Clinical Sciences and Anesthesia Practice
Preoperative assessment
Frame every preoperative question around three outputs: risk of the patient, difficulty of the airway, and the plan for the case. Functional capacity is the strongest simple discriminator - the ability to climb a flight of stairs or do heavy housework represents at least 4 METs and generally supports proceeding without further cardiac testing. Apply the ASA fasting intervals: 2 hours for clear fluids, 4 hours for breast milk, 6 hours for infant formula and a light meal, 8 hours for a fatty meal.
Machine, monitors, airway
The ASA machine check sequence - high-pressure leak test, low-pressure leak test, flowmeters, vaporizers, CO2 absorbent, breathing circuit, suction, ancillary equipment - is a favorite detail item. Continuous pulse oximetry, capnography, ECG, blood pressure, and temperature are standards; capnography is mandatory whenever an endotracheal tube or supraglottic airway is in place, because it is the most reliable confirmation of tube position and the earliest detector of disconnection or esophageal intubation.
Fluids and blood
Maintenance crystalloid for a 70 kg adult by the 4-2-1 rule is 40 + 20 + 50 = 110 mL/hr. Restrictive transfusion thresholds (generally hemoglobin 7–8 g/dL, higher for active ischemia) outperform liberal triggers in most trials.
Traps
Do not confuse difficult mask ventilation with difficult intubation - they are separate predictors with separate rescue plans. Do not assume an unobstructed airway because the patient is fasting; ileus and gastroparesis change the calculus. Do not treat the 4-2-1 rule as a resuscitation bolus.
Rule of thumb
If a plan cannot answer what you will do if the first attempt at the airway fails, the plan is incomplete.