Sedation and anaesthesia
An ideal anesthetic agent for feral cats would have a wide safety margin; provide rapid and predictable surgical anesthesia and postoperative analgesia; and be reversible, inexpensive, and simple to administer to trapped cats.[x]
Feral cats are typically given an anaesthetic/sedative combination by intra-muscular injection. Ketamine causes hypertonicity of skeletal muscle so it is combined with a sedative to achieve adequate muscle relaxation.[xi]
Don’t feel that feral cats are being short-changed by not being given inhalant anaesthesia. There are some good reasons to use an injectable cocktail for feral cats:
- Safety: It is far safer to inject a feral cat through a crush cage than it is to sedate them and administer an induction agent such as Propofol or Alfaxan intravenously. Feral cats may not respond to pre-meds in same way as a tame cat and may need a higher than normal amount to achieve adequate sedation. Similarly, the need for the cat to regain all of its reflexes and come-to before extubation poses an obvious risk when dealing with a feral cat.
- Speed: The goal with TNR is to begin surgery as soon as possible once the cat has been trapped, with the aim of minimising the cat’s stress and trauma. A pre-med sedative takes twenty minutes to take effect before the cat can be inducted and intubated. In contrast, intra-muscular anaesthetics typically take effect within five minutes. Inhalant anaesthesia causes further delay after surgery while waiting for the cat to recover sufficiently for extubation. If multiple cats are being trapped and neutered on a single day, using inhalant anaesthesia is not a good use of the time allotted to the TNR group.
- Suitability: Injectables offer good anaesthesia and analgesia for thirty to forty minutes, which is sufficient time to perform a routine spay or neuter. If surgery is unexpectedly prolonged, the cat can be masked and gassed down. Approximately 11% of feral cats require supplemental anaesthesia with isoflurane.[xii]
- Some studies suggest that the use of inhalant anaesthesia actually increases the risk of anaesthetic death in cats. This should be put in perspective however; the overall rate of anaesthetic death in cats is estimated at approximately one in 895.[xiii]
Suggested anaesthetic protocol
For cats weighing less than 2kg, vets practised in feral spay/neuter recommend a combination of ketamine and medetomidine, administered concomitantly in one syringe.
|Active ingredient||Brand name||Concentration||Dosage|
|Ketamine||Narketan 10%||100mg/ml||2.5mg/kg i.m.|
Other ketamine brands include Vetalar and Narketan, but concentration may vary between products. Medetomidine is variously branded as Medator, Sedator, Sedastart etc. but again concentrations may vary. Medetomidine can be reversed with atipamezole (Antisedan™) when surgery is completed. Kittens should be given a dose of atipamezole equivalent to half the dose of medetomidine received, so that they can eat as soon as possible after surgery. This is essential to prevent hypoglycaemia.
Alternative anaesthetic protocol
Ketamine is combined with xylazine, given concomitantly in one syringe.
Other xylazine brands include Rompun 2% and Chanazine 2% but concentration may vary between products. Xylazine depresses thermo-regulation in cats, so extra precautions are needed to prevent hypothermia both during and after surgery. The cat should be protected against the cold surface of the operating table with a towel and heat pad.
The ketamine should be drawn into the syringe first, so that it is administered second to the medetomidine or xylazine. This is because it stings and if the cat jumps there is a risk of incomplete intramuscular delivery. Lubricate the eyes with Gel Tears™ (Chauvia) or Clinadry™ (Nutriscience).
Cats that achieve only partial anaesthetic effect can be masked and given inhalant anaesthesia for the remainder of the surgery. Do not mask cats with significant URI.
The cat’s bladder should be carefully expressed before preparation for surgery. If the cat cannot be provided with a hospitalisation cage and litter tray after surgery, they may be reluctant to urinate in the trap or cat carrier and experience bladder discomfort. Emptying the bladder for the cat also lessens the likelihood that you will have to disturb the recuperating cat to change out soiled bedding.
Antibiotics are unnecessary if it is a routine spay/neuter of an apparently healthy cat and asepsis is strictly maintained. Injectable antibiotics are recommended if the cat has an upper respiratory tract infection or infected bite wounds. Cats found to be pregnant should receive prophylactic long-acting antibiotics at time of surgery. For example, Betamox LA™ (amoxycillin) is a broad-spectrum antibiotic suitable for skin and soft tissue infections and is effective for up to 48 hours. It can be given subcutaneously or into the muscle at a rate of 0.1ml/kg. Convenia™ (cefovecin sodium) effectively treats infected wounds and abscesses and provides up to 14 days of treatment. Note that its safety has not been determined in lactating animals. The dosage for cats is 8 mg/kg.
Young, apparently healthy cats should receive an NSAID such as Metacam or Carprieve subcutaneously before surgery, as the analgesic effect of xylazine is very short. Pain control is important not only for humane reasons, but because pain inhibits recovery. More so than with pet cats with indoor access, these cats need to be back on their feet as quickly as possible. Use NSAIDs with caution in older cats as they may have underlying renal or hepatic impairment. Determine the safety of your chosen NSAID for use in lactating cats.
Not all TNR groups will want their cats tested for FIV and FeLV. This comes down to reasons of cost and practicality. Time and time again, scientific studies have shown that the incidence of FIV or FeLV in feral cats is not significantly greater than the rate of infection in owned cats.[xiv] If every feral cat were to be FIV/FeLV tested, the results would be negative up to 90 or 95% of the time. Where an FIV/FeLV test equates to half the cost of a spay/neuter procedure, TNR groups do have to ask themselves if such testing is the best use of limited funds.
Some groups compromise by testing those cats that have clinical signs of an infection that is usually self-limiting but can become chronic in an immuno-suppressed individual. The likelihood is however that cats with conditions such as emaciation, renal enlargement, stomatitis, severe otitis externa, pyoderma or chronic upper respiratory tract infection should be euthanised on humane grounds regardless of their FIV/FeLV status, because it is impossible to provide such cats with effective treatment.
A further complicating issue is the accuracy of ELISA test kits such as WITNESS™ or SNAP™ as they are not entirely reliable.[xv]
- Accuracy of positive tests for FIV/FeLV decreases when prevalence is low, so up to 50% of positive test results might be expected to be false positives.
- The sample may be contaminated, which can cause a false positive.
- Positive test results in kittens less than six months of age should be repeated. FIV+ mother cats transfer antibodies to their kittens during lactation. Although all the kittens may be antibody positive, the actual virus itself is usually only transmitted to one in three.
- Some FIV cats produce antibodies that are not detected by the standard in-house test, resulting in false negatives.
- In the early stages of infection, FIV antibodies are not produced, which causes a false negative.
- A cat in the later stages of FIV may also test negative because their immune system is so compromised that they no longer produce detectable levels of antibodies.
This is not to say that ELISA test kits don’t have their uses, but they are more suited for use in tame cats, who can be retested by an outside laboratory to confirm the cat’s FIV or FeLV status.
As already touched on, euthanasia should be considered for cats that have signs of illness or injury that will cause continued pain and suffering. A disease that might be successfully treated in a tame cat is often incurable if it’s a feral, because the trauma of indefinite confinement and physical restraint required to treat the cat would outweigh the benefits. Realistically, the only treatments that can be offered to a feral cat are those that can be quickly performed while the cat is still anaesthetised and that don’t require significant aftercare. For example:
- Diseased, loose teeth can be extracted
- Mutilated, necrotic tails can be amputated
- Cancerous ear tips can be removed to prevent spread of squamous cell carcinoma.
- A ruptured, infected eye globe caused by bacterial infection secondary to URI can be enucleated
- Wounds and abscesses can be clipped, flushed and cleaned with disinfectant solution
- Mite-infested ears can be flushed with one of the following preparations:
- Cooled chamomile tea
- 0.1% povidone iodine solution
- 0.5ml Hibiscrub™ and 99.5ml lukewarm water
- Distilled white vinegar and pre-sterilised tepid water diluted 1:2
Spays: Flank approach or ventral midline incision?
This will largely depend on the vet’s preference. Traditionally, the flank approach has been advocated for feral cats because the incision can be more easily monitored for wound infection, dehiscence or evisceration. But is not recommended for pregnant cats due to associated morbidity. [xvi] If the vet discovers pregnancy on entering the abdominal cavity, they should close the flank incision and use a ventral midline approach instead. The flank approach has also been recommended for lactating cats, but we have not experienced any difficulties with the ventral midline technique in nursing cats when the surgeon is skilful and keeps the incision as small as possible without compromising the quality of the surgery.
If the vet uses the flank approach, be conservative when clipping the cat in preparation for skin scrubbing. Clip conservatively so the cat suffers only minimal heat loss once released after surgery.
Increased post-operative pain has been reported in cats that have been flank spayed compared with those spayed via ventral midline incision.[xvii] For this reason the ventral midline approach is preferable. We have encountered only one incidence of evisceration, and this occurred when a panicked cat snagged the wound while recovering in the trap shortly after surgery. (This is why we now only use the better quality traps!) Wound prolapse should not be a worry so long as there is a two- or three-layer closure of the muscle, intra-dermal and outer skin layers.
Special considerations when spaying pregnant cats
Sadly, this is a necessary evil. It is hard to justify not spaying a feral cat found to be pregnant. If she is released unspayed, chances are her kittens will never be located and they will most likely suffer tremendously. Recapture of the mother cat after the kittens are weaned is extremely difficult, if not impossible. Even in the unlikely event that she is retrapped, she will probably be pregnant again already.
For the unborn kittens, it is a humane and merciful passing. The mother cat is spared the further burden of endless litters of kittens and will have a longer life-expectancy.
It is not fair to confine a feral cat for the duration of her pregnancy so that her kittens can be tamed and rehomed. For one, the stress of confinement may lead the cat to reject her kittens. Secondly, if a feral cat is separated from their colony for more than three weeks, she will have difficulty reintegrating. So a female cat who has been away from the colony from time of capture through to kittening and weaning of those kittens should be relocated. Feral cats are very attached to the territory they have established and female feral cats in particular form very close familial ties. It is hugely traumatic for a feral cat to be relocated, so relocations to farm homes are only carried out if the cats lives are in danger in their current location.
Some vets will not spay a pregnant cat if her unborn kittens are at an advanced stage of development. Others will spay a female cat in late pregnancy. Either way, a pregnant cat that is being spayed will require additional care. She should be given 10-20ml/kg sub-cutaneous fluids, which equates to 60-100mls for an average-sized cat. If she is close to full-term, a euthanising agent should be injected into the uterus once it has been removed from the cat. Pregnant cats require confinement for at least 48 hours after surgery.
Cat gut is still typically used for ligatures, but because the cat cannot be recaptured for suture removal, absorbable suture material such as PDS II, Polysorb, Dexon, Biosyn or Vicryl should be used for closure. Many vets instead use Supramid, which is non-absorbable but has low tissue reactivity.
A cruciate mattress pattern is suitable for the muscle layer. One suture usually suffices.
A simple-interrupted suture pattern is ideal for skin closure as failure of one knot will be inconsequential. The sutures can have extra knots applied or can be placed intra-dermally. At least one vet that works with us uses a vertical mattress pattern for skin closure, because it makes it more difficult for the cat to interfere with the sutures.
Surgical staples are not recommended as they are only appropriate if they will be subsequently removed. This is impractical with a feral cat.
Any cats that present with lice, fleas or ear mites should be given a spot-on application of Advocate or Stronghold before end of surgery. The use of Frontline spray as an alternative is not advisable because it may contribute to hypothermia in a recumbent cat.
Nurses may question the virtues of giving such treatments to parasitised feral cats when they typically offer protection for no longer than four weeks. But TNR clients will still be anxious that affected cats be treated, regardless of the additional cost:
- Severe infestations with fleas or cat lice can be severely debilitating. Cats and kittens that are badly infested become anaemic. Cats with chronic ear mite infestations commonly have infected wounds around the base of the ears from persistent scratching. Even a month’s relief can be enough time for secondary, bacterial infections to resolve. A neutered cat is more robust, so it should shrug off any subsequent infestations more ably.
- Treating an affected cat may prevent transmission to other, more vulnerable members of the colony, such as kittens. Bear in mind that fleas are vectors of FeLV.
- Not all ferals live communally, so the cat may not necessarily become re-infested by direct contact. Limerick Feral Cats provide shelter to the feral cats after release. The shelters are filled with hay which is changed out regularly. This minimises the presence of flea larvae and flea pupae in the cats’ environment. If a cat is reinfested with fleas after a time, they can be given an oral treatment to kill adult fleas, e.g. Capstan.™
Ear-tipping is essential to responsible feral colony management. It causes the cat no distress as it is quickly performed while the cat is still under anaesthesia. Ear-tipping eliminates the possibility that the cat will be mistaken as entire and subjected to the unnecessary trauma of recapture. It is essential for TNR groups to be able to identify newcomers to a managed colony so that they can be neutered to keep the population from increasing.
Some vets practice ear-notching instead of ear-tipping, but a small, triangular ear-notch closely resembles the tears to the ear commonly inflicted during cat fights. You also need to be very close to the cat to see the notch, and this is not practical with cats that flee from close contact with humans. The beauty of ear-tipping when performed well is that it creates a very distinctive silhouette that can be seen from a distance.
The left ear that is tipped, according to international practice. There are several techniques. In each case, about 3/8th of an inch is removed from the distal tip of the left pinna.
- A straight arterial forceps is placed across the ear and a scalpel blade or Mayo scissors is used to cut to make a sharp dissection above the forceps. The forceps remain clamped on the ear until just before the cat is placed in their carrier for recovery. This reduces bleeding. The cat should be placed in right lateral recumbency for recovery so bleeding from the ear can be monitored.
- The ear tip is clamped with a forceps and cut off with a scalpel. Bleeding is staunched with the cauterising gun. This usually only achieves partial haemostasis so again the cat is placed in right sternal recumbency for monitoring.
- A straight arterial forceps is placed across the tip of the left ear. With the forceps in one hand keeping the pinna taut, the nurse uses a cauterising gun in the other hand to cut through the tissue in a straight line just below the line of the forceps. This technique requires some practice to achieve a distinctly surgical finish.
Ideally the cat would be transferred to a hospitalisation cage for recovery. This gives them maximum space and allows the nurse to clean the cage and replenish food and water in safety. The hospitalisation cage can also accommodate a litter tray.
Not all practices or TNR groups will have the luxury of hospitalisation cages. As an alternative, the cat can be returned to the trap or placed in a secure carrier with its head facing the door. The trap or carrier should be clean and lined with newspaper, puppy pad and vet bed, if these are available. Surround and cover the cat with strips of newspaper to keep them warm. Cover the trap or carrier with a clean towel or blanket and keep the cat in a warm environment at least until it is holding its head up and beginning to move around. Check on the cat regularly. Once the cats are sitting up you can provide a small amount of wet food mixed with warm water in a bowl or coop cup. (Remember that the cats may not have eaten in up to 48 hours because they are fasted the day before trapping and may have been dropped into the clinic the evening before surgery.) This is an ideal opportunity to give the cat an oral worm dose mixed in with the food, as hunger is a great sauce!
Male cats can be released 24 hours after surgery and sometimes they are so agitated by confinement that they should be released as little as twelve hours after surgery. This should be decided upon by the vet.
Female cats should be confined for a minimum of 24 hours, although lactating cats whose kittens could not be relocated should be returned as soon as the vet deems it safe to do so. Cats that were heavily pregnant should be held for at least 48 hours and ideally longer if a hospitalisation cage can be provided. Again weigh the benefits of a monitored recovery against the stress of confinement. Some of the tamer, younger ferals can cope with a longer confinement than 24 for 48 hours. Use your judgement based on the cat’s behaviour and treat each case individually.
For the vast majority of feral cats, recovery after spay/neuter is uneventful. But because there may be unexpected complications during surgery and because we don’t necessarily know what underlying diseases the cats may have, it’s important to monitor them very carefully. Prolonged recovery time may be anaesthetic-related or due to hypothermia. The cats should also be monitored for post-operative haemorrhage.
Anaesthesic drugs may effect renal perfusion. Cats with renal dysfunction may have difficulty in recovery. The vet may palpate the kidneys in an older cat once they are anaesthetised, but of course, the findings will not be conclusive. To date Limerick Feral Cats have lost two cats to anaesthetic death. In both cases the patient failed to fully regain consciousness and was euthanised. Both were older male cats, although the significance of this has not been fully understood. On one other occasion, we were alerted by the caretaker several weeks after surgery that one tom wasn’t eating, had retreated into the cats’ shelter and was so weak that she had no difficulty in handling him. ‘Mucks’ was rushed to the vet and was found to be icteric, indicating hepatic dysfunction. He was put to sleep.
When the cat is being discharged back to the care of the TNR group, they will appreciate any information you can provide on the cat so that it can be added to the group’s records. The TNR group will be interested to hear the following:
- The cat’s gender
- A rough estimate of age based on the condition of the teeth and general appearance
- If female, the cat’s pregnancy status and if she had complications such as pyometra
- The cat’s ecto-parasite burden and if it received an acaricide
- The cat’s FIV/FeLV status, if a blood test was requested
- Confirmation that the cat was ear-tipped
- Whether there were any complications during recovery
- The cat’s precise body weight so it’s worm dose will be measured more accurately
- The grounds for euthanasia, if this was decided upon by the vet