9.1 Preoperative History, Physical Examination & ASA Physical Status Classification
Key Takeaways
- The ASA Physical Status Classification categorizes baseline physiologic reserve and systemic disease severity rather than surgical risk: ASA 1 (healthy), ASA 2 (mild systemic disease without functional limitation), ASA 3 (severe systemic disease with functional limitation), ASA 4 (severe systemic disease that is a constant threat to life), ASA 5 (moribund patient not expected to survive 24 hours without surgery), and ASA 6 (brain-dead organ donor).
- The emergency modifier 'E' is appended when a delay in treatment significantly increases the threat to life or body part; 'E' can modify any classification (e.g., ASA 1E to ASA 5E).
- Functional capacity measured in Metabolic Equivalents of Task (METs) is an independent predictor of perioperative cardiovascular risk: 1 MET = 3.5 mL O₂/kg/min (basal resting metabolic rate); ≥4 METs (climbing a flight of stairs, walking 4 mph / 6.4 km/h) signifies adequate reserve, whereas >10 METs indicates excellent functional capacity.
- Preoperative airway assessment requires a multi-modal evaluation synthesizing Mallampati score (Class I–IV), thyromental distance (<6 cm predicts difficult laryngoscopy), inter-incisor opening (<3 cm), upper lip bite test (Class I–III), and cervical spine mobility (<35° extension).
- A focused organ system review establishes baseline neurologic, cardiopulmonary, renal, hepatic, and endocrine functional reserves to anticipate intraoperative hemodynamic instability and guide anesthetic technique.
Last updated: August 2026
9.1 Preoperative History, Physical Examination & ASA Physical Status Classification
The preoperative evaluation is the clinical cornerstone of anesthetic practice. Its primary objectives are to identify patient-specific comorbidities, determine physiological reserve, optimize chronic medical conditions, formulate an individualized anesthetic plan (general, neuraxial, peripheral nerve block, or monitored anesthesia care), and obtain informed consent. A structured preoperative assessment significantly decreases perioperative morbidity, mortality, and day-of-surgery case cancellations.
1. Components of the Comprehensive Preoperative Evaluation
An effective anesthetic assessment integrates the patient's medical history, prior anesthetic experiences, current pharmacotherapy, targeted physical examination, and selective diagnostic testing.
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| COMPONENTS OF THE PREOPERATIVE EVALUATION |
+-------------------+-----------------------------+-----------------------+
| History & Review | Airway & Physical Exam | Risk Stratification |
| - Medical/Surg Hx | - Airway classification | - ASA PS Class (1-6E) |
| - Anesthetic Hx | - Cardiopulmonary exam | - METs functional cap |
| - Allergies/Meds | - Baseline neurological | - Organ reserve |
| - NPO & Habits | - Vascular access sites | - Plan formulation |
+-------------------+-----------------------------+-----------------------+
Essential Historical Elements
- Personal and Familial Anesthetic History:
- Malignant Hyperthermia (MH): Personal or family history of unexplained perioperative cardiac arrest, rhabdomyolysis, hyperpyrexia, or masseter spasm (autosomal dominant RYR1 or CACNA1S receptor mutations).
- Pseudocholinesterase (Butyrylcholinesterase) Deficiency: History of prolonged apnea following succinylcholine or mivacurium administration.
- Difficult Airway History: Prior failed intubation, tracheostomy, emergency cricothyroidotomy, or dental trauma.
- Postoperative Nausea and Vomiting (PONV): Identification of Apfel risk factors (female gender, non-smoker, history of PONV/motion sickness, anticipated postoperative opioid use).
- Delayed Emergence: History of prolonged recovery due to metabolic, pharmacodynamic, or central nervous system dysfunction.
- Allergies vs. Adverse Drug Reactions:
- Differentiate true IgE-mediated anaphylaxis (bronchospasm, angioedema, urticaria, profound cardiovascular collapse) from non-allergic adverse effects (e.g., nausea from codeine, histamine release from rapid morphine/atracurium administration, muscle fasciculations/myalgia from succinylcholine).
- Document specific cross-reactivities: e.g., egg or soy anaphylaxis with propofol (rare, as propofol utilizes refined egg lecithin and soybean oil, but caution warranted in severe anaphylaxis), and amide vs. ester local anesthetic allergic mechanisms (esters metabolize to para-aminobenzoic acid [PABA], which is highly allergenic; amides rarely cause true allergy, often related to the preservative methylparaben).
- Substance Use & Lifestyle Factors:
- Tobacco: Number of pack-years, timing of last cigarette, presence of chronic bronchitis or emphysema.
- Alcohol: Frequency and quantity; risk of acute intoxication (decreased anesthetic requirements) vs. chronic heavy use (upregulated CYP2E1 enzymes, increased anesthetic requirements, alcohol withdrawal syndrome / delirium tremens 48–72 hours postoperatively).
- Recreational Drugs: Cocaine and amphetamines (acute intoxication causes massive sympathomimetic storm with risk of arrhythmias, ischemia, and hyperthermia; chronic abuse causes catecholamine depletion leading to severe refractory intraoperative hypotension).
- NPO Status and Aspiration Risk Assessment:
- Strict verification of the time and nature of the last oral intake (liquids, solids, fat content).
2. ASA Physical Status Classification System
The American Society of Anesthesiologists (ASA) Physical Status Classification System was originally introduced in 1941 to assess physical fitness and collect statistical data. It categorizes baseline physiologic reserve and systemic comorbidity severity. Crucial NCE Concept: The ASA PS score does not measure operative or surgical risk; rather, it reflects the patient's baseline physiological state at the time of assessment.
ASA Physical Status Definitions & Clinical Benchmarks
| ASA Class | Official ASA Definition | Adult Clinical Examples | Obstetric / Pediatric Examples |
|---|---|---|---|
| ASA 1 | A normal healthy patient | Non-smoking, no or minimal alcohol use, excellent exercise tolerance, no chronic medications | Healthy pediatric patient; non-pregnant adult |
| ASA 2 | A patient with mild systemic disease without substantive functional limitations | Current social cigarette smoker; social alcohol drinker; well-controlled HTN; well-controlled DM (no end-organ damage); mild asthma/COPD; BMI $30 - 39.9\text{ kg/m}^2$ | Normal, uncomplicated pregnancy; term infant without congenital defects |
| ASA 3 | A patient with severe systemic disease that results in substantive functional limitation; one or more moderate-to-severe diseases | Poorly controlled HTN or DM; symptomatic COPD; morbid obesity (BMI $\ge 40\text{ kg/m}^2$); active hepatitis; alcohol dependence/abuse; implanted pacemaker; moderate reduction in ejection fraction ($EF\ 35-49%$); ESRD on scheduled chronic dialysis; history ($>3\text{ months}$) of MI, CVA, TIA, or coronary stents | Preeclampsia without severe features; gestational diabetes poorly controlled; preterm infant $<37\text{ weeks}$ |
| ASA 4 | A patient with severe systemic disease that is a constant threat to life | Recent ($<3\text{ months}$) MI, CVA, or TIA; ongoing myocardial ischemia or severe valve dysfunction; severe reduction in ejection fraction ($EF < 30%$); sepsis; shock; DIC; acute respiratory distress syndrome (ARDS); ESRD not undergoing scheduled dialysis | Preeclampsia with severe features; peripartum cardiomyopathy with severe decompensation |
| ASA 5 | A moribund patient who is not expected to survive without the operation | Ruptured abdominal or thoracic aortic aneurysm; massive polytrauma with hemorrhagic shock; intracranial hemorrhage with midline shift and herniation; ischemic bowel with multiorgan failure | Uterine rupture with exsanguinating hemorrhage and profound shock |
| ASA 6 | A declared brain-dead patient whose organs are being removed for donor purposes | Certified brain death undergoing organ procurement | Certified brain-dead pediatric or adult donor |
| 'E' Modifier | Emergency procedure: Delay in surgical treatment would significantly increase the threat to life or body part | Appended to any class (e.g., ASA 1E for a healthy patient with acute appendicitis; ASA 3E for an end-stage diabetic with acute strangulated hernia) | Emergent stat cesarean delivery for acute fetal bradycardia in a healthy mother (ASA 2E) |
NCE Exam Trap — ASA Classification of Pregnancy & Morbid Obesity:
- Pregnancy: A normal, completely healthy pregnant woman presenting for elective cesarean delivery is classified as ASA 2 (not ASA 1) due to the profound, altered physiological state of pregnancy (increased blood volume, hypercoagulability, reduced FRC, elevated cardiac output).
- Obesity: A BMI of $30.0 - 39.9\text{ kg/m}^2$ is ASA 2; a BMI $\ge 40\text{ kg/m}^2$ is ASA 3.
- Timeframe for Vascular Events: An MI or CVA occurring $<3\text{ months}$ prior is ASA 4; an MI or CVA occurring $>3\text{ months}$ prior with stable recovery is ASA 3.
3. Functional Capacity & Metabolic Equivalents of Task (METs)
Functional capacity is a powerful, independent predictor of perioperative cardiovascular events and all-cause mortality. It is quantified using Metabolic Equivalents of Task (METs).
Metabolic Equivalent Fundamentals
This represents the basal resting oxygen consumption of a 70-kg, 40-year-old male in the resting, seated position.
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| FUNCTIONAL CAPACITY SPECTRUM (METs) |
+--------------------+----------------------------+-----------------------+
| Poor (<4 METs) | Moderate/Good (4-10 METs) | Excellent (>10 METs) |
| - Eating, dressing | - Climbing 1-2 flights | - Strenuous sports |
| - Walking indoors | - Walking 4 mph (6.4 km/h) | - Swimming laps |
| - Cannot climb 1 fl| - Scrubbing floors, golf | - Singles tennis, run |
+--------------------+----------------------------+-----------------------+
Clinical Tiers of Functional Capacity
| MET Tier | Functional Level | Clinical Activities & Benchmarks | Perioperative Significance |
|---|---|---|---|
| $< 4\text{ METs}$ | Poor | Self-care (eating, dressing, showering); walking 1–2 blocks on level ground at 2–3 mph ($3.2-4.8\text{ km/h}$); light housework (dusting, washing dishes); inability to climb a flight of stairs without stopping | High risk of perioperative myocardial ischemia, heart failure, and death; warrants further cardiac testing if high-risk surgery is planned |
| $4 - 10\text{ METs}$ | Moderate to Good | Climbing 1–2 flights of stairs without stopping; walking up a hill; walking on level ground at 4 mph ($6.4\text{ km/h}$); running a short distance; heavy housework (scrubbing floors, moving heavy furniture); recreational bowling or golfing without a cart | Indicates sufficient cardiopulmonary reserve to tolerate most noncardiac surgical stresses without invasive cardiac testing |
| $> 10\text{ METs}$ | Excellent | Participating in strenuous athletics (swimming, singles tennis, soccer, basketball, cross-country skiing, running/jogging $>5\text{ mph}$) | Extremely low risk of perioperative cardiac complications |
ACC/AHA Key Decision Point: If an asymptomatic patient with stable cardiovascular disease has functional capacity of $\ge 4\text{ METs}$, they can safely proceed to elective noncardiac surgery without further noninvasive cardiac stress testing, regardless of surgical invasiveness.
4. Focused Preoperative Airway Physical Examination
A thorough airway examination identifies anatomic features associated with difficult mask ventilation, difficult supraglottic airway (SGA) placement, difficult direct/video laryngoscopy, and difficult surgical cricothyroidotomy.
MALLAMPATI CLASSIFICATION (Sitting, Mouth Open, Tongue Protruded, NO Phonation)
Class I Class II Class III Class IV
+---------------+ +---------------+ +---------------+ +---------------+
| Soft Palate | | Soft Palate | | Soft Palate | | |
| Fauces | | Fauces | | Base of | | Hard Palate |
| Uvula | | Portion of | | Uvula | | Only |
| Tonsillar | | Uvula | | (NO Uvula | | |
| Pillars | | | | Tip) | | |
+---------------+ +---------------+ +---------------+ +---------------+
Airway Risk Predictors
- Modified Mallampati Score: Evaluated with patient seated upright, head in neutral position, mouth opened maximally, and tongue protruded without phonation:
- Class I: Soft palate, fauces, uvula, and anterior/posterior tonsillar pillars fully visible.
- Class II: Soft palate, fauces, and uvula visible (pillars masked by tongue base).
- Class III: Soft palate and base of uvula visible.
- Class IV: Hard palate only visible (soft palate completely hidden).
- Thyromental Distance (TMD): Measured from the thyroid notch to the inside tip of the mandibular mentum with the neck fully extended. A distance $<6.0\text{ cm}$ (or $<3$ fingerbreadths) indicates an acute anterior angle and poor mandibular space to displace the tongue during direct laryngoscopy.
- Inter-Incisor Gap (Mouth Opening): Measured between the incisor teeth. An opening $<3.0\text{ cm}$ ($<2$ fingerbreadths) impedes insertion of standard laryngoscope blades and SGA devices.
- Upper Lip Bite Test (ULBT / Mandibular Protrusion): Evaluates mandibular mobility:
- Class I: Lower incisors can bite the upper lip above the vermilion border.
- Class II: Lower incisors bite the upper lip below the vermilion border.
- Class III: Lower incisors cannot reach the upper lip (associated with difficult laryngoscopy).
- Neck Mobility: Normal cervical extension from neutral to full extension is $\ge 35^\circ$. Atlanto-occipital joint rigidity (e.g., severe osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, cervical spine fusion) prevents optimal "sniffing position" alignment (cervical flexion with atlanto-occipital extension).
5. Systematic Organ System Review
| System | Focus Areas | High-Yield Preoperative Flags |
|---|---|---|
| Cardiovascular | Ischemic disease, valvular stenosis/regurgitation, heart failure, arrhythmias, hypertension | Angina stability, orthopnea, paroxysmal nocturnal dyspnea (PND), lower extremity edema, presence of S3 gallop or systolic ejection murmurs |
| Pulmonary | Asthma, COPD, OSA, interstitial lung disease, recent URI | Baseline wheezing, home oxygen requirements, exercise tolerance, nocturnal snoring/apneic spells, cough with purulent sputum within past 4 weeks |
| Renal | Acute kidney injury (AKI), chronic kidney disease (CKD), hemodialysis | Baseline serum creatinine/BUN, baseline potassium, dialysis schedule (dialyze within 24 hours prior to surgery; verify dry weight and post-dialysis potassium) |
| Hepatic | Cirrhosis, portal hypertension, viral hepatitis | Ascites, jaundice, encephalopathy, coagulation factor deficiencies (elevated PT/INR), platelet sequestration from splenomegaly |
| Endocrine | Diabetes mellitus, thyroid disease, adrenal insufficiency | Glycemic control (HbA1c), signs of autonomic neuropathy (gastroparesis, resting tachycardia, orthostatic hypotension), chronic steroid use requiring stress dosing |
| Neurologic | Stroke/TIA, seizure disorder, neuromuscular disorders | Baseline motor/sensory deficits (document prior to regional blocks), ICP elevation signs, safety of succinylcholine in denervation/myopathy |
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Test Your Knowledge
A 54-year-old male with a history of hypertension well-controlled on amlodipine and a BMI of 34 kg/m² presents for an elective right inguinal hernia repair. He smokes 1 pack of cigarettes per day but has no dyspnea, wheezing, or functional limitations. He walks 3 miles daily without chest discomfort. What is his correct ASA Physical Status classification?
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B
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D
Test Your Knowledge
A 62-year-old female presents to the emergency department with a ruptured abdominal aortic aneurysm and severe hemorrhagic shock (blood pressure 68/40 mmHg, heart rate 138 bpm). She is rushed directly to the operating room for emergency open vascular repair. She is not expected to survive 24 hours without immediate surgical intervention. How should her physical status be classified?
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B
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D
Test Your Knowledge
Which of the following physical examination and history findings represents adequate functional capacity (≥4 METs) and the lowest independent predictor of perioperative cardiopulmonary morbidity?
A
B
C
D