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1.
OBJECTIVE: To determine the relationship between bispectral index (BIS) and minimum alveolar concentration (MAC) multiples of isoflurane after IM injection of medetomidine or saline (0.9% NaCl) solution in anesthetized dogs. ANIMALS: 6 dogs. PROCEDURE: Each dog was anesthetized 3 times with isoflurane. First, the MAC of isoflurane for each dog was determined by use of the tail clamp method. Second, anesthetized dogs were randomly assigned to receive an IM injection of medetomidine (8 microg x kg(-1)) or an equal volume of isotonic saline (0.9% NaCl) solution 30 minutes prior to beginning BIS measurements. Last, anesthetized dogs received the remaining treatment (medetomidine or isotonic saline solution). Dogs were anesthetized at each of 4 MAC multiples of isoflurane. Ventilation was controlled and atracurium (0.2 mg/kg followed by 6 microg/kg/min as a continuous infusion, IV) administered. After a 20-minute equilibration period at each MAC multiple of isoflurane, BIS data were collected for 5 minutes and median values of BIS calculated. RESULTS: BIS significantly decreased with increasing MAC multiples of isoflurane over the range of 0.8 to 2.0 MAC. Mean (+/- SD) MAC of isoflurane was 1.3 +/- 0.2%. During isoflurane-saline anesthesia, mean BIS measurements at 0.8, 1.0, 1.5, and 2.0 MAC were 65 +/- 8, 60 +/- 7 52 +/- 3, and 31 +/- 28, respectively. During isoflurane-medetomidine anesthesia, mean BIS measurements at 0.8, 1.0, 1.5, and 2.0 MAC were 77 +/- 4, 53 +/- 7, 31 +/- 24, and 9 +/- 20, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: BIS monitoring in dogs anesthetized with isoflurane has a predictive value in regard to degree of CNS depression. During isoflurane anesthesia, our results support a MAC-reducing effect of medetomidine.  相似文献   

2.
OBJECTIVE: To determine the effects of meloxicam and butorphanol on minimum alveolar concentration of isoflurane (MAC(ISO)) in rabbits. ANIMALS: 10 healthy young adult female rabbits. PROCEDURE: Rabbits were anesthetized with isoflurane on 3 occasions in a blinded, randomized complete block design to determine the MAC(ISO) associated with administration of meloxicam (0, 0.3, or 1.5 mg/kg, PO) and butorphanol (0.4 mg/kg, IV). The MAC(ISO) was determined by use of a paw clamp technique as the end-tidal concentration of isoflurane halfway between the values that allowed or inhibited purposeful movement. Rectal temperature, end-tidal CO2 concentration, heart rate, oxygen saturation, and arterial blood pressure were measured to evaluate cardiopulmonary function. RESULTS: Mean +/- SE MAC(ISO) in saline (0.9% NaCl) solution-treated rabbits was 2.49 +/- 0.07% and was not significantly different from that associated with administration of meloxicam at 0.3 mg/kg (2.56 +/- 0.07%) or 1.5 mg/kg (2.66 +/- 0.07%). Butorphanol significantly reduced the MAC(ISO) to 2.30 +/- 0.07% when administered with saline solution alone, 2.27 +/- 0.07% when administered with 0.3 mg of meloxicam/kg, and 2.33 +/- 0.07% when administered with 1.5 mg of meloxicam/kg. The percentage reduction in MAC(ISO) was significantly greater for rabbits that received butorphanol and meloxicam at either dose, compared with butorphanol and saline solution. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that meloxicam does not have a direct isoflurane-sparing effect and does not interfere with the anesthetic-sparing effect of butorphanol in rabbits.  相似文献   

3.
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.  相似文献   

4.
OBJECTIVE: To determine effects of low doses of medetomidine administered with and without butorphanol and glycopyrrolate to middle-aged and old dogs. DESIGN: Prospective randomized clinical trial. ANIMALS: 88 healthy dogs > or = 5 years old. PROCEDURE: Dogs were assigned randomly to receive medetomidine (2, 5, or 10 micrograms/kg [0.9, 2.3, or 4.6 micrograms/lb] of body weight, i.m.) alone or with glycopyrrolate (0.01 mg/kg [0.005 mg/lb], s.c.), medetomidine (10 micrograms/kg) and butorphanol (0.2 mg/kg [0.1 mg/lb], i.m.), or medetomidine (10 micrograms/kg), butorphanol (0.2 mg/kg), and glycopyrrolate (0.01 mg/kg). Anesthesia was induced with thiopental sodium and maintained with isoflurane. Degree of sedation and analgesia were determined before and after medetomidine administration. Respiratory rate, heart rate, and mean arterial blood pressure were determined 10 and 30 minutes after medetomidine administration. Adverse effects and amounts of thiopental and isoflurane used were recorded. RESULTS: Sedation increased after medetomidine administration in 79 of 88 dogs, but decreased in 7 dogs that received 2 or 5 micrograms of medetomidine/kg. Mean postsedation analgesia score and amounts of thiopental and isoflurane used were less in dogs that received medetomidine and butorphanol, compared with other groups. Respiratory rate, heart rate, and blood pressure were not different among groups. Significantly more adverse effects developed in dogs that did not receive glycopyrrolate. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of medetomidine (10 micrograms/kg, i.m.) and butorphanol (0.2 mg/kg, i.m.) induced sedation and analgesia and reduced amounts of thiopental and isoflurane required for anesthesia in middle-aged and old dogs. Glycopyrrolate decreased frequency of medetomidine-associated adverse effects.  相似文献   

5.
OBJECTIVE: To evaluate the effects of butorphanol and carprofen, alone and in combination, on the minimal alveolar concentration (MAC) of isoflurane in dogs. DESIGN: Randomized complete-block crossover study. ANIMALS: 6 healthy adult dogs. PROCEDURE: Minimal alveolar concentration of isoflurane was determined following administration of carprofen alone, butorphanol alone, carprofen and butorphanol, and neither drug (control). Anesthesia was induced with isoflurane in oxygen, and MAC was determined by use of a tail clamp method. Three hours prior to induction of anesthesia, dogs were fed a small amount of canned food without any drugs (control) or with carprofen (2.2 mg/kg of body weight [1 mg/lb]). Following initial determination of MAC, butorphanol (0.4 mg/kg [0.18 mg/lb], i.v.) was administered, and MAC was determined again. Heart rate, respiratory rate, indirect arterial blood pressure, endtidal partial pressure of CO2, and saturation of hemoglobin with oxygen were recorded at the time MAC was determined. RESULTS: Mean +/- SD MAC of isoflurane following administration of butorphanol alone (1.03 +/- 0.22%) or carprofen and butorphanol (0.90 +/- 0.21%) were significantly less than the control MAC (1.28 +/- 0.14%), but MAC after administration of carprofen alone (1.20 +/- 0.13%) was not significantly different from the control value. The effects of carprofen and butorphanol on the MAC of isoflurane were additive. There were not any significant differences among treatments in regard to cardiorespiratory data. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that administration of butorphanol alone or in combination with carprofen significantly reduces the MAC of isoflurane in dogs; however, the effects of butorphanol and carprofen are additive, not synergistic.  相似文献   

6.
OBJECTIVE: To determine sedative and cardiorespiratory effects of i.m. administration of medetomidine alone and in combination with butorphanol or ketamine in dogs. DESIGN: Randomized, crossover study. ANIMALS: 6 healthy adult dogs. PROCEDURES: Dogs were given medetomidine alone (30 micrograms/kg [13.6 micrograms/lb] of body weight, i.m.), a combination of medetomidine (30 micrograms/kg, i.m.) and butorphanol (0.2 mg/kg [0.09 mg/lb], i.m.), or a combination of medetomidine (30 micrograms/kg, i.m.) and ketamine (3 mg/kg [1.36 mg/lb], i.m.). Treatments were administered in random order with a minimum of 1 week between treatments. Glycopyrrolate was given at the same time. Atipamezole (150 micrograms/kg [68 micrograms/lb], i.m.) was given 40 minutes after administration of medetomidine. RESULTS: All but 1 dog (given medetomidine alone) assumed lateral recumbency within 6 minutes after drug administration. Endotracheal intubation was significantly more difficult when dogs were given medetomidine alone than when given medetomidine and butorphanol. At all evaluation times, percentages of dogs with positive responses to tail clamping or to needle pricks in the cervical region, shoulder region, abdominal region, or hindquarters were not significantly different among drug treatments. The Paco2 was significantly higher and the arterial pH and Pao2 were significantly lower when dogs were given medetomidine and butorphanol or medetomidine and ketamine than when they were given medetomidine alone. Recovery quality following atipamezole administration was unsatisfactory in 1 dog when given medetomidine and ketamine. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that a combination of medetomidine with butorphanol or ketamine resulted in more reliable and uniform sedation in dogs than did medetomidine alone.  相似文献   

7.
OBJECTIVE: To evaluate the effect of medetomidine on minimum alveolar concentration (MAC), respiratory rate, tidal volume, minute volume (V(M)), and maximum inspiratory occlusion pressure (IOCP(max)) in halothane- and isoflurane-anesthetized dogs. ANIMALS: 6 healthy adult dogs (3 males and 3 females). PROCEDURE: The MAC of both inhalants was determined before and 5, 30, and 60 minutes after administration of medetomidine (5 microg/kg, IV). Dogs were subsequently anesthetized by administration of halothane or isoflurane and administered saline (0.9% NaCl) solution IV or medetomidine (5 microg/kg, IV). Respiratory variables and IOCP(max) were measured at specific MAC values 15 minutes before and 5, 30, and 60 minutes after IV administration of medetomidine while dogs breathed 0% and 10% fractional inspired carbon dioxide (FICO2). Slopes of the lines for VM/FICO2 and IOCP(max)/FICO2 were then calculated. RESULTS: Administration of medetomidine decreased MAC of both inhalants. Slope of V(M)/FICO2 increased in dogs anesthetized with halothane after administration of medetomidine, compared with corresponding values in dogs anesthetized with isoflurane. Administration of medetomidine with a simultaneous decrease in inhalant concentration significantly increased the slope for V(M)/FICO2, compared with values after administration of saline solution in dogs anesthetized with halothane but not isoflurane. Values for IOCP(max) did not differ significantly between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Equipotent doses of halothane and isoflurane have differing effects on respiration that are most likely attributable to differences in drug effects on central respiratory centers. Relatively low doses of medetomidine decrease the MAC of halothane and isoflurane in dogs.  相似文献   

8.
OBJECTIVE: To determine the effect of medetomidine on the stress response induced by ovariohysterectomy in isoflurane-anesthetized dogs. STUDY DESIGN: Prospective randomized study. ANIMALS: Twelve healthy adult female purpose-bred dogs, weighing 16.8 to 25 kg. METHODS: Two treatments were randomly administered to each of twelve dogs at weekly intervals: (1) Saline injected IM followed in 15 minutes by isoflurane anesthesia (ISO) induced by mask and maintained at an end-tidal concentration of 1.8% for 60 minutes; and (2) Medetomidine, 15 ug/lkg IM followed in 15 minutes by isoflurane anesthesia (ISO&MED) induced by mask and maintained at an end-tidal concentration of 1.0% for 60 minutes. One week after completion of these two treatments, all dogs were ovariohysterectomized. six receiving each treatment (SURG and SURG&MED). Central venous blood samples (10 mL) were obtained immediately before medetomidine or saline (baseline) and at 30, 75, and 195 minutes and 24 hours after administration of medetomidine or saline in ISO and ISO&MED. In SURG and SURG&MED, samples were obtained immediately prior to injection of medetomidine or saline (baseline) and at 30 (before skin incision), 45 (after severence of the ovarian ligament), 75 (after skin closure), 105 (30 minutes after skin closure, dog recovered and in sternal recumbency), 135, 195, 375 minutes, and 24 hours after the initial sample. Samples were analyzed for epinephrine, norepinephrine, adrenocorticotrophic hormone (ACTH), cortisol, insulin, and glucose. Data were analyzed by analysis of variance and where significant differences were found, a least significant difference test was applied. RESULTS: Premedication with medetomidine prevented or delayed the stress response induced by ovariohysterectomy in isoflurane-anesthetized dogs. CONCLUSIONS: The stress response induced by ovariohysterectomy, although significant, is of short duration. Medetomidine safely and effectively reduced surgically-induced stress responses. CLINICAL RELEVANCE: Surgically induced stress responses can be obtunded or prevented by administration of medetomidine.  相似文献   

9.
OBJECTIVE: To determine whether opioids with varying interactions at receptors induce a reduction in minimum alveolar concentration (MAC) of isoflurane in cats. ANIMALS: 12 healthy, female, spayed cats. PROCEDURE: Cats were anesthetized with isoflurane and instrumented to allow collection of arterial blood and measurement of arterial blood pressure. Each drug was studied separately, and for each drug cats were randomly allocated to receive 2 doses. The drugs studied were morphine (0.1 or 1.0 mg/kg), butorphanol (0.08 or 0.8 mg/kg), buprenorphine (0.005 and 0.05 mg/kg), and U50488H (0.02 and 0.2 mg/kg). All drugs were diluted in 5 ml of saline (0.9% NaCl) solution and infused IV for 5 minutes. The MAC of isoflurane was determined in triplicate, the drug administered, and the MAC of isoflurane redetermined for a period of 3 hours. RESULTS: All drugs had a significant effect on MAC over time. With morphine only, the effect on MAC over time was different between doses. The greatest mean (+/- SD) reductions in MAC of isoflurane in response to morphine, butorphanol, buprenorphine, and U50488H administration were 28 +/- 9, 19 +/- 3, 14 +/- 7, and 11 +/- 7%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Morphine (1.0 mg/kg) and butorphanol (0.08 and 0.8 mg/kg) induced significant reductions in MAC of isoflurane that were considered clinically important. Although significant, reductions in MAC of isoflurane induced by morphine (0.1 mg/kg), buprenorphine (0.005 and 0.05 mg/kg), and U50488H (0.02 and 0.2 mg/kg) were not considered clinically relevant because they fell within the error of the measurement technique. Administration of morphine or butorphanol decreases the need for potent inhalant anesthetics in cats and could potentially be beneficial in combination with inhalants.  相似文献   

10.
OBJECTIVE: To determine the effect of a constant-rate infusion of fentanyl on minimum alveolar concentration (MAC) of isoflurane and to determine the interaction between fentanyl and a benzodiazepine agonist (diazepam) and antagonist (flumazenil) in isoflurane-anesthetized dogs. ANIMALS: 8 mixed-breed adult dogs. PROCEDURE: Dogs were anesthetized with isoflurane 3 times during a 6-week period. After a 30-minute equilibration period, each MAC determination was performed in triplicate, using standard techniques. Fentanyl was administered as a bolus (10 microg/kg of body weight, IV) that was followed by a constant infusion (0.3 microg/kg per min, IV) throughout the remainder of the experiment. After determining isoflurane-fentanyl MAC in triplicate, each dog received saline (0.9% NaCl) solution, diazepam, or flumazenil. After 30 minutes, MAC was determined again. RESULTS: Fentanyl significantly decreased isoflurane MAC (corrected to a barometric pressure of 760 mm Hg) from 1.80+/-0.21 to 0.85+/-0.14%, a reduction of 53%. Isoflurane-fentanyl-diazepam MAC (0.48+/-0.29%) was significantly less than isoflurane-fentanyl-saline MAC (0.79+/-0.21%). Percentage reduction in isoflurane MAC was significantly greater for fentanyl-diazepam (74%), compared with fentanyl-saline (54%) or fentanyl-flumazenil (61%). Mean fentanyl concentrations for the entire experiment were increased over time and were higher in the diazepam group than the saline or flumazenil groups. CONCLUSIONS AND CLINICAL RELEVANCE: Fentanyl markedly decreased isoflurane MAC in dogs. Diazepam, but not flumazenil, further decreased isoflurane-fentanyl MAC. Our results indicate that diazepam enhances, whereas flumazenil does not affect, opioid-induced CNS depression and, possibly, analgesia in dogs.  相似文献   

11.
OBJECTIVE: To determine effects of epidural administration of morphine and buprenorphine on the minimum alveolar concentration of isoflurane in cats. Animals-6 healthy adult domestic shorthair cats. PROCEDURES: Cats were anesthetized with isoflurane in oxygen. Morphine (100 microg/kg diluted with saline [0.9% NaCl] solution to a volume of 0.3 mL/kg), buprenorphine (12.5 microg/kg diluted with saline solution to a 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. The minimum alveolar concentration (MAC) of isoflurane was measured in triplicate by use of the tail clamp technique. At least 1 week was allowed between successive experiments. RESULTS: The MAC of isoflurane was 2.00 +/- 0.18%, 2.13 +/- 0.11%, and 2.03 +/- 0.09% in the morphine, buprenorphine, and saline solution groups, respectively. No significant difference in MAC was detected among treatment groups. CONCLUSIONS AND CLINICAL RELEVANCE: A significant effect of epidural administration of morphine or buprenorphine on the MAC of isoflurane in cats could not be detected. Further studies are needed to establish whether epidural opioid administration has other benefits when administered as a component of general anesthesia in cats.  相似文献   

12.
OBJECTIVE: To determine the cardiorespiratory effects of preemptive atropine administration in dogs sedated with medetomidine. DESIGN: Randomized crossover trial. ANIMALS: 12 healthy adult dogs. PROCEDURES: Dogs underwent 6 treatments. Each treatment consisted of administration of atropine (0.04 mg/kg [0.018 mg/lb] of body weight, IM) or saline solution (0.9% NaCl, 1 ml, IM) and administration of medetomidine (10, 20, or 40 microg/kg [4.5, 9.1, or 18.2 microg/lb], IM) 10 minutes later. Treatments were administered in random order, with a minimum of 1 week between treatments. Cardiorespiratory effects before and after atropine and medetomidine administration were assessed. Duration of lateral recumbency and quality of sedation and recovery were assessed. RESULTS: Bradycardia (heart rate < 60 beats/min) was seen in all dogs when saline solution was administered followed by medetomidine, and the dose of medetomidine was not associated with severity or frequency of bradycardia or second-degree heart block. However, a medetomidine dose-dependent increase in mean and diastolic blood pressures was observed, regardless of whether dogs received saline solution or atropine. Preemptive atropine administration effectively prevented bradycardia and second-degree heart block but induced pulsus alternans and hypertension. The protective effects of atropine against bradycardia lasted 50 minutes. Blood gas values were within reference limits during all treatments and were not significantly different from baseline values. Higher doses of medetomidine resulted in a longer duration of lateral recumbency. CONCLUSIONS AND CLINICAL RELEVANCE: Preemptive administration of atropine in dogs sedated with medetomidine effectively prevents bradycardia for 50 minutes but induces hypertension and pulsus alternans.  相似文献   

13.
OBJECTIVE: To examine stress-related neurohormonal and metabolic effects of butorphanol, fentanyl, and ketamine administration alone and in combination with medetomidine in dogs. ANIMALS: 10 Beagles. PROCEDURE: 5 dogs received either butorphanol (0.1 mg/kg), fentanyl (0.01 mg/kg), or ketamine (10 mg/kg) IM in a crossover design. Another 5 dogs received either medetomidine (0.02 mg/kg) and butorphanol (0.1 mg/kg), medetomidine and fentanyl (0.01 mg/kg), medetomidine and ketamine (10 mg/kg), or medetomidine and saline (0.9% NaCI) solution (0.1 mL/kg) in a similar design. Blood samples were obtained for 6 hours following the treatments. Norepinephrine, epinephrine, cortisol, glucose, insulin, and nonesterified fatty acid concentrations were determined in plasma. RESULTS: Administration of butorphanol, fentanyl, and ketamine caused neurohormonal and metabolic changes similar to stress, including increased plasma epinephrine, cortisol, and glucose concentrations. The hyperglycemic effect of butorphanol was not significant. Ketamine caused increased norepinephrine concentration. Epinephrine concentration was correlated with glucose concentration in the butorphanol and fentanyl groups but not in the ketamine groups, suggesting an important difference between the mechanisms of the hyperglycemic effects of these drugs. Medetomidine prevented most of these effects except for hyperglycemia. Plasma glucose concentrations were lower in the combined sedation groups than in the medetomidine-saline solution group. CONCLUSIONS AND CLINICAL RELEVANCE: Opioids or ketamine used alone may cause changes in stress-related biochemical variables in plasma. Medetomidine prevented or blunted these changes. Combined sedation provided better hormonal and metabolic stability than either component alone. We recommend using medetomidine-butorphanol or medetomidine-ketamine combinations for sedation or anesthesia of systemically healthy dogs.  相似文献   

14.
OBJECTIVE: To compare the perioperative stress response in dogs administered medetomidine or acepromazine as part of the preanesthetic medication. ANIMALS: 42 client-owned dogs that underwent elective ovariohysterectomy. PROCEDURE: Each dog was randomly allocated to receive medetomidine and butorphanol tartrate (20 microgram/kg and 0.2 mg/kg, respectively, IM) or acepromazine maleate and butorphanol (0.05 and 0.2 mg/kg, respectively, IM) for preanesthetic medication. Approximately 80 minutes later, anesthesia was induced by administration of propofol and maintained by use of isoflurane in oxygen. Each dog was also given carprofen before surgery and buprenorphine after surgery. Plasma concentrations of epinephrine, norepinephrine, cortisol, and beta-endorphin were measured at various stages during the perioperative period. In addition, cardiovascular and clinical variables were monitored. RESULTS: Concentrations of epinephrine, norepinephrine, and cortisol were significantly lower for dogs administered medetomidine. Concentrations of beta-endorphin did not differ between the 2 groups. Heart rate was significantly lower and mean arterial blood pressure significantly higher in dogs administered medetomidine, compared with values for dogs administered acepromazine. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that for preanesthetic medications, medetomidine may offer some advantages over acepromazine with respect to the ability to decrease perioperative concentrations of stress-related hormones. In particular, the ability to provide stable plasma catecholamine concentrations may help to attenuate perioperative activation of the sympathetic nervous system.  相似文献   

15.
OBJECTIVE-To compare the effect of oral administration of tramadol alone and with IV administration of butorphanol or hydromorphone on the minimum alveolar concentration (MAC) of sevoflurane in cats. DESIGN-Crossover study. ANIMALS-8 Healthy 3-year-old cats. PROCEDURES-Cats were anesthetized with sevoflurane in 100% oxygen. A standard tail clamp method was used to determine the MAC of sevoflurane following administration of tramadol (8.6 to 11.6 mg/kg [3.6 to 5.3 mg/lb], PO, 5 minutes before induction of anesthesia), butorphanol (0.4 mg/kg [0.18 mg/lb], IV, 30 minutes after induction), hydromorphone (0.1 mg/kg [0.04 mg/lb], IV, 30 minutes after induction), saline (0.9% NaCl) solution (0.05 mL/kg [0.023 mL/lb], IV, 30 minutes after induction), or tramadol with butorphanol or with hydromorphone (same doses and routes of administration). Naloxone (0.02 mg/kg [0.009 mg/lb], IV) was used to reverse the effects of treatments, and MACs were redetermined. RESULTS-Mean +/- SEM MACs for sevoflurane after administration of tramadol (1.48 +/- 0.20%), butorphanol (1.20 +/- 0.16%), hydromorphone (1.76 +/- 0.15%), tramadol and butorphanol (1.48 +/- 0.20%), and tramadol and hydromorphone (1.85 +/- 0.20%) were significantly less than those after administration of saline solution (2.45 +/- 0.22%). Naloxone reversed the reductions in MACs. CONCLUSIONS AND CLINICAL RELEVANCE-Administration of tramadol, butorphanol, or hydromorphone reduced the MAC of sevoflurane in cats, compared with that in cats treated with saline solution. The reductions detected were likely mediated by effects of the drugs on opioid receptors. An additional reduction in MAC was not detected when tramadol was administered with butorphanol or hydromorphone.  相似文献   

16.
OBJECTIVE: To determine the pharmacokinetics of ketamine and norketamine in isoflurane-anesthetized dogs. Animals-6 dogs. PROCEDURE: The minimum alveolar concentration (MAC) of isoflurane was determined in each dog. Isoflurane concentration was then set at 0.75 times the individual's MAC, and ketamine (3 mg/kg) was administered IV. Blood samples were collected at various times following ketamine administration. Blood was immediately centrifuged, and the plasma separated and frozen until analyzed. Ketamine and norketamine concentrations were measured in the plasma samples by use of liquid chromatography-mass spectrometry. Ketamine concentration-time data were fitted to compartment models. Norketamine concentration-time data were examined by use of noncompartmental analysis. RESULTS: The MAC of isoflurane was 1.43 +/- 0.18% (mean +/- SD). A 2-compartment model best described the disposition of ketamine. The apparent volume of distribution of the central compartment, the apparent volume of distribution at steady state, and the clearance were 371.3 +/- 162 mL/kg, 4,060.3 +/- 2,405.7 mL/kg, and 58.2 +/- 17.3 mL/min/kg, respectively. Norketamine rapidly appeared in plasma following ketamine administration and had a terminal half-life of 63.6 +/- 23.9 minutes. A large variability in plasma concentrations, and therefore pharmacokinetic parameters, was observed among dogs for ketamine and norketamine. CONCLUSIONS AND CLINICAL RELEVANCE: In isofluraneanesthetized dogs, a high variability in the disposition of ketamine appears to exist among individuals. The disposition of ketamine may be difficult to predict in clinical patients.  相似文献   

17.
The effects of epidural and intravenous (IV) methadone (0.5mg/kg) on the minimum alveolar concentration of isoflurane (ISO(MAC)) were compared in dogs. Six dogs (16.5 ± 2.5 kg bodyweight) received three treatments in random order during isoflurane anaesthesia, with a 7 day washout interval between each study. Methadone was injected via a lumbosacral epidural catheter introduced 10 cm cranially into the epidural canal and the electrical stimulation for ISO(MAC) determination was applied either to the thoracic (EP(T) treatment) or to the pelvic limb (EP(P) treatment) during separate study days. In the IV treatment, ISO(MAC) was determined via electrical stimulation of the pelvic limb. Variables were recorded before (baseline), 2.5 and 5h after drug injection. The ISO(MAC) decreased significantly (P<0.05) from baseline at 2.5 and 5h after methadone in all treatments. At 2.5h, the magnitude of ISO(MAC) reduction did not differ between treatments (mean decreases from baseline: 30-33%). The ISO(MAC) reduction lasted longer following epidural methadone in the thoracic limb (decreases from baseline: 30% at 5h in the EP(T) treatment vs. 19% and 16% in the EP(P) and IV treatments, respectively). Although the isoflurane sparing effect provided by epidural methadone was not significantly greater than IV methadone during the initial stage (2.5h), it was more prolonged than the IV route in specific dermatomes (5h in the thoracic limb) with the epidural technique employed. Methadone may therefore provide a greater isoflurane sparing effect when administered epidurally, compared to IV, when noxious stimulation occurs in specific dermatomes.  相似文献   

18.
Objective-To evaluate the effects of epidural administration of 3 doses of dexmedetomidine on isoflurane minimum alveolar concentration (MAC) and characterize changes in bispectral index (BIS) induced by nociceptive stimulation used for MAC determination in dogs. Animals-6 adult dogs. Procedures-Isoflurane-anesthetized dogs received physiologic saline (0.9% NaCl) solution (control treatment) or dexmedetomidine (1.5 [DEX1.5], 3.0 [DEX3], or 6.0 [DEX6] mug/kg) epidurally in a crossover study. Isoflurane MAC (determined by use of electrical nociceptive stimulation of the hind limb) was targeted to be accomplished at 2 and 4.5 hours. Changes in BIS attributable to nociceptive stimulation and cardiopulmonary data were recorded at each MAC determination. Results-With the control treatment, mean +/- SD MAC values did not change over time (1.57 +/- 0.23% and 1.55 +/- 0.25% at 2 and 4.5 hours, respectively). Compared with the control treatment, MAC was significantly lower at 2 hours (13% reduction) but not at 4.5 hours (7% reduction) in DEX1.5-treated dogs and significantly lower at 2 hours (29% reduction) and 4.5 hours (13% reduction) in DEX3-treated dogs. The DEX6 treatment yielded the greatest MAC reduction (31% and 22% at 2 and 4.5 hours, respectively). During all treatments, noxious stimulation increased BIS; but changes in BIS were correlated with increases in electromyographic activity. Conclusions and Clinical Relevance-In dogs, epidural administration of dexmedetomidine resulted in dose-dependent decreases in isoflurane MAC and that effect decreased over time. Changes in BIS during MAC determinations may not represent increased awareness because of the possible interference of electromyographic activity.  相似文献   

19.
OBJECTIVE: To determine minimum alveolar concentration (MAC) of isoflurane in green iguanas and effects of butorphanol on MAC. DESIGN: Prospective randomized trial. ANIMALS: 10 healthy mature iguanas. PROCEDURE: in each iguana, MAC was measured 3 times: twice after induction of anesthesia with isoflurane and once after induction of anesthesia with isoflurane and IM administration of butorphanol (1 mg/kg [0.45 mg/lb]). A blood sample was collected from the tail vein for blood-gas analysis at the beginning and end of the anesthetic period. The MAC was determined with a standard bracketing technique; an electrical current was used as the supramaximal stimulus. Animals were artificially ventilated with a ventilator set to deliver a tidal volume of 30 mL/kg (14 mL/lb) at a rate of 4 breaths/min. RESULTS: Mean +/- SD MAC values during the 3 trials (2 without and 1 with butorphanol) were 2.0 +/- 0.6, 2.1 +/- 0.6, and 1.7 +/- 0.7%, respectively, which were not significantly different from each other. Heart rate and end-tidal partial pressure of CO2 were also not significantly different among the 3 trials. Mean +/- SD heart rate was 48 +/- 10 beats/min; mean end-tidal partial pressure of CO2 was 22 +/- 10 mm Hg.There were no significant differences in blood-gas values for samples obtained at the beginning versus the end of the anesthetic period. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the MAC of isoflurane in green iguanas is 2.1% and that butorphanol does not have any significant isoflurane-sparing effects.  相似文献   

20.
OBJECTIVE: To determine the cardiac anesthetic index (CAI) of isoflurane in green iguanas and whether butorphanol affected the CAI. DESIGN: Prospective randomized controlled trial. ANIMALS: 7 healthy mature iguanas. PROCEDURE: In 5 iguanas, CAI was determined after induction of anesthesia with isoflurane alone, and in 5 iguanas, CAI was determined after induction of anesthesia with isoflurane and IM administration of butorphanol (1 mg/kg [0.45 mg/lb]). Three iguanas underwent both treatments. Animals were equilibrated for 20 minutes at 1.5 times the minimum alveolar concentration (MAC) of isoflurane and observed for evidence of cardiovascular arrest. If there was no evidence of cardiovascular arrest, end-tidal isoflurane concentration was increased by 20%, and animals were allowed to equilibrate for another 20 minutes. This process was repeated until cardiovascular arrest occurred or vaporizer output could no longer be consistently increased. The CAI was calculated by dividing the highest end-tidal isoflurane concentration by the MAC. RESULTS: None of the iguanas developed cardiovascular arrest and all survived. Mean +/- SD highest end-tidal isoflurane concentration during anesthesia with isoflurane alone (9.2 +/- 0.60%) was not significantly different from mean concentration during anesthesia with isoflurane and butorphanol (9.0 +/- 0.43%). The CAI was > 4.32. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that the CAI of isoflurane in green iguanas is > 4.32 and not affected by administration of butorphanol. Isoflurane appears to be a safe anesthetic in green iguanas.  相似文献   

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