Abstract and Introduction
Platelets are critical for clot formation. A normal platelet count is 250 × 103 cells/μl of blood, and there are approximately 2 × 1012 platelets in the whole body, with two thirds in circulation and one third sequestered in the spleen. Platelets provide both primary hemostasis through the formation of a platelet plug and secondary hemostasis by providing "rafts" of negatively charged surface phospholipids on which the amplification and propagation phases of plasma coagulation occur. If lost or dysfunctional platelets need to be replaced quickly, transfusion of stored donor platelets is the only widely available therapy.
It is sometimes hard to know when to transfuse platelets. Stored platelets are a complex biologic therapy, and transfusion results depend on the donor, processing, and storage. Most perioperative practices are not supported by high-quality evidence. Traditionally, it is acceptable to perform percutaneous procedures with platelets greater than or equal to 20 × 103 cells/μl, do abdominal surgery with greater than or equal to 50 × 103 cells/μl, and do neurologic or posterior ocular surgery with greater than or equal to 100 × 103 cells/μl (Table 1). These are apparently acceptable limits-the true physiologic thresholds are probably lower-and exceptions abound. For example, research in trauma suggests that actively bleeding patients do better when platelets are administered early, even when counts are maintained above 100 × 103 cells/μl. On the other hand, patients taking antiplatelet agents who have nonsurgical intracranial hemorrhage may be harmed by platelet transfusion. Optimal platelet therapy is also hampered by a lack of tests that can stratify bleeding risk, rapidly and accurately differentiate causes of coagulopathy, or reliably guide physicians at the bedside.
This paper will discuss guidelines, physiologic evidence, and the results of randomized clinical trials as they affect perioperative platelet therapy. By "perioperative" we mean any procedure in which a patient might be under the care of an anesthesiologist. In most cases, specific, actionable evidence is missing, so it is impossible to provide a formal systematic review. All references were found by searching Medline or from the citations of references found in Medline. For the interested reader, we have provided a list of particularly influential primary clinical research (Table 2).
Anesthesiology. 2021;134(3):471-479. © 2021 American Society of Anesthesiologists | Lippincott Williams & Wilkins