Postoperative thrombocytopenia

Prevalence

  • Thrombocytopenia (defined as a platelet count of <150 × 109/L) occurs after major surgery in 30% to 60% of patients:
    • 56% of cardiac surgery patients
    • 28% of hip surgery patients
  • Almost all patients undergoing major surgery have a significant decline in platelet count (e.g., 20% or 30%) compared with their preoperative baseline platelet count.

Timing

  • A platelet count decrease is normal and expected within 4 days of surgery – the majority of cardiac surgery patients have a nadir platelet count on postoperative days 2 to 3, with the platelet count returning to baseline by day 5.
  • Later onset thrombocytopenia (after 4 days of surgery) raises concerns for other causes such as:
    • Drugs:
      • Heparin-induced thrombocytopenia (HIT)
      • Drug induced immune thrombocytopenia (DITP) from perioperative medication, such as:
        • Vancomycin
        • Cephalosporins
        • Glycoprotein IIb/IIIa inhibitors
    • Post-transfusion purpura (PTP)
    • Disseminated intravascular coagulation
    • Artificial surface exposure:
      • Ventricular assist devices
      • Intra-aortic balloon pumps
      • Indwelling catheters (e.g., extracorporeal membrane oxygenation)

Pathophysiology

  • Causes:
    • Pseudothrombocytopenia – EDTA-related platelet clumping
    • Hemodilution:
      • Proportional to the amount of crystalloid, colloid, and non–platelet-containing blood products administered.
      • Dilutional thrombocytopenia manifests within minutes to a few hours following surgery.
      • Proportional reductions in hemoglobin, hematocrit, and the white blood cell count are typically seen along with the platelet decrease.
    • Accelerated platelet consumption related to surgical hemostasis.
    • Immune mediated:
      • New antibody production usually take at least 5 days to manifest.
      • Therefore DITP, HIT, or PTP usually become manifest during the second postoperative week.
  • Thrombopoietin response:
    • Takes 3 to 4 days to increase platelet production by the bone marrow megakaryocytes.
    • Results in a physiological “overshoot” in the platelet count. Postoperative platelet counts peak at two- to threefold the patient’s preoperative platelet count at approximately postoperative day 14.

Reference