What pre-operative labs are typically recommended before surgery?

Recommended Preoperative Laboratory Tests

Preoperative laboratory testing should be selective and based on specific patient risk factors and the type of surgery rather than ordered routinely for all patients, as indiscriminate testing rarely alters perioperative management and does not improve outcomes. 1

Core Principles for Preoperative Testing

• Routine preoperative testing for healthy patients undergoing low-risk procedures is not recommended
• Testing should be guided by patient-specific risk factors and surgical complexity
• Tests performed within 2 months of surgery generally do not need to be repeated 2

Recommended Testing Based on Patient Factors

Complete Blood Count (CBC)

• Indicated for patients with:
  • History of anemia or recent blood loss
  • Hematologic disorders
  • Anticipated significant blood loss during surgery
  • Cardiovascular surgery
  • Elderly patients undergoing major surgery 3
• Not recommended routinely for healthy patients 1

Electrolytes and Renal Function Tests

• Indicated for patients with:
  • Hypertension, heart failure, chronic kidney disease
  • Complicated diabetes mellitus
  • Liver disease
  • Patients taking diuretics, ACE inhibitors, ARBs, NSAIDs, or digoxin 1, 3
• Not indicated based on age alone 1

Coagulation Studies

• Indicated for patients with:
  • Known coagulation disorders
  • Liver disease
  • Patients taking anticoagulants
  • History of excessive bleeding or bruising
  • Family history of heritable coagulopathy 1, 3
• Not recommended routinely for healthy patients 1

Glucose Testing

• Random glucose testing indicated for patients at high risk of undiagnosed diabetes
• HbA1C testing for patients with known diabetes only if results would alter perioperative management 1, 3

Electrocardiogram (ECG)

• Indicated for patients with:
  • Known coronary heart disease or structural heart disease
  • Age >65 years
  • Cardiovascular risk factors (diabetes, hypertension)
  • Active cardiovascular signs or symptoms 1, 3

Chest X-ray

• Indicated for patients with:
  • New or unstable cardiopulmonary signs or symptoms
  • Risk of postoperative pulmonary complications if results would change management 3
• Not recommended routinely for healthy patients 1

COVID-19 Testing

• Recommended for all patients before non-emergent surgery
• For emergency cases, proceed with surgery while awaiting results 1, 3

Testing Recommendations by Surgical Risk

Low-Risk Surgery (e.g., cataract surgery, minor procedures)

• Healthy patients: No preoperative testing needed 1
• Patients with comorbidities: Selective testing based on specific conditions

Moderate-Risk Surgery

• Selective testing based on patient risk factors
• Consider ECG for patients >65 years or with cardiovascular risk factors 3

High-Risk Surgery (e.g., major vascular, cardiac, thoracic)

• More comprehensive testing recommended:
  • CBC, electrolytes, renal function
  • Coagulation studies if indicated
  • ECG for patients >65 years or with risk factors
  • Consider type and screen for procedures with anticipated blood loss >500ml 3

Timing of Preoperative Tests

• Laboratory tests performed within 2 months of surgery generally do not need to be repeated for healthy patients 2
• For patients with significant comorbidities, testing closer to surgery may be warranted
• COVID-19 testing should be performed within 48-72 hours before surgery 1

Common Pitfalls to Avoid

• Ordering routine "battery" tests for all surgical patients regardless of risk
• Repeating normal tests unnecessarily when previous results are recent and normal
• Failing to consider the impact of test results on perioperative management
• Delaying urgent surgery for non-essential testing 3

Special Considerations

• For patients undergoing cataract surgery, no preoperative testing is required for patients in their usual state of health 1
• For orthopedic trauma patients, pay particular attention to platelet count, coagulation studies, and bilirubin levels, as abnormalities may predict cardiac and septic complications 4

By following these evidence-based recommendations, clinicians can ensure appropriate preoperative testing that improves patient outcomes while avoiding unnecessary costs and potential harms from over-testing.