What routine labs should be done on postoperative day 1 (POD1) after an elective joint replacement?

Routine Laboratory Testing on POD1 After Elective Joint Replacement

Routine laboratory testing on postoperative day 1 after elective joint replacement should include a complete blood count (CBC), comprehensive metabolic panel (CMP), and PT/INR, as these are the only labs with guideline-level support for routine POD1 monitoring. 1

Evidence-Based Laboratory Protocol

Standard POD1 Labs (Recommended)

• Complete blood count (CBC) should be obtained on the day following joint replacement surgery 1
• Comprehensive metabolic panel (CMP) should be obtained on POD1 1
• PT/INR should be obtained on POD1 1
• Hemoglobin/hematocrit may be obtained on the same day of surgery (POD0) depending on institutional protocols and clinical judgment 1

Labs NOT Routinely Indicated POD1

• ESR and CRP are NOT indicated routinely on POD1 in uncomplicated cases, as CRP remains elevated for up to 2 months after surgery under normal circumstances 1
• ESR and CRP should only be obtained when there is clinical suspicion of infection (fever, wound drainage, persistent pain, swelling) 1
• Synovial fluid analysis is NOT routinely indicated on POD1 unless acute infection is suspected based on clinical findings 1

Clinical Context and Rationale

The guideline recommendation for routine POD1 labs comes from consensus on monitoring for immediate postoperative complications rather than infection surveillance. The CBC monitors for bleeding complications (given that transfusion rates historically ranged from 37-71% in joint replacement patients) 2, while the CMP assesses electrolyte disturbances and renal function that may occur perioperatively 1.

Important Caveats

• Inflammatory markers (ESR/CRP) are expected to be elevated in the immediate postoperative period and do not return to baseline until approximately 2 months after surgery 1
• Testing ESR/CRP on POD1 provides no diagnostic value for infection detection, as they will be elevated regardless of infection status 1
• If infection is suspected clinically (fever, acute onset symptoms, wound concerns), then ESR and CRP should be obtained along with blood cultures 1

Special Populations Requiring Additional Monitoring

• Diabetic patients should monitor glucose levels particularly from POD1 to POD3 due to transient hyperglycemia risk from perioperative steroids or stress response 1
• Patients on anticoagulation may require additional coagulation monitoring beyond routine PT/INR based on their specific regimen 1

Common Pitfalls to Avoid

• Ordering inflammatory markers (ESR/CRP) routinely on POD1 wastes resources and provides no actionable information, as these will be elevated in all patients 1
• Over-transfusing based solely on hemoglobin thresholds (such as Hb <10 g/dL) without clinical indication; transfusion should be reserved for Hb <8 g/dL or strong clinical need 2
• Failing to obtain baseline labs when infection is suspected, as these values are critical for later comparison if complications develop 1, 3