• To revise the principles of transfusion, see Principles of transfusion and Consent for transfusion guidelines
• Collected from UK volunteer whole blood and/or apheresis platelet donors
• Laboratory will issue 'pooled' or 'apheresis' platelets according to product availability (or as per clinical haematology request)
• Stored in controlled temperature 20-24°C with agitation for <7 days with bacterial screening
  • no need to agitate platelets after removal from cold storage
• Contains small quantities of red cells (ABO/RhD appropriate platelets issued by laboratory)
• Pooled buffy coat platelets (4 donors in 'platelet additive solution')
  • mean volume 294 mL (150-380 mL), mean platelet yield 312 x 10⁹/unit (specification ≥240 x 10⁹/unit)
• Apheresis platelets (1 donor in 100% plasma)
  • mean volume 217 mL, mean platelet yield 280 x 10⁹/unit (specification ≥240 x 10⁹/unit)

• Thrombocytopenia (or platelet dysfunction) where significant bleeding, or risk of significant bleeding - see below
• Wherever possible, identify and treat the cause of thrombocytopenia in preference to platelet transfusion 
• Always consider alternatives/adjuncts to platelet transfusion 
• Platelet transfusion is not without risk
  
  • if in any doubt regarding the use of platelet transfusion, link with clinical haematology 

• Thrombotic thrombocytopenic purpura (TTP) unless life-threatening haemorrhage

• Apply surface pressure and correct any surgical cause of bleeding
• Review/stop anticoagulant/antiplatelet medication
• Correct cause of thrombocytopenia e.g. steroids/thrombopoietin receptor agonists (TPO agents) in ITP, avotrombopag in chronic liver disease (CLD)
• Consider tranexamic acid
• Uraemia with bleeding - dialysis, correct anaemia, consider desmopressin/DDAVP^®
• Inherited platelet function disorders - consider tranexamic acid, desmopressin/DDAVP^®
• If fibrinogen <1.5 g/L with severe bleeding, replace. See Cryoprecipitate guideline

Choose indication for possible transfusion - see WHO Bleeding Score

1. Prophylactic (WHO bleeding grade 0-1) - to prevent bleeding
2. Pre-procedure - to prevent bleeding expected to occur during surgery/invasive procedures
3. Therapeutic (WHO bleeding grade ≥2) - to treat active bleeding

Before transfusion always assess:

• Cause of thrombocytopenia (or platelet dysfunction)
• Objective measure of bleeding severity (use WHO Bleeding Score ) 
• Bleeding risk of procedure/surgery (where relevant)
• Additional risk factors for bleeding/clinical history/transfusion history 
• Alternatives/adjuncts to platelet transfusion 
• Use only one adult dose [one unit/1 adult treatment dose (ATD)] routinely for prophylactic platelet transfusions
• No clear relationship between severity of thrombocytopenia and risk of spontaneous bleeding
• Clinical factors other than platelet count are important determinants of bleeding
  
  • e.g. sepsis, antimicrobial treatment, abnormalities of haemostasis
• Certain subgroups of patients e.g. autologous stem cell transplant may not require prophylactic platelet transfusion irrespective of platelet count
• A 'risk-adapted approach' may be more prudent (i.e. individually risk assess rather than transfuse based on absolute platelet count)

Reversible bone marrow failure (BMF)

• Reversible BMF associated with treatable disease and/or chemotherapy including stem cell transplantation, where recovery is anticipated
• Transfusion threshold: platelets <10 x 10⁹/L 
• If sepsis/haemostatic abnormality, or other additional risk factor for bleeding, consider transfusion threshold 10-20 x 10⁹/L - individual review required
• Consider no routine prophylactic transfusion in autologous stem cell transplantation 

Critical illness

• Prevalence of platelet count <50 x 10⁹/L in ICU is 5-20%
• Platelet transfusion in critically ill patients is associated with increased morbidity and mortality (likely due to pro-inflammatory mechanisms) with limited evidence of benefit
• Transfusion threshold: platelets <10 x 10⁹/L (if sepsis/haemostatic abnormality, or other additional risk factor for bleeding, 10-20 x 10⁹/L) in discussion with clinical haematology 

Other situations

• Consider platelet transfusion to prevent bleeding in severe thrombocytopenia (platelet count <10 x 10⁹/L) caused by abciximab

Prophylactic transfusion NOT indicated (in absence of surgery/procedure) in:

• Chronic stable BMF e.g. myelodysplastic syndrome (MDS) if not on intensive treatment and not bleeding. 'No prophylactic platelet transfusion' strategy includes those on low dose oral chemotherapy or azacitadine 
• Abnormal platelet function - both inherited or acquired disorders e.g. uraemia
• Platelet consumption/destruction e.g. disseminated intravascular coagulation (DIC), thrombotic thrombocytopenic purpura (TTP) 
• Immune thrombocytopenia e.g. immune thrombocytopenic purpura (ITP), heparin induced thrombocytopenia (HIT), post transfusion purpura (PTP)

Before transfusion always assess:

• Cause of thrombocytopenia (or platelet dysfunction) and correct
• Objective measure of bleeding severity (use WHO Bleeding score ) 
• Bleeding risk of procedure/surgery (where relevant)
• Additional risk factors for bleeding/clinical history/transfusion history 
• Alternatives/adjuncts to platelet transfusion 

Transfusion not indicated

• Bone marrow aspirate or trephine biopsy
• Peripherally inserted central catheters (PICC) line insertion/removal
• Traction removal of tunnelled central venous catheter
• Cataract surgery

Transfusion not indicated in low risk interventional radiology (IR) procedures

• Basic venous interventions (IVC filter insertion/removal)
• Superficial interventions/biopsies (excludes liver/renal)
• GI tract stenting
• Musculoskeletal interventions
• Ultrasound guided drainages
• Catheter exchange/removal

Indications

Central venous catheter (CVC) insertion (un-tunnelled)

• Transfusion threshold: platelets ≤20 x 10⁹/L

Tunnelled CVC line insertions

• Transfusion threshold: platelets <20-50 x 10⁹/L (depending on technician, line position, clinical history - discuss with haematology) 

Moderate/high risk IR interventions e.g. arterial interventions, embolisation, dialysis access, liver/renal biopsy, tumour ablation, aortic stent grafting

• Transfusion threshold: platelets ≤50 × 10⁹/L

Lumbar puncture

• Transfusion threshold: platelets ≤40 x 10⁹/L

Percutaneous liver biopsy

• Transfusion threshold: platelets ≤50 x 10⁹/L
• Consider transjugular biopsy if platelet count is below this level

Major surgery

• Transfusion threshold: platelets ≤50 x 10⁹/L

Spinal anaesthesia

• Transfusion threshold: platelets ≤50 x 10⁹/L
• Weak recommendation, low quality of evidence 

Epidural anaesthesia, insertion and removal

• Transfusion threshold: platelets ≤80 x 10⁹/L
• Weak recommendation, low quality of evidence 

Neurosurgery/ophthalmic surgery involving posterior segment of the eye

• Transfusion threshold: platelets ≤100 x 10⁹/L

Congenital platelet function disorders e.g. Glanzmann thrombasthenia

• Discuss with clinical haematology
• Consider alternatives/adjuncts to platelet transfusion e.g. tranexamic acid, rFVIIa
• Use HLA-matched platelets, where transfusion indicated, where time allows [link with NHS blood and transplant manufacture (NHSBT)]

Acquired platelet function disorders e.g. renal failure

• In renal failure correct anaemia, uraemia and consider DDAVP^® - link with clinical haematology. Avoid platelet transfusion as infused platelets will acquire a dysfunction similar to the patients' own platelets and platelet transfusion may result in alloimmunisation

Acquired platelet function disorders e.g. antiplatelet medications

• Stop medication before surgery where clinically appropriate
• Single-agent aspirin unlikely to confer significant risk - no action required
• If high bleeding risk procedure e.g. neurosurgery, on P2Y12 antagonists e.g. clopidogrel, or glycoprotein IIa/IIIb inhibitor - discuss with clinical haematology 
• If surgical procedure is not to be performed, do not transfuse platelets 
• Consider platelet function testing - thromboelastrography (TEG) in cardiac theatres or platelet function testing [platelet function assay (PFA) in laboratory], as 20-30 % of patients are non-responders to aspirin, clopidogrel or both
  
  • when laboratory documented platelet function within normal limits, avoid platelet transfusion
  • with TEG platelet mapping, if MA result in ADP/AA channels >50 mm, patient no more at risk of bleeding than patient who is not on antiplatelet therapy, avoid transfusion 
• Consider alternatives/adjuncts to platelet transfusion 
• If transfusing platelets, assess timing of medication administration, as residual drug may inhibit transfused platelets 
  
  • ensure >2 hr elapsed post aspirin ingestion
  • ensure >12-24 hr post clopidogrel ingestion

Before transfusion always assess:

• Cause of thrombocytopenia (or platelet dysfunction) and correct
• Objective measure of bleeding severity (use WHO Bleeding score ) 
• Bleeding risk of procedure/surgery (where relevant)
• Additional risk factors for bleeding/clinical history/transfusion history 
• Alternatives/adjuncts to platelet transfusion 

Indications

Critical site bleeding e.g. CNS

• Transfusion threshold: platelets <100 x 10⁹/L

Major haemorrhage (WHO grade 3+)

• Transfusion threshold: platelets <50 x 10⁹/L
• Empirically as per major haemorrhage protocol (MHP) 

Clinically significant bleeding (WHO grade 2)

• Transfusion threshold: platelets <30 x 10⁹/L

Congenital platelet function disorders e.g. Glanzmann thrombasthenia

• Discuss with clinical haematology

Acquired platelet function disorders e.g. antiplatelet medications, renal failure

• Platelet transfusion may be inferior to standard care in patients on antiplatelet agents with spontaneous intracerebral haemorrhage
• See information in 2. Prophylactic platelet transfusions pre-procedure and discuss with clinical haematology 

• Each ATD platelets is an independent treatment decision (single unit policy)
• For prophylaxis, do not routinely transfuse more than 1 ATD (1 unit)
• Before invasive procedure or to treat bleeding, consider the size of the patient, previous increments and the target platelet count 
• Prescribe on the fluid prescription of the drug chart (or specific transfusion chart where available) 
• Assess every patient for risk of transfusion associated circulatory overload (TACO)
  
  • manage appropriately e.g. rate, diuretics, frequency of observations 

Effect of transfusion

• 1 ATD platelets typically increases platelet count by 20-40 x 10⁹/L
• Platelet increment reduces with repeated platelet transfusions
  
  • even in the absence of alloimmunisation
• Platelet increment in patients with chronic liver disease may be lower, but platelet activity is increased due to higher circulating von Willebrand factor
• In some situations, target platelet thresholds may not be achievable 
  
  • individual case review is required

• Transfuse as soon as possible after component arrives
  • use a standard blood administration set with a 170-200 micron filter
• Transfuse immediately before surgery/procedure (where relevant)
• Do not transfuse platelets through an administration set that has already been used to administer red blood cells
  • to avoid platelet clumping
• Check product for signs of deterioration/bacterial contamination before use
  • e.g. clumping/discolouration, damage to bag
  • do not transfuse, return to laboratory
• Transfusion rate must be specified on prescription (not range)
• Transfusion rate depends on clinical situation/patient history typically:
  • if low risk of TACO, 20-30 min per ATD - specify time on prescription 
  • if high risk of TACO, 30-60 min per ATD - specify time on prescription 
  • if major haemorrhage protocol (MHP) 'stat' over 5-10 min - correlate with bleeding severity 
• Any blood component connected to the patient’s IV access is regarded as ‘transfused’ for traceability purposes - even if the unit was subsequently (partially) wasted

• Assess patients clinically after each ATD for bleeding symptom severity and signs/symptoms of adverse events (see  Adverse reactions to blood transfusion guideline) and TACO
• Assess laboratory parameters after each unit
• repeat FBC@≥15mins to assess if target platelet threshold achieved