Thomas J Doherty Copyright (c) 2013 All rights reserved. http://works.bepress.com/thomas_doherty Recent documents in Thomas J Doherty en-us Sun, 05 May 2013 01:39:52 PDT 3600 Physiologic and antinociceptive effects following intramuscular administration of xylazine hydrochloride in combination with tiletamine-zolazepam in llamas http://works.bepress.com/thomas_doherty/34 http://works.bepress.com/thomas_doherty/34 Fri, 03 May 2013 06:46:38 PDT Objective-To evaluate antinociceptive and selected effects associated with IM administration of xylazine hydrochloride in combination with tiletamine-zolazepam in llamas. Animals-8 adult male llamas. Procedures-Each llama received tiletamine-zolazepam (2 mg/kg) combined with either xylazine (0.1, 0.2, or 0.4 mg/kg) or saline (0.9% NaCl) solution IM (treatments designated as TZ-Xy0.1, TZ-Xy0.2, TZ-Xy0.4, and TZ-Sal, respectively) at 1-week intervals. Selected cardiorespiratory variables were assessed during lateral recumbency and anesthesia, and recovery characteristics were recorded. Duration of antinociception was evaluated by clamping a claw every 5 minutes. Results-Interval between treatment administration and lateral recumbency for TZ-Xy0.4 was shorter than that for TZ-Xy0.1 or TZ-Sal. Mean ± SEM duration of antinociception was longer for TZ-Xy0.4 (51.3 ± 7. 0 minutes), compared with findings for TZ-Xy0.2 (31.9 ± 6.0 minutes), TZ-Xy0.1 (8.1 ± 4.0 minutes), and TZ-Sal (0.6 ± 0.6 minutes). Interval between treatment administration and standing was longer for TZ-Xy0.4 (112 ± 9 minutes) than it was for TZ-Xy0.2 (77 ± 9 minutes) or TZ-Sal (68 ± 9 minutes). Mean heart and respiratory rates during the first 30 minutes for TZ-Sal exceeded values for the other treatments. Administration of TZ-Xy0.2 and TZ-Xy0.4 resulted in Pao2 < 60 mm Hg at 5 minutes after llamas attained lateral recumbency, and values differed from TZ-Sal findings at 5, 10, and 15 minutes; Paco2 was greater for TZ-Xy0.2 and TZ-Xy0.4 than for TZ-Sal at 5, 10, 15, and 20 minutes. Conclusions and Clinical Relevance-Xylazine (0.2 and 0.4 mg/kg) increased the duration of antinociception in llamas anesthetized with tiletamine-zolazepam.

]]> R Seddighi et al. Effects of hyperbaric oxygen treatment on horses with experimentally induced endotoxemia http://works.bepress.com/thomas_doherty/33 http://works.bepress.com/thomas_doherty/33 Tue, 12 Feb 2013 08:55:31 PST OBJECTIVE: To determine the effectiveness of preinduction hyperbaric oxygen treatment (HBOT) in ameliorating signs of experimentally induced endotoxemia in horses. ANIMALS: 18 healthy adult horses. PROCEDURES: Horses were randomly assigned to 1 of 3 equal-sized treatment groups to receive normobaric ambient air and lipopolysaccharide (LPS), HBOT and LPS, or HBOT and physiologic saline (0.9% NaCl) solution. Horses were physically examined, and blood was obtained for a CBC and to determine concentration or activity of plasma tissue necrosis factor-α, blood lactate, and blood glucose before the horses were treated with HBOT and then intermittently for 6 hours after administration of LPS or physiologic saline solution. RESULTS: All LPS-treated horses developed signs and biochemical and hematologic changes consistent with endotoxemia. Treatment with HBOT significantly ameliorated the effect of LPS on clinical endotoxemia score but did not significantly improve other abnormalities associated with endotoxemia. CONCLUSIONS AND CLINICAL RELEVANCE: The protective effect of HBOT was minimal, and results did not support its use as a treatment for horses prior to development of endotoxemia.

]]> C Baumwart et al. Effect of nitrous oxide on the minimum alveolar concentration for sevoflurane and the minimum alveolar concentration derivatives that prevent motor movement and autonomic responses in dogs. http://works.bepress.com/thomas_doherty/32 http://works.bepress.com/thomas_doherty/32 Mon, 07 May 2012 02:47:39 PDT OBJECTIVE: To investigate the effects of the concurrent administration of 70% N(2)O on the minimum alveolar concentration (MAC) for sevoflurane in dogs, the MAC derivative that blocks motor movement (MAC(NM)), and the MAC derivative that blocks autonomic responses (MAC(BAR)). ANIMALS: 7 adult sexually intact male mixed-breed dogs. PROCEDURES: For each dog, anesthesia was induced with sevoflurane delivered via a face mask. Initially, the baseline MAC, MAC(NM), and MAC(BAR) for sevoflurane were determined by use of a noxious stimulus (50 V, 50 Hz, and 10 milliseconds) applied subcutaneously over a midulnar region. Nitrous oxide (70%) was added to the breathing circuit, and MAC, MAC(NM), and MAC(BAR) were determined again. Percentage changes from the respective baseline concentrations for MAC, MAC(NM)' and MAC(BAR) were calculated after the administration of N(2)O. RESULTS: Baseline median values for the MAC, MAC(NM), and MAC(BAR) for sevoflurane were 1.75%, 2.00%, and 2.50%, respectively. Addition of 70% N(2)O significantly decreased MAC, MAC(NM), and MAC(BAR) by 24.4%, 25.0%, and 35.2%, respectively, and these values did not differ significantly from each other. CONCLUSIONS AND CLINICAL RELEVANCE: Supplementation with 70% N(2)O caused a clinically important and significant decrease in the MAC, MAC(NM)' and MAC(BAR) for sevoflurane in dogs.

]]> Reza Seddighi DVM, MS, PhD, Dip ACVA, cVMA et al. Use of xylazine/ketamine or medetomidine combined with either ketamine, ketamine/butorphanol, or ketamine/telazol for immobilization of white-tailed deer (<em>Odocoileus virginianus</em>) http://works.bepress.com/thomas_doherty/30 http://works.bepress.com/thomas_doherty/30 Thu, 19 Jan 2012 07:46:26 PST We immobilized 18 captive, adult, female white-tailed deer (Odocoileus virginianus) with a combination of either 1) xylazine/ketamine (XK; 1.6+0.1 mg kg 1 xylazine and 7.8+0.3 mg kg 1 ketamine antagonized with 2.1+0.1 mg kg 1 tolazoline), 2) Medetomidine/Ketamine (MK; 0.075+0.01 mg kg 1 medetomidine and 2.1+0.2 mg kg 1 ketamine antagonized with 0.37+0.0 mg kg 1 atipamezole), 3) Medetomidine/Ketamine/Butorphanol (MKB; 0.072+0.01 mg kg 1 medetomidine, 2.1+0.2 mg kg 1 ketamine and 0.1+ 0.0 mg kg 1 butorphanol antagonized with 0.36+0.0 mg kg 1 atipamezole and 10.3+1.2 mg kg 1 naltrexone), 4) Medetomidine/Ketamine/Tiletamine-zolazepam-A (MKT-A; 0.063+0.0 mg kg 1 medetomidine, 0.9+0.1 mg kg 1 ketamine and 2.0+0.1 mg kg 1 tiletamine-zolazepam antagonized with 0.31+0.0 mg kg 1 atipamezole ), or 5) Medetomidine/Ketamine/Tiletamine-zolazepam-B (MKT-B; 0.067+0.0 mg kg 1 medetomidine, 1.4+0.1 mg kg 1 ketamine and 1.1+0.1 mg kg 1 tiletamine-zolazepam antagonized with 0.34+0.0 mg kg 1 atipamezole). We measured times from injection to first effect, sternal recumbency and lateral recumbency. We measured SpO2, heart rate, respiratory rate and body temperature of each deer at 20 and 40 min after lateral recumbency. Forty-five minutes after lateral recumbency, deer were given appropriate antagonist drugs (half i.v., half i.m.). All drug combinations except the XK dose produced lateral recumbency in the deer. Hyperthermia occurred in the XK, MKB and MK groups. The MKT-A and MKT-B treatments resulted in acceptable physiological parameters, rapid induction and quick recovery. Combining ketamine (for a relatively shorter recovery time), tiletamine-zolazepam (for rapid induction) and medetomidine (for synergistic effects and increased relaxation) may optimize induction and recovery times in white-tailed deer.

]]> Lisa I. Muller et al. Publications Pharmacokinetics of Intravenous and Intramuscular Tramadol in Llamas http://works.bepress.com/thomas_doherty/29 http://works.bepress.com/thomas_doherty/29 Thu, 19 Jan 2012 07:46:24 PST The purpose of this study was to determine the pharmacokinetics of tramadol and its metabolite M1 after intravenous and intramuscular administration to llamas. Tramadol, a centrally acting analgesic whose efficacy is a result of complex interactions between opiate, adrenergic and serotonin receptor systems, has been used clinically to treat moderate to severe pain in humans. The pharmacokinetic parameters of tramadol and M1 in plasma were examined following intravenous and intramuscular administration to six healthy male llamas. Tramadol half-life, volume of distribution at steady-state and clearance after intravenous administration were 2.12 ± 0.37 h, 4.02 ± 1.16 L/kg and 1728.73 ± 152.82 mL/h/kg, respectively. The bioavailability was 110 ± 21% and half-life 2.54 ± 0.31 h following intramuscular administration of tramadol. M1 had a half-life of 10.40 ± 2.90 h and 7.71 ± 0.54 h following intravenous and intramuscular administration of tramadol.

]]> Sherry Cox et al. Effects of a Concentrated Lidocaine Solution on the Acute Phase Stress Response to Dehorning in Dairy Calves http://works.bepress.com/thomas_doherty/28 http://works.bepress.com/thomas_doherty/28 Thu, 19 Jan 2012 07:46:22 PST The objective of this study was to more fully define the surgical stress response to dehorning by heat cauterization in dairy calves by measuring behavioral, hormonal, inflammatory, and immunological markers of stress and to determine whether a nerve block of the surgical site with a concentrated solution of lidocaine (5%) reduces the degree of stress. Thirty-two 10- to 12-wk-old female Holstein calves were randomly allotted to 1 of 4 treatments: 5% lidocaine followed by dehorning, 2% lidocaine followed by dehorning, saline followed by dehorning, or 5% lidocaine followed by sham dehorning. Plasma cortisol concentration was measured in blood samples collected via a jugular catheter at −0.5, 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 6, 9, 12, 24, 48, and 72h. Various other blood constituents were measured in samples collected at −0.5, 12, 24, 48, and 72h. Feeding, drinking, scratching, grooming, rubbing, licking, and inactivity behaviors were observed in the standing and recumbent positions using a 10-min scan sampling method analyzed on a time period and daily basis for 72h following the dehorning procedure. The frequency of vocalization, kicking, and lying in the chute during the dehorning procedure were also assessed. The overall plasma cortisol concentrations were higher in calves subjected to dehorning than in control calves. Compared with the control group, the saline-treated calves had a higher cortisol concentration at 30 and 60min postdehorning. Plasma cortisol concentrations were higher in all groups at 30min postdehorning than at other sampling times. The percentage of circulating neutrophils and the neutrophil:lymphocyte ratio were increased in the saline and 2% lidocaine group. Total plasma protein, fibrinogen, and α1-acid glycoprotein concentrations were similar among treatments. The behavioral response to dehorning, as manifested by kicking while in the chute, was greater in the saline and 2% lidocaine group than in the control or 5% lidocaine treatment groups. In the postdehorning period, the percentage of time calves spent performing various maintenance behaviors did not differ among treatments. Thus, injection of 5% lidocaine may not provide any added comfort after the dehorning but may decrease the overall stress response during the procedure.

]]> Thomas J. Doherty et al. The effect of midazolam on the end-tidal concentration of isoflurane necessary to prevent movement in dogs http://works.bepress.com/thomas_doherty/27 http://works.bepress.com/thomas_doherty/27 Thu, 19 Jan 2012 07:46:19 PST OBJECTIVE: To determine the possible additive effect of midazolam, a GABA(A) agonist, on the end-tidal concentration of isoflurane that prevents movement (MAC(NM) ) in response to noxious stimulation. STUDY DESIGN: Randomized cross-over experimental study. ANIMALS: Six healthy, adult intact male, mixed-breed dogs. METHODS: After baseline isoflurane MAC(NM) (MAC(NM-B) ) determination, midazolam was administered as a low (LDS), medium (MDS) or high (HDS) dose series of midazolam. Each series consisted of two dose levels, low and high. The LDS was a loading dose (Ld) of 0.2 mg kg(-1) and constant rate infusion (CRI) (2.5 μg kg(-1) minute(-1)) (LDL), followed by an Ld (0.4 mg kg(-1)) and CRI (5 μg kg(-1) minute(-1)) (LDH). The MDS was an Ld (0.8 mg kg(-1)) and CRI (10 μg kg(-1) minute(-1)) (MDL) followed by an Ld (1.6 mg kg(-1)) and CRI (20 μg kg(-1) minute(-1)) (MDH). The HDS was an Ld (3.2 mg kg(-1)) and CRI (40 μg kg(-1) minute(-1)) (HDL) followed by an Ld (6.4 mg kg(-1)) and CRI (80 μg kg(-1) minute(-1)) (HDH). MAC(NM) was re-determined after each dose in each series (MAC(NM-T)). RESULTS: The median MAC(NM-B) was 1.42. MAC(NM-B) did not differ among groups (p > 0.05). Percentage reduction in MAC(NM) was significantly less in the LDS (11 ± 5%) compared with MDS (30 ± 5%) and HDS (32 ± 5%). There was a weak correlation between the plasma midazolam concentration and percentage MAC(NM) reduction (r = 0.36). CONCLUSION AND CLINICAL RELEVANCE: Midazolam doses in the range of 10-80 μg kg(-1) minute(-1) significantly reduced the isoflurane MAC(NM) . However, doses greater than 10 μg kg(-1) minute(-1) did not further decrease MAC(NM) indicating a ceiling effect.

]]> Reza Seddighi et al. Manual of equine anaesthesia and analgesia http://works.bepress.com/thomas_doherty/31 http://works.bepress.com/thomas_doherty/31 Thu, 19 Jan 2012 07:44:38 PST Thomas J. Doherty et al. The effect of ketamine on the MACBAR of sevoflurane in dogs http://works.bepress.com/thomas_doherty/26 http://works.bepress.com/thomas_doherty/26 Mon, 29 Aug 2011 12:10:28 PDT METHODS: Dogs were anesthetized with sevoflurane on two occasions, 1 week apart, and baseline MAC(BAR) (B-MAC(BAR)) was determined on each occasion. MAC(BAR) was defined as the mean of the end-tidal sevoflurane concentrations that prevented and allowed an increase (≥15%) in heart rate or invasive mean arterial pressure in response to a noxious electrical stimulus (50 V, 50 Hz, 10 ms). Dogs then randomly received either a low-dose (LDS) or high-dose series (HDS) of ketamine, and treatment MAC(BAR) (T-MAC(BAR)) was determined. The LDS had an initial loading dose (LD) of 0.5 mg kg(-1) and constant rate infusion (CRI) at 6.25 μg kg(-1) minute(-1), followed, after T-MAC(BAR) determination, by a second LD (1 mg kg(-1)) and CRI (12.5 μg kg(-1) minute(-1)). The HDS had an initial LD (2 mg kg(-1)) and CRI (25 μg kg(-1) minute(-1)) followed by a second LD (3 mg kg(-1)) and CRI (50 μg kg(-1) minute(-1)). Data were analyzed with a mixed-model anova and are presented as LSM ± SEM. RESULTS: The B-MAC(BAR) was not significantly different between treatments. Ketamine at 12.5, 25, and 50 μg kg(-1) minute(-1) decreased sevoflurane MAC(BAR), and the maximal decrease (22%) occurred at 12.5 μg kg(-1) minute(-1). The percentage change in MAC(BAR) was not correlated with either the log plasma ketamine or norketamine concentration. CONCLUSIONS AND CLINICAL RELEVANCE: Ketamine at clinically relevant doses of 12.5, 25, and 50 μg kg(-1) minute(-1) decreased sevoflurane MAC(BAR), although the reduction was neither dose-dependent nor linear.

]]> Lyda Love et al. Yohimbine Ameliorates the Effects of Endotoxin on Gastric Emptying of the Liquid Marker Acetaminophen in Horses http://works.bepress.com/thomas_doherty/25 http://works.bepress.com/thomas_doherty/25 Fri, 05 Aug 2011 09:33:29 PDT The effect of yohimbine pretreatment on gastric emptying of a liquid marker in horses was evaluated by measuring serum concentrations of acetaminophen. Gastric emptying was determined in normal, fasted horses, in horses given endotoxin (E. coli 055 B5; 0.2 microg/kg) intravenously, and in horses given yohimbine (0.25 mg/kg, IV, over 30 minutes) plus endotoxin. Acetaminophen (20 mg/kg) was given by stomach tube 15 minutes after the endotoxin infusion. Blood samples for acetaminophen analysis were collected, and time to reach the peak serum concentration (Tmax), the maximum serum concentration (Cmax) and the area under the acetaminophen serum concentration versus time curve (AUC) were determined for each treatment group. Endotoxin significantly increased Tmax, indicating a profound delay in gastric emptying and yohimbine pretreatment significantly (P < or = 0.05) prevented this effect.

]]> S. D. Meisler et al. Iontophoresis of Dexamethasone-phosphate into the Equine Tibiotarsal Joint http://works.bepress.com/thomas_doherty/24 http://works.bepress.com/thomas_doherty/24 Fri, 05 Aug 2011 09:33:28 PDT In human rehabilitation medicine, dexamethasone-phosphate is theoretically iontophoresed to localized subcutaneous tissue where conversion to dexamethasone occurs. This delivery system has recently been introduced into veterinary medicine for the same purpose. However, the pharmacokinetic justification for parenteral delivery of this prodrug remains undocumented. Utilizing iontophoretic methods that are relevant to both human and veterinary clinical practice, the present investigation compared injection and iontophoresis of dexamethasone-phosphate into the equine tibiotarsal joint, also known as the tarsocrual joint. The tibiotarsal joints of seven horses were injected with 4 mL of 6 mg/mL dexamethasone-phosphate. With a similar drug concentration and over the same application site, six different horses underwent simultaneous cathodic iontophoresis (4 mA, 40 min) or passive application (0 mA, 40 min) on contralateral limbs. Following all applications, tibiotarsal joint synovium was collected. Local venous blood samples were also collected from the iontophoretic and passive application sites for analysis of plasma drug concentrations. Because of the potential for conversion of dexamethasone-phosphate to dexamethasone, an extraction and analysis protocol was developed for both chemicals. The technique demonstrated a linear range of detection (0.39–12 μg/mL) and a capability for measuring both chemicals in plasma and synovium. Conversion of dexamethasone-phosphate to dexamethasone occurred during synovial incubation (37 °C) and following freeze–thaw cycles. In contrast to the measurable synovial concentrations of dexamethasone-phosphate (2.3±0.96 mg/mL) and dexamethasone (0.27±0.07 mg/mL) following injection, neither drug was detected in the synovium or the local venous blood following iontophoretic or passive applications. In conclusion, these results do not confirm iontophoretic or passive delivery of measurable dexamethasone-phosphate into the tibiotarsal joint using current clinical methods.

]]> J. Blackford et al. Effects of Intramuscular Omeprazole on Gastric Acid Secretion in Horses over a Twenty-four Hour Period http://works.bepress.com/thomas_doherty/23 http://works.bepress.com/thomas_doherty/23 Fri, 05 Aug 2011 09:33:26 PDT The effect of intramuscular (i.m.) omeprazole (0.25 or 1.0 mg/kg bwt; LD and HD), respectively, on volume, total acid output (TAO) and pH of the gastric juice was studied during 24 h in 5 horses with a chronically implanted gastric cannula. Whether secretion in controls was basal or stimulated with pentagastrin (8 μg/kg bwt/h), volume (NS) and TAO (P<0.01, NS) gradually decreased and pH increased (P<0.05, NS).

Omeprazole significantly reduced the average basal TAO by 49 ± 6% (LD) and 88 ± 3% (HD) and the stimulated TAO by 64 ± 2% and 97 ± 1%. Basal pH in controls was 2.1–4.2 and after omeprazole treatment, pH 2.8–4.1 (LD) and 2.4–6.6 (HD). After stimulation, the corresponding pH values were 2.6–3.3, 3.9–4.9 and 5.4–7.2. The biological availability of omeprazole was 70–80%. Due to the simplicity of the administration technique and the higher biological availability, intramuscular administration may offer a practical and less expensive way of treating gastric ulcers in horses.

]]> A. Sandin et al. Effects of Orally Administered Enteric-coated Omeprazole on Gastric Secretion in Horses http://works.bepress.com/thomas_doherty/22 http://works.bepress.com/thomas_doherty/22 Fri, 05 Aug 2011 09:33:25 PDT F. M. Andrews et al. The Effect of Sedation on Gastric Emptying of a Liquid Marker in Ponies http://works.bepress.com/thomas_doherty/21 http://works.bepress.com/thomas_doherty/21 Fri, 05 Aug 2011 09:33:23 PDT Objective The effect of sedation on gastric emptying was evaluated in six ponies by monitoring serum concentrations of acetaminophen (AP) after intragastric administration.

Experimental Design Prospective randomized experimental study.

Animals Six adult ponies, 135 to 275 kg.

Methods Fifteen minutes after the intravenous administration of xylazine (1 mg/kg), butorphanol (0.05 mg/kg), acepromazine (0.05 mg/kg) or saline, ponies were given AP (20 mg/kg in 350 mL water) by stomach tube. Blood for AP analysis was collected at baseline and 15, 30, 45, 75, 90, 105, and 120 minutes after AP administration. The time (Tmax) to reach peak serum concentration (Cmax), and the area under the AP serum concentration versus time curve (AUC) were determined for each treatment group.

Results Tmax was 31 mins in the control group, and this increased significantly (P < .05) after sedation. Cmax decreased (P < .05) after xylazine administration, and AUC decreased (P < .05) after acepromazine.

Conclusions This study indicated that sedation has a significant effect on the gastric emptying rate of a liquid in ponies.

Clinical Relevance Although sedation produced a significant delay in gastric emptying, the influence was transient and unlikely to be of clinical significance in healthy ponies. However, the ability of these agents to slow gastric emptying should be considered in the surgical patient.

]]> Thomas J. Doherty et al. Metoclopramide Ameliorates the Effects of Endotoxin on Gastric Emptying of Acetaminophen in Horses http://works.bepress.com/thomas_doherty/20 http://works.bepress.com/thomas_doherty/20 Fri, 05 Aug 2011 09:33:22 PDT The effect of metoclopramide on gastric emptying of a liquid marker in horses was evaluated by measuring serum concentrations of acetaminophen. Gastric emptying was determined in normal, fasted horses (n = 7), horses given endotoxin intravenously (n = 7), and horses given intravenous metoclopramide plus endotoxin (n = 6). The mean time to reach maximum serum acetaminophen concentration (Tmax), the maximum serum concentration (Cmax), and the area under the serum acetaminophen concentration vs time curve (AUC) were compared among treatment groups. Endotoxin caused a profound delay in gastric emptying, and pretreatment with metoclopramide significantly (P < 0.05) ameliorated this effect.

]]> Thomas J. Doherty et al. Acetaminophen as a Marker of Gastric Emptying in Ponies http://works.bepress.com/thomas_doherty/19 http://works.bepress.com/thomas_doherty/19 Fri, 05 Aug 2011 09:33:20 PDT Gastric emptying was evaluated in ponies using the acetaminophen (AP) method. Fifteen minutes after i.v. administration of metoclopramide, erythromycin, yohimbine, atropine or saline, the ponies were given AP by stomach tube. Blood samples for AP analysis were collected at baseline and 15, 30, 45, 60, 75, 90, 105 and 120 min after AP administration. Time to reach peak serum concentration (Tmax), maximum serum concentration (Cmax) and area under the AP serum concentration vs. time curve (AUC) were determined for each treatment group.

In the control group, Tmax was 31 min and this decreased significantly (P<0.05) following the administration of metoclopramide. Atropine significantly increased Tmax and decreased Cmax and AUC. Yohimbine significantly increased AUC. Erythromycin did not significantly change any parameter.

This study indicates that acetaminophen can be used to evaluate gastric emptying in ponies. The method is easy to perform and is minimally invasive. Metoclopramide stimulated gastric emptying of liquid in healthy, fasting ponies. Atropine significantly delayed, while erythromycin had little effect on, gastric emptying. Yohimbine increased the cumulative absorption of AP.

]]> Thomas J. Doherty et al. Effect of Intravenous Lidocaine on Halothane Minimum Alveolar Concentration in Ponies http://works.bepress.com/thomas_doherty/18 http://works.bepress.com/thomas_doherty/18 Fri, 05 Aug 2011 09:33:19 PDT This study investigated the effect of lidocaine i.v. on halothane minimum alveolar concentration (MAC) in ponies. Six ponies were anaesthetised with thiopentone and succinylcholine, intubated and anaesthesia maintained with halothane. Ventilation was controlled and blood pressure maintained within clinically acceptable limits. Following a 2 h equilibration period, baseline halothane MAC was determined. The ponies were then given a loading dose of lidocaine (2.5 or 5 mg/kg bwt) or saline over 5 min, followed by a constant infusion of lidocaine (50 or 100 μg/kg/min, or saline, respectively). The halothane MAC was redetermined after a 60 min infusion of lidocaine or saline. The baseline halothane MAC for the control group was mean ± s.d. 0.94 ± 0.03%, and no significant decrease occurred following saline infusion. Lidocaine decreased halothane MAC in a dose-dependent fashion (r = 0.86; P<0.0003). The results indicate that i.v. lidocaine may have a role in equine anaesthesia.

]]> Thomas J. Doherty et al. Effect of Cisapride on Gastric Emptying in Horses Following Endotoxin Treatment http://works.bepress.com/thomas_doherty/17 http://works.bepress.com/thomas_doherty/17 Fri, 05 Aug 2011 09:33:17 PDT The effect of cisapride pretreatment on gastric emptying in horses was determined by measuring serum concentrations of acetaminophen, a drug known to be readily absorbed in the small intestine but not in the stomach. The time to reach maximum serum acetaminophen concentrations (Tmax), the maximum serum concentrations (Cmax) and the area under the serum acetaminophen concentration vs. time curves (AUC) were compared among treatment groups. In the first part of the study, the effect of orally administered cisapride (0.1, 0.2 and 0.4 mg/kg bwt) on gastric emptying was examined in 6 normal fasted horses. In the second part of the study, gastric emptying in horses given endotoxin i.v. (n = 6) was compared to those that received cisapride per os prior to administration of endotoxin (n = 6) and those that received neither compound (n = 6). Cisapride did not alter gastric emptying in normal horses. Endotoxin caused a profound delay in gastric emptying and pretreatment with cisapride significantly attenuated this effect. It is concluded that cisapride may be useful as a prophylactic measure when administered prior to the development of endotoxaemia

]]> N. Valk et al. Phenylbutazone Prevents the Endotoxin-induced Delay in Gastric Emptying in Horses http://works.bepress.com/thomas_doherty/16 http://works.bepress.com/thomas_doherty/16 Fri, 05 Aug 2011 09:33:15 PDT The effect of phenylbutazone on gastric emptying in horses was determined by measuring serum concentrations of acetaminophen. Gastric emptying was determined in normal fasted horses (n = 6), horses given endotoxin intravenously (n = 6), horses given intravenous phenylbutazone (n = 6), and horses given intravenous phenylbutazone plus endotoxin (n = 6). The mean time to reach maximum serum acetaminophen concentration (Tmax), the maximum serum concentration (Cmax), and the area under the serum acetaminophen concentration versus time curve (AUC) were compared among treatment groups. Phenylbutazone did not alter gastric emptying in normal horses. Endotoxin caused a profound delay in gastric emptying, and pretreatment with phenylbutazone abolished this effect.

]]> N. Valk et al. Comparison of Halothane Minimum Alveolar Concentration and Minimum Effective Concentration in Ponies http://works.bepress.com/thomas_doherty/15 http://works.bepress.com/thomas_doherty/15 Fri, 05 Aug 2011 09:33:14 PDT Thomas J. Doherty et al.