Geriatric animals have less capability to keep warm. Use warming mats during procedures and when caged to help keep them warm. Warming the fluids prior to administration can also help maintain body temperature. Photo courtesy Dr. Michael C. Petty In general terms, geriatric patients are defined as those that have completed 75-80 percent of their anticipated life span.1 In humans, geriatric comorbidities are the main cause of mortality during anesthesia.2 There is no reason to think it is any different in our dogs and cats. The second largest reason is that in most geriatric patients, there is a decline in the normal “reserve capacity” which can impede their response to situations of stress, such as hospitalization and surgery.3 Not all dogs and cats have issues with major organ systems, but those of high consideration are the cardiovascular system, major organs, such as the liver and kidneys, and the respiratory system. Additionally, for unknown reasons, older patients require less injectable and inhalant anesthetic drugs to produce general anesthesia.4 The following is a list of common considerations when dealing with apparently healthy geriatric patients. It is not intended to serve as a guide for geriatric patients with significant or profound comorbidities. Additionally, this writing concentrates on pain management, which also overlaps with anesthetic protocols. It is not meant to be a guide for induction or maintenance of anesthesia. Pharmaceutical considerations: Acute pain Opioids Opioids are amazing pain drugs when used in acute pain settings, such as pre- and post-surgery, and in the case of trauma. Opioids are generally the safest and most effective agents available for the treatment of acute pain. Although many of us were taught to fear the serious side effects of opioids, these concerns were inappropriately extrapolated from experiences in human medicine.5 Opioids work on several levels, including the inhibition of pain at peripheral nociceptors, modulation of the pain signal in the spinal pathway, and reduced perception of pain in the brain. Modification of opioid doses for geriatric animals is not needed. Opioids can be classified into three types: Full agonists. These opioids produce dose-dependent analgesia—that is, the more administered (within safety limits), the greater the effect. They bind and fully activate opioid receptors, particularly the μ receptor. Clinical application: Used for procedures that have the potential for causing severe pain, including perioperative and trauma pain. Partial agonists. Partial agonists bind to opioid receptors with high affinity but produce a submaximal effect, even at higher doses. This ceiling effect limits both their analgesic potential and their potential side effects. Clinical application: Appropriate for mild to moderate pain. Agonist-antagonists. These drugs act as agonists at some opioid receptors (typically κ) and antagonists at others (typically μ). This class of opioids rarely causes dysphoria. They may displace full agonists from the μ receptor, potentially reversing their effects. Clinical application: Used for mild to moderate pain. They are useful for opioid reversal when dysphoria occurs with full agonists but still allow partial maintenance of analgesia. Refer to Table 1 for a detailed breakdown of commonly used opioids by classification, route of administration, and clinical indications. Table 1: Commonly used opioids and their classification, indication, and administration Drug Efficacy Dosage for dogs Duration Morphine Excellent 0.1-0.2 mg/kg IM Up to 4 hours Hydromorphone Excellent 0.05-0.2 mg/kg IM Up to 6 hours Fentanyl Excellent 2-10 mg/kg IV Up to 1 hour Methadone Excellent 0.2-0.5 mg/kg IV, IM, SQ Up to 4 hours Buprenorphine Moderate to good 10-20 mg/kg IM Up to 6 hours Butorphanol Poor 0.2-0.4 mg/kg IM Up to 1.5 hours Drug Efficacy Dosage for cats Duration Morphine Excellent 0.1-0.2 mg/kg IM Up to 4 hours Hydromorphone Excellent 0.05-0.1 mg/kg IM Up to 6 hours Methadone Excellent 0.2-0.5 mg/kg IV, IM, SQ Up to 4 hours Buprenorphine Moderate to good 0.01-0.02 mg/kg IM** Up to 6 hours Butorphanol Poor 0.1-0.4 mg/kg IM Up to 45 minutes *Always use a dosing regimen and opioid that you feel comfortable with. **The author recommends the use of Simbadol, a concentrated buprenorphine product that is given subcutaneously. Morphine Morphine is the prototypical opioid against which other opioids are measured. It is extremely safe, with minimal cardiovascular and respiratory effects. As a full agonist, it is reversible. Morphine can cause a decrease in GI motility, which should not be of clinical importance when used short-term, such as for surgery. It also causes vomiting, especially in those patients that receive it prior to surgery. Morphine can be given subcutaneously, intramuscularly, or very slowly intravenously to avoid histamine release. It has a rapid onset of action, occurring within three to five minutes, and provides analgesia for two to four hours. Note: Morphine is potentially less effective in cats than it is in dogs, as cats only benefit from the parent drug but cannot make the intermediate metabolite. Hydromorphone It is very similar to morphine in terms of onset and duration. All opioids can cause hyperthermia; however, it has been implicated, maybe wrongly, to be more severe in cats. One study showed all opioids tested caused a mild increase in body temperature.6 This is usually a self-limiting issue and may also be more closely associated with post-emergent dysphoria following sedation or general anesthesia. Methadone Very similar to morphine but also has some N-methyl-D-aspartate (NMDA) antagonist activity. Methadone causes little nausea and is less likely to cause dysphoria compared to other full agonists. Fentanyl A very potent opioid given intravenously as either a constant rate infusion or as a bolus. It has a rapid onset of action, typically occurring within two to five minutes. It is less likely to cause GI effects or dysphoria compared to the other full agonists. Buprenorphine This has moderate potency compared to the full agonists, so consideration must be given for the surgical procedure to be performed. It has a long onset of action, as much as 30 minutes, but also has a long duration of action, typically in the six- to eight-hour range. Given to cats as the concentrated form of Simbadol, it can provide analgesia for 24 hours. Butorphanol This agonist-antagonist is moderately potent, with an onset of action of one to five minutes when administered IV or IM. However, it has a short duration of action, ranging from 45 minutes. It has an excellent sedative effect, which can last several hours. This sedative effect is often confused with the much shorter analgesic effect. Alpha-2 Agonists Alpha-2 agonists—primarily dexmedetomidine, medetomidine, and xylazine—are sedative-analgesic agents commonly used in veterinary practice. Their mechanism of action involves stimulation of central α₂-adrenoceptors, resulting in sedation, analgesia, and muscle relaxation, as well as dose-sparing effects on other anesthetic agents. Dexmedetomidine is the most commonly used alpha-2 agonist due to its higher receptor selectivity and favorable pharmacodynamic profile. Clinical use of alpha-2 agonists: As premedication in balanced anesthesia protocols For sedation when combined with other agents (e.g. opioids, ketamine) Occasionally, as part of multimodal analgesia during painful procedures or in recovery. Note: Atipamezole is a specific antagonist and should always be available when using this class of drugs When combined with opioids, the recommended dose of dexmedetomidine is 0.5–2 µg/kg IM. Always dose based on lean body mass, not total weight. Special considerations when using alpha-2 in geriatric or compromised patients: Due to age-related reductions in cardiac output, vascular compliance, and organ perfusion, alpha-2 agonists must be used with extreme caution in geriatric animals. Avoid their use as a stand-alone sedative in older patients. Instead, consider combining with opioids for pre-anesthesia or combining with ketamine and opioids for procedural sedation. See Table 2 for a list of common contraindications. Table 2: Common contraindications for using alpha-2 adrenergic Absolute contraindications • Cardiovascular disease • Congestive heart failure • Dilated cardiomyopathy • Heart block • Poor cardiac output • Significant bradycardia Use with caution • Liver disease because they are metabolized hepatically • Diabetes, as they can inhibit insulin release • Pregnancy, as uterine contraction might occur • Dogs and cats prone to seizures Advantages of using alpha-2 agonists include a rapid onset of action, reliable sedation and analgesia, reduced use of anesthetic agents, including inhalants, and the ability to offer reversible control over the duration of effect or in the event of an adverse event. The disadvantages of using alpha-2 agonists include emesis, muscle twitching and tremors, reflexive bradycardia due to increased central blood pressure, and reduced cardiac output. Ketamine Ketamine is a dissociative anesthetic widely used in veterinary medicine for induction, sedation, and analgesia. It functions primarily as an NMDA receptor antagonist, disrupting nociceptive signal transmission and preventing central sensitization. Ketamine is most effective when combined with other agents, such as opioids and alpha-2 agonists, particularly in multimodal analgesia protocols. Ketamine provides excellent somatic analgesia. However, it has poor visceral analgesia, making it a poor choice for intra-abdominal procedures. It also has the advantage of a rapid onset and a long duration of action. Its ability to maintain cardiovascular and respiratory function makes it a potential option for geriatric patients that do not have significant cardiovascular or respiratory disease. There are some disadvantages with ketamine, including hypersalivation, increased muscle tone resulting in a rigid appearance, lack of a blink response requiring ophthalmic lubrication, and rough recoveries when used as a sole agent. Patients may experience vocalization, tremors, or dysphoria. See Table 3 for a list of contraindications. Table 3: Contraindications for ketamine • Heart disease as it may increase heart rate, blood pressure and myocardial oxygen consumption Hypertrophic cardiomyopathy Valvular disease Arrhythmias Hypertrophic cardiomyopathy Valvular disease Dilated cardiomyopathy • Severe CNS disease or cranial trauma as it may increase intracranial hypertension • Glaucoma, as it can increase intraocular pressure • Advanced liver and kidney disease as they can impair clearance Non-steroidal anti-inflammatory drugs (NSAIDs) NSAIDs should be considered for use in managing pain in geriatric dogs and cats, but only if there are no contraindications for use, such as poor renal function, GI disease, or others. Always consider COX-2 NSAIDs, such as carprofen or meloxicam, as they have fewer GI and renal side effects, and as such, may be considered safer in geriatric patients. It is advisable not to administer NSAIDs preoperatively unless there are provisions for closely monitoring for a drop in blood pressure, and the attending veterinary staff have the necessary pharmaceuticals and skill set to respond appropriately to a blood pressure drop. Many veterinarians prefer to start NSAIDs during the immediate post-anesthetic recovery. Local anesthetics Local anesthetics can and should be used whenever possible. As the only true analgesic, it can have a profound effect on patient comfort, as well as safety, as the use of local anesthetics will reduce the need and dosage of other analgesics. There are no contraindications specific to geriatric patients. The usual precautions of dose and route of administration are the same across all age groups. Non-pharmaceutical considerations Geriatric pets may become disoriented in the unfamiliar surroundings of a veterinary hospital. This can interfere with both eating and sleeping, which have been shown to impact recovery in all age groups, but is decidedly a more important consideration in geriatrics that may have comorbidities. It is essential that we consider the factors that impact sleep7 and nutrition.8 Hospitalization can be especially stressful for geriatric animals. Take the time to comfort them throughout their stay. Photo courtesy Dr. Michael C. Petty As mentioned earlier, many of these elderly patients have a reduced physiological reserve. Providing them with comfortable settings, gentle handling, comforting interactions with the veterinary staff, and minimizing hospitalization time can decrease unwanted issues related to morbidity and mortality. Michael C. Petty, DVM, is a veterinary school graduate from Michigan State University. Dr. Petty has devoted his professional life to the care and well-being of animals, especially in pain management. Petty is the past president of the International Veterinary Academy of Pain Management and current World Small Animal Association Pain Council member. A frequent speaker and consultant, he has published articles in veterinary journals and serves in an advisory capacity to several pharmaceutical companies on pain management topics. Petty has been the investigator/veterinarian in 12 FDA pilot and pivotal studies for pain management products. He has lectured both nationally and internationally on pain management topics. References Dodman NH, Seeler DC, Court MH. Aging changes in the geriatric dog and their impact on anesthesia. Compendium on Continuing Education for the Practicing Veterinarian. 1984;6:1106–1113. Muravchick S. The aging process: anesthetic implications. Acta anaesthesiologica Belgica. 1998;49:85–90. Conzen P, Peter K. Inhalation anaesthesia at the extremes of age: geriatric anaesthesia. Anaesthesia. 1995;50(Suppl):29–33. doi: 10.1111/j.1365-2044.1995.tb06187.x. Hughes J. Anaesthesia for the geriatric dog and cat. Ir Vet J. 2008 Jun 1;61(6):380-7 Hansen B. Acute Pain Management. Veterinary Clinics of NA, Small Animal. K Mathews, ed. 2000;4:899‐916. Posner LP, et al. Vet Anaesth Analg. 2010;37(1):35-43. Emma A. Devereux, Alana V. Ejezie, Alex M. Lynch, Margaret E. Gruen, Stefanie J. LaJuett, James B. Robertson, Valery F. Scharf Factors Affecting Sleep Among Dogs and Cats in a Veterinary Intensive Care Unit, Journal of Veterinary Emergency and Critical Care: 2025;Volume 35, Issue 3:252-232 Collins, S. (2016). The importance of nutrition in the post-operative recovery of cats and dogs. Veterinary Nursing Journal, 31(8), 233–236. https://doi.org/10.1080/17415349.2016.1194637
