USE OF BLOOD AND BLOOD PRODUCTS IN OBSTRETRICS
 

Principles of blood transfusion in obstetrics

• All women should have blood group and antibody screen done at booking and 28 weeks gestation
• If transfusion of any blood component is required, a sample for group & save must be sent to the blood transfusion lab
• During labour / prior to surgical intervention, blood should be sent for group & save or crossmatch according to locally agreed guideline, taking individual patient circumstances into account
• Healthy women with an uncomplicated history do not need blood grouped & saved or crossmatched prior to caesarean section
• Blood samples used to crossmatch red cells should not be more than 7 days old
• The presence of atypical antibodies can delay crossmatching and group-specific blood should not be used. Blood should be crossmatched in advance in women with atypical antibodies if bleeding is anticipated
• Only Kell negative blood should be used for transfusion unless the woman is known to be Kell positive.
• CMV negative red cells and platelets should be used in women who are CMV negative or in whom the CMV status is unknown. However, urgent transfusion should not be delayed if CMV negative blood is not immediately available
• 2 units of crossmatched blood may be permanently available for women with major placenta previa. These units should be replaced weekly by newly crossmatched units
• The use of pre-deposited autologous blood is not recommended
• Most units of blood and blood products in the UK are not virally inactivated and there remains a small risk of transfusion transmitted infection

Use and availability of blood products
 

Red cells

• There are no firm criteria for transfusing red cells. Decision should be based on a combination of estimated blood loss, continuation of blood loss, likelihood of further bleeding, symptoms, signs (P, BP) and haematological indices
• In an emergency, group-specific compatible blood can be available within 10 minutes + transport time in women with no atypical antibodies. If atypical antibodies are present, crossmatched blood is required.
• In extreme circumstances, O Rh negative red cells can be used

Fresh frozen plasma and Cryoprecipitate

• The RCOG PPH guidelines recommend that 4 units of FFP should be administered per 6 units of blood transfused.
• Other major haemorrhage protocols recommend 1:1 transfusion of red cells and FFP
• Use of cryoprecipitate should be discussed with the haematologist
• FFP and cryoprecipitate should be of the same group as the patient. If this is not possible, ABO-incompatible products may be used so long as they do not have a high titre of anti-A or anti-B activity
• Once FFP is ordered, it takes at least 30 minutes to thaw
• Anti-D immunoglobulin not needed if a Rh negative woman is given Rh positive FFP or cryoprecipitate
• Fibrinogen levels should be maintained at > 1.0 g/L

Platelets

• Platelets should be transfused when the platelet count is 75 x 109/L or less to ensure that the platelet count is maintained above 50 x 109/L
• Platelets should be transfused following discussion with the haematologist
• Platelets should be group-compatible and Rh negative women should receive Rh negative platelets
• If Rh positive platelets are administered to Rh negative women, anti-D immunoglobulin (250iu – covers 5 units of platelets given over a 6 weeks period) should be administered (not required if caesarean hysterectomy is performed)

Recombinant Factor VIIa

• May be used as treatment for life-threatening PPH
• Not recommended as prophylaxis for PPH
• Its use should not delay surgical / radiological intervention

Intra-operative cell salvage in obstetrics
 

• Intraoperative blood cell salvage is the process whereby blood shed during an operation is collected, filtered and washed to produce autologous red blood cells for transfusion to the patient.
• The aspirate includes amniotic fluid and fetal blood. A leukocyte depletion filter is recommended to reduce the amount of amniotic fluid contaminants. However, fetal blood cells are not removed.
• Although cell salvage has been used extensively in other surgical specialties, use in obstetrics has been limited by concerns about amniotic fluid embolism and haemolytic disease in future pregnancies
• Recommended for use when intra-operative blood loss of over 1500ml is anticipated
• Consent should be obtained and its use should be audited
• Should only be used by teams that use it regularly and have built up experience and expertise
• In Rh negative women, a Kleihauer test is recommended 1 hour after transfusion and the appropriate dose of anti-D immunoglobulin administered
• Can be used in women who refuse transfusion of donated blood
• May reduce the incidence of transfusion reactions and transfusion-related infection

Infusion rates and times for blood components

Depend on the individual situation and must be specified by the doctor. Use of a suitable infusion pump allows a precise rate to be specified.

Red cells

• Rapid infusion may be required in managing major haemorrhagein
• The infusion of each pack should not take more than four hours

Platelets

• Platelets have a short storage life and are generally infused in no longer than 30−60 minutes per pack.

Fresh frozen plasma

• Rapid infusion may be appropriate when it is given to replace coagulation factors during major haemorrhage. There is anecdotal evidence that acute reactions may be more common with faster rates of administration.

Complications of massive blood transfusion
 

Massive blood transfusion is defined as the replacement of a patient's total blood volume in less than 24 hours, or acute administration of more than half the patient's estimated blood volume per hour. Complications include:
 

Hypothermia

• This is a particularly important complication of massive blood transfusion and may exacerbate other complications. Hypothermia leads to reduced citrate and lactate metabolism, leading to metabolic acidosis. There is increased Hb affinity for oxygen, impaired red cell and platelet function and increased risk of cardiac dysrhythmias.
• Women being treated for post-partum haemorrhage should be kept warm and theit temperature should be monitored

Thrombocytopenia

• Due to dilution. At least 1.5 times blood volume must be replaced for this to be a clinical problem. However, can occur following smaller transfusions if DIC occurs or there is pre-existing thrombocytopenia.

Coagulation Factor Depletion

• Stored blood contains all coagulation factors except V and VIII. Only mild changes in coagulation occur as a result of blood transfusion and coagulopathy is more likely to be due to DIC.

Oxygen Affinity Changes

• Stored blood has low levels of 2,3 DPG and therefore high oxygen affinity. This adversely affects oxygen delivery to the tissues. 2,3 DPG levels rise rapidly following transfusion and normal oxygen affinity is usually restored in a few hours.

Hypocalcaemia

• Transfused blood contains ~ 3g citrate per unit (anti-coagulant, binds calcium).  The healthy adult liver will metabolise 3g citrate every 5 minutes. Transfusion at rates higher than one unit every five minutes or impaired liver function may thus lead to citrate toxicity and hypocalcaemia.

Hyperkalaemia / hypokalaemia

• Stored red cells leak potassium leading to high concentrations in the plasma. Hyperkalaemia may rarely develop if large volumes of blood are given quickly. Hypokalaemia develops more commonly as red cells begin metabolism and re-uptake of potassium

Acid/Base Disturbances

• Acid-base status may be disturbed by lactic and citric acid in stored blood. Citric acid is metabolised to bicarbonate and metabolic alkalosis may develop.

Acute Respiratory Distress Syndrome (ARDS)

• Both under- and over-transfusion are associated with ARDS.

Reducing the need for blood transfusion

• Treat anaemia in the antenatal period. Exclude haemoglobinopathy if Hb < 10.5 g/dl. Oral iron for iron deficiency and parenteral treatment if oral therapy not tolerated or compliance is in doubt. Use of recombinant human erythropoietin currently not recommended.
• Minimise blood loss at delivery. Active management of third stage of labour. Women at high risk of haemorrhage should deliver in hospital. Ensure appropriate management of women on low molecular weight heparin.

INFORMED CONSENT& REFUSAL OF BLOOD PRODUCTS

Before prescribing blood or blood products, the obstetrician should:

• Explain the proposed treatment
• Explain the anticipated benefits
• Explain the potential consequences of not being treated
• Explain the risks associated with the treatment including risk of transmitting infection
• Explain possible alternatives to the treatment (iron therapy, intra-operative cell salvage)
• Provide patient information leaflets
• Document discussion in the medical records
• Discuss with senior colleague if treatment with blood products is declined

Management of women who refuse blood transfusion

• All women should be asked if they have any objections to transfusion of blood or blood products at booking. Women who refuse blood products should be referred to a consultant obstetrician
• Women may decline treatment with blood or blood products for personal or religious reasons (for instance, Jehovah’s Witnesses)
• Women who refuse blood transfusion may accept treatment with other blood products. The woman’s wishes should be discussed in detail and documented. Women may have different views even when they belong to the same religious organisation. The individual woman’s views must therefore be taken into account
• Obstetricians must be aware of women’s beliefs in relation to receiving blood or blood products and of the alternatives to transfusion that may be applicable.
• Jehovah’s Witnesses are encouraged to carry an Advanced Treatment Directive (Living Will) detailing their wishes about medical care. Clinicians must take full note of this document. They must ensure also that the woman signs the appropriate form indicating her refusal to receive blood or blood components. The document will normally state:
• ‘In the event of emergency treatment including general anaesthesia and surgery, the administration of blood or blood components is declined. My express refusal of blood is absolute and is not to be overridden in any circumstances’.
• The administration of blood products to a patient who has refused them is unlawful and may lead to criminal and/or civil proceedings.
• Haematinics should be routinely prescribed in the antenatal period to optimise haemoglobin concentration. Anaemia should be treated promptly
• The consultant obstetrician and anaesthetist should be informed whenever a woman who has refused blood products is admitted in labour
• The third stage of labour should be managed actively and prophylactic use of uterotonic agents such as oxytocin infusion or misoprostol should be considered
• If caesarean section is needed, it should be performed by the consultant obstetrician and anaesthetist

Management of haemorrhage in women who refuse blood transfusion
 

Assessment

• Assess airway, breathing & circulation. Continuous monitoring of P, BP, SO2. Ensure accurate measurement of blood loss

Communication

• Inform the consultant obstetrician & anaesthetist. Discuss management with the consultant haematologist
• Explain that blood transfusion is recommended as appropriate
• Keep woman informed of evolving circumstances and provide opportunity for her to change her mind. Ensure that she is not acting under coercion. Recognise that a competent patient has the right to refuse treatment

Resuscitation

• Use warm colloid or crystalloid

Stop the bleeding

• Standard use of mechanical methods and uterotonic drugs.
• Have low threshold for surgical intervention including hysterectomy
• If laparotomy is performed, use cell salvage if the woman has indicated that she will accept this
• Consider iv vitamin K, desmopressin, anti-fibrinolytic agents such as aprotinin and transexamic acid.

Subsequent care
 

• Haemoglobin levels can be optimised using erythropoietin, parenteral iron and folic acid