In veterinary medicine, anesthesia for small animals is a vital tool that helps veterinarians carry out important procedures and enhances animal well-being. However, a smooth and successful anesthetic experience entails careful planning, precise technique, and a deep understanding of small animal physiology.
Recommended course: Advanced Anesthesia for Small Animals
Pre-anesthetic considerations
An extensive pre-anesthetic evaluation establishes the basis for a secure and effective procedure. It allows veterinarians to evaluate risk factors and underlying physiological changes or pathological diseases that will impact the anesthetic plan.
According to the American Animal Hospital Association (AAHA), the factors to be evaluated during a pre-anesthetic patient evaluation include:
- Medical history
- Physical examination
- Age
- Breed or size
- Temperament
- Patient diagnostics (risk factors and specific patient concerns)
Pre-anesthetic planning will also consider the type of procedure, clinical staff training, and time of day.
Pre-operative bloodwork
Pre-operative bloodwork can reveal important information about a patient’s internal health. The test results are baseline values necessary for patient evaluation. There may be a need for more tests depending on the veterinarian’s initial assessment, the medical history of the patient, age, and the medical procedure that will be performed. The results of these tests enable veterinarians to identify potential anesthetic risks and tailor their approach accordingly.
Fasting and pre-medication protocols
How long should an animal patient fast before surgery? This depends on several factors, including the species and type of procedure that will be performed. Having an empty stomach during surgery can avoid aspiration of food particles, but prolonged fasting can increase a patient’s risk for dehydration and electrolyte imbalance. Achieving optimal equilibrium is fundamental.
Pre-anesthetic fasting intends to reduce anesthetic complications, specifically gastroesophageal reflux (GER), esophagitis, and aspiration pneumonia. Researchers have reported that anywhere from 17 to 50% of dogs experience GER under general anesthesia. These are potentially common, and serious, complications (Veterinary Practice News, 2021).
Source: AAHA
Pre-anesthetic regimens
Pre-anesthetic regimens aren’t a ‘one-size-fits-all’ approach. Different groups of medications are generally used to achieve specific goals. These include tranquilizers, sedatives, anticholinergics, and analgesics. The choice and dosage of pre-anesthetic drugs depend on several factors, including
- Age. Younger animal patients can tolerate higher doses of tranquilizers than senior patients.
- Health conditions. Adjustments in the selection, dosage, or medication may be required for patients diagnosed with specific medical issues.
- Type of procedure. Minimally invasive procedures might utilize a lighter pre-medication regimen compared to major surgeries.
Communicating with clients
Pain management and patient comfort are primary concerns of pet owners and should be addressed in every anesthetic strategy. The main goal of open client communication is to instill a feeling of confidence in pet owners that the anesthesia team possesses the empathy, knowledge, and state-of-the-art equipment to administer the safest anesthetic for their pets.
Pet owners need to be assured that specific methods will be used to reduce patient discomfort and stress levels, before they leave home, while they are in the hospital, and during their recuperation at home. Providing a clear and concise explanation of the anesthetic process can help reduce their fears and anxieties.
Client communication tips
- Explain the process their pet will have to undergo, including the pre-anesthetic exam, laboratory work, and fasting protocols. The purpose of pre-medication should also be explained.
- Discuss what anesthesia options are available and what factors are considered in deciding which one to use.
- Always remember to talk about the inherent risks associated with anesthesia. But always emphasize the safety measures that the team observes to minimize potential risks.
Anesthetic techniques for small animals: A multi-modal approach
Modern veterinary anesthesia now uses a multi-modal approach that combines several drugs and techniques to achieve balanced anesthesia. Injectable and inhalation drugs are generally used, with injectables often given at the start of anesthesia to induce a state of unconsciousness and pain relief. Combining specific drugs can help maintain the desired anesthesia level throughout the surgical process.
Benefits of a multi-modal approach
- By using multiple drugs at lower doses, the potential side effects associated with high doses of a single drug are significantly minimized.
- Multi-modal anesthesia allows the incorporation of analgesics into the anesthetic plan. This can promote better pain control throughout the procedure as well as post-operatively.
- By targeting different elements of anesthesia (pain, sedation, and muscle relaxation), a more stable and controlled anesthetic plane is achieved, thus improving patient safety and stability.
Monitoring a patient during anesthesia
Veterinary professionals must carefully monitor all patients under anesthesia to detect any potential complications and make appropriate adjustments to maintain an anesthetic plane that’s safe and stable. Key parameters to monitor include the heart rate (HR), respiratory rate and pattern, and red blood cell oxygen saturation (Sp02).
In some cases, advanced monitoring techniques, such as capnography and blood pressure monitoring, may be warranted. The decision to use any of these techniques usually depends on the patient and the type of procedure.
Fluid therapy management during anesthesia for small animals
Fluid therapy management is a frequently overlooked yet essential component of anesthesia. Anesthesia can disturb the fragile equilibrium of fluids in a small animal. Intravenous fluids are essential for maintaining hydration during surgery, facilitating optimal physiological function, and aiding in recuperation.
The hydration status of the patient is closely monitored by keeping a watchful eye on urine output, mucous membrane hydration, and skin tent.
Calculating an animal’s fluid needs
When it comes to fluid therapy, the individual fluid requirements of a patient are calculated based on several factors.
- Patient’s size and weight: Larger animals naturally require more fluids compared to their smaller counterparts.
- Pre-operative hydration status: Dehydrated patients may require additional fluids to correct pre-existing deficits.
- Blood loss during surgery: Anticipated blood loss during surgery necessitates adjustments to fluid rates to compensate for blood volume depletion.
- Type of anesthesia: Certain anesthetic agents have a diuretic effect, increasing urine output and potentially requiring higher fluid rates.
Pain management after anesthesia
Anesthesia makes it possible to perform important procedures, but it doesn’t eliminate the pain. Effective pain management is important to keep patients comfortable, promote recovery, and minimize complications.
Multi-modal strategies for pain control
A multi-modal strategy combines several techniques to achieve pain relief and comfort after anesthesia. Non-steroidal anti-inflammatory drugs (NSAIDs), analgesics (opioids), and local anesthetics are generally used for this purpose. The type of procedure, the health status of the patient, and how long pain relief lasts are important considerations in choosing appropriate pain medications.
Anesthesia and brachycephalic breeds
The anatomical features associated with brachycephalic breeds — stenotic nares, elongated soft palate, everted laryngeal saccules, and hypoplastic trachea — make anesthesia management challenging. The increased upper airway resistance causes increased respiratory work. Sedating brachycephalic breeds is risky because this can cause relaxation and hypoventilation, making them prone to hypoxia.
During the peri-anesthetic period, these breeds are also prone to aspiration and regurgitation, which can also increase their risk of hypoxia.
Specific considerations
To minimize risks, veterinary professionals should keep the following considerations in mind:
| Considerations | Other important information |
| As part of pre-operative management, require a short period of fasting before anesthesia, typically allowing for a light meal (wet food) about 4 hours before the anesthesia is administered. | Omeprazole is given 4 hours before induction of anesthesia to help reduce gastric acidity. |
| Sedative choices should be considered carefully. | Excessive sedation increases the animal’s risk for hypoxia. Acepromazine should be used with caution at routine doses because of its long duration, lack of reversibility, and vasodilating effects, rendering upper airway resistance even higher. Caution: Regardless of sedative choices, these patients need to be monitored closely whenever they are sedated. |
| Intubation can be challenging due to the long, floppy soft palate, large epiglottis, everted laryngeal saccules, and smaller-than-expected trachea. | Preoxygenation before intubation is warranted. This should be done with a mask, not just holding the machine Y-piece near the animal’s nares. If the dog struggles, don’t force it, as the oxygen consumption of struggling will negate any benefit of preoxygenation. Use a laryngoscope, and have a tongue depressor handy to push the soft palate dorsally. |
| Anesthetic maintenance, once you have a secure airway, should be routine. | Brachycephalic breeds have an increased vagal tone, so they may require a dose of glycopyrrolate or atropine during anesthesia to treat a low heart rate (depending on blood pressure). If high due to an alpha-2 agonist sedative, DO NOT give an anti-cholinergic). |
| Management of recovery involved the use of analgesics, but excessive sedation should be avoided. | Ideally, NSAIDs plus local anesthesia should be used. Dogs that are agitated/stressed/struggling during recovery will worsen their airway resistance and may require oxygen supplementation and sedation. Options for sedation include very low intravenous doses of alpha-2 agonists. |
Source: Breed Considerations in Anesthesia
Geriatric patients
Physiological changes, such as decreased organ function, the presence of pre-existing medical issues, and reduced physiologic reserve, can affect how geriatric pets handle anesthesia.
To minimize potential risks and promote positive outcomes for geriatric patients, anesthetic protocols are generally tailored to their needs. This can be achieved by:
- Identifying any pre-existing health issues by conducting a complete pre-anesthetic evaluation.
- Administering anesthetic medications at lower doses.
- Maintaining optimum body temperature.
- Promoting recovery and minimizing complications with effective pain management.
Anesthesia in emergency and critical care
Emergency and critical care situations call for quick action, including adjusting the methods of anesthesia to effectively handle the challenges that may arise. Physiological instability is generally present during emergencies and in critically ill patients. This warrants the need for adjustments to conventional anesthetic procedures including:
- The use of anesthetic agents with rapid onset, short action, and low organ toxicity.
- Assessing the patient’s respiratory status to determine whether to use inhalation or injectable anesthesia.
- Addressing any fluid and electrolyte imbalances before or during anesthesia.
- Performing minimally invasive approaches, if possible, to minimize stress in patients who are already compromised.
Close monitoring extends to the recovery period that starts when the anesthesia wears off until the patient is discharged.
Tips for a safe and comfortable recovery period
- Pain management. Pain control should continue to promote recovery and prevent potential complications
- Monitoring of vital signs to help identify potential issues
- Assessing neurological signs to ensure the patient is recovering well from anesthesia.
- Monitoring the patient’s hydration status through urine output and mucous hydration.
Discharge protocols
Once the patient is stable and ready for discharge, the veterinarian should give clear and detailed discharge instructions to the pet owner so they can provide optimal aftercare at home. Full instructions should cover pain medication schedules and potential side effects, dietary restrictions, activity limitations, wound care (if applicable), and a schedule of follow-up appointments.
