Abdominal Surgery Rotation

Evidence-Based Blood Transfusion

Blood transfusion does not simply involve the anesthesiologist hanging pRBCs once 1000 ml of blood are in the suction container!

Correct pre-operative anemiaMinimize intra-operative blood lossOptimize blood replacement

Though these things don’t seem to be within our control we can at least go into surgery armed with some data…

Patient blood management

Difficult for anesthesiologist to have a role since we often see patients the day before surgery

Can consider:IV iron or erythropoetin

Will increase hemoglobin by 1-2 g/dL but requires 2 weeks for maximal effect

1. Correct pre-operative anemia

Things we can do:

Maintenance of normothermiaControlled hypotension

Meaning a MAP that is SAFE for the patient, not necessarily what the surgeon wants!

Consider use of regional anesthesia for pain control and BP effects

Cell salvage and re-transfusionUsually a decision made by surgeon

2. Minimize intra-operative blood loss

3. Optimize blood replacement

And now for some data…

838 ICU patients randomized to:Restrictive transfusion- pRBCs for Hgb < 7, goal 7-9Liberal transfusion- pRBCs for Hgb <10, goal 10-12

Overall 30-day mortality was similar but…

If APACHE II score was <20 (less sick pts, see next slide)Mortality was 8.7% (restrictive) vs. 16.1% (liberal)

If age was <55 yearsMortality was 5.7% (restrictive) vs. 13.0% (liberal)

If patient had acute MI or unstable anginaMortality was similar in both groups

The trial that started it all: TRICCTransfusion Requirements In Critical Care

Hebert et al. NEJM, 1999.

Rectal temperatureHRRRMAPAa gradient or PaO2pHNaK

CrHctWBCGlasgow coma scaleAgeChronic disease

APACHE II: Acute Physiologic and Chronic Health Evaluation scoring system

Higher number is worseCorrelations have been made between APACHE II score and

morbidity/mortality

Score based on 14 parameters scored 0-4 points each:

Meta-analysis of 45 cohort studies including 272,596 patients

Outcomes included mortality, multi-organ dysfunction syndrome (MODS), acute respiratory distress syndrome (ARS) & infections

In 42 studies the risk of transfusions outweighed the benefit (higher mortality & morbidity- MODS, ARDS, infections)

In 2 studies the risk was neutral (benefit = risk) In 1 study the benefit outweighed the risk

But…the only adequately powered, randomized trial on transfusion requirements is TRICC!

And then the meta-analysis…

Marik & Corwin. CCM, 2008.

But this is all in the ICU…

What about in the OR?

Does preoperative anemia in patients having major non-cardiac surgery alter morbidity and mortality?

Retrospective analysis of 227,425 patients undergoing major surgery

After controlling for other risk factors (Age, DMII, cardiac dx, COPD, CRI, cancer)

Post-op mortality at 30 days was higher in those with pre-operative Hct < 36 for females or <39 for males with an odds ratio of 1.42 (confidence interval 1.31-1.54)This means anemia increased mortality 1.42 fold!

Post-op morbidity at 30 days was higher in those with pre-operative anemia with odds ratio 1.35 (confidence interval 1.3-1.4)This means anemia increased complications 1.35 fold!

Analysis also showed increased mortality WITH blood transfusion!

Authors conclude that pre-operative anemia should be treated with iron supplementation or erythropoeitin administration (if time allows) NOT transfusion!

BUT…

Does intraoperative transfusion of 1-2 units of pRBCs in patient with Hct < 30 affect morbidity and mortality?**This study group is VERY relevant to our

practice- think of how often you transfuse “just” one or two units intraoperatively!**

Retrospective analysis of 10,100 patient undergoing general, vascular or orthopedic surgery with preoperative hct < 30

Anesthesiology. 2011.

Transfusion of 1-2 units intraoperatively increased mortality and morbidity at 30 days

Hct prior to transfusion not reported

Authors conclude that intraoperative transfusion leads to higher morbidity and mortality but it could be EITHER the transfusion or the increased surgical bleeding/complications that are the direct CAUSE!

Remember:

correlation causation

But…

Surgeons HATE to look up and see red (ie. blood hanging) without it being discussed with them

If you feel that a transfusion is indicated, discuss it with the surgery team FIRST!

On the practical side…

Single donor, volume 250-300 mlHct ~70%1 unit increases Hgb ~1g/dlTheoretically not compatible with LR because

it may chelate calcium and clotStored in:

Citrate- anticoagulant binds CaPhosphate- bufferDextrose- energy sourceAdenosine- precursor for ATP synthesis

The Basics: pRBCs

Contains coagulation factorsUse ABO-compatibleStored frozen, use within 24 hrs of thawing1 unit increases clotting factors 2-3%Can be used to treat heparin resistance

(antithrombin III deficiency) in patients requiring heparinizationMost often seen with patients going on bypass

The basics: FFP

Stored at room temperature for <5 days“6-pack” used to refer to pooling of platelets

from 6 donors which is rarely done anymoreThese days when you ask for a “6-pack” you

get an apheresis unit which has platelets from a single donor (volume 200-400ml) and will increase plt count ~ 50,000

The Basics: Platelets

Fraction of plasma that precipitates when FFP is thawed

Contains factors VIII, XIII, fibrinogen, fibronectin

1 unit contains 5 x more fibrinogen than 1 unit of FFP

Usually used to replace fibrinogen <100 mg/dl with microvascular bleeding or in patients with vWF disease

The Basics: Cryoprecipitate

1.The most common cause of mortality associated with blood transfusion is:

A. ABO hemolytic transfusion reactionB. Non-ABO hemolytic transfusion reactionC. Microbial infectionD. Transfusion associated circulatory overload

(TACO)E. Transfusion associated acute lung injury

(TRALI)

Board Review questions

E. TRALI is the most common cause of mortality associated with transfusions (51%), followed by non-ABO hemolytic transfusion reaction (20%), microbial infections (12%), ABO hemolytic transfusion reaction (7%), TACO (7%) and other (2%).

Answer

2.Which of the following is MOST likely to be a manifestation of citrate toxicity?

A. HypotensionB. Short QT interval on ECGC. Peaked T waves on ECGD. Wide pulse pressure

Board Review questions

A. Hypotension.Citrate is used as an anticoagulant in banked blood and

chelates ionized calcium. It can have the same effect on iCa in the body. The manifestations of citrate intoxication are the same as those observed with hypocalcemia:Prolonged QT, flattened T wavesDecreased contractility with hypotensionNarrowed pulse pressure Increased LVEDP, increased CVP

Normally citrate is metabolized by the liver. Can become elevated in massive transfusion, liver failure, hypothermia.

More common with FFP administrationTreat with IV calcium

Answer

Glance LG et al. Association between Intraoperative Blood Transfusion and Mortality and Morbidity in Patients Undergoing

Noncardiac Surgery. Anesthesiology. 2011; 114(2): 283-292.Hebert PC et al. A multicenter, randomized, controlled clinical

trial of transfusion requirements in critical care. NEJM. 1999; 340 (6): 409-17.

Marik PE & Corwin H. Efficacy of red blood cell transfusion in the critically ill: A systematic review of the literature. CCM. 2008; 36(9):2667-2674.

Musallam KM et al. Preoperative anaemia and postoperative outcomes in non-cardiac surgery: a retrospective cohort study. Lancet. 2011; 378: 1396–407.

Spahn DR et al. Patient blood management. Anesthesiology. 2008; 109: 951-3.

References