Should a complete blood count (CBC) and prothrombin time/partial thromboplastin time (PT/PTT) be performed before vitrectomy surgery?

Preoperative CBC and PT/PTT Testing Before Vitrectomy Surgery

Routine preoperative CBC and PT/PTT testing is not recommended before vitrectomy surgery unless specific risk factors for bleeding are present. 1, 2

Decision Algorithm for Preoperative Testing

CBC Testing Indications:

• Recommended for patients with:
  • History of anemia or recent blood loss 1
  • Hematologic disorders 1
  • Liver disease 1
  • Patients at extremes of age 1
  • Cardiovascular disease undergoing major surgery 1

PT/PTT Testing Indications:

• Recommended for patients with:
  • Medical conditions associated with impaired hemostasis (liver disease, hematopoietic disorders) 1, 2
  • Current anticoagulant therapy 1, 2
  • History suggesting coagulation disorder (spontaneous bruising, excessive bleeding with prior surgeries) 1
  • Family history of coagulopathy 1, 2

Evidence Analysis

Guidelines from the American Family Physician clearly state that indiscriminate preoperative coagulation testing is not warranted 1. This is supported by the American Gastroenterological Association, which suggests against extensive preprocedural testing, including repeated measurements of PT/INR or platelet count, even in patients with known baseline abnormal coagulation parameters 1.

The yield of PT/PTT testing in detecting unsuspected bleeding disorders is extremely low (0.2%) in patients without clinical indications of bleeding disorders 3. This suggests that routine testing provides minimal clinical benefit while potentially leading to false positives and unnecessary interventions.

Special Considerations for Vitrectomy

Vitreoretinal surgery has some unique considerations:

• Studies have shown that patients undergoing diabetic vitrectomy who remained on anticoagulation did not exhibit higher risk of intraoperative or postoperative vitreous hemorrhage 4.
• Maintenance of antiplatelet and anticoagulant therapy during vitreoretinal surgery has been shown to be safe in most patients 5.
• The Early Treatment Diabetic Retinopathy Study found that aspirin use did not influence rates of vitreous hemorrhage or need for vitrectomy 6.

Risk Factors Requiring Testing Before Vitrectomy

• High-risk patients who should receive testing:
  • Patients with known coagulopathies
  • Patients on anticoagulation therapy (particularly if INR >1.4) 1
  • Patients with thrombocytopenia (platelet count <100,000/ml) 1
  • Patients with liver disease or renal disease 1
  • Patients with history of bleeding complications during previous surgeries 2

Common Pitfalls to Avoid

1. Overreliance on testing: Routine testing in low-risk patients leads to unnecessary delays, costs, and potential false positives 1, 3.

2. Ignoring clinical history: A thorough bleeding history is more valuable than routine laboratory tests for predicting surgical bleeding risk 2.

3. Misinterpreting results: Mild abnormalities in coagulation tests may not correlate with clinical bleeding risk, particularly in patients without symptoms 1.

4. Discontinuing necessary anticoagulation: Stopping anticoagulation for vitrectomy may pose greater risks than continuing it in patients with high thrombotic risk 4, 5.

In conclusion, while preoperative CBC and PT/PTT testing has traditionally been part of surgical preparation, evidence suggests a targeted approach based on specific risk factors is more appropriate than universal testing before vitrectomy surgery.