Pre-anaesthetic Preparation
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Direct answer
Pre-anaesthetic preparation is the systematic process that converts a patient on the ward into a safe candidate on the table: history and examination, American Society of Anesthesiologists (ASA) physical status grading I to VI, airway assessment with the Mallampati class and the 2-4-6 fasting rule (clear fluids 2 hours, breast milk 4 hours, light solids and formula 6 hours, fried or fatty meals 8 hours), relevant investigations, informed consent, and premedication where indicated. On the technician's side it means a checked machine, working suction, a prepared airway tray and correctly sized monitoring leads. Most anaesthetic catastrophes examined in retrospect reveal a skipped step in exactly this phase, which is why Indian exams treat preparation as a mark-scoring numbered list.
What you must remember
- ASA grading: I healthy; II mild systemic disease without functional limitation; III severe systemic disease with functional limitation; IV severe disease that is a constant threat to life; V moribund, not expected to survive without surgery; VI brain-dead organ donor; the suffix E marks an emergency.
- Fasting (ASA guidance): 2 hours for clear fluids (water, black tea, pulp-free juice), 4 hours for breast milk, 6 hours for infant formula, light meals and non-human milk; 8 hours is the traditional margin for fried or fatty food — the rule applies to elective patients, never to emergencies, who are treated as having a full stomach.
- Airway assessment: Mallampati class I-IV (structures visible at mouth opening), thyromental distance below 6 cm, sternomental distance below 12-13 cm, inter-incisor gap below 3 cm, limited neck extension, and a history of difficult intubation all predict difficulty.
- Routine investigations in Indian practice: haemoglobin, blood group and crossmatch when bleeding is expected, serum creatinine and electrolytes in older or hypertensive patients, ECG, and serology (HIV, hepatitis B and C); chest X-ray and coagulation profile only when indicated.
- Premedication classics: glycopyrrolate 0.2 mg intramuscularly as antisialagogue, ranitidine 150 mg and metoclopramide 10 mg for aspiration-prone patients, and 30 mL of 0.3 molar sodium citrate immediately pre-operatively in obstetrics.
- Theatre readiness: machine check completed, suction switched on and under the pillow, airway trolley stocked, difficult-airway trolley location known, and the WHO Surgical Safety Checklist sign-in done before induction.
Working through a real pre-assessment
A 54-year-old woman for open chole-cystectomy arrives with hypertension on telmisartan and type 2 diabetes on metformin. The preparation unfolds as a checklist with clinical logic. She is ASA II. Fasting is confirmed: clear fluids stopped 2 hours prior, breakfast 8 hours ago. Her airway is assessed — Mallampati II, thyromental distance 6.5 cm, full neck extension — no difficulty predicted, but a bougie and one tube size smaller stay ready regardless, because prediction fails more often than examiners admit. Telmisartan is given with a sip of water; metformin is withheld, and her morning glucose is checked because a hypoglycaemic patient under general anaesthesia gives no warning symptoms. Haemoglobin, creatinine, ECG and a group-and-save sample are verified, and two units are crossmatched since open gallbladder surgery can bleed.
The technician's parallel list: machine self-test and circle-system leak check, sodalime inspected, airway tray with a 7.0 mm tube, working laryngoscope light, and suction catheters. In theatre, the sign-in — identity, site, consent, allergies, airway risk, blood availability — is read aloud before anything is injected. Ten structured minutes here is the cheapest safety investment in the entire perioperative period.
Where students slip
The commonest error is applying the fasting rule to the emergency patient: the 2-4-6 schedule is for elective fasting only, and every emergency, every obstetric patient and every patient with ileus or obstruction is a full stomach deserving rapid-sequence induction. The second slip is grading ASA by the disease label rather than functional limitation — a well-controlled diabetic on tablets is ASA II, while the same diabetic with nephropathy and limited effort tolerance becomes III. Third, Mallampati is quoted without the caveat that it must be done with the tongue maximally protruded, phonation absent, sitting upright; performed sloppily it systematically underestimates difficulty, and the exam answer pairs it with at least one other test rather than using it alone.
Frequently asked questions
What is the ASA physical status classification?
Six grades from I (healthy patient) through VI (brain death), with E appended for emergencies; it describes pre-operative fitness, not surgical risk or anaesthetic difficulty.
What are the standard pre-operative fasting hours?
Clear fluids up to 2 hours, breast milk 4 hours, light solids and formula 6 hours, and fried or fatty meals 8 hours before elective anaesthesia — emergencies are exempt and treated as full stomach.
Which bedside tests predict a difficult airway?
Mallampati class III-IV, thyromental distance under 6 cm, sternomental distance under 12-13 cm, inter-incisor gap under 3 cm, restricted neck extension and a receding chin; no single test is reliable alone.
Why is sodium citrate given before obstetric general anaesthesia?
It is a non-particulate antacid that immediately raises gastric pH, so that if aspiration occurs the fluid is less corrosive to the lungs; 30 mL of 0.3 molar solution is given in theatre.
Which cardiac drugs are continued on the morning of surgery?
Beta-blockers, alpha-2 agonists like clonidine and most antihypertensives are continued with a sip of water to avoid rebound ischaemia and hypertension; metformin and short-acting insulin are customarily withheld.