Robotic prostatectomy: physiology and positioning

Surgical approach

Typically robot-assisted laparoscopic radical prostatectomy (RARP) via transperitoneal approach
- Port placement (usually 5–6 ports), creation of CO₂ pneumoperitoneum, then robot docking (patient becomes difficult to access)
- Steep Trendelenburg (often 25–40°) with legs in lithotomy; dissection of prostate/seminal vesicles; control of dorsal venous complex
- Bladder neck division, prostate removal (endoscopic bag), vesico-urethral anastomosis; pelvic lymph node dissection may be added
- Drain +/-; urinary catheter left in situ post-op (often 7–14 days depending on local practice)

Anaesthetic management (overview)

Type of anaesthesia: General anaesthesia with controlled ventilation; regional techniques as adjunct for analgesia (e.g. intrathecal opioid, TAP block) depending on local practice
Airway: cuffed ETT mandatory (steep Trendelenburg + pneumoperitoneum → aspiration risk, high airway pressures, limited access after docking)
Duration: typically 2–4 hours (can be longer with lymph node dissection, obesity, previous surgery, learning curve)
Pain: usually moderate (less than open prostatectomy); main issues are visceral discomfort, port-site pain, shoulder tip pain from CO₂
Key constraints: after docking, access to airway/IV lines is restricted; patient position is fixed; emergency undocking takes time

Physiological effects: CO₂ pneumoperitoneum

Typical insufflation pressures 10–15 mmHg (higher pressures worsen cardiorespiratory effects)
Cardiovascular: ↑ SVR and MAP (catecholamines + mechanical effects), variable CO; ↓ venous return if high IAP/compression of IVC; vagal responses during peritoneal stretch can cause bradycardia/asystole
- CO may increase initially (autotransfusion from splanchnic bed) then fall with higher IAP/steeper Trendelenburg/limited preload reserve
- Arrhythmias: hypercarbia + vagal stimulation; treat cause (reduce IAP, deepen anaesthesia, anticholinergic if needed)
Respiratory: ↓ FRC and compliance, ↑ airway pressures, ↑ V/Q mismatch and atelectasis; CO₂ absorption → hypercarbia unless minute ventilation increased
- ETCO₂ rises; may need ↑ RR/VT, consider pressure-controlled ventilation, recruitment manoeuvres and PEEP
- In severe COPD/pulmonary HTN: hypercarbia can worsen PVR and RV strain
CNS/eye: CO₂ and Trendelenburg can ↑ CBF and ICP; ↑ IOP (risk in glaucoma/ocular pathology)
Renal/splanchnic: ↓ renal blood flow and urine output (IAP + neurohumoral); oliguria common intra-op and not necessarily hypovolaemia
Gas-related complications: subcutaneous emphysema, pneumomediastinum, pneumothorax; CO₂ gas embolism (rare but critical)

Physiological effects: steep Trendelenburg (with lithotomy)

Haemodynamics: ↑ venous return and CVP; may increase cardiac filling pressures without improving CO (especially with high IAP); facial/airway oedema risk with long cases
Respiratory: further ↓ FRC/compliance; cephalad diaphragm displacement; higher plateau pressures; increased atelectasis
Airway: ETT can migrate endobronchially with head-down positioning; check tube position after final positioning and after docking
CNS/eye: ↑ ICP and IOP; rare but important risk of postoperative visual loss (ischaemic optic neuropathy/CRAO) in prolonged head-down with raised venous pressure
Upper airway oedema: consider cuff leak test before extubation if prolonged steep Trendelenburg, large fluids, difficult airway, or obvious facial swelling
Lithotomy-specific: ↑ risk of DVT/PE; nerve injuries (common peroneal, femoral, obturator, sciatic); compartment syndrome (rare)

Positioning and access: practical implications of robotic docking

Before docking: secure two IV cannulae, arterial line if indicated, ensure all lines have extension tubing and are well labelled
Airway access becomes limited after docking: ensure ETT secured, bite block if needed, suction available, circuit connections tight, consider reinforced tube if local practice
Pressure areas: shoulder braces increase brachial plexus injury risk; prefer non-slip mattress/gel pads and careful strapping rather than hard braces
Arms: usually tucked; ensure neutral wrist/forearm, padding of ulnar nerve, avoid excessive shoulder abduction/external rotation
Head/eyes: protect eyes (taping + padding), avoid direct pressure; ensure head neutral to reduce venous congestion
Legs in lithotomy: pad fibular head; avoid extreme hip flexion/abduction; raise/lower legs together to reduce lumbar/hip injury and haemodynamic swings
Temperature: active warming (forced-air, warmed fluids) despite pneumoperitoneum-related heat loss

Ventilation strategy (typical approach)

Mode: volume-controlled or pressure-controlled; aim lung-protective ventilation (e.g. 6–8 mL/kg IBW), adjust for compliance changes
PEEP: often 5–10 cmH₂O (balance recruitment vs haemodynamics); consider recruitment manoeuvres after insufflation and after de-docking
CO₂ management: increase minute ventilation to maintain acceptable ETCO₂/PaCO₂; consider permissive mild hypercapnia case-by-case (avoid in raised ICP/pulmonary HTN)
Oxygenation: higher FiO₂ may be needed; treat atelectasis with recruitment/PEEP rather than excessive FiO₂ alone

Haemodynamic and fluid management

Monitoring: standard + consider arterial line for significant cardiorespiratory disease, expected long case, difficult access, or need for frequent ABGs
Haemodynamic goals: maintain organ perfusion; treat hypotension with vasopressors (phenylephrine/metaraminol/noradrenaline) rather than excessive fluids in head-down
Fluid: avoid liberal fluids (worsens facial/airway oedema); use goal-directed approach where available; accept low urine output intra-op if perfusion adequate
Bleeding: usually modest but can be significant (dorsal venous complex, pelvic sidewall); ensure group & screen/crossmatch per local policy

Analgesia and PONV

Multimodal: paracetamol + NSAID (if appropriate) + opioid titration; consider local infiltration at ports; TAP block may help port-site pain
Intrathecal opioid (e.g. diamorphine) sometimes used as adjunct; weigh benefits vs urinary retention is irrelevant (catheter), but pruritus/resp depression risk remains
PONV risk: laparoscopy + opioids; use prophylaxis (e.g. dexamethasone + ondansetron ± droperidol) and minimise volatile/opioid where possible

Extubation and postoperative care

Before extubation: assess for airway oedema (facial swelling, conjunctival oedema, difficult ventilation, long steep Trendelenburg, large fluids); consider cuff leak test and head-up time
Post-op destination: PACU usually; consider HDU/ICU for significant comorbidity, prolonged case, major physiological derangement, or complications
Complications to watch: shoulder tip pain, ileus, urinary leak, bleeding, DVT/PE, respiratory compromise/atelectasis

Key complications specific to RARP physiology/positioning

CO₂ gas embolism: sudden ↓ ETCO₂, hypoxia, hypotension, mill-wheel murmur (rare), arrhythmias/cardiac arrest
- Immediate actions: stop insufflation, release pneumoperitoneum, 100% O₂, call for help, support circulation, consider Durant position (left lateral head-down) and aspirate via CVC if present
Subcutaneous emphysema/pneumothorax: rising ETCO₂, crepitus, increased airway pressures; confirm (clinical/US/CXR) and treat (reduce IAP, ventilate, chest drain if tension/large)
Nerve/pressure injuries: brachial plexus (shoulder braces), ulnar nerve (tucked arms), common peroneal (lithotomy), femoral/obturator (hip flexion/abduction)
Rhabdomyolysis/compartment syndrome (rare): prolonged lithotomy, obesity, hypotension; post-op severe leg pain/swelling, dark urine, ↑ CK, hyperkalaemia
Ocular complications: corneal abrasion (commonest), raised IOP; rare visual loss—meticulous eye protection and avoid direct pressure

You are anaesthetising a patient for robotic prostatectomy. What are the main physiological consequences of combining pneumoperitoneum with steep Trendelenburg?

Structure answer by systems; emphasise additive effects and implications for ventilation and extubation.

Respiratory: ↓ FRC/compliance, ↑ atelectasis and V/Q mismatch, ↑ airway pressures; CO₂ absorption → ↑ PaCO₂/ETCO₂ requiring ↑ minute ventilation
Cardiovascular: ↑ SVR/MAP; venous return and filling pressures may rise but CO can fall at higher IAP or in limited cardiac reserve; vagal bradycardia during insufflation
CNS/eye: ↑ ICP/IOP due to hypercarbia + head-down venous congestion
Airway/face: venous congestion → facial, conjunctival and airway oedema; extubation risk
Renal: ↓ renal perfusion/urine output from IAP and neurohumoral responses; oliguria common

After insufflation the patient becomes profoundly bradycardic with hypotension. What is your differential and immediate management?

Think vagal reflex vs gas embolism vs anaesthetic depth vs haemorrhage; treat immediately while communicating with surgeon.

Immediate actions: call for help, stop insufflation, release pneumoperitoneum, check pulse/ECG, 100% O₂, deepen anaesthesia if light
Treat bradycardia: atropine/glycopyrrolate; if unstable consider adrenaline bolus per ALS
Differential: vagal response to peritoneal stretch (common), high IAP reducing venous return, CO₂ embolism (look for sudden ↓ ETCO₂), anaphylaxis, myocardial ischaemia, haemorrhage
If CO₂ embolism suspected: stop gas, deflate, Durant position, haemodynamic support, consider aspiration via CVC if present

How would you ventilate a patient during robotic prostatectomy to manage raised airway pressures and hypercarbia?

Demonstrate lung-protective strategy, recruitment/PEEP, and CO₂ control.

Use controlled ventilation via cuffed ETT; consider pressure-controlled ventilation to limit peak pressures while ensuring adequate tidal volume
Tidal volume ~6–8 mL/kg IBW; adjust RR to increase minute ventilation and control ETCO₂/PaCO₂
Apply PEEP 5–10 cmH₂O and recruitment manoeuvres after insufflation/positioning and before extubation (after de-docking) to reverse atelectasis
Check ETT position after steep Trendelenburg (risk of endobronchial intubation) if pressures rise or unilateral breath sounds
If persistent issues: ask surgeon to reduce insufflation pressure, ensure paralysis adequate, exclude pneumothorax/subcutaneous emphysema

What are the anaesthetic implications of robotic docking and how do you prepare before docking occurs?

Focus on loss of access and the need to anticipate problems.

Before docking: secure airway (ETT fixed), confirm ventilation; ensure two IV lines, extensions, and all monitoring functioning; consider arterial line if indicated
Positioning checks: eyes protected, head neutral, arms padded/tucked, pressure points padded, legs positioned safely in lithotomy
Plan for emergencies: agree undocking procedure and communication; ensure emergency drugs accessible; have suction and airway rescue equipment immediately available
After docking: access limited—avoid moving lines/circuit; frequent reassessment of airway pressures, ETCO₂, haemodynamics

What positioning injuries are associated with robotic prostatectomy and how do you prevent them?

Examiners want named nerves + mechanism + prevention.

Brachial plexus injury: shoulder braces + steep Trendelenburg traction; prevent by avoiding hard braces, use non-slip mattress/gel pads and careful strapping, keep shoulders neutral
Ulnar nerve: arms tucked with pressure at elbow; prevent with padding and neutral forearm/wrist position
Common peroneal nerve: compression at fibular head in lithotomy; prevent with padding and correct stirrup placement
Femoral/obturator/sciatic: excessive hip flexion/abduction/external rotation; prevent by limiting extremes and checking alignment
Compartment syndrome/rhabdomyolysis: prolonged lithotomy, obesity, hypotension; prevent by minimising duration, ensuring perfusion, careful positioning, consider staged leg lowering if prolonged
Eye injury/visual loss: corneal abrasion, raised IOP; prevent with taping/padding, avoid direct pressure, avoid excessive fluids, consider limiting duration of steep Trendelenburg where possible

At the end of the case the patient has marked facial swelling. How do you decide whether it is safe to extubate?

Demonstrate a structured extubation risk assessment and a plan if unsafe.

Risk factors: prolonged steep Trendelenburg, high fluid balance, obesity/OSA, difficult airway, high airway pressures, conjunctival oedema
Assess: head-up period, ensure normocapnia, check for cuff leak (imperfect but useful), inspect tongue/oropharynx if feasible, ensure full reversal and adequate respiratory mechanics
If concern: delay extubation, ventilate in theatre/PACU/ICU, consider steroid therapy per local practice, maintain head-up, diurese only if appropriate
If extubating: do so fully awake with airway rescue plan and equipment; consider extubation over an airway exchange catheter in high-risk cases

Describe the causes of a rising ETCO₂ during robotic prostatectomy and how you would manage it.

Split into increased production/absorption vs reduced elimination vs equipment issues.

Increased CO₂ load: absorption from pneumoperitoneum; worsened by high IAP, long duration, subcutaneous emphysema
Reduced elimination: hypoventilation (insufficient minute ventilation), increased dead space, V/Q mismatch/atelectasis, endobronchial intubation
Equipment: exhausted soda lime (if circle), rebreathing, sampling line issues
Management: increase minute ventilation; recruitment + PEEP; check tube position; examine for surgical emphysema; ask to reduce IAP; ABG if severe or discordant ETCO₂/clinical picture

What are the key differences in anaesthetic considerations between open radical prostatectomy and robotic prostatectomy?

Contrast pain/bleeding vs physiology/positioning constraints.

Robotic: pneumoperitoneum + steep Trendelenburg → major respiratory mechanics changes, hypercarbia, raised IOP/ICP, airway oedema; restricted access after docking
Open: usually more pain and higher blood loss risk; less hypercarbia/position-related airway oedema; easier access to patient throughout
Analgesia: open often benefits from epidural/neuraxial; robotic often managed with multimodal + local blocks