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Question Posted February 20, 2007
I'm currently managing a case involving a cat who became neurological during a rhinoscopy procedure; she woke up with seizures, was comatose and hypertensive for a day or so, then continued to improve over the last two weeks so that now she is unsteadily ambulatory, lacks a menace response but appears to avoid obstacles in her path, tries to use her litter pan and does occasionally groom herself. She responds to sounds but is still "not quite right" otherwise. She growls and hisses when petted or moved, but responds to gentle touch and will actually start purring (she never attempts any aggressive action, just noise). One of my techs was mentioning how her father had terrible headaches for a while after an episode of an aneurysm so I thought possibly she was painful and tried tramadol (a little less than a 1/4 tab, she's about 5 kgs). Her growling decreased quite a bit but it left her even more spacey and she quit eating, so I wasn't too happy with the results.
My questions - does it seem reasonable to assume she might be painful and would gabapentin be worth trying? Any other thoughts on this poor kitty?
I'm afraid if the growling and hissing keep us, her owner will give up on her but she's made tremendous recovery so far and I think she could continue to get better.
Jean Jarvis
Response 1
What an interesting case...
Of course, we have such difficulty with our patients in the realm of headache - - impossible for me to believe they don't get them, but how will we ever be able to "ask" them...
Based on what you have posted here, Jean, I would be quite inclined to try gabapentin. Most 5kg cats with pain issues in my practice start at 50mg gabapentin PO BID, and we go up from there. I have not had issues with cats being "dull" on this starting dose.
Hope you will let the list know the outcome! Good luck.
Robin Downing
Response 2
Given the history of how the neurologic symptoms onset, is there any possibility that the cribiform plate was breached during the scope procedure?
Did your biopsies reveal a neoplasia that might similarly now be crossing into the brain?
Craig D. Maloney
Response 3
That's kind of the question, isn't it? But how would you know? I didn't do the procedure, and the guy who did is ACVIM and has been doing them for twenty years. He didn't see any problems during the procedure, and the kitty was rock solid from the anesthetic end of things (we do EKG, end tidal CO2, O2 sats, blood pressure during procedures). It was on extubation that problems showed up. No malignancy in her biopsies (her nasal discharge is already under control). Anyway, I think I will try her on gabapentin, just to see what happens. She's closer to normal every day (except for the growling); today, she started to meow again.
Jean Jarvis
Response 4
I agree w/ Craig Maloney that the cat's neuro complications could possibly be related to underlying disease compromising integrity of cribriform plate, which could predispose to injury during anesthesia/rhinoscopy. MRI or CT of skull?
Regarding gabapentin dose - I knew of a geriatric cat (presumed neuropathic pain from chronic malunion lumbar fracture) who was on gabapentin 5mg/kg BID (after about 1mo on 2.5mg/kg BID) for awhile, but weeks/months later the owner/vet noticed the cat being more sedate/sleeping more, so decreased the dose. We wondered if maybe the cat's declining GFR might be prolonging gabapentin effect, so effective analgesic dose decreased.
In a cat w/ CNS problem/altered mentation, etc, esp of unknown etiology, perhaps consider starting at gabapentin dose lower than 5mg/kg BID, in order to avoid excessive CNS depression. If no problem after a day or 2 of lower dose (eg 2.5mg/kg BID), you can increase the dose in stepwise fashion as needed.
Pauline Wong
Response 5
Not an expert here, but I was wondering if ketamine had been used in the anesthetic protocol (sorry if I missed this in the original post).
The signs sound similar to some cats who have experienced an adverse event - thought to be cerebral hypoxia (even with normal readings on anesthetic monitoring) - most commonly related to ketamine use, but has been noted with other anesthetic drugs as well. If you can, search VIN on this.
Just a thought.
Response 6
Thanks for the comment. No, no ketamine on her. She went home to her owner yesterday (second try) and was hissy and growly from the car ride but then settled down and started exploring cautiously (she still can't see well but can see some). I haven't heard from the owner yet today..... hoping that's good news.
Jean Jarvis
Response 7
Bear in mind that ketamine is so commonly administered to cats in the US that although there may be an association betw ketamine & these complications in cats, by no means does that mean there is any causal relationship. If you look in the FDA CVM's adverse drug experience database, similar complications have been reported in cats treated w/ Telazol, but the numbers are less, perhaps related to ketamine being on the market for a longer period of time.
The incidence of acute blindness, deafness, & other CNS complications in previously healthy cats recovering from anesthesia may be mediated through cerebral hypoxia/ischemia during anesthesia, but the incidence is uncommon & sporadic, so it's difficult to study epidemiologically or to better establish etiology. In many cases, anesthesia was uneventful & seemingly well-conducted w/ adequate/appropriate support & monitoring.
Some cats recover. Some recover gradually, but remain blind. In the following case report, there was no significant histopath in eyes, optic nerves or optic chiasm. The cat had microscopic necrosis in cerebral cortex & hippocampus.
I. R. Jurk, et al
Acute vision loss after general anesthesia in a cat Veterinary Ophthalmology 2001; 4 (2), 155–158. doi:10.1046/j.1463-5224.2001.00170.x
Full text online (subscription or fee required):
< http://www.blackwell-synergy.com/doi/abs/10.1046/j.1463-5224.2001.00170.x >
Cat was anes w/ ketamine/acepromazine/isoflurane & intubated for dental prophylaxis. Slow anes recovery, blind, lethargic, then over 2wk had progressive deterioration.
It's encouraging that the Jean Jarvis' patient is showing signs of recovering from brain injury.
Maybe the cat is growling/hissing when handled because she's blind & not necessarily because she's painful?
Pauline Wong
Response 8
There is some evidence to support that ketamine itself is neuroprotective. I seriously doubt you can pin this particular problem on the anesthetic agent.
Himmelseher S, Durieux ME. Revising a dogma: ketamine for patients with neurological injury? Anesth Analg. 2005 Aug;101(2):524-34
We evaluated reports of randomized clinical trials in the perioperative and intensive care setting concerning ketamine's effects on the brain in patients with, or at risk for, neurological injury. We also reviewed other studies in humans on the drug's effects on the brain, and reports that examined ketamine in experimental brain injury. In the clinical setting, level II evidence indicates that ketamine does not increase intracranial pressure when used under conditions of controlled ventilation, coadministration of a gamma-aminobutyric acid (GABA) receptor agonist, and without nitrous oxide. Ketamine may thus safely be used in neurologically impaired patients. Compared with other anesthetics or sedatives, level II and III evidence indicates that hemodynamic stimulation induced by ketamine may improve cerebral perfusion; this could make the drug a preferred choice in sedative regimes after brain injury.
In the laboratory, ketamine has neuroprotective, and S(+)-ketamine additional neuroregenerative effects, even when administered after onset of a cerebral insult. However, improved outcomes were only reported in studies with brief recovery observation intervals. In developing animals, and in certain brain areas of adult rats without cerebral injury, neurotoxic effects were noted after large-dose ketamine. These were prevented by coadministration of GABA receptor agonists. IMPLICATIONS: Ketamine can be used safely in neurologically impaired patients under conditions of controlled ventilation, coadministration of a {gamma} -aminobutyric acid receptor agonist, and avoidance of nitrous oxide. Its beneficial circulatory effects and preclinical data demonstrating neuroprotection merit further animal and patient investigation.
PMID: 16037171 [PubMed - indexed for MEDLINE]
Robert E. Meyer