Medical emergencies in the companion animal oncology patient (Proceedings)

It is the rapidly dividing nature of cancer cells that allows us to have success with chemotherapy protocols, and this same behavior can also lead to a crisis situation. With a critical eye and careful monitoring, most circumstances can be managed or possibly avoided altogether. The following is an overview of potential oncologic emergencies, but is by no means meant to be an exhaustive list. Lecture will include discussion of underlying pathophysiololgic states of syndromes, treatments and dosages of frequently used medications.

Patients can present with a multitude of symptoms, with most any organ and body system affected. The application of multi-agent chemotherapy protocols has allowed for survival times that are generally lengthy and of good quality. However, as no two patients will respond alike, emergencies can occur.

Acute Tumor Lysis Syndrome is a potentially fatal complication of treatment, whether it be chemotherapy, radiation or steroids, alone. Breakdown products from dying cancer cells cause metabolic imbalances such as, but not limited to, hyperkalemia, hyperphosphatemia, hypocalcemia, and resulting acute renal failure. As potassium and phosphates are largely intracellular ions, large amounts of tumor cell death results in an increase in their blood levels. Hyperphosphatemia causes acute renal failure due to calcium phosphate crystals being deposited in the renal parenchyma as a direct result of the hypocalcemia causing a calcium phosphate precipitate.

Acute Respiratory Distress Syndrome (ARDS) is a critical lung disease typified by severe inflammation of the lung parenchyma. Systemic release of cytokines and other inflammatory mediators quickly result in the need for assisted ventilation. Multiple organ failure may follow and these patients may rapidly deteriorate even with swift intervention.

Anaphylaxis is most commonly associated with the administration of L-asparaginase, but this form of hypersensitivity can be seen with the administration of any medication. Reactions usually present anywhere from an immediate onset up to 60 minutes and can include vomiting, diarrhea, edema, urticaria, dyspnea, and restlessness.

The use of chemotherapeutics alone or in concert with other treatment modalities may decrease a patient's total number of white blood cells, or more specifically, their neutrophils. Care must be taken with any immunosuppressed patient to not compromise their condition and risk inviting sepsis.

Primary tumors of bone can weaken the affected area and cause a fracture. Metastasis may also occur, as it can from many primary lesions, which also have the potential to weaken underlying bone and fracture. Acute and extreme pain, coupled with hyper- calcemia are just a few issues that need to be addressed in these patients.

Extravasation of a vesicant chemotherapeutic agent can cause tissue necrosis. If not immediately identified and corrective measures implemented, permanent injury may result. It is important to differentiate between these types of reactions versus inflammation caused by an irritant drug. While symptoms need to be addressed for patient comfort, there are typically no lasting or long-term effects from irritants.

Radiation reactions are dose and time dependant, as well as relative to area/cell type being treated. Individual factors will be discussed at the time of lecture.