Analgesic effects of epidurally administered levogyral ketamine alone or in combination with morphine on intraoperative and postoperative pain in dogs undergoing ovariohysterectomy

OBJECTIVE: To evaluate the analgesic and adverse effects of epidurally administered levogyral (S[+]) ketamine alone or in combination with morphine on intraoperative and postoperative pain in dogs undergoing ovariohysterectomy. ANIMALS: 30 dogs scheduled for ovariohysterectomy. PROCEDURE: Dogs were randomly allocated to 1 of 3 groups. Dogs in group 1 received S(+) ketamine (1 mg/kg), dogs in group 2 received S(+) ketamine (0.5 mg/kg) and morphine (0.05 mg/kg), and dogs in group 3 received S(+) ketamine (1 mg/kg) and morphine (0.025 mg/kg). The skin was incised 15 minutes after epidural administration of analgesics. Heart rate (HR), respiratory rate (RR), systolic blood pressure (SBP), oxygen saturation as measured by pulse oximetry, and arterial blood gases were obtained before anesthesia, 15 minutes after epidural administration of analgesics, 15 and 30 minutes after initiation of surgery, and at the end of surgery. During the intraoperative period, an increase of > or =20% in baseline values for HR, RR, and SBP was considered a sign of intraoperative pain. Signs of pain and adverse effects were assessed at 2, 4, and 8 hours postoperatively. RESULTS: There were no significant differences in intraoperative or postoperative measurements among the 3 groups. No dogs had intraoperative signs of pain. Mean postoperative pain assessment scores were <3.5 in all 3 groups. Salivation was the most frequent adverse effect in dogs in groups 1 and 3, and sedation occurred more frequently in dogs in groups 2 and 3. CONCLUSIONS AND CLINICAL RELEVANCE: All 3 analgesic regimens provided good respiratory and cardiovascular stability intraoperatively and adequate postoperative analgesia with minimal adverse effects.     

The post-operative analgesic effects of epidurally administered morphine and transdermal fentanyl patch after ovariohysterectomy in dogs

ObjectiveTo investigate the analgesic and side effects of epidural morphine or a fentanyl patch after ovariohysterectomy in dogs.Study designProspective, randomized clinical study.AnimalsTwenty female mongrel dogs undergoing ovariohysterectomy.MethodsThe dogs were allocated to one of two groups: epidural morphine or transdermal fentanyl patch. Anaesthesia was induced with propofol and maintained with isoflurane. Morphine (0.1 mg kg^?1) was administered epidurally in the epidural morphine group and a transdermal fentanyl patch was applied 24 hours before the operation in the fentanyl patch group.The heart rate, respiratory rate, body temperature, plasma cortisol concentration, and sedation and analgesia scores were recorded during the 24 hour post-operative period. Adverse effects such as vomiting, anorexia, skin reactions, urinary retention, and time to start licking the surgical site were also recorded. p < 0.05 was considered significant. Statistical analyses utilized anova for repeated measures, Friedman tests, Mann-Whitney U-tests and independent sample t-tests as relevant.ResultsPain scores were lower in the epidural group than in the fentanyl group at all post-operative times. The dogs in the epidural morphine group were calm and relaxed, whereas discomfort and vocalization were recorded in the fentanyl patch group. The sedation scores were higher in the fentanyl patch group throughout the 12 hour period. Salivation and anorexia lasted longer in the fentanyl patch group than in the epidural morphine group. Plasma cortisol concentrations were high in the early post-operative period in both groups. The fentanyl patch group had higher cortisol concentrations than the epidural morphine group. Slight erythema was recorded in two dogs when the patches were removed.Conclusion and clinical relevanceEpidurally administered morphine provided better analgesia and caused fewer adverse effects than the fentanyl patch after ovariohysterectomy in dogs.     

Comparison of morphine and carprofen administered alone or in combination for analgesia in dogs undergoing ovariohysterectomy

In this study the analgesic efficacy of the pure agonistic opioid morphine and the cyclo-oxygenase type-2-selective carprofen were compared since there is no previous specific comparative study for these two common analgesics. Forty-five bitches undergoing elective ovariohysterectomy were randomly assigned to one of three groups; receiving morphine 0.4 mg/kg bodyweight pre-operatively and 0.2 mg/kg every 4-6 hours thereafter (Morphine group), receiving a once-off carprofen 4 mg/kg injection (Carprofen group) or receiving both morphine and carprofen (MorphCarp group). The dogs were premedicated with acepromazine 0.01 mg/kg and induced with either thiopentone 5-10 mg/kg or propofol 4-6 mg/kg. General anaesthesia was maintained with halothane in oxygen. The degree of pain was assessed over a 24-hour period under blinded conditions using a pain scale modified from the University of Melbourne pain scale and the Glasgow composite pain tool. Physiological parameters such as respiratory rate, pulse rate and body temperature were also assessed over the same time period. There was no significant difference in pain-scores and thus analgesia offered by the three analgesia protocols at any assessment point across the three groups, but there were differences within groups across time points. Baseline total pain-scores were lower than scores at all post-operative points within all three groups. Both morphine and carprofen provided good analgesia without any obvious adverse effects. This study indicates that at the dosages indicated above, carprofen administered on its own produces analgesia equal to that produced by morphine and that the two drugs administered together do not produce better analgesia than either drug administered on its own.     

Analgesic, hemodynamic and respiratory effects of caudal epidurally administered ropivacaine hydrochloride in mares

Objective To determine the analgesic, hemodynamic and respiratory effects, sedation and ataxia in mares of caudal epidural administration of ropivacaine hydrochloride solution. Study design Prospective, single‐dose trial. Animals Ten healthy mares weighing from 475 to 565 kg. Methods Intravascular catheters and an epidural needle were placed after infiltration of the skin and subcutaneous tissues with 2% lidocaine. Ropivacaine (0.5%, 8 or 9 mL) was then injected epidurally at the fifth sacral or sacrococcygeal vertebrae, respectively. Analgesia was determined by lack of sensory perception to electrical stimulation (> 40 milliamps) and absence of response to needle pricks extending from coccyx to S2 dermatomes. Electrocardiogram, heart and respiratory rates, rectal temperature, arterial blood pressure, arterial acid‐base (pH, standard bicarbonate and base excess), gas tensions (PO₂, PCO₂), PCV, oxyhemoglobin and total solids concentrations, and numerical scores of perineal analgesia, sedation (head drop), and ataxia (position of pelvic limbs) were determined before and during a 5‐hour testing period. Analysis of variance (anova ) with repeated measures was used to detect significant (p < 0.05) differences of mean values from baseline. Results Epidurally administered ropivacaine induced variable analgesia extending bilaterally from coccyx to S2 (three mares), coccyx to S3 (four mares), and coccyx to S4 (three mares), with minimal sedation, ataxia, and cardiovascular and respiratory disturbances of mares. Perineal analgesia was attained at 10 ± 4 minutes and lasted for 196 ±42 minutes (mean ± SD). Five mares demonstrated inadequate perineal analgesia, probably attributable to deviation of the spinal needle from the midline. They were successfully blocked with ropivacaine on another occasion. Epidural ropivacaine significantly reduced repiratory rates of mares and did not change other variables from baseline. Conclusions and clinical relevance Ropivacaine (0.5%, 8 mL 500 kg^?1) can be administered caudal epidurally to produce prolonged (> 2.5 hours) bilateral perineal analgesia with minimal sedation, ataxia, and circulatory and respiratory disturbances in standing mares.     

Cardiovascular effects of epidurally administered oxymorphone and an oxymorphone-bupivacaine combination in halothane-anesthetized dogs

OBJECTIVE: To evaluate cardiovascular effects of epidurally administered oxymorphone (OXY) and an OXY-bupivacaine combination (O/B) in halothane-anesthetized dogs. ANIMALS: 6 dogs. PROCEDURE: In a randomized crossover design study, dogs were anesthetized with halothane and given OXY, O/B, and saline solution (SAL). Eucapnia and end-tidal halothane concentration of 1.2% were established. Heart rate (HR), systemic and pulmonary arterial pressures, central venous pressure (CVP), and cardiac output were measured at baseline and 5, 15, 30, 45, 60, and 75 minutes after treatment. At 90 minutes, glycopyrrolate was administered IV, and measurements were repeated at 95 minutes. Cardiac index (CI), stroke volume, stroke index, systemic vascular resistance (SVR), and left ventricular work were calculated. End-tidal halothane concentration was decreased to 0.8% from 17 to 45 minutes and to 0.5% from 47 to 95 minutes for OXY and O/B, whereas for SAL, it was maintained at 1.5 and 1.2%, respectively. Samples were obtained at 0, 2, 5, 15, 30, 45, 60, and 95 minutes for measurement of serum opiate concentration and comparison with values after IM administration of OXY. RESULTS: HR decreased, but CVP and SVR increased in response to OXY and O/B. These changes were reversed after IV administration of glycopyrrolate, resulting in significant increase in CI, compared with that in response to SAL. Serum opiate concentration increased markedly and peaked within 15 minutes after OXY and O/B administration but did not differ from values after IM administration. CONCLUSIONS: Epidural administration of OXY results in rapid systemic uptake and decreased HR. Glycopyrrolate administration improves HR, resulting in improved CI at equipotent halothane concentrations.     

A comparison of the haemodynamic effects of epidurally administered medetomidine and xylazine in dogs

Alpha₂ agonists have a significant role in epidural anaesthetic techniques. However, there are few reports regarding epidural administration of these drugs especially in small animals ( Greene et al. 1995; Keegan et al. 1995; Vesal et al. 1996 ). This study compared the haemodynamic effects of xylazine and medetomidine after epidural injection in dogs. Six dogs (four females and two males) weighing 27.5 ± 3.39 kg, aged 5.6 ± 1.42 years were studied on two separate occasions one month apart. Dogs were sedated with 0.5 mg kg^?1 diazepam IM and 0.1 mg kg^?1 acepromazine IM. After 20 minutes, a lumbosacral epidural injection of 0.25 mg kg^?1 xylazine was administered (group X). One month later, following the same sedation, 15 µg kg^?1 medetomidine was administered epidurally (group M). Haemodynamic variables (ECG and indirect blood pressure (Doppler)), respiratory rate and rectal temperature were recorded before (baseline) and then every 5 minutes after the epidural injection, up to 60 minutes. Differences between groups were compared by a paired t‐test. Within group changes were compared to basal values by anova . A p‐value of < 0.05 was considered statistically significant. Both groups showed significant reductions in heart rate (106.3 ± 7.7 beats minute^?1 baseline versus 67.7 ± 7.6 (group M); 91 ± 3.8 baseline versus 52.3 ± 9 (group X)) and mean arterial blood pressure (113.1 ± 12.3 mm Hg baseline versus 87 ± 11 (group M); 118 ± 7 baseline versus 91 ± 14 (group X)). There were no differences between groups in these variables. After epidural injection, first degree atrioventricular block was recorded significantly more often in group X (50% against 33%) but second degree block was significantly more frequent in group M (66% against 33%). Also 50% of dogs in group X and 66% in group M showed sinus arrest. Respiratory rate decreased significantly in both groups following the epidural injection (20.66 ± 0.66 minute^?1 baseline versus 16.33 ± 4.77 (group M); 37.66 ± 0.56 baseline versus 16.33 ± 1.81 group X), but no differences between groups were observed. Rectal temperature decreased significantly in group X (38.16 ± 0.21) with respect to the basal measurement (39.30 ± 0.14 °C). In group M, there was no significant reduction in temperature, however, no statistical difference in rectal temperature was found between groups. This study shows that 0.25 mg kg^?1 xylazine and 15 µg kg^?1 medetomidine produce similar, significant cardiovascular and respiratory changes following lumbosacral epidural administration in dogs.     

Interaction between epidurally administered ketamine and pethidine in dogs

The present study was designed to test the hypothesis that a synergistic interaction could be recorded after epidural administration of ketamine-an N-methyl-D-aspartate (NMDA) antagonist and pethidine--an opioid agonist. Twelve adult mongrel dogs of either sex were randomly divided in three groups A, B and C of four animals each. Ketamine (5%) at 2.5 mg/kg and pethidine (3%) 2 mg/kg were injected at lumbosacral epidural space in animals of groups A and B, respectively. In animals of group C ketamine (2.5 mg/kg) and pethidine (2 mg/kg) were injected. Heart rate increased significantly up to 15 min in group A, whereas in groups B and C, the increase was non-significant for a period of 10 and 45 min, respectively. Respiration increased gradually up to 45-60 min in group A and for 15-20 min in group B. However, in animals of group C respiration fell below the baseline during the first 10-15 min and then returned near the baseline. Rectal temperature decreased only marginally in all the groups. Ketamine alone produced complete analgesia at tail and perineal region for a period of 5-10 min and then moderate analgesia for the next 20-30 min. Analgesia at the flank was moderate to complete between 5 and 15 min. In group B complete analgesia was only moderate at the tail and perineal region up to 30 min. In animals of group C, complete analgesia was observed only at perineal region for a very short period (5 min). Analgesia was not associated with sedation in any of the groups but animals of groups A and C showed signs of motor incoordination. Results of the study suggest rather antagonistic than synergistic interaction between epidurally administered ketamine and pethidine. Further studies are needed to confirm the antagonistic interaction between the two drugs.     

Cardiopulmonary effects of epidurally administered xylazine in the horse

This study was designed to determine whether the epidural administration of an alpha2 agonist, xylazine, would produce measurable changes in arterial blood pressure, electrocardiographic (ECG) activity and arterial blood gas values in horses. Six horses were given each of four treatments: epidural xylazine, intravenous xylazine, epidural lidocaine and epidural saline. A carotid artery catheter was used to measure arterial blood pressure and to collect samples for blood gas analysis before treatment and at intervals post treatment. Heart rate, arterial pressures, ECG activity and respiratory rate were recorded at the same intervals. No significant changes were recorded between time intervals or between individual treatments. It was concluded that this method of xylazine administration to horses produced potent caudal analgesia without measurable cardiopulmonary effects.     

Effects of epidurally administered morphine or buprenorphine on the thermal threshold in cats

Objective: To determine the antinociceptive effects of epidural administration of morphine or buprenorphine in cats by use of a thermal threshold model. ANIMALS: 6 healthy adult cats. PROCEDURES: Baseline thermal threshold was determined in duplicate. Cats were anesthetized with isoflurane in oxygen. Morphine (100 microg/kg diluted with saline [0.9% NaCl] solution to a total volume of 0.3 mL/kg), buprenorphine (12.5 microg/kg diluted with saline solution to a total volume of 0.3 mL/kg), or saline solution (0.3 mL/kg) was administered into the epidural space according to a Latin square design. Thermal threshold was determined at various times up to 24 hours after epidural injection. RESULTS: Epidural administration of saline solution did not affect thermal threshold. Thermal threshold was significantly higher after epidural administration of morphine and buprenorphine, compared with the effect of saline solution, from 1 to 16 hours and 1 to 10 hours, respectively. Maximum (cutout) temperature was reached without the cat reacting in 0, 74, and 11 occasions in the saline solution, morphine, and buprenorphine groups, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Epidural administration of morphine and buprenorphine induced thermal antinociception in cats. At the doses used in this study, the effect of morphine lasted longer and was more intense than that of buprenorphine.     

Antinociceptive effects of epidural magnesium sulphate alone and in combination with morphine in dogs

ObjectiveTo compare the antinociceptive effects of magnesium sulphate (MgSO₄) when administered epidurally alone and in combination with morphine.Study designExperimental, randomized, ‘blinded’, crossover study.AnimalsSix healthy adult Beagle dogs.MethodsEvaluated treatments were MgSO₄ (2.5 mg kg⁻¹) alone (Mg), morphine (0.1 mg kg⁻¹) alone (Mo), MgSO₄ in combination with morphine (Mm), and sterile water (0.115 mL kg⁻¹; Co) that were injected in the lumbosacral epidural space using an epidural catheter. Antinociception was measured using the von Frey mechanical threshold device applied to the carpal pads, both sides of the thorax and metatarsi. Measurements were obtained at time points: before treatment (baseline) and 0.5, 1, 2, 4, 6, 12, 18 and 24 hours after the epidural injection. Sedation, behaviour score and presence of motor deficits were assessed. Data were analyzed using a linear mixed model and Bonferroni adjustments, with significance set at p < 0.05.ResultsThere were significant effects of treatment and time in all regions. Overall threshold values in grammes force [median (interquartile range)] when stimulation regions were combined were significantly higher in Mg [164 (135–200)], Mo [156 (129–195)] and Mm [158 (131–192)] compared to Co [145 (120–179)]. Thresholds were significantly higher compared to Co in Mg, Mo and Mm at the thorax and metatarsi, but only in Mg and Mo at the carpal pads. No motor deficits were observed at any time point. Thresholds (combined regions) were increased from baseline at one or more time points with all treatments, including control.Conclusion and clinical relevanceEpidural MgSO₄ produced an antinociceptive effect characterised by an increase in the mechanical thresholds of similar magnitude to that produced by epidural morphine, compared with the control group, without causing any motor deficits. No potentiation of morphine antinociception was observed. The onset and offset times of antinociception could not be clearly established. To what extent these results can be extrapolated to clinical cases requires further investigation.     

Comparative hemodynamic effects of halothane and halothane-acepromazine at equipotent doses in dogs.

The purpose of this study was to compare the cardiovascular effects of halothane when used alone at increasing doses (1.2, 1.45 and 1.7 minimum alveolar concentration, MAC) to those produced with equipotent doses of halothane after potentiation of the anesthetic effect with acepromazine (ACP) sedation (45% reduction of halothane MAC). Six healthy mature dogs were used on three occasions. The treatments were halothane and intramuscular (IM) saline (1.0 mL), halothane and ACP (0.04 mg/kg IM), or halothane and ACP (0.2 mg/kg IM). Anesthesia was induced and maintained with halothane in oxygen and the dogs were prepared for the collection of arterial and mixed venous blood and for the determination of heart rate, systolic, diastolic and mean arterial pressure, mean pulmonary arterial pressure (PAP), central venous pressure and cardiac output. Following animal preparation the saline or ACP was administered and positive pressure ventilation instituted. Twenty-five minutes later the dogs were exposed to the first of three anesthetic levels, with random assignment of the sequence of administration. At each anesthetic level, measurements were obtained at 20 and 35 min. Calculated values included cardiac index, stroke index, left ventricular work, systemic vascular resistance, arterial oxygen content, mixed venous oxygen content, oxygen delivery and oxygen consumption. Heart rate was significantly higher with halothane alone than with both halothane-ACP combinations and was significantly higher with high dose ACP compared to low dose ACP. Systolic and mean blood pressures were lowest with halothane alone and highest with 0.2 mg/kg ACP, the differences being significant for each treatment. Oxygen uptake and PAP were significantly lower in dogs treated with ACP. It was concluded that ACP does not potentiate the cardiovascular depression that accompanies halothane anesthesia when the resultant lower dose requirements of halothane are taken into consideration.     

Comparison of the effects of morphine administered by constant-rate intravenous infusion or intermittent intramuscular injection in dogs

OBJECTIVE: To compare physiologic and analgesic effects of morphine when given by IV constant-rate infusion or by IM injection to dogs undergoing laparotomy and to determine pharmacokinetics of morphine in dogs following IV constant-rate infusion. DESIGN: Prospective randomized controlled trial. ANIMALS: 20 dogs. PROCEDURE: Dogs undergoing laparotomy were treated with morphine beginning at the time of anesthetic induction. Morphine was administered by IV infusion (0.12 mg/kg/h [0.05 mg/lb/h] of body weight) or by IM injection (1 mg/kg [0.45 mg/lb]) at induction and extubation and every 4 hours thereafter. Treatments continued for 24 hours after extubation. RESULTS: Blood gas values did not indicate clinically significant respiratory depression in either group, and degree of analgesia (determined as the University of Melbourne Pain Scale score) and incidence of adverse effects (panting, vomiting, defecation, and dysphoria) were not significantly different between groups. Dogs in both groups had significant decreases in mean heart rate, rectal temperature, and serum sodium and potassium concentrations, compared with preoperative values. Mean +/- SEM total body clearance of morphine was 68 +/- 6 ml/min/kg (31 +/- 3 ml/min/lb). Mean steady-state serum morphine concentration in dogs receiving morphine by constant-rate infusion was 30 +/- 2 ng/ml. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that administration of morphine as a constant-rate IV infusion at a dose of 0.12 mg/kg/h induced effects similar to those obtained with administration at a dose of 1 mg/kg, IM, every 4 hours in dogs undergoing laparotomy. Panting was attributed to an opioid-induced resetting of the hypothalamic temperature set point, rather than respiratory depression.     

Isoflurane sparing action of epidurally administered xylazine hydrochloride in anesthetized dogs

OBJECTIVE: To evaluate the influence of epidural administration of xylazine hydrochloride on the minimum alveolar concentration of isoflurane (MAC(ISAO)) and cardiopulmonary system in anesthetized dogs. ANIMALS: 6 clinically normal dogs. PROCEDURE: Dogs were anesthetized with isoflurane in oxygen after randomly being assigned to receive 1 of the following 4 treatments: epidural administration of saline (0.9% NaCl) solution or xylazine at a dose of 0.1, 0.2, or 0.4 mg x kg(-1). Experiments were performed on 5 occasions with at least a 1-week interval between experiments; each dog received all 4 treatments. Following instrumentation, the concentration of isoflurane was maintained constant for 15 minutes at the MAC(ISO) that had been determined for each dog, and data on heart rate, arterial blood pressure, respiratory rate, tidal volume, minute volume, arterial partial pressure of oxygen, arterial partial pressure of carbon dioxide, and arterial pH were collected. The epidural treatment was administered, and 30 minutes later, data were again collected. From this point on, determination of the MAC(ISO) following epidural treatment (ie, MAC(ISO+EPI)) was initiated. Cardiopulmonary data were collected before each electrical supramaximal stimulus during MAC(ISO+EPI) determinations. RESULTS: The mean (+/-SD) MAC(ISO) was 1.29 +/- 0.04%. The epidural administration of xylazine at doses of 0.1, 0.2, and 0.4 mg x kg(-1) decreased the MAC(ISO), respectively, by 8.4 +/- 2.4%, 21.7 +/- 4.9%, and 33.4 +/- 2.64%. Cardiopulmonary effects were limited. CONCLUSIONS AND CLINICAL RELEVANCE: Epidural administration of xylazine decreases the MAC(ISO) in a dose-dependent manner and is associated with few cardiopulmonary effects in anesthetized dogs.     

Arrhythmogenicity of dopamine and its effects on hemodynamics in dogs under halothane anesthesia

The arrhythmogenicity of dopamine, its effects on cardiac function, hemodynamics, and diuresis under halothane anesthesia were evaluated in dogs. The induction time of arrhythemias and the effect of arrhythmias on cardiac function, hemodynamics, and diuresis were determined after infusion of dopamine for 30-min period at increasing doses of 3, 5, 7, 10, and 15 micrograms/kg/min. The results were as follows. 1. Arrhythmia induction percentage was 28.6% at 5 micrograms/kg/mn, 42.9% at 7 micrograms/kg/min, 25% at 10 micrograms/kg/min, and 41.7% at 15 micrograms/kg/min. The induction time of arrhythemias (sec) was 459 at 5 micrograms/kg/min, 332 at 7 micrograms/kg/min, 152 at 10 micrograms/kg/min, and 279 at 15 micrograms/kg/min. No arrhythmias were present at 3 micrograms/kg/min. 2. Heart rate and myocardial oxygen consumption was increased in the arrhythmia-induced group compared to the non-arrhythmia-induced group. 3. Myocardial contractility, mean aortic pressure, mean pulmonary arterial pressure, and diuresis increased dose-dependently in the non-arrhythmia-induced group; however, these measures were increased in the arrhythmia-induced group without regard to dose.     

Comparison of hemodynamic, clinicopathologic, and gastrointestinal motility effects and recovery characteristics of anesthesia with isoflurane and halothane in horses undergoing arthroscopic surgery

OBJECTIVE: To compare hemodynamic, clinicopathologic, and gastrointestinal motility effects and recovery characteristics of halothane and isoflurane in horses undergoing arthroscopic surgery. ANIMALS: 8 healthy adult horses. PROCEDURE: Anesthesia was maintained with isoflurane or halothane (crossover study). At 6 intervals during anesthesia and surgery, cardiopulmonary variables and related derived values were recorded. Recovery from anesthesia was assessed; gastrointestinal tract motility was subjectively monitored for 72 hours after anesthesia. Horses were administered chromium, and fecal chromium concentration was used to assess intestinal transit time. Venous blood samples were collected for clinicopathologic analyses before and 2, 24, and 48 hours after anesthesia. RESULTS: Compared with halothane-anesthetized horses, cardiac index, oxygen delivery, and heart rate were higher and systemic vascular resistance was lower in isoflurane-anesthetized horses. Mean arterial blood pressure and the dobutamine dose required to maintain blood pressure were similar for both treatments. Duration and quality of recovery from anesthesia did not differ between treatments, although the recovery periods were somewhat shorter with isoflurane. After isoflurane anesthesia, gastrointestinal motility normalized earlier and intestinal transit time of chromium was shorter than that detected after halothane anesthesia. Compared with isoflurane, halothane was associated with increases in serum aspartate transaminase and glutamate dehydrogenase activities, but there were no other important differences in clinicopathologic variables between treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with halothane, isoflurane appears to be associated with better hemodynamic stability during anesthesia, less hepatic and muscle damage, and more rapid return of normal intestinal motility after anesthesia in horses undergoing arthroscopic procedures.     

Cardiopulmonary and analgesic effects of caudal epidurally administered ropivacaine in cattle

ObjectiveTo assess cardiopulmonary and analgesic effects after administration of ropivacaine into the caudal epidural space of cattle.Study designProspective, single-dose trial.AnimalsEight healthy mixed breed cows aged 8 ± 5 years and weighing 507 ± 112 kg.MethodsCaudal epidural anesthesia was produced in cows with 0.75% ropivacaine (0.11 mg kg^?1). Onset time, duration and cranial spread of analgesia were recorded. Heart rate (HR), respiratory rate (f_R), rectal temperature (RT), and mean arterial blood pressure (MAP) were measured prior to epidural administration (T₀) and at 15, 30, 60, 120, 180 and 240 minutes after epidural administration (T₁₅, T₃₀, T₆₀, T₁₂₀, T₁₈₀ and T₂₄₀). Arterial blood acid-base balance (pH, standard bicarbonate and base excess), gas tension (PaO₂, PaCO₂, SaO₂) and electrolytes (Na⁺, K⁺, iCa²⁺,Cl^?) were recorded at T₀, T₃₀, T₆₀, T₁₂₀, T₁₈₀ and T_240. Ataxia was evaluated at T₀, T₃₀, T₆₀, T₁₂₀, T₁₈₀ and T₂₄₀ and at 1 hour intervals thereafter until analgesia was no longer present in each animal.ResultsEpidurally administered ropivacaine induced variable analgesia extending bilaterally from the coccyx to S3. Time to onset of analgesia and mean duration in the perineal area were 15 ± 4 and 359 ± 90 minutes, respectively. Respiratory rate and RT increased from T₁₂₀ to T₂₄₀ when compared to the value at T₀. Ionized calcium and chloride concentrations increased at T₁₈₀ and T₂₄₀ when compared to T₀. The other variables were not significantly different from baseline values (p> 0.05). Four animals were mildly ataxic.Conclusion and clinical relevanceRopivacaine (0.75%, 0.11 mg kg^?1) can be administered by caudal epidural injection to produce prolonged bilateral perineal analgesia with minimal ataxia and cardiopulmonary changes in standing cattle.     

Comparison of tramadol and morphine for pre-medication of dogs undergoing general anesthesia for orthopedic surgery

Tramadol is a centrally acting analgesic with opioid and monoaminergic actions. Its clinical effects have been well characterized in humans, where it has been in use for many years, but little is known for veterinary species. This study evaluated the sedative, emetic, thiopental‐sparing and intraoperative respiratory and hemodynamic effects of tramadol in comparison to morphine for pre‐medication of dogs undergoing orthopedic surgery under halothane anesthesia. Sixteen adult, healthy, mixed breed dogs (8.0 ± 2.6 kg) were studied. Eight dogs were pre‐medicated with tramadol (1.0 mg kg^‐1 IM) and the other eight with morphine (1.0 mg kg^–1 IM). After 20 minutes, anesthesia was induced with thiopental and subsequently maintained with halothane in oxygen using a Bain system, with spontaneous respiration. Degree of sedation and occurrence of emesis were evaluated after pre‐anesthetic medication. Dose of thiopental necessary for tracheal intubation was compared between the two groups. Arterial blood gas analyzes were done before pre‐medication and at 60 minutes of anesthesia. Heart rate and noninvasive arterial blood pressure were recorded before pre‐medication and every 10 minutes during anesthesia. Observer was blinded of the treatment given for each dog. Tramadol produced no visible sedation and no vomiting, while morphine induced a moderate degree of sedation in all dogs and vomiting in 62% of them. Dogs pre‐medicated with tramadol required significantly more thiopental (17 ± 3.8 mg kg^–1) for induction of anesthesia than those pre‐medicated with morphine (12 ± 1.8 mg kg^–1). Pre‐medication with morphine was associated with significantly higher PaCO₂ and lower pH at 60 minutes of anesthesia. The remaining respiratory parameters and the hemodynamic variables were similar between the two groups. In conclusion, dogs pre‐medicated with tramadol at 1 mg kg^–1 IM do not become visibly sedated and require a greater amount of thiopental for induction of anesthesia than pre‐medication with morphine. As intraoperative respiratory function is better preserved with tramadol, it may be useful for pre‐medication of respiratory compromised patients.