Blood Conservation
Blood Conservation
Blood Conservation
Edited by: Dr. Fran Smith, Anaesthetic Consultant, North Bristol Trust, UK, and Dr.
Gregory Klar, Associate Professor, Queen’s Hospital, Canada
†
Corresponding author e-mail: yolandesquire@doctors.org.uk
KEY POINTS
Blood conservation techniques reduce the risk associated with blood transfusion and improve patient outcomes.
Strategies should be patient specific and include preoperative optimisation of haemoglobin, management of
comorbidities and medications, intraoperative blood preservation techniques, and careful postoperative management.
A multidisciplinary and multimodal approach is key to effective blood conservation.
INTRODUCTION
Perioperative anaemia is a common finding in surgical patients. It occurs in 20% to 40% of cases and is a specific indicator for
increased postoperative morbidity and mortality.1,2 Anaemia is defined by the World Health Organisation (WHO) as
haemoglobin (Hb) concentration ,130 g/L for men, ,120 g/L for women, and ,110 g/L for pregnant women. Historically, red
blood cell (RBC) transfusion has been generously used to treat perioperative anaemia and blood loss; however, it has since
been shown that a restrictive strategy for red cell transfusion is as effective, if not superior, to liberal transfusion in many
critically ill patients.3 It is also important to remember some of the risks associated with transfusion (see Table 1). In 2016, the
Serious Hazards of Transfusion (SHOT) report found that 87% of serious complications were related to human error.
Pulmonary complications and transfusion-associated circulatory overload were the most common causes of death and
morbidity.4
In 2010 the WHO targeted avoidable transfusion by improving patient blood management. It aimed to provide guidance,
training, and support for the safe and rational use of blood products and therefore minimise unnecessary exposure to blood
products. It targeted 3 pillars of care (see Figure 1).2
These pillars of care can be best addressed by considering the patients’ surgical journey, from preoperative, to intraoperative,
through postoperative recovery. We must take a combined approach depending on individual patient requirements and the
nature of the intended surgery.
In 2012, a study in Yorkshire looked at the implementation of a local blood management programme for more than 700 hip and
knee replacements. They introduced a preoperative algorithm for identifying and treating anaemia and intraoperative guidelines
on blood conservation strategies. This was found to reduce the prevalence of anaemia at the time of surgery from 26% to 10%.
Perioperative blood loss also fell by 20%; the transfusion rate for total hip arthroplasty went from 23% to 8% and for total knee
arthroplasty from 8% to 0%.5
It is important to remember that for some patients, blood conservation may also be the only option in managing perioperative
anaemia. For example, the Jehovah’s Witnesses blood doctrine specifically prohibits procedures involving blood ingestion or
transfusion. This includes the use of RBCs, white cells, platelets, or plasma.
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* Hypothermia
* Thrombophlebitis
* Citrate toxicity
* Iron overload
Figure 1. The 3 pillars of care in safe and rational use of blood products.2
PREOPERATIVE STRATEGIES
A patient-specific risk assessment for transfusion should be carried out for all patients but is especially important for those in
whom there is potential for high blood loss during surgery, for example, cardiac, spinal, or major lower-limb procedures.
Preoperative optimisation includes the identification and treatment of preoperative anaemia with consideration of patient
comorbidities such as ischaemic heart disease and the appropriate management of perioperative anticoagulation.
production is provided mainly by macrophages recycling iron from degraded RBCs, whilst daily absorption of 1 to 2 mg replaces
extra losses. Increased requirement, limited supply, and blood loss can all lead to a true deficiency. Patients can also have a
functional iron deficiency, in which increased hepcidin levels, due to infectious or inflammatory diseases, ageing, or chronic
disease, inhibit ferroportin and prevent iron release from macrophages despite adequate total body stores.7
Where there are true low iron levels, early correction with iron replacement treatment is optimal. This can be oral iron such as
ferrous sulphate, ferrous fumarate, or ferrous gluconate, and the body can absorb up to 6 mg/d. Parenteral iron therapy can be
used if there is a functional iron deficiency or if oral treatment is not tolerated or is ineffective or when time is limited for adequate
replacement. An increase in Hb is seen within 2 weeks of parenteral iron therapy and is maximal at approximately 6 weeks.8
Erythropoiesis-stimulating agents (ESA) may also be of benefit to increase RBC production. A short preoperative regimen of
ESA or even a single dose alongside parenteral iron has been shown to be successful in both cardiac and noncardiac surgeries
for reducing transfusion rates.9
Other causes of anaemia once identified can be treated with replacement of the relevant component, for example, vitamin B12
or folic acid, or involve more specific management plans from the haematologist.
Anticoagulants
Many patients take medications that interfere with coagulation and can lead to a higher risk of perioperative bleeding. Examples
in common use include aspirin, clopidogrel, warfarin, and direct oral anticoagulant drugs, such as rivaroxaban, apixaban, and
dabigatran. It is important to balance the risks and benefits of stopping these medications perioperatively depending on the
thromboembolic versus intraoperative bleeding risk, and this may require a multidisciplinary discussion between the
anaesthetist, surgeon, haematologist, and cardiologist to make a detailed plan (Table 3). If the risk of stopping treatment is
high, then bridging therapy can also be considered using a shorter-acting heparin to cover the immediate operative period.
Intraoperative
Reducing blood loss intraoperatively involves a multidisciplinary approach and ongoing communication with the surgical team.
Individualised goal-directed interventions are important in minimising the need for transfusion. These include combined
consideration of patient positioning, thermoregulation, regional anaesthesia, blood pressure management, operative
techniques, haemodilution, cell salvage, and the use of antifibrinolytics.
Patient Positioning
Circulatory changes induced by the perioperative positioning of patients can be used to reduce or increase blood loss by
promoting or opposing venous drainage in a field. Venous drainage axes should not be compressed, as this can lead to
Thermoregulation
Hypothermia, which is defined as a core temperature of less than 368C, can lead to altered enzyme function in the clotting
cascade, including effects on fibrinolysis and reduced platelet function.10 The combination of these factors may result in
abnormal haemostasis with an increased risk of intraoperative bleeding. Hypothermia also leads to an increase in Hb oxygen
affinity, reduced cardiac output, and ultimately a reduction in tissue oxygenation.
Regional Anaesthesia
Loss of sympathetic tone as a result of regional anaesthesia may help reduce the arterial and peripheral venous blood pressure
in the surgical field, resulting in less intraoperative blood loss. A meta-analysis of 66 studies in 2006 showed that spinal or
epidural anaesthesia was associated with a significant decrease in the estimated blood loss (at the end of the procedure) when
compared with a general anaesthetic.11
Operative Techniques
A proactive approach to managing bleeding and preventing ongoing loss is crucial to blood conservation. Preventative
measures such as tourniquets can be considered, especially with lower-limb surgery, ensuring that the duration of ‘‘tourniquet
time’’ and pressure is clearly monitored to avoid muscle and nerve damage.13 Vessel ligation should be proactive rather than
reactive. Other methods to stop bleeding early include pressure, ligation, diathermy, and topical vasoconstrictors (eg, use of
adrenaline-soaked swabs and the use of fibrin glues).
Haemodilution
Haemodilution may be either normovolaemic or hypervolaemic. Normovolaemic haemodilution involves removing a patient’s
blood and replacing it with crystalloid to maintain intravascular volume. The haematocrit is low; tissue perfusion and blood flow
are high due to low plasma viscosity. Blood loss intraoperatively will contain fewer RBCs. Once the blood loss has stopped, the
patient’s own blood can then be returned.
Hypervolaemic haemodilution is dilution of the blood volume without withdrawing blood first, aiming for a lower haematocrit to
prevent overall loss of RBCs if bleeding occurs and to maintain tissue perfusion. Care to avoid circulatory overload must be
taken, especially in patients with reduced cardiac function. Haemodilution is not commonly employed.
Cell Salvage
Where major blood loss might be expected, collection, processing, and reinfusion of autologous blood is becoming more widely
used and accessible14 (Figure 2).
A recent study showed that 53% of UK hospitals now use cell salvage. Indications include anticipated loss of .1000 mL or 20%
of estimated blood volume, increased risk factors for bleeding, patients with rare blood types or antibodies, and patients who
refuse to receive donor blood.14
Drawbacks of cell salvage include appropriate training of personnel and the many relative contraindications (see Table 4).
Antifibrinolytics
Tranexamic acid is an antifibrinolytic used increasingly during surgery to decrease blood loss by helping to prevent the
breakdown of fibrin and promoting the maintenance of blood clots. Many trials have demonstrated its effectiveness; the
WOMAN trial published in April 2017 was an international randomized controlled trial looking at postpartum haemorrhage in
more than 20 000 women. It found a significant reduction in death due to bleeding in patients randomly assigned to receive
tranexamic acid compared with placebo (1.5% vs 1.9%), especially when given within 3 hours of delivery.15 The risk of adverse
events, including thromboembolism, was not different between the two groups. Across other surgical specialties, a systematic
review and cumulative meta-analysis in 2012 looked at the effect of tranexamic acid on surgical bleeding and found that the
probability of receiving a blood transfusion was reduced by as much as a third.16 The CRASH-2 trial in 2011 assessed
tranexamic acid in trauma patients and found that early treatment with tranexamic acid (,1 hour) significantly reduced the risk
of death due to bleeding from 7.7% in the placebo group to 5.3% in the tranexamic acid group.17 However, when given after 3
hours, this effect was reduced.
SUMMARY
With such a high incidence of perioperative anaemia and reduced availability and rising costs of donor blood, blood
conservation techniques are essential to improving patient care and reducing morbidity and mortality. Strategies should begin
well in advance of the day of surgery and should include a multimodal, multiprofessional approach throughout the patient’s
perioperative journey.
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