Physiological triggers Physiological triggers for blood Transfusion in for blood Transfusion in

the ICUthe ICU

Dr. T.R. ChandrashekarDr. T.R. ChandrashekarIntensivistIntensivist

K.R.HospitalK.R.HospitalBangaloreBangalore

Some facts about Blood Some facts about Blood transfusiontransfusion

Only absolute indication is to increase oxygen delivery to Tissues in anaemic patients- ie to increase oxygen carrying capacity.

It is a tissue transplantation procedure

Blood should not be used for intravascular

volume expansion

Transfusion Trigger

Acceptable hemoglobin concentration Acceptable hemoglobin concentration

Risk of blood transfusionRisk of blood transfusion Risk of low hemoglobinRisk of low hemoglobin

Oxygen transport Oxygen transport physiology physiology

Oxygen transport Oxygen transport physiologyphysiology

Oxygen to mitochondria is the goalOxygen to mitochondria is the goal We accept low Hb in critically ill We accept low Hb in critically ill

patients because increasing the Hb with patients because increasing the Hb with old stored blood increases mortality.old stored blood increases mortality.

Because of low Hb –the oxygen content Because of low Hb –the oxygen content is lowis low

Hence we should we should be certain Hence we should we should be certain all along the oxygen cascade-Lung to all along the oxygen cascade-Lung to mitochondria, the system is able to mitochondria, the system is able to increase the delivery/extract oxygenincrease the delivery/extract oxygen

OxygeOxygendelivndeliv

eryery CaO2 = (1.34 x Hb x SaO2) +dissolved O2

DO2 = CO X CaO2

Cardiac output= HR x SV

Mitochondria in end organs

Oxygen extraction/ Oxygen extraction/ reservereserve

Sao2 95-98%/Co=5L/mtSao2 95-98%/Co=5L/mt At Hb of 15 g % Oxygen content is At Hb of 15 g % Oxygen content is

1000 ml1000 ml At Hb of 10 g % Oxygen content is At Hb of 10 g % Oxygen content is

698 ml698 ml At Hb of 7 g % Oxygen content is 445 At Hb of 7 g % Oxygen content is 445

mlml At this Hb we have reduced the At this Hb we have reduced the

reservereserve

Do2/Vo2Do2/Vo2 CO/Oxygen saturation remain CO/Oxygen saturation remain

constantconstant

Hb 7 g%Hb 7 g%

225ml normal O2 utilisation

Reserve

Cannot be utilised

225ml normal O2 utilisation/ No reserve

Hb 15g%

DO2/VO2DO2/VO2

Patients have to be kept them well above the Critical Point so that oxygenation of any tissue is not compromised

Supply dependent

area

In critically ill supply dependent

area

Factors that may result in a patient being potentially closer

to the critical point than normal Reduced oxygen delivery.

(a) Decreased cardiac output:(i) Pre-morbid disease e.g.,IHD, valvular heart

disease.(ii) Hypovolaemia e.g., increased capillary leak.(iii) Arrhythmias e.g., atrial fibrillation.(iv) Pulmonary embolism.(v) Specific heart muscle disease e.g., systemic

inflammatory response syndrome (SIRS) related cardiomyopathy.

(b) Hypoxaemia secondary to acute respiratory failure.-(ALI)/ (ARDS).

Factors that may result in a patient being potentially

closer to the critical point than normal

Pain, stress, anxiety.

Shivering.Fever.Severe infection.Sepsis/(SIRS).Trauma

Surgery.Burns.Adrenergic drug

infusions.Work of breathing

e.g., during weaning.

Convulsions.

Increased oxygen consumption

Does old blood improve Does old blood improve oxygen content?oxygen content?

Storage Defects and Microvascular Perfusion

Decreased 2,3- DPG, ADP,NOBuild-up of cytokines, Free Hb, K+, debrisPoor deformability

Will they improve oxygen content and delivery ?

Immune suppression

Infections

Clinical and animal studies report contradictory findings about the oxygenation capacity of

stored RBCs

Transfusion “Trigger” Controversy

Transfusion trigger:“a particularhemoglobin level ofdiscomfort in thePrescribing physician, Not defined by clearPhysiologic parameters”

8/24?

7/21?

10/30?

Transfusion paradigms

Sources of Variation in Transfusion Practice

Physician practice variation Physicians make highly individualized trade-

off decisions between the risks of anemia vs. the risks and benefits of transfusion

Several studies show this individualization is more aligned with the physician’s bias rather than physiologic status of the patient

This decision is often based more upon custom and habit rather than formal training and current evidence based principles

Transfusion triggerTransfusion trigger

(Crit Care Med 2009; 37:3124 –3157)

Recommendations Regarding Indications for RBC Transfusion in

the General Critically Ill Patient

RBC transfusion is indicated for patients with evidence of hemorrhagic shock. (Level 1)

RBC transfusion may be indicated for patients with evidence of acute hemorrhage and hemodynamic instability or inadequate oxygen delivery. (Level 1)

Indications for RBC Transfusion in the General Critically Ill Patient

A “restrictive” strategy of RBC transfusion (transfuse when Hb <7 g/dL) is as effective as a “liberal” transfusion strategy (transfusion when Hb < 10 g/dL) in critically ill patients with hemodynamically stable anemia, except possibly in patients with acute myocardial ischemia. (Level 1)

In critically ill pts on the ventilator, the above also holds true. LEVEL II

In resuscitated, critically ill trauma pts, the above holds true. LEVEL II

In critically ill patients with stable cardiac disease, the above holds true. LEVEL II. (very important: prevention of ischemia not supported by literature)

Anemia in the ICUAnemia in the ICU 95% of ICU patients have anemia by Day 395% of ICU patients have anemia by Day 3 The anemia typically persists throughout the The anemia typically persists throughout the

ICU and hospital stayICU and hospital stay ~50% patients admitted to ICU’s in USA ~50% patients admitted to ICU’s in USA

receive transfusionsreceive transfusions ~85% patients who stay in ICU > 1 week ~85% patients who stay in ICU > 1 week

receive transfusionsreceive transfusions On average, 9.5 units of PRBC per patientOn average, 9.5 units of PRBC per patient 40% during the first week40% during the first week 60% ongoing “need” for transfusion @ 2-3 60% ongoing “need” for transfusion @ 2-3

units/weekunits/week Acute blood loss accounts for only 35% of Acute blood loss accounts for only 35% of

transfusion eventstransfusion events Why does patients become Anaemic in ICU?

Causes of Anemia in the Causes of Anemia in the Critically IllCritically Ill Diagnostic phlebotomy (~ 750-900 mL/ICU stay)Diagnostic phlebotomy (~ 750-900 mL/ICU stay)

Average 40-60 mL/day/Accounts for 20% of total Average 40-60 mL/day/Accounts for 20% of total blood lossblood loss

Occult and overt bleeding: wounds, drains & GI tractOccult and overt bleeding: wounds, drains & GI tract Anemia due to underproductionAnemia due to underproduction

Blunted erythropoietin response to low HctBlunted erythropoietin response to low Hct Cytokines (IL-1Cytokines (IL-1, TNF-, TNF-) inhibit erythropoietin ) inhibit erythropoietin

genegene Inflammatory processes in the ICUInflammatory processes in the ICU Altered iron metabolismAltered iron metabolism Impaired proliferation and differentiation of Impaired proliferation and differentiation of

erythroid progenitorserythroid progenitors Hematologically similar to anemia of chronic disease Hematologically similar to anemia of chronic disease

(low iron, low TIBC, normal/high ferritin)(low iron, low TIBC, normal/high ferritin)

Physiological triggerPhysiological trigger

The use of a single hemoglobin “trigger” for all patients is not recommended

Decision for RBC transfusion should be based on an individual patient’s intravascular volume status, evidence of shock, duration and extent of anemia, and cardiopulmonary physiologic parameters. (Level 2)

Physiological triggerPhysiological trigger

It is obvious that for any individual the clinician cannot know where the Critical Point lies nor know how close to the Critical Point a patient can go.

What the clinician does know are the factors involved and the overt pathophysiology in an individual patient which are likely to influence their proximity to the Critical Point.

The physiologic effect of anemia

Is clinically assessed by examination of indicators of

Global and organ-specific oxygen delivery.

How well is anemia How well is anemia tolerated?tolerated?

Are the compensatory Are the compensatory mechanisms working?mechanisms working?

Is their a Tissue oxygen Is their a Tissue oxygen deficit?deficit? SymptomsSymptoms

Rate Pressure product-Heart compensationRate Pressure product-Heart compensation Global oxygenation parametersGlobal oxygenation parameters Scvo2/lactateScvo2/lactate Tissue oxygenation parametersTissue oxygenation parameters

Gastric tonometryGastric tonometryP300 latencyP300 latencyS-T segment analysisS-T segment analysis

Anemia symptomsAnemia symptoms

Exertional dyspnea Chest pain Lethargy Pallor Hypotension Tachycardia Impaired consciousness

Points to consider before Points to consider before Blood transfusionBlood transfusion

Hemodynamic status, Rate of ongoing blood loss Likelihood of further blood loss Evidence of end-organ compromise Risk of CAD Balance of risks vs. benefits of transfusion These findings will determine the urgency

of response and will determine whether or not transfusion is indicated

Three possible scenarios Three possible scenarios in ICUin ICU

Acute bleedAcute bleed Septic shock during resuscitationSeptic shock during resuscitation Hemodynamicaly stable euvolemic Hemodynamicaly stable euvolemic

anemia in critically ill patient anemia in critically ill patient

Acute bleed Acute bleed

Patient with esophageal varices and portal hypertension- with bleeding (1L)

Baseline Hb 8g%Baseline Hb 8g%

Blood transfusion before the hematocrit drops and prior to endoscopic intervention

Septic shock-EGDTSeptic shock-EGDT

Hemodynamically stable Hemodynamically stable critically ill patientcritically ill patient

IssuesIssues Hemodilution Hemodilution

CaO2 = (1.34 x Hb x SaO2) +dissolved O2

DO2 = CO X CaO2

Cardiac output

Mitochondria in end organs

7 g % ALI/ARDS

PE

Sepsis induced myocardial depression

Drugs

Inotropes

Pericardial effusion

vv

MMDS-cannot extract O2 O2

lactateCO2

vvaa

Case scenario…Case scenario…

20 year old male patient with APD-20 year old male patient with APD-accidental phenol ingestion vitals stable accidental phenol ingestion vitals stable Hb 8.6 g% had a bout of coffee ground Hb 8.6 g% had a bout of coffee ground aspirationaspiration

Endoscopy done -bleeder clippedEndoscopy done -bleeder clipped Vitals stableVitals stable Hb 6.9 g %Hb 6.9 g %

Do we transfuse ?Do we transfuse ?

Case scenario…Case scenario…

45 year old 70 kg diabetic admitted 45 year old 70 kg diabetic admitted with H1N1 ARDS, Day 6with H1N1 ARDS, Day 6

On ventilator PEEP14 cms H2o/ FIO2 On ventilator PEEP14 cms H2o/ FIO2 70%70%

Vt 300ml, plateau pressure 30 cms H2oVt 300ml, plateau pressure 30 cms H2o Pco2 75/Po2 53/Sao2 86%Pco2 75/Po2 53/Sao2 86% Vitals stable, febrile, Scvo2 58%Vitals stable, febrile, Scvo2 58% Hb 7.3 g %Hb 7.3 g % Do we transfuse ?Do we transfuse ?

Case scenario…Case scenario…

65 year old septic patient with Scvo2 65 year old septic patient with Scvo2 of 55%of 55%

With IHD -Ef 45% on two inotropes With IHD -Ef 45% on two inotropes BP 110/54 admission Hb 8.2 g%, Hr BP 110/54 admission Hb 8.2 g%, Hr 120/mt, mild ST elevation in chest 120/mt, mild ST elevation in chest leads consistent with old ECG leads consistent with old ECG findingsfindings

Do we transfuse?Do we transfuse? YESYES

Case scenario…Case scenario…

45 year old DM with Fournier's 45 year old DM with Fournier's Gangrene has BP of 102/49 on Gangrene has BP of 102/49 on dobutamine, noradrenaline high dobutamine, noradrenaline high doses, on ventilator Pao2-125 doses, on ventilator Pao2-125

HR 134/mt SCvo2 49% CO-7L/mtHR 134/mt SCvo2 49% CO-7L/mt Hb is 10.2 g %Hb is 10.2 g % What do we do?What do we do? MMDSMMDS

Recommendations Regarding Recommendations Regarding Strategies to Reduce RBC Strategies to Reduce RBC

TransfusionTransfusion The use of low-volume adult or pediatric The use of low-volume adult or pediatric

blood sampling tubes blood sampling tubes The use of blood conservation devices for The use of blood conservation devices for

reinfusion of waste blood with diagnostic reinfusion of waste blood with diagnostic sampling sampling

Intraoperative and postoperative blood Intraoperative and postoperative blood salvage salvage

Alternative methods for decreasing Alternative methods for decreasing transfusion may lead to a significant transfusion may lead to a significant reduction in allogeneic blood usage. reduction in allogeneic blood usage.

Conclusion Conclusion

Though strengthening of the position of thresholds and their application almost mandates that any

special circumstances, such as the unstable patient, the dynamics of surgical bleeding or those at risk of covert cardiovascular problems

Require close monitoring and individualized trade-off decisions between the risks of anemia vs.

the risks and benefits of transfusion

Require close monitoring and individualized trade-off decisions between the risks of anemia vs.

the risks and benefits of transfusion