PLATELETS AS A BLOOD PRODUCT 

1. INTRODUCTION

Platelets are anucleate cytoplasmic fragments derived from megakaryocytes in bone marrow and play a central role in primary hemostasis, clot stabilization, inflammation, and immunity.

Platelet transfusion is indicated to:

  • Prevent bleeding (prophylactic)
  • Treat active bleeding (therapeutic)
  • Support invasive procedures and surgeries

📌 Platelet transfusion is qualitatively different from PRBC or plasma transfusion because:

  • Platelets are metabolically active
  • Short shelf life
  • High risk of bacterial contamination
  • Immune-mediated complications are common


2. TYPES OF PLATELET PRODUCTS

A. Random Donor Platelets (RDP)

(also called Whole Blood–Derived Platelets)

Feature

Description

Source

Single unit of whole blood

Volume

~50–70 mL

Platelet content

≥ 5.5 × 10⁹ per unit

Storage

20–24°C with continuous agitation

Shelf life

5 days (7 days with bacterial testing)

ABO compatibility

Preferred but not mandatory

🔹 Dose:

  • Adult therapeutic dose = 4–6 RDP units (pooled)


B. Single Donor Platelets (SDP / Apheresis Platelets)

Feature

Description

Source

Plateletpheresis

Volume

~200–300 mL

Platelet content

≥ 3 × 10¹¹

Equivalent to

4–6 RDP units

Leukoreduction

Usually prestorage

Alloimmunization

Lower risk

🔹 Preferred in:

  • Oncology patients
  • Stem cell transplant
  • Refractory thrombocytopenia
  • HLA-matched transfusion


C. Modified Platelet Products

Type

Indication

Leukoreduced

Prevent FNHTR, CMV transmission, alloimmunization

Irradiated

Prevent TA-GVHD

HLA-matched

Platelet refractoriness

Cross-matched

Immune refractoriness

Pathogen-reduced

Reduce bacterial/viral transmission


3. STORAGE AND HANDLING

Parameter

Value

Temperature

20–24°C

Agitation

Continuous

Shelf life

5 days

pH at expiry

≥ 6.2

Storage solution

Plasma or PAS

📌 Why not refrigerated?
→ Cold storage causes rapid clearance and platelet activation.

📌 Highest bacterial contamination risk among all blood products


4. ABO AND Rh COMPATIBILITY

ABO

  • ABO-identical preferred
  • ABO-incompatible acceptable if unavoidable
  • Minor incompatibility → hemolysis risk due to donor plasma antibodies

Rh

  • Platelets lack Rh antigen
  • Residual RBCs may sensitize
  • Rh-negative females of childbearing age:
    • Give Rh-negative platelets
    • If Rh-positive platelets → give Anti-D (50 µg)


5. DOSE AND EXPECTED RESPONSE

Expected Platelet Increment

Parameter

Value

Increment per adult dose

30,000–60,000/µL

Time to check count

10–60 minutes post transfusion

Platelet lifespan

7–10 days


Corrected Count Increment (CCI)

CCI=Platelets transfused(Post−Pre)×BSA

Interpretation

CCI

Adequate response

> 7,500

Refractoriness

< 5,000


6. INDICATIONS FOR PLATELET TRANSFUSION

A. Prophylactic Transfusion (Non-bleeding)

Platelet Count

Indication

<10,000/µL

Stable patient

<20,000/µL

Fever, sepsis

<30,000/µL

Acute leukemia, APL

<50,000/µL

Invasive procedures

<100,000/µL

Neurosurgery, eye surgery

📌 Do NOT transfuse solely based on number without context


B. Therapeutic Transfusion (Bleeding)

Scenario

Threshold

Active bleeding

<50,000

Massive hemorrhage

<100,000

DIC with bleeding

<50,000

Trauma / TBI

<100,000


C. Peri-Procedural Thresholds

Procedure

Platelet Target

Central line

≥20,000

Lumbar puncture

≥50,000

Major surgery

≥50,000

Neuro / ophthalmic

≥100,000

Neuraxial anesthesia

≥80,000 (institution-dependent)


7. PLATELET TRANSFUSION IN SPECIAL CONDITIONS

A. Massive Transfusion Protocol (MTP)

  • PRBC : Plasma : Platelets = 1 : 1 : 1
  • Maintain platelets >50,000 (≥100,000 in TBI)


B. DIC

Type

Platelets

Bleeding DIC

YES

Non-bleeding

NO


C. TTP / HUS

 ABSOLUTE CONTRAINDICATION
→ May worsen thrombosis


D. ITP

Situation

Platelets

Life-threatening bleed

YES + steroids/IVIG

Routine

NO


E. Liver Disease

  • Transfuse only if:
    • Active bleeding
    • Before high-risk procedures
  • Target usually >50,000


8. CONTRAINDICATIONS

Condition

Reason

TTP / HUS

Microvascular thrombosis

HIT (unless bleeding)

Thrombotic risk

ITP (routine)

Rapid destruction

Hypersplenism (routine)

Ineffective


9. ADVERSE REACTIONS

A. Acute Reactions

Reaction

Feature

FNHTR

Fever, chills

Allergic

Urticaria

Anaphylaxis

IgA deficiency

Bacterial sepsis

Fever, shock

TRALI

Non-cardiogenic pulmonary edema

TACO

Volume overload


B. Delayed Complications

Complication

Mechanism

Alloimmunization

Anti-HLA antibodies

Platelet refractoriness

Immune/non-immune

TA-GVHD

Viable donor lymphocytes

Iron overload

Rare


10. PLATELET REFRACTORINESS

Definition

  • Failure to achieve adequate platelet increment after ≥2 transfusions

Causes

Non-immune (80%)

  • Sepsis
  • DIC
  • Splenomegaly
  • Fever
  • Bleeding

Immune

  • Anti-HLA antibodies
  • Anti-HPA antibodies

Management

  • HLA-matched platelets
  • Cross-matched platelets
  • Treat underlying cause


11. SPECIAL MODIFICATIONS

Leukoreduced Platelets

  • ↓ FNHTR
  • ↓ CMV
  • ↓ Alloimmunization

Irradiated Platelets

  • Indicated in:
    • Stem cell transplant
    • Hodgkin lymphoma
    • Congenital immunodeficiency
    • Intrauterine transfusion


12. KEY EXAM PEARLS 

🔹 Platelets stored at room temperature, not refrigerated
🔹 Highest bacterial contamination risk among blood products
🔹 1 SDP ≈ 4–6 RDP
🔹 TTP is absolute contraindication
🔹 Platelet refractoriness → think HLA antibodies
🔹 Massive transfusion → 1:1:1 strategy