Anaesthesia for Colorectal Resection

An overview of the process

Resection of a segment of colon or rectum with restoration of continuity by anastomosis, or formation of a stoma. What changes the anaesthetic is the surgical approach, how low the resection is, and whether a stoma is being formed.

Anastomotic leak is the complication that defines this surgery. Excess perioperative fluid produces bowel wall oedema and threatens the anastomosis. Bowel oedema = leak.

Open resection is managed supine with neuraxial analgesia. Laparoscopic and robotic resection may be managed in lithotomy with head-down tilt, where the position and the resection generates the risk.

Pre-op assessment

• Functional capacity and cardiorespiratory reserve. Assess frailty in the elderly.
• Anaemia is common in colorectal malignancy and is worth correcting before the day of surgery.
• Nutritional state and weight loss.
• Neoadjuvant chemoradiotherapy for rectal cancer produces fibrosis, a more difficult dissection and a longer operation.
• In inflammatory bowel disease, establish steroid and immunosuppressant use and nutritional state.
• Diabetes and glycaemic control.
• Fasting 6 hours for solids and 2 hours for clear fluids, with carbohydrate loading.
• Avoid long-acting anxiolytic premedication, particularly in the elderly.
• Venous thromboembolic risk is high — pelvic surgery, malignancy and reduced mobility.
• Consent covers general anaesthesia, the planned analgesic technique, blood loss, and for robotic cases the consequences of steep head-down positioning.

Induction and intra-operative management

• Volatile or TIVA.
• Monitoring should be scaled to the case. Standard monitoring is appropriate for a straightforward benign resection.
• An arterial line is indicated for open major resection, significant comorbidity, anticipated blood loss, or a prolonged robotic case in steep head-down tilt.
• Urinary catheter, core temperature monitoring, neuromuscular monitoring.
• Site all required access before the arms are tucked or the robot is docked. The patient is not reachable afterwards.
• Active warming with forced-air warming and a fluid warmer. Long open resections with an exposed abdomen lose heat rapidly.
• Single-dose antibiotic prophylaxis within 60 minutes of incision, redosed if prolonged.
• Mechanical thromboprophylaxis should be used if not contraindicated.
• Maintain deep neuromuscular blockade with train-of-four monitoring for laparoscopic and robotic work.

Positioning

• Lithotomy with head-down tilt is used for anterior resection and most laparoscopic and robotic colorectal work.
• Well leg compartment syndrome follows prolonged lithotomy with the legs elevated. Ask the surgeon to lower the legs periodically on long cases, and document the position and its duration.
• Pad the fibular head to protect the common peroneal nerve.
• Brachial plexus injury follows tucked arms and shoulder supports pressing on the plexus in head-down tilt. Avoid shoulder braces where possible.
• Confirm the patient is secure before tilting, and check again afterwards.
• Steep head-down tilt reduces pulmonary compliance and raises airway pressures, raises intracranial and intraocular pressure, and produces facial and airway oedema.
• Recheck tube position after tilting. Head-down tilt with pneumoperitoneum moves the carina cephalad and may produce endobronchial intubation.

Robotic resection

• Once the robot is docked the patient cannot be moved and must not move. Movement risks visceral or vascular injury from fixed instruments. Maintain deep neuromuscular blockade, monitored objectively, until undocked.
• Where the patient must be moved urgently, the robot must be undocked first. Establish who performs this before starting.
• Anticipate haemodynamic change at desufflation and on return to a neutral position.

Fluid management

• Goal-directed fluid therapy. Avoid fluid overload.
• Treat neuraxial hypotension with a vasopressor rather than repeated fluid boluses.

Perioperative analgesia

• Open resection: thoracic epidural or intrathecal morphine. Intrathecal morphine is used on this list for open panproctocolectomy as the primary analgesic component.
• Intrathecal morphine provides analgesia for approximately 24 hours. The plan for the second postoperative day must be made on the day of surgery.
• Intrathecal morphine requires a postoperative respiratory monitoring plan to be prescribed.
• Laparoscopic and robotic resection: epidural is not usually indicated. Transversus abdominis plane or rectus sheath blocks with port-site infiltration.
• Regular paracetamol.
• NSAIDs. The default is cautious use rather than avoidance. They may be used where renal function is adequate, the patient is euvolaemic and there is no specific contraindication. Greater caution applies after a rectal anastomosis.
• PONV prophylaxis with at least two agents.
• For prophylactic low molecular weight heparin, allow 12 hours from the last dose before siting or removing an epidural catheter and 4 hours afterwards; for treatment dose, 24 hours and 4 hours. Extend the interval if insertion was traumatic.

Post-operative care

• Most elective patients return to the ward on an enhanced recovery pathway. Escalate to HDU where indicated.
• Handover should include the resection performed, whether an anastomosis or stoma was formed, the approach and position, the analgesic technique and — where intrathecal morphine was used — the time it was given and the day-two plan, the dose of low molecular weight heparin and when the next is due, the fluid balance and the blood loss.
• Anastomotic leak commonly presents with tachycardia, new atrial fibrillation, fever, an ileus that does not resolve, rising inflammatory markers and pain out of proportion, before any radiological sign.
• Ileus is common. Early feeding and mobilisation reduce it.
• Delayed respiratory depression may follow intrathecal morphine.
• Well leg compartment syndrome presents as calf pain out of proportion after prolonged lithotomy. It is rare, catastrophic and missed where it is not considered.
• Other complications to anticipate are bleeding, acute kidney injury, and stoma complications with high output, dehydration and electrolyte loss.
• Early oral intake and mobilisation from the day of surgery. Prophylactic nasogastric intubation is not required.

References

1. Gustafsson UO, Rockall TA, Wexner S, et al. Guidelines for perioperative care in elective colorectal surgery: Enhanced Recovery After Surgery (ERAS) Society recommendations 2025. Surgery, 2025;184:109397.
2. Association of Anaesthetists of Great Britain & Ireland, Obstetric Anaesthetists' Association, Regional Anaesthesia UK. Regional anaesthesia and patients with abnormalities of coagulation.
3. Kietaibl S, Ferrandis R, Godier A, et al. Regional anaesthesia in patients on antithrombotic drugs: Joint ESAIC/ESRA guidelines. European Journal of Anaesthesiology, 2022;39:100–132.
4. Centre for Perioperative Care. Guideline for Perioperative Care for People with Diabetes Mellitus Undergoing Elective and Emergency Surgery, 2021, updated 2023.