171
PATIENTS ON ANTICOAGULANTS
Check of control of anticoagulation
The therapeutic range for the INR may vary according to the indication for anticoagulation. An INR of 2.0–3.0 is usually appropriate for DVT prophy-laxis and 3.0–4.0 for patients with mechanical prosthetic heart valves.
For patients who have INR 4.0–7.0 without haemorrhage, withhold warfarin therapy for 1 or 2 days, and arrange review by appropriate specialist team or GP. For patients with INR > 7.0 without haemorrhage, withhold warfarin and obtain specialist consultation before considering phytomenadione (vitamin K 1 ) 5mg by slow IV injection or orally.
Interactions with other prescribed or proprietary medicines Many drugs can interfere with anticoagulant control. Before giving or stopping any drug in a patient taking warfarin or other anticoagulant, check the potential for interaction — Appendix I in the BNF .
Particular groups of drugs, likely to be prescribed in the ED, which may cause problems include analgesics (especially NSAIDs), antibacterials and anti-epileptics. Always LOOK IT UP.
Other oral anticoagulants
Dabigatran (a direct thrombin inhibitor) and rivaroxaban (a Factor Xa inhibitor) are among a group of new oral anticoagulants which may be prescribed instead of warfarin or low molecular weight heparin, in certain conditions. They do not require routine blood monitoring. To date, there are no guidelines for measuring their effect in patients who are bleeding, and there is no proven way to reverse their effect. Always discuss bleeding patients on new oral anticoagulants with a haematologist. Attempts at reversal may include FFP or prothrombin complex concentrate.
Blood transfusion 1
It is better to stop bleeding than to have to replace blood loss General aspects
Correctly documenting and labelling blood tubes and forms, combined with checking blood products prior to administration, is crucial for safe patient care. If a patient’s name(s), date of birth, clinical details and address are unknown or uncertain, identify them for transfusion purposes by a unique number (usually their unique ED number) and inform the blood transfusion laboratory.
To avoid confusion, the doctor taking the blood sample must label and sign the tube at the patient’s bedside, complete the form, and contact the transfusion service. Only take blood from one patient at a time. Label tubes immediately to minimize the risk of mislabelling. Blood banks may refuse to handle incorrectly labelled forms/tubes.
If you knowingly give a blood product (or animal product e.g. gelatin) to a patient whom you know would not accept this (eg a Jehovah’s Witness) you are likely to face an indefensible medicolegal claim.
What to send
10mL clotted blood is usually adequate for adults. Where it is obvious that massive transfusion may be required, send two 10mL samples. On the request form, indicate how much blood is needed, when and where the blood is to be sent. Date and sign the form.
What to request
The amount of blood to be delivered and to be kept available at the transfusion centre for immediate dispatch depends on the patient’s clinical state and assessment of future blood losses. Assessment of a patient with hypovolaemic shock is complex and includes recognition of the clinical situation, the potential blood loss, together with a current assessment of the patient and investigations. Hb and Hct values may be misleading.
It may take hours for their values to equilibrate to those indicating the degree of blood loss.
Group and screen The patient’s ABO and Rhesus D group is determined and the serum tested for unexpected red cell antibodies. Subsequently, if required, blood can be provided within 10–15min, assuming the antibody screen is clear. Request ‘Group and screen’ where a patient does not need transfusion in the ED, but may require it later.
Cross-match Full blood compatibility testing may take up to 1hr. If blood is required more urgently, ABO and Rh compatible units can usually be provided within 15min, including an ‘immediate spin cross-match’ as a fi nal check on ABO compatibility. In exsanguinating haemorrhage, uncross-matched group O Rhesus –ve blood can be issued immediately.
173
BLOOD TRANSFUSION 1
Blood products
The UK uses blood component therapy. There appears to be no specifi c advantage in using ‘whole’ blood as opposed to red cells plus a volume expander.
Red cells (additive solution) Each pack (volume 300mL) is from a single donor and has a Hct of 0.65–0.75 (0.55–0.65 for RBCs in additive solution).
A transfusion of 4mL/kg will i circulating Hb by 81g/dL.
Whole blood A ‘unit’ contains 530mL (470mL of blood from a single donor + 63mL preservative solution), with a Hct of 0.35–0.45.
Platelet concentrate either pooled or from a single donor by platelet pheresis.
Fresh frozen plasma contains clotting factors and fi brinogen.
Cryoprecipitate is derived from FFP when it is thawed. It is rich in factor VIII, fi brinogen, and von Willebrand Factor.
Prothrombin complex concentrate is a combination of vitamin K dependent Factors II, VII, IX and X. Use PCC to reverse warfarin.
Transfusion precautions (UK Blood Safety & Quality Regulations 2005)
• 2 practitioners must confi rm all the following steps before commencing transfusion. If there is ANY discrepancy, DO NOT transfuse.
• Confi rm the details on the traceability label on the blood component match the patient’s full name, date of birth, and hospital number (wrist band if unconscious).
• Check that the traceability label is attached to the blood bag.
• Ensure the donation number, the patient’s blood group/RhD type all match and that any special requirements are covered.
• Check every component before starting transfusion for signs of discol-ouration, leaks, clots etc. and the expiry date.
• If all checks are satisfactory, the 2 practitioners should ensure that the component has been prescribed (prescription form and/or fl uid balance chart) and sign the front of the traceability label before commencing the transfusion.
• Infuse all components through a giving set with integral fi lter to trap large aggregates. Microaggregate fi lters are not routinely required.
• Never add any drug to a blood component infusion.
• Do not use giving-sets which previously contained glucose or gelatin.
• Red cell concentrates may be diluted with 0.9 % saline using a Y giving-set to improve fl ow rates. Never add any other solution.
• Use a blood warmer, especially for large and/or rapid transfusions.
• Once the transfusion has started, peel off the portion of the signed label and attach to the appropriate place in the fl uid balance sheet.
• Sign the prescription form to confi rm the patient identity checks.
• Complete and sign the label and return it to the laboratory.
See: www.transfusionguidelines.org.uk
Blood transfusion 2
Massive transfusion
Loss of 50 % of circulating blood volume within 3hr is perhaps the most relevant ED defi nition. Resuscitation requires an interdisciplinary team and clear organization.
In the event of massive blood loss
• Protect the airway and give high fl ow O 2 .
• Get help — two nurses and a senior doctor.
• Insert two large bore cannulae and start IV warm saline 1000mL stat.
• Take FBC, U&E, LFTs, coagulation, and cross-match. Label the blood tubes and ensure they are sent directly to the laboratory. Do not leave them unlabelled or lying around in the resusitation room.
• Telephone the haematology laboratory to warn of potential massive transfusion. Request ABO group-specifi c red cells if the patient is peri-arrest. This will take only 10min in the laboratory. Otherwise, request full cross-match and give number of units required.
• Accurate patient ID is essential, even if the patient is unknown.
• Call appropriate senior surgeon — to stop bleeding as soon as possible.
• Start blood transfusion if the patient remains tachycardic and/or hypo-tensive despite crystalloid resuscitation.
• Repeat all bloods, including FBC, clotting, U&Es, calcium, and magne-sium levels, every hour.
• Start platelet transfusion if platelet count falls below 75 × 10 9 /L.
• Anticipate the requirement for FFP and consider giving early during the resuscitation. FFP will replace clotting factors and fi brinogen. Aim to maintain fi brinogen > 1.0g/L and the INR and APTT <1.5 normal.
Cryoprecipitate may also be used.
• Recombinant Factor VIIa might be used as a ‘last ditch attempt’ to control bleeding in young patients where surgical control of bleeding is not possible, and the above has already been corrected. If the drug is available it is usually ordered by a haematologist.
Massive transfusion complications Rapid infusion of blood products may lead to:
Hypothermia Blood products are normally stored at 2–6 ° C. Rapid infusion can cause signifi cant hypothermia. Use blood warmers routinely for rapid transfusions (eg > 50mL/kg/hr or 15mL/kg/hr in children). Never warm a blood product by putting a pack into hot water, on a radiator or any other heat source.
Electrolyte disturbances With massive transfusion, the citrate anticoagulant may cause signifi cant toxicity, d plasma Ca 2 + (impairing cardiac function) and acid–base balance disturbance. This is aggravated in patients with underlying liver disease, hypotension or hypothermia. Citrate may also bind Mg 2 + , causing arrhythmias. Prophylactic or routine administration of IV calcium salts is not recommended. Monitor ECG and measure ionized plasma Ca 2 + levels during massive transfusion. K + levels i in stored blood and hyperkalaemia may follow massive infusion. Routinely monitor the ECG and check plasma K + levels. Transient hypokalaemia may follow 24hr after large volume transfusion
175
BLOOD TRANSFUSION 2
Blood product administration
Blood transfusion is not a panacea. An improvement in O 2 delivery cannot be assumed. RBC function deteriorates during storage and changes in O 2 affi nity occur withe d 2,3-DPG levels, while d ATP levels alter RBC mem-brane deformability causing i cell stiffness and micro-circulatory problems.
UK donations are routinely screened for hepatitis B, HIV, HTLV, syphilis, and where necessary, CMV. However, blood cannot be sterilized: small but defi nite risks of infection transmission exist.
Transfusion reactions
Monitor the patient closely for the fi rst 5–10min of the infusion of each unit of blood to detect early clinical evidence of acute reactions. If the patient develops a temperature, shortness of breath, chest or abdom-inal pain or hypotension, suspect a transfusion reaction. Treat allergic reactions including itching, urticaria, bronchospasm and fever convention-ally (see b Anaphylaxis treatment, p.43).
Mismatched transfusion By far the commonest cause is a clerical error when labelling, ordering or administering blood. Transfusion of ABO incompatible blood causes acute severe haemolysis and circulatory collapse. In a hypovolaemic, shocked, or anaesthetized patient these features may be obscured and missed.
If a transfusion reaction is suspected:
ABO incompatability, haemolytic reaction, bacterial infection, severe allergic reaction, or transfusion-related acute lung injury:
• Stop the transfusion.
• Keep the IV line open with 0.9 % saline.
• Record all observations, give supplemental oxygen.
• Double-check the blood unit label with the patient’s wrist identity band and other identifi ers.
• Send the unit of blood product and the giving set to the blood bank.
• Take 40mL of blood. Send it as follows:
• 5mL anticoagulated and 5mL clotted blood to blood bank;
• 10mL for U&E;
• 10mL for coagulation screening;
• 10mL for blood cultures.
• Contact the blood bank directly by phone.
• Contact haematologist directly.
• Give broad spectrum antibiotic if infection suspected .
• Monitor fl uid balance and urinary output.