Post-operative Complications

A framework

Post-operative complications are best organised by time since surgery, because timing narrows the differential faster than any other variable. A patient febrile on day 1 has a different list of likely problems from the same patient febrile on day 6, and being able to say why is what a good post-take ward round consists of.

Haemorrhage is classified separately by its own timing: primary during the operation, reactionary within 24 hours as blood pressure rises and clot or ligature slips, and secondary at 7 to 14 days from erosion of a vessel by infection.

Post-operative pyrexia

Fever after surgery is common and does not always mean infection. The five Ws are a genuinely useful mnemonic because they are ordered by the day on which each becomes likely.

Complications by system

Respiratory

• Atelectasis - collapse of alveoli from shallow breathing, retained secretions and diaphragmatic splinting. Prevented and treated by adequate analgesia (a patient who cannot cough because of pain will collapse their bases), sitting up, deep breathing and physiotherapy.
• Pneumonia - hospital-acquired, more common after upper abdominal and thoracic surgery, in smokers and in the frail
• Aspiration - at induction or extubation, or later in a patient with an ileus or impaired swallow
• Opioid-induced respiratory depression - a reducing respiratory rate with pinpoint pupils and drowsiness. Reverse with naloxone, and review the analgesic regimen rather than simply stopping all analgesia.
• Pulmonary oedema from fluid overload, particularly in older patients and those with cardiac or renal impairment
• Acute respiratory distress syndrome after major surgery, sepsis or massive transfusion

Cardiovascular and thromboembolic

• Myocardial injury after non-cardiac surgery - often silent, occurring in the first 48 hours, and detected only by a raised troponin. It is associated with a substantial increase in 30-day mortality, which is why unexplained tachycardia or hypotension deserves an ECG and a troponin rather than reassurance.
• New atrial fibrillation - common after major surgery, and frequently the first sign of an underlying problem such as sepsis, a leak, hypovolaemia or electrolyte disturbance. Treat the cause as well as the rhythm.
• Hypotension - the usual causes are hypovolaemia, bleeding, sepsis, epidural or spinal anaesthesia, and cardiac events. Examine the wound and the drains before assuming it is the epidural.
• Deep vein thrombosis and pulmonary embolism, despite prophylaxis. Maintain a low threshold for imaging, since D-dimer is almost always raised after surgery and is not usable.

Gastrointestinal

• Post-operative ileus - a degree of ileus is physiological after abdominal surgery. It becomes pathological if prolonged, and should then prompt a search for a leak, a collection, an electrolyte abnormality or excessive opioid use. Managed with nasogastric decompression if vomiting, correction of potassium and magnesium, opioid-sparing analgesia and early mobilisation.
• Anastomotic leak - see below
• Post-operative nausea and vomiting - very common, distressing, and preventable with risk-stratified prophylaxis (the Apfel score identifies female sex, non-smoking status, previous PONV or motion sickness, and post-operative opioids)
• Constipation, from opioids and immobility, which is a genuine cause of confusion and abdominal pain and is easily overlooked
• Clostridioides difficile infection after antibiotic prophylaxis or treatment
• Stress ulceration and upper gastrointestinal bleeding, in critically ill patients
• Adhesional obstruction - early after abdominal surgery, and a lifelong risk thereafter

Wound

• Surgical site infection - erythema, warmth, tenderness, discharge and dehiscence, typically day 5 to 7. Prevented by appropriate prophylactic antibiotics, glycaemic control, normothermia, skin preparation and good technique.¹
• Haematoma - a swollen, tense, painful wound, which may need evacuation and predisposes to infection. A neck haematoma after thyroid or carotid surgery is an airway emergency and the wound should be opened at the bedside.
• Seroma - a collection of serous fluid, common after mastectomy and hernia repair, usually managed conservatively
• Wound dehiscence - separation of the wound. Superficial dehiscence involves skin and subcutaneous tissue; full-thickness (burst abdomen) involves the fascia and may expose bowel.
• Incisional hernia, in 10 to 20% of midline laparotomies, more common after wound infection

Renal, urinary and metabolic

• Acute kidney injury - from hypovolaemia, sepsis, hypotension, nephrotoxic drugs and contrast. Review the fluid balance chart, the drug chart and the blood pressure, and stop the NSAIDs and ACE inhibitors.
• Urinary retention - very common after anaesthesia, spinal or epidural anaesthesia, pelvic and anorectal surgery, and with opioids and anticholinergics. Palpate and scan the bladder in any confused or agitated post-operative patient.
• Catheter-associated urinary tract infection, which is why catheters should be removed as early as possible
• Hyponatraemia, classically from excessive hypotonic fluid combined with post-operative ADH secretion
• Hypokalaemia and hypomagnesaemia, from gastrointestinal losses, which perpetuate ileus and provoke arrhythmia
• Hyperglycaemia in diabetic and non-diabetic patients, from the stress response, which impairs wound healing and increases infection risk
• Refeeding syndrome in malnourished patients restarted on nutrition

Neurological

• Post-operative delirium - common, particularly in older patients, and associated with longer stays, functional decline and mortality. It is not simply an effect of the anaesthetic: look systematically for pain, hypoxia, sepsis, urinary retention, constipation, electrolyte disturbance, alcohol or benzodiazepine withdrawal, and culprit drugs including opioids and anticholinergics.²
• Post-operative cognitive dysfunction, a more prolonged decline in memory and executive function
• Stroke, particularly after cardiac, carotid and major vascular surgery
• Peripheral nerve injury from positioning - the ulnar nerve at the elbow, the common peroneal nerve at the fibular head in lithotomy, and brachial plexus injury from arm abduction

Two complications worth knowing in detail

Anastomotic leak

Leakage of luminal contents from a surgical join, occurring in around 3 to 8% of colorectal anastomoses and more often in low rectal anastomoses. It is the complication that most often turns a routine recovery into a critical illness, and it is missed because the early signs are non-specific.

• Risk factors - a low rectal anastomosis, emergency surgery, male sex, obesity, smoking, malnutrition, steroids, diabetes, radiotherapy, poor blood supply and tension on the anastomosis
• Timing - classically day 5 to 7, but it may present earlier or, in a contained leak, considerably later
• Early features - unexplained tachycardia or new atrial fibrillation, a failure to progress, prolonged ileus, increasing rather than decreasing pain, a low-grade fever and a CRP that fails to fall or rises after day 3
• Later features - peritonism, faeculent or purulent drain output, sepsis and organ dysfunction
• Investigation - CT of the abdomen and pelvis with intravenous and rectal contrast is the test of choice. A normal CT in a patient who is clinically deteriorating does not exclude a leak.
• Management - resuscitation, broad-spectrum antibiotics, nil by mouth, and source control. A small contained leak in a stable patient may be managed with antibiotics and radiological drainage; a free leak with peritonitis requires laparotomy with washout and usually a defunctioning or end stoma.

Wound dehiscence and burst abdomen

Full-thickness dehiscence of a laparotomy wound occurs in around 1 to 3% of cases, typically on day 7 to 10, and carries a mortality of up to 25% because of the associated sepsis and the physiological state of the patient.

• The herald sign is a serosanguinous, pink, watery discharge from an apparently intact wound, sometimes described as salmon-coloured. This precedes the dehiscence and must not be dismissed as normal ooze.
• Risk factors - wound infection, malnutrition, obesity, diabetes, steroids, chronic cough, malignancy, jaundice, uraemia, smoking, raised intra-abdominal pressure and poor closure technique
• Immediate management if bowel is exposed - lie the patient flat, cover the wound with sterile saline-soaked gauze, give analgesia and intravenous fluids, keep nil by mouth, start broad-spectrum antibiotics, and call the surgical registrar for urgent return to theatre for resuture with deep tension sutures or a mass closure
• Do not attempt to push bowel back in on the ward

Assessing the deteriorating post-operative patient

1. A to E assessment with a full set of observations and a NEWS2 score, and escalate according to the score rather than to your impression
2. Establish the day since surgery, what operation was done and by whom, and read the operation note - the anatomy of the operation determines what can go wrong
3. Examine the wound and every drain, noting volume and character of output, and look at the abdomen properly rather than through a dressing
4. Review the observation chart as a trend, not as a snapshot. A heart rate that has crept from 70 to 100 over 12 hours is a more important finding than any single value.
5. Review the fluid balance chart - input, output, drains, nasogastric losses, and urine output over the last 24 hours
6. Review the drug chart - analgesia, antibiotics, thromboprophylaxis, and any drug that could be causing the problem
7. Bloods - FBC, U&Es, CRP, LFTs, a venous gas with lactate, blood cultures if febrile, and a troponin and ECG if there is unexplained tachycardia or hypotension
8. Imaging - chest radiograph, and a CT of the abdomen and pelvis with contrast where an intra-abdominal complication is suspected
9. Escalate early. The commonest failure in these patients is not a wrong diagnosis but a delayed one.

Red flags

Prognosis

Most complications are minor and self-limiting, but a small number account for the great majority of post-operative deaths. The pattern across audits is consistent: patients rarely die of the complication itself, they die of failure to rescue - the complication occurred, the signs were present, and the escalation was too slow.

This is why the recurring theme of surgical care is process rather than heroics. Prompt recognition of an unexplained tachycardia, a CRP that will not fall, or a wound that is weeping pink fluid is what separates a patient who has a CT and a stoma from one who has an emergency laparotomy in septic shock.

For the individual patient, the strongest determinants of outcome after a complication are the same as those before surgery: age, frailty, comorbidity and nutritional state. That is worth remembering because it points back to the pre-operative clinic. A significant share of post-operative complications is decided before the patient reaches theatre, and the anaemia, the smoking and the uncontrolled diabetes were all correctable then.