What is the recommended workup for high altitude (HA) work?

Recommended Workup for High Altitude Work

The recommended workup for individuals planning to work at high altitude should include cardiovascular assessment, pulmonary evaluation, and risk stratification based on pre-existing conditions to minimize morbidity and mortality risks. 1, 2

Cardiovascular Assessment

• Comprehensive cardiovascular evaluation to identify pre-existing conditions that may worsen at altitude, including hypertension, coronary artery disease, and arrhythmias 1
• Blood pressure measurement and monitoring, as high altitude exposure is associated with increased blood pressure, especially at night 1
• ECG to detect pre-existing arrhythmias (prevalence of 0.33% in pre-altitude screening) 3
• For patients with history of coronary artery disease:
  • Risk stratification using Canadian Cardiovascular Society (CCS) classification 1
  • Stress testing for medium-risk patients to assess coronary blood flow adaptation to altitude-like conditions 1
  • Evaluation of time since any previous cardiac events (minimum 6 months after uncomplicated acute coronary syndrome or revascularization) 1

Pulmonary Evaluation

• Baseline pulmonary function tests to identify individuals at risk for high-altitude pulmonary edema (HAPE) 4, 5
• Assessment for pre-existing pulmonary hypertension, which may worsen significantly at altitude 1
• Evaluation for sleep-disordered breathing, which can worsen at altitude 1

Risk Stratification Based on Pre-existing Conditions

Cardiovascular Conditions

• Hypertension: Patients with blood pressure ≥160/95 mmHg should be excluded from high altitude work 3
• Coronary artery disease:
  • Low risk (CCS 0-I): May safely work up to 4200m with light-to-moderate physical exertion 1
  • Moderate risk (CCS II-III): May work up to 2500m but should avoid physical exertion beyond light activity 1
  • High risk (CCS IV): Should not work at high altitude 1
• Post-revascularization: Wait at least 6-12 months after coronary stenting before high altitude exposure 1

Cerebrovascular Conditions

• History of ischemic stroke: Carotid ultrasound imaging to check for complicated plaques or severe carotid stenosis 1
• History of hemorrhagic stroke or cerebral aneurysms: Increased risk due to altitude-induced blood pressure elevation 1

Other Conditions

• Obesity: Identified as a risk factor for acute mountain sickness and reduced work performance at altitude 3
• Diabetes: Consider excluding from altitude employment 3
• Asthma: Generally improves at altitude but requires monitoring for specific triggers 3

Laboratory and Additional Testing

• Complete blood count to establish baseline hemoglobin and hematocrit levels 4
• Basic metabolic panel to assess kidney function, especially if acetazolamide prophylaxis is being considered 2
• Oxygen saturation measurement at rest and with exercise 5

Prophylaxis Recommendations

• Acetazolamide (250mg twice daily or 500mg once daily) as first-line prophylactic medication for altitude sickness prevention 2, 4
• Nifedipine for individuals at high risk for HAPE 2
• Dexamethasone as an alternative when acetazolamide is contraindicated 2

Common Pitfalls to Avoid

• Underestimating the importance of gradual ascent and proper acclimatization (recommended rate: 300-600m/day above 2500m) 2, 5
• Failure to recognize that hypertensive patients may be more susceptible to high altitude effects due to elevated hypoxic peripheral and central chemoreflex sensitivity 1
• Overlooking the need for medication adjustments at altitude, particularly diuretics which may increase risk of dehydration 1, 2
• Inadequate hydration, which can worsen altitude sickness symptoms 2
• Allowing individuals with coronary heart disease or uncontrolled hypertension to work at high altitude without proper risk stratification 3