What is a pre-anaesthetic check-up and why is it done?
The pre-anaesthetic check-up (PAC) — also called the pre-anaesthetic or preoperative evaluation — is the visit at which the anaesthetist decides whether a patient is fit for the planned anaesthetic, what risks exist, and what must be done before the day of surgery. It is not a formality: most of the preventable anaesthetic disasters (aspiration, a failed airway, uncontrolled hypertension or diabetes on the table) are predicted at this visit.
- Assess risk — identify coexisting disease and grade overall fitness (ASA physical status).
- Predict a difficult airway — so equipment and a backup plan are ready before induction.
- Order only the tests that change management — not a routine panel for everyone.
- Optimise — control BP, sugar, bronchospasm, anaemia; continue or withhold medicines.
- Plan the anaesthetic — general vs regional, monitoring, postoperative bed (ward / HDU / ICU).
- Instruct — fasting (NPO) times, which drugs to take on the morning of surgery.
- Premedicate, explain and take informed consent — reduce anxiety and document the plan.
The ASA fasting guideline itself opens its preoperative-assessment recommendation with the same three tools: a review of pertinent medical records, a physical examination, and a patient survey or interview. That history and examination should cover ASA physical status, age, sex, type of surgery and the potential for difficult airway management, along with reflux, dysphagia and motility or metabolic disorders such as diabetes that raise aspiration risk.
What history and examination are included in a PAC?
| Area | What to ask | Why it matters |
|---|---|---|
| Previous anaesthesia | Problems with earlier anaesthetics; difficult intubation; PONV | Repeated airway difficulty; post-operative nausea risk |
| Family history | Relatives with problems under anaesthesia | Malignant hyperthermia is autosomal dominant — a close relative with an episode means a non-triggering anaesthetic (no volatile agents, no succinylcholine) |
| Cardiovascular | Chest pain, breathlessness, effort tolerance, recent MI or stent, syncope | Recent (< 3 months) MI/stent moves the patient to ASA IV |
| Respiratory | Asthma, COPD, smoking, recent upper respiratory infection, snoring/OSA | Bronchospasm, laryngospasm, post-op hypoxia |
| Endocrine / metabolic | Diabetes control, thyroid disease | Peri-operative glucose; aspiration risk from gastroparesis |
| GI / aspiration | Reflux, dysphagia, last meal | Decides fasting plan and need for aspiration prophylaxis |
| Drugs and allergies | All regular medicines, anticoagulants/antiplatelets, drug and latex allergy | What to continue, what to stop, what to avoid |
| Pregnancy status | Possibility of pregnancy in women of reproductive age | Fetal risk; pregnancy is itself an ASA II example |
Examination focuses on the airway (below), the cardiovascular and respiratory systems, the spine and back if regional anaesthesia is planned, venous access, and dentition (loose teeth, caps and dentures). Height and weight are recorded — weight for drug doses, and height for the predicted body weight used later to set ventilator tidal volumes.
How is the ASA physical status classification graded?
The American Society of Anesthesiologists (ASA) physical status classification is the single most-asked part of the PAC. It was introduced in 1941 (Saklad), revised in 1963, approved in its current form by the ASA House of Delegates in 2014 and amended in 2020 (StatPearls); the ASA has since published an updated statement with revised examples. It has six classes plus an 'E' suffix for emergencies.
| Class | ASA definition | Typical examples |
|---|---|---|
| ASA I | A normal healthy patient | Healthy, non-smoking, no or minimal alcohol use |
| ASA II | A patient with mild systemic disease | Current smoker, social drinker, pregnancy, obesity (30 < BMI < 40), well-controlled DM/HTN, mild lung disease |
| ASA III | A patient with severe systemic disease | Poorly controlled DM or HTN, COPD, morbid obesity (BMI ≥ 40), active hepatitis, implanted pacemaker, ESRD on regular dialysis, MI/CVA/TIA/stent > 3 months ago |
| ASA IV | Severe systemic disease that is a constant threat to life | MI/CVA/TIA/stent < 3 months, ongoing cardiac ischaemia, severe valve dysfunction, severe reduction of EF, sepsis, DIC, ESRD not on regular dialysis |
| ASA V | A moribund patient who is not expected to survive without the operation | Ruptured abdominal/thoracic aneurysm, massive trauma, intracranial bleed with mass effect |
| ASA VI | A declared brain-dead patient whose organs are being removed for donor purposes | Organ retrieval |
- Age is not part of ASA grading. An 80-year-old with no disease is still ASA I (StatPearls lists this as a limitation, since neonates and the elderly are more sensitive to anaesthesia).
- It is not a risk score for the operation. It grades the patient, not the surgery; procedure invasiveness and frailty also drive risk.
- Inter-rater variability is high, especially for age, anaemia, obesity and a history of MI.
- Pregnancy = ASA II in the ASA examples; morbid obesity (BMI ≥ 40) = ASA III.
How is the airway assessed during a PAC?
Every PAC must answer one question: can this patient be mask-ventilated and intubated? The bedside tests are cheap, quick and individually weak — so they are combined. The Mallampati classification grades how much of the oropharynx is visible with the mouth open and tongue protruded (sitting, no phonation); the other tests check mouth opening, jaw protrusion, thyromental distance and neck movement.
| Test | Concern when |
|---|---|
| Modified Mallampati | Class III (soft palate + base of uvula) or IV (hard palate only) |
| Mouth opening (inter-incisor gap) | Less than about 3 fingerbreadths |
| Thyromental distance | Less than 6 cm with the neck extended |
| Upper lip bite test | Class 3 — lower incisors cannot reach the upper lip |
| Neck mobility | Limited flexion/extension (e.g. cervical spondylosis, collar) |
| Look externally | Beard, short thick neck, obesity, receding mandible, prominent teeth |
Which investigations are needed before anaesthesia?
Modern guidance rejects a fixed 'routine panel'. NICE NG45 (Routine preoperative tests for elective surgery) ties testing to two things: the grade of surgery (minor, intermediate, major/complex) and the patient's ASA grade. For minor surgery (e.g. excising a skin lesion, draining a breast abscess) in an ASA I patient, NICE does not routinely recommend a full blood count, haemostasis tests, kidney function, ECG or lung function.
| Test | NICE NG45 recommendation |
|---|---|
| Chest X-ray | Do not routinely offer before surgery |
| Resting echocardiography | Not routinely; consider if a heart murmur and a cardiac symptom, or signs/symptoms of heart failure (do an ECG first) |
| Urine dipstick | Do not routinely offer |
| Sickle cell testing | Do not routinely offer — ask about personal and family history instead |
| HbA1c (no known diabetes) | Do not routinely offer |
| HbA1c (known diabetes) | Offer if not tested in the last 3 months |
| Pregnancy test | With consent, if there is any doubt whether the woman could be pregnant |
Tests are then added on clinical grounds — an ECG in a patient with cardiac disease or an ASA III–IV patient without a recent ECG, renal function in a patient at risk of acute kidney injury, coagulation in a patient on anticoagulants or with liver disease, and a haemoglobin before surgery with expected blood loss.
What are the ASA preoperative fasting (NPO) guidelines?
The ASA Practice Guidelines for Preoperative Fasting (2017) apply to healthy patients of all ages undergoing elective procedures under general anaesthesia, regional anaesthesia or procedural sedation. The old rule of 'nil by mouth after midnight' is not what the guideline says.
| Ingested material | Minimum fast |
|---|---|
| Clear liquids (water, pulp-free juice, carbonated drinks, clear tea, black coffee, carbohydrate drinks) — no alcohol | 2 hours |
| Breast milk | 4 hours |
| Infant formula | 6 hours |
| Non-human milk | 6 hours (behaves like a solid) |
| Light meal (e.g. toast and clear liquids) | 6 hours |
| Fried or fatty food, or meat | 8 hours or more |
- The guideline does not apply to procedures with no anaesthesia or local anaesthesia only, when airway reflexes are intact and there are no aspiration risk factors.
- It may need modification in patients with conditions that affect gastric emptying or fluid volume — for example pregnancy, obesity, diabetes, hiatus hernia, GERD, bowel obstruction or an emergency.
- Following the guideline does not guarantee an empty stomach — emergencies are managed as 'full stomach' with rapid sequence induction.
What is premedication and which drugs are used?
Premedication is drug treatment given before induction. In children the primary goal is anxiolysis; other aims include amnesia, attenuation of the stress response, vagolysis, reduced anaesthetic requirement, reduced secretions, anti-emesis and analgesia (PMC review of paediatric premedication).
| Goal | Agent(s) | Exam point |
|---|---|---|
| Anxiolysis, amnesia | Benzodiazepine — midazolam (oral in children 0.5–0.75 mg/kg, max 20 mg) | Most commonly used sedative premedicant in children; antegrade amnesia |
| Sedation (alternatives) | α2 agonists — clonidine, dexmedetomidine (e.g. intranasal); ketamine (IM for uncooperative children) | Dexmedetomidine causes bradycardia/hypotension at higher doses |
| Reduce gastric acidity/volume | H2 blockers, PPIs, non-particulate antacids (e.g. sodium citrate), metoclopramide | Only for patients at increased aspiration risk — not routine |
| Reduce secretions / vagolysis | Anticholinergics (e.g. glycopyrrolate) | Not recommended to reduce aspiration risk |
| Topical analgesia for cannulation | EMLA (2.5% lidocaine + 2.5% prilocaine), applied about 1 hour before | Causes venoconstriction and blanching |
How are patients optimised and which medicines are continued?
Optimisation means getting the patient to their best achievable state before an elective operation — controlling blood pressure and blood sugar, treating active wheeze, correcting anaemia and electrolytes, and timing surgery after recent cardiac events. When something reversible is found in an elective case, postponement is often the safest plan.
- Beta-blockers — continue. Withdrawal of beta-blockers in the perioperative period is associated with more adverse cardiovascular events and higher mortality.
- ACE inhibitors / ARBs — often withheld on the morning of surgery. In a randomised trial in elderly patients, discontinuing them was associated with fewer episodes of intraoperative hypotension and less vasopressor use.
- Anticoagulants and antiplatelets — individualised: balance bleeding risk against thrombosis, and check timing before neuraxial blocks.
- Diabetes — HbA1c within 3 months (NICE), plan peri-operative glucose management.
- Recent MI or coronary stent — under 3 months makes the patient ASA IV; elective surgery is usually deferred.
How do consent and documentation complete the PAC?
The PAC ends with informed consent for anaesthesia: the patient is told what anaesthetic is planned, the alternatives (for example regional instead of general), the common and serious risks, fasting and medicine instructions, and what to expect after surgery. In children, the explanation should be developmentally appropriate and the visit is also a chance to build rapport and reduce anxiety — family-centred approaches can lower the need for drug premedication.
- Record the ASA grade (with E if emergency) and the airway assessment.
- Write the anaesthetic plan and any special needs (difficult-airway cart, blood, ICU bed).
- Write explicit NPO times and the list of medicines to take or omit.
- Prescribe premedication and aspiration prophylaxis if indicated.
- Document consent and reassess the patient on the day of surgery.
What are the common exam traps on the pre-anaesthetic check-up?
- ASA ≠ age. A fit elderly patient can be ASA I.
- ASA ≠ surgical risk score. It grades the patient's systemic disease only.
- E is a suffix, not class VII. 'ASA IIE' = ASA II undergoing emergency surgery.
- ASA V vs VI: V is moribund and needs surgery to survive; VI is brain-dead (organ donor).
- BMI cut-offs: 30–40 = ASA II; ≥ 40 = ASA III.
- Fasting: clear liquids 2 h, breast milk 4 h, formula and non-human milk 6 h, light meal 6 h, fatty meal 8 h.
- Investigations: chest X-ray, urine dipstick and sickle tests are not routine before elective surgery.
- Aspiration prophylaxis is for at-risk patients; routine use in healthy patients is not recommended.