How safe is anesthesia in small animals?
Original Question: Hi can you talk more about anesthetics and safety especially in small animals? - Anonymous
Working in a practice that sees a variety of small mammals and other “exotic” pets as well as cats and dogs, I am indeed familiar with the general hamster medicine and surgery. I would say on average, I see 2-3 hamsters per week, and sometimes all in the same day. In general, they are fun little pets and straightforward to care for. There are several types – the one featured in this article is a dwarf hamster, the smallest ones we see as pets. I have treated ones as small as 30 grams – very tiny! Unfortunately, traumatic injuries are common with these pets as they are very active, quick and small. I have personally performed a successful hind limb amputation on a dwarf hamster. I know my colleague has done several as well. These animals do remarkably well recovering from surgery – the one I amputated was running around her cage an hour after waking up from surgery. We didn’t need to use an e-collar for that one, but little rodents tend to chew out anything foreign (sutures, staples) in their skin. On occasion, we see rats chewing on their sutures or surgery sites and causing problems. Sometimes you have to be creative with things to prevent self-trauma! I remember I splinted a forelimb of a dwarf hamster for a closed fracture, and the splint was about half the size of the pet! I had to cover it with several layers of tape and vet wrap so that he couldn’t damage it.
Regarding the anaesthesia – any sedation or anesthetic in a small mammal carries a higher risk of anesthetic complications than it does for dogs and cats. One reason is that it is nearly impossible to protect the airway of these tiny animals with an endotracheal tube – commercial tubes are just not made that small, and visualizing the glottis is a problem in many of them as well. This can lead to increased risk of aspiration and reduced ability to control anesthetic and oxygen delivery. Another issue is that many small mammals can have underlying heart, respiratory or organ disease that we cannot easily detect prior to an anesthetic event (which would be the case with dogs and cats). IV catheter access is not possible in tiny hamsters, but we are able to obtain IV access on some rats. The effects of drugs and dose ranges for small mammals are quite different than in dogs and cats, and this presents challenges as well.
Typically, if we were doing a major surgery on a hamster we would give injectable pre-medication intramuscularly, and then place the animal in an incubator with oxygen for 10-15 minutes. We would then induce anesthesia with isoflurane via facemask. The pre-medication can help with pain and excitement, thereby reducing the level of isoflurane needed (which we want to limit as much as possible!). In a hamster, we would likely give subcutaneous fluids during the surgery to provide some fluid volume support (since we don’t have IV access). We have emergency drugs calculated and drawn up in syringes all ready to go if needed, and have a technician monitoring the heart rate and rhythm, resp. rate and depth very closely throughout. We do try to obtain other measurements, but on the tiniest of patients, the machines just don’t work! For example, typically our pulse oximetry machine only reads up to 300bpm heart rate, and many very small mammals will be far above this rate. On recovery, the pet would be again placed in the incubator with oxygen, until it is mobile.
I hope this helps,
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