Transcript Plateletworks 2007 Slide Series

Hemostasis
Homeostasis
What are Platelets?
Disk-shaped
cell fragments
produced in the
megakaryocytes
Mature
Platelet
Megakaryocyte
Bone
Marrow
Storage and Circulation
Quantity - 200,000 - 400,000/mm3
Life Span - 10 days
33%
pooling
67%
in the
circulation
Spleen
Megakaryocyte
Types of Thrombi
Type
Components
Seen In
Treatment
Red
RBC, Fibrinogen,
WBC, Platelets
AMI
Thrombolytic
Therapy
White
Platelets Only
Unstable Angina
Hyperaggregable
HIT or HITT
Nitroglycerine
Yellow
Lipid Build Up
Unstable Angina
AMI
Laser Therapy
Angioplasty
Dynamics of Hemostasis
®
Platelets



Anucleate, multifunctional blood cells
First line of defense against injury to blood vessels
Adhere
Activate
Aggregate
Vascular
System
Vascular Responses
Arachidonic Acid Metabolism
Platelet Function Defects
Adhesion
Shape Change Release
Aggregation
Coagulation
Delayed Fibrin Formation
1. Failure of platelets to adhere
2. Failure to release ADP
3. Failure to release TxA2
4. Failure to aggregate
5. Failure of surface binding of coagulation factors
Electron Micrograph
of the Cellular Components of Blood
Red Blood Cell
Activated Platelet
White Blood Cell
EM Platelet Structure
Activated Platelets
Anatomy of a Platelet
Delta Granules
ADP
Serotonin
ATP
Calcium
Dense Tubular
System
Microtubular
System
Plasma Membrane
PF3
Alpha Granules
PF4
Factor V
Factor VIII R:ag
(vWF:ag)
Glycogen
Fibrinogen
Fibronectin
b Thromboglobulin
Cytosol
Factor XIII
Exterior Coat
(Glycocalyx)
Mitochondria
Surface
Connecting System
Adhesion Surface Activated Platelet
Collagen
GPIa
GPIX
Arachidonic Acid
Ca+
Serotonin
CycloOxygenase
Endoperoxides
Thromboxane
Synthetase
Ristocetin
ADP
Receptor
ADP
Dense
Body
TxA2
GPIIIa
TxA2
GPIb
Released
vWF
GPIIb
Adhesion

Plaque rupture or
vascular damage
exposes
subendothelial
proteins to which
platelet receptors
bind, resulting in
platelet adhesion
Aggregation: Activated Platelet
in Final Stage for Binding to Fibrinogen
Collagen
GPIa
GPIX
Arachidonic Acid
Ca+
Serotonin
CycloOxygenase
Endoperoxides
Thromboxane
Synthetase
ADP
Receptor
ADP
Dense
Body
Ristocetin
TxA2
GPIb
vWF
TxA2
GPIIb
GPIIIa
Released
GP IIb/IIIa Receptors:
The Final Common Pathway



Most numerous receptor on
platelet membrane surface
(40,000 to 80,000 per platelet)
Becomes receptive to
fibrinogen binding upon
platelet activation
Represents the final common
pathway for platelet
aggregation
Adapted from Charo et al. In: Colman RW et al, eds. Hemostasis and Thrombosis: Basic Principles
and Clinical Practice. 3rd ed. Philadelphia, Pa: JB Lippincott; 1994:495
Mechanism of Action:
GP IIb/IIIa Inhibitors
Pharmacologic Intervention
in Platelet Function
Platelet Inhibition Mechanisms
GPIIb
GPIIIa
IIb/IIIa
Inhibitors
Arachidonic Acid
Aspirin
CycloOxygenase
Endoperoxides
Plasmin
Dense
Body
Thromboxane
Synthetase
GPIa
GPIb
ADP Inhibitors
ADP
Receptor
Acquired Functional Disorders







Drugs
Uremia
Cirrhosis / Chronic Hepatitis
Leukemia & Myelodysplastic Syndrome
Plasma Protein Abnormalities
Myeloproliferative Disorders
Cardiopulmonary Bypass
Effect of Cardiopulmonary Bypass
on Hemostasis
Hemodilution
Platelets
Coagulation Proteins
Activation
Platelets
Fibrinolysis
Coagulation
Drugs That Affect Platelets

Analgesics (aspirin, NSAIDs) affecting prostanoid synthesis
or action

Caffeine, theophylline, dipyridamole, and drugs which
increase platelet cyclic AMP

Antimicrobials (penicillins, cephalosporins, nitrofurantoin)

Cardiovascular agents (quinidine, diurectics, vasodilators

Anticoagulants (coumadin, heparin) and thrombolytics (t-PA,
streptokinase)

Psychotropics (tricyclics/phenothiazines) and anesthetics

Chemotherapeutic agents

Miscellaneous agents (dextrans, clofibrate, ETOH, Vitamin E,
onions, garlic, ginger, fish oil)
Platelet Aggregation
Platelet
Rich
Plasma
(PRP)
+
Baseline Light
Transmission
Aggregating
Reagent
Aggregate
Clumping
Increased Light
Transmission
Typical Biphasic Pattern
Platelet
Rich
Plasma
100
90
80
70
60
50
40
30
20
10
0
Platelet
Poor
Plasma
Secondary Response (Release)
Primary Response
Lag
Injection Point
Platelet Aggregation Testing

Important in assessing risk of bleeding or
need for transfusion in active bleeding

Surgical, pre-surgical and emergency

Important in monitoring and managing
antiplatelet therapies (ReoPro, Aggrastat,
Integrilin, aspirin, etc.)

Important for monitoring platelet
destruction by mechanical means
(extracorporeal circulation)
Platelet Assessment
Quantitative – Platelet Count
 Qualitative – Platelet Aggregation

ALL now can be done with
Plateletworks
®
Plateletworks Concept

First and only test for both quantitative
and qualitative platelet assessment

Cell counter platform provides CBC with
quantitative platelet count

Addition of a platelet agonist (reagent)
causes a reaction (aggregation)
indicative of qualitative platelet function

Multiple agonists for optimal sensitivity
®
Plateletworks Procedure

Run CBC on EDTA. Note Platelet Count.

Run CBC using Plateletworks agonist
tube. Note Platelet Count which, due to
aggregation, will be reduced from first
sample.

EDTA - Agonist
x 100 = % of functional platelets
EDTA
Plateletworks Principle Overview

Baseline EDTA platelet count established
using normal CBC

All platelets in circulation quantified
Original Platelet Count
(211 x103/mm3)
Plateletworks Principle Overview

Agonist platelet count then performed using
Plateletworks agonist tube

Platelets remaining in circulation quantified
With agonist –
New count (8 x103/mm3)
Platelet Function = 96%
Result Calculation
Baseline (total plts)
Agonist (non-functional plts)
= 211,000
= 8,000
So…
Aggregated Platelets
203,000
211,000
x 100
= 203,000
= 96% Aggregation
Platelet Aggregation Correlation:
Plateletworks vs. Chronolog
Collagen
100
R = 0.91
80
ADP
60
40
100
20
y = 0.9401x
R = 0.88
P=.0001
0
0
20
40
60
80
% Aggregation Chronolog
R = 0.88
100
120
90
% Aggregation Plateletworks
% Aggregation Plateletworks
120
80
70
60
50
40
30
20
y = 0.8753x + 17.656
R = 0.91
P=.0001
10
0
0
20
40
60
% Aggregation Chronolog
80
100
Platelets and CPB

About 20% of patients undergoing CPB
bleed enough to mandate intervention


Defined as multiple transfusions
About 2 to 3% of patients will undergo
re-exploration mandated by abnormal
bleeding
Surgical source
 Severe acquired hemostatic defect source

Consequences of the Bleeding Patient







Re-operation
Delayed chest closure
Increased risk of mediastinitis or other
infection
Hypovolemia
Biventricular cardiac function
Blood product reactions (1.6% hepatitis A,
11.6% hepatitis B)
Immunologic effects (anaphylaxis or acute
lung injury)
Causes of Excessive Bleeding after CPB

Probable


Local bleeding site or acquired (mechanical or
pharmaceutical) platelet dysfunction
Possible

Preoperative drug-induced hemostatic dysfunction
(aspirin, warfarin, IIb/IIIa)

Preoperative hemostatic dysfunction

Inherited hemostatic dysfunction (vWF, platelet defect)

DIC (sepsis, low-output state)

Primary fibrino(geno)lysis
Temporary Depletion of Glycoproteins

Platelet GP are responsible for
 IIb /IIIa:
binding to each other
(cohesion or aggregation)
 Ia/Ib:
bridging platelets to the site
of injury (adhesion)
Plateletworks® Value in CPB







Assess the extent of platelet dysfunction induced
by CPB
Monitor post-op recovery of platelet aggregation
Monitor recovery / drop in platelet count
Guide transfusion decisions
Manage bleeding patients
Evaluate emergency surgery Cath Lab patients
with anti-platelet agents
FUTURE: Manage anti-platelet agents given
during beating heart procedures
CPB Clinical Highlights
Improving Patient Care: Predicting Bleeding Risk
Patient F - Bypass
90
80
70
 Negative platelet
function recovery
60
50
% Aggregation
% Aggregation
Patient J - Bypass
60
50
40
30
20
10
0
40
30
20
10
0
Pre-Pump On-Pump 1 On-Pump 2 Post Pump
Pre-Pump On-Pump 1 On-Pump 2 Post Pump
Interval
Interval
Patient NG - site 5
100
90
90
80
70
60
70
80
% aggregation ADP
% aggregation ADP
Patient EC - site 5
50
40
30
20
10
0
60
50
40
30
20
10
0
baseline
heparin
CPB
Tim e
30 min CPB Leave OR
baseline
heparin
CPB
Tim e
30 min CPB Leave OR
 Potential bleeding
risk
 These patients did
bleed and received
PLT packs
(avg. 6 units each)
CPB Clinical Highlights
Improving Patient Care: Predicting Bleeding Risk
Patient HG - site 5
Patient CB - site 5
90
120
80
% aggregation ADP
% aggregation ADP
100
80
60
40
20
70
60
50
40
30
20
10
0
0
baseline
heparin
CPB
30 min CPB Leave OR
baseline
Tim e
80
70
% Aggregation
% Aggregation
90
70
40
30
20
10
0
CPB
30 min CPB Leave OR
Patient M - Bypass
80
50
heparin
 Low bleeding
risk predicted
Tim e
Patient E - Bypass
60
 Positive platelet
function recovery
60
50
40
30
20
10
0
Pre-Pump On-Pump 1 On-Pump 2 Post Pump
Pre-Pump On-Pump 1 On-Pump 2 Post Pump
Interval
Interval
 These patients did
not bleed
 “Normal” post
operative recovery
period
CPB Clinical Highlights
Improving Patient Care: Identifying the bleeding source
Acceptable
“Working
Platelet Number”
If bleeding, not
because of
platelets
No platelet
transfusion
needed
CPB Clinical Highlights
Improving Patient Care: Identifying the bleeding source
Acceptable
“Working
Platelet Number”
If bleeding, not
because of
platelets
No platelet
transfusion
needed
CPB Clinical Highlights
Improving Patient Care: Identifying the bleeding source
“Working Platelet
Number” below
50,000!
If bleeding, most
likely due to
platelets
Platelet
transfusion
needed
CPB Clinical Highlights
Improving Patient Care: Treating the bleeding source
6 units of platelets
given
6 units Plts given
“Working Platelet
Number” now
above 50,000!
Bleeding ceases,
so platelet
transfusion
correct therapy
Anti-Platelet Monitoring
with Plateletworks
Nine parameter
hematology profile
including…
 Red Cells
 White Cells
 Platelets
 HCT
 Platelet Function
 Results in ~ 4 minutes
 Multiple clinical utilities
Clinical Experience – Plateletworks*
 CPB – monitoring patients peri-operatively
(help with decision making re: platelet transfusion;
re-operation etc.)
 PCI - evaluate PCI patients on anti-platelet
agents (including tirofiban, eptifibatide, abciximab,
clopidogrel and ASA)
 Used to identify potential drug-drug
interactions (statins-clopidogrel)
 Used to monitor platelet function in HIT
*Independent studies
Clinical Experience – Plateletworks
 A Rapid Platelet Function Assay Used to Regulate Platelet
Transfusion Prophylaxis Following Cardiopulmonary Bypass
Surgery. JECT 2004; 26(2): 145-148.
 Plateletworks Platelet Function Test Compared to the
Thromboelastograph for Prediction of Postoperative Outcomes.
JECT 2004; 36(2): 149-152.
 Point of Care Testing Shows Clinically Relevant Variation in the
Degree of Inhibition of Platelets by Standard-Dose Abciximab
Therapy During Percutaneous Coronary Intervention. Cath
Cardiovascular Interventions 2004; 62: 150-154.
 Whole Blood Point of Care Platelet Testing During Cardiac
Surgery Predicts Perioperative Bleeding. ASA, 2004.
Clinical Experience – Plateletworks
 Efficacy of High-Dose Bolus Tirofiban Compared to Regular-Dose
Glycoprotein IIb/IIIa Inhibitors on Platelet Aggregation Inhibition in
Myocardial Infarction Patients Treated with Primary Angioplasty.
ESC, August 2003.
 Impact of Angina Class on Inhibition of Platelet Aggregation
Following Clopidogrel Loading in Patients Undergoing Coronary
Intervention. Cath Cardiovascular Interventions 2003, 59: 21-25.
 Monitoring Platelet Function During Cardiopulmonary Bypass in
the Presence of Tirofiban. Soc Cardiovasc Anest, April 2003.
 Clopidogrel Poor Responders Discovered During Point-of-Care
Platelet Aggregation Testing. ACC, March 2003
Clinical Experience – Plateletworks
 Atorvastatin Reduces the Ability of Clopidogrel to Inhibit
Platelet Aggregation: A New Drug-Drug Interaction.
Circulation 2003; 107: 32 - 37.
 Contribution of Hepatic Cytochrome P450 3A4 Metabolic
Activity to the Phenomenon of Clopidogrel Resistance.
Circulation 2004; 109: r1 – r6.
 Evaluation of Platelet Count and Function in Patients Administered Tirofiban or Eptifibatide Undergoing Percunateous
Coronary Intervention. Point of Care: The Journal of
Near-Patient Testing & Technology 2004; 3(2): 66-70.
* Reprints available from www.helena.com or [email protected]
Case Studies
 Platelet protection with tirofiban and
monitoring using Plateletworks
 The regulation of platelet transfusion
prophylaxis following cardiopulmonary
bypass surgery
 Issues regarding potential clopidogrel
resistance – how to monitor and manage
Case Study - HIT
Case Study: Platelet Protection Using
the Glycoprotein IIb/IIIa Inhibitor
Tirofiban in a Patient with Heparin
Induced Thrombocytopenia
Undergoing Aortic Valve Replacement
Requiring Cardiopulmonary Bypass
Kirk E Guyer BS, David GM Carville PhD – Indiana University South Bend
Wei C Lau MD – University of Michigan Health Systems, Ann Arbor
Case Study – HIT
Heparin-Induced Thrombocytopenia


Serious clinical condition

High morbidity and mortality in cardiac
surgery patients
Associated with administration of
unfractionated heparin (UFH) or low
molecular weight heparin (LMWH)
Case Study – HIT
Heparin-Induced Thrombocytopenia

Spontaneous antibodies against heparin
bound to platelet factor 4 (PF4)

Antibody-antigen complexes result in
platelet activation and thrombin generation

Platelet count plummets with simultaneous
increase in thromboembolic events

Mesenteric and/or peripheral infarctions
lead to necrosis and amputation
Case Study – HIT
Strategies to Prevent HIT
Alternative modes of anticoagulation needed:




Danaparoid sodium
Recombinant-hirudin (bivalirudin/refludan)
Argatroban
Anti-GPIIb/IIIa agents
Case Study – HIT
AntiGPIIb/IIIa Agents for HIT

Abciximab – Fab’ – sustained anti-platelet
and potential thrombocytopenic responses
at therapeutic levels - not suitable

Eptifibatide – heptapeptide – good
pharmacokinetic profile with a short-half life

Tirofiban – non-peptide – good
pharmacokinetic profile with a short-half life
Koster et al. Anesthesiology 2001; 94(2): 245-251
Jeske et al. Thromb Haemost 1999; 82 (suppl): 389
Case Study – HIT
Monitoring AntiGP IIb/IIIa Agents



Not an approved use of anti-GP IIb/IIIa agents

Need near-patient analyzer to monitor
Need to monitor patient’s response in OR
Can’t use gold standard (PRP aggregometry)
or flow cytometry (centralized tests) in OR
Plateletworks used in this study for OR monitoring
Case Study – HIT
Case Report

84 year old female admitted for aortic valve
replacement


Previously diagnosed with HIT


UFH @ 300 units/kg with an ACT of ≥ 480 secs
GP IIb/IIIa antagonist, tirofiban, administered
to protect patient’s platelets and prevent HIT
Tirofiban infusion stopped 30 minutes prior to
termination of CPB
Case Study – HIT
Patient Monitoring

Patient’s platelet count and function
evaluated with Plateletworks

Reference platelet count performed and
compared with platelet count in the presence
of 20mM ADP

Ratio of ADP to reference tube platelet count
calculated as percent platelet aggregation

4 minute TAT
Case Study – HIT
Peri-Procedural Platelet Count
Platelets
Platelets transfused (five packs)
Case Study – HIT
Peri-Procedural Platelet Function
Post-procedural recovery
Case Study – HIT
HIT Case Study Summary
 HIT a critical concern with high-dose heparin in CPB
 Alternative anti-coagulation strategies needed
 Anti-GP IIb/IIIa agents may prove most suitable
 Tirofiban used to protect against HIT during CPB
 Plateletworks correctly assessed platelet function
even when platelet count dropped to ~ 53x103/mL
 Other systems cannot evaluate platelet function in
hemodilute / thrombocytopenic patients
Case Study – Platelet Transfusion
Case Study: A Rapid Platelet Function
Assay Used To Regulate Platelet
Transfusion Prophylaxis Following
Cardiopulmonary Bypass Surgery
Kathy E Shaffer MT (ASCP) – Aultman Blood Center, Canton, OH
David T Pearman BS – Helena Point of Care Division, Beaumont, TX
Robert S Galen MD, MPH – College of Pharmacy, Univ of GA, Athens
David GM Carville PhD – Dept of Chemistry, Indiana Univ South Bend
Case Study – Platelet Transfusion
Transfusion Triage





Blood conservation under continual scrutiny
Rising blood costs
Increasing availability issues
Improving outcome and reducing risk
Universal transfusion algorithm needed
Case Study – Platelet Transfusion
Role of the Platelet
 Open-heart surgery activates platelet cascade
– generation of thrombin
– expression of GP IIb/IIIa receptors
– aggregation and adhesion
– initiation of complement, PAF etc.
 Decreased platelet number and function
results in increased risk of bleeding
Case Study – Platelet Transfusion
Platelet Function Testing


PRP aggregometry not suited to acute setting


Platelets transfused per NIH / WHO guidelines
Other tests – flow cytometry, fibrin & d-dimer
ELISAs, TEG, etc – clinically useful but need
special equipment & training or are laborious
Platelets and other factors need to be
monitored near-patient
Case Study – Platelet Transfusion
Objective of Study

To determine if the use of a point-of-care
platelet analyzer (Plateletworks) to
evaluate platelet function and count, as
part of a complete blood count (CBC), in
post-operative CPB patients, would
enhance transfusion triage
Case Study – Platelet Transfusion
Patients and Study Protocols


310 CPB from Aug ’01 to Jan ’02

Platelet transfusion protocol based on AABB
/ WHO guidelines (and platelet evaluation)

FFP or CRYO based on observational
bleeding and/or platelet function
Post-operative “POC” evaluation of platelet
count and function
Case Study – Platelet Transfusion
Prospective & Retrospective Comparison
8/00 - 1/01 8/01 - 1/02 Difference
Retrospective
Prospective
Total CPB
Procedures
238
310
+ 72
Platelet
Packs
2676
1770
– 906
Platelet Units
per Patient
11.75
5.5
– 6.25
Case Study – Platelet Transfusion
Monthly Usage Comparison
700
Units of Platelets Transfused
Units of Platelets Transfused
600
500
400
2001/02
2000/01
300
200
100
0
Aug
Sep
Oct
Nov
Dec
Jan
Month
Total platelet savings: 906 units over 6 months
Case Study – Platelet Transfusion
Monthly Platelet Usage per Case
20
per Case
Units
Platelet
Number
of Platelets
Transfused
per Case
18
16
14
12
2001/02
2000/01
10
8
6
4
2
0
Aug
Sep
Oct
Nov
Dec
Jan
Month
Total platelet savings: 50.9% over 6 months
Case Study – Platelet Transfusion
Monthly FFP & CRYO Usage per Case
Number of Platelets Transfused per Case
25
20
FFP
CRYO
FFP
CRYO
15
10
2001/02
2001/02
2000/01
2000/01
5
0
Aug
Sep
Oct
Nov
Dec
Jan
Month
FFP and CRYO usage reduced by > 80%
Case Study – Platelet Transfusion
Summary Results


25% more CPB procedures performed



Platelet transfusions reduced by 906 units
“Near-patient” platelet count and function,
with a central lab CBC
Platelets packs per patient cut in half
FFP and CRYO usage reduced by > 80%
Case Study – Platelet Transfusion
Summary Discussion
 Effects of CPB on platelet count & function may
contribute to significant post-operative bleeding
 High morbidity & mortality without intervention
 Transfusion practices quite variable
 Recent recommendations: reduce use of
transfusion products
 Cost-benefit analyses highlight sizeable
expense associated with transfusion
Case Study – Platelet Transfusion
Conclusions
 Need rational approach to manage coagulation





disorders during CPB
Methods too laborious & complex with long TAT
Near-patient testing permits “more accurate” and
timelier intervention
Patients managed “bed-side” receive significantly
fewer blood products
Transfusion protocol / algorithm is penultimate tool
for successful transfusion triage
Additional prospective studies warranted
Case Study – Drug Interactions
Clinical Study: St. John’s Wort
Enhances the Platelet Inhibitory
Effect of Clopidogrel in Clopidogrel
“Resistant” Healthy Volunteers
Wei C Lau MD – University of Michigan, Ann Arbor
David GM Carville PhD, Kirk E Guyer BS – Univ of Indiana South Bend
Charlene J Neer BSN, MPA, Eric R Bates MD – Univ of MI, Ann Arbor
Case Study – Drug Interactions
Study Protocols

Intro: Does St John’s Wort (SJW) enhance
platelet inhibitory effect of clopidogrel in
non-responders and low-responders?

Method:
– 6 healthy clopidogrel-resistant subjects
– 14-day washout period
– 14 days x 300 mg SJW x 3 times per day
– Baseline platelet aggregation – 0 hour
– 450 mg clopidogrel administered
– Platelet aggregation @ 2, 4 & 6 hrs post
Case Study – Drug Interactions
Effect of SJW on Non-Responders
P = 0.004
P = 0.03
100
P = 0.004
95 + 2 97 + 2
79 + 11
84 + 7
84 + 7
90
Platelet Aggregation (%)
64 + 17
80
51 + 16
70
46 + 19
60
50
40
30
20
Baseline
St. John's Wort
10
0
Baseline
2 Hours
4 Hours
Time
6 Hours
Case Study – Drug Interactions
Conclusions

St John’s Wort increases CYP3A4
activity, converting clopidogrel
non-responders and low-responders
to clopidogrel responders

Herb-drug and drug-drug interactions
are pharmacologically important
Case Study Conclusions


Platelets are integral for normal hemostasis

Platelet function and count are needed for
monitoring

Platelet monitoring improves clinical
outcome and reduces costs
Patient response to anti-platelet agents is
individualized
Platelet Function Assessment


Platelet assessment has been elusive



“Rule in/rule out” source of bleeding
Platelet dysfunction key factor in CPB
bleeding and other hemorrhagic problems
Guide transfusion decisions
Monitor anti-platelet therapies
Plateletworks®