Chapter 12
Recipient Monitoring
Kenichiro Yagi1 and Marie K. Holowaychuk2
1Adobe Animal Hospital, Los Altos, California, USA
2Critical Care Vet Consulting, Calgary, Alberta, Canada
Introduction
Safe and effective transfusion administration requires donor screening, proper selection of blood products, pre-transfusion compatibility testing, recipient monitoring, and swift treatment of complications. Appropriate donor screening minimizes the chances of blood-borne pathogen transmission and prevents transfusion of anti-erythrocyte antibodies. Choosing component therapy can minimize transfusion of immunogenic components, alleviate concerns of transfusion-associated circulatory overload (TACO), and lessen apprehensions regarding storage lesions when red blood cell (RBC) products are not needed. However, some situations, such as massive hemorrhage, are more effectively managed with whole blood transfusions.
Pre-transfusion compatibility testing ensures the best possible match between donors and recipients, thereby reducing the risk of immunologic transfusion complications. Despite the best efforts to prevent transfusion-associated complications, the fact remains that not all complications are preventable, therefore careful recipient monitoring is imperative for early detection of transfusion-associated complications, as well as timely intervention. The type and incidence of complications are variable depending on the component transfused and can be categorized as immunologic or non-immunologic. Recognition of clinical signs of complications while monitoring patients receiving a transfusion is of the utmost importance.
Approach to transfusion monitoring
The general approach to monitoring recipients during transfusions starts with obtaining baseline vital signs prior to starting the transfusion. The temperature, heart rate (HR), pulse rate and quality, respiratory rate (RR) and character, mucous membrane color, capillary refill time (CRT), mentation, blood pressure, and any pre-existing edema, vomiting, or diarrhea should be recorded. The same parameters are monitored periodically during the transfusion to recognize changes that will help to determine whether a transfusion-associated complication is occurring. The pre-transfusion packed cell volume (PCV) and plasma characteristics should also be recorded for later comparison. Storage of the centrifuged microhematocrit tube will also allow for qualitative (visual) comparison of the plasma post transfusion. Blood lactate levels can also be measured to evaluate the degree of tissue hypoxia present in the case of anemia or hypovolemia.
Variations in administration and monitoring protocols exist among institutions and hospitals, although most protocols involve more frequent monitoring and a slower infusion rate during the initial phase of the transfusion; this prevents a large volume of incompatible blood from being transfused. One strategy is to initiate the transfusion at 50% of the target rate for 30 minutes, then increase to 75% of the target rate for an additional 15 minutes, and finally increase to the final target rate if no signs of complications are seen. Parameters are monitored every 15 minutes for the first 60–90 minutes and then every 30 minutes until the transfusion is completed (Prittie 2012). Another protocol initiates transfusions at a rate of 0.5–1.0 mL/kg/hour for the first 15 minutes before increasing to the final target rate if no complications are detected. Parameters are monitored every 15 minutes for the first 60 minutes and then every 30–60 minutes until the transfusion is completed (Davidow 2013).
The slower initial transfusion rate allows the recipient to be assessed for acute immunologic complications that might arise, while minimizing the volume of the blood component transfused. Therefore, if clinical signs of a complication manifest and the transfusion must be stopped, the antigenic load is reduced. As the transfusion progresses beyond the initial stage, the frequency of recording parameters is reduced as the chances of acute reactions become less likely. Ideally, all transfusion recipients should have a dedicated veterinary technician monitoring them during the entire transfusion and recording all findings on a designated form (Figure 12.1). Any unusual signs or changes in behavior should not be discounted and must be recorded. All concerns should be brought to the attention of a veterinarian immediately.
Figure 12.1 A blood transfusion monitoring form is a useful tool for record keeping and tracking the patient’s vital signs during the transfusion.
Transfusion recipients should be monitored beyond the completion of the transfusion to assess the effectiveness of the transfusion and detect any signs of delayed transfusion-associated complications. The effectiveness of RBC transfusions is ascertained when alleviation of signs related to inadequate oxygen-carrying capacity such as weakness, tachycardia, increased RR or effort, and pale mucous membrane color is observed. Blood should also be collected and hematocrit tubes spun 1, 12, and 24 hours after completion of the transfusion to assess the color of the plasma and record any change in PCV. Microhematocrit tubes spun during each PCV measurement should be stored to allow for comparison of plasma color and allow detection of extravascular (bilirubinemia) or intravascular (hemoglobinemia) hemolysis. If blood lactate was increased prior to the transfusion, post-transfusion decreases in blood lactate can indicate improvement in oxygen-carrying capacity and/or oxygen delivery. If plasma products are given for coagulation factor supplementation in patients with a coagulopathy, clotting times might be re-measured to assess the effect.
Depending on the type of complication, signs can arise within hours to weeks of the transfusion, making follow-up important. Signs of transfusion-associated complications include changes in vital parameters, blood pressure, laboratory values, or other abnormal clinical sigs (e.g., vomiting, tremors) and differ depending on the type of complications that arise (see Chapter 11). If any signs arise that are indicative of a transfusion-associated complication, the transfusion should be stopped, the veterinarian notified, and appropriate action taken.
Approach to transfusion-associated complications
Signs of transfusion-associated complications
Signs that arise during and several hours after the completion of transfusions should be treated as though they are complications related to the transfusion and responded to swiftly. Fever and vomiting are common signs of transfusion-associated complications, but can also be seen due to underlying disease. It can therefore be difficult to immediately determine the type and severity of the complication based on the initial signs seen. There are several other signs that can be exhibited by patients secondary to transfusion-associated complications or transfusion reactions, necessitating close monitoring of several parameters (Box 12.1).
Incidence of transfusion-associated complications
Transfusion-associated complications appear to be more common in dogs than cats when proper donor selection, compatibility testing, and blood transfusion techniques are employed. Transfusion-associated complications occur in 3.3–28% of canine patients and 1.2–8.7% of feline patients (Kerl and Hohenhaus 1993; Callan et al. 1996; Castellanos and Gray 2004; Weingart et al. 2004; Klaser et al. 2005; Holowaychuk et al. 2014). A retrospective study that included records of dogs receiving massive transfusions reported transient fever, vomiting, facial swelling, and delayed hemolysis in 40% (6 of 15) of the dogs (Jutkowitz et al. 2002). Another study that evaluated the effect of premedication on transfusion reactions in dogs reported signs of acute reactions within 24 hours of transfusion associated with 15% of the transfusions performed. The most common signs were fever (53%) and vomiting (18%), which occurred more often in dogs with immune-mediated diseases (Bruce et al. 2015).
A retrospective feline study observed acute transfusion reactions associated with whole blood (WB) or packed RBC (PRBC) transfusions in 8.7% (11/126) of cats. Signs included febrile non-hemolytic transfusion reaction (FNHTR) (5 cats), facial rubbing and angioedema (2 cats), vomiting (1 cat), salivation (1 cat), and pulmonary crackles that were confirmed with radiography to be pulmonary edema from volume overload (1 cat). A hemolytic reaction was also suspected in one cat (Klaser et al. 2005). A similar study retrospectively evaluated cats receiving whole blood transfusions and documented transfusion complications associated with 1.2% of the transfusions. One cat developed a fever within 5 minutes of the second transfusion and another experienced tachypnea with a mild increase in body temperature (Weingart et al. 2004).
Monitoring parameters
Transfusion-associated complications manifest in a variety of ways and are often identified by a combination of clinical signs (Table 12.1). While the type of complication cannot be determined by evaluating any single parameter, abnormal physical findings will prompt performing additional diagnostic tests to fully determine the type of the complication (Tables 12.2 and 12.3).
Table 12.1 Transfusion-associated complications and clinical signs
| Complication | Signs | Onset time | Pathophysiology | Products of concern |
| Allergic reaction: mild | Vomiting, diarrhea, fever, erythema, urticarial, pruritus, facial angioedema | Seconds to hours | IgE-mediated mast cell degranulation and release of inflammatory mediators | All |
| Allergic reaction: anaphylaxis | Dogs: weakness, collapse, generalized erythema, pale mucous membranes, prolonged CRT, poor pulse quality, hypothermia, altered mentation Cats: respiratory distress, salivation, vomiting, collapse | Seconds to hours | Massive IgE-mediated mast cell degranulation Non-immune anaphylaxis possible with high antigen load | All, especially during repeat transfusions |
| Hemolytic transfusion reactions: acute | Hypotension, bradycardia, shock Salivation, vomiting, diarrhea, fever Hemoglobinemia, hemoglobinuria (intravascular) Bilirubinemia, bilirubinuria (extravascular) | Seconds to hours | IgG- and IgM-mediated complement activation and phagocytic removal by mononuclear phagocytic system | Whole blood Packed red blood cells |
| Type III hypersensitivity | Fever, erythema, edema, urticarial, neutropenia | 1–3 weeks post-transfusion | High antigenic load, leading to immune complex formation and deposition | Protein concentrates |
| Febrile non-hemolytic transfusion reaction | Fever, with a temperature increase greater than 1°C | Seconds to hours | Immune response to leukocyte and platelet antigens | All |
| Transfusion-related acute lung injury (TRALI) | Tachypnea, dyspnea Pulmonary edema without signs of cardiovascular overload | During transfusion up to 72 hours after | Endothelial activation and expression of adhesion molecules and subsequent neutrophil activation | All |
| Transfusion-associated circulatory overload (TACO) | Respiratory distress, coughing, cyanosis, hypertension, harsh/loud lung sounds, crackles | During transfusion | Intravascular volume overload | All |
| Transfusion-transmitted bacterial infections | Variable: severe fever (>2°C increase), signs of sepsis | Beginning, during, or after transfusion | Bacterial contamination of blood product | All |
| Hypothermia | Decreased temperature measurement | Throughout the transfusion | Rapid infusion or large volume transfusion | Stored whole blood, packed red blood cells, and plasma |
| Citrate toxicity | Twitching, seizures, arrhythmias, weakness, ataxia, coma | During and after transfusion | Chelation of calcium and magnesium by citrate contained in the anticoagulant | All products containing citrate anticoagulant |
| Hyperammonemia | Altered mentation, seizures, ataxia, head pressing | During and after the transfusion | Infusion of ammonia accumulated during storage to patients with liver dysfunction | Stored whole blood or packed red blood cells |
CRT, capillary refill time; Ig, immunoglobulin.
Table 12.2 Normal and abnormal monitoring parameters for dogs and cats
| Parameter | Normal signs | Abnormal signs |
| Temperature | 100.5–102.5°F (38.1–39.2°C) | Hypothermia: <99.5°F (37.5°C) Hyperthermia: >102.5°F (39.2°C) FNHTR: increase of over 2°F (1°C) |
| Heart rate | Dog: 60–120 beats/minute Cat: 140–180 beats/minute | Bradycardia: <60 beats/minute (dog), <140 beats/minute (cat) Tachycardia: >120 beats/minute (dog), >180 beats/minute (cat) Arrhythmia |
| Pulse rate and quality | Synchronous with heart rate and clearly palpable | Asynchronous Weak |
| Respiratory rate | Dog: 10–30 breaths/minute Cat: 20–40 breaths/minute | Tachypnea: >40 breaths/minute Dyspnea: Increase in effort |
| Mucous membrane color | Pink | Pale Red Cyanosis |
| Capillary refill time | 1–2 seconds | Vasodilation: <1 second Vasoconstriction: >2 seconds |
| Mentation | Alert | Obtunded, stuporous, or comatose Neurologic signs |
| Blood pressure | Systolic: 110–160 mmHg Diastolic: 60–90 mmHg Mean: 85–120 mmHg | Hypertension: systolic >180 mmHg, mean >120 mmHg Hypotension: systolic < 90 mmHg, mean < 70 mmHg |
| Other signs | Peripheral edema Urticaria Vomiting Diarrhea Neurologic signs Weakness or collapse Restlessness Twitching Tremors Seizures |
FNHTR, febrile non-hemolytic transfusion reaction.
Table 12.3 Possible transfusion-associated complications according to clinical signs
| Clinical sign | Possible complication |
| Vomiting | Allergic reaction Anaphylaxis Hemolytic transfusion reaction FNHTR |
| Fever | Allergic reaction Anaphylaxis Hemolytic transfusion reaction Type III hypersensitivity FNHTR Sepsis |
| Hypotension | Hemolytic transfusion reaction Anaphylaxis Sepsis |
| Tachycardia | Hemolytic transfusion reaction Allergic reaction Anaphylaxis Non-immunologic hemolysis Sepsis TACO |
| Bradycardia | Hyperkalemia TACO |
| Arrhythmia | Hyperkalemia Citrate toxicity |
| Mucous membrane color | Pale: hemolytic transfusion reaction, anaphylaxis, sepsis Injected (dark red): anaphylaxis, sepsis Cyanotic or grey: TACO, TRALI, anaphylaxis (cats) |
| Capillary refill time | Prolonged: hemolytic transfusion reaction, allergic reaction, anaphylaxis, non-immunologic hemolysis, sepsis Shortened: allergic reaction, anaphylaxis, sepsis |
| Venous distension | TACO |
| Dyspnea/tachypnea | TACO TRALI Anaphylaxis (cats) |
| Neurologic/neuromuscular signs | Citrate toxicity Hyperammonemia |
| Urticaria/edema | Allergic reaction |
| Hemoglobinemia/hemoglobinuria | Hemolytic transfusion reaction Inappropriate RBC product handling, administration, or contamination |
FNHTR, febrile non-hemolytic transfusion reaction; TACO, transfusion-associated circulatory overload; TRALI, transfusion-related acute lung injury.
Temperature
Hyperthermia
Fever is the most common manifestation of a transfusion-associated complication and likely occurs secondary to the inflammatory response associated with immunologic and non-immunologic complications. Fever can be seen with transfusion-associated complications such as FNHTRs, acute hemolytic transfusion reactions (AHTRs), allergic reactions, non-immunologic hemolysis, and bacterial contamination causing sepsis. In people, the likelihood that a fever is caused by bacterial contamination is higher when increases in temperature exceed 2°C (Klein et al. 1997). However, any increase in rectal temperature of more than 1°C is consistent with a transfusion-associated complication. It is important to note that low rectal temperature measurements can be obtained pre-transfusion due to severe hypoperfusion and vasoconstriction, so an increase in temperature measurement during transfusion can be the result of clinical improvement and not a transfusion reaction. Thus, detecting a true fever in a patient initially hypothermic during baseline evaluation requires careful inspection for any accompanying signs. In patients administered protein concentrates, signs of type III hypersensitivity reactions including fever can manifest 1–3 weeks post transfusion (Tizard 2013).
Hypothermia
Hypothermia is easily detected using standard monitoring protocols and can cause deleterious effects such as increases in hemoglobin’s affinity for oxygen, changes in metabolic rate, and inhibition of coagulation. Because blood products are stored at temperatures lower than body temperature, there is a risk of causing recipient hypothermia if the blood products are not warmed prior to administration. This typically is not a problem in larger patients transfused using slower administration rates, since the product will often have the chance to warm to room temperature by the time it is transfused and because larger patients are more resistant to hypothermia. However, this becomes a concern when large volumes of non-warmed blood are transfused or high administration rates are used, especially in smaller patients. If hypothermia is detected, the patient should be warmed to normal or near-normal temperatures using external warming devices (Figure 12.2).
Figure 12.2 A patient is warmed with a forced warm air blanket.
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