Anesthesia and surgery

Click to access the 2011 Anesthesia Guidelines for Dogs and Cats.

Preanesthetic considerations

Patient Assessment. The importance of complete and accurate historical information cannot be overstated, including current medications (e.g., over-the-counter, prescription, alternative, supplements) with regard to their potential impact on anesthesia and recovery. Perform a complete and thorough physical examination, including assessments of weight, temperature, pulse, respirations, and pain.

Consider a preanesthetic blood pressure evaluation, especially in cats. Pay special attention to cardiopulmonary status. If any physical abnormalities are detected (e.g., heart murmur, arrhythmia, poor pulse quality, abnormal respiratory sounds), consider expanding the cardiopulmonary evaluation to include thoracic radiographs, electrocardiography, echocardiography, and/or blood pressure measurements. 28,46 Whether a preanesthetic electrocardiogram is needed for pets without detectable abnormalities is uncertain. There is some evidence that conduction abnormalities may exist subclinically (especially in cats) or be overlooked because of animal disposition, operator error, etc.28,46 An electrocardiogram is strongly recommended when abnormalities are found on auscultation.

Laboratory Evaluations. All healthy senior pets should have wellness screening tests along with measurement of electrolytes and a platelet count, ideally within the 2 weeks preceding anesthesia. However, for healthy senior pets that have had routine wellness tests within the previous 6 months, the practitioner must determine which tests should be repeated or added, based on the pet’s age (e.g., middleaged versus senior), risk factors, and the procedure to be performed. In addition to any tests not done in the previous 6 months, a complete blood count and dipstick urinalysis with specific gravity should be repeated prior to anesthesia. Obtain at least a hematocrit and platelet count if surgery is planned. Remember that automated platelet counts are unreliable in cats, so if the platelet count is low, a manual recount should be performed. Consider further workup if test results are not within the normal ranges.47

When anesthesia of a sick pet is necessary, perform the sick pet screening [Table 3] and compare the results to any earlier wellness screening tests. Perform additional tests as appropriate based on previous, ongoing, or new health issues discovered in the history, examination, and laboratory results. For example, perform coagulation function tests on at-risk animals, such as those with liver disease, malassimilation/ maldigestion disorders, NSAID usage, and breed predisposition.

Client Communication. Before anesthesia, discuss all risks and benefits with the client and obtain written, informed consent for all procedure(s). Prepare postoperative instructions. Provide clients with clear, concise, verbal and written take-home instructions that include information about possible complications, drug effects, nursing care, nutritional management, home monitoring, and after-hours veterinary phone contact.

Patient Management. Create a plan for anesthesia, analgesia, intravenous fluid administration, antimicrobial therapy, and body temperature maintenance during surgery.48,49 Begin analgesia prior to induction of anesthesia, giving special consideration to the combination of systemic analgesia and local or regional anesthetic blocks. Perioperative pain is best controlled by an aggressive, preemptive, multimodal approach.50,51

Intravenous access via an indwelling catheter is necessary for anesthetic induction, intraoperative fluid administration, and administration of appropriate medications. Initiate fluid preloading when indicated (e.g., renal disease, dehydration). When antimicrobial therapy is specifically indicated, begin the medication prior to surgery.52,53 Provide preoxygenation when indicated (e.g., obstructive upper airway disease, cardiac disease) via mask, oxygen cage, nasal cannula, or other methods. Ensure adequate ventilation via endotracheal intubation for general anesthetic procedures. Provide manually or mechanically assisted respiration as necessary.

Based on animal risk factors, consider placing an indwelling urinary catheter to measure fluid output during and after surgery, and/or the measurement of central venous pressure to prevent both under-hydration and over-hydration. Detailed attention to cardiopulmonary and renal functions is crucial for the successful outcome of anesthesia in senior animals. Close monitoring is essential during all stages of anesthesia. The greatest risks to the animal occur during the induction of anesthesia and from the time anesthetic agents are discontinued until full recovery.

During anesthesia

One trained person should be dedicated to the monitoring and recording of vital parameters, such as body temperature, heart rate and rhythm, respiration, oxygen saturation via pulse oximetry, blood pressure, and end-tidal carbon dioxide. An apnea monitor is also helpful. Intravenous fluid support is essential, and care should be taken to customize the type and rate of fluids administered (e.g., lower rate with cardiac disease, increased rate with renal failure).54,55 Continue pain management, giving special consideration to constant- rate infusion of intravenous analgesics.

Postoperative/postanesthetic considerations

Maintain an open airway via intubation until the animal is swallowing. Continue oxygenation when appropriate, as described in the preanesthetic section of this report. Continue to maintain body temperature and to provide intravenous fluid support at least until the animal is ambulatory (or stable), or for longer as indicated (e.g., dehydration, hypothermia, renal compromise, other metabolic disorders).

Regularly monitor and record vital signs. Continue a preemptive and multimodal approach to pain. The adaptive mechanisms of animals make it difficult to accurately assess their degree and perception of pain; therefore, administer pain medications on a schedule appropriate for the drug(s) and the condition being treated. Do not wait for the animal to show signs of pain.56-58 Continue to assess the individual needs of each animal, as all individuals react differently to pain and to medications for pain.

Provide appropriate nursing care for recumbent animals, including warming and turning, human touch, and compassionate verbal encouragement. When recovery is delayed or prolonged, promote movement via massage, passive motion exercises, and sling-assisted walking.