In a nutshell: Abnormal Coagulation Tests and Blood ... • Scheduled for elective hernia surgery ‘ ... Pathway. Extrinsic . Pathway. Common . Pathway. ... • As part of investigation

In a nutshell: Abnormal Coagulation Tests and Blood Transfusion

Ng Heng JooDepartment of HaematologySingapore General Hospital

The typical case

54 year old man• Scheduled for elective hernia surgery

‘…Sir, the anaesthetist has cancelled this case … his bloods are abnormal…may bleed’

How does a patient stop bleeding during surgery (haemostasis)?

1. Vascular smooth muscle contraction2. Platelet adhesion and aggregation3. The coagulation system4. The surgeon

The Haemostasis Screen

• Coagulation screen – Prothrombin time (PT)– Activated partial thromboplastin time (aPTT)

• Platelet count

The Prothrombin Time (PT)

Tissue factor

CalciumCitrate anticoagulated

plasma

Activated Partial Thromboplastin Time

Surface activating agente.g kaolin

PhospholipidCitrate anticoagulated

plasma

Factor XII

Factor VII

Factor XI

Factor IX

Factor I

Factor II

Factor V

Factor X

Factor VIII

Intrinsic Pathway

Extrinsic Pathway

Common Pathway

Prolongs PTT

Prolongs PT

Prolongs PT and PTT

PT and PTT made easy

TF

HMWK

PK

Factor XII

Factor VII

Factor XI

Factor IX

Factor I

Factor II

Factor V

Factor X

Factor VIII

Intrinsic Pathway

Extrinsic Pathway

Common Pathway

PT and PTT made easy

TF

HMWK

PK PTPTT

Possible patterns of the abnormal PT/aPTT

Prolonged PTNormal aPTT

Factor VII deficiencyor inhibitors

Normal PTProlonged aPTT

Factor VIII, IX, XI or XII deficiencyor inhibitors

Lupus anticoagulant

Prolonged PT and aPTT

Factor I, II, V or X deficiencyor inhibitors

Multiple clotting factor deficiencies

The 50:50 Mixing Study

One volume Normal Plasma

All clotting factorsat 100%

One VolumePatient’s Plasma

Worse case scenario

Clotting factor at 0%

Factor concentrations of 30% or more should give a normal PT/PTT result

Total = 50%In clotting factor deficiencies, the PT or PTT should normaliseIf PT/aPTT remains prolonged, suspect inhibitors

When is the surgeon likely to encounter an abnormal coagulation

screen?• Pre-admission or pre-operative screening

investigation• As part of investigation for intra or post-op

bleeding that is beyond expected norms

If I were a surgeon, what does an abnormal coagulation profile mean to

me….• Can I operate?• I need to operate – how can I operate?• I have operated – how will it affect my

operation?• My patient is bleeding and it is making me

look bad – do I need to and how do I correct it?

Is it really necessary to do a pre-operative coagulation screen for all

patients?

Pre-operative coagulation screening .…what you don’t know cannot hurt you!

Chee YL et al. BJH 2008

The pre-operative coagulation screen

• Indiscriminate coagulation screening prior to surgery or other invasive procedures to predict postoperative bleeding in unselected patients is not recommended. (Grade B, Level III).

• A bleeding history including detail of family history, previous excessive post-traumatic or postsurgical bleeding and use of anti-thrombotic drugs should be taken in all patients preoperatively and prior to invasive procedures. (Grade C, Level IV).

• If the bleeding history is negative, no further coagulation testing is indicated. (Grade C, Level IV).

• If the bleeding history is positive or there is a clear clinical indication (e.g. liver disease), a comprehensive assessment, guided by the clinical features is required. (Grade C, Level IV).

Chee YL et al. BJH 2008

Positive predictive value of abnormal coagulation test for post-op bleeding

Poor (inconsistent) predictive value

Chee YL et al. BJH 2008

The lowdown on PT and aPTT

• In-vitro assays – do not necessarily reflect in-vivo haemostatic response

• Best use as diagnostic tests to confirm the presence of a bleeding disorder – not as screening test to detect a bleeding disorder

• Normal range excludes 2.5% of healthy people whose results may be above normal

The PT and/or aPTT is abnormal

Can I ignore an abnormal PT/aPTT?

• No personal or family history of bleeding• Marginal prolongation of 1-2 seconds beyond

the normal range

Before I call a colleague, what I should probably find out first?

• Known congenital bleeding disorder– Haemophilia A and B– Von Willebrand

• Known acquired bleeding disorder– Acquired factor inhibitors e.g against factor 8– Drugs – e.g. anticoagulants– Liver disease– Sepsis/acute DIC

• A bleeding history

When do I need to give something before surgery?

• Most congenital factor deficiencies– Exceptions: factor XII deficiencies, mild factor VII

with known bleeding phenotype

• Severe sepsis +/- DIC

The case of the patient with liver disease

• Prolongation of PT and aPTT common in liver disease

• Isolated prolonged PT seen in early liver disease due to fall in factor VII

• PT and PTT are poor predictors of bleeding• Routine correction of coagulopathy is not

required for non-bleeding patients

The patient on anticoagulant

General principals• Wait if possible – allow anticoagulant effect to

wear off• If you cannot wait

– Warfarin: IV vitamin K AND 4 factor prothrombin complex (4F-PCC) or FFP

– Heparin/low molecular weight heparin –protamine sulphate

– Non-vitamin K oral antagonist – 4F-PCC

The patient with acquired coagulation factor inhibitors

• PLEASE…. TRY…… NOT TO OPERATE• If you do, be prepared to file for bankruptcy

for patient, doctor and hospital• Use recombinant activated factor VII or FEIBA

till such time when bleeding stops

The case of the lupus anticoagulant positive patient

• aPTT prolonged, PT normal, lupus anticoagulant demonstrated

• Patient is however prothrombotic• No correction of aPTT before surgery• Consider VTE prophylaxis after surgery

What do I give to correct coagulopathy?

• Known single factor congenital deficiency– Haemophilia A: factor VIII concentrates– Haemophilia B: factor IX concentrates– Von Willibrand disease: intermediate purity factor

VIII with high vWF– Factor VII deficiency: recombinant activated factor

VIIa– Others: fresh frozen plasma

Factor inhibitors

• Recombinant activated factor VII (Novo Seven)• FEIBA

Are there numerical guides on when I should correct an abnormal

coagulation profile before surgery?• INR >1.2 for surgery in critical areas• INR > 1.5 for major surgery in non-critical

areas• PT and aPTT > more than 1.5x the mid-point

of the normal range

If I give fresh frozen plasma, how much should be given?

• 10-20 mls per/kg• For the average size individual, at least 750

mls (approx. 3 packs)

The platelet count – what is a ‘safe” number for surgery

• 50 x 109/L for major surgery in non-critical areas

• 100 x 109/L of surgery in critical areas e.gintracranial, spinal, ocular surgery

Packed red cell transfusion

General principles• Hb >10 gm/dl – very little justification for

transfusion• Hb<7 gm/dl – beneficial especially when

symptomatic or if there is ongoing blood loss• Hb 7-10gm/dl – individualized. Assess

symptoms and signs, co-morbidities, evidence of ongoing blood loss or potential for blood loss

Singapore Med J 2011; 52(3) : 211

Thank you