Anesthesia always carries with it both short and long term risks so we feel that one of the most important preventive health measures that veterinarians should be concerned about is doing everything we can to make anesthesia as safe as possible. It is for this reason that we don't offer bargain basement spays, neuters, and other surgeries. It just makes no sense to spend money on the best food, vaccines, toys, beds, and other cat necessities and then cut corners on anesthesia.
This is our video on anesthesia safety. It goes into some detail as to why a proper anesthesia is more than just keeping an animal alive.
There are a lot of physiologic changes that occur when an anesthetic is administered. If not monitored and supported, these changes can lead to unnecessary suffering, unrecognized organ damage, and even death.
At North County Cat Hospital, even for surgeries as seemingly simple as neuters and spays, an anesthesia includes:
We perform an examination on the day of the procedure to look for anything that might affect the safety of the anesthesia. The examination helps to determine the anesthetic protocol and doses to be used and gives us baseline parameters.
A blood panel is done either on the day of the procedure or before. It is to look for things that aren't revealed by the physical examination and that might impact the anesthesia.
Preanesthetic medications help calm the patient and prevent pain. They also decrease the amount of anesthetic agent needed to induce the patient.
I.V. catheters are a critical part of any good anesthesia. They allow us to give relatively large amounts of fluids rapidly and they allow immediate administration of medications.
Almost all anesthetics cause the blood vessels to dilate. Unless relatively large amounts of fluids are given rapidly at the onset of this dilation, there isn't enough blood volume to fill these vessels and this often leads to a sudden and severe drop in blood pressure accompanied by a proportional drop in blood flow. This isn't usually enough to cause death but it is enough to cause significant damage to internal organs that can have future consequences, such as premature kidney disease.
The induction is the time that the patient goes from being fully awake to fully anesthetized and is one of the riskiest parts of the procedure. To minimize the risks, it is important to induce the patient quickly. This allows rapid control of breathing and minimizes the time spent in the excitement phase of anesthesia which is physiologically taxing and dangerous. Induction via intramuscular injection or "boxing down" or "masking down" generally take longer and are more stressful and dangerous.
When animals are under anesthesia, they lose their gag reflex. If they vomit while under they can potentially aspirate stomach contents into the lungs which is life-threatening. An endotracheal tube prevents this from happening. The tube also allows anesthetic and oxygen to be administered more easily. You will see an orange endotracheal tube in the part of video that shows what we don't do. These old style tubes are more likely to cause a tear in the trachea. We don't use them.
Because it does not need to be metabolized by the body and because the dosage can be adjusted very quickly, gas anesthetics are generally considered the safest for the patient.
Under anesthesia, the body loses some of its ability to regulate internal temperature and there is a tendency for that temperature to drop. This can have severe physiologic consequences. Heat support in the form of an externally applied source of heat is usuallly needed to keep the temperature within the normal range. We use a Bair Hugger which warms with warm air.
In the video, you will see a cat who is covered in bubble wrap at another veterinary hospital. The intent is to insulate the cat, but if no external heat is applied, the patient's temperature will usually drop. We don't use bubble wrap at North County Cat Hospital.
The first lesson of anesthesia monitoring in veterinary school was "look at the patient." There are times when an anesthetized patient will have more than a dozen wires, leads, or tubes attached. We still always look at the patient to help in the assessment of their current condition.
A pulse oximeter is used to give us a moment by moment reading of the pulse rate and rhythm and the oxygen content of the blood blood. If there is a problem with oxygen delivery, it is critical to know as soon as possible.
We feel that the biggest risks of anesthesia in healthy cats, and one that is often overlooked, is the possibility of the blood pressure getting too low. Low blood pressure decreases the amount of blood reaching the organs and even if there is plenty of oxygen in the blood, if that blood can't reach the organs, irreversible damage is caused to the internal organs. This can happen without any outward sign. The patient can wake up and look fine, but if damage was done, it will eventually cause a problem.
Some anesthesiologist consider the monitoring of carbon dioxide to be the most important parameter for our machines to monitor. It will sometimes alert us to a critical problem before any of the other methods of monitoring.
Whether anesthetized or not, if a warm blooded animal's temperature gets to high or too low, it can have serious consequences. We use a probe that constantly monitors the temperature of our anesthetized patients and alerts us if the temperature falls outside of our narrow parameters.
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