Oncological emergencies can be divided into two major categories – tumour related and treatment related.
Tumour-related emergencies (Table 9.1)
Tumour-related emergencies could be due to the primary effect of the tumour on the patient, e.g. a dog with a ruptured splenic mass, or the secondary effects caused by a paraneoplastic syndrome (PNS), e.g. severe hypoglycaemia secondary to an insulinoma. For a more detailed discussion of PNS and tumour-related emergencies, see Chapter 10.
| PTH, parathormone; PTHrP, parathormone-related peptide. | |||
| Problem | Cause | Tumour | Treatment |
|---|---|---|---|
| Anaemia | Blood loss | Bleeding tumour – haemoabdomen | Blood transfusion |
| Immunity mediated | Lymphoma, leukaemia | Steroids ± blood transfusion | |
| Hyperviscosity | Paraproteins | Myeloma, lymphoma | Fluids, cytoreductive chemotherapy |
| Hypercellularity | Leukaemia | Fluids, cytoreductive chemotherapy | |
| Polycythaemia | Renal carcinoma or metastasis to kidney | Fluids, phlebotomy | |
| Disseminated intravascular coagulation | Disruption to normal clotting process | Haemangiosarcoma, inflammatory carcinoma | Treat underlying tumour, plasma transfusion |
| Hypoglycaemia | Hyperinsulinaemia Insulin-like growth factor II | Insulinoma, sarcomas, hepatic neoplasia | I.v. dextrose |
| Hypercalcaemia | Increased PTH Increased PTHrP | Parathyroid tumour/hyperplasia Carcinomas, lymphomas, sarcomas | Aggressive saline diuresis; furosemide if hydrated, steroids if confirmed lymphoid origin |
| Effusions | Metastatic cancer Thoracic duct obstruction | Carcinomas, haemangiosarcomas, lymphomas, etc. | Thoracocentesis, pericardial tap, etc. treat underlying cause |
| Fever | Inflammation Infection | Lymphoma, leukaemia | Fluids, antibiotics, anti-inflammatories |
| Seizures | Primary brain tumour, hypoglycaemia, hyperviscosity | Glioma, meningioma, insulinoma, myeloma, etc. | Stabilize seizures depending on underlying cause |
| Urinary blockage | Tumour extension into urethra | Sarcoma, carcinoma | Place urinary catheter |
The goal of this section is to outline how patients with underlying neoplastic conditions may present in the emergency situation, but the reader is reminded that for each category there are many non-neoplastic conditions with similar presentations, so full evaluation and assessment of the patient are essential. Also, the reader is directed to individual chapters for more detailed discussion of each tumour type.
Anaemia
Unless the anaemia has resulted from acute blood loss it is rarely an emergency, even though it is a common sequela not only of neoplasia but also of long-term chemotherapy. The various causes of anaemia are discussed in Chapter 10.
Transfusions should be considered in oncological cases when the patient is clinical for the anaemia or when the packed cell volume (PCV) is falling rapidly. A cat with a PCV of 15 that is not weak, tachycardic or very lethargic does not need to be transfused as an emergency. However, this patient does require close monitoring as the situation could change depending on the underlying cause of the anaemia. If the same cat had a PCV <10%, then a blood transfusion is necessary because the oxygen-carrying capacity of the blood is reduced and cardiovascular collapse can occur.
Depending on the cause of anaemia a number of blood components are available for transfusion; however, whenever possible, component therapy rather than whole blood transfusions are indicated (Feldman 2000; see Table 9.2).
| HBOC, haemoglobin-based oxygen carrier. | |||
| Condition | Component of choice | 1st alternative | 2nd alternative |
|---|---|---|---|
| Blood loss anaemia (hypovolaemic) | Packed red blood cells and crystalloid or colloid fluids | HBOC | Whole blood |
| Blood loss (normovolaemic) | Packed red blood cells | HBOC | Whole blood |
| Anaemia secondary to bone marrow failure | Packed red blood cells | Whole blood | HBOC |
| Haemolytic anaemia | Packed red blood cells | HBOC | Whole blood |
| Disseminated intravascular coagulation | Fresh frozen plasma | – | – |
Dogs
The DEA blood groups in dogs are well established and currently blood typing cards are available to check the DEA1.1 antigen (the most immunogenic) before a transfusion (Giger 2000). Both the donor and recipient should be typed. The best donors are DEA1.1 negative. DEA1.1 positive blood should only be given to DEA1.1 positive recipients because of the potential of inducing anti-DEA1.1 antibodies in negative dogs transfused with positive blood (Giger et al 1995). The recent report of a new blood type antigen, Dal, identified initially in Dalmatians, may mean that screening against more than DEA1.1 will be necessary (Blais et al 2007). If multiple transfusions are to be given to a particular patient over a period of days it is necessary to crossmatch all future blood after 4 days to prevent a transfusion reaction.
Accurate records of what has been given to a patient should be recorded on their file. For any anaemic patient the best transfusion product is packed red blood cells as less ‘foreign’ protein is transfused and there is therefore a reduced likelihood of an adverse immune response to minor histocompatibility antigens. Giving the correct blood component rather than whole blood also reduces the potential for fluid overload in normovolaemic patients.
Cats
The AB blood group system is recognized and consists of three types: A, B and AB. In cats the presence of naturally occurring alloantibodies means that giving the wrong blood type to a patient can result in fatal transfusion reactions, even with a first transfusion. Ideally, a crossmatch should be done prior to any blood transfusion (Giger 2000). The typing cards commercially available can distinguish the two major blood groups recognized in cats, A and B. However, in the rare case of a suspected AB cat, the blood should be sent to an outside laboratory for typing. The prevalence of blood types varies geographically and within breeds (Giger et al 1989, Knottenbelt et al 1999).
Breeds with a high incidence of B blood type include British Shorthair (40%) and Cornish/Devon Rex (30%); breeds with no reported B blood type include Siamese and Tonkinese. Weinstein has recently reported on the presence of an additional red cell antigen, Mik (Weinstein et al 2007). In cats, blood components are not as readily available as in dogs so whole blood transfusions are usually given. Finding a B donor cat can be very difficult and in such instances haemoglobin-based oxygen carrier (HBOC) products are available (Muir & Wellman 2003).
When giving a blood transfusion, the volume to be transfused can be calculated as follows:
where k = 90 for dogs and 60 for cats.
Haemoabdomen
This is most commonly seen in dogs with ruptured splenic/liver masses. It is seen far less frequently in cats and may then be due to either haemangiosarcoma (HSA) or mast cell tumour (MCT). The clinical presentation is typically acute collapse and on examination the mucous membranes are pale and there is often a palpable fluid wave. It is important to remember that not every haemoabdomen in the dog is due to HSA and 30 to 50% of splenic masses are benign (Chapter 23). In the emergency situation it is important to confirm that the ascitic fluid is in fact blood. A blood-coloured fluid is not necessarily blood! The peripheral PCV and the PCV of the fluid should be checked and coincide before a diagnosis of haemoabdomen can be made.
Significant fluid in the abdomen means that abdominal radiographs may not be helpful so the best diagnostic tool is an abdominal ultrasound. The presence of a haemoabdomen as a result of a bleeding splenic/liver mass and a low or falling PCV necessitates an abdominal exploratory. Many of these patients are in disseminated intravascular coagulation (DIC) so a clotting profile should be obtained. If the patient is significantly anaemic or the PCV is falling, then a blood transfusion may be needed before or during surgery, and blood products should be available after surgery if bleeding continues. In patients with stable PCV >25% but in DIC, fresh frozen plasma should be given instead of whole blood.
Hyperviscosity/polycythaemia
In veterinary medicine, hyperproteinaemia is the most common cause of hyperviscosity, polycythaemia is rare and hyperviscosity as a result of significant leucocytosis is also uncommon. Patients with hyperviscosity may present with a number of clinical signs, e.g. epistaxis, hyphema, collapse, weakness or seizures. Establishment of a good minimum database is essential. In the case of hyperviscosity due to paraproteins, fluid therapy is indicated, i.e. 0.9% NaCl at high fluid rates. Polycythaemic patients will also respond to high fluid rates as an initial treatment in the emergency situation. If the PCV is extremely high (>70), phlebotomy should be used to lower the PCV to around 60. The reduction in PCV should be gradual. The amount of blood that can be removed is up to 20 ml/kg and the volume should be replaced with 0.9% NaCl. For patients with hyperviscosity due to leucocytosis, the underlying cause needs to be established; however, if it is a consequence of leukaemia, then chemotherapy needs to be implemented (see Chapter 22).
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