Lithotomy position and complications

Surgical approach (typical uses of lithotomy)

• Used to provide access to the perineum, anus, rectum, vagina/cervix, urethra/bladder
  • Common procedures: cystoscopy/TURBT/TURP, ureteroscopy, gynaecology (hysteroscopy, D&C, vaginal surgery), colorectal (haemorrhoids, fistula), obstetrics (operative vaginal delivery, repair).
• Patient positioned supine with hips flexed/abducted and knees flexed; legs supported in stirrups/boots; table may be Trendelenburg for pelvic exposure.
  • Variants: low lithotomy, standard, high lithotomy; Lloyd-Davies (often with steep Trendelenburg).
• Surgeon may request: steep head-down, perineal retraction, prolonged duration, intermittent leg movement, lithotomy with laparoscopy/robotics.

Anaesthetic management (overview)

• Type of anaesthesia: GA (common) or regional (spinal/epidural/CSE) depending on procedure; consider combined techniques for longer cases.
  • Regional advantages: reduced thrombotic risk, good analgesia; disadvantages: hypotension, masking of compartment syndrome/nerve injury pain, limited duration.
• Airway: ETT often preferred if steep Trendelenburg, pneumoperitoneum, long duration, obesity, aspiration risk; SGA may be acceptable for short, non-Trendelenburg cases with minimal insufflation.
  • Trendelenburg increases airway oedema risk; consider cuff-leak test if prolonged steep head-down.
• Duration: ranges from <30 min (cystoscopy) to 2–6+ h (complex pelvic/robotic). Risk of positioning injury rises with time (notably >2–4 h).
• Pain: often mild–moderate for endoscopic; moderate–severe for major pelvic/vaginal/colorectal surgery. Plan multimodal analgesia ± neuraxial/opioid-sparing techniques.
• Key anaesthetic priorities: haemodynamics, ventilation (esp. Trendelenburg), pressure area/nerve protection, VTE prophylaxis, documentation, and safe coordinated leg movement.

Definition and positioning principles

• Lithotomy: supine with hips flexed and abducted, knees flexed; legs supported in stirrups/boots; buttocks near table edge for perineal access.
• Core principles: symmetry, avoid excessive hip flexion/abduction/external rotation, avoid pressure on nerves/soft tissue, maintain access to airway/lines, and secure patient (esp. Trendelenburg).
  • Move both legs together (raise and lower simultaneously) to reduce hip/lumbar torsion and haemodynamic swings.
• Support type matters: boot stirrups distribute pressure and reduce peroneal nerve injury vs candy-cane supports (higher focal pressure at fibular head).

Physiological effects (FRCA core)

• Cardiovascular: raising legs increases venous return and may increase preload/CO; returning legs to supine can cause relative hypovolaemia and hypotension (especially if vasodilated/neuraxial).
  • Steep Trendelenburg: ↑ venous return/central venous pressure; may worsen cardiac failure and increase bleeding in head/neck.
• Respiratory: Trendelenburg + abdominal insufflation (lap/robotic) → ↓ FRC, ↓ compliance, ↑ airway pressures, V/Q mismatch; risk of atelectasis and hypercapnia.
  • Airway oedema risk increases with prolonged steep Trendelenburg and fluid loading.
• Neurological/ocular: Trendelenburg can increase ICP and IOP; rare risk of postoperative visual loss (more typical in prone but consider in prolonged steep head-down).
• Peripheral perfusion: elevation and external compression can reduce limb perfusion; prolonged high lithotomy increases risk of lower limb compartment syndrome.

Complications: overview (what to list in a viva)

• Nerve injuries: commonest positioning complication. Key nerves: common peroneal, femoral, sciatic, obturator, lateral femoral cutaneous, saphenous.
• Musculoskeletal: hip dislocation, back pain, muscle/ligament strain; rhabdomyolysis (rare).
• Vascular: DVT/PE; limb ischaemia; pressure-related vascular compromise; haemodynamic instability on leg movement.
• Compartment syndrome: well-leg compartment syndrome (WLCS) after prolonged lithotomy ± Trendelenburg.
• Skin/pressure injuries: sacrum, heels, calves, popliteal fossa; perineal pressure injury; genital oedema; eye/face oedema in Trendelenburg.
• Airway/respiratory: difficult ventilation in steep Trendelenburg; airway oedema; aspiration risk; endotracheal tube migration (cephalad carina shift).

Nerve injuries in lithotomy (high-yield details)

• Common peroneal nerve (most common): compression at fibular head against stirrup/candy-cane; presents with foot drop (dorsiflexion weakness) ± sensory loss over dorsum of foot/lateral shin.
  • Prevention: avoid pressure at fibular head, use boot supports, pad well, avoid excessive knee flexion/external rotation, check symmetry.
• Femoral nerve: stretch/compression from excessive hip flexion/abduction/external rotation or retractor pressure; weakness of knee extension (quadriceps), reduced patellar reflex, sensory loss anterior thigh/medial leg.
  • Prevention: limit hip flexion/abduction, avoid extreme lithotomy, ensure retractors not compressing psoas/femoral nerve region.
• Sciatic nerve: stretch with extreme hip flexion and knee extension; presents with weakness below knee (variable) and sensory changes posterior leg/foot.
  • Prevention: avoid combined hip flexion with knee extension; keep knees flexed; avoid extreme positions.
• Obturator nerve: excessive hip abduction or pelvic surgery; weakness of thigh adduction; medial thigh sensory loss (variable).
• Lateral femoral cutaneous nerve (meralgia paraesthetica): compression near ASIS/inguinal ligament from straps/positioning; sensory symptoms lateral thigh.
• Risk factors for nerve injury: prolonged duration, extremes of BMI (thin: less padding; obese: increased pressure), diabetes/peripheral neuropathy, smoking, hypotension, hypothermia, inadequate padding, steep Trendelenburg/robotics.

Well-leg compartment syndrome (WLCS) in lithotomy

• Definition: acute compartment syndrome in a limb without direct trauma, classically after prolonged lithotomy (often with Trendelenburg). Surgical emergency.
• Pathophysiology: reduced arterial inflow (leg elevation, hypotension) + impaired venous return (external compression) → ischaemia-reperfusion, capillary leak, rising compartment pressures.
• Risk factors: duration >4 hours (risk rises with time), high lithotomy, steep Trendelenburg, hypotension/vasoconstrictors, hypovolaemia, tight calf supports, obesity, peripheral vascular disease, long pelvic/robotic surgery.
• Clinical features (often post-op): severe leg pain (out of proportion), pain on passive stretch, tense swollen compartments, paraesthesia, weakness; pulses may be present (late sign).
• Diagnosis: clinical; compartment pressure measurement if uncertain. Do not delay treatment for tests if high suspicion.
• Management: urgent senior review and immediate fasciotomy; remove constriction, level limb (avoid elevation), optimise perfusion (oxygen, correct hypotension), treat rhabdomyolysis (fluids, monitor K+/CK, renal protection).
• Prevention: minimise time in lithotomy, periodic leg lowering (if feasible), avoid excessive elevation, use boot supports, avoid tight straps, maintain normotension/normovolaemia, active temperature management, document checks.

Airway and ventilation issues in Trendelenburg lithotomy (lap/robotic)

• Effects: cephalad diaphragm displacement → ↑ peak/plateau pressures, ↓ compliance; CO2 absorption → hypercapnia; facial/airway oedema; increased aspiration risk.
• Practical management: secure ETT well; consider pressure-controlled ventilation, PEEP, recruitment manoeuvres; monitor ETCO2 and adjust minute ventilation; limit fluids where appropriate; consider diuresis only if clinically indicated.
• Extubation considerations: assess for airway oedema (cuff leak, direct laryngoscopy if needed), head-up before extubation, ensure full reversal and readiness for reintubation.

Safe positioning checklist (what you say and do)

• Before induction (if possible): explain positioning risks; assess baseline neuropathy; consider documentation of pre-existing deficits.
• During positioning: move legs simultaneously; ensure hips not excessively flexed/abducted; knees flexed; neutral ankle; avoid pressure at fibular head and popliteal fossa; pad sacrum/heels; check genital/perineal pressure points.
• Lines/monitoring: ensure IV/arterial lines not kinked; check BP cuff/arterial trace after Trendelenburg; ensure access to airway and eyes protected (tape + lubrication).
• Intra-op: regular documented checks (e.g., every 30–60 min): limb position, padding, perfusion, pressure areas; consider lowering legs intermittently in long cases if feasible.
• End of case: return to supine gradually; anticipate hypotension; reassess limb position and skin; document any concerns; structured handover (position duration, Trendelenburg time, any issues).

Postoperative assessment and management of suspected positioning injury

• Early recognition: ask about numbness/weakness/pain in legs; examine motor and sensory function; inspect pressure areas.
• If nerve palsy suspected: remove ongoing compression, document findings, inform surgical team, consider neurology/physio referral; most are neuropraxia and recover over weeks–months, but exclude compressive haematoma or compartment syndrome.
• If WLCS suspected: treat as emergency—urgent surgical review for fasciotomy; analgesia should not delay diagnosis; monitor CK, renal function, electrolytes; manage rhabdomyolysis/hyperkalaemia.