Preanesthetic Assessment and Preparation
Assessment and preparation
Preanesthetic evaluation identifies risk, optimizes comorbidity, and creates a plan. Obtain a focused history: prior anesthetics and complications, difficult airway, malignant hyperthermia, drug allergies, medications, substance use, exercise tolerance, and family history. Examine the airway: mouth opening, thyromental distance, Mallampati, neck mobility, dentition, and signs of obstruction. Review cardiovascular and pulmonary status, renal and hepatic function, and neurologic disease. ASA physical status classifies fitness, not procedural risk: ASA 1 healthy; ASA 2 mild systemic disease; ASA 3 severe systemic disease; ASA 4 severe disease that is a constant threat to life; ASA 5 moribund; ASA 6 brain-dead organ donor. Emergency status is denoted by E.
Fasting reduces aspiration risk: clear fluids 2 hours, breast milk 4 hours, infant formula and nonhuman milk 6 hours, and a light meal 6 hours; fatty or fried meals may require longer. Routine preoperative testing is not indicated for every patient; order tests based on history, physical findings, and procedure risk. Continue beta-blockers and most chronic medications; manage anticoagulants and antiplatelets with a procedure-specific plan. Document informed consent, including alternatives and risks, and ensure appropriate NPO instructions and site marking.
Traps and a rule
Traps include misclassifying ASA 3 as "severe" versus "mild" disease, ordering indiscriminate testing, stopping beta-blockers abruptly, and assuming all clear fluids are prohibited after midnight. Another trap is relying on a single airway test to predict difficulty.
Rule of thumb: an asymptomatic patient with well-controlled hypertension on a stable regimen and no end-organ damage is usually ASA 2; if there is significant end-organ damage or poorly controlled disease, consider ASA 3. Use the highest applicable category and add E for emergency.