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1.

Objective

To evaluate the ability of a noninvasive cardiac output monitoring system with electrical velocimetry (EV) for predicting fluid responsiveness in dogs undergoing cardiac surgery.

Study design

Prospective experimental trial.

Animals

A total of 30 adult Beagle dogs.

Methods

Stroke volume (SV), stroke volume variation (SVV) and cardiac index were measured using the EV device in sevoflurane-anaesthetized, mechanically ventilated dogs undergoing thoracotomies for experimental creation of right ventricular failure. The dogs were considered fluid responsive if stroke volume (SVI; indexed to body weight), measured using pulmonary artery thermodilution, increased by 10% or more after volume loading (10 mL kg–1). Relationships of SVV, central venous pressure (CVP) and pulmonary artery occlusion pressure (PAOP) with SVI were analysed to estimate fluid responsiveness.

Results

Better prediction of fluid responsiveness, with a significant area under the receiver operating characteristic curve, was observed for SVV (0.85 ± 0.07; p = 0.0016) in comparison with CVP (0.65 ± 0.11; p = 0.17) or PAOP (0.60 ± 0.12; p = 0.35), with a cut-off value of 13.5% (84% specificity and 73% sensitivity).

Conclusions and clinical relevance

SVV derived from EV is useful for identification of dogs that are likely to respond to fluids, providing valuable information on volume status under cardiothoracic anaesthesia.  相似文献   

2.

Objective

To evaluate replicate effects and test–retest reliability of mechanical and thermal quantitative sensory testing (QST) in normal dogs and dogs with osteoarthritis (OA)-associated pain.

Study design

A prospective clinical study.

Animals

A total of 54 client owned dogs (OA, n = 31; controls, n = 23).

Methods

Mechanical [electronic von Frey (EVF) and blunt pressure] and thermal (hot and cold) sensory thresholds were obtained in dogs with OA-associated pain and control dogs at two visits, 7 days apart, to assess test–retest reliability. Thresholds were measured at the OA-affected joint (hip or stifle), over the tibial muscle and over the midpoint of the metatarsals. Five replicates were obtained for each modality at each site bilaterally.

Results

Overall, there was no significant effect of replicates on QST response. EVF thresholds were significantly lower at the second visit in OA dogs at the affected and metatarsal sites (p = 0.0017 and p = 0.0014, respectively). Similarly for control dogs, EVF thresholds were significantly lower at the second visit at the metatarsal site (p = 0.001). Significantly higher hot thermal latencies were seen in OA dogs at the affected and tibial testing sites (p = 0.014 and p = 0.012, respectively), and in control dogs at the tibial site (p = 0.004).

Conclusions

In QST, a replicate does not show a strong effect. However, QST results show variability over time, particularly for EVF and hot thermal stimuli.

Clinical relevance

If QST is to be used clinically to evaluate a sensitized state, the variability over time needs to be accounted for in the study design.  相似文献   

3.
4.
5.

Objective

Variants in the MC1R gene have been associated with red hair color and sensitivity to pain in humans. The study objective was to determine if a relationship exists between MC1R genotype and physiological thermal or mechanical nociceptive thresholds in Labrador Retriever dogs.

Study design

Prospective experimental study.

Animals

Thirty-four Labrador Retriever dogs were included in the study following public requests for volunteers. Owner consent was obtained and owners verified that their dog was apparently not experiencing pain and had not been treated for pain during the previous 14 days. The study was approved by the Institutional Animal Care and Use Committee.

Methods

Nociceptive thresholds were determined from a mean of three thermal and five mechanical replications using commercially available algometers. Each dog was genotyped for the previously described MC1R variant (R306ter). Data were analyzed using one-way anova with post hoc comparisons using Tukey’s test (p < 0.05).

Results

Thirteen dogs were homozygous wild-type (WT/WT), nine were heterozygous (WT/R306ter), and eight were homozygous variant (R306ter/R306ter) genotype. Four dogs could not be genotyped. A significant difference (p = 0.04) in mechanical nociceptive thresholds was identified between dogs with the WT/WT genotype (12.1 ± 2.1 N) and those with the WT/R306ter genotype (9.2 ± 2.4 N).

Conclusion

A difference in mechanical, but not thermal, nociceptive threshold was observed between wild-type and heterozygous MC1R variants. Differences in nociceptive thresholds between homozygous R306ter variants and other genotypes for MC1R were not observed.

Clinical relevance

Compared with the wild-type MC1R genotype, nociceptive sensitivity to mechanical force in dogs with a single variant R306ter allele may be greater. However, in contrast to the reported association between homozygous MC1R variants (associated with red hair color) and nociception in humans, we found no evidence of a similar relationship in dogs with the homozygous variant genotype.  相似文献   

6.

Objective

To determine the intubation dose and select physiologic effects of alfaxalone alone or in combination with midazolam or ketamine in dogs.

Study design

Prospective, clinical study.

Animals

Fifty-three healthy client-owned dogs [mean ± standard deviation (SD)] 5.1 ± 1.8 years, 27 ± 15.4 kg, scheduled for elective orthopedic surgery.

Methods

After premedication with acepromazine (0.02 mg kg–1) and hydromorphone (0.1 mg kg–1) intramuscularly, alfaxalone (0.25 mg kg–1) was administered intravenously over 15 seconds followed immediately by 0.9% saline (AS), midazolam (0.3 mg kg–1; AM), ketamine (1 mg kg–1; AK1), or ketamine (2 mg kg–1; AK2). Additional alfaxalone (0.25 mg kg–1 increments) was administered as required to permit endotracheal intubation. The incidence of apnea and the time from intubation until spontaneous movement were recorded. Heart rate (HR) and blood pressure were recorded 15 minutes after premedication, after intubation and 2, 5, 10 and 15 minutes thereafter. Blood was collected for measurement of serum glucose and insulin concentrations before induction, after intubation and at 2, 5, 10 and 50 minutes. Data were analyzed by split-plot anova with Bonferroni adjustment for the number of group comparisons.

Results

Mean ± SD alfaxalone mg kg–1 doses required for endotracheal intubation were AS (1.0 ± 0.4), AM (0.4 ± 0.2), AK1 (0.5 ± 0.3) and AK2 (0.5 ± 0.4) (p = 0.0005). Differences in cardiopulmonary variables among groups were minor; HR decreased in AS, while in other groups, HR increased transiently postintubation. Incidence of apnea in AS was 54% with no significant difference among groups. Midazolam significantly prolonged time from intubation until spontaneous movement (p < 0.002).

Conclusions and clinical relevance

Midazolam and ketamine reduced the alfaxalone dose required for endotracheal intubation. Serum glucose and insulin concentrations were not influenced by administration of alfaxalone alone or when administered with midazolam or ketamine.  相似文献   

7.

Objective

The aim of the study was to evaluate the influence of tramadol on acute nociception in dogs.

Study design

Experimental, blinded, randomized, crossover study.

Animals

Six healthy laboratory Beagle dogs.

Methods

Dogs received three treatments intravenously (IV): isotonic saline placebo (P), tramadol 1 mg kg?1 (T1) and tramadol 4 mg kg?1 (T4). Thermal thresholds were determined by ramped contact heat stimulation (0.6 °C second?1) at the lateral thoracic wall. Mechanical thresholds (MT) were measured using a probe containing three blunted pins which were constantly advanced over the radial bone, using a rate of force increase of 0.8 N second?1. Stimulation end points were defined responses (e.g. skin twitch, head turn, repositioning, vocalization) or pre-set cut-out values (55 °C, 20 N). Thresholds were determined before treatment and at predetermined time points up to 24 hours after treatment. At each measurement point, blood was collected for determination of O-desmethyltramadol concentrations. The degree of sedation and behavioural side effects were recorded. Data were analysed by one-way anova and two-way anova for repeated measurements.

Results

Thermal nociception was not influenced by drug treatment. Mechanical nociception was significantly increased between P and T1 at 120 and 240 minutes, and between P and T4 at 30, 60, 240 and 420 minutes. T1 and T4 did not differ. O-desmethyltramadol (M1) maximum plasma concentrations (Cmax) were 4.2 ± 0.8 ng mL?1 and 14.3 ± 2.8 ng mL?1 for T1 and T4, respectively. Times to reach maximum plasma concentrations (Tmax) were 27.6 ± 6.3 minutes for T1 and 32.1 ± 7.8 minutes for T4. No sedation occurred. There were signs of nausea and mild to moderate salivation in both groups.

Conclusion and clinical relevance

Tramadol was metabolized marginally to O-desmethyltramadol and failed to produce clinically relevant acute antinociception. Therefore, the use of tramadol for acute nociceptive pain is questionable in dogs.  相似文献   

8.

Objective

To evaluate intraoperative and postoperative efficacy of ultrasound (US)-guided femoral (FN) and obturator (ON) nerves block, in the iliopsoas muscle compartment (IPM), using an in-plane technique.

Study design

Anatomical research and randomized, prospective, ‘blinded’ clinical study.

Animals

Six dog cadavers and 20 client-owned dogs undergoing tibial plateau levelling osteotomy (TPLO) surgery.

Methods

In phase 1, anatomical dissections and US imaging of the IPM were performed to design an US-guided nerve block involving the FN and ON simultaneously. The technique was considered successful if new methylene blue solution injection (0.1 mL kg?1) stained FN–ON for ≥2 cm. In phase 2, the US-guided nerve block designed in phase 1, combined with US-guided sciatic nerve (ScN) block, was performed in 20 dogs undergoing TPLO surgery. Patients were assigned randomly to one of two treatment groups: ropivacaine 0.3% (R3, n = 10) and ropivacaine 0.5% (R5, n = 10) at a volume of 0.1 mL kg?1 for each nerve block. Intraoperative success rate (fentanyl requirement < 2.1 mcg kg?1 hour?1) and postoperative pain score [Short Form-Glasgow Composite Measure Pain Scale (SF-GCMPS) ≥ 5/20] were evaluated.

Results

In phase 1, the US image of FN–ON was detected between L6 and L7. In-plane needling technique produced a staining of >4 cm in six of six cases. No abdominal or epidural dye spread was found. In phase 2, median fentanyl infusion rates were 0.5 (0.0–0.9) μg kg?1 hour?1 for R3 and 0.6 (0.0–2.2) μg kg?1 hour?1 for R5. At 9 and 11 hours after the peripheral nerve blocks, an SF-GCMPS ≥ 5 was observed for R3 and R5, respectively.

Conclusions and clinical relevance

The US-guided FN–ON block in the IPM, using an in-plane technique, combined with US-guided ScN block, provided sufficient analgesia to minimize the use of fentanyl during TPLO surgery. A longer postoperative analgesia was observed in group R5 compared with R3.  相似文献   

9.

Objective

To evaluate the ability of pulse wave transit time (PWTT) to detect changes in stroke volume (SV) and to estimate cardiac output (CO) compared with the thermodilution technique in isoflurane-anaesthetized dogs.

Study design

Prospective, experimental study.

Animals

Eight adult laboratory dogs.

Methods

The dogs were anaesthetized with isoflurane and mechanically ventilated. Reference CO (TDCO) was measured via a pulmonary artery catheter using the thermodilution technique and reference SV (TDSV) was calculated. PWTT was calculated as the time from the electrocardiogram R-wave peak to the rise point of the pulse oximeter wave. Estimated CO (esCO) was derived from PWTT after calibration with arterial pulse pressure (both non-invasive and invasive methods) and TDCO. Haemodynamic changes were induced by administration of phenylephrine (vasoconstriction), high isoflurane (vasodilatation and negative inotropy) and dobutamine (vasodilatation and positive inotropy). Trending between percentage change in PWTT and TDSV was assessed using concordance analysis and receiver operator characteristic (ROC) curve. The agreement between esCO and TDCO was evaluated using the Bland–Altman method.

Results

The direction of percentage change between consecutive PWTT and the corresponding TDSV showed a concordance rate of 95%, with correlation coefficients of ?0.86 (p < 0.001). Area under the ROC curve for the change in PWTT to detect 15% change in TDSV was 0.91 (p < 0.001). TDCO compared with esCO calibrated with invasive and non-invasive blood pressure showed a bias (precision of agreement) of 0.58 (1.54) and 0.57 (1.59) L minute?1 with a percentage error of ±61% and ±63%, respectively.

Conclusions and clinical relevance

In isoflurane-anaesthetized dogs, PWTT showed a good trending ability to detect 15% changes in SV. This technique is easy to use, inexpensive, non-invasive and could become routine anaesthetic monitoring. However, the agreement between absolute esCO and TDCO was unacceptable.  相似文献   

10.

Objective

To determine if neuromuscular monitoring at the pelvic limb accurately reflects neuromuscular function in the larynx after administration of rocuronium in anesthetized dogs.

Study design

Prospective experimental study.

Animals

Six healthy Beagle dogs.

Methods

Anesthesia was maintained in dogs with isoflurane and a continuous infusion of dexmedetomidine. Rocuronium (0.6 mg kg?1) was administered intravenously to induce neuromuscular block. Train-of-four (TOF) impulses were applied to the left recurrent laryngeal nerve (RLn) and the peroneal nerve (Pn). The evoked TOF ratio (TOFR; T4:T1) was measured with electromyography (EMG) simultaneously at the larynx and at the pelvic limb. Spontaneous recoveries of T1 to 25% (T125%) and 75% (T175%) of twitch height, and to TOFR of 0.70 and 0.90 (TOFR0.90) at each EMG site were compared.

Results

Data from five dogs were analyzed. Times to T125% were similar at the pelvic limb and larynx when measured by EMG; time to T175% was slower at the larynx by 6 ± 4 minutes (p = 0.012). The larynx had a slower recovery to TOFR0.70 (41 ± 13 minutes) and TOFR0.90 (45 ± 13 minutes) than did the pelvic limb [29 ± 8 minutes (p = 0.011) and 33 ± 9 minutes (p = 0.003), respectively]. When the pelvic limb EMG returned to TOFR0.70 and TOFR0.90, the larynx EMG TOFR0.70 and TOFR0.90 values were 0.32 ± 0.12 (p = 0.001) and 0.38 ± 0.13 (p = 0.001), respectively.

Conclusions and clinical relevance

After administration of rocuronium, neuromuscular function assessed by EMG recovered approximately 36% slower at the larynx than at the pelvic limb. The results in these dogs suggest that quantitative neuromuscular monitoring instrumented at a pelvic limb may be unable to exclude residual block at the larynx in anesthetized dogs.  相似文献   

11.

Objective

The combination of butorphanol, azaperone and medetomidine (BAM) with subsequent antagonism by naltrexone–yohimbine or naltrexone–atipamezole was evaluated for reversible immobilization of captive African lions (Panthea leo).

Study design

Prospective, clinical trial.

Animals

Twenty lions, 11 males and nine females, weighing 38–284 kg were immobilized in South Africa.

Methods

The BAM volume dose rate administered was 0.005–0.008 mL kg?1 (0.6 mL 100 kg?1). Physiologic variables were recorded every 5 minutes. Four arterial blood samples were collected from all animals at 20, 30, 40 and 50 minutes after immobilization for analysis of blood-gases and acid-base status.

Results

The actual doses administered were as follows: butorphanol, 0.18 ± 0.03 mg kg?1; azaperone, 0.07 ± 0.01 mg kg?1; and medetomidine, 0.07 ± 0.01 mg kg?1. The inductions were calm and smooth, and induction time ranged from 4 to 10 minutes (7 ± 2 minutes). The amount of time needed to work with each lion was 70 minutes, and no additional drug doses were needed. Heart rate (40 ± 8 beats minute?1) and respiratory frequency (15 ± 4 breaths minute?1) were stable throughout immobilization. The mean arterial blood pressure of all animals was stable but elevated (142 ± 16 mmHg). The rectal temperature slightly increased over time but remained within acceptable range. The recovery time was significantly shorter when using naltrexone and atipamezole (9 ± 1 minutes) compared to using naltrexone and yohimbine (22 ± 7 minutes).

Conclusion and clinical relevance

The BAM combination proved to be reliable for general veterinary anaesthesia in lions. During anaesthesia, minor veterinary procedures such a blood collection, intubation, vaccination and collaring could safely be performed with no additional dosing required.  相似文献   

12.

Objective

To determine the effects of low and high dose infusions of dexmedetomidine and a peripheral α2-adrenoceptor antagonist, MK-467, on sevoflurane minimum alveolar concentration (MAC) in dogs.

Study design

Crossover experimental study.

Animals

Six healthy, adult Beagle dogs weighing 12.6 ± 0.9 kg (mean ± standard deviation).

Methods

Dogs were anesthetized with sevoflurane in oxygen. After a 60-minute instrumentation and equilibration period, the MAC of sevoflurane was determined in triplicate using the tail clamp technique. PaCO2 and temperature were maintained at 40 ± 5 mmHg (5.3 ± 0.7 kPa) and 38 ± 0.5 ºC, respectively. After baseline MAC determination, dogs were administered two incremental loading and infusion doses of either dexmedetomidine (1.5 μg kg?1 then 1.5 μg kg?1 hour?1 and 4.5 μg kg?1 then 4.5 μg kg?1 hour?1) or MK-467 (90 μg kg?1 then 90 μg kg?1 hour?1 and 180 μg kg?1 then 180 μg kg?1 hour?1); loading doses were administered over 10 minutes. MAC was redetermined in duplicate starting 30 minutes after the start of drug administration at each dose. End-tidal sevoflurane concentrations were corrected for calibration and adjusted to sea level. A repeated-measures analysis was performed and comparisons between doses were conducted using Tukey's method. Statistical significance was considered at p < 0.05.

Results

Sevoflurane MAC decreased significantly from 1.86 ± 0.3% to 1.04 ± 0.1% and 0.57 ± 0.1% with incremental doses of dexmedetomidine. Sevoflurane MAC significantly increased with high dose MK-467, from 1.93 ± 0.3% to 2.29 ± 0.5%.

Conclusions and clinical relevance

Dexmedetomidine caused a dose-dependent decrease in sevoflurane MAC, whereas MK-467 caused an increase in MAC at the higher infusion dose. Further studies evaluating the combined effects of dexmedetomidine and MK-467 on MAC and cardiovascular function may elucidate potential benefits of the addition of a peripheral α2-adrenergic antagonist to inhalation anesthesia in dogs.  相似文献   

13.

Objective

To evaluate the effect of hyaluronidase on uptake, duration and speed of elimination of xylazine–tiletamine–zolazepam administered in the subcutaneous fat over the dorsal lumbar region of swine.

Study design

Blinded, randomized, crossover study.

Animals

Six healthy Landrace/Large White pigs weighing 132 ± 24 kg (mean ± standard deviation).

Methods

Animals were administered xylazine (1 mg kg?1) and tiletamine–zolazepam (8 mg kg?1) (control treatment, CON), or xylazine–tiletamine–zolazepam at the same doses with hyaluronidase (400 IU) (treatment HYA). The treatments were administered into the dorsal lumbar adipose tissue, 2.5–3.0 cm laterally from the spinous process of the second lumbar vertebra. The latency, anesthesia and recovery periods were measured. Heart rate, noninvasive systolic, diastolic, and mean arterial pressures, respiratory rate, hemoglobin oxygen saturation and rectal temperature were recorded every 10 minutes for up to 50 minutes.

Results

One animal in CON and one animal in HYA were responsive to stimulation and did not allow safe handling. No significant difference was found between treatments for latency (CON 11.3 ± 5.9 minutes, HYA 7.4 ± 5.1 minutes) and anesthesia (CON 53 ± 53 minutes, HYA 49 ± 38 minutes) periods. Recovery period was shorter in HYA (9 ± 6 minutes) than in CON (32 ± 16 minutes) (p < 0.05). Physiological variables were not significantly changed over time and were within accepted normal clinical limits for the species in both treatments.

Conclusion and clinical relevance

Hyaluronidase (400 IU) administered into adipose tissue in pigs did not reduce the latency and duration of dissociative anesthesia, but was associated with faster recovery.  相似文献   

14.

Objective

To evaluate three volumes of lidocaine for spermatic cord block to perform castration in cattle.

Study design

Randomized blinded clinical study.

Animals

Thirty mixed-breed Nellore cattle, aged 28–40 months and weighing 395 ± 21 (352–452) kg [mean ± standard deviation (range)].

Methods

Cattle were restrained in a chute and allowed to stand without sedation. Three milliliters of 2% lidocaine without epinephrine were infiltrated subcutaneously at each site of scrotal incision in all animals. The animals were allocated to three groups of 10 animals each. Lidocaine 2% was injected into each spermatic cord using a volume of 2, 3 or 4 mL in groups A, B, or C, respectively. The total volumes of lidocaine used were 10, 12, and 14 mL in groups A, B, and C, respectively. The duration of surgery and the retraction of the testicle (scored as positive or negative according to retraction of the testicle) during the procedure were recorded. The data were statistically analyzed by one-way anova followed by Tukey’s and chi-square tests. Differences were considered significant when p < 0.05.

Results

The mean surgical time was shorter in group C than in groups A and B (p < 0.001). In groups A, B and C, 90%, 60% and 10% of the animals showed retraction of the testicle, respectively. Fewer animals retracted the spermatic cord in group C than in group A (p = 0.002) and B (p = 0.02).

Conclusions and clinical relevance

Optimal spermatic cord block was achieved by injection of 4 mL of 2% lidocaine 5 minutes before castration and following incisional infiltration of lidocaine, in adult cattle weighing about 400 kg.  相似文献   

15.

Objective

To measure intraocular pressure (IOP) in horses during hoisting after induction of anesthesia.

Study design

Prospective nonrandomized clinical study.

Animals

Eighteen healthy adult horses aged [mean ± standard deviation (SD)] 10 ± 4.2 years and weighing 491 ± 110 kg anesthetized for elective procedures.

Methods

IOP was measured in the superior eye of each horse based on planned recumbency after induction of anesthesia. Measurements were taken directly after premedication with xylazine or detomidine with butorphanol, after induction with diazepam–ketamine, after intubation, when suspended by the hoist and on the operating table. During hoisting, the head was supported and the eye–heart height was measured to account for variations in head positioning among patients. IOPs were compared across time points using repeated-measures analysis of variance. Regression was used to compare IOP outcome with potential cofactors.

Results

Compared with measurements after premedication (17.5 ± 2.5 mmHg) (mean ± SD), hoisting significantly increased IOP (32.4 ± 15.3 mmHg) (p < 0.01). The highest recorded IOP in the hoist was 80.0 (range, 16.0–80.0) mmHg. The difference in IOP between premedication and hoisting was 15.0 ± 16.2 (range, –1.0 to 68.0) mmHg. Body weight had a significant effect on absolute IOP and change in IOP in the hoist (p < 0.01).

Conclusions and clinical relevance

Hoist IOP was significantly higher than post-premedication IOP with heavier horses having higher hoist IOPs and greater increases in IOP. The clinician should take this relationship into account when anesthetizing and hoisting larger horses where an increase in IOP could be detrimental.  相似文献   

16.

Objective

To evaluate skin temperature increase as an early predictive measure for evaluating epidural and femoral-sciatic block success in dogs.

Study design

Prospective clinical trial.

Animals

A total of 29 dogs undergoing orthopaedic surgery on one hindlimb.

Methods

Dogs were anaesthetized and placed into lateral recumbency with the affected limb uppermost and the coat was clipped. Baseline infrared thermographic images (T0) of the affected limb, of the paw pad of the affected leg and of the ipsilateral paw pad were taken. Subsequently, dogs were administered either an epidural (EPI; n = 11) or a femoral–sciatic block (FS; n = 18) using bupivacaine 1 mg kg?1. Then, 2 minutes after placement of the block, thermographic images were obtained every 3 minutes for a total of four measurements (T1–T4) and surgery was commenced. Rescue analgesia consisting of fentanyl 1 μg kg?1 was administered if needed. A regional block was considered successful if the dose of fentanyl administered was less than the lower 95% confidence interval of the geometric mean of the total fentanyl used in each group. A ≥ 1 °C increase of skin temperature was considered as the minimum increase required for detection of a successful block.

Results

A total of 12 out of 18 blocks in the FS and eight of 11 in the EPI group were considered successful based on fentanyl consumption. Out of these, only four of 12 in the FS and one of eight in the EPI group developed an increase in temperature of ≥ 1 °C. Contrarily, four of six of the nonsuccessful cases in the FS and three of three in the EPI group developed an increase in temperature of ≥ 1 °C.

Conclusions and clinical relevance

Contrary to reports in humans, thermography did not indicate regional block success prior to surgery in dogs. However further studies under more controlled conditions are needed to determine whether thermography can be used to indicate failure of regional blockade.  相似文献   

17.

Objective

To study the effects of MK-467, a peripheral α2-adrenoceptor antagonist, on sedation, heart rate and blood pressure after intramuscular (IM) coadministration with 25 μg kg?1 of dexmedetomidine in cats.

Study design

Prospective, randomized, controlled, blinded, cross-over, experimental study.

Animals

A total of eight healthy, adult, neutered male cats.

Methods

Cats were administered five IM treatments at least 2 weeks apart, consisting of dexmedetomidine 25 μg kg?1 (D25), MK-467 600 μg kg?1 (M600) and D25 combined with 300, 600 and 1200 μg kg?1 of MK-467 (D25M300, D25M600 and D25M1200, respectively). Heart rate and direct arterial blood pressure were recorded via telemetry and sedation assessed prior to treatments and at intervals for 8 hours thereafter.

Results

Heart rate decreased significantly after all treatments with dexmedetomidine and remained below baseline up to 240 (D25), 20 (D25M300) and 3 minutes (D25M600 and D25M1200). Mean arterial pressure (MAP) increased with D25, remained unchanged with M600 and decreased over time with all combination treatments. The highest and lowest MAP after each treatment were 168 ± 17 and 100 ± 14 (D25), 157 ± 18 and 79 ± 11 (D25M300), 153 ± 11 and 74 ± 10 (D25M600), 144 ± 12 and 69 ± 7 (D25M1200) and 136 ± 9 and 104 ± 13 mmHg (M600). All treatments with dexmedetomidine produced sedation although its duration was significantly reduced by the addition of MK-467.

Conclusions and clinical relevance

Dexmedetomidine induced bradycardia and hypertension, which were attenuated by all three doses of MK-467. The duration of sedation was reduced by MK-467. MK-467 may improve the cardiovascular tolerance of IM dexmedetomidine in cats.  相似文献   

18.

Objective

N-butane and n-pentane can both produce general anesthesia. Both compounds potentiate γ-aminobutyric acid type A (GABAA) receptor function, but only butane inhibits N-methyl-d-aspartate (NMDA) receptors. It was hypothesized that butane and pentane would exhibit anesthetic synergy due to their different actions on ligand-gated ion channels.

Study design

Prospective experimental study.

Animals

A total of four Xenopus laevis frogs and 43 Sprague–Dawley rats.

Methods

Alkane concentrations for all studies were determined via gas chromatography. Using a Xenopus oocyte expression model, standard two-electrode voltage clamp techniques were used to measure NMDA and GABAA receptor responses in vitro as a function of butane and pentane concentrations relevant to anesthesia. The minimum alveolar concentrations (MAC) of butane and pentane were measured separately in rats, and then pentane MAC was measured during coadministration of 0.25, 0.50 or 0.75 times MAC of butane. An isobole with 95% confidence intervals was constructed using regression analysis. A sum of butane and pentane that was statistically less than the lower-end confidence bound isobole indicated a synergistic interaction.

Results

Both butane and pentane dose-dependently potentiated GABAA receptor currents over the study concentration range. Butane dose-dependently inhibited NMDA receptor currents, but pentane did not modulate NMDA receptors. Butane and pentane MAC in rats was 39.4 ± 0.7 and 13.7 ± 0.4 %, respectively. A small but significant (p < 0.03) synergistic anesthetic effect with pentane was observed during administration of either 0.50 or 0.75 × MAC butane.

Conclusions

Butane and pentane show synergistic anesthetic effects in vivo consistent with their different in vitro receptor effects.

Clinical relevance

Findings support the relevance of NMDA receptors in mediating anesthetic actions for some, but not all, inhaled agents.  相似文献   

19.

Objective

To compare the duration of action of atracurium in diabetic and nondiabetic dogs.

Study design

Prospective, blinded, clinical study.

Animals

A total of 26 diabetic and 29 nondiabetic dogs.

Methods

Following preanaesthetic medication and intravenous (IV) propofol induction, anaesthesia was maintained with isoflurane in oxygen. Atracurium 0.2 mg kg?1 IV was administered to provide neuromuscular blockade (NMB) and the responses (twitches; T) to train-of-four nerve stimulation were recorded by palpation and electromyography (EMG). Time to onset of NMB (from atracurium administration to loss of T4 by EMG), duration of NMB (to return of T1 by EMG) and also times to loss and return of T2–T4 were recorded. Heart rate (HR), mean arterial pressure, end-tidal isoflurane (Fe′Iso), end-tidal CO2 concentrations and oesophageal temperature were recorded at onset of NMB and when T1EMG returned. Groups were compared using t tests and Mann–Whitney U tests (p < 0.05).

Results

Diabetic dogs were older (9.9 ± 0.3 compared with 6.8 ± 0.7 years, p = 0.0003). Group parameters were similar at onset and offset of NMB apart from HR at offset, which was higher for diabetics compared to nondiabetics (114 ± 4 compared with 100 ± 3 beats minute?1, respectively, p = 0.004), Fe′Iso was higher in the diabetic group at onset (1.3 ± 0.03% compared with 1.2 ± 0.04%, p = 0.026) and offset (1.4 ± 0.03% compared with 1.3 ± 0.03%, p = 0.007), and temperature was higher for diabetics at onset (37.5 ± 0.1 °C compared with 37.0 ± 0.2 °C, p = 0.012) and offset (37.5 ± 0.1 °C compared with 36.9 ± 0.2 °C, p = 0.004). The duration of action of atracurium(tactile) and atracurium(EMG) were similar for both groups.

Conclusions and clinical relevance

The duration of action of atracurium was similar in diabetic and nondiabetic dogs as indicated by tactile and EMG monitoring.  相似文献   

20.

Objective

To compare airway management during induction of anaesthesia, spontaneous ventilation (SV) and controlled mechanical ventilation (CMV), using an endotracheal tube (ETT), laryngeal mask (LM), rabbit-specific supraglottic airway device (v-gel) or facemask (FM).

Study design

Prospective randomized crossover experiment.

Animals

Ten New Zealand White rabbits.

Methods

After premedication, rabbits were randomly allocated to four groups: 1) ETT; 2) LM; 3) v-gel or 4) FM. The required dose of propofol, duration and number of attempts to place an airway device and leakage during SV and CMV at different peak inspiratory pressures (6, 10, 12, 14 and 16 cmH2O) were recorded. Computed tomography (CT) of the head, neck and abdomen were performed before and after CMV.

Results

Significantly less propofol and time [2.0 ± 0.5 mg kg?1, 82 ± 34 seconds, p < 0.001] were needed to place the FM compared to the three other groups [v-gel 5.1 ± 2.1 mg kg?1, 302 ± 124 seconds; LM 4.8 ± 1.2 mg kg?1, 275 ± 89 seconds; ETT 5.5 ± 1.4 mg kg?1, 315 ± 147 seconds]. A leak > 25% of the tidal volume occurred at the lowest pressure in FM [median (range), 6 (6–8) cmH2O], which was significantly lower than with v-gel [16 (6–no leak at 16) cmH2O], LM [>16 (6–no leak at 16)] or ETT [>16 (no leak at 16) cmH2O] (p < 0.001). On CT images, the height and width of the larynx were significantly smaller with v-gel in comparison to FM and LM (p = 0.004). A significant increase in the amount of gas in the stomach (p = 0.007), but not gastric volume, was detected in FM and LM.

Conclusions and clinical relevance

The v-gel is a practical alternative to LM and ETT for airway management and CMV, but can compress the larynx. The FM is easily placed, but significant leakage occurs during CMV.  相似文献   

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