Pre-Surgical Risk: The Evidence Behind the Pathway

A 67-year-old retired bank clerk from Udupi is listed for an open cholecystectomy through an upper abdominal incision. The operation is expected to take two to three hours. He has hypertension, and type 2 diabetes on metformin and a sulfonylurea, and his oxygen saturation in room air is 97 per cent. The surgeon’s note says, “Physician’s fitness, please.” The intern asks you, “What do I actually write? Fit or not fit?” This is an illustrative case, not a real patient.

The Pre-Surgical Risk Pathway answers a better question than “fit or not fit”: how much risk, in which organ, and what can be done about it before the operation. It keeps every step, score, band, threshold and drug instruction it uses. What it leaves out is three pieces of physiology and epidemiology that explain why those steps are there. They are here, with the reasoning around them. By the end you will know why the most useful test for this man is a question about stairs, and why his lungs need a score too.

1. What the stair question is really measuring

Start with the unit. 1 MET = 3.5 mL O2/kg/min. Surgery imposes 4-6 METs of stress on a patient who has no way of declining it, so a patient who cannot reach 4 METs in ordinary life has no reserve left for the theatre. That is why this one bedside question predicts better than most laboratory tests.

In plain words, a MET (metabolic equivalent) is the oxygen the body uses sitting at rest. Surgery and the days after it ask the heart and lungs for four to six times that, whether the patient is ready or not. A patient who can climb a flight of stairs without stopping has shown that he can manage at least 4.

“So why not just do an echocardiogram?” Because an echo at rest tells you how the heart looks, not how much reserve it has. The stair question asks the patient to report his own exercise test, done every day of his life. The tool asks it this way: can you climb one flight of stairs without stopping, or walk 500 metres on the flat without breathlessness? Where the answer is unclear, the 2024 guideline prefers a structured questionnaire, the Duke Activity Status Index, with a score above 34 marking low risk.

This is where residents most often go wrong, and it is an honest mistake: they estimate the METs themselves, from how the patient looks on the bed. Subjective estimation performs poorly. Ask the question, and write down the answer.

2. Why every surgical patient is at risk of a clot

A clot in a vein needs three conditions, known together as Virchow’s triad: damage to the vessel wall, slow blood flow, and blood that clots more easily than it should. Surgery activates all three arms of Virchow’s triad: endothelial injury, stasis, and hypercoagulability. The incision injures vessels, the patient lies still on the table and in bed afterwards, and the body’s response to the operation makes the blood clot more readily.

That is why venous thromboembolism is the most preventable cause of in-hospital death, and why the tool scores every surgical patient with the Caprini model. The ASI guidelines recommend pharmacological thromboprophylaxis for a Caprini score of 3 or more.

“But I was taught that Indians rarely get clots.” Many of us were. That belief rests largely on series that never screened for clots, and under-prophylaxis remains a real problem on Indian surgical wards.

3. The lungs deserve a score too

Postoperative pulmonary complications are as frequent as cardiac ones and carry comparable mortality, yet most preoperative pathways score only the heart. ARISCAT changes that (Canet 2010). It predicts respiratory failure, infection, effusion, collapse of part of a lung, pneumothorax and bronchospasm from seven routine items, all of them already on the chart.

Work it for our bank clerk with the items the tool prints. Age 51 to 80: 3 points. Saturation 97 per cent: no points. No respiratory infection in the last month: none. Haemoglobin above 10 g/dL: none. Upper abdominal incision: 15 points. Duration 2 to 3 hours: 16 points. Not an emergency: none. His total is 34.

At 34 he is at intermediate risk, about one patient in eight. That is a reason to act, not to cancel: teach him chest physiotherapy and incentive spirometry before the operation, treat any active infection, ask for lung-protective ventilation, and lower the threshold for monitored care afterwards.

Back to the fitness note

So what does the intern write? Not “fit”. She writes what she found and what follows. He climbs two flights of stairs to his flat without stopping, so his functional capacity is at least 4 METs, and the stepwise algorithm says to proceed without further cardiac testing. His ARISCAT score is 34, intermediate, so he needs the lung measures before and after. His Caprini score decides his thromboprophylaxis. His metformin is held on the day of surgery only, and his sulfonylurea on the morning of surgery. That note helps the surgeon and the anaesthesiologist far more than one word.

Try this

An 82-year-old woman needs a hernia repair through a lower abdominal incision, expected to take one hour. Her saturation is 93 per cent. Work out her ARISCAT score as a planned operation, and again if it becomes an emergency. Illustrative case.

Answer. Age above 80: 16 points. Saturation 91 to 95 per cent: 8 points. A lower abdominal incision of one hour adds nothing. Planned, she scores 24, low risk. As an emergency she gains 8 points, 32 in all, which is intermediate. The same woman and the same operation carry a different pulmonary risk when the operation is rushed.

Take-home points

• Do not write “fit for surgery”; write the risk in each organ and what follows from it.
• Ask the stair question yourself; an estimate of METs from the bedside performs poorly.
• Every surgical patient meets all three arms of Virchow’s triad; score the clot risk every time.
• Postoperative pulmonary complications are as common as cardiac ones; score the lungs with ARISCAT.
• An intermediate or high score is a reason to prepare the patient, not to cancel.

Declaration: the author built and maintains the tool. It is free to use. The figures in this article are those the tool carried in its Evidence tab on 4 November 2026, each from the source the tool names. The illustrative cases follow the tool’s rules; check the tool’s result for a real patient.

References

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