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- Author or Editor: Thomas J. Doherty x
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Abstract
OBJECTIVE To evaluate agreement among diplomates of the American College of Veterinary Anesthesia and Analgesia for scores determined by use of a simple descriptive scale (SDS) or a composite grading scale (CGS) for quality of recovery of horses from anesthesia and to investigate use of 3-axis accelerometry (3AA) for objective evaluation of recovery.
ANIMALS 12 healthy adult horses.
PROCEDURES Horses were fitted with a 3AA device and then were anesthetized. Eight diplomates evaluated recovery by use of an SDS, and 7 other diplomates evaluated recovery by use of a CGS. Agreement was tested with κ and AC1 statistics for the SDS and an ANOVA for the CGS. A library of mathematical models was used to map 3AA data against CGS scores.
RESULTS Agreement among diplomates using the SDS was slight (κ = 0.19; AC1 = 0.22). The CGS scores differed significantly among diplomates. Best fit of 3AA data against CGS scores yielded the following equation: RS = 9.998 × SG0.633 × ∑UG0.174, where RS is a horse's recovery score determined with 3AA, SG is acceleration of the successful attempt to stand, and ∑UG is the sum of accelerations of unsuccessful attempts to stand.
CONCLUSIONS AND CLINICAL RELEVANCE Subjective scoring of recovery of horses from anesthesia resulted in poor agreement among diplomates. Subjective scoring may lead to differences in conclusions about recovery quality; thus, there is a need for an objective scoring method. The 3AA system removed subjective bias in evaluations of recovery of horses and warrants further study.
Abstract
OBJECTIVE
To determine whether palmar digital nerve (PDN) blockade in horses with a combination of dexmedetomidine and mepivacaine would block the response to mechanical force applied to the digit longer than would anesthetizing these nerves with mepivacaine alone or dexmedetomidine alone.
ANIMALS
8 mares with no signs of lameness.
PROCEDURES
In a randomized, crossover, blinded, experimental study, both PDNs of the same forelimb of each horse were anesthetized by perineural injection with either 30 mg mepivacaine alone, 250 µg of dexmedetomidine alone, or 30 mg mepivacaine combined with 250 µg of dexmedetomidine. Each horse received each treatment, and treatments were administered ≥ 2 weeks apart. The mechanical nociceptive threshold was measured at a region between the heel bulbs with the use of a digital force gauge before (baseline) and at 15-minute intervals after treatment.
RESULTS
The mean duration of sensory blockade of the digit was 2-fold longer when a combination of mepivacaine and dexmedetomidine was administered (371 minutes), compared with when mepivacaine alone was administered (186 minutes). Treatment with dexmedetomidine alone did not change the mechanical nociceptive threshold substantially from baseline and resulted in no clinical signs of sedation.
CLINICAL RELEVANCE
Results indicated that relief from digital pain provided by perineural treatment with mepivacaine for PDN blockade can be extended by adding dexmedetomidine to the injectate.
Abstract
OBJECTIVE To evaluate the effect of IM administration of a tiletamine hydrochloride–zolazepam hydrochloride (TZ) combination with either dexmedetomidine hydrochloride or saline (0.9% NaCl) solution (SS) on the motor response to claw clamping, selected cardiorespiratory variables, and quality of recovery from anesthesia in alpacas.
ANIMALS 5 adult sexually intact male alpacas.
PROCEDURES Each alpaca was given the TZ combination (2 mg/kg) with dexmedetomidine (5 [D5], 10 [D10], 15 [D15], or 20 [D20] µg/kg) or SS IM at 1-week intervals (5 experiments); motor response to claw clamping was assessed, and characteristics of anesthesia, recovery from anesthesia, and selected cardiorespiratory variables were recorded.
RESULTS Mean ± SEM duration of lack of motor response to claw clamping was longest when alpacas received treatments D15 (30.9 ± 5.9 minutes) and D20 (40.8 ± 5.9 minutes). Duration of lateral recumbency was significantly longer with dexmedetomidine administration. The longest time (81.3 ± 10.4 minutes) to standing was observed when alpacas received treatment D20. Following treatment SS, 4 alpacas moved in response to claw clamping at the 5-minute time point. Heart rate decreased from pretreatment values in all alpacas when dexmedetomidine was administered. Treatments D10, D15, and D20 decreased Pao2, compared with treatment SS, during the first 15 minutes. During recovery, muscle stiffness and multiple efforts to regain a sternal position were observed in 3 SS-treated and 1 D5-treated alpacas; all other recoveries were graded as excellent.
CONCLUSIONS AND CLINICAL RELEVANCE In TZ-anesthetized alpacas, dexmedetomidine (10, 15, and 20 µg/kg) administered IM increased the duration of lack of motor response to claw clamping, compared with the effect of SS.
Abstract
OBJECTIVE To determine effects of fentanyl, lidocaine, and a fentanyl-lidocaine combination on the minimum alveolar concentration of sevoflurane preventing motor movement (MACNM) in dogs.
ANIMALS 6 adult Beagles.
PROCEDURES Dogs were anesthetized with sevoflurane in oxygen 3 times (1-week intervals). Baseline MACNM (MACNM-B) was determined starting 45 minutes after induction of anesthesia. Dogs then received 1 of 3 treatments IV: fentanyl (loading dose, 15 μg/kg; constant rate infusion [CRI], 6 μg/kg/h), lidocaine (loading dose, 2 mg/kg; CRI, 6 mg/kg/h), and the fentanyl-lidocaine combination at the same doses. Determination of treatment MACNM (MACNM-T) was initiated 90 minutes after start of the CRI. Venous blood samples were collected at the time of each treatment MACNM measurement for determination of plasma concentrations of fentanyl and lidocaine.
RESULTS Mean ± SEM overall MACNM-B for the 3 treatments was 2.70 ± 0.27 vol%. The MACNM decreased from MACNM-B to MACNM-T by 39%, 21%, and 55% for fentanyl, lidocaine, and the fentanyl-lidocaine combination, respectively. This decrease differed significantly among treatments. Plasma fentanyl concentration was 3.25 and 2.94 ng/mL for fentanyl and the fentanyl-lidocaine combination, respectively. Plasma lidocaine concentration was 2,570 and 2,417 ng/mL for lidocaine and the fentanyl-lidocaine combination, respectively. Plasma fentanyl and lidocaine concentrations did not differ significantly between fentanyl and the fentanyl-lidocaine combination or between lidocaine and the fentanyl-lidocaine combination.
CONCLUSIONS AND CLINICAL RELEVANCE CRIs of fentanyl, lidocaine, and the fentanyl-lidocaine combination at the doses used were associated with clinically important and significant decreases in the MACNM of sevoflurane in dogs.
Abstract
OBJECTIVE To determine the minimum infusion rate (MIR) of propofol required to prevent movement in response to a noxious stimulus in dogs anesthetized with propofol alone or propofol in combination with a constant rate infusion (CRI) of ketamine.
ANIMALS 6 male Beagles.
PROCEDURES Dogs were anesthetized on 3 occasions, at weekly intervals, with propofol alone (loading dose, 6 mg/kg; initial CRI, 0.45 mg/kg/min), propofol (loading dose, 5 mg/kg; initial CRI, 0.35 mg/kg/min) and a low dose of ketamine (loading dose, 2 mg/kg; CRI, 0.025 mg/kg/min), or propofol (loading dose, 4 mg/kg; initial CRI, 0.3 mg/kg/min) and a high dose of ketamine (loading dose, 3 mg/kg; CRI, 0.05 mg/kg/min). After 60 minutes, the propofol MIR required to prevent movement in response to a noxious electrical stimulus was determined in duplicate.
RESULTS Least squares mean ± SEM propofol MIRs required to prevent movement in response to the noxious stimulus were 0.76 ± 0.1 mg/kg/min, 0.60 ± 0.1 mg/kg/min, and 0.41 ± 0.1 mg/kg/min when dogs were anesthetized with propofol alone, propofol and low-dose ketamine, and propofol and high-dose ketamine, respectively. There were significant decreases in the propofol MIR required to prevent movement in response to the noxious stimulus when dogs were anesthetized with propofol and low-dose ketamine (27 ± 10%) or with propofol and high-dose ketamine (30 ± 10%).
CONCLUSIONS AND CLINICAL RELEVANCE Ketamine, at the doses studied, significantly decreased the propofol MIR required to prevent movement in response to a noxious stimulus in dogs.
Abstract
Objective—To investigate the effects of the concurrent administration of 70% N2O on the minimum alveolar concentration (MAC) for sevoflurane in dogs, the MAC derivative that blocks motor movement (MACNM), and the MAC derivative that blocks autonomic responses (MACBAR).
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, MACNM, and MACBAR 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, MACNM, and MACBAR were determined again. Percentage changes from the respective baseline concentrations for MAC, MACNM’ and MACBAR were calculated after the administration of N2O.
Results—Baseline median values for the MAC, MACNM, and MACBAR for sevoflurane were 1.75%, 2.00%, and 2.50%, respectively. Addition of 70% N2O significantly decreased MAC, MACNM, and MACBAR 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% N2O caused a clinically important and significant decrease in the MAC, MACNM’ and MACBAR for sevoflurane in dogs.
Abstract
OBJECTIVE To evaluate the effect of MgSO4, alone and in combination with propofol, on the minimum alveolar concentration preventing motor movement (MACNM) in sevoflurane-anesthetized dogs.
ANIMALS 6 healthy purpose-bred adult male Beagles (least squares mean ± SEM body weight, 12.0 ± 1.1 kg).
PROCEDURES Dogs were anesthetized 3 times at weekly intervals. The MACNM was measured 45 minutes after induction of anesthesia (baseline; MACNM-B) and was determined each time by use of a noxious electrical stimulus. Treatments were administered as a loading dose and constant rate infusion (CRI) as follows: treatment 1, MgSO4 loading dose of 45 mg/kg and CRI of 15 mg/kg/h; treatment 2, propofol loading dose of 4 mg/kg and CRI of 9 mg/kg/h; and treatment 3, MgSO4 and propofol combination (same doses used previously for each drug). A mixed-model ANOVA and Tukey-Kramer tests were used to determine effects of each treatment on the percentage decrease from MACNM-B. Data were reported as least squares mean ± SEM values.
RESULTS Decrease from MACNM-B was 3.4 ± 3.1%, 48.3 ± 3.1%, and 50.3 ± 3.1%, for treatments 1, 2, and 3, respectively. The decrease for treatments 2 and 3 was significantly different from that for treatment 1; however, no significant difference existed between results for treatments 2 and 3.
CONCLUSIONS AND CLINICAL RELEVANCE MgSO4 did not affect MACNM, nor did it potentiate the effects of propofol on MACNM. Administration of MgSO4 in this study appeared to provide no clinical advantage as an anesthetic adjuvant.
Abstract
Objectives
To determine the effects of orally administered omeprazole, as enteric-coated capsules, on baseline and stimulated gastric acid secretion in horses.
Animals
5 healthy 8-year-old mixed-breed horses fitted with gastric cannulas.
Procedure
Enteric-coated granules of omeprazole were mixed with corn syrup and administered orally once daily for 5 consecutive days. On days 1 and 5 beginning 5 hours after omeprazole administration, 4 gastric fluid samples were collected, each for 15 minutes, via the gastric cannula (baseline samples). Pentagastrin was administered IV as a constant infusion for the subsequent 2 hours, and 15-minute gastric fluid samples were again collected (stimulated samples). Fluid volume, acidity (mmol H+/L), and pH and gastric acid production (mmol H+) were determined for all baseline samples and for stimulated samples collected during the second hour of pentagastrin infusion. Control experiments were done in a similar manner after giving corn syrup alone to the same horses.
Results
Compared with values obtained during control experiments, baseline and stimulated gastric fluid acidity and gastric acid production significantly decreased, and the mean pH of gastric fluid samples significantly increased, after horses were given 5 daily doses of omeprazole.
Conclusions and Clinical Relevance
Enteric-coated omeprazole (1.0 mg/kg of body weight; PO) administered once daily for 5 days significantly inhibited unstimulated and pentagastrin-stimulated gastric acid secretion in horses. This commercially available formulation of omeprazole may be efficacious in the treatment of gastroduodenal ulcers in horses. (Am J Vet Res 1999;60:929–931)
Abstract
OBJECTIVE To determine the effects of stacked wedge pads and chains applied to the forefeet of Tennessee Walking Horses on behavioral and biochemical indicators of pain, stress, and inflamation.
ANIMALS 20 Tennessee Walking Horses.
PROCEDURES Horses were randomly assigned to 2 treatment groups: keg shoes (control; n = 10) or stacked wedge pads and exercise with chains (10). Ten days before treatment application, an accelerometer was attached at the left metatarsus of each horse to record daily activity. Horses were exercised for 20 minutes daily, beginning on day -7. On day 0, exercise ceased, the forefeet were trimmed, and the assigned treatment was applied. From days 1 through 5, horses were exercised as before. Blood samples for measurement of plasma cortisol, substance P, and fibrinogen concentrations were collected on days -5, 1, and 5 before and after exercise and every 30 minutes thereafter for 6 hours.
RESULTS No significant differences in plasma concentrations of cortisol, substance P, and fibrinogen were detected between groups. Although lying behaviors changed after shoes were applied, these behaviors did not differ significantly between groups. Shoeing appeared to have altered behavior to a greater extent than did the type of treatment applied.
CONCLUSIONS AND CLINICAL RELEVANCE Application of stacked wedge pads and chains to the forefeet of horses for a 5-day period as performed in this study evoked no acute or subacute stress or nociceptive response as measured. Although these findings should not be extrapolated to the long-term use of such devices in Tennessee Walking Horses performing the running walk, the data should be considered when making evidence-based decisions relating to animal welfare and the use of stacked wedge pads and chains.
Abstract
OBJECTIVE
To determine the efficacy and duration of effect for liposomal bupivacaine following perineural administration to the medial and lateral palmar digital nerves of horses.
ANIMALS
9 nonlame mares.
PROCEDURES
For each horse, 2 mL of liposomal bupivacaine (13.3 mg/mL; total dose, 53.2 mg or approx 0.11 mg/kg) or sterile saline (0.9% NaCl) solution was injected adjacent to the medial and lateral palmar digital nerves at the level of the distal aspect of the proximal sesamoid bones of a randomly selected forelimb. Twenty-one days later, the opposite treatment was administered in the contralateral forelimb. A digital algometer was used to measure the mechanical nociceptive threshold (MNT) immediately before and at predetermined times for 48 hours after injection of each treatment. The mean MNT was compared between the 2 treatments at each measurement time.
RESULTS
The mean MNT for the liposomal bupivacaine-treated limbs was significantly greater (ie, the limb was less sensitive) than that for the saline-treated limbs between 30 minutes and 4 hours after treatment injection. Following liposomal bupivacaine administration, 1 horse developed mild swelling at the injection sites that resolved without treatment within 24 hours. No other adverse effects were observed.
CONCLUSIONS AND CLINICAL RELEVANCE
Results suggested that liposomal bupivacaine is another option for perineural anesthesia in horses. Further research is necessary to determine the optimal dose and better elucidate the duration of effect for the drug when used for palmar digital nerve blocks in horses.