1 Nov 2016
Kenichiro Yagi explains why the ability to recognise abnormalities during a blood transfusion – using knowledge of both the clinical signs of complications and appropriate interventions – is vital for a positive outcome.
Kenichiro Yagi
Job Title
Dog blood transfusion.
Veterinary nurses play a vital role in transfusion monitoring and assuring patient safety. This includes obtaining baseline vital parameters evaluating the cardiovascular, respiratory, gastrointestinal and nervous systems. Blood work, such as packed cell volume, and evaluation of plasma characters and lactate, also aid the process. Transfusion administration is phased into an initial, slow administration phase and full target rate phase, further improving safety.
Transfusion-associated complications are observed to be more common in dogs than in cats. Hypothermia can occur in rapid, high volume transfusions. Gastrointestinal signs, such as vomiting, nausea and diarrhoea, are also common. Cardiovascular signs can arise due to complications leading to hypotension or fluid volume overload. Respiratory signs can manifest from impaired perfusion or pulmonary oedema. Electrolyte disturbances and toxicity can lead to neuromuscular signs. Allergic reactions will manifest as external signs, such as urticaria, pruritus and facial oedema.
Transfusion monitoring includes monitoring both the administration and the patient. Swift intervention is necessary when clinical signs are seen.
Our knowledge of donor screening, blood typing and proper blood component and patient selection has vastly improved chances of successful transfusions.
Diligent monitoring of the patient during a transfusion is critical to a positive outcome because not all complications are preventable, and the incidence and type of complication varies depending on the component being transfused.
A general approach to monitoring starts by acquiring a baseline set of vital parameters. The baseline provides a reference point, making it possible to compare the patient’s status.
Parameters
Protocol
Initial phase:
Target rate phase:
Heart rate (HR), pulse rate and quality, respiratory rate (RR) and character, mucous membrane colour (MM), capillary refill time (CRT), temperature, mentation and blood pressure are included.
Any external signs, such as pre-existing oedema and incidences of vomiting or diarrhoea, are also noted. These parameters (Panel 1) are assessed frequently during the transfusion.
In the case of red blood cell (RBC) transfusions, recording the pre-transfusion packed cell volume (PCV) and plasma characteristic will allow for later comparison.
Storing the centrifuged microhaematocrit tube will allow for visual comparison of the plasma characteristic, which can be useful when haemolytic reactions are suspected.
The degree of tissue hypoxia can also be estimated by measuring blood lactate, which accumulates when anaerobic respiration is predominant – making the test valuable in assessing the effectiveness of RBC transfusions.
To minimise the detrimental effects of blood products should complications arise, transfusion protocols implement an introductory rate lower than the target rate, preventing infusion of large volumes prior to recognition of complication signs (Figure 1).
The reduced rate can be based on a percentage of the target rate, such as 25%, or a dosage, such as 0.5mL/kg/hr, carried out for the first 15 to 30 minutes while transfusion-monitoring parameters are assessed every 5 to 15 minutes.
If any complication signs are seen, the transfusion should be halted and the patient assessed for the type of complication being experienced. If no signs arise in the initial period, the transfusion rate is increased to the target rate as an acute reaction is less likely.
The entire transfusion should be completed within four hours to reduce the chances of bacterial proliferation from exposure to room temperature.
It is recommended to evaluate transfusion-monitoring parameters every 30 minutes during this phase as the chances of complications are still present; chances of complications, such as transfusion-associated circulatory overload (TACO), increase at a higher rate and further progress into the transfusion.
Transfusion recipients should be monitored beyond the completion to assess its effectiveness and because complications of delayed onset are possible. Assessing PCV and plasma characteristic will help assess RBC mass and the presence of delayed haemolysis. It is recommended to assess this 1 hour, 12 hours and 24 hours after completion.
A drop in PCV, haemoglobinaemia from intravascular haemolysis (Figure 2) and bilirubinaemia from extravascular haemolysis can be a sign of delayed haemolytic reaction.
Post-transfusion lactate values can be used to compare pre-transfusion values, with a reduction indicating improved oxygen delivery to the tissues.
In cases of plasma transfusion for factor deficiency-related coagulopathy, improvement can be assessed by measuring clotting times. Transfusion-monitoring parameters should be obtained during the course of hospitalisation periods.
Transfusion-associated complications are observed to be more common in dogs than cats, with incidents ranging from 3.3–28% in dogs and 1.2-8.7% in cats (Kerl and Hohenhaus, 1993; Callan et al, 1996; Castellanos et al, 2004; Weingart et al, 2004; Klaser et al, 2005; Holowaychuk et al, 2014).
The most common signs of complications in dogs were fever (53%) and vomiting (18%), occurring more often in dogs with immune-mediated diseases (Bruce et al, 2015).
A retrospective study in cats observed the highest incidence of febrile non-haemolytic transfusion reaction (FNHTR), with other complications also observed (Weingart et al, 2004, Klaser et al, 2005), such as:
Development of a fever is the most common sign of transfusion-associated complications, occurring due to an inflammatory response to the blood component.
A fever can be a sign of FNHTR, acute haemolytic transfusion reaction (AHTR), allergic reaction, non-immunologic haemolysis or sepsis from bacterial contamination.
An increase in rectal temperature of more than 1°C is likely due to a transfusion-associated complication. That said, the association is less reliable when monitoring patients with reduced rectal temperature from hypoxia-related vasoconstriction, as the increase in temperature could be a result of regained perfusion as vasoconstriction is alleviated.
Rapid transfusion of larger volumes of blood components can lead to hypothermia, as many of the products are stored at refrigeration or freezing temperature. Hypothermia is best avoided as it can result in haemoglobin dysfunction, metabolic derangement and coagulopathy.
Hypothermia is a concern mostly with high volume transfusions in smaller patients, or with rapid transfusion scenarios.
Warming the blood product using a fluid warmer placed within 2.5cm of the patient’s catheter can help prevent hypothermia, equilibrating to room temperature prior to reaching the patient (Chiang et al, 2011).
Vomiting can be associated with FNHTR, AHTR and allergic or anaphylactic reactions. In the case of allergic or anaphylactic reactions, nausea and diarrhoea can also be seen, accompanied by cutaneous signs (Shmuel and Cortes, 2013). Hypersalivation and diarrhoea are potential signs of AHTR or bacterial sepsis.
Linking gastrointestinal signs to transfusion-associated complications is easier when patients do not exhibit any signs prior to the transfusion, while differentiating between the disease process and transfusion complication in patients that already had signs is rather difficult.
Any vomiting during the transfusion should prompt investigation of a transfusion-associated complication.
Heart auscultation, HR, pulse rate and quality, MM, CRT, jugular venous distension and blood pressure can be used to evaluate the cardiovascular system during a transfusion.
However, associating abnormalities in these parameters to transfusion complications in patients experiencing hypovolaemia can be difficult.
Tachycardia is often present in anaemic patients from compensatory increase in cardiac output caused by reduced oxygen carrying capacity. If reduced oxygen carrying capacity is the cause of the tachycardia, the rate should normalise as the RBC transfusion takes effect.
Tachycardia that develops during a transfusion can indicate AHTR, allergic reactions, anaphylaxis, non-immunologic haemolysis or sepsis; all sources of loss of vasomotor tone and distributive shock.
An increased plasma potassium concentration from an RBC transfusion can lead to bradycardia (Lacerda et al, 2014), although it is unlikely to occur in patients with normal kidney function.
Hypocalcaemia and hypomagnesaemia, due to citrate toxicity, can induce arrhythmias, such as supraventricular tachycardia, ventricular premature contractions, ventricular tachycardia and ventricular fibrillation.
The MM is often pale to white, with a prolonged CRT in significantly anaemic patients, which should normalise to pink as RBC transfusions effectively alleviates anaemia. In patients without anaemia, the MM can become hyperaemic and red in colour from allergic or anaphylactic reactions from vasodilation.
Cyanosis is a late sign of respiratory compromise, which can be seen with TACO or transfusion-related acute lung injury (TRALI), though it might not be visible in anaemic patients as it depends on the presence of 50g/L of deoxyhaemoglobin.
Signs of volume overload include jugular venous distension, as well as increased blood pressure measurements.
Monitoring RR and character will allow for detection of TACO, TRALI and anaphylaxis that have a direct consequence to respiratory function. Tachypnoea is also seen with AHTR and non-immunologic haemolysis.
In many cases, anaemic patients with lactic acidosis will hyperventilate, with these signs being alleviated as anaemia is treated.
The mentation of the patient, if altered due to cerebral hypoxia from anaemia, should be alleviated as anaemia is treated. There can be worsening of mentation with complications leading to hypotension, such as anaphylaxis, AHTR or sepsis.
Citrate toxicity can cause neurologic signs related to hypocalcaemia, such as muscle tremors, facial rubbing, muscle cramping, agitation or seizures (Schneck et al, 2012). It is especially a concern in massive transfusions.
Seizures, coma, head pressing and ataxia can be caused by hyperammonaemia by infusion of stored RBC products, especially for those with liver dysfunction.
Urticaria, pruritus and facial oedema are common signs of allergic reactions. Nausea, vomiting and diarrhoea can also occur both acutely and in a delayed manner, thus having the parameters included in the set of regular transfusion-monitoring parameters.
A gravity drip is commonly used for canine transfusions since evidence emerged indicating RBC damage and reduced post-transfusion survival time when a syringe pump or volumetric pump is used for RBC administration (McDevitt et al, 2011).
The gravity drip method introduces uncertainty in the consistency of administration rate since patient position, patency of the catheter and the volume left in the bag can all alter the drip rate.
Therefore, monitoring the drip rate has become an intensive aspect of transfusion monitoring, requiring a dedicated veterinary nurse to monitor the drip in addition to the patient.
Drip monitoring systems can be used to simplify the process (Figure 3), using an optical sensor to detect blood drops passing through the administration set to display a calculated flow rate based on the frequency of drops detected. The device will track the total volume infused and set off an alarm when the drip rate falls out of desired range.
“Blood approved” infusion pumps are also available, but literature into their safety in use with blood has not been made available.
If any signs are seen and complication is suspected, the transfusion should be stopped immediately while the patient is further evaluated for confirmation and diagnosis.
Repeat measurements of transfusion-monitoring parameters should continue at regular intervals and blood samples collected for evaluation of the PCV and plasma.
The product inciting the signs should also be evaluated for potential contamination and haemolysis. Once initial steps are taken to care for the patient, further treatment should be given specifically to each complication.
Early recognition of any complication will increase the chances of positive outcomes.
