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Blood transfusion: how to do it

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Category: Schede
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  • Disciplina: Ematologia, Immunologia, Diagnostica di laboratorio
  • Specie: Cane e Gatto

Whole blood transfusions are indicated in all patients experiencing a rapid loss of red blood cells and plasma, as may happen as a result of trauma, surgery, rupture of organic masses, rodenticide poisoning, etc. Plasma administration is appropriate in the presence of infectious or inflammatory disorders in which a major protein loss has been detected (e.g., parvovirosis with severe diarrhoea), when supplementation of coagulation factors is necessary (e.g., in the course of rodenticide poisoning, pancreatitis, etc.) or for resuscitation procedures or other interventions.

Packed red blood cells (pRBC), or better erythrocyte concentrates, may be used in disorders characterized by a selective destruction of red blood cells, such as in the presence of immune-mediated anaemia, bone marrow aplasia, etc. (Fig. 1). Products such as concentrated plasma and cryoprecipitate may be used in the presence of severe thrombocytopenia and platelet disorders (e.g., Von Willebrand disease, haemophilia A) however such products are not always easily available.

 

 

 

EXECUTION OF THE TRANSFUSION

Ideally, before administering blood from a donor a crossmatch test should be performed in all recipients1. In reality, in the dog, the first transfusion is usually safe and allergic reactions are rare. In the cat, the situation is different. Red blood cells of cats are physiologically characterized by surface antigens, which differ depending on the blood type. In order to avoid problems of blood group incompatibility, in the cat a crossmatch test before transfusion is absolutely necessary. In the cat, even small volumes (< 5ml) of blood may at times be the cause of anaphylactic reactions, which may put at risk the life of the animal. In Italy, most cats belong to the A2 blood group, however in certain breeds such as the British shorthair, Devon Rex and Angora, blood group B cats may be present. The blood group AB is apparently very rare.2,3

Before performing a transfusion the bag containing blood or blood derivatives should be warmed to room temperature in order to avoid hypothermia and possible cardiac arrhythmias.4 Transfusion sets with special incorporated filters are used (Fig. 2) in order to trap blood clots which may form within the bag.4-7 The mixing of blood (or red blood cells) with liquid solutions, such as Ringer’s lactate or dextrose within the same transfusion line, should be avoided, as the first – in view of its concentration of ionized calcium – may cause microagglutination, while the second may cause red blood cell aggregation, swelling and lysis.

Transfusion technique
Before transfusing it is first necessary to calculate the volume of the product to be transfused.5-7 The desired PCV depends on the underlying cause. In hypovolemic patients the target PCV is usually of around 25-30%. In cases of immune mediated anaemia the target is lower, at around 20-25%, the goal being to stabilize the cardiovascular system without at the same time suppressing red blood cell production by the bone marrow.

The blood volume to be transfused may be calculated with the following formula:

Blood (ml) = 60 (cat) x recipient body weight (kg) x target PCV – recipient PCV
                     80 (dog)                                            PCV of transfused blood

The maximum transfusion volume usually allowed is of 22 ml/kg/day, although various authors use higher values without severe consequences. Higher volumes may however be the cause of hypocalcemic tetany or hypocoagulable states.

In the presence of hypoalbuminaemia, the plasma volume to be transfused may be calculated with the following formula:

Plasma (ml) = recipient body weight (kg) x 4.5 x [target albumin concentration – baseline albumin concentration (g/l)]

As previously mentioned, before transfusing blood and blood derivatives must both be warmed to room temperature. This may be done by immersion of the transfusion set, or of the entire bag, in warm water (never over 37°C to avoid blood cell lysis and plasma protein denaturation) or using appropriate blood warmers, a technique more commonly used in human medicine.

The initial administration rate should be very slow, at around 0.25 ml/kg/h for the first 15 minutes, and the patient should be monitored frequently for possible anaphylactic reactions. In the presence of a hypovolemic patient due to blood loss, the administration rate may be higher, but rarely over 22 ml/kg/h. In such cases, in order to identify eventual allergic reactions as early as possible the patient must be carefully monitored and connected to an ECG for the early detection of cardiac arrhythmias. In the presence of tremors or muscular contractions (especially after the rapid administration of large volumes of blood) a calcium assay is necessary, as hypocalcaemia may be present. In such cases, 10% calcium gluconate should be administered at the dose of 0.5-1.5 ml/kg IV over 30 minutes, while monitoring the heart rate.

Before transfusing the initial temperature, heart and respiratory rate, mucous membrane colour and CRT should be measured and transcribed. These values are to be monitored throughout the entire transfusion (e.g., initially every 15 min. then every 30 min.)

The transfusion may be continued ad the dose of 5-10 ml/kg/h; in cases in which the increased blood volume may entail risks for the animal (e.g., in the presence of decompensated heart failure, renal disease, etc.) it is advisable not to go over 4 ml/kg/h and to monitor the animal very carefully. Should all go well, without adverse events (e.g., increased respiratory rate, presence of dyspnoea, etc.), a slow increase of infusion speed may also be possible.

Plasma may be administered at the dose of 5-10 ml/kg two or three times a day, depending on the need and on the clinical symptoms of the patient.

The preferred route of administration is IV. Large gauge catheters are preferable in order to facilitate blood flow and to avoid undesired occlusions. Should the blood bag contain limited amounts of plasma (e.g., pRBC), a saline solution (NaCl 0.9%) should be added into the bag in order to make it as fluid as possible. Other types of IV fluids are not advisable as they may contain calcium or be hypo/hypertonic solutions. The administration of colloids is not recommended as incompatibility with the blood may be present as well as with the anticoagulant normally present within transfusion bags (EDTA). Many authors claim that peristaltic pumps should not be used, as they can be a potential cause of lysis of red blood cells. Although this may be a true risk, when no alternatives are available (e.g., very small animals, etc.) the author of this article uses peristaltic pumps without having ever noticed adverse reactions or side effects.

When venous access is not possible (e.g., cardiocirculatory shock patients, etc.), a large gauge catheter or a normal bone marrow aspiration catheter may be inserted into a bone marrow cavity. The possible sites of insertion are: the iliac crest, the greater tubercle of the humerus or, in neonates, the tibial crest. With this approach, red blood cells enter into the circulation within 5 minutes.

The intraperitoneal route is not recommended; with this approach red blood cells take longer to enter into the blood circulation (24-72h) and seem to have a shorter half-life.

 

TRANSFUSION COMPLICATIONS

Complications may result from improper preparation of blood and of its components, storage or administration technique. Transfusion reactions are of two major types:

  • Immune-mediated reactions
  • Non-immune-mediated reactions

Immune-mediated reactions against blood components

  • Haemolytic destruction caused by blood group incompatibility. This reaction is very similar to what happens during intravascular immune-mediated haemolysis; the patient presents haemoglobinaemia and haemoglobinuria, but extravascular reactions may also be present.

The clinical manifestations of haemolysis are:

  • Restlessness
  • Urticaria and pruritus
  • Muscle tremors
  • Seizures
  • Nausea, hypersalivation, vomiting
  • Fever
  • Facial oedema (angioedema)
  • Tachypnoea
  • Tachycardia

The non-haemolytic reactions are:

  • Pruritus/urticaria
  • Anaphylaxis
  • Fever
  • Angioedema
  • Seizures

Delayed immunological reactions:

  • Delayed haemolysis (2-21 days after transfusion)
  • Post-transfusion purpura caused by anti-platelet antibodies

Non-immune-mediated reactions

  1. Increased blood volume/very rapid administration

    1. Cough

    2. Dyspnoea

    3. Vomiting

    4. Urticaria

  2. Fever

  3. Non-immune-mediated haemolysis

    1. Damage of red blood cells during administration

    2. Use of frozen blood

    3. Use of blood which is too warm

    4. pRBC mixed with non-isotonic solutions

 

TREATMENT OF TRANSFUSION REACTIONS

In the presence of transfusion reactions:

  1. Stop the transfusion immediately.

  2. If the patient is in a state of anaphylaxis or shock:

    1. Assure that the airways are “patent” and that the patient may breathe

    2. Start infusing crystalloids at shock doses (60-90 ml/kg/h) in boluses of 20 ml/kg and monitor the patient between each bolus

    3. Administer intravenous epinephrine 1:10,000 (prepare diluting 1.0 ml of epinephrine 1:1,000 (1.0 mg/ml) in 9 ml of Nacl 0.9%). In the absence of a venous access administer the dose sublingually or into the trachea via an endotracheal tube using a urinary catheter. Repeat if necessary.

  3. Administer antihistamines: diphenhydramine 0,5-2 mg/kg (maximum 50 mg) IM q8h

  4. Verify the transfusion dose and administration speed; if the speed was very high and the clinical signs are mild, slow down the infusion rate.

  5.  In case of angioedema, pruritus or urticaria, administer antihistamines and slow down the infusion rate. Should the signs persist or worsen, stop the transfusion.

  6. In case of hyperthermia, which does not resolve with fluid therapy alone, administer very low-dose dexamethasone or an anti-inflammatory drug (meloxicam, carprofen, etc.), depending on the underlying disorder and concurrent treatments.

  7. In the presence of seizures which do not stop, administer diazepam 0,5mg/kg IV or endorectal.

  8. If sepsis is suspected, take a blood sample for culture examination and administer broad-spectrum antibiotics.

  9. Diarrhoea is sometimes present, but it is usually self-limiting and no targeted treatment is necessary.

In conclusion, blood transfusions are a simple clinical intervention, however it is absolutely necessary to be extremely cautious and to adhere to all the principles and precautions necessary for the correct blood withdrawal and infusion; it is especially necessary to carefully monitor the patient throughout the transfusion procedure, in order to identify and treat as soon as possible any adverse reaction that may arise.

 

Suggested reading

  1. Hohenhaus AE. Importance of blood groups and blood group antibodies in companion animals. Transfus Med Rev. 2004 Apr;18(2):117-26. Review.
  2. Proverbio D. et al. Comparison of gel column agglutination with monoclonal antibodies and card agglutination methods for assessing the feline AB group system and a frequency study of feline blood types in northern Italy. Vet Clin Pathol. 2011.
  3. Seth M, Jackson KV, Giger U. Comparison of five blood-typing methods for the feline AB blood group system. Am J Vet Res. 2011 Feb;72(2):203-9.
  4. Schultz JA, Sims C, Bissonnette B. Methods for warming intravenous fluid in small volumes. Can J Anaesth. 1998;45:1110-5.
  5. Tocci LJ. Transfusion medicine in small animal practice. Vet Clin North Am Small Anim Pract. 2010;40:485-94. Review.
  6. Rozanski E, de Laforcade AM. Transfusion medicine in veterinary emergency and critical care medicine. Clin Tech Small Anim Pract. 2004;19:83-7. Review.
  7. Lanevschi A, Wardrop KJ. Principles of transfusion medicine in small animals. Can Vet J. 2001 Jun;42(6):447-54. Review.