Blood Management Strategies

Preoperative Anaemia Screening

The definition. The WHO calls it anaemia below 130 g/L in men, below 120 g/L in women and below 110 g/L in pregnancy.

Which kind of iron deficiency. Order ferritin, transferrin saturation and CRP together. Ferritin alone is unreliable, because it is an acute-phase reactant and rises with any inflammation: a normal ferritin in an inflamed patient does not exclude iron deficiency.

• Absolute iron deficiency - a low ferritin. Iron stores are genuinely empty
• Functional iron deficiency, or anaemia of inflammation - a normal or high ferritin with a low transferrin saturation and a raised CRP. Stores exist, but hepcidin traps iron in the reticuloendothelial system and it cannot reach the marrow

Where the anaemia comes from. The commonest causes in elective orthopaedic patients are iron deficiency (chronic blood loss, poor intake), anaemia of chronic disease (inflammatory arthritis), and renal impairment (hip osteoarthritis patients are often elderly with CKD). Check FBC, ferritin, CRP and creatinine as a minimum.

Iron Supplementation

Route follows the deficiency. Oral iron works for absolute deficiency when there is adequate lead time of several weeks. It will not work in functional deficiency, where it is not absorbed and simply causes side effects, and intravenous iron is the answer there, as it is when there is too little time, when oral iron is not tolerated, and where there is malabsorption.

Oral iron. Target 150-200 mg elemental iron per day, and give it on alternate days rather than daily: a daily dose raises hepcidin and blunts the next one, so alternate-day dosing improves fractional absorption. With less than two weeks before surgery, oral iron is not effective.

• Ferrous sulfate 325 mg (65 mg elemental iron) TDS
• Ferrous gluconate 300 mg (36 mg elemental iron) TDS
• Ferrous fumarate 200 mg (66 mg elemental iron) TDS

Intravenous iron. Ferric carboxymaltose (Ferinject) as a 1000 mg single dose is the most common choice; iron polymaltose (Ferrosig) is given in 500 mg doses and iron sucrose (Venofer) in 200 mg doses.

Erythropoietin (EPO) Therapy

Who gets it. EPO is for selected anaemia that is not iron-deficiency anaemia, and it is always given with iron, oral or intravenous, because it is ineffective without it.

• Chronic kidney disease with anaemia (CrCl less than 30 mL/min)
• Severe anaemia (Hb less than 100 g/L) with surgery in less than 4 weeks
• Anaemia of chronic disease refractory to iron
• Jehovah's Witness patients refusing transfusion

Dose. Epoetin alfa (Eprex) 40,000 units subcutaneously weekly for 3-4 weeks, or darbepoetin (Aranesp) 150 mcg subcutaneously weekly for 3-4 weeks. Either needs weeks to work.

Side effects. Hypertension occurs in 10-20%, so monitor the blood pressure. The thrombosis risk is theoretical, with no proven increase in the orthopaedic setting. Headache and flu-like symptoms are common, and pure red cell aplasia is very rare and associated with long-term use.

Timing of Preoperative Optimisation

Lead time is the constraint. Each agent needs a minimum interval before it moves the haemoglobin, so the surgical date decides what can be offered.

Tranexamic Acid (TXA) - Evidence and Protocols

Where it is used. Give TXA in every major orthopaedic case unless contraindicated: primary THA and TKA, revision arthroplasty where blood loss is higher and TXA is highly effective, multi-level fusion and deformity correction in spine surgery, hip fracture, and trauma. It also reduces transfusion in cardiac surgery, in CABG and valve replacement.

Contraindications. Four, and each is a reason to withhold rather than to reduce the dose, apart from the last.

• Active thromboembolic disease (DVT, PE, MI or stroke less than 3 months ago)
• A history of seizures - TXA crosses the blood-brain barrier, with a rare seizure risk at high doses
• Known allergy to TXA
• Renal impairment - reduce the dose if CrCl is less than 30, because the drug accumulates

Intraoperative Cell Salvage

Indications. The blood-loss threshold varies between units, but the case mix is consistent.

• Expected blood loss greater than 500-1000 mL
• Revision THA/TKA, where high blood loss is expected
• Spine deformity correction and multi-level fusion
• Pelvic and acetabular fracture ORIF
• Jehovah's Witness patients, acceptable to many if the circuit is continuous
• Rare blood type or multiple antibodies, where crossmatch is difficult

When not to. Three contraindications are absolute and are worth carrying as a set. Two more are relative: sickle cell disease, because reinfused cells may sickle, and antibiotic-impregnated cement, for the theoretical reinfusion of antibiotic - use a leukocyte filter.

The process. Four steps, and the washing step is why only red cells come back.

1. Collection - suction shed blood into a reservoir with anticoagulant (heparin)
2. Washing - centrifugation separates the RBCs, which are washed with saline to remove debris
3. Concentration - produces an RBC concentrate (Hct 50-60%)
4. Reinfusion - filtered autologous RBCs are reinfused intravenously

Limitations. Only red cells are salvaged, with no clotting factors or platelets. A minimum of 500 mL blood loss is needed for it to be cost-effective, the equipment and technician cost $500-1000 per case, and it does not reduce allogeneic transfusion if blood loss is minimal.

Surgical Technique and Hypotensive Anaesthesia

What the operation contributes. Approach, operative time, tourniquet use, the quality of haemostasis and whether the case is a revision all change how much blood is lost.

Hypotensive anaesthesia. A controlled reduction in MAP to 50-60 mmHg reduces surgical field bleeding and total blood loss by 20-30%, and is used in spine surgery and revision arthroplasty. It requires an experienced anaesthetist, because the risk is cerebral or cardiac ischaemia, and it is contraindicated in severe coronary artery disease, cerebrovascular disease and hypertension.

The adjuncts. Drains are controversial and may increase total blood loss, so modern practice is to avoid them or remove them early (less than 24h). Fibrin sealants are expensive with minimal benefit over TXA, topical haemostatic agents (bone wax, gelatin sponges, thrombin) are useful for bone bleeding, and bipolar electrocautery gives better haemostasis than monopolar with less tissue damage.

Autologous Techniques

Why PABD fell out of favour. Donating blood preoperatively makes the patient anaemic, with the Hb dropping 10-20 g/L, and an anaemic patient is more likely to need transfusion - their own autologous unit plus allogeneic blood. 50% of donated autologous units are discarded, storage carries a bacterial contamination risk, and storage and processing cost money. Patient Blood Management with iron, EPO and TXA is superior.

What is left of it. Rare blood types with a difficult crossmatch, where cell salvage is still preferred; patients with multiple RBC antibodies; and the rare Jehovah's Witness patient who refuses allogeneic blood but accepts autologous.

Acute normovolaemic haemodilution. Immediately after induction, 1-3 units of the patient's own whole blood are withdrawn into citrate (CPD) collection bags while the volume is simultaneously replaced with crystalloid (about 3:1) or colloid (about 1:1) to keep the patient normovolaemic. The patient then bleeds dilute, lower-haematocrit blood through the high-loss part of the operation, and the collected fresh whole blood is reinfused at the end - last unit out, first back in.

What it offers that cell salvage does not. The reinfused product is fresh autologous whole blood containing functional platelets and clotting factors, where cell salvage returns washed red cells only. It is low-cost, avoids storage, and is acceptable to many Jehovah's Witness patients if a continuous circuit is maintained. It suits anticipated large blood loss with an adequate starting haemoglobin, and rare blood types or multiple antibodies.

When not to use it. Pre-existing anaemia, significant coronary or cardiac disease (the patient cannot tolerate the dilutional anaemia), severe pulmonary disease, coagulopathy, or an inability to maintain normovolaemia. Evidence for transfusion reduction is modest and ANH is used less than TXA and cell salvage.

Restrictive vs Liberal Transfusion Thresholds

Reading the table against the trials. TRICC tested 70 against 100 g/L in critically ill patients. FOCUS, the largest transfusion trial in orthopaedics, tested a threshold of 80 g/L or symptoms in elderly hip-fracture patients with cardiovascular disease or risk factors, and found no difference in death or independent walking at 60 days. So 70 g/L is the general trigger, and the 80 g/L figure is the one tested in patients whose hearts were already at risk.

The symptoms that count. These are the findings that argue for transfusion whatever the haemoglobin is.

• Tachycardia (HR greater than 100 at rest) not explained by pain or anxiety
• Dyspnoea or increased work of breathing
• Chest pain or ECG changes of ischaemia
• Postural hypotension or dizziness
• Confusion or altered mental state
• Oliguria (less than 0.5 mL/kg/h)

Massive Transfusion Protocols

The definition. Massive transfusion is the loss of one blood volume - approximately 70 mL/kg, or 5 litres in a 70 kg adult - in 24 hours, or transfusion of greater than 4 units of RBC in 1 hour, or ongoing transfusion of greater than 1 unit of RBC per hour.

Activation criteria. The trigger is the clinical picture and the anticipated need, not a haemoglobin result.

• Systolic BP less than 90 mmHg despite 2L crystalloid
• HR greater than 120 persistently
• Clinical suspicion of major haemorrhage (pelvic fracture, multiple long bone fractures, haemothorax)
• Anticipated transfusion of greater than 4 units RBC in the next hour

Blood Product Characteristics

What one unit buys you. The expected increments, which are what the post-transfusion check is measured against.

• 1 unit RBC raises Hb by approximately 10 g/L (a haematocrit increase of approximately 3%)
• 1 unit FFP raises fibrinogen by approximately 0.25 g/L, with modest correction of the INR
• 1 unit platelets (pool) raises the platelet count by approximately 30-50 x 10^9/L
• 1 unit cryoprecipitate raises fibrinogen by approximately 0.5 g/L

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Transfusion Complications

When it happens narrows what it is. The reactions are grouped below by the interval between starting the unit and the first sign.