Page 2223 - Hematology_ Basic Principles and Practice ( PDFDrive )

1970 Part XII Hemostasis and Thrombosis

60 54.9
After cardiac surgery
50
After orthopedic surgery
38.4
40
Patients (%) 30 25.5 26.7 Potentially abnormal
31.6
20
13.0 on or after day 5
10 4.3 3.8
0.4 1.4
0
1 2 3 4 5 >6
A Days of postoperative nadir

300 300
Platelet count (× 10 9 /L) 200 Day 2 nadir 200 Hemodilution Day 3 nadir

100
100
0 Hemodilution 0
0 1 2 3 4 5 0 1 2 3 4 5
B Days after cardiac surgery C Days after cardiac surgery
Fig. 132.7 EARLY POSTOPERATIVE PLATELET COUNT DECLINES. (A) Distribution of early post-
operative count nadirs. For both orthopedic and cardiac surgery patients, day 2 represents the most common
day for the postoperative platelet count nadir to occur (data exclude day 0); beyond postoperative day 4, it is
likely that a superimposed thrombocytopenic disorder is occurring. (B and C) Representative postcardiac
surgery platelet count declines. Both patients illustrate early hemodilution effects (day 0) and subsequent
additional early platelet count declines with nadirs of day 2 (B) and day 3 (C). Neither patient received platelet
transfusions. (From Greinacher A, Warkentin TE: Acquired non-immune thrombocytopenia. In: Marder VJ, Aird WC,
Bennett JS, et al, editors: Hemostasis and thrombosis: Basic principles and clinical practice, ed 6. Philadelphia, 2013,
Lippincott Williams & Wilkins, p 796.)

Solid Organ and Bone Marrow Transplantation obscure; reduced ADAMTS13 (a disintegrin and metalloproteinase
with thrombospondin 13) levels have not been implicated. The
Thrombocytopenia commonly occurs during episodes of solid organ hematologic abnormalities can be mild and remit spontaneously,
allograft rejection. It is possible that platelet activation and deposition although patients often have residual azotemia and hypertension.
in the transplanted organ vasculature contribute to the rejection More severely affected patients do not usually benefit from plasma-
process. Antirejection therapies can also cause thrombocytopenia pheresis. The syndrome has a poor overall prognosis, and many
through increased platelet destruction (antilymphocyte globulin) or patients die irrespective of any intervention.
BM suppression (azathioprine). Posttransplantation HUS develops in
approximately 5% of renal transplant recipients and in even fewer
recipients of liver or heart transplants. Although cyclosporine is Cardiopulmonary Bypass Surgery
sometimes implicated in HUS, it can usually be safely resumed after
recovery. Excess bleeding is a common problem in patients who undergo heart
Early, severe thrombocytopenia caused by BM-ablative therapy surgery using cardiopulmonary bypass. Many of these patients receive
invariably accompanies BM transplantation (BMT). Platelet count blood transfusions, and approximately 5% require reoperation for
9
recovery to greater than 50 × 10 /L is more rapid (16 vs. 35 postoperative bleeding.
days) in patients receiving autologous mobilized peripheral blood Thrombocytopenia and transient platelet dysfunction (see Chapter
progenitor cells than in those undergoing autologous BMT. Severe 159) are observed in virtually every patient. Typically, the platelet
persistent thrombocytopenia despite recovery of RBCs and WBCs count falls by 30% to 70%, primarily as a result of hemodilution but
is relatively common after BMT or peripheral blood transplanta- also because of bleeding and losses within the extracorporeal perfu-
tion; autoimmune thrombocytopenia has been implicated in some sion device. Because patients invariably receive heparin during cardiac
patients. Late-onset thrombocytopenia after BMT that responds to surgery and have often received heparin in the remote or recent past,
corticosteroids, IVIg, and splenectomy also has been attributed to immune HIT is frequently considered in the differential diagnosis
autoimmune thrombocytopenia. Rarely, transplantation-associated of early-onset and persisting postcardiac surgery thrombocytopenia;
alloimmune thrombocytopenia can be caused by donor–recipient however, HIT is an unlikely explanation for thrombocytopenia even
A1
incompatibility involving platelet-specific alloantigens such as Pl when anti-PF4/heparin antibodies are positive. 29
a
(HPA-1a) or Br (HPA-5b). The bleeding time increases markedly during heart surgery (to
A syndrome of thrombocytopenia, RBC fragmentation, and renal greater than 30 minutes) but usually improves to less than 15 minutes
impairment can occur in as many as 10% of patients undergoing shortly after surgery and to normal several hours later. By contrast,
BMT, usually beginning 3–12 months after transplantation (BMT- the thrombocytopenia persists for 3–4 days followed by recovery of
associated thrombotic microangiopathy). The pathogenesis remains the platelet count to values exceeding the preoperative baseline.