Mayfield Three-Pin Fixation:

• Rigid skull fixation
• No facial contact
• Best for prolonged procedures
• Pins penetrate scalp (bleeding risk)

Gardner-Wells Tongs:

• Traction pins in skull
• Can suspend head to relieve facial pressure
• Used with cervical spine cases

Corneal Protection

Corneal Abrasion Risk:

• Incidence: 0.1-1% in spinal surgery
• Mechanism: Lagophthalmos (incomplete eye closure), pressure, drying
• Presentation: Pain, foreign body sensation, photophobia
• Prevention: Lubrication, tape closure, protective shields

Prevention Measures:

• Apply ophthalmic lubricant (petrolatum-based)
• Tape eyelids closed horizontally
• Avoid vertical taping (may not fully close)
• Consider moisture chambers or goggles
• Check closure after final positioning

Management:

• Usually self-limiting
• Topical antibiotic prophylaxis
• Pain management
• Follow-up with ophthalmology if severe
• Most resolve within 24-48 hours

Pressure Injuries and Neuropraxia

Pressure Point Protection

Common Sites for Pressure Injuries:

• Face: Forehead, chin, cheekbones, ears
• Chest: Female breasts (especially large), sternum, ribs
• Pelvis: Anterior superior iliac spines, pubis
• Lower extremities: Patellae, toes, knees
• Upper extremities: Ulnar nerve at elbow, radial nerve at spiral groove

Pressure Injury Risk Factors:

• Prolonged procedure duration
• High BMI (increased tissue pressure)
• Large volume fluid resuscitation (edema)
• Diabetes (impaired healing)
• Peripheral vascular disease
• Malnutrition

Prevention Strategies:

• Gel or foam padding at all pressure points
• Redistribute pressure when possible (if procedure allows)
• Maintain normothermia (reduces tissue ischemia)
• Optimize perfusion (avoid hypotension)
• Preoperative skin assessment
• Postoperative skin inspection

Brachial Plexus Injury

Mechanisms:

• Stretch: Arm abduction >90°, external rotation
• Compression: Shoulder braces, direct pressure on plexus
• Ischemia: Prolonged compression impairs vasa nervosum
• Shoulder depression: Arm hanging off table

Risk Factors:

• Diabetes mellitus
• Hypertension
• Smoking
• Malnutrition
• Prolonged procedure
• Extreme arm positions

Prevention:

• Limit arm abduction to <90°
• Avoid external rotation at shoulder
• Support arms on padded arm boards at sides
• Shoulder braces: Place at acromion, not neck
• Document neurovascular status pre and postoperatively

Recognition and Management:

• Postoperative weakness, numbness, pain in distribution
• Usually neuropraxia (transient) vs. axonotmesis (prolonged)
• EMG at 2-3 weeks if not improving
• Physical therapy for rehabilitation
• Most resolve spontaneously over weeks to months

Peripheral Nerve Injuries

Ulnar Nerve:

• Most common perioperative nerve injury
• Compression at elbow (cubital tunnel)
• Prevention: Padding at elbow, neutral forearm position

Radial Nerve:

• Compression at spiral groove of humerus
• Risk with arm hanging over table edge
• Prevention: Adequate arm support

Common Peroneal Nerve:

• Compression at fibular head
• Risk with knee-chest position or leg holders
• Prevention: Padding at fibular head

Lateral Femoral Cutaneous Nerve:

• Compression at anterior superior iliac spine
• Meralgia paresthetica (pain/numbness lateral thigh)
• Prevention: Pad ASIS

Saphenous Nerve:

• Compression at medial tibial condyle
• Prevention: Padding at medial knee

Limb Complications and Compartment Syndrome

Compartment Syndrome

Pathophysiology:

• Elevated pressure within fascial compartment
• Reduced capillary perfusion
• Ischemia leads to edema, further increasing pressure
• Cycle continues causing muscle and nerve necrosis
• Rhabdomyolysis and renal failure may result

Risk Factors:

• Prolonged immobility in prone position
• External compression (improper positioning)
• Hypotension (reduced perfusion pressure)
• Obesity (increased tissue pressure)
• Increased muscularity
• Peripheral vascular disease

Clinical Presentation:

• Pain out of proportion to injury
• Pain with passive stretch of compartment
• Paresthesias
• Pallor (late sign)
• Pulselessness (very late sign)
• Paralysis (late sign)

Measurement:

• Intracompartmental pressure monitoring
• Delta pressure = diastolic BP - compartment pressure
• Delta <30 mmHg indicates compartment syndrome
• Clinical suspicion more important than numbers

Prevention in Prone Surgery:

• Adequate padding of all extremities
• Avoid prolonged knee-chest position
• Maintain perfusion pressure
• Check extremity position and pulses intraoperatively
• Document neurovascular status pre and postoperatively

Management:

• Emergent fasciotomy if compartment syndrome diagnosed
• Delay leads to irreversible muscle/nerve damage
• Nephrology consultation if rhabdomyolysis
• Aggressive fluid resuscitation to prevent renal failure

Rhabdomyolysis

Risk Factors in Prone Surgery:

• Prolonged operative time (>4-6 hours)
• Male gender (more muscle mass)
• Obesity
• Hypotension
• External compression

Diagnosis:

• Elevated creatine kinase (CK) >1000-5000 U/L
• Myoglobinuria (tea-colored urine)
• Elevated potassium
• Elevated creatinine (if renal involvement)

Prevention:

• Limit prone time when possible
• Adequate padding
• Maintain urine output >0.5 mL/kg/hr
• Consider CK monitoring in high-risk prolonged cases

Treatment:

• Aggressive IV hydration (maintain UO >100-200 mL/hr)
• Urine alkalinization (pH >6.5) with sodium bicarbonate
• Avoid diuretics until adequately hydrated
• Monitor electrolytes (hyperkalemia risk)
• Hemodialysis if refractory renal failure

Abdominal Compartment Syndrome

Pathophysiology

Definition:

• Sustained IAP >20 mmHg with new organ dysfunction
• Or IAP >12 mmHg with organ dysfunction in some definitions
• Grade I: 12-15 mmHg
• Grade II: 16-20 mmHg
• Grade III: 21-25 mmHg
• Grade IV: >25 mmHg

Causes in Prone Position:

• Abdominal compression without proper support
• Tight abdominal closures (previous surgery)
• Massive fluid resuscitation
• Ileus or bowel distension
• Retroperitoneal hematoma

Physiological Consequences:

• Reduced cardiac output (preload reduction)
• Increased airway pressures (diaphragmatic elevation)
• Reduced renal perfusion (oliguria/anuria)
• Reduced mesenteric perfusion (ischemia, bacterial translocation)
• Reduced cerebral perfusion (elevated CVP transmitted)
• Lower extremity venous stasis (DVT risk)

Monitoring and Prevention

Intra-Abdominal Pressure Monitoring:

• Intra-vesicular (bladder) pressure most common
• Transducer zeroed at mid-axillary line
• Instill 25 mL sterile saline into bladder
• Measure at end-expiration
• Perform in supine position ideally

Prevention Strategies:

• Use Jackson table or chest rolls (ensure abdomen free)
• Do not use chest rolls AND abdominal supports simultaneously
• Position rolls at nipple line
• Avoid excessive fluid resuscitation
• Consider prophylactic IAP monitoring in high-risk prolonged cases

Recognition:

• Increasing airway pressures
• Oliguria despite adequate hydration
• Increasing vasopressor requirements
• Metabolic acidosis
• Hypoxia/hypercapnia
• Rising CVP with falling cardiac output

Management

Non-Surgical:

• Evacuate intra-luminal contents (NGT, rectal tube)
• Evacuate extra-luminal fluid (paracentesis if ascites)
• Improve abdominal wall compliance (sedation, neuromuscular blockade)
• Optimize fluid management (avoid overload)
• Optimize organ perfusion (vasopressors as needed)
• Consider diuresis after adequate resuscitation

Surgical Decompression:

• Laparostomy (open abdomen) if medical therapy fails
• Indicated for: Grade IV ACS, organ failure progression, refractory acidosis
• Risk of complications: bleeding, infection, enteric fistula
• Delayed closure when IAP normalized

Cardiac Arrest and CPR in Prone Position

Challenges

Access Limitations:

• Cannot perform standard supine CPR
• Defibrillator pads placed anteriorly before turning
• Airway already secured (ETT in place)
• IV access may be limited
• Medication administration challenging

Time to Supination:

• Emergency turning takes 2-5 minutes with coordination
• Risk of surgical site contamination
• Risk of dislodging monitoring lines
• May be contraindicated with unstable spine

Anatomical Considerations:

• Direct cardiac compression through thoracic spine possible
• Different compressions technique required
• May be effective in some cases
• Not standard of care but may be life-saving

Management Strategies

Immediate Actions:

1. Confirm cardiac arrest (pulse check)
2. Call for help and emergency equipment
3. Ensure ETT secure and ventilating
4. Begin CPR if feasible in prone position
5. Prepare for emergency supination

Prone CPR Technique:

• Place heel of one hand on T6-T10 vertebrae
• Place other hand on top
• Compress with same force as supine CPR
• May generate adequate cardiac output
• Alternative: Malleable backboard under chest

Emergency Turning:

• Coordinate with surgical team
• Remove all sharp objects from field
• Maintain inline stabilization if spinal instability
• Turn as single unit (log roll technique)
• Resume standard CPR immediately when supine

Alternative Approaches:

• Some centres advocate staying prone for CPR
• Defibrillation can be performed prone (pads placed laterally)
• Thoracotomy with internal massage if open chest
• Consider if turning will cause catastrophic bleeding or spinal injury

Equipment and Positioning Devices

Jackson Spinal Table (Jackson Frame)

Design:

• Radiolucent frame for imaging capability
• Chest and iliac supports
• Abdomen hangs freely between supports
• Adjustable height and tilt

Advantages:

• Minimal abdominal compression
• Near-normal hemodynamics
• Excellent surgical access
• Reduced bleeding (less venous engorgement)
• Radiolucent for intraoperative imaging

Considerations:

• Patient must be transferred to/from frame
• Frame adds complexity to positioning
• May not be suitable for all patients (body habitus)
• Cost and storage requirements

Wilson Frame

Design:

• Adjustable frame creating kyphotic position
• Chest and hip supports
• Abdomen hangs in frame opening
• Adjustable angle (0-90°)

Advantages:

• Allows lumbar spine flexion for access
• Relatively simple to use
• Widely available

**Disadvantages:**n- May cause abdominal compression if not sized correctly

• Patient may slide cephalad
• Less hemodynamic stability than Jackson table
• May limit extreme Trendelenburg

Chest Rolls

Design:

• Cylindrical gel or foam rolls
• Placed longitudinally under chest
• Abdomen hangs between rolls
• Can use standard operating table

Placement:

• Position at nipple line level
• Align with mid-clavicular lines
• Width apart to allow abdomen to hang
• Ensure no compression of breasts (females)

Advantages:

• Simple and inexpensive
• Readily available
• Can use with standard table

Disadvantages:

• Less stable than Jackson table
• Risk of rolling off
• Potential for breast compression
• More abdominal compression than Jackson

Arm Positioning

Arm Boards:

• Arms abducted at 90° or less
• Prone with arms extended forward
• Risk of brachial plexus stretch
• Requires adequate padding

Arms at Sides:

• Tucked alongside body
• Reduces plexus stretch risk
• May limit surgical access
• Secure with drawsheet (avoid tape on skin)

Arms on Head:

• Arms flexed above head (surrender position)
• Used for some posterior cervical procedures
• High risk for ulnar nerve and brachial plexus injury
• Ensure adequate padding and limited time

Indigenous Health Considerations

Aboriginal and Torres Strait Islander Peoples:

Indigenous Australians experience disproportionate rates of spinal pathology requiring surgical intervention, including higher incidence of traumatic spinal injuries and degenerative conditions at younger ages. The social determinants of health, including higher rates of occupational injuries, motor vehicle accidents in remote areas, and delayed access to preventive care, contribute to this burden. When Indigenous patients present for spinal surgery in the prone position, these comorbidities create compounded risks.

Diabetes is significantly more prevalent among Aboriginal Australians, affecting approximately 18% of adults compared to 5% in non-Indigenous populations. This elevated rate increases susceptibility to pressure injuries, impairs wound healing, and increases infection risk. Diabetic neuropathy may mask early signs of positioning-related neuropraxia, delaying recognition of brachial plexus or peripheral nerve injuries. Preoperative optimization of glycemic control and meticulous attention to pressure point protection are essential.

Chronic kidney disease affects Aboriginal Australians at rates 5-10 times higher than the general population, creating significant implications for prone positioning management. The combination of renal impairment with potential abdominal compartment syndrome effects requires careful monitoring of intra-abdominal pressure and renal perfusion. Nephrotoxic agents should be minimized, and fluid management requires particular attention to avoid both overload and prerenal insults.

Visual impairment, particularly diabetic retinopathy, is more common in Indigenous populations. The risk of postoperative vision loss from ischaemic optic neuropathy adds to existing visual morbidity. High vigilance for POVL prevention, including maintaining adequate perfusion pressure and avoiding excessive fluid shifts, is particularly important.

Cultural safety in spinal surgery care involves recognizing that extended periods in the prone position with facial support devices may be distressing for patients who value face-to-face communication. Preoperative explanation and reassurance, potentially involving Aboriginal Health Workers, helps prepare patients. Family involvement in perioperative care decisions aligns with Aboriginal family structures and supports healing.

Māori Health Considerations:

Māori demonstrate similar patterns of health disparities, with higher rates of diabetes, obesity, and cardiovascular disease than non-Māori populations. These comorbidities increase the physiological stresses of prone positioning and the risks of cardiovascular decompensation, pressure injuries, and postoperative complications.

Obesity is particularly prevalent among Māori adults (48% vs 29% non-Māori), significantly increasing the risks associated with prone positioning. Elevated intra-abdominal pressure from obesity, combined with the prone position, creates substantial cardiovascular and respiratory compromise. The Jackson table or careful chest roll positioning is essential to allow the abdomen to hang freely and minimize these effects. However, body habitus may make optimal positioning challenging, requiring creative solutions and close hemodynamic monitoring.

Type 2 diabetes affects Māori at approximately twice the rate of non-Māori, with earlier onset and more severe complications. The combination of diabetes, obesity, and renal impairment creates a high-risk profile for prone spinal surgery. Whānau often wish to be present throughout the surgical journey, and accommodating family involvement in preoperative preparation and postoperative care aligns with Māori health models.

Postoperative vision loss would be particularly devastating in a population where healthcare access may already be compromised by geographic and socioeconomic barriers. Ensuring optimal hemodynamic management, careful positioning, and vigilant monitoring during prone surgery is essential for equitable outcomes.

ANZCA Exam Focus

Common Viva Topics

Physiology:

• Explain the cardiovascular effects of prone positioning and how they differ with and without abdominal compression
• Discuss the pathophysiology of postoperative vision loss (POVL) in prone surgery
• Describe the respiratory effects of prone positioning and how they impact ventilatory management
• Explain the mechanism and prevention of brachial plexus injury in prone positioning

Clinical Management:

• How would you position a patient for an 8-hour prone spinal fusion?
• Describe your strategy for preventing pressure injuries in prolonged prone surgery
• How would you manage a suspected compartment syndrome postoperatively?
• Outline your approach to a cardiac arrest occurring during prone surgery

Complications:

• What are the risk factors for ischaemic optic neuropathy in prone surgery?
• How do you prevent and detect endobronchial intubation in the prone position?
• Describe the recognition and management of abdominal compartment syndrome
• What is your emergency protocol for loss of airway in the prone position?

Assessment Content

SAQ 1: Positioning and Physiology (20 marks)

A 72-year-old male (BMI 38 kg/m²) is scheduled for posterior cervical decompression and fusion, expected duration 6 hours. He has hypertension, type 2 diabetes, and 30-pack-year smoking history.

a) Describe the physiological effects of the prone position on the cardiovascular system, comparing proper positioning (Jackson table) vs. improper positioning (abdominal compression). (6 marks)

b) What specific measures will you take to prevent postoperative vision loss (POVL) in this high-risk patient? (6 marks)

c) Outline your strategy for preventing pressure injuries and neuropraxia during this prolonged procedure. (8 marks)

Model Answer:

a) Cardiovascular effects of prone position:

Proper positioning (Jackson table):

• Abdomen hangs freely, minimal compression (1 mark)
• Cardiac output maintained near normal (1 mark)
• Venous return preserved (1 mark)
• CVP mildly elevated due to position (1 mark)

Improper positioning (abdominal compression):

• IVC compression reduces venous return (1 mark)
• Cardiac output reduced 20-30% (1 mark)
• Significantly elevated CVP (1 mark)
• Compensatory tachycardia and vasoconstriction (1 mark)
• Risk of abdominal compartment syndrome (1 mark)

b) POVL prevention measures:

• Position head neutral or 10° reverse Trendelenburg (1 mark)
• Use horseshoe headrest or Mayfield pins (no orbital pressure) (1 mark)
• Maintain MAP >65 mmHg (higher given hypertension history) (1 mark)
• Keep hemoglobin >100 g/L (1 mark)
• Minimize crystalloid; use colloids if large volume needed (1 mark)
• Check eye position every 20 minutes (1 mark)
• Consider staged procedure if >6 hours (1 mark)

c) Pressure injury and neuropraxia prevention:

Pressure injuries:

• Use Jackson table or chest rolls at nipple line (1 mark)
• Gel/foam padding at all pressure points (forehead, chin, ASIS, knees) (1 mark)
• Pad breasts medially in females (1 mark)
• Maintain normothermia (1 mark)
• Optimize perfusion (avoid hypotension) (1 mark)
• Document skin integrity pre and post (1 mark)

Neuropraxia prevention:

• Arms at sides or <90° abduction (1 mark)
• Shoulder braces (if used) on acromion, not neck (1 mark)
• Pad elbows (ulnar nerve) and fibular heads (peroneal nerve) (1 mark)
• Document neurovascular status pre and post (1 mark)

SAQ 2: Complications and Emergency Management (20 marks)

Four hours into a prone lumbar spinal fusion, the patient's airway pressure suddenly increases from 25 to 45 cmH₂O, SpO₂ drops to 88%, and EtCO₂ waveform shows reduced amplitude.

a) What is your differential diagnosis for this acute deterioration? (6 marks)

b) Describe your immediate management of this situation. (8 marks)

c) If this patient suffered a cardiac arrest in the prone position, outline your management strategy. (6 marks)

Model Answer:

a) Differential diagnosis:

• Endobronchial intubation (ETT advanced into mainstem) (2 marks)
• Kinked ETT (cervical flexion) (1 mark)
• Mucus plug or blood clot obstruction (1 mark)
• Pneumothorax (1 mark)
• Aspiration (1 mark)
• Displaced ETT (partial extubation) (1 mark)

b) Immediate management:

1. Call for help and alert surgeon (1 mark)
2. Increase FiO₂ to 100% (1 mark)
3. Check ETT position and connections (1 mark)
4. Pass suction catheter to assess patency (1 mark)
5. Auscultate chest for asymmetry or absent breath sounds (1 mark)
6. If endobronchial suspected: Withdraw ETT 2-3 cm and reassess (1 mark)
7. If no improvement and patient deteriorating: Prepare to turn supine (1 mark)
8. If kinked suspected: Adjust head position or change to armored ETT (1 mark)

c) Cardiac arrest in prone position:

Immediate actions:

• Confirm arrest, call for help (1 mark)
• Ensure ETT secure and ventilating (1 mark)
• Begin prone CPR if feasible (compressions over T6-T10) (1 mark)
• Coordinate emergency turning with surgical team (1 mark)
• Maintain spinal precautions if unstable spine (1 mark)
• Defibrillation can be performed prone (pads lateral) (1 mark)

References

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82. Alvine FG, Schurrer ME. Postoperative ulnar-nerve palsy. Are there predisposing factors? J Bone Joint Surg Am. 1987;69(2):255-259. PMID: 3818704