There are various reasons why a cat should be sedated or anesthetized, from aggressiveness or fear in consultation that make it unexplorable, to minor surgical procedures or large caliber operations. Anesthesia, especially general anesthesia, is very safe, contrary to what many caregivers think, since with the knowledge current drugs and advances in monitoring, the percentage of death by anesthesia is less than 0.5%.
But How long does it take for a cat to recover from anesthesia? It is one of the many questions that come up to cat guardians who will undergo this procedure. In this article on our site we tell you everything about anesthesia and sedation in cats, what to do beforehand, its phases, effects, drugs and recovery.
Difference between sedation and anesthesia
Many people confuse sedation with anesthesia, but the truth is that they are two very different processes. sedation consists of a state of central nervous system depression in which animals fall asleep with little or no response to external stimuli. On the other hand, anesthesia can be local or general, in the latter case with generalized loss of sensation characterized by hypnosis, muscle relaxation and analgesia.
However, before your cat undergoes surgery, your veterinarian will discuss the pre-anesthetic examThis is very important to assess the he alth status of your feline companion and to plan the best anesthetic protocol for their individual case. This consists of:
- Complete clinical history (existing diseases and medication).
- Physical exam (vital signs, mucous membranes, capillary refill time and body condition).
- Blood tests and biochemistry.
- Urine analysis.
- Electrocardiogram to assess the state of the heart.
- In some cases also x-rays or ultrasound.
How long does sedation last in a cat?
It will depend on the type of procedure used which will vary according to the duration and intensity of the procedure and the individual variability of the cat. Combinations of sedating, tranquilizing, and pain-relieving drugs can be used to sedate a cat, such as the following:
Phenothiazines (acepromazine)
It is a sedative that takes a maximum of 20 minutes to act and sedation lasts about 4 hours. The animal must be oxygenated if it is used as a sedative due to the cardiovascular depression it produces. It is characterized by:
- Antiemetic (does not induce vomiting).
- Deep sedation.
- It has no antagonist, so the cat will wake up when the drug is metabolized.
- Bradycardia (low heart rate).
- Hypotension (low blood pressure) lasting up to 6 hours.
- Do not produce analgesia.
- Moderate muscle relaxation.
Alpha-2 agonists (xylazine, medetomidine and dexmedetomidine)
They are good sedatives that take a maximum of 15 minutes to act and have a shorter duration of sedation, only about 2 hoursThey have an antagonist (atipamezole), so if it is used they will wake up shortly without having to wait the necessary time until the sedative effect wears off. It must be oxygenated due to the cardiovascular effects they produce:
- Good muscle relaxation.
- Moderate analgesia.
- Emetic (induces vomiting).
- Bradycardia.
- Hypotension.
- Hypothermia (low body temperature).
- Diuresis (increased urine production).
Benzodiazepines (diazepam and midazolam)
They are relaxers that take a maximum of 15 minutes to act and last from 30 minutes to 2 hours. They have an antagonist (flumazenil) and produce the following effects:
- Powerful muscle relaxation.
- It has no effect on the cardiovascular system.
- No sedans.
- Do not produce analgesia.
Opioids (butorphanol, morphine, methadone, fentanyl, and pethidine)
They are good analgesics often used together with sedatives to contribute to sedation or to prepare the cat for anesthesia. They tend to depress the cardiorespiratory center quite a bit and some, like morphine, are emetic. Opioids such as morphine were previously believed to be contraindicated in cats due to their stimulant effects. It is currently known that more than being contraindicated, can be used without problems but maintaining the dosage, route, schedule and combination of drugs, since the problems arise if overdosed, causing dysphoria, delirium, motor excitability, and seizures.
On the other hand, while butorphanol produces less analgesia and is used in sedation or for premedication before general anesthesia, methadone and fentanyl are the most used in this species forcontrol pain during surgery due to its greater analgesic power. They have an antagonist to reverse their effects called naloxone.
Therefore, the duration of sedation will depend on the metabolism and state of the cat itself. The average is about 2 hours if the sedation is not reversed with the antagonist. By combining two or more drugs from different classes, it allows to enhance the desired pharmacological effects and thus reduce doses and side effects. For example, the combination of butorphanol with midazolam and dexmedetomidine is usually very effective in sedating a nervous, sore, stressed or aggressive cat in the office, and having an antagonist reverses the effects, allowing them to return home awake or slightly sleepy.
How long does anesthesia last for a cat?
Anesthetic procedures consist of four phases:
Phase 1: Premedication
Its main purpose is to create an "anesthetic cushion" to decrease the dose of subsequent anesthetics, reducing dose-dependent side effects, reduce the stress, fear and pain of the cat. It is done by administering different combinations of sedative drugs, muscle relaxants and analgesics that we have discussed in the previous section.
Phase 2: anesthetic induction
By administering an injectable inducing anesthetic such as alfaxalone, ketamine or propofol to cause the cat to lose reflexes and thus allow intubation (introduction of a tube into the feline trachea for introduction inhalation anesthetic) to continue the anesthetic process.
These phases usually last about 20-30 minutes in total until the drugs take effect and allow the next step.
Phase 3: maintenance
Consists of the continuous administration of an anesthetic agent, either in the form:
- Inhalation: (such as isoflurane) along with analgesia (opioids such as fentanyl, methadone or morphine) and/or NSAIDs, such as meloxicam, which will improve pain and inflammation in the postoperative period. The latter can also be administered at the end of anesthesia together with antibiotics to prevent possible infections.
- Intravenous: propofol and alfaxalone in continuous infusion or repeated boluses together with a strong opioid such as fentanyl or methadone. Use for more than one to two hours in cats is not recommended to avoid slow recovery, especially with propofol.
- Intramuscular: Ketamine and opioid for short 30-minute surgeries. If a little more time is required, a second dose of intramuscular ketamine can be given, but not more than 50% of the initial dose.
The duration of this phase is variable and will depend on the type of surgery your cat is going to undergo. If it is a cleaning, around an hour; a castration, somewhat less, as well as obtaining biopsies; if a foreign body such as hairballs is operated on, it can take a little longer, while if they are traumatology operations, they can last several hours. It also depends on the skill of the surgeon and possible intraoperative complications.
Phase 4: Recovery
After the end of anesthesia, resuscitation begins, which should be quick, gentle, stress-free and pain-free if respected the procedure, the combinations and the doses of drugs used. It will be necessary to monitor your constants, your condition, your temperature and later possible complications, such as fever and vomiting, which may indicate an infection. In general, a he althy adult cat, well fed, vaccinated and dewormed usually recovers from anesthesia 2 days after the intervention and its sequelae10 days later
So the duration of anesthesia is variable depending on the duration of the surgery, the state and metabolism of the animal, the skills of the surgeon, the complications, the drugs used and the resuscitation time. Thus, while some anesthesias last an hour or less, others can last several hours But don't worry, with a correct anesthetic protocol, analgesia, control of vital signs and temperature by the anesthesiologist, your cat will be safe and without feeling any pain or stress regardless of the duration of anesthesia.
My cat is not recovering from anesthesia
The time that the animal may take to recover from the anesthesia will depend on the amount that has been administered, the type of anesthesia with which they have worked and also the cat itself. Even if your little feline has fasted prior to surgery, he may throw up some bile or leftover food in his stomach or become nauseated. Don't worry, it's normal if alpha-2 sedatives or some opioids have been used. It is also normal that, after waking up, the cat goes to the sides disoriented or meows for no reason, that it takes a few hours to want to eat or that it urinates a lot that day to eliminate the extra liquid administered with fluids during anesthesia. During recovery, cats need to be in a warm, dark, quiet place
Sometimes cats can take a long time to wake up. Keep in mind that cats are very different from dogs in many ways. In anesthesia they were not going to be less. In particular, the metabolism of drugs in cats is much slower than in dogs, so they can take longer to wake up. Your cat may take longer to recover from anesthesia for the following reasons:
Enzyme deficiency
One of the most important pathways for drug metabolism for subsequent elimination is conjugation with glucuronic acid. However, cats have a deficiency of the enzyme glucuronyltransferase, which is responsible for this. Due to this, the metabolism of drugs that use this pathway is much slower by having to use an alternative: sulfoconjugation. The origin of this deficit is found in feline eating habits. Being strict carnivores they have not evolved to develop systems to metabolize plant phytoalexin. Therefore, in cats certain drugs (ibuprofen, aspirin, acetaminophen, and morphine) should be avoided or used at much lower doses than in dogs that do not have this problem.
Propofol as an anesthetic
Use of propofol as a maintenance anesthetic for more than one hour may lengthen recovery times in cats. In addition, repeated anesthesia with propofol in felines can lead to oxidative injury and the production of Heinz bodies (inclusions that form on the periphery of red blood cells from destruction of hemoglobin).
Drug overdose
Cats usually weigh little, especially if they are small, so they can be overdosed more easily with the consequent prolongation of the recovery process by they take much longer to metabolize to stop their action. In these cases, only antagonist drugs would be indicated, but bearing in mind that awakenings can be abrupt and dysphoric In fact, the tendency is to try more progressive awakenings and slow, with the help of relaxants such as benzodiazepines if necessary.
Hypothermia
Hypothermia in cats or drop in body temperature is common due to their small size and weight. The lower the temperature, the more difficult it is to metabolize drugs due to reduced enzyme function, lengthening recovery and awakening from anesthesia. This condition must be prevented by applying insulating materials to the animal and covering it with blankets or using heated surgical tables, applying tempered fluids, as well as maintaining the temperature of the operating room at around 21-24 ºC.
