What tests are required for surgical clearance in a morbidly obese patient who uses electronic cigarettes (e-cigarettes)?

Pre-Surgical Clearance Tests for Morbidly Obese Patients Who Vape

For morbidly obese patients who vape, pre-surgical clearance should include comprehensive respiratory, cardiovascular, and airway assessments, with particular attention to arterial blood gas analysis, spirometry, ECG, and screening for obstructive sleep apnea. 1, 2

Respiratory Assessment

• Baseline oxygen saturation measurement - Arterial saturation <95% on air indicates potential respiratory compromise 1
• Spirometry to evaluate pulmonary function, particularly if:
  • Limited exercise tolerance
  • History of respiratory symptoms
  • Forced vital capacity <3L or FEV1 <1.5L indicates significant respiratory disease 1
• Arterial blood gas analysis if any of these warning signs are present:
  • Respiratory wheeze at rest
  • Serum bicarbonate >27 mmol/L (suggests chronic CO2 retention)
  • Oxygen saturation <95% on air 1, 2
• Polysomnography (sleep study) if symptoms of obstructive sleep apnea are present, as vaping may exacerbate underlying sleep-disordered breathing 1

Cardiovascular Assessment

• 12-lead ECG for all morbidly obese patients who vape (mandatory due to combined risk factors) 1, 2
• Assessment of exercise tolerance - A key predictor of perioperative risk 1
• Cardiopulmonary exercise testing (CPET) if:
  • Poor exercise tolerance reported
  • Multiple cardiovascular risk factors present
  • Complex or high-risk surgery planned 1, 2
• Stress testing (preferably functional exercise testing) if:
  • Unable to achieve 4 METs of activity
  • Multiple cardiac risk factors present
  • Consider pharmacological stress testing if patient cannot exercise 1

Airway Assessment

• Neck circumference measurement - >60 cm associated with 35% probability of difficult laryngoscopy 1
• Mallampati score and other standard airway assessments
• Documentation of facial hair that may interfere with bag-mask ventilation 1

Laboratory Tests

• Complete blood count - Elevated WBC may indicate chronic inflammation associated with obesity 3
• Comprehensive metabolic panel including:
  • Liver function tests (AST, ALT, bilirubin) - Especially important as obesity increases risk of NAFLD 4
  • Fasting glucose and HbA1c - To screen for diabetes
  • Lipid profile - To assess cardiovascular risk
  • Renal function tests (BUN, creatinine) 1
• Coagulation studies (PT, PTT, INR) - Especially if anticoagulation will be needed 1
• C-reactive protein - Consider as an inflammatory marker, as elevated CRP is common in morbidly obese patients and associated with increased cardiovascular risk 3

Imaging Studies

• Chest X-ray (posteroanterior and lateral views) - To evaluate cardiac size, pulmonary vascularity, and detect undiagnosed heart failure or pulmonary hypertension 1
• Consider echocardiography if:
  • History of cardiac disease
  • Poor exercise tolerance
  • Multiple cardiovascular risk factors
  • Signs of pulmonary hypertension on ECG (right axis deviation, right bundle branch block) 1

Risk Stratification

• Calculate Obesity Surgery Mortality Risk Score (OS-MRS) - Even for non-bariatric surgery, this can help stratify risk:
  • BMI ≥50 kg/m²
  • Male gender
  • Hypertension
  • Known risk factors for pulmonary embolism
  • Age ≥45 years
  • Scores of 4-5 indicate highest risk (Class C: 2.4-3.0% mortality) 1

Special Considerations for Vapers

• Document duration and frequency of vaping - Current vaping increases perioperative pulmonary complications
• Recommend cessation of vaping at least 4 weeks before surgery if possible 2
• Assess for symptoms of e-cigarette or vaping product use-associated lung injury (EVALI) - Including cough, shortness of breath, chest pain

Common Pitfalls to Avoid

1. Underestimating airway difficulties - Obesity alone increases risk of difficult intubation by 30%; vaping may further compromise respiratory function 1

2. Relying solely on BMI - While BMI is useful for screening, additional anthropometric measurements (waist circumference, neck circumference) provide more comprehensive assessment of risk 5

3. Inadequate planning for postoperative care - Consider level 2 or 3 care if:

   • OS-MRS score 4-5
   • Limited functional capacity
   • Untreated OSA with need for postoperative opioids 1

4. Overlooking depth of anesthesia monitoring - For patients >140-150 kg, standard target-controlled infusion formulas become unreliable 1

5. Failing to optimize modifiable risk factors - Consider a 2-6 week pre-operative "liver shrinking" diet to improve respiratory function and facilitate surgery 1, 2

By following this comprehensive pre-surgical clearance protocol for morbidly obese patients who vape, you can significantly reduce perioperative morbidity and mortality while improving surgical outcomes.