Oncologic emergencies (Proceedings)

THE SEPTIC NEUTROPENIC PATIENT:

This is the most common reason for presentation to the emergency clinic in patients currently undergoing chemotherapy. Any chem

otherapy patient that is not feeling well should have a CBC performed, as well as a thorough physical examination. Severely neutropenic patients may not have enough leukocytes to mount a febrile response. Chemotherapy- induced neutropenia generally happens 7-10 days after administration although the range can extend from 4-16 days. Chemotherapy induced death of in intestinal crypt cells occurs on day 2-5 resulting in potentially higher numbers of enteric bacteria crossing the intestinal epithelium. Neutrophil numbers may not be sufficient to clear infection and multiple organs can quickly become involved. Neutrophil numbers <1,000/ul leave them at increased risk, and numbers <500/ul are almost a guarantee.

Baseline evaluation should include physical examination, CBC, biochemical profile, urinalysis and possibly blood and urine cultures and thoracic radiographs. These cases when treated aggressively have a good prognosis. Without treatment their prognosis is very guarded. They should be hospitalized and receive intravenous fluids and antibiotics.

It is important to rehydrate these patients quickly. Intravenous fluids alone will often start to bring the temperature down and make them feel much better. This will also help protect the kidneys from any potential nephrotoxicity secondary to cephalosporin or aminoglycoside administration by ensuring they are well hydrated. Cultures most often return a diagnosis of strep, staph, or a variety of gr- enteric bacteria. A first generation cephalosporin and an aminoglycoside will effectively treat over 95% of these patients. When treated effectively their temperature should start approaching normal by 8-12 hours after instituting therapy. We generally recommend taking their temperature every 1-2 hours in the initial phases of treatment. Their hydration status, blood glucose, electrolytes and blood pressure should also be evaluated multiple times each day. Patients receiving aminoglycoside antibiotics should also have urine sediments examined daily.

In patients with underlying renal disease, a second generation cephalosporin along with a fluoroquinolone can be considered. These patients may take longer for their body temperatures to return to normal. Approximately 5% of cases have anaerobes involved in their etiology and the addition of metronidazole would be required. The benefit of G-CSF is well documented in the prophylactic setting. It is more controversial in the febrile patient, but there is little drawback to adding it to the treatment regimen. Once the patient has been afebrile for a full 24 hours, and their neutrophil count is >1,000/ul they can return home on oral antibiotics which should be administered for another 5-7 days.

HYPERCALCEMIA

The most common cause of hypercalcemia in the dog and cat is laboratory error, so always be certain to recheck elevated values in the asymptomatic patient. The clinical signs can be quite dramatic and include polydipsia, polyuria, anorexia, vomiting, weakness, constipation and bradycardia. A true hypercalcemia is most often associated with an underlying malignancy. The other differentials that must be considered include primary hyperparathyroidism (parathyroid adenoma or hyperplasia), rodenticide toxicity, hypervitaminosis D, renal failure, hypoadrenocorticism, and granulomatous disease. The most common malignancies associated with hypercalcemia are lymphoma and apocrine gland anal sac adenocarcinoma (AGASACA). It has also been identified secondary to thyroid carcinoma, multiple myeloma, squamous cell carcinoma, mammary gland tumors and bony metastases from any tumor.

The data base for these patients should include a physical examination (including rectal palpation), CBC, biochemical profile, urinalysis +/- thoracic and abdominal radiographs and abdominal ultrasound. Calcium values >14 mg/dL are an indication for treatment, at 16-18 mg/dL they are considered critical patients and those >18 mg/dL are at risk for a crisis.

The goal of therapy is to increase renal excretion and decrease absorption of calcium, without compromising your ability to diagnose the primary etiology. The mainstay of treatment is intravenous fluid administration. Normal saline is the treatment of choice as it will maximize calciuresis. Fluid rates 2-3 times maintenance may be required to keep up with their losses and rehydrate the patient adequately. Other treatment options include furosemide, bisphosphonates, calcitonin and prednisone. Try not to use the prednisone until all diagnostic samples are collected so that a lymphoma is not masked. The best treatment by far is to diagnose the primary etiology and treat it appropriately.

STERILE HEMORRHAGIC CYSTITIS

This can by induced by the administration of cyclophosphamide and the incidence is higher when the cyclophosphamide is given intravenously. It can be severe enough to warrant transfusion and is very uncomfortable for the animal. The cyclophosphamide should immediately be discontinued. A urinalysis should be performed to rule out a urinary tract infection. The owners should be cautioned that these clinical signs will persist for several weeks. Pain control should be instituted immediately.

HEMOABDOMEN

Two-thirds of splenic masses are malignant, and two-thirds of those are hemangiosarcoma. The incidence of hemangiosarcoma is higher in those animals with a spontaneous rupture of their mass. It is nice to have an abdominal ultrasound prior to surgery to look for hepatic involvement and document that the spleen is the source of hemorrhage prior to surgery. Thoracic radiographs should be performed to look for thoracic metastases. Many of these animals are in a low-grade DIC at the time of presentation and most will require blood products and/or fresh whole blood. If only the spleen is involved these patients can be expected to quickly return to a good quality of life, but with median survival times of 30-90 days. The addition of adjuvant chemotherapy appears to extend survival times out to the 6-8 month range.

EXTRAVASATION

Antineoplastic agents that are vesicants or local irritants include doxorubicin, vincristine, actinomycin D, dacarbazine, mithramycin, streptozotocin, vinblastine, mustargen, daunorubicin and etoposide along with several others. The doxorubicin and vincristine are by far the most commonly administered agents and may present to the emergency clinic for swelling and redness at the site of an injection. Most of the time it is secondary to cellulitis in the region, but an extravasation should be on the list of differentials. Extravasations will quickly progress to ulcerations without appropriate therapy. Doxorubicin extravasation can be successfully managed with dexrazoxane which is administered both locally and systemically. Doxorubicin sites should be treated with cold compresses for at least 45 minutes 4-6 times within the first 24 hours. Vincristine sites should be treated with warm compresses as both cold and corticosteroids will worsen their toxicity. Hyaluronidase is the recommended antidote for vincristine extravasation and is instilled into the injection site.