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Tumescent Local Anesthesia in Cats Undergoing Mastectomy

Maria Angeles Jimenez, DVM, CVA, DECVAA, MRCVS, North Downs Specialist Referrals, Bletchingley, Surrey, United Kingdom

Anesthesiology & Pain Management

November/December 2021

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In the Literature

Moreira CMR, Oliveira RLS, Costa GA, Corgozinho KB, Luna SPL, Souza HJM. Evaluation of tumescent local anesthesia in cats undergoing unilateral mastectomy. Vet Anaesth Analg. 2021;48(1):134-141.


Tumescent local anesthesia (TLA), a novel analgesia technique, was evaluated in 12 cats undergoing unilateral mastectomy in this prospective clinical trial.

TLA containing lidocaine diluted to 0.32% and epinephrine was administered subcutaneously throughout the surgical dissection area 15 minutes after anesthetic induction. To determine plasma lidocaine levels, blood samples were collected at designated timepoints from 10 minutes to 6 hours after TLA administration. All cats remained stable during anesthesia, and none required rescue analgesia during surgery. Cats were monitored for 6 hours postoperatively and assessed for signs of toxicosis, sedation, and pain. Two cats required rescue analgesia 2 hours postoperatively. No signs of lidocaine toxicosis were observed. In all cats, lidocaine plasma levels were lower than previously identified toxic plasma lidocaine levels in cats. 

Although the authors attributed the lack of sympathetic changes during surgery to TLA and concluded that TLA is a viable addition to analgesia in cats undergoing mastectomy, isoflurane concentration was not measured. High concentrations of isoflurane could have similarly depressed the sympathetic system. In addition, TLA can have variable effects depending on the amount of subcutaneous fat; as was shown in a study in which TLA failed in one obese dog, likely due to uneven subcutaneous distribution or lidocaine deposition in fat layers.

There are no other published studies of TLA in cats and only 2 studies in dogs.1,2 Although the results of this study may seem promising, additional research is needed to confirm these findings, and it may be safer to wait for further evidence before TLA is used in clinical practice.


Key pearls to put into practice:


Appropriate patient selection is necessary when considering TLA use in cats. Until more data are available, TLA should only be considered in cases in which there are no other analgesic alternatives (eg, due to opioid hypersensitivity), and pet owners should understand the risks and lack of data. 

TLA should only be considered in cats with normal body condition, as underweight patients are prone to hypothermia and intraperitoneal injection, and obese patients may experience infiltration of local anesthetic into fat tissue.


In patients with mammary tumors, TLA has the risk for seeding cancerous cells in adjacent tissue. It is unknown whether TLA confers a risk for iatrogenic tumor implantation, but the possibility should be considered.


Absence of clinical signs of toxicosis and low lidocaine plasma levels in this study may suggest that TLA is safe in cats; however, minimum lidocaine toxicity levels in cats are still uncertain, and this study only observed patients for 6 hours postoperatively. Cats should be hospitalized overnight and adequately monitored during and after the procedure for lidocaine adverse effects and adequate anesthesia and analgesia recovery.


Pain should be scored throughout hospitalization, as lidocaine’s duration of effect is unknown. Mastectomies can be moderately to severely painful, and an analgesic should be sent home with the patient.


For global readers, a calculator to convert laboratory values, dosages, and other measurements to SI units can be found here.

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