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Biomedical subjects

S M Hartsfield

Publications and source records attributed to S M Hartsfield.

At least 19 recordsLinked to original sources
PubMed2001

Pharmacokinetics and pharmacodynamics of butorphanol in llamas after intravenous and intramuscular administration.

OBJECTIVE: To evaluate disposition of butorphanol after i.v. and i.m. administration, effects on physiologic variables, and analgesic efficacy after i.m. administration in llamas. DESIGN: Nonrandomized crossover study. ANIMALS: 6 healthy adult male llamas. PROCEDURE: Butorphanol (0.1 mg/kg [0.045 mg/lb] of body weight) was administered i.m. first and i.v. 1 month later. Blood samples were collected intermittently for 24 hours after administration. Plasma butorphanol versus time curves were subjected to pharmacokinetic analysis. Two months later, butorphanol (0.1 mg/kg) was administered i.m., and physiologic variables and analgesia were assessed. RESULTS: Extrapolated peak plasma concentrations after i.v. and i.m. administration were 94.8 +/- 53.1 and 34.3 +/- 11.6 ng/ml, respectively. Volume of distribution at steady state after i.v. administration was 0.822 +/- 0.329 L/kg per minute and systemic clearance was 0.050 +/- 0.014 L/kg per minute. Slope of the elimination phase was significantly different, and elimination half-life was significantly shorter after i.v. (15.9 +/- 9.1 minutes) versus i.m. (66.8 +/- 13.5 minutes) administration. Bioavailability was 110 +/- 49% after i.m. administration. Heart rate decreased and rectal temperature increased. Somatic analgesia was increased for various periods. Two llamas became transiently sedated, and 2 became transiently excited after butorphanol administration. CONCLUSIONS AND CLINICAL RELEVANCE: Although i.v. administration of butorphanol results in a short half-life that may limit its analgesic usefulness, the elimination half-life of butorphanol administered i.m. is likely to be clinically useful. The relationship among plasma butorphanol concentration, time, and analgesia differed with the somatic analgesia model; clinically useful analgesia may occur at lower plasma concentrations than those reported here.

Analgesics, Opioid↗
PubMed1999

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.

Anesthesia, Inhalation↗
PubMed1999

Pharmacokinetics of fentanyl after intravenous and transdermal administration in goats.

OBJECTIVE: To evaluate disposition of fentanyl in goats after IV and transdermal administration. ANIMALS: 8 healthy 2-year-old goats weighing 31.8 to 53.6 kg (mean+/-SD, 40.4+/-7.5 kg). PROCEDURE: Each goat was given 2 treatments consisting of fentanyl administered IV (2.5 microg/kg of body weight) and via a transdermal patch (50 microg/h). There was a 2-month interval between treatments. Blood samples were collected at specified times and analyzed in duplicate to determine plasma fentanyl concentrations. Pharmacokinetic values were calculated, using a computerized modeling program. RESULTS: Administration of fentanyl was tolerated by all goats. Intravenous administration of fentanyl resulted in a transitory increase in rectal temperature that was not clinically important. Terminal elimination half-life after IV administration was 1.20+/-0.78 h, volume of distribution at steady state was 1.51+/-0.39 L/kg, and systemic clearance was 2.09+/-0.62 L/kg/h. Transdermal administration of fentanyl resulted in variable plasma concentrations, with peak plasma concentrations ranging from 1.12 to 16.69 ng/ml (mean+/-SD, 6.99+/-6.03 ng/ml) and time to peak concentration ranging from 8 to 18 hours (mean+/-SD, 13+/-4.5 hours). After removal of the transdermal patch, mean+/-SD terminal elimination half-life was 5.34+/-5.34 hours. CONCLUSIONS AND CLINICAL RELEVANCE: Intravenous administration of fentanyl (2.5 microg/kg) in goats results in a relatively short half-life that will limit its use for management of pain. Transdermal administration of fentanyl (50 microg/h) in goats results in variable plasma concentrations that may exceed those anticipated on the basis of a theoretical delivery rate, but stable plasma concentrations of fentanyl may not be achieved.

Administration, Cutaneous↗
PubMed1998

Evaluation of analgesia provided by postoperative administration of butorphanol to cats undergoing onychectomy.

OBJECTIVE: To evaluate adequacy of analgesia provided by postoperative administration of butorphanol to cats undergoing onychectomy. DESIGN: Randomized controlled trial. ANIMALS: 63 cats undergoing elective onychectomy. PROCEDURE: Cats were randomly assigned to a treatment (n = 42) or control group (21). Cats in the treatment group were given butorphanol parenterally immediately and 4 hours after surgery and orally for 2 days after surgery. Rectal temperature, heart rate, and respiratory rate were recorded and scores were assigned for temperament, recovery, sedation, analgesia, and lameness for the first 24 hours after surgery. Owners provided scores for appetite, personality, and lameness the first and second days after discharge from the hospital. RESULTS: Heart rate, respiratory rate, rectal temperature, and temperament and sedation scores were not significantly different between groups at any evaluation time. Recovery scores were significantly better for butorphanol-treated than for control-group cats 10 minutes after extubation. Analgesia scores were significantly better for butorphanol-treated than for control-group cats between 5 and 24 hours after surgery. Fewer butorphanol-treated than control-group cats were lame at the time of discharge from the hospital. The first day after discharge, owners reported that percentages of butorphanol-treated cats that ate normally, acted normally, and had only mild or no lameness were significantly higher than percentages of control-group cats that did. Significant differences between groups were not detected the second day after discharge. CLINICAL IMPLICATIONS: Results suggest that for cats undergoing onychectomy, administration of butorphanol the day of surgery and the first full day after surgery provides effective analgesia and improves recovery, appetite, and gait.

Analgesia↗
PubMed1998

Maintenance of anaesthesia with sevoflurane and oxygen in mechanically-ventilated horses subjected to exploratory laparotomy treated with intra- and post operative anaesthetic adjuncts.

Eight healthy horses premedicated with xylazine and induced with ketamine were used to evaluate sevoflurane in oxygen for maintenance of anaesthesia during elective exploratory laparotomy. After orotracheal intubation, horses were hoisted, placed in dorsal recumbency on a padded surgery table, and received sevoflurane in oxygen for maintenance of anaesthesia. The horses were allowed to breathe spontaneously until instrumented; then, they were mechanically ventilated to maintain the PaCO2 between 35 and 45 mmHg. Systolic (SAP), diastolic (DAP), and mean (MAP) arterial blood pressures, heart rate (HR), ECG, respiratory rate, an estimation of the saturation of haemoglobin with oxygen in peripheral arterial blood (S(p)O2), nasal temperature, end-tidal CO2(ET(CO2)), end-tidal sevoflurane (ET(SEVO)), and vaporiser concentration were recorded every 5 min post induction; arterial blood samples were obtained soon after induction, at 30 min after induction, and every hour thereafter until surgery was completed. Recovery data including times from the sevoflurane vaporiser being turned off to first movement, to sternal recumbency, and to standing, number of attempts to stand, and recovery score (between 1 = safe, smooth and 6 = stormy, major injury to horse) were collected. Analysis of variance was performed using physiological data collected over 195 min of anaesthesia, the longest time period during which all 8 horses were instrumented. Time effects (P<0.05) for HR, SAP, DAP, MAP, and nasal temperature were identified. Heart rate peaked at 45 min and declined over the course of the procedure. Arterial blood pressure generally decreased over time. Body temperature decreased over time. From 15 to 195 min mean ET(SEVO)concentration ranged from 2.0 to 3.3%, while mean vaporiser settings ranged from 3.7 to 5.5%. Three horses received intra-operative ketamine; all horses received dobutamine infusions; and 2 horses received intra-operative calcium-dextrose. Total anaesthesia time was 222-316 min (mean+/-s.d.269+/-31 min). Time from turning the sevoflurane vaporiser off to first movement was mean +/-s.d.18+/-15 min; to sternal recumbency was 54+/-22 min; to standing was 65+/-27 min; and to returning the horse to the stall in the ward was 78+/-24 min. Six horses stood on the first attempt; 2 horses stood on the second attempt. The median recovery score was one (1-3). In conclusion, sevoflurane provided a stable, easily controllable anaesthetic plane during prolonged exploratory laparotomies; horses experienced smooth, safe recoveries after maintenance of anaesthesia with sevoflurane following routine anaesthetic induction and post operative xyalzine administration.

Adjuvants, Anesthesia↗
PubMed1998

Idiopathic distal esophageal dilation in a southern black rhinoceros (Diceros bicornis minor).

An adult female southern black rhinoceros (Diceros bicornis minor) experienced intermittent periods of regurgitation while eating, suggesting an esophageal disorder. Endoscopy for evaluation of the trachea, esophagus, and stomach revealed a 30-mm nasopharyngeal orifice with associated recess located in the caudodorsal pharynx and a 10-cm dilated segment of the distal esophagus that was presumably the cause of regurgitation. Dietary management of esophageal dilation through short-term utilization of a "soft feed" program successfully eliminated the regurgitation. This is the first report of esophageal dysfunction in a rhinoceros.

Animals↗
PubMed1997

Anesthetic effects of tiletamine-zolazepam, alone or in combination with butorphanol, in goats.

OBJECTIVE: To evaluate anesthetic effects of tiletamine-zolazepam (TZ), alone or in combination with butorphanol, in goats undergoing laparotomy for embryo collection. DESIGN: Randomized clinical trial with crossover design. ANIMALS: 9 adult female goats. PROCEDURE: Goats were anesthetized twice: once with TZ (5.5 mg/kg [2.5 mg/lb] of body weight, i.v.) and once with tiletamine-zolazepam and butorphanol (0.1 mg/kg [0.045 mg/lb], i.v.). Additional doses of TZ (0.5 to 1.0 mg/kg [0.23 to 0.45 mg/lb], i.v.] were administered as needed to maintain a surgical anesthetic plane. Time to sternal recumbency was recorded, and quality of induction was scored. Arterial pressures, heart rate, respiratory rate, and rectal temperature were recorded every 5 minutes; arterial blood samples were collected every 30 minutes. Oxygen was insufflated if estimated saturation of hemoglobin in peripheral arterial blood with oxygen was < 90%; intermittent positive-pressure ventilation was performed if goats became apneic. Muscle relaxation, quality of anesthesia, and eye signs were scored every 15 minutes during anesthesia. Anesthesia time was recorded, and quality of recovery and degree of postoperative analgesia were scored. Plasma cortiso concentration was measured before induction, immediately after extubation, and 2 hours after extubation. RESULTS: Induction was rapid and smooth. Five goats regurgitated, 3 required supplemental oxygen, and 1 required intermittent positive-pressure ventilation, but none of the goats became hypotensive. Muscle relaxation and quality of anesthesia were adequate. Goats recovered from anesthesia without complications. We did not detect any significant differences between anesthetic regimens for any of the variables measured, except bicarbonate concentration and base excess. CLINICAL IMPLICATIONS: TZ at a dose of 5.5 mg/kg was satisfactory for anesthetic induction in goats; additional doses can be given to extend anesthesia time, but addition of butorphanol at a dose of 0.1 mg/kg to this regimen does not seem to provide any measurable benefit. An oxygen source and a means of assisting ventilation should be available.

Analgesics, Opioid↗
PubMed1997

Cardiovascular effects of buprenorphine in anesthetized dogs.

OBJECTIVE: To determine the cardiovascular effects of buprenorphine in isoflurane- and halothane-anesthetized dogs. ANIMALS: 6 healthy adult hound-type dogs given buprenorphine (16 micrograms/kg of body weight, i.v.) or isovolumetric 5% dextrose solution during anesthesia with isoflurane or halothane. PROCEDURE: Each dog was anesthetized 4 times, with a minimum of 10 days between episodes. Anesthesia was induced with isoflurane or halothane in O2 by mask, and was maintained with 1.9% isoflurane or 1.3% halothane (end-tidal concentration). The PaCO2 was maintained between 35 and 45 mm of Hg by use of mechanical ventilation, and the following variables were determined: systolic, diastolic, and mean arterial blood pressures; cardiac output; cardiac index; stroke volume; heart rate; systemic vascular resistance; mean pulmonary arterial pressure; and pulmonary vascular resistance. In addition, arterial blood samples for gas and acid-base analyses were collected at 30-minute intervals for 2.5 hours. After baseline values were recorded, dogs were randomly assigned to receive either buprenorphine (16 micrograms/kg, i.v.) or isovolumetric 5% dextrose solution. All variables were then recorded at 15-minute intervals for 2.5 hours. RESULTS: During isoflurane anesthesia, buprenorphine administration caused significant (P < or = 0.05) reductions in diastolic arterial pressure, mean arterial pressure, systolic arterial pressure, cardiac index, and heart rate, whereas systemic vascular resistance increased significantly. During halothane anesthesia, buprenorphine administration caused significant decreases in heart rate, cardiac index, mean, systolic and diastolic arterial blood pressures, and stroke volume, whereas pulmonary arterial blood pressure and systemic vascular resistance increased significantly. CONCLUSION: Although the changes seen were significant, they were not sufficiently large to be of clinical importance in healthy dogs.

Analgesics, Opioid↗
PubMed1997

Effects of high-dose gentamicin sulfate on neuromuscular blockade in halothane-anesthetized horses.

OBJECTIVE: To evaluate effects of a single high dose of gentamicin on neuromuscular function in horses anesthetized with halothane. ANIMALS: 6 healthy adult horses. PROCEDURE: Halothane-anesthetized horses were positioned in left lateral recumbency, and the right hind limb was immobilized in a reusable fiberglass cast fixed to a steel frame. The hoof was attached to a force transducer, and resting tension of 0.93 +/- 0.16 kg was maintained. A supramaximal train-of-four stimulus of 2 Hz for a duration of 0.25 millisecond was applied to the superficial peroneal nerve every 20 seconds by a square-wave stimulator. The force of the evoked digital extensor tension was recorded to determine first muscle twitch tension, compared with the baseline value (T1%) and the ratio of the force of the fourth twitch to the first twitch (T4/T1). Data were recorded at 5, 10, 15, 30, and 60 minutes after i.v. administration of vehicle or gentamicin (6 mg/kg of body weight). RESULTS: There was a significant (P = 0.04) treatment-time interaction for the effect of gentamicin on T1%; T1% associated with vehicle decreased from 100% to 92% during the 60- minute study period, but no decrease was associated with gentamicin. For T4/T1, there was no significant effect of treatment or time or treatment-time interaction between gentamicin and vehicle. CONCLUSIONS: Gentamicin did not cause a decrease in initial muscular strength, nor did it impair the muscles' ability to sustain strength. CLINICAL RELEVANCE: A single high dose of gentamicin does not cause significant neuromuscular blockade when administered alone to healthy horses anesthetized with halothane.

Analysis of Variance↗
PubMed1996

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.

Analgesia↗
PubMed1996

Pharmacokinetics, effects on renal function, and potentiation of atracurium-induced neuromuscular blockade after administration of a high dose of gentamicin in isoflurane-anesthetized dogs.

OBJECTIVE: To determine pharmacokinetics, renal effects, and effect on atracurium-induced neuromuscular blockade of a high dose of gentamicin in isoflurane-anesthetized dogs. ANIMALS: 6 healthy, adult, mixed-breed dogs, anesthetized twice and receiving gentamicin (6 mg/kg of body weight, i.v.) or saline solution. PROCEDURE: Blood samples were collected before and at intervals after gentamicin administration. Pharmacokinetic values were evaluated by use of multivariant stepwise linear regression analysis. Gentamicin-induced renal changes were assessed by comparing pretreatment and 12- to 24-hour posttreatment values for serum urea nitrogen, serum creatinine, urine creatinine-to-gamma-glutamyl-transferase ratio, and urinalysis. Neuromuscular blockade, maintained by atracurium infusion, was assessed, using the train-of-four response. At stable 50% depression of first twitch (T1), gentamicin or saline solution was given. Before and at posttreatment intervals for 60 minutes, T1% and fourth twitch-to-T1 ratio were recorded. The infusion was discontinued and 50 to 75% T1 recovery time was recorded. At 75% T1, edrophonium (0.5 mg/kg) was administered i.v.. RESULTS: Mean values for volume of distribution and clearance were 0.263 L/kg and 2.0 ml/min/kg, respectively. Mean maximal serum concentration of gentamicin was 46.4 micrograms/ml. Pre and posttreatment values for serum urea nitrogen, serum creatinine, urine creatinine-to-gamma-glutamyltransferase ratio, and other urine analytes were not significantly different. Mean (+/- SD) values for T1% and fourth twitch-to-T1 ratio decreased significantly after gentamicin (depression was maximal at 5 minutes). Recovery time (50 to 75% T1) was not different between groups. Edrophonium restored twitch to baseline. CONCLUSIONS: Mean values for apparent volume of distribution and total body clearance of gentamicin were similar to values in unanesthetized dogs. Mean maximal serum concentration of gentamicin was greater than that in unanesthetized dogs. Renal function was unaffected. Gentamicin potentiated atracurium-induced neuromuscular blockade, but did not affect recovery time.

Anesthesia↗
PubMed1994

Evaluation of pulse oximetry in horses surgically treated for colic.

All 43 horses anaesthetised for colic surgery were premedicated with xylazine or diazepam. Anaesthesia was induced with guaifenesin and ketamine, horses were placed in dorsal recumbency and anaesthesia was maintained with isoflurane in oxygen and mechanical ventilation. Haemoglobin saturation readings (SpO2) were taken with a pulse oximeter and compared with computed haemoglobin saturation (SaO2) from arterial blood samples. Readings were taken over a range of SaO2 of 78-100%, mean arterial blood pressure ranged from 24 to 108 mmHg and PaO2 ranged from 53 to 490 mmHg. Analysis of 107 readings showed that SpO2 values predicted SaO2 but time, blood pressure and individual horse did not. Correlation coefficients between SpO2 and SaO2 were 0.85 for all values and 0.88 for values at 30 min. Values for bias and precision were calculated for all SpO2 values and for readings separated into 3 saturation groups: normal, low normal, and abnormal. The pulse oximeter tended to underestimate SaO2 at all times, and was less precise as the saturation decreased.

Analysis of Variance↗
PubMed1993

Pharmacokinetics of midazolam administered concurrently with ketamine after intravenous bolus or infusion in dogs.

Midazolam, a water-soluble benzodiazepine tranquilizer, has been considered by some veterinary anaesthesiologists to be suitable as a combination anaesthetic agent when administered concurrently with ketamine because of its water solubility and miscibility with ketamine. However, the pharmacokinetics of midazolam have not been extensively described in the dog. Twelve clinically healthy mixed breed dogs (22.2-33.4 kg) were divided into two groups at random and were administered ketamine (10 mg/kg) and midazolam (0.5 mg/kg) either as an intravenous bolus over 30 s (group 1) or as an i.v. infusion in 0.9% NaCl (2 ml/kg) over 15 min. Blood samples were obtained immediately before the drugs were injected and periodically for 6 h afterwards. Serum concentrations were determined using gas chromatography with electron-capture detection. Serum concentrations were best described using a two-compartment open model and indicated a t1/2-alpha of 1.8 min and t1/2-beta of 27.8 min after i.v. bolus, and t1/2-alpha of 1.35 min and t1/2-beta of 31.6 min after i.v. infusion. The calculated pharmacokinetic coefficient B was significantly smaller after i.v. infusion (429 +/- 244 ng/ml) than after i.v. bolus (888 +/- 130 ng/ml, P = 0.004). Furthermore, AUC was significantly smaller after i.v. infusion (29,800 +/- 6120 ng/h/ml) than after i.v. bolus (42,500 +/- 8460 ng/h/ml, P < 0.05), resulting in a larger ClB after i.v. infusion (17.4 +/- 4.00 ml/min/kg than after i.v. bolus (12.1 +/- 2.24 ml/min/kg, P < 0.05). No other pharmacokinetic value was significantly affected by rate of intravenous administration.

Anesthesia↗
PubMed1993

Cardiorespiratory effects of intravenous bolus administration and infusion of ketamine-midazolam in dogs.

Twelve healthy dogs were used to determine the cardiorespiratory effects of i.v. administered ketamine (10 mg/kg of body weight) and midazolam (0.5 mg/kg). Half the dogs received a ketamine-midazolam combination (K-M) as a bolus over 30 seconds and the other half received the K-M as an infusion over 15 minutes. Induction of anesthesia by use of K-M was good in all dogs. Ketamine-midazolam combination as a bolus or infusion induced minimal cardiorespiratory effects, except for significant (P < 0.05) increases in mean heart rate and rate-pressure product. The increase in heart rate was greater in dogs of the infusion group. Mild and transient respiratory depression was observed in dogs of both groups immediately after administration of K-M, but was greater in dogs of the bolus group than in dogs of the infusion group. Duration of action of K-M for chemical restraint was short. Salivation and defecation were observed in a few dogs. Extreme muscular tone developed in 1 dog after K-M bolus administration.

Administration, Oral↗