Sandee M. Hartsfield

General Anesthetic Techniques in Ruminants

Sedation, anesthesia, protection of the airway during general anesthesia, and control of pain in the perioperative period are important considerations in the management of sheep, goats, and cattle. Though ruminants are classically considered farm animals and are often intended for the production of food and fiber, these species are used extensively in research and teaching and they are increasingly important as companion animals. Whatever their use may be, anesthetic and analgesic drugs and techniques should be used to ensure minimal stress and discomfort during the perioperative period.

Advantages and Guidelines for Using Ketamine for Induction of Anesthesia

Ketamine in combination with a sedative or tranquilizer is a relatively safe and effective drug for intravenous induction of anesthesia in dogs and cats. If properly dosed, the combination can be used to induce anesthesia with minimal adverse cardiovascular effects, and it is a reasonable method for induction of anesthesia in patients with cardiac disease. If dosage is kept low, the rate of recovery is acceptable, and some of the drugs commonly used in the regimen with ketamine are reversible with appropriate antagonists.

Dose range finding study for the efficacy of meloxicam administered prior to sodium urate-induced synovitis in cats.

OBJECTIVE To determine the lowest efficacious dose of oral meloxicam for relieving pain in cats with a sodium urate (SU)-induced acute inflammatory synovitis. STUDY DESIGN Randomized, blinded, controlled, and four-way crossover study. ANIMALS Eight surgically neutered cats (four males, four females) paired according to sex. METHODS Each pair of cats was treated with 0 (placebo), 0.025, 0.05, or 0.075 mg kg(-1) oral meloxicam once daily for 4 days prior to injection, into alternating stifles, of 1 mL of 20 mg mL(-1) SU crystals, beginning with the right stifle. Each cat received each of the four treatments, separated by at least 21 days. Analgesic efficacy was evaluated based on objective (e.g., pressure mat data total force, contact pressure, and contact area) and subjective (e.g., scores for Analgesia Scale [AS], Lameness Scale [LS], and Visual Analog Scale [VAS]) outcome measures for pain assessment. All outcome measures were recorded before and during 30 hours after SU injection. The pre-defined primary outcome measure was the area under the response-time curve (AUC(0-30) hours) of the total force of the injected limb. Data were analyzed by analysis of variance. A sequential test procedure was applied and the test sequence stopped in case of a nonsignificant result. RESULTS Meloxicam at doses of 0.05 and 0.075 mg kg(-1) day(-1) PO was significantly different from placebo for the pre-defined primary outcome measure (i.e., AUC(0-30) hours of total force). All tested meloxicam doses were lower than placebo for the subjective outcome measures (i.e., AUC(0-30) hours of AS, LS, and VAS). CONCLUSIONS AND CLINICAL RELEVANCE The lowest efficacious dose of meloxicam for relieving pain in cats with an SU-induced synovitis was 0.05 mg kg(-1) day(-1) PO according to the pre-defined primary outcome measure. However, lower doses may also be effective as seen in the subjective outcome measures.

Pharmacokinetics and selected behavioral responses to butorphanol and its metabolites in goats following intravenous and intramuscular administration

OBJECTIVE To evaluate disposition of a single dose of butorphanol in goats after intravenous (IV) and intramuscular (IM) administration and to relate behavioral changes after butorphanol administration with plasma concentrations. DESIGN Randomized experimental study. ANIMALS Six healthy 3-year-old neutered goats (one male and five female) weighing 46.5 ± 10.5 kg (mean ± D). METHODS Goats were given IV and IM butorphanol (0.1 mg kg-1) using a randomized cross-over design with a 1-week interval between treatments. Heparinized blood samples were collected at fixed intervals for subsequent determination of plasma butorphanol concentrations using an enzyme linked immunosorbent assay (ELISA). Pharmacokinetic values (volume of distribution at steady state [VdSS], systemic clearance [ClTB], extrapolated peak plasma concentration [C0] or estimated peak plasma concentration [CMAX], time to estimated peak plasma concentration [TMAX], distribution and elimination half-lives [t1/2], and bioavailability) were calculated. Behavior was subjectively scored. A two-tailed paired t-test was used to compare the elimination half-lives after IV and IM administration. Behavioral scores are reported as median (range). A Friedman Rank Sums test adjusted for ties was used to analyze the behavioral scores. A logit model was used to determine the effect of time and concentration on behavior. A value of p < 0.05 was considered significant. RESULTS Volume of distribution at steady state after IV administration of butorphanol was 1.27 ± 0.73 L kg-1, and ClTB was 0.0096 ± 0.0024 L kg-1 minute-1. Extrapolated C0 of butorphanol after IV administration was 146.5 ± 49.8 ng mL-1. Estimated CMAX after IM administration of butorphanol was 54.98 ± 14.60 ng mL-1, and TMAX was 16.2 ± 5.2 minutes; bioavailability was 82 ± 41%. Elimination half-life of butorphanol was 1.87 ± 1.49 and 2.75 ± 1.93 hours for IV and IM administration, respectively. Goats became hyperactive after butorphanol administration within the first 5 minutes after administration. Behavioral scores for goats were significantly different from baseline at 15 minutes after IV administration and at 15 and 30 minutes after IM administration. Both time and plasma butorphanol concentration were predictors of behavior. Behavioral scores of all goats had returned to baseline by 120 minutes after IV administration and by 240 minutes after IM administration. Conclusions and Clinical Relevance  The dose of butorphanol (0.1 mg kg-1, IV or IM) being used clinically to treat postoperative pain in goats has an elimination half-life of 1.87 and 2.75 hours, respectively. Nonpainful goats become transiently excited after IV and IM administration of butorphanol. Clinical trials to validate the efficacy of butorphanol as an analgesic in goats are needed.

Anesthetic Techniques in Poultry

Anesthesia may be required in various species of poultry to facilitate surgery, diagnostics, and research. Preanesthetic evaluation, careful anesthetic management, and proper supportive methods should be employed. Injectable regimens may be useful for some procedures, but inhalation methods are more appropriate for long periods of anesthesia. Intubation of the trachea and maintenance of ventilation are of particular importance in avian species. Monitoring and support should continue until recovery is complete.

Cardiac troponin I concentrations following medetomidine–butorphanol sedation in dogs

OBJECTIVE To evaluate the effect of medetomidine-butorphanol sedation on serum cardiac troponin I (cTnI) concentration, a marker of myocardial ischemia and injury, in healthy dogs undergoing pre-surgical radiographs for orthopedic procedures. STUDY DESIGN Prospective clinical study. ANIMALS Twenty client-owned dogs with no history of cardiac disease. METHODS Dogs were evaluated for pre-existing cardiac disease with electrocardiogram (ECG), noninvasive blood pressure and echocardiogram. Sedation was achieved using a combination of medetomidine (10 microg kg(-1)) and butorphanol (0.2 mg kg(-1)) intravenously. Blood pressure, heart rate and ECG were serially recorded throughout the duration of sedation. Serum cTnI concentration was measured at baseline and 6, 18, and 24-hours post-sedation. RESULTS Following administration of medetomidine and butorphanol, all dogs were adequately sedated for radiographs and had a decreased heart rate and increased diastolic blood pressure. Arrhythmias associated with increased parasympathetic tone occurred, including a sinus arrhythmia further characterized as a sinus bigeminy in 17 of the dogs. Serum cTnI was undetectable at all time points in all but three dogs. Two of the three dogs had a detectable concentration of cTnI at all time points measured, including prior to sedation. Only one of the two dogs had a cTnI concentration above the normal reference interval. The dogs that exhibited detectable cTnI had no significant difference in signalment, heart rate, blood pressure, or lactate concentration as compared to those with undetectable cTnI. CONCLUSIONS AND CLINICAL RELEVANCE Sedation with medetomidine and butorphanol had predictable cardiovascular effects including bradycardia, an increase in arterial blood pressure, and arrhythmias in apparently healthy dogs requiring radiographs for orthopedic injuries, but did not induce significant increases in serum cTnI concentration following the drug doses used in this study.

Equipment for Inhalant Anesthesia

When used properly, anesthesia machines, breathing systems, anesthesia ventilators, and ancillary equipment allow the safe and efficient use of the inhalant anesthetics. Several veterinary anesthesia machines and ventilators have been introduced over the last few years. This article includes a discussion of some of these new pieces of anesthesia equipment, with particular emphasis on changes and innovations in the design of the equipment. In addition, principles of use and care of various anesthetic equipment is included where appropriate.

Repeated injectable anesthesia in six horses for cobalt therapy

Little information exists about repeated injectable anesthesia in horses, therefore our purpose is to report the anesthetic method we used to facilitate clinical treatment. Between 1992 and 1999, we anesthetized 6 horses 12 times each at 2^3 day intervals, to allow cobalt therapy (CO) of their tumors. One horse received an additional 10 treatments (T). The ¢ve mares and one gelding (3 QH, 1 Paint, 1TB, 1grade) had a mean age of 927 years (mean 2 SD) and mean weight of 505254 kg. Horses were anesthetized with xylazine (X, 1.020.08mg kgÿ1) and tiletamine-zolazepam (TZ, 1.020.08mg kgÿ1) given IV. Butorphanol (B, 0.02620.01) was given with X, 12 times in one horse and11 times in two horses. A portable multifunction monitor was used to provide ECG, hemoglobin saturation and NIBP. Additional drugs (X, B or ketamine) were required to maintain immobility during transport from the CO room or when horses were repositioned for bilateralT (¢ve horses). No horse required additional drugs after the fourth T. Heart rates were always within normal range (30^45 beats minÿ1) and mean arterial blood pressures were elevated (85^140mmHg). Mean maintenance time (T plus transport time) was 3026minutes, while recovery time (when placed in recovery stall to standing) was 46216 minutes. Oxygen was nasally insu¥ated at 15 Lminÿ1 during T and in recovery. Recoveries were generally good and improved over the course of T. All horses lost weight duringT; meanweight loss was 27222 kg. Horses appeared to acclimatize to transport and treatment, as judged by the fact that lower X doses (10% decrease) or no additional drugs were required during treatment or transport after the ¢rst 3^4 treatments. In conclusion, all horses tolerated repeated anesthesia with injectable agents without apparent adverse side e¡ects.

Precautions When Using Enflurane

Enflurane offers few advantages over halothane, and it is more expensive than halothane. It causes greater cardiopulmonary depression and induces seizure activity. When economy and systemic effects are considered, enflurane offers no real benefits for veterinary anesthesia.