Anesthesia drugs for the small animal patient (Proceedings) - Veterinary Healthcare


Anesthesia drugs for the small animal patient (Proceedings)


Inhalation Agents

Inhalation anesthetic agents are widely used in veterinary medicine today. Volatile anesthetic agents are delivered, and for the most part removed from the body by the lungs. The use of these agents requires an anesthesia machine that provides oxygen, a breathing circuit, and a facemask or endotracheal tube, as well as a way to remove accumulations of carbon dioxide. These components reduce the risk of morbidity or mortality to the patient by facilitating ventilation and increasing oxygenation. Anesthesia induction with an inhaled agent is no safer to the patient than induction with injectable anesthetic agents. It is more that the patient is better supported with oxygen. The use of an inhaled anesthetic agent to maintain anesthesia for a prolonged period of time is a safe and practical method. The main advantage to an inhalation agent induction is the recovery will be rapid, depending on the amount of time the patient is asleep. Less drug metabolism by the liver is required when compared to injectable drugs. The two more common inhalation agents used in veterinary medicine today are halothane and isoflurane, newer agents are on the horizon such as sevoflurane and desflurane. Sevoflurane is experiencing a current rise in popularity due to increased marketing.

Local Anesthetics

A local anesthetic can provide total analgesia to the affected area. They have been applied topically to wounds or by local infiltration to a region of the body (ie: intercostal block or epidural injection) or they have been instilled into a body cavity to provide relief (intrapleural or intraperitoneal infusions). Local anesthetic agents can reduce the quantity of other analgesics needed to provide adequate pain relief.


Pain management has become a major focus in veterinary medicine, especially in the arena of anesthesia. It has become well established that attacking pain by more than one avenue using a multi modal approach is an effective pain management strategy. The use of NSAIDs has recently been touted as "the most widely used analgesics in veterinary medicine" Historically anesthesiologists have been leery to administer these drugs until the anesthesia period is over and the patient is in recovery. NSAIDs are associated with adverse effects on the GI, renal and hepatic systems as well as coagulation disorders. With the arrival of newer NSAIDs such as carprofen, deracoxib and meloxicam; NSAIDs are finding their way into the anesthetist's toolbox as another resource for pain management. Even with the newer drugs caution must still be advised. The patient's physical status, co-existing diseases, current medications and its physiological homeostasis during the anesthesia period must all be considered when choosing the best pain management. Is the use of an NSAID drug in this individual patient's best interest? If so, then which one and at what dose?


Analgesia, immobilization, amnesia, muscle relaxation and physiological homeostasis are the desired end-points for an anesthesia drug plan. Often the choice of drugs may be limited and your selection may not include the "optimal" drug of choice for a particular patient or situation. Your knowledge and experience with the drugs available to you is a cornerstone in the anesthesia drug plan. What are the advantages to these drugs? What are the disadvantages of these drugs? What are the needs of the patient and which drugs will best support this patient? Thinking your way through these questions as you develop an effective plan will require knowledge, understanding and experience with the drugs available at your facility. The advantage to a well-designed plan comes from the forethought used to generate the plan and anticipate complications. Know what you have to work with, know what the patient needs, anticipate problems and plan a response. Optimize your knowledge, skills and abilities to provide high quality anesthesia care and support for the patient.


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