An account of Ketamine in Bengal cats

 

Bengal cats take their name from the Asian leopard cat’s scientific name, Felis bengalensis. The breed originated through an unintended cross between an Asian leopard cat and domestic shorthairs. This happened in the late1950s during which time the Asian leopard cats were available in pet stores across some parts of America!  A woman in California was the first to make such a cross, after she got one from a pet-store as company for black tom cat. But little did she know that the two ‘species’ would mate. The result – a litter of beautiful spotted kitties, which later came to be known as the ’Bengal Cat’ after some more such crosses and back crosses.

Ketamine in some areas of the world including the Indian sub-continent is one of the most common drugs administered for cats as anesthetic along with other drugs as part of balanced anesthesia. Ketamine stands out from other anesthetics for the fact that it doesn’t significantly interfere with the cardiopulmonary homeostasis and can be given through the intramuscular route also.

There is quite a lot of anecdotal evidence of Bengal cats being extremely sensitive to the Ketamine, a commonly used Anesthetic. Muscle tremors, aggressive behavior, aversion to owners, increased vocalization, restlessness, fearfulness, erratic and dysphoric recoveries, spastic jerking movements, convulsions, hypertonicity and sensitivity to touch are few among the most common side effects of ketamine reported with the use of Ketamine. The odds of a Bengal cat experiencing one or more of the above are higher because they are ‘sensitive’ to the drug. But I couldn’t find actual scientific proof that backs up this claim. In an attempt to find some concise reference, I did however come across a couple of articles highlighting the physiological and genetic abnormalities in Bengal cats. The following points stand out

1)      Ketamine is metabolized and disposed mainly by oxidation by Cytochrome enzyme, conjugation, and small part is eliminated as such in bile and urine. Bengals are said to be deficient in Cytochrome P-450 and its isoenzymes. This compromises the cat’s abilities to metabolize several drugs like Paracetamol among many such drugs.

2)      Hypertrophic Cardiomyopathy is a cardiac disease with concentric hypertrophy of the left ventricle seen commonly in cats. Its an occult disease and very often goes unnoticed. To put this into perspective, 69% of cats diagnosed with HCM through Echocardiography didn’t exhibit cardiac murmurs and 15-35% of apparently healthy cats in a study were found to have HCM after an echocardiography and Bengal cats are one of the most presented breeds for HCM. Although mild and better compared to some other anesthetics, ketamine affects the cardiovascular properties by increasing the heart rate and arterial blood pressure- something which can have fatal effects in a cat with subclinical HCM and which is undergoing a major surgical procedure.

3)      Anecdotes state Bengal Cats are known to be extremely sensitive to Ketamine, leading to acute hypersensitivity reactions

 

Zain, a beautiful 10-month-old Bengal came in for Castration with his owner, a courteous and conversant lady who threw some light on the anesthesia of Bengal cats herself while having the pre-operative chat. Credit to her for doing all the homework, I must say. One of the very few times where Google derived information was interpreted and used in the right manner. The only other choice I had was Alphaxalone but didn’t have enough quantity of the drug unfortunately. That left me with Ketamine ultimately. I decided to use a minimal dose of Ketamine (5mg/kg), Butorphanol (0.2 mg/kg) and Xylazine (0.7 mg/kg) to attain mild sedation so that the cat can be prepped for surgery. This was clearly an empirical decision. I later planned to induce with Propofol and maintain with Isoflurane if required. The level of sedation I attained with Xylazine, Butorphanol and Ketamine was more than I expected although the physiological parameters were within acceptable limits. Induction was done using Propofol – to effect and the procedure was smoothly carried out. The lowest values of Respiratory rate, Heart rate and BP during the entire course of anesthesia were 14 breaths per minute, 60 beats per minute and 90 mm Hg respectively. I administered 4 units of Atipamezole post-surgery to be extra cautious in ensuring a quick recovery.

No visible adverse effects associated with Ketamine that were listed above were noticed. No hypersensitivities were observed. A pre-surgical echocardiogram wasn’t performed either. Zain’s recovery was smooth and uneventful and didn’t seem to be influenced by Atipamezole which although is only an alpha-2 adrenoceptor antagonist.

                     

                                           Zain while recovering from Anesthesia

This single report of using ketamine on a Bengal cat proves nothing though. Possibilities are this cat might not have had any occult heart disease and might not have had elicited any hypersensitivity reactions. After all, it is stated that Bengals are merely ‘sensitive’ to Ketamine and not ‘intolerant.’ 

I personally would still feel more comfortable using something safer like Alphaxalone and Isoflurane if I had that luxury in my practice and recommend  this low dose Ketamine, Xylazine, Propofol and Isoflurane combination in case better drugs aren't available. To conclude, I feel Bengal cats are like orchids of the plant kingdom - they need precise, personalised and diligent medical care but when given that, they never fail to impress with their looks and inquisitive personalities.