preanaesthetic check up
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I now have comprehensive content from Barash's Clinical Anesthesia. Let me compile a thorough, well-structured answer.
Pre-Anaesthetic Check-Up (Preanesthetic Evaluation)
The pre-anaesthetic check-up (PAC) is a structured assessment performed before any surgical procedure requiring anaesthesia. Its goals are to reduce patient risk and morbidity, prepare the patient medically and psychologically, and promote efficient, safe perioperative care. The Joint Commission and the American Society of Anesthesiologists (ASA) both mandate this evaluation for all surgical patients.
1. Goals of the PAC
- Identify medical risk factors that could complicate anaesthesia
- Formulate an optimal anaesthetic plan tailored to the patient
- Optimise the patient's health before surgery
- Obtain informed consent for anaesthesia
- Educate the patient about the perioperative course
- Reduce OR cancellations and unnecessary costs
2. Components of the PAC
A. Patient Identification and Planned Procedure
- Full name, date of birth, medical record number
- Sex, gender identity, preferred pronouns
- Diagnosis and nature of the planned surgical procedure
- Urgency classification (elective, urgent, emergency)
- Emergency cases allow less time for evaluation and carry higher anaesthetic risk
- Advanced directives and code status
B. Vital Signs and Anthropometry
- Height, weight, BMI
- Blood pressure, heart rate, respiratory rate, temperature, SpO2
- NPO (nothing by mouth) status - critical for aspiration risk
3. History
A. Anaesthetic and Surgical History
- Previous surgeries and anaesthetics, and how the patient tolerated them
- Any history of difficult airway (this is paramount)
- History of malignant hyperthermia (MH) - a "drug allergy to anaesthesia" reported by the patient or family should raise MH suspicion
- History of postoperative nausea and vomiting (PONV)
- Any adverse reactions to anaesthetic agents
B. Medical History - Systems Review
| System | Key Points to Assess |
|---|---|
| Airway | Difficult intubation history, obstructive sleep apnoea (OSA), teeth, mouth opening |
| Pulmonary | Asthma, COPD, URI, smoking, bronchodilator/steroid use, OSA, cough, dyspnoea |
| Cardiovascular | Hypertension, CAD, CHF, valvular disease, dysrhythmias, pacemaker, pulmonary hypertension, angina, syncope, exercise tolerance |
| CNS | Stroke, seizures, raised ICP, psychiatric disorders, neuromuscular disease, spinal cord injury |
| GI/Hepatic | Liver disease, hepatitis, reflux/GERD, bowel obstruction, nausea/vomiting, alcohol use |
| Renal | Insufficiency, failure, dialysis dependence |
| Haematology | Anaemia, coagulopathy, sickle cell disease, prior transfusions, chemotherapy |
| Endocrine/Metabolic | Diabetes mellitus, thyroid disease, steroid use, rheumatoid arthritis |
| Infectious | TB, viral illness, foreign travel, antibiotic-resistant organisms |
| Other | Pregnancy (gestational age), trauma history, latex allergy |
C. Medications
- All prescription drugs, OTC medications, herbal supplements, and illicit drugs
- Check for potential drug interactions with anaesthetic agents
- Assess need for stress-dose steroids (chronic steroid users)
- Note any anticoagulants, antiplatelets - may need bridging
D. Allergies
- Drug allergies with nature of reaction (rash vs. anaphylaxis)
- Latex allergy (check for associated fruit allergies: banana, kiwi, avocado)
- Previous transfusion reactions
4. Physical Examination
A. Airway Assessment (Most Critical)
This is the single most important part of the physical exam:
| Parameter | What to Assess |
|---|---|
| Mallampati class | I-IV, predicts difficulty of laryngoscopy |
| Mouth opening | Inter-incisor distance (normal >3 cm) |
| Thyromental distance | Normal >6.5 cm |
| Neck mobility | Extension range (flexion/extension) |
| Ability to prognath | Lower jaw protrusion (Upper Lip Bite Test) |
| Dentition | Loose/carious/protruding teeth, dentures |
| Neck circumference | Large neck is a predictor of OSA and difficult intubation |
B. Cardiovascular Examination
- Heart sounds (murmurs, gallops, rubs)
- Peripheral perfusion, capillary refill
- JVP, oedema, hepatomegaly
- Peripheral pulses
C. Respiratory Examination
- Auscultation (wheeze, crepitations)
- Respiratory rate, SpO2
- Signs of COPD, hyperinflation
D. Other Systems
- Neurological: baseline mental status, focal deficits
- Back/spine: relevant for regional anaesthesia (scoliosis, prior lumbar surgery, infections)
- Intravenous access sites
5. Exercise Tolerance Assessment
Exercise tolerance is a significant predictor of cardiac risk. It is expressed in metabolic equivalents (METs):
- Poor functional capacity (<4 METs): unable to climb a flight of stairs or walk on level ground at 4 mph - high risk
- Good functional capacity (>4 METs): generally reassuring for perioperative cardiac events
6. Preoperative Investigations
Investigations should be ordered based on positive findings from history and physical examination, or anticipated intraoperative physiologic changes (e.g., major blood loss). Routine blanket ordering is not recommended.
| Investigation | Indication |
|---|---|
| CBC/Haemoglobin | Suspected anaemia, major surgery with expected blood loss |
| Electrolytes/Creatinine | Renal disease, diuretic use, DM, cardiac disease |
| Blood glucose/HbA1c | Diabetes mellitus |
| Coagulation (PT/PTT/INR) | Anticoagulant use, liver disease, coagulopathy |
| Liver function tests | Hepatic disease, alcohol use, suspected liver pathology |
| ECG | Age >40 (males), >50 (females), known/suspected cardiac disease, hypertension |
| Chest X-ray | Known cardiopulmonary disease, suspected malignancy, not routine |
| Pulmonary function tests | Significant respiratory disease (asthma, COPD), lung resection surgery |
| Echocardiography | Known/suspected valvular disease, CHF, pulmonary hypertension |
| Blood grouping and crossmatch | Major surgery with expected blood loss |
| Thyroid function | Thyroid disease |
| Pregnancy test | Women of childbearing age (when applicable) |
| Sickle cell screening | At-risk populations |
7. ASA Physical Status Classification
Used to stratify anaesthetic risk:
| Class | Description | Example |
|---|---|---|
| ASA I | Normal healthy patient | Healthy adult, no comorbidities |
| ASA II | Mild systemic disease | Controlled DM, mild hypertension, obesity (BMI 30-40), active smoker |
| ASA III | Severe systemic disease | Uncontrolled DM, morbid obesity, active CHF, COPD |
| ASA IV | Severe disease - constant threat to life | Unstable angina, decompensated CHF, renal failure on dialysis |
| ASA V | Moribund, not expected to survive without surgery | Ruptured aortic aneurysm, massive trauma |
| ASA VI | Brain-dead donor for organ harvesting | - |
The letter "E" is appended for emergency procedures (e.g., ASA IIE).
8. Pre-operative Optimisation
Based on the evaluation, conditions should be optimised before elective surgery:
- Cardiovascular: continue antihypertensives; consider starting beta-blockers in high-risk patients; obtain cardiology consult for uncontrolled disease
- Pulmonary: treat active infections, bronchospasm; stop smoking ≥3 weeks before surgery (reduces bronchial hypersecretion); start physiotherapy
- Endocrine: glucose optimisation; hold oral hypoglycaemics; adjust insulin dosing; treat thyroid disease
- Haematology: correct anaemia; review anticoagulation management; plan for blood products
- Medications: continue cardiac and pulmonary medications up to the day of surgery; assess subacute bacterial endocarditis (SBE) prophylaxis need; hold oral anticoagulants per bridging protocol
- Dental: remove carious teeth ≥3 weeks before surgery (prevents postoperative lung abscess)
- Weight: encourage weight reduction in obese patients before elective surgery
9. NPO (Nil Per Os) Guidelines
Aspiration of gastric contents is a serious perioperative risk. Standard ASA fasting guidelines:
| Ingested material | Minimum fasting period |
|---|---|
| Clear liquids | 2 hours |
| Breast milk | 4 hours |
| Infant formula / non-human milk | 6 hours |
| Light meal (toast, clear liquids) | 6 hours |
| Heavy meal (fried/fatty food, meat) | 8 hours |
Patients with increased aspiration risk (GERD, obesity, gastroparesis, bowel obstruction, pregnancy) may need special precautions (rapid sequence induction, premedication with antacids/H2 blockers/prokinetics).
10. PONV Risk Assessment
The Apfel score is commonly used for adults:
| Risk factor | Points |
|---|---|
| Female gender | 1 |
| Non-smoker | 1 |
| History of PONV or motion sickness | 1 |
| Postoperative opioid use (anticipated) | 1 |
- 0 factors: ~10% PONV risk
- 1 factor: ~20%
- 2 factors: ~40%
- 3 factors: ~60%
- 4 factors: ~80%
Dual antiemetic prophylaxis is recommended with 1-2 risk factors; 3-4 agents for >2 risk factors.
11. Informed Consent for Anaesthesia
The final step includes:
- Explaining the proposed anaesthetic technique (general, regional, neuraxial, monitored care)
- Discussing risks and alternatives
- Answering patient questions
- Documenting the patient's consent
Sources:
- Barash, Cullen, and Stoelting's Clinical Anesthesia, 9e - Chapter 23: Preoperative Patient Assessment and Management
- Pye's Surgical Handicraft, 22nd Edition - Preoperative Assessment
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