What preoperative laboratory and imaging studies are recommended for an adult undergoing orthopedic surgery with regional (block) anesthesia?

Preoperative Testing for Orthopedic Surgery Under Block Anesthesia

For adults undergoing orthopedic surgery with regional (block) anesthesia, obtain complete blood count (CBC) and urea/electrolytes routinely; coagulation studies and chest X-ray only if clinically indicated; and ECG based on age and cardiovascular risk factors.

Essential Laboratory Tests

Routine Testing Required

All patients undergoing orthopedic surgery with regional anesthesia should have:

• Complete blood count (CBC) 1
• Urea and electrolytes 1

These tests are mandatory regardless of the anesthetic technique because they identify critical conditions affecting surgical outcomes and anesthetic safety.

Hemoglobin Considerations for Orthopedic Surgery

The CBC is particularly important in orthopedic procedures because:

• Pre-operative anemia occurs in approximately 40% of orthopedic trauma patients 1
• Perioperative hemoglobin can drop by approximately 2.5 g/dL 1
• Consider pre-operative transfusion if Hb < 9 g/dL, or < 10 g/dL with ischemic heart disease 1
• If Hb is 10-12 g/dL, crossmatch two units of blood 1

Platelet Count and Regional Anesthesia Safety

The platelet count from your CBC is critical for regional anesthesia safety:

• Platelet count 50-80 × 10⁹/L is a relative contraindication to neuraxial anesthesia 1
• Platelet count < 50 × 10⁹/L typically requires pre-operative platelet transfusion 1
• For patients on anticoagulants or with suspected coagulopathy, check platelets immediately before the block 2

Electrolyte Testing Rationale

Electrolyte measurement is essential for patients:

• Taking digoxin, diuretics, ACE inhibitors, or ARBs 3
• With known renal disease 3
• With cardiovascular disease undergoing intermediate or major surgery 3

Selective Testing Based on Clinical Indicators

Coagulation Studies

Order coagulation studies ONLY if: 1

• Patient is on anticoagulation therapy
• History of bleeding disorders
• Liver disease present
• Clinical suspicion of coagulopathy
• Platelet count abnormalities detected

Do not order routine coagulation studies for healthy patients undergoing regional anesthesia.

Chest Radiography

Order chest X-ray ONLY if: 1

• Active cardiopulmonary symptoms
• Known significant cardiac or respiratory disease requiring assessment
• Clinical examination reveals new findings

Routine chest X-rays are not indicated for asymptomatic patients.

Electrocardiography (ECG)

The ECG recommendations vary by guideline, but a practical approach is:

Obtain ECG for: 3

• All patients > 65 years
• Patients with diabetes, hypertension, cardiovascular disease, or inability to exercise
• Any patient with cardiovascular risk factors undergoing intermediate or high-risk surgery

ECG is NOT indicated for: 3

• Asymptomatic patients with no risk factors undergoing low-risk procedures

Monitoring Requirements During Regional Anesthesia

Once you proceed with the block, minimum monitoring includes: 4

• ECG
• Non-invasive blood pressure (NIBP)
• Pulse oximetry (SpO₂)

These monitors must:

• Begin BEFORE the regional anesthesia procedure
• Continue for at least 30 minutes after block completion 4

Common Pitfalls to Avoid

1. Do not order "routine" preoperative panels - The evidence strongly supports selective testing based on clinical indicators 5, 6, 7. Routine testing without clinical indication is costly and rarely changes management.

2. Do not skip platelet count review before neuraxial blocks - This is the single most important test for preventing catastrophic vertebral canal hematoma 1, 2.

3. Do not assume normal recent labs are sufficient - In patients with pre-eclampsia, rapidly evolving coagulopathy, or acute illness, check labs immediately before the procedure 2.

4. Do not forget glucose monitoring for diabetics - Blood glucose should be measured at least hourly in patients with treated diabetes during anesthesia 4.

Special Populations

High-Risk Patients Requiring Additional Assessment

For patients with severe systemic disease (ASA 3-4), which represents approximately 70% of orthopedic trauma patients 1:

• Review all medications carefully for drug interactions
• Assess cardiovascular disease (present in 35%), respiratory disease (14%), and diabetes (9%) 1
• Consider consultation with an anesthesiologist experienced in regional techniques 8

Anticoagulated Patients

If the patient is on anticoagulation:

• Verify appropriate timing of last dose relative to planned block
• Obtain coagulation studies (PT/INR, aPTT as appropriate)
• Check platelet count
• Follow specific guidelines for neuraxial anesthesia in anticoagulated patients 2

Evidence Quality Note

The recommendations for routine CBC and electrolytes in orthopedic surgery come from established guidelines 1, though the evidence level is rated as C (expert consensus). However, the strong consensus across multiple guidelines and the clear clinical rationale—particularly regarding anemia management and platelet counts for regional anesthesia safety—support these recommendations firmly. The more recent ESAIC guidelines 5 emphasize tailored assessment but reinforce that testing should be guided by patient comorbidities and surgical risk, not performed routinely without indication.