Basic and Applied Sciences Relevant to Anesthesia
What you must understand
Build a working model of the airway, respiratory mechanics, circulation, and how drugs move through the body. Know the landmarks of the upper airway (oral cavity, pharynx, larynx, vocal cords, trachea, carina), the lobes of the lungs, and the segmental blood supply to the spinal cord. Understand oxygen delivery as the product of cardiac output and arterial oxygen content, and why anemia and low output both reduce it. For pharmacology, master pharmacokinetics (absorption, distribution, metabolism, clearance, half-life, context-sensitive half-time) and pharmacodynamics (receptors, potency, efficacy, dose-response). Know that potency is described by ED50 and that efficacy is the maximal effect-these are different concepts. For physics, understand the gas laws, vaporizer principles, flowmeters, and the difference between pressure and flow in a breathing circuit.
Traps in questions
Questions often swap potency and efficacy, or confuse MAC (a measure of potency for volatile agents) with awareness or with a concentration that guarantees unconsciousness. Another trap is confusing the oxyhemoglobin dissociation curve shift: right shift (higher P50) means easier unloading of oxygen to tissues, not better loading. Temperature, pH, and 2,3-DPG all shift the curve.
Rule of thumb
Use the Fick principle: oxygen consumption equals cardiac output times the arteriovenous oxygen content difference. If a patient is anemic or in low-output states, delivery falls even with normal saturation.