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Today's VeTerinary PracTice | January/February 2016 | tvpjournal.com elemenTs oF oncology Peer reviewed 54 oTm buprenorphine (80–120 mcg/kg Q 12–24 H) or transdermal fentanyl liquid (2.7 mg/kg, one application) can be used to further alleviate pain when nsaids and other analgesics do not provide enough comfort. Defnitive Chemotherapy although it is not often recognized as a side effect of chemotherapy in veterinary patients, pain is possible due to: • drug extravasation • Unique drug toxicities. Extravasation s evere tissue necrosis and pain occur when vesicant chemotherapy drugs, including doxorubicin, vincristine, and vinblastine, are administered extravascularly (Figure 5). 15 extravasation of doxorubicin results in severe tissue injury that may result in the need for surgical debridement, amputation, or euthanasia. 15,16 extravasation can be avoided by use of a perfectly placed, one-stick iV catheter and vigilant observation. 15,16 To reduce the risk of inadvertent catheter dislodgment and extravasation in dogs and cats that are too excited for catheter placement with physical restraint alone, chemical restraint—such as a neuroleptic analgesic technique combining a sedative/tranquilizer (eg, acepromazine, midazolam, dexmedetomidine) with an opioid—should be considered. once extravasation is known: • an attempt to aspirate the drug through the iV catheter and then tissue cooling to induce local vasoconstriction and prevent further spread of the drug is recommended. 16 • evidence suggests that intravenous administration of the chelating agent dexrazoxane within 6 hours of doxorubicin extravasation may reduce severity of injury, but ideal dose and timing are unknown. 16 • anecdotally, topical 99% dimethyl sulfoxide applied 3 times per day and cold compresses applied up to 4 times per day for up to 2 weeks are recommended. 15,16 • Use of the nsaid piroxicam has also been reported anecdotally, 16 and other nsaids or opioids may be indicated depending on the severity and extent of tissue injury. nsaids and opioids may also be useful to reduce the occurrence of self-trauma following extravasation events that could lead to further local tissue injury. although most recommendations for treatment of extravasation injury are anecdotal, it is prudent to manage cases of suspected or confrmed extravasation proactively, with combinations of topical dimethyl sulfoxide, cold compresses, nsaids, and opioids to reduce the risk for serious and potentially life-threatening tissue injury. Sterile Hemorrhagic Cystitis acrolein is a metabolite of cyclophosphamide that is concentrated in the urinary bladder and induces sterile hemorrhagic cystitis (s Hc), a painful and irritating condition that manifests as hematuria, pollakiuria, and stranguria without evidence of a bacterial infection. 17,18 When s Hc occurs, cyclophosphamide is often discontinued to reduce the risk for worsening clinical signs. Treatment focuses on supportive care with oral pain medications, including opioids and nsaids, as no effective specifc therapy for s Hc exists. Prevention strategies include: • co-administering furosemide at doses up to 2.2 mg/kg iV 17 Figure 5. A 7-year-old, spayed female rottweiler—previously treated for diffuse large B-cell lymphoma at another practice— presented due to relapse, with a nonhealing ulcer over the right cephalic vein. The ulcer had reportedly developed 7 months prior to presentation, following the frst administration of vincristine. The referring veterinarian's medical records indicated a change in the pet's demeanor following the extravasation event, and the patient required a basket muzzle for subsequent treatments. The ulcer persisted until the dog's death approximately 11 months after the extravasation event.