Feline anesthesia considerations and protocols

Doses on this pageEvery dose below is quoted from the cited source. Verify against the current label/formulary and the patient's full clinical picture.

Equipment and breathing circuits

The AAFP guidelines treat anesthetic equipment as life-critical [1]. They list the following as essential: a non-rebreathing circuit with a manometer, a safety pop-off relief valve, an esophageal stethoscope, a thermometer, a blood pressure monitor, and a pulse oximeter that displays a waveform [1]. Capnography with a waveform, a fluid pump, and an ECG are listed as recommended extras [1]. The panel calls for leak testing the breathing circuit before every anesthetic [1].

The size of the cat drives these choices. The guidelines note a lung capacity of roughly 400 ml in an average cat. They warn that the high oxygen flows used with non-rebreathing circuits can injure the airway in under 30 seconds if pressure builds [1]. The panel recommends non-rebreathing circuits in all cats. It says modern low-dead-space circle systems can also be used safely in cats over 3 kg. It states the oxygen flush valve "should never be used when a cat is connected to an NRC" [1]. Equipment dead space, per the guidelines, should be no more than 2 to 3 ml/kg, and a single elbow adapter may add up to 8 ml [1].

Preanesthetic assessment and preparation

According to the AAFP panel, every cat should have a preanesthetic physical examination. History can be incomplete for outdoor or multi-cat households [1]. Stress raises heart rate, blood pressure, and respiratory rate and may prevent a full exam. For elective cases where the cat has become distressed, the panel describes rescheduling as "a viable option" with a plan to address fear first [1].

Per the guidelines, the decision to run laboratory tests should be based on history, examination, risk assessment, and practice policy. Chemistry, CBC, and urinalysis are recommended routinely from the mature (7 to 10 years) life stage onward [1]. The panel cites a retrospective study of cats with a mean age of 11.6 years. About 16% had concerning results, and protocols were changed or procedures postponed in 9% [1]. It also notes that sedation with dexmedetomidine can alter heart rate, echocardiographic findings, blood pressure, and blood glucose [1].

On fasting, the guidelines state that traditional 6 to 12 hour fasts "are not evidence based" [1]. They add that, with no feline data, a small wet meal 3 to 4 hours before anesthesia may be used at the clinician's discretion, with water available until premedication [1].

Comorbidities the guidelines address

The AAFP panel singles out several conditions [1]:

• Hypertrophic cardiomyopathy. Alpha-2 agonist use is described as controversial, and the benefits of low doses may outweigh risks.
• Hyperthyroidism. The aim is to reach a euthyroid state before elective procedures.
• Kidney disease. Preanesthetic fluids and blood pressure management are emphasized.
• Diabetes mellitus. Insulin dosing is tied to the preprocedure glucose, and these cats are scheduled first in the day.
• Asthma. Cats stay on their maintenance medications, and the team prepares for rapid decompensation.
• Obesity. Drug doses are based on ideal body weight.
• Urinary obstruction. When there are hyperkalemia-related ECG changes or blood potassium is above 7 mEq/l, immediate therapy is instituted before sedation or anesthesia.

The panel does not consider ASA classification essential for every cat because it is subjective [1]. It cites one feline study in which ASA status was a better predictor of complications than age, and cats with ASA 3 or higher had a significantly increased risk of complications [1].

Sedation, premedication and induction

The AAFP guidelines describe two approaches to procedural sedation [1]:

• Use a sedative such as dexmedetomidine and accept its ceiling effect.
• Add an anesthetic agent such as ketamine, alfaxalone, or tiletamine/zolazepam, which sedates at low doses and anesthetizes at higher ones.

Opioids, benzodiazepines, and alpha-2 agonists are reversible [1]. The panel also recommends giving cats a place to hide, such as a box or igloo bed from which they can be injected [1].

For premedication, the guidelines report that alpha-2 agonists give reliable dose-dependent sedation but reduce cardiac output [1]. Anticholinergics should not be combined with them because of possible significant hypertension [1]. Acepromazine is described as inconsistent in cats and able to make intraoperative hypotension harder to treat [1]. Benzodiazepines are not considered suitable alone or with opioids in young or adult healthy cats [1]. The ISFM panel adds that alpha-2 agonists should be reserved for cats with stable cardiovascular function and that atipamezole should always be on hand [4].

Induction can be by SC, IM, or IV injection or by inhalant [1]. The AAFP panel states preoxygenation "should be standard practice" because all induction drugs can depress breathing [1]. It calls chamber induction a "last resort," noting that agitated, unpremedicated cats need more inhalant and release more catecholamines [1]. During maintenance, the guidelines report that isoflurane and sevoflurane can cut cardiac output and blood pressure by 50 to 70% at surgical concentrations, and that opioid infusions can reduce inhalant needs [1]. The panel recommends limiting propofol infusions to under 30 minutes [1].

Airway management

The AAFP panel describes the feline larynx as small, prone to spasm, and easily damaged. It reports tracheal tears with outcomes ranging up to death [1]. Its intubation sequence includes [1]:

1. Preoxygenation for 3 minutes if tolerated.
2. Sternal positioning.
3. Topical 2% lidocaine, no more than 0.2 ml, dropped on the arytenoids, followed by a 60 to 90 second wait.
4. Gentle advancement of the tube on inspiration.
5. Visual confirmation of the arytenoids on either side of the tube.

The tube should reach no farther than the thoracic inlet. The cuff is inflated in small air increments until there is no leak at a circuit pressure of 16 to 18 cmH2O [1].

The guidelines present a feline supraglottic airway device as an alternative to an endotracheal tube. They cite studies showing faster placement, fewer attempts, less propofol, and less post-removal discomfort [1]. The authors of the UK neutering study note that intubation has been associated with increased mortality in cats [2]. In their study, 10 cats needed reintubation for tube obstruction, which the authors argue supports routine capnography [2].

Monitoring and common complications

The AAFP panel cites evidence that pulse and pulse oximetry monitoring are associated with lower mortality, and that a dedicated anesthetist reduces deaths [1]. It recommends recording parameters at least every 15 minutes and preparing a patient-specific emergency drug sheet for each anesthetic [1]. The normal heart rate in anesthetized cats is given as 100 to 180 bpm. The esophageal stethoscope is rated the most reliable heart rate method in the panel's comparison table [1].

For hypotension, the guidelines describe stepwise responses [1]:

1. Reduce the inhalant after checking depth.
2. Give a crystalloid bolus, unless cardiomyopathy or anuric renal failure makes it inadvisable.
3. Add drugs that allow lower vaporizer settings.
4. Use a positive inotrope if hypotension persists.

Cats lose heat quickly because of their surface area. The panel recommends starting temperature support in the holding area before premedication and considers active warming more effective than passive methods [1]. It also reports rebound hyperthermia after anesthesia, adding that this "is not a reason to withhold opioid analgesics" [1].

The retrospective UK study of 1,019 neutered cats linked hypotension to acepromazine premedication, higher maximum isoflurane, longer anesthesia, and lower body weight. It linked bradycardia to medetomidine [2]. The authors caution that the study was retrospective, protocols were not standardized, data were missing, and events may have been underreported [2].

Recovery, team roles and analgesia

According to the AAFP guidelines, 60% of anesthetic-related cat deaths happen during recovery, especially the first 3 hours [1]. For that reason, monitoring should be as close as during anesthesia, with a capnograph left on the tube until extubation [1]. The panel describes optimal recovery as consciousness and extubation within 15 to 30 minutes, with normal vital signs and sternal recumbency [1]. Pain is named as the most common differential for emergence delirium [1].

In the UK study, anesthesia was monitored by registered or student veterinary nurses with no other duties. Recovery, however, was often handled by patient care assistants, and the only death occurred after dyspnea in recovery [2]. The authors argue that handovers should be clear and that receiving staff should be trained to recognize problems and call for help [2]. Safety checklists were completed in only 28.9% of cases [2]. The AAFP panel calls veterinary checklists "highly recommended" [1].

For pain, the ISFM consensus panel recommends preventive and multimodal analgesia built on opioids, local anesthetics, and NSAIDs, with validated pain scales used to guide rescue analgesia [4]. It notes that ketamine-based protocols may falsely raise pain scores early in recovery [4].

Before using any dose aboveVerify against the current label/formulary and the patient's full clinical picture.