07 / Anaesthesia · Assess
The pre-operative clinic
Fifteen minutes at a bedside that decide how the next four hours go. 10 patients to grade, 18 drugs to decide, the 6 cardiac risk factors to count, and a fasting clock that starts from the list time.
ASA physical status
Grade the patient
A 24-year-old non-smoker for a knee arthroscopy. Runs twice a week. No medication.
The grades, with the society’s own examples
- I A normal healthy patient. Healthy, non-smoking, no or minimal alcohol use.
- II Mild systemic disease without substantive functional limitation. Current smoker; Social alcohol drinker; Pregnancy; Obesity with a BMI of 30 to 40; Well-controlled diabetes or hypertension; Mild lung disease.
- III Severe systemic disease with substantive functional limitation. Poorly controlled diabetes or hypertension; COPD; Morbid obesity, BMI 40 or above; Active hepatitis; Alcohol dependence; A pacemaker; Moderately reduced ejection fraction; End-stage renal disease on regular dialysis; A heart attack, stroke, TIA or coronary stent more than three months ago.
- IV Severe systemic disease that is a constant threat to life. A heart attack, stroke, TIA or coronary stent within the last three months; Ongoing cardiac ischaemia or severe valve dysfunction; Severely reduced ejection fraction; Sepsis; Disseminated intravascular coagulation; End-stage renal disease not on regular dialysis.
- V A moribund patient not expected to survive without the operation. Ruptured abdominal aortic aneurysm; Massive trauma; Intracranial bleed with mass effect; Ischaemic bowel with multi-organ failure.
- VI A patient declared brain-dead whose organs are being removed for donation. Organ retrieval.
The patient’s own drugs
Continue, hold, or stop?
Monoamine oxidase inhibitors
The whole table
- Beta blockersContinue, Including the morning of surgery. Stopping causes rebound tachycardia and ischaemia. Starting them the day before surgery is worse than either.
- StatinsContinue, Throughout. Plaque stabilisation; withdrawal is associated with more perioperative cardiac events.
- ACE inhibitors and angiotensin receptor blockersHold the dose, The morning of major surgery. Refractory hypotension at induction that does not respond to the usual pressors. Restarted once the patient is euvolaemic. Practice varies; many continue them for minor surgery.
- DiureticsHold the dose, The morning of surgery. A fasted patient does not need to be made drier. Potassium is checked.
- AspirinContinue, In almost all patients, and always with a coronary stent. The bleeding risk is small; the thrombotic risk of stopping is real. Stopped only for intracranial and some prostate surgery, by agreement.
- Clopidogrel, prasugrel, ticagrelorStop in advance, 7 days before (5 for ticagrelor), only with the cardiologist's agreement. A recent stent needs both antiplatelets; surgery is deferred rather than the drugs stopped. Without a stent, the bleeding risk decides.
- WarfarinStop in advance, 5 days before, INR checked to be 1.4 or below. Bridged with heparin only in the highest-risk patients: a mechanical mitral valve, a recent venous thromboembolism.
- Rivaroxaban, apixaban, dabigatranStop in advance, 48 hours before for standard bleeding risk, 72 hours for high; longer with renal impairment. No bedside test and no simple reversal for all of them. Renal clearance sets the interval, dabigatran most of all.
- MetforminHold the dose, The morning of surgery if eating and drinking will be missed; otherwise continue. Lactic acidosis if the kidneys are hit by hypotension or contrast. Restarted with the first meal.
- SGLT2 inhibitors (empagliflozin, dapagliflozin)Stop in advance, 3 days before surgery. Euglycaemic ketoacidosis: the sugar looks normal while the patient is acidotic. Check ketones if unwell after surgery.
- GLP-1 agonists (semaglutide, liraglutide)Hold the dose, A week before for weekly preparations, the day before for daily ones. Delayed gastric emptying: a fasted patient can have a full stomach. If not held, treat as full and consider a rapid sequence induction.
- InsulinContinue, Basal insulin continued at about 80 percent the night before; prandial doses omitted while fasting. Never stop insulin in type 1 diabetes. A variable-rate infusion covers a long fast or major surgery, with glucose checked hourly.
- Long-term steroids (prednisolone 5 mg or more for over three weeks)Continue, The usual dose, plus hydrocortisone 100 mg at induction for major surgery and an infusion or 50 mg six-hourly after. A suppressed adrenal cannot mount the stress response: unexplained hypotension after surgery in a steroid patient is an Addisonian crisis until treated.
- InhalersContinue, Including on the morning of surgery, brought to the anaesthetic room. An asthmatic who has missed their morning dose is the one who bronchospasms at intubation.
- Combined oral contraceptive and HRTStop in advance, 4 weeks before major surgery, with alternative contraception; or continue with full thromboprophylaxis. Venous thromboembolism. The decision is made at the pre-operative visit, not the day before.
- LithiumHold the dose, 24 hours before major surgery; continue for minor. Fluid shifts change the level and lithium prolongs neuromuscular block. Levels are checked.
- Monoamine oxidase inhibitorsContinue, With specialist advice, and the anaesthetist told. Pethidine and indirect sympathomimetics such as ephedrine can cause a hypertensive or serotonergic crisis; the anaesthetic is planned around them.
- Herbal preparations: garlic, ginkgo, ginseng, St John's wortStop in advance, 2 weeks before. Bleeding for the first three, and enzyme induction for St John's wort, which changes the dose of everything else.
Revised Cardiac Risk Index
Count the factors
30-day major cardiac event
3.9%
Low risk
Functional capacity, the other half
- 1 METEating, dressing, sitting at a computer
- 2 METsWalking slowly on the flat
- 4 METsClimbing a flight of stairs or a hill, walking briskly, heavy housework
- 6 METsA round of golf carrying the clubs, dancing
- 10 METsRunning, swimming lengths, singles tennis
Below four METs, or a score of two or more, before major surgery earns a conversation about optimisation and objective testing.
The fasting clock
Set the time the list starts
- until 06:30Clear fluids: water, pulp-free juice, black tea or coffee, oral rehydration solutionEncouraged until two hours before. Prolonged fasting does not empty the stomach further; it dehydrates the patient and worsens the induction hypotension. Many paediatric units now allow clear fluids until one hour before.
- until 04:30Breast milkEmpties faster than formula.
- until 02:30Formula milk, cow's milk, a light mealToast and tea counts as a light meal. Milk in a drink makes it a meal.
- until 00:30A large or fatty mealFat slows gastric emptying; so do pain, opioids, trauma, pregnancy, diabetes and bowel obstruction, and those patients are treated as full whatever the clock says.
- at inductionChewing gum and sweetsRemoved before induction. Gum increases gastric volume a little; the evidence does not justify cancelling a case for it.
The rule is two, four, six: two hours for clear fluids, four for breast milk, six for everything else. Sip until sent.
What to order
Tests that change the plan, and the ones that never did
- Full blood countMajor surgery; any surgery with expected blood loss; ASA III or above; anaemia symptoms. The haemoglobin sets the transfusion plan and finds the anaemia that should be treated before elective surgery, not during it.
- Urea and electrolytesMajor surgery; ASA III or above; diuretics, ACE inhibitors, lithium, digoxin; kidney disease; diabetes. Potassium and creatinine change the drugs given and the fluids planned.
- ElectrocardiogramASA III or above for any surgery; ASA II with cardiovascular, renal or diabetic disease for intermediate or major surgery; age above 65 for major surgery. A baseline to compare against when a postoperative trace looks abnormal, and the occasional finding that changes the plan.
- Coagulation screenAnticoagulants; liver disease; a bleeding history; before a neuraxial block in these patients. A screen in an unselected patient finds nothing that the bleeding history did not.
- Group and save, or crossmatchBy the surgical blood ordering schedule for the operation. Two units crossmatched for a hip; a group and save for a hernia; six units and a massive transfusion plan for an aneurysm.
- Chest radiographNot routinely. New respiratory signs or symptoms, or as a baseline before thoracic surgery. Age and smoking alone do not justify it.
- Pregnancy testAny person who could be pregnant, with consent, on the day. The anaesthetic, the drugs and the radiation all change.
- HbA1c and glucoseDiabetes, or suspected diabetes. An HbA1c above 69 mmol/mol is a reason to defer elective surgery and optimise.
- Echocardiogram or a cardiopulmonary exercise testPoor or unknown exercise tolerance before major surgery; a murmur not previously investigated; heart failure. Objective reserve when the corridor stairs cannot be climbed or the story is unclear.