Page 1936 - Hematology_ Basic Principles and Practice ( PDFDrive )

1716 Part XI Transfusion Medicine

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Days with Bleeding of Grade 2 or Higher % 30
35

25
20
15
10

0 5
1−5 6−10 11−15 16−20 21−25 26−30 31−35 36−40 41−45 46−50 51−55 56−60 61−65 66−70 71−75 76−80 81−85 86−90 91−95 96−100 >100

Morning Platelet-Count Category (x10 -3 /mm 3 )
No.of 652 3240 3843 3194 2449 1976 1501 1182 1009 774 677 513 409 358 298 232 192 162 140 139 1369
Days
Fig. 112.1 RELATIONSHIP BETWEEN PLATELET COUNT AND SPONTANEOUS BLEEDING
AMONG PATIENTS WITH THERAPY-INDUCED HYPOPROLIFERATIVE THROMBOCYTOPE-
NIA. The percentage of days that adult or pediatric patients with hematologic malignancy enrolled in the
PLADO trial had grade 2 or higher bleeding is shown as a function of morning platelet count. The 95%
confidence intervals are shown as dashed lines. The bleeding risk was equivalent for platelet counts between
6000 and 80,000/µL.
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was randomized to no prophylactic platelet transfusions or routine lymphoblastic leukemia who underwent lumbar puncture. No serious
prophylaxis. Grade 2 or higher bleeding occurred in 50% of patients hemorrhagic complications were observed after 5223 lumbar punc-
in the no-prophylaxis group versus 43% in the prophylaxis group (p tures, including 170 procedures that were done when the platelet
= .06 for noninferiority.) There were no deaths due to bleeding in count was 11,000 to 20,000/µL. The authors concluded that pro-
this study. In both trials, bleeding occurred more frequently among phylactic platelet transfusion was unnecessary in patients with platelet
patients being treated for acute leukemia versus autologous stem counts above 10,000/µL. Lumbar punctures were performed in only
cell transplant recipients. Overall, the results of these trials support 29 patients with platelet counts of 10,000/µL or less, making it
the continued use of prophylactic platelet transfusions for patients difficult to assess the risk of bleeding in patients with very low platelet
with hematologic malignancy and therapy-induced hypoproliferative counts. A similar, albeit much smaller, retrospective study examined
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thrombocytopenia. 15 the same issue in adult patients with acute leukemia. No hemor-
rhagic complications were observed after 195 lumbar punctures,
including 35 that were done with platelet counts of 20,000 to
Prophylactic Platelet Dosing 30,000/µL. With very limited data published data available on
severely thrombocytopenic adults, AABB has suggested 50,000/µL as
There are currently thought to be two distinct clearance mechanisms a minimum safe platelet count for lumbar puncture in adult patients.
for platelets. Most platelets undergo senescence after circulating in For central venous catheter placements, AABB has suggested
the peripheral blood for 8 to 10 days. But there is also evidence for 20,000/µL as a minimum safe platelet count, based on multiple
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a second clearance route in which there is a fixed daily loss of platelets observational studies. Relatively few studies have been published to
that occurs independent of platelet age. Platelets exiting the circula- date addressing the question of a safety minimum platelet count for
tion via this second route are postulated to function in maintaining other types of bedside procedures (thoracentesis, paracentesis, etc.)
vascular integrity. In principle, a low dose of platelets could be used
to meet this daily requirement. This hypothesis was tested directly by
the 2010 PLADO trial. A total of 1272 patients undergoing HSCor Prophylactic Platelets for Major Surgical Procedures
chemotherapy were randomly assigned to receive low-, medium-, or
high-dose platelets for a morning count of 10,000/µL or lower. The There are currently no data from randomized trials addressing the
risk of spontaneous bleeding was not increased until patient platelet question of what constitutes an adequate platelet count before surgery.
counts fell to 5000/µL or lower. No differences were observed in Retrospective studies, though, suggest that patients with platelet
bleeding rates among the three treatment groups, supporting the counts of 50,000/µL or higher are not at excess bleeding risk during
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concept that few platelets are required to maintain hemostasis. surgery. Bishop and colleagues reported a series of 95 patients with
Although significantly fewer total platelets were transfused to patients acute leukemia who underwent 130 surgical procedures with platelet
in the low-dose group, platelet transfusions were required more counts of less than 50,000/µL. Intraoperative blood loss exceeded
frequently. 12 500 mL in only 7% of cases. No relationship was seen between the
preoperative platelet count and surgical blood loss. These data suggest
that prophylactic platelet transfusions need not be administered
Prophylactic Platelets for Invasive Bedside Procedures before surgery when the preoperative platelet count is at least
50,000/µL. This rule of thumb is thought to apply to most types of
To date, there have been no large randomized trials evaluating the surgery (cardiac, orthopedic, and so on). For a few types of surgeries,
need for platelet prophylaxis before invasive bedside procedures such however, requiring a higher platelet count (70,000–100,000/µL) is
as lumbar puncture. However, retrospective data provide reassurance traditional, although no published data currently exist either to
that moderate thrombocytopenia does not pose a serious risk for support or refute this approach. These settings include neurosurgery,
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performing such procedures. Howard et al reviewed the records of retinal surgeries, and other procedures in which the risk is not that
956 consecutive pediatric patients with newly diagnosed acute the patient may exsanguinate but rather that even a minor bleed