Preoperative Evaluation

Preoperative Evaluation: Goals & Components - Setting the Stage

• Goals:
  • Identify patient risks, optimize conditions.
  • Formulate anesthetic strategy.
  • Obtain informed consent.
  • Reduce patient anxiety.
  • Minimize perioperative morbidity & mortality.
• Components:
  • History: Medical, surgical, anesthesia, drugs (📌AMPLE: Allergies, Medications, Past medical Hx, Last meal, Events leading to surgery), allergies.
  • Physical Exam: Systemic, vitals, airway (e.g., Mallampati).
  • Investigations: Indicated, not routine.
  • Risk Assessment: ASA status, functional capacity (METs).
  • Premedication & fasting guidelines.

⭐ ASA Physical Status Classification is a key predictor of perioperative risk and guides management.

Preoperative Evaluation: Patient Assessment - History & Exam Secrets

• History:
  • 📌 AMPLE: Allergies, Medications (anticoagulants, insulin, steroids, MAOIs), Past medical Hx (cardiac, resp, renal, hepatic, endocrine), Last meal (solids 6-8h, clear fluids 2h prior), Events leading to surgery.
  • Anesthetic Hx: Prior difficult intubation, Postoperative Nausea & Vomiting (PONV). Family Hx: Malignant hyperthermia, suxamethonium apnoea.
  • Functional Capacity: Metabolic Equivalents (METs); < 4 METs (e.g., cannot climb 1 flight of stairs) indicates poor reserve.
  • Habits: Smoking (advise cessation 4-8 weeks prior), alcohol, drug abuse.
• Examination:
  • Vitals (BP, HR, RR, Temp), BMI. Systemic: Cardiovascular (murmurs, JVP), Respiratory (air entry, wheeze).
  • Airway Assessment (Crucial for Safety):
    • 📌 LEMON:
      • Look externally (facial trauma, large incisors, beard, macroglossia).
      • Evaluate 3-3-2 rule: Inter-incisor gap (3 fingers), Hyoid-mental distance (3 fingers), Thyrohyoid distance/Thyroid cartilage to floor of mouth (2 fingers).
      • Mallampati classification (I-IV): Assesses tongue vs. pharyngeal space.
      • Obstruction (e.g., goiter, tumor, Ludwig’s angina, stridor).
      • Neck mobility: Full flexion & extension (atlanto-occipital joint extension >35°).
    • Thyromental Distance (TMD): Normal > 6.5 cm. If < 6 cm, suspect difficult laryngoscopy.
    • Inter-incisor Gap (Mouth Opening): Normal > 3 cm (or 2 large finger breadths).
    • Upper Lip Bite Test (ULBT): Class I (can bite upper lip above vermilion line), II (below vermilion), III (cannot bite).

⭐ A combination of Mallampati Class III/IV, Thyromental Distance (TMD) < 6 cm, and reduced neck movement (especially extension < 35°) significantly increases the likelihood of difficult intubation.

Preoperative Evaluation: Investigations & Risk - Numbers Game

• Selective Investigations (Not Routine):

  • ECG: Age >50y, cardiac Hx/disease, mod-high risk surgery.
  • Hb: Major blood loss expected; transfuse if <7-8 g/dL.
  • Creatinine: Baseline for RCRI.
  • Coagulation: Bleeding Hx, anticoagulants.

• Cardiac Risk:

  • Functional Capacity: METS <4 (e.g., can't climb stairs) = poor.
  • RCRI (Revised Cardiac Risk Index) - 1 point each:
    • High-risk surgery (vascular, intraperitoneal, intrathoracic)
    • Hx IHD
    • Hx CHF
    • Hx CVA/TIA
    • Preoperative Insulin Rx
    • Preoperative Creatinine >2 mg/dL
  • Stratify MACE risk using RCRI score:

• Pulmonary Risk:
  • Factors: Age, SpO2 <96%, recent RTI, anemia (Hb <10 g/dL), site (thoracic/upper abd.), duration >2h, emergency.
  • 📌 Smoking cessation: 4-8 weeks prior.

⭐ RCRI ≥1: Consider beta-blockers for high-risk surgery (start days before, not day-of).

Preoperative Evaluation: Fasting & Premeds - Final Prep Rally

• NPO Guidelines (📌 2-4-6-8 Rule): Clear liquids 2 hrs; Breast milk 4 hrs; Infant formula/Light meal 6 hrs; Fatty/Fried meal/Meat 8 hrs.
• Premed Goals: Anxiolysis, sedation, analgesia, amnesia, antisialagogue, aspiration prophylaxis (↑pH, ↓volume), blunt reflexes.
• Common Premeds:
  • Anxiolytics: Benzodiazepines (e.g., Midazolam).
  • Analgesics: Opioids (e.g., Fentanyl), NSAIDs.
  • Anticholinergics: Glycopyrrolate (↓secretions).
  • Antiemetics: Ondansetron.
  • Aspiration Prophylaxis: H2 blockers (Ranitidine), PPIs (Omeprazole), Sod. Citrate.
• Informed Consent: Essential; covers procedure, risks, benefits, alternatives. Patient capacity vital.
• Final Pre-op Check: Patient ID, surgical site, IV access, allergies reviewed.

⭐ Sodium citrate (0.3M solution, 15-30 mL) given 15-30 minutes before induction rapidly increases gastric pH without increasing volume, reducing aspiration risk.

High‑Yield Points - ⚡ Biggest Takeaways

• ASA physical status is vital for perioperative risk stratification.
• Mallampati score (I-IV) helps predict difficult intubation.
• NPO guidelines: 2h (clears), 4h (breast milk), 6h (light meal), 8h (fatty meal).
• Pre-op ECG if >50 yrs or with cardiac risk factors.
• Critical history: prior anesthetic complications (e.g., MH), allergies.
• Assess functional capacity (METs); >4 METs is generally good.
• Manage anticoagulants/antiplatelets balancing thrombotic vs. bleeding risks.