Red Cell Red Cell In Vivo In Vivo Recovery Recovery and Survival Studiesand Survival Studies

Richard J. Davey, MDRichard J. Davey, MDThe Methodist Hospital, Houston TXThe Methodist Hospital, Houston TXBlood Products Advisory CommitteeBlood Products Advisory Committee

May 1, 2008May 1, 2008

Evolution of Labeling and Evaluation Evolution of Labeling and Evaluation CriteriaCriteria

1947: Ross proposes 70% red cell survival at 24 1947: Ross proposes 70% red cell survival at 24 hours as a minimum recoveryhours as a minimum recovery

1950: Gray and Sterling describe 1950: Gray and Sterling describe 5151Cr as a red cell Cr as a red cell labellabel

1967: Fisher describes 1967: Fisher describes 99m99mTc as a red cell labelTc as a red cell label 1985: Minimum survival raised to 75% following FDA 1985: Minimum survival raised to 75% following FDA

workshopworkshop 1989: AuBuchon refines use of 1989: AuBuchon refines use of 111111In as a red cell labelIn as a red cell label 1998: Minimum survival 1998: Minimum survival ≥ 75%: SD ≤ 9% based on ≥ 75%: SD ≤ 9% based on

historical datahistorical data 2004: Current criteria based on historical data, BPAC2004: Current criteria based on historical data, BPAC

Characteristics of an Ideal Red Cell Characteristics of an Ideal Red Cell RadiolabelRadiolabel

Minimal preparative manipulation of red Minimal preparative manipulation of red cellscells

Specific for red cellsSpecific for red cells Nontoxic to the cellNontoxic to the cell Nontoxic to the recipientNontoxic to the recipient No metabolism by red cellsNo metabolism by red cells No elution from the cellNo elution from the cell Radioactive half-life appropriate for the Radioactive half-life appropriate for the

duration of the studyduration of the study No relabeling of other cellsNo relabeling of other cells

Characteristics of Commonly Used Characteristics of Commonly Used Red Cell RadiolabelsRed Cell Radiolabels

CharacteristicCharacteristic 5151Cr Cr 99m99mTcTc 111111InIn

Half-lifeHalf-life 27.7 days27.7 days 6.0 hours6.0 hours 2.8 days2.8 days

ElutionElution 1% day1% day 4% hour4% hour 4% day4% day

Major Major γγ-photon-photon 320 keV320 keV 140 keV 173,247 140 keV 173,247 keVkeV

emissionsemissions

Suitable for imaging NoSuitable for imaging No YesYes YesYes

Technical Steps for Labeling Red Cells Technical Steps for Labeling Red Cells with with 5151 Cr Cr

A suitable sample of red cells stored A suitable sample of red cells stored under experimental condition is under experimental condition is chosen. For autologous studies,chosen. For autologous studies,

~ 15ml is used.~ 15ml is used. An amount of An amount of 5151 Cr is used to insure Cr is used to insure

minimum adequate counts minimum adequate counts throughout the study (~ 4000 throughout the study (~ 4000 counts/sample: 5 to 20 counts/sample: 5 to 20 μμCi)Ci)

After incubation with test red cells, After incubation with test red cells, unbound unbound 5151 Cr is removedCr is removed

An appropriate standard is prepared An appropriate standard is prepared for blood volume determinationfor blood volume determination

Labeled red cells are infused into a Labeled red cells are infused into a peripheral vein and exact volume of peripheral vein and exact volume of infused material is determinedinfused material is determined

Technical Steps for Labeling Red Cells Technical Steps for Labeling Red Cells with with 5151 CrCr

Samples are drawn Samples are drawn from opposite arm. from opposite arm. Several early samples Several early samples are drawn for 100% are drawn for 100% survival survival determination.determination.

Samples counted in Samples counted in duplicate and duplicate and corrected for elution.corrected for elution.

Early Loss of Labeled, Stored Red Cells Early Loss of Labeled, Stored Red Cells After InfusionAfter Infusion

Zero-Time Determination by Direct Red Cell Zero-Time Determination by Direct Red Cell Mass Measurement (Mass Measurement (99m 99m Tc) and by Back-Tc) and by Back-

Extrapolation (Extrapolation (51 51 Cr)Cr)

Partial List of Red Cell Products Partial List of Red Cell Products Evaluated Using Red Cell Recovery Evaluated Using Red Cell Recovery

StudiesStudies

New plastics and plasticizersNew plastics and plasticizers New anticoagulant/preservativesNew anticoagulant/preservatives Filtration devices and leukoreduced Filtration devices and leukoreduced

productsproducts Irradiated red cellsIrradiated red cells ““Undercollected” red cell unitsUndercollected” red cell units Pathogen inactivation proceduresPathogen inactivation procedures Enzymatic removal of A and B Enzymatic removal of A and B

antigensantigens

Effect of Prestorage Irradiation on 24-Effect of Prestorage Irradiation on 24-hour Posttransfusion Red Cell Recoveryhour Posttransfusion Red Cell Recovery

Storage IntervalStorage Interval 21 Days 21 Days11 28days 28days11 42 Days 42 Days22

Radiation doseRadiation dose 20 Gy 20 Gy 30 Gy 20 Gy 20 Gy 30 Gy

Control IrradControl Irrad. . Cont. IrradCont. Irrad Cont. IrradCont. Irrad..

Potassium (mEq/L) Potassium (mEq/L) 36.6 63.4 47.7 69.4 42.6 78.1 36.6 63.4 47.7 69.4 42.6 78.1

ATP (ATP (μμM/g Hb)M/g Hb) 3.6 3.6 3.2 3.8 3.5 2.1 1.9 3.2 3.8 3.5 2.1 1.9

RBC 24 hr recovery (%)RBC 24 hr recovery (%) 90.4 82.2 85.0 80.7 90.4 82.2 85.0 80.7 78.4 78.4 68.568.5

1. Friedman et al. Transfusion 1991;31:50S1. Friedman et al. Transfusion 1991;31:50S

2. Davey et al. Transfusion 1992:32:525-82. Davey et al. Transfusion 1992:32:525-8

Evolution of Labeling and Evaluation Evolution of Labeling and Evaluation CriteriaCriteria

1947: Ross proposes 70% red cell survival at 24 1947: Ross proposes 70% red cell survival at 24 hours as a minimum recoveryhours as a minimum recovery

1950: Gray and Sterling describe 1950: Gray and Sterling describe 5151Cr as a red cell Cr as a red cell labellabel

1967: Fisher describes 1967: Fisher describes 99m99mTc as a red cell labelTc as a red cell label 1985: Minimum survival raised to 75% following FDA 1985: Minimum survival raised to 75% following FDA

workshopworkshop 1989: AuBuchon refines use of 1989: AuBuchon refines use of 111111In as a red cell labelIn as a red cell label 1998: Minimum survival 1998: Minimum survival ≥ 75%: SD ≤ 9% based on ≥ 75%: SD ≤ 9% based on

historical datahistorical data 2004: Current criteria based on historical data, BPAC2004: Current criteria based on historical data, BPAC

FDA Requirements for Approval of FDA Requirements for Approval of Red Blood Cell ProductsRed Blood Cell Products

Total 20 or more evaluable 24-hour recoveriesTotal 20 or more evaluable 24-hour recoveries Minimum two laboratoriesMinimum two laboratories Sample mean Sample mean ≥ 75%≥ 75% Sample standard deviation ≤ 9%Sample standard deviation ≤ 9% One-sided 95% lower confidence limit for the One-sided 95% lower confidence limit for the

proportion of successes must be >70% with proportion of successes must be >70% with success threshold for individual recovery ≥ 75%.success threshold for individual recovery ≥ 75%. A successful trial can have no more than 3 of 24 RBC A successful trial can have no more than 3 of 24 RBC

recoveries below 75%recoveries below 75% Hemolysis < 1% at end of storageHemolysis < 1% at end of storage Comparison, control vs. test: ATP, 2,3 DPG, pH, Comparison, control vs. test: ATP, 2,3 DPG, pH,

glucose, lactateglucose, lactate

The Problem With “Old” BloodThe Problem With “Old” Blood

Mechanisms of Morbidity and Mortality: Mechanisms of Morbidity and Mortality: The Red Cell Storage Lesion The Red Cell Storage Lesion

Storage LesionStorage Lesion

Decreased 2,3 DPGDecreased 2,3 DPG Increased rigidityIncreased rigidity High PA I levelHigh PA I level Poor O Poor O2 transport High CD 40High CD 40 Inflammation Inflammation NO depletionNO depletion Thrombosis Thrombosis Increase in IL-10Increase in IL-10 Decrease in TNF-Decrease in TNF-αα

Depletion of 2,3 DPGDepletion of 2,3 DPG

Loss of RBC DeformabilityLoss of RBC Deformability

Storage Depletes RBC Nitric Oxide Storage Depletes RBC Nitric Oxide BioactivityBioactivity

Outcomes: Liberal vs. Restrictive Outcomes: Liberal vs. Restrictive TransfusionsTransfusions

Outcome MeasureOutcome Measure Restrictive (Restrictive (n=418) n=418) LiberalLiberal (n=420) (n=420) p p valuevalue

(Hb: 7.0-9.0)(Hb: 7.0-9.0) (Hb: 10.0-12.0) (Hb: 10.0-12.0)

Death (# / %)Death (# / %) 30 day30 day 78 (18.7) 78 (18.7) 98 (23.3)98 (23.3) 0.110.11 ICUICU 56 (13.4) 56 (13.4) 68 (16.2) 0.2968 (16.2) 0.29 HospitalHospital 93 (22.2) 118 (28.1) 0.05 93 (22.2) 118 (28.1) 0.05

Length of stay – daysLength of stay – days ICUICU 11.0 11.0 ± 10.7 11.5 ± 11.3 0.53± 10.7 11.5 ± 11.3 0.53 Hospital 34.8 ± 19.5 35.5 ± 19.4 Hospital 34.8 ± 19.5 35.5 ± 19.4

0.580.58

Hebert PC, et al. New Engl J Med 1999;340:409.Hebert PC, et al. New Engl J Med 1999;340:409.

Factors Associated With Postoperative Factors Associated With Postoperative Morbidity Morbidity Post-CABGPost-CABG

VariableVariable Odds RatioOdds Ratio Upper CLUpper CL Lower CLLower CL p p valuevalue

TransfusionTransfusion PRBC, unitsPRBC, units 1.73 1.73 1.67 1.80 <.0001 1.67 1.80 <.0001

PreoperativePreoperative Higher BMIHigher BMI 1.05 1.04 1.07 1.05 1.04 1.07

<.0001<.0001 Abnormal LVEF 1.62 1.33 1.98 <.0001Abnormal LVEF 1.62 1.33 1.98 <.0001 Peripheral vasc. disease 1.54 1.21 1.95 .0004Peripheral vasc. disease 1.54 1.21 1.95 .0004 Previous stroke 1.55 1.14 2.11 . 0051Previous stroke 1.55 1.14 2.11 . 0051

““Perioperative RBC transfusion is the single factor most reliably Perioperative RBC transfusion is the single factor most reliably associated with postoperative morbid events”associated with postoperative morbid events”

Koch GC et al. Crit Care Med 2006;34;1608Koch GC et al. Crit Care Med 2006;34;1608

HypothesisHypothesis Serious complications and mortality after cardiac surgery Serious complications and mortality after cardiac surgery

may increase when red cell units are transfused after may increase when red cell units are transfused after they have been stored for more than 2 weeksthey have been stored for more than 2 weeks

Patients underwent coronary-artery bypass grafting, cardiac-Patients underwent coronary-artery bypass grafting, cardiac-valve surgery, or a combination of the two proceduresvalve surgery, or a combination of the two procedures

6002 patients studied from June 30, 1998 to January 30, 6002 patients studied from June 30, 1998 to January 30, 20062006

All serious morbid events evaluatedAll serious morbid events evaluated When blood was ordered for transfusion, the blood bank When blood was ordered for transfusion, the blood bank

provided the oldest available matching unit for each request provided the oldest available matching unit for each request (FIFO)(FIFO)

Median time of storage was 15 daysMedian time of storage was 15 days

ConclusionsConclusions

Patients given older blood:Patients given older blood: Greater in-hospital mortality (2.8% vs. Greater in-hospital mortality (2.8% vs.

1.7%, P < 0.004)1.7%, P < 0.004) More likely to need prolonged ventilatory More likely to need prolonged ventilatory

support (9.7% vs. 5.6%, P<0.001)support (9.7% vs. 5.6%, P<0.001) More likely to have renal failure (2.7% vs. More likely to have renal failure (2.7% vs.

1.6%, P < 0.003)1.6%, P < 0.003) Increased sepsis (4.0% vs. 2.8%, P < Increased sepsis (4.0% vs. 2.8%, P <

0.01)0.01) Increased multisystem organ failure Increased multisystem organ failure

(0.7% vs. 0.2%, P < 0.007)(0.7% vs. 0.2%, P < 0.007)

Red Cell Recoveries in Clinical Trials: Red Cell Recoveries in Clinical Trials: Where Should We Set the Bar?Where Should We Set the Bar?

Technical labeling procedures are well established and Technical labeling procedures are well established and performed by skilled laboratoriesperformed by skilled laboratories

Prudent to be cautious in liberalizing threshold valuePrudent to be cautious in liberalizing threshold value Do not want to set bar so Do not want to set bar so highhigh as to lead to unnecessary as to lead to unnecessary

trial failures. (67.3% historical success rate for liquid trial failures. (67.3% historical success rate for liquid products @ 75% threshold value)products @ 75% threshold value)

Do not want to set the bar so Do not want to set the bar so lowlow as to have almost 100% as to have almost 100% success. (99.9% historical success for liquid products @ success. (99.9% historical success for liquid products @ 67% threshold)67% threshold)

Alternatives: Alternatives: 70%70% threshold value threshold value = 95.5% historical success (liquid = 95.5% historical success (liquid

storage)storage) 72 -73%72 -73% threshold value? threshold value?

Davey RJ. Editorial. Davey RJ. Editorial. TransfusionTransfusion. In press.. In press.