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1.
ObjectiveTo evaluate the effect of tramadol on sevoflurane minimum alveolar concentration (MACSEVO) in dogs. It was hypothesized that tramadol would dose-dependently decrease MACSEVO.Study designRandomized crossover experimental study.AnimalsSix healthy, adult female mixed-breed dogs (24.2 ± 2.6 kg).MethodsEach dog was studied on two occasions with a 7-day washout period. Anesthesia was induced using sevoflurane delivered via a mask. Baseline MAC (MACB) was determined starting 45 minutes after tracheal intubation. A noxious stimulus (50 V, 50 Hz, 10 ms) was applied subcutaneously over the mid-humeral area. If purposeful movement occurred, the end-tidal sevoflurane was increased by 0.1%; otherwise, it was decreased by 0.1%, and the stimulus was re-applied after a 20-minute equilibration. After MACB determination, dogs randomly received a tramadol loading dose of either 1.5 mg kg?1 followed by a continuous rate infusion (CRI) of 1.3 mg kg?1 hour?1 (T1) or 3 mg kg?1 followed by a 2.6 mg kg?1 hour?1 CRI (T2). Post-treatment MAC determination (MACT) began 45 minutes after starting the CRI. Data were analyzed using a mixed model anova to determine the effect of treatment on percentage change in baseline MACSEVO (p < 0.05).ResultsThe MACB values were 1.80 ± 0.3 and 1.75 ± 0.2 for T1 and T2, respectively, and did not differ significantly. MACT decreased by 26 ± 8% for T1 and 36 ± 12% for T2. However, there was no statistically significant difference in the decrease between the two treatments.Conclusion and clinical relevanceTramadol significantly reduced MACSEVO but this was not dose dependent at the doses studied.  相似文献   

2.
ObjectiveThe objectives of this study were to determine the effects of fentanyl on the end-tidal concentration of sevoflurane needed to prevent motor movement (MACNM) in response to noxious stimulation, and to evaluate if acute tolerance develops.Study designRandomized cross-over experimental study.AnimalsSix healthy, adult (2–3 years old), intact male, mixed-breed dogs weighing 16.2 ± 1.1 kg.MethodsSix dogs were randomly assigned to receive one of three separate treatments over a 3 week period. After baseline sevoflurane MACNM (MACNM-B) determination, fentanyl treatments (T) were administered as a loading dose (Ld) and constant rate infusion (CRI) as follows: T1-Ld of 7.5 μg kg?1 and CRI at 3 μg kg?1 hour?1; T2-Ld of 15 μg kg?1 and CRI at 6.0 μg kg ?1 hour?1; T3-Ld of 30 μg kg?1 and CRI at 12 μg kg?1 hour?1. The MACNM was defined as the minimum end-tidal sevoflurane concentration preventing motor movement. The first post-treatment MACNM (MACNM-I) determination was initiated 90 minutes after the start of the CRI, and a second MACNM (MACNM-II) determination was initiated 3 hours after MACNM-I was established.ResultsThe overall least square mean MACNM-B for all groups was 2.66%. All treatments decreased (p < 0.05) MACNM, and the decrease from baseline was 22%, 35% and 41% for T1, T2 and T3, respectively. Percentage change in T1 differed (p < 0.05) from T2 and T3; however, T2 did not differ from T3. MACNM-I was not significantly different from MACNM-II within treatments.Conclusions and clinical relevanceFentanyl doses in the range of 3–12 μg kg?1 hour?1 significantly decreased the sevoflurane MACNM. Clinically significant tolerance to fentanyl did not occur under the study conditions.  相似文献   

3.
ObjectiveTo compare the effects of continuous rate infusions (CRIs) of intravenous (IV) morphine and morphine-tramadol on the minimum alveolar concentration (MAC) of sevoflurane, and on electroencephalographic entropy indices in dogs.DesignProspective study.AnimalsEight young, healthy German shepherds, weighing 26.3 ± 3.1 kg (mean ± SD).MethodsAnaesthesia was induced and maintained with sevoflurane. A standard tail-clamp technique was used for MAC determination. Within one anaesthetic period, MAC was first determined during sevoflurane anaesthesia alone (MACB); then during morphine infusion (MACM), (loading dose 0.5 mg kg−1IM; CRI, 0.2 mg kg−1hour−1) then finally during morphine-tramadol infusion (tramadol loading dose 1.5 mg kg−1IV; CRI, 2.6 mg kg−1 hour−1) (MACMT). At each change, periods of 45 minutes were allowed for equilibration. Stated entropy (SE), response entropy (RE), and RE-SE differences were measured five minutes prior to and during tail clamping.ResultsThe MACB was 2.1 ± 0.3vol%. The morphine and morphine-tramadol infusions reduced MAC to 1.6 ± 0.3vol% and 1.3 ± 0.3vol%, respectively. MAC was decreased below baseline more during morphine-tramadol than during morphine alone (39 ± 9% versus 25 ± 6%, respectively; p = 0.003). All SE and RE and most RE-SE differences were increased significantly (p < 0.05) over pre-stimulation in all groups when the dogs responded purposefully to noxious stimulation. When no response to noxious stimulation occurred, the entropy indices did not change.Conclusion and clinical relevanceIn dogs, combined morphine-tramadol CRI decreased sevoflurane MAC more than morphine CRI alone. Entropy indices changed during nociceptive responses in anaesthetized animals, suggesting that entropy measurements may be useful in determining anaesthetic depth in dogs.  相似文献   

4.
ObjectiveTo compare the effects of a constant rate infusion (CRI) of dexmedetomidine and morphine to those of morphine alone on the minimum end-tidal sevoflurane concentration necessary to prevent movement (MACNM) in ponies.Study designProspective, randomized, crossover, ‘blinded’, experimental study.AnimalsFive healthy adult gelding ponies were anaesthetized twice with a 3-week washout period.MethodsAfter induction of anaesthesia with sevoflurane in oxygen (via nasotracheal tube), the ponies were positioned on a surgical table (T0), and anaesthesia was maintained with sevoflurane (Fe‘SEVO 2.5%) in 55% oxygen. Monitoring included pulse oximetry, electrocardiography and measurement of anaesthetic gases, arterial blood pressure and body temperature. The ponies were mechanically ventilated and randomly allocated to receive IV treatment M [morphine 0.15 mg kg?1 (T10-T15) followed by a CRI (0.1 mg kg?1 hour?1)] or treatment DM [dexmedetomidine 3.5 μg kg?1 plus morphine 0.15 mg kg?1 (T10-T15) followed by a CRI of dexmedetomidine 1.75 μg kg?1 hour?1 and morphine 0.1 mg kg?1 hour?1]. At T60, a stepwise MACNM determination was initiated using constant current electrical stimuli at the skin of the lateral pastern region. Triplicate MACNM estimations were obtained and then averaged in each pony. Wilcoxon signed-rank test was used to detect differences in MAC between treatments (a = 0.05).ResultsSevoflurane-morphine MACNM values (median (range) and mean ± SD) were 2.56 (2.01–4.07) and 2.79 ± 0.73%. The addition of a continuous infusion of dexmedetomidine significantly reduced sevoflurane MACNM values to 0.89 (0.62–1.05) and 0.89 ± 0.22% (mean MACNM reduction 67 ± 11%).Conclusion and clinical relevanceCo-administration of dexmedetomidine and morphine CRIs significantly reduced the MACNM of sevoflurane compared with a CRI of morphine alone at the reported doses.  相似文献   

5.
ObjectiveTo evaluate the effects of intravenous lidocaine (L) and ketamine (K) alone and their combination (LK) on the minimum alveolar concentration (MAC) of sevoflurane (SEVO) in dogs.Study designProspective randomized, Latin-square experimental study.AnimalsSix, healthy, adult Beagles, 2 males, 4 females, weighing 7.8 – 12.8 kg.MethodsAnesthesia was induced with SEVO in oxygen delivered by face mask. The tracheas were intubated and the lungs ventilated to maintain normocapnia. Baseline minimum alveolar concentration of SEVO (MACB) was determined in duplicate for each dog using an electrical stimulus and then the treatment was initiated. Each dog received each of the following treatments, intravenously as a loading dose (LD) followed by a constant rate infusion (CRI): lidocaine (LD 2 mg kg−1, CRI 50 μg kg−1minute−1), lidocaine (LD 2 mg kg−1, CRI 100 μgkg−1 minute−1), lidocaine (LD 2 mg kg−1, CRI 200 μg kg−1 minute−1), ketamine (LD 3 mg kg−1, CRI 50 μg kg−1 minute−1), ketamine (LD 3 mgkg−1, CRI 100 μg kg−1 minute−1), or lidocaine (LD 2 mg kg−1, CRI 100 μg kg−1 minute−1) + ketamine (LD 3 mg kg−1, CRI 100 μg kg−1 minute−1) in combination. Post-treatment MAC (MACT) determination started 30 minutes after initiation of treatment.ResultsLeast squares mean ± SEM MACB of all groups was 1.9 ± 0.2%. Lidocaine infusions of 50, 100, and 200 μg kg−1 minute−1 significantly reduced MACB by 22.6%, 29.0%, and 39.6%, respectively. Ketamine infusions of 50 and 100 μg kg−1 minute−1 significantly reduced MACB by 40.0% and 44.7%, respectively. The combination of K and L significantly reduced MACB by 62.8%.Conclusions and clinical relevanceLidocaine and K, alone and in combination, decrease SEVO MAC in dogs. Their use, at the doses studied, provides a clinically important reduction in the concentration of SEVO during anesthesia in dogs.  相似文献   

6.
This study evaluated the effects of IV lidocaine (L) and ketamine (K), alone and in combination (LK), on the isoflurane MAC (ISOMAC) in goats. It was hypothesized that L and K would reduce ISOMAC and that the effect of LK would be additive. Eight adult goats (24–51 kg) were used in the study. Each goat was studied on four occasions, at weekly intervals, using a randomized crossover design. Anesthesia was induced with isoflurane (ISO) in O2 and goats were intubated and ventilated to normocapnia. End‐tidal ISO (ETISO) and CO2 were monitored with a calibrated infrared analyzer. Body temperature was maintained in the normal range using a heating pad. Approximately 45 minutes after intubation, and with the ETISO having been held constant for at least 20 minutes, determination of the baseline MAC (MACB) was initiated. A noxious stimulus, which consisted of clamping a claw between the jaws of a 10‐inch Vulsellum forceps, was administered for 60 seconds or until purposeful movement occurred. If purposeful movement occurred, the ETISO was increased by 0.1 vols% otherwise it was decreased by 0.1 vols% and the stimulus was reapplied following a 20 minute equilibration period. Following MACB determination treatments were administered as a loading dose (Ld) in 10 mL 0.9% NaCl over 3 minutes followed by a constant rate infusion to a final volume of 60 mL hour–1 in 0.9% NaCl, as follows: L (Ld 2.5 mg kg–1 + 100 μg kg–1 minutes–1); K (Ld 1.5 mg kg–1 + 50 μg kg–1minutes); LK or 0.9% NaCl. Post‐treatment MAC (MACT) determination began 45 minutes after the start of the loading dose. MACB and MACT were determined in triplicate and the mean value was used for data analysis. Difference in percent change in MAC was tested using a mixed‐model anova . Means separation among levels of treatment was tested using the Tukey‐Kramer method. The mean MACB for all treatments was 1.13 ± 0.03 vols%. L, K and LK reduced (p < 0.05) MACB by 19%, 49% and 69%, respectively. No change (p > 0.05) occurred with saline. It was concluded that L and K caused clinically significant decreases in ISOMAC; however, the percent MAC reduction with L was less than expected given the MAC reduction reported with L for other species. The combination (LK) caused a profound decrease in ISOMAC and this effect was additive.  相似文献   

7.
ObjectiveTo determine the effect of intravenous ketamine on the minimum alveolar concentration of sevoflurane needed to block autonomic response (MACBAR) to a noxious stimulus in dogs.Study designRandomized, crossover, prospective design.AnimalsEight, healthy, adult male, mixed-breed dogs, weighing 11.2–16.1 kg.MethodsDogs were anesthetized with sevoflurane on two occasions, 1 week apart, and baseline MACBAR (B-MACBAR) was determined on each occasion. MACBAR 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 MACBAR (T-MACBAR) 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-MACBAR 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.ResultsThe B-MACBAR was not significantly different between treatments. Ketamine at 12.5, 25, and 50 μg kg?1 minute?1 decreased sevoflurane MACBAR, and the maximal decrease (22%) occurred at 12.5 μg kg?1 minute?1. The percentage change in MACBAR was not correlated with either the log plasma ketamine or norketamine concentration.Conclusions and clinical relevanceKetamine at clinically relevant doses of 12.5, 25, and 50 μg kg?1 minute?1 decreased sevoflurane MACBAR, although the reduction was neither dose-dependent nor linear.  相似文献   

8.
ObjectiveTo determine the possible additive effect of midazolam, a GABAA agonist, on the end-tidal concentration of isoflurane that prevents movement (MACNM) in response to noxious stimulation.Study designRandomized cross-over experimental study.AnimalsSix healthy, adult intact male, mixed-breed dogs.MethodsAfter baseline isoflurane MACNM (MACNM-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). MACNM was re-determined after each dose in each series (MACNM-T).ResultsThe median MACNM-B was 1.42. MACNM-B did not differ among groups (p >0.05). Percentage reduction in MACNM 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 MACNM reduction (r = 0.36).Conclusion and clinical relevanceMidazolam doses in the range of 10–80 μg kg?1 minute?1 significantly reduced the isoflurane MACNM. However, doses greater than 10 μg kg?1 minute?1 did not further decrease MACNM indicating a ceiling effect.  相似文献   

9.
ObjectiveTo investigate the effects of methadone on the minimum alveolar concentration of isoflurane (ISOMAC) in dogs.Study designProspective, randomized cross-over experimental study.AnimalsSix adult mongrel dogs, four males and two females, weighing 22.8 ± 6.6 kg.MethodsAnimals were anesthetized with isoflurane and mechanically ventilated on three separate days, at least 1 week apart. Core temperature was maintained between 37.5 and 38.5 °C during ISOMAC determinations. On each study day, ISOMAC was determined using electrical stimulation of the antebrachium (50 V, 50 Hz, 10 mseconds) at 2.5 and 5 hours after intravenous injection of physiological saline (control) or one of two doses of methadone (0.5 or 1.0 mg kg?1).ResultsMean (±SD) ISOMAC in the control treatment was 1.19 ± 0.15% and 1.18 ± 0.15% at 2.5 and 5 hours, respectively. The 1.0 mg kg?1 dose of methadone reduced ISOMAC by 48% (2.5 hours) and by 30% (5 hours), whereas the 0.5 mg kg?1 dose caused smaller reductions in ISOMAC (35% and 15% reductions at 2.5 and 5 hours, respectively). Both doses of methadone decreased heart rate (HR), but the 1.0 mg kg?1 dose was associated with greater negative chronotropic actions (HR 37% lower than control) and mild metabolic acidosis at 2.5 hours. Mean arterial pressure increased in the MET1.0 treatment (13% higher than control) at 2.5 hours.Conclusions and clinical relevanceMethadone reduces ISOMAC in a dose-related fashion and this effect is lessened over time. Although the isoflurane sparing effect of the 0.5 mg kg?1 dose of methadone was smaller in comparison to the 1.0 mg kg?1 dose, the lower dose is recommended for clinical use because it results in less evidence of cardiovascular impairment.  相似文献   

10.
Reduction of isoflurane MAC by fentanyl or remifentanil in rats   总被引：2，自引：0，他引：2  
Objective The main objective of the study was to determine the effects of three different infusion rates of fentanyl and remifentanil on the minimum alveolar concentration (MAC) of isoflurane in the rat. A secondary objective was to assess the cardiovascular and respiratory effects of the two opioid drugs. Animal population Thirty‐seven male Wistar rats were randomly allocated to one of six treatment groups. Material and methods For all treatment groups anaesthesia was induced with 5% isoflurane in oxygen using an induction chamber. A 14‐gauge catheter was used for endotracheal intubation, and anaesthesia was maintained with isoflurane delivered in oxygen via a T‐piece breathing system. A baseline determination of the minimum alveolar concentration of isoflurane (MACISO) was made for each animal. Fentanyl (15, 30, 60 µg kg?1 hour?1) or remifentanil (60, 120, 240 µg kg?1 hour?1) were infused intravenously into a previously cannulated tail vein. Thirty minutes after the infusion started, a second MACISO (MACISO+drug) was determined. The carotid artery was cannulated to monitor the arterial pressure and to take samples for arterial gas measurements. Cardiovascular (heart rate and arterial pressure) and respiratory (respiratory rate and presence/absence of apnoea) effects after opioid infusion were also recorded. Results Fentanyl (15, 30, 60 µg kg?1 hour?1) and remifentanil (60, 120, 240 µg kg?1 hour?1) similarly reduced isoflurane MAC in a dose‐dependent fashion: by 10% at lower doses, 25% at medium doses and by 60% at higher doses of both the drugs. Both opioids reduced the respiratory rate in a similar way for all doses tested. No episodes of apnoea were recorded in the remifentanil groups, while administration of fentanyl resulted in apnoea in three animals (one at each dose level). The effects on the cardiovascular system were similar with both drugs. Conclusions We conclude that the intraoperative use of remifentanil in the rat reduces the MAC of isoflurane, and that this anaesthetic sparing effect is dose‐dependent and similar to that produced by fentanyl at the doses tested. Clinical relevance The use of remifentanil during inhalant anaesthesia in the rat can be considered an intravenous alternative to fentanyl, providing similar reduction in isoflurane requirements. Due to its rapid offset, it is recommended that alternative pain relief be instituted before it is discontinued.  相似文献   

11.
Objective To compare the efficacy of epidural buprenorphine with epidural morphine for post‐operative pain relief in dogs undergoing cranial cruciate ligament rupture repair. Study design A randomized, double blind clinical trial. Animals Twenty client‐owned dogs with cranial cruciate ligament rupture. Methods Dogs were randomly assigned to receive either epidural buprenorphine (4 µg kg?1) or epidural morphine (0.1 mg kg?1) in a total volume of 0.2 mL kg?1. Epidural injections were performed immediately after induction of anesthesia. End‐tidal halothane and CO2 were recorded every 15 minutes from the time of epidural administration of drug to extubation. A numerical rating pain score system was used by a blinded observer to evaluate analgesia beginning at extubation and continuing at specific intervals for 24 hours after surgery. Heart rate, respiratory rate, and blood pressure were recorded noninvasively at the same times. If pain score indicated moderate discomfort, rescue morphine at 1.0 mg kg?1 was administered intramuscularly. Results There were no significant differences between groups with respect to pain score, heart rate, respiratory rate, indirect blood pressure, end‐tidal halothane or end‐tidal CO2 at any time point. Fifty percent of dogs in the buprenorphine group and 50% of dogs in the morphine group required rescue analgesic medication. Time of systemic rescue morphine administration did not differ significantly between the two groups. There were no clinically observable side‐effects from epidural administration of either drug in any of the dogs of this study. Conclusions Epidural buprenorphine is as effective as epidural morphine for the relief of postoperative hindlimb orthopedic pain in dogs. Clinical relevance Buprenorphine appears to be an effective opioid for epidural use in healthy dogs. Buprenorphine may offer certain advantages over morphine for epidural use, such as lower abuse potential and, in some clinics, reduced cost and less wastage of drug.  相似文献   

12.
Lidocaine decreases minimum alveolar concentration (MAC) of inhalational anesthetics. This study determined the influence of a low dose, 50 µg kg?1 minute?1 (LDI) and high dose, 200 µg kg?1 minute?1 (HDI) constant rate infusion of lidocaine on the MAC of isoflurane (I) in dogs. Ten mongrel dogs were anesthetized with I in oxygen and mechanically ventilated. End‐tidal anesthetic (Fe ′A) and CO2 (Pe ′CO2) concentrations were monitored at the endotracheal tube adaptor with an infrared gas analyzer calibrated before each experiment with a standardized calibration gas mixture designed for the analyzer. Pe ′CO2 and body temperature were maintained within normal limits. Noxious stimuli included clamping the hindlimb paw (HC) and electrical current (50 V at 50 cycles second?1 for 10 milliseconds pulse?1) applied subcutaneously to the forelimb (FE) at the level of the ulna. After an initial equilibration period of at least 40 minutes at an Fe ′A of 1.7%, the Fe ′A was decreased to a value close to the estimated MAC for dogs. MAC was defined as the Fe ′A mid‐way between the value permitting and preventing purposeful movement. Following baseline MAC, a loading dose of 2 mg kg?1 of lidocaine IV was administered over 3 minutes followed by the LDI, and MAC determinations for the combination started after 30 minutes of infusion. Once determined, the lidocaine infusion was stopped for 30 minutes and the dog maintained at the ETC that prevented movement without the lidocaine. Following this period, a second loading dose of lidocaine was given (2 mg kg?1) over 3 minutes followed by the HDI, and the MAC determination procedure repeated after 30 minutes of infusion. Data were analyzed using an anova for repeated measures. MAC of I was 1.34 ± 0.035% (mean ± SEM) for both the FE and HC stimuli. The LDI significantly decreased MAC to 1.09 ± 0.043% (18.7% reduction) and HDI to 0.76 ± 0.030% (43.3% reduction). In conclusion, lidocaine infusions decreased the MAC of isoflurane in a dose‐dependent manner.  相似文献   

13.
ObjectiveTo determine which class of opioid alone or in conjunction with other anesthetic drugs causes post-anesthetic hyperthermia in cats.Study designProspective, randomized, crossover study.AnimalsEight adult, healthy, cats (four spayed females and four castrated males weighing 3.8 ± 0.6 kg).MethodsEach cat was instrumented with a wireless thermistor in the abdominal cavity. Temperature in all phases was recorded every 5 minutes for 5 hours. Population body temperature (PBT) was recorded for ～8 days. Baseline body temperature is the final 24 hours of the PBT. All injectable drugs were given intramuscularly. The cats were administered drugs in four phases: 1) hydromorphone (H) 0.05, 0.1, or 0.2 mg kg?1; 2) morphine (M) (0.5 mg kg?1), buprenorphine (BUP) (0.02 mg kg?1), or butorphanol (BUT) (0.2 mg kg?1); 3) ketamine (K) (5 mg kg?1) or ketamine (5 mg kg?1) plus hydromorphone (0.1 mg kg?1) (KH); 4) isoflurane in oxygen for 1 hour. Fifteen minutes prior to inhalant anesthetic, cats received either no premed (I), hydromorphone (0.1 mg kg?1) (IH), or hydromorphone (0.1 mg kg?1) plus ketamine (5 mg kg?1) (IHK).ResultsMean PBT for all unmedicated cats was 38.9 ± 0.6 °C (102.0 ± 1 °F). The temperature of cats administered all doses of hydromorphone increased from baseline (p < 0.03) All four opioids (H, M, BUP and BUT) studied increased body temperature compared with baseline (p < 0.005). A significant difference was observed between baseline temperature values and those in treatment KH (p < 0.03). Following recovery from anesthesia, temperature in treatments IH and IHK was different from baseline (p < 0.002).Conclusions and clinical relevanceAll of the opioids tested, alone or in combination with ketamine or isoflurane, caused an increase in body temperature. The increase seen was mild to moderate (<40.1 °C (104.2 °F) and self limiting.  相似文献   

14.
ObjectiveTo evaluate the effects of constant rate infusions (CRIs) of dexmedetomidine and remifentanil alone and their combination on minimum alveolar concentration (MAC) of sevoflurane in dogs.Study designRandomized crossover experimental study.AnimalsA total of six (three males, three females) healthy, adult neutered Beagle dogs weighing 12.6 ± 1.4 kg.MethodsAnesthesia was induced with sevoflurane in oxygen until endotracheal intubation was possible and anesthesia maintained with sevoflurane using positive-pressure ventilation. Each dog was anesthetized five times and was administered each of the following treatments: saline (1 mL kg–1 hour–1) or dexmedetomidine at 0.1, 0.5, 1.0 or 5.0 μg kg–1 loading dose intravenously over 10 minutes followed by CRI at 0.1, 0.5, 1.0 or 5.0 μg kg–1 hour–1, respectively. Following 60 minutes of CRI, sevoflurane MAC was determined in duplicate using an electrical stimulus (50 V, 50 Hz, 10 ms). Then, CRI of successively increasing doses of remifentanil (0.15, 0.60 and 2.40 μg kg–1 minute–1) was added to each treatment. MAC was also determined after 30 minutes equilibration at each remifentanil dose. Isobolographic analysis determined interaction from the predicted doses required for a 50% MAC reduction (ED50) with remifentanil, dexmedetomidine and remifentanil combined with dexmedetomidine, with the exception of dexmedetomidine 5.0 μg kg–1 hour–1, obtained using log-linear regression analysis.ResultsThe sevoflurane MAC decreased dose-dependently with increasing infusion rates of dexmedetomidine and remifentanil. Remifentanil ED50 values were lower when combined with dexmedetomidine than those obtained during saline–remifentanil. Synergistic interactions between dexmedetomidine and remifentanil for MAC reduction occurred with dexmedetomidine at 0.5 and 1.0 μg kg–1 hour–1.Conclusions and clinical relevanceCombined CRIs of dexmedetomidine and remifentanil synergistically resulted in sevoflurane MAC reduction. The combination of dexmedetomidine and remifentanil effectively reduced the requirement of sevoflurane during anesthesia in dogs.  相似文献   

15.
ObjectiveTo determine the effect of maropitant, an NK-1 receptor antagonist on the minimum alveolar concentration (MAC) of sevoflurane after intravenous and epidural administration to dogs.Study designProspective experimental study.AnimalsSeven, adult, spayed-female dogs (24.8 ± 1.9 kg).MethodsEach dog was anesthetized twice with sevoflurane in oxygen, with at least 10 days separating the anesthetic events. The minimum alveolar concentration (MAC) of sevoflurane was determined using the tail-clamp technique. During the first anesthetic event, the MAC of sevoflurane was determined initially and again after intravenous administration of maropitant (5 mg kg?1) and an infusion (150 μg kg?1 hour?1). During the second anesthetic event, an epidural catheter was advanced to the 4th lumbar vertebra and MAC was determined after administration of saline and maropitant (1 mg kg?1) epidurally. All MAC determinations were done in duplicate. The MAC values were adjusted to sea level and compared using student's t-test.ResultsThe baseline MAC for sevoflurane was 2.08 ± 0.25%. Intravenous maropitant decreased (p < 0.05) MAC by 16% (1.74 ± 0.17%). In contrast, epidural administration of either saline or maropitant did not change (p > 0.05) the MAC (2.17 ± 0.34% and 1.92 ± 0.12%, respectively).Conclusion and clinical relevanceMaropitant decreased the MAC of sevoflurane when administered intravenously to dogs but not after epidural administration.  相似文献   

16.
ObjectiveTo determine the effect of fentanyl on the minimum alveolar concentration of isoflurane (MACISO) and cardiovascular variables in dogs, and how the treatment of bradycardia affects them.Study designProspective, randomized crossover-controlled trial.AnimalsA total of six male Beagle dogs weighing 9.9 ± 0.7 kg (mean ± standard deviation) and aged 13 months.MethodsTo each dog, two treatments were assigned on different days: fentanyl (FENTA) or fentanyl plus glycopyrrolate (FENTAglyco) to maintain heart rate (HR) between 100 and 132 beats minute?1. Determinations of MACISO were performed with 10 plasma fentanyl target concentrations ([Fenta]Target (0, 0.16, 0.32, 0.64, 1.25, 2.5, 5.0, 10.0, 20.0 and 40.0 ng mL?1) for FENTA and 5 [Fenta]Target (0, 1.25, 2.5, 5.0, 10.0 ng mL?1)) for FENTAglyco. During each MACISO determination, cardiovascular variables [mean arterial pressure (MAP), HR and cardiac index (CI)] were measured, and systemic vascular resistance index (SVRI) calculated. Pharmacodynamic models were used to describe the plasma fentanyl concentration [Fenta]–response relationship for the effect on MACISO and cardiovascular variables. A mixed-model analysis of variance followed by Dunnett’s or Tukey’s test, and the Bonferroni adjustment were used for comparisons within and between each treatment, respectively. Significance was set as p < 0.05.ResultsFentanyl decreased MACISO by a maximum of 84%. The [Fenta] producing 50% decrease in MAC, HR and CI were 2.64, 3.65 and 4.30 ng mL?1 (typical values of population model), respectively. The prevention of fentanyl-mediated bradycardia caused no significant effect on MACISO, but increased HR, MAP and CI, and decreased SVRI when compared with isoflurane alone.Conclusions and clinical relevanceFentanyl caused a plasma concentration-dependent decrease in MACISO, HR and CI and an increase in SVRI. Cardiovascular improvements associated with fentanyl in isoflurane-anesthetized dogs only occurred when the fentanyl-mediated bradycardia was prevented.  相似文献   

17.
Little is known about the analgesic action of buprenorphine (BUP) in cats. Relative to man, the cat has a more alkaline oral pH, which may make this an effective route for administering BUP in this species. This study aimed to assess and compare the pharmacokinetics and pharmacodynamics of sublingual (S‐L) and IV administration of BUP. Thermal threshold (TT) was measured and blood samples were collected following IV or S‐L administration (20 µg kg?1) of the injectable formulation. Six cats (five spayed females, one castrated male, 4.1–6.6 kg) were used. Each cat received both treatments in a randomized cross‐over study design with 1 month between experiments. Twenty‐four hours prior to each study, the lateral thorax of each of the cats was shaved, cephalic and jugular catheters placed, and oral pH measured. On the day of the study, TT was measured using a ‘thorax‐mounted’ thermal threshold‐testing device specifically developed for cats. The cats were free to move around. Skin temperature was recorded before each test, then the heater activated. When the cat responded by flinching, turning, or jumping, the stimulus was terminated and the threshold temperature was recorded. The thermal threshold cut‐off point was 55.5 °C. Three baseline thresholds were recorded before treatment with S‐L or IV (via cephalic catheter) BUP (20 µg kg?1). Blood was withdrawn (jugular) at 1, 2, 4, 6, 10, 15, 30, 45, 60 minutes and at 2, 4, 6, 8, 12, and 24 hours post‐administration. TT was measured every 30 minutes?6 hours, 1–12 hours, and at 24 hours post‐administration. Plasma was immediately separated, stored at ?20.5 °C, and assayed within 4 months using a commercially available 125I radioimmunoassay. Threshold data were analyzed using anova with a repeat factor of time. No adverse effects were noted. Pupils were dilated for up to 9 hours post‐BUP. Behavioral changes were calm euphoria. Measured oral pH was 9 in each cat. Pre‐treatment mean threshold (±SD) was 41.2 ± 0.9 °C in the S‐L group and 40.8 ± 0.85 °C in the IV group. There were no significant differences between the groups with respect to thresholds over time (p = 0.72). Thresholds were significantly increased from 30 to 360 minutes in both the groups (>44.615 °C). Peak plasma BUP (Cmax) was lower (11 ± 6.7 ng mL?1vs. 92.9 ± 107.9 ng mL?1) and occurred later (Tmax) (30 minutes vs. 1 minute) after S‐L compared to IV administration, respectively. BUP (20 µg kg?1)‐administered S‐L or IV provided antinociception between 30 and 360 minutes after administration. Plasma levels did not correspond to TT.  相似文献   

18.

Objective

To characterize the isoflurane-sparing effects of a high and a low dose of fentanyl in dogs, and its effects on mean arterial pressure (MAP) and heart rate (HR).

Study design

Prospective, randomized crossover trial.

Animals

Eight healthy male Beagle dogs weighing 12.1 ± 1.6 kg [mean ± standard deviation (SD)] and approximate age 1 year.

Methods

Dogs were anesthetized using isoflurane and minimum alveolar concentration (MAC) was determined in duplicate by the bracketing method using an electrical stimulus on the tarsus. Animals were administered fentanyl: low dose (33 μg kg?1 loading dose, 0.2 μg kg?1 minute?1) or high dose (102 μg kg?1 loading dose, 0.8 μg kg?1 minute?1) and MAC was re-determined (MACISO-F). Blood was collected for analysis of plasma fentanyl concentrations before administration and after MACISO-F determination. All values are presented as mean ± SD.

Results

Isoflurane MAC (MACISO) was 1.30 ± 0.23% in the low dose treatment, which significantly decreased to 0.75 ± 0.22% (average MAC reduction 42.3 ± 9.4%). MACISO was 1.30 ± 0.18% in the high dose treatment, which significantly decreased to 0.30 ± 0.11% (average MAC reduction 76.9 ± 7.4%). Mean fentanyl plasma concentrations were 6.2 and 29.5 ng mL?1 for low and high dose treatments, respectively. MAP increased significantly only in the high dose treatment (from 81 ± 8 to 92 ± 9 mmHg). HR decreased significantly in both treatments from 108 ± 25 to 61 ± 14 beats minute?1 with the low dose and from 95 ± 14 to 42 ± 4 beats minute?1 with the high dose.

Conclusions and clinical relevance

Fentanyl administration resulted in a dose-dependent isoflurane MAC-sparing effect with bradycardia at both doses and an increase in MAP only at high dose. Further evaluation is needed to determine the effects of fentanyl on the overall cardiovascular function.  相似文献   

19.
ObjectiveTo test the hypothesis that subarachnoid administration of buprenorphine and lidocaine provides more intense and longer lasting perioperative analgesia with less side effects than xylazine and lidocaine in goats.Study designRandomized, blinded, controlled study.Study animals Ten healthy female goats randomly assigned to two groups of five animals each.MethodsAfter sedation with acepromazine (0.1 mg kg?1) intravenously (IV), lidocaine 2% (0.1 mL kg?1) combined with either xylazine (0.05 mg kg?1; Group X) or buprenorphine (0.005 mg kg?1; Group B) were injected intrathecally at the lumbo-sacral junction prior to stifle surgery. Electrocardiogram, heart rate, direct systolic, mean, and diastolic arterial blood pressures, rectal temperature and arterial blood gases were recorded as were post-operative sedation and pain scores using a visual analogue and numeric rating scale, respectively. Data were analyzed with one-way anova for repeated measures, one-way anova, Friedman's and Kruskal–Wallis tests as necessary (p< 0.05).ResultsSurgery was successfully performed under both analgesia protocols. Total pain and sedation scores were significantly lower in the B as compared with X group from 3–24 hours and 30–120 minutes, respectively after subarachnoid drug administration (SDA). Heart rate and arterial blood pressures decreased post SDA and were consistently lower in X versus B (p< 0.05). In B arterial blood gas parameters did not change post SDA, but in group X PaCO2 increased slightly within 15 minutes of SDA and remained elevated for at least 3 hours (p< 0.05).ConclusionIn these goats intrathecal administration of buprenorphine and lidocaine produced more profound and longer lasting analgesia with less sedation and hemodynamic and respiratory impairment than xylazine with lidocaine.Clinical relevanceIn these goats undergoing hind limb surgery, subarachnoid buprenorphine/lidocaine offered more intense and longer lasting analgesia than a xylazine/lidocaine combination, with less sedation and impairment of cardiopulmonary function.  相似文献   

20.
Objectives To investigate the effects of levomepromazine and different desflurane concentrations upon electrocardiographic variables. Animals Twenty adult mongrel dogs of both sexes weighing 6–28 kg. Methods Dogs were divided into two groups of 10 animals. Group 1 received 1 mg kg?1 IV of levomepromazine and 15 minutes later anesthesia was induced with propofol (3 mg kg?1 IV). Desflurane end‐tidal concentration was set at 1.6 MAC. After 30 minutes at this concentration, measurements were taken and the end‐tidal concentration was reduced to 1.4 MAC. Thereafter, it was reduced to 1.2 and then 1.0 MAC at 15‐minute intervals. The same procedure was followed for group 2, except that levomepromazine was replaced with 0.2 mL kg?1 of 0.9% saline solution and more propofol was needed for induction (7 mg kg?1). The animals' body temperature was maintained between 38.3 and 39 °C using a heating pad. The electrocardiographic tracing was obtained from lead II throughout the experimental period. The measurements were taken immediately before the administration of levomepromazine or placebo (T1), 15 minutes after pre‐medication (T2) and 30 minutes after the establishment of 1.6 MAC (T3). The other measurements were made at the concentrations of 1.4, 1.2, and 1.0 MAC, respectively (T4?6). The numerical data were submitted to analysis of variance plus F‐test (p < 0.05). Results The dogs that received levomepromazine had a decrease in heart rate. However, in both groups it increased with desflurane administration. Levomepromazine, in association with desflurane, did not induce significant electrocardiographic changes, and all mean values (except P‐wave duration) were within the reference range for this species. Conclusions and clinical relevance This study documented that levomepromazine, in association with desflurane, does not induce significant changes in electrocardiographic variables, suggesting that this drug combination has minimal effect on myocardial conduction.  相似文献   

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