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1.

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   

2.

Objective

To determine the anti-inflammatory efficacy of choline in vivo and in vitro and to investigate the anti-inflammatory mechanisms of choline.

Study design

Randomized, controlled studies.

Animals

In vivo trials used 16 Romney sheep. In vitro experiments utilized RAW 264.7 mouse macrophage cells.

Methods

Hypoxaemia induced in 16 sheep by intravenous (IV) injection of 50 μg kg–1 xylazine, an α-2 agonist, was measured in sheep at 0, 1 and 4 minutes using arterial blood gas analysis with and without 50 mg kg–1 IV choline chloride premedication. Cell culture studies used enzyme-linked immunosorbent assay to measure the release of tumour necrosis factor (TNF-α) from lipopolysaccharide (LPS) stimulated macrophages with and without choline chloride premedication. TNF-α release was compared to thalidomide suppressed and untreated cells.

Results

Choline premedication in sheep mitigated a reduction in arterial partial pressure of oxygen (PaO2) but did not prevent development of clinically significant hypoxaemia. Decrease in mean PaO2 of choline treated sheep was 6.36 kPa (47.7 mmHg) compared to 9.81 kPa (73.6 mmHg) in control sheep. In vitro studies demonstrate that choline administered concurrent with LPS activation did not significantly suppress TNF-α expression but that treatment of cells with choline 10 minutes prior to LPS activation did significantly suppress TNF-α expression. Choline pretreated cells expressed 23.99 ± 4.52 ng mg–1 TNF-α while LPS only control cells expressed 33.83 ± 3.20 ng mg–1.

Conclusions

Choline is able to prevent macrophage activation in vitro when administered prior to LPS activation and may reduce hypoxaemia in sheep developing pulmonary oedema after xylazine administration. This effect requires premedication with choline.

Clinical relevance

Pharmacological manipulation of autonomic inflammatory responses holds promise for the treatment of inflammation. However, the complex cellular mechanisms involved in this reflex means that an adequate therapy should approach multiple pathways and mechanisms of the inflammatory response.  相似文献   

3.
4.

Objective

To investigate changes in serum cardiac troponin I (cTnI) concentrations in dogs in which medetomidine was used for sedation or for premedication prior to anaesthesia with propofol and sevoflurane.

Study design

Prospective clinical study.

Animals

A total of 66 client-owned dogs.

Methods

The dogs were sedated with medetomidine (0.04 mg kg?1) intravenously (IV) (group M; n = 20) and left to breath room air or anaesthetized with propofol (6.5 ± 0.76 mg kg?1 IV) and sevoflurane (4.5% vaporizer setting) in oxygen (group P + S; n = 20) or with medetomidine (0.04 mg kg?1 IV), propofol (1.92 ± 0.63 mg kg?1) and sevoflurane (3% vaporizer setting) in oxygen (group M + P + S; n = 26), respectively. After 35 minutes, medetomidine was antagonized with atipamezole (0.1 mg kg?1 intramuscularly). Blood samples for serum cTnI determination were taken before sedation or anaesthesia, 6 and 12 hours and 4 days thereafter. Serum cTnI concentrations were measured with the Architect STAT Troponin-I assay.

Results

Before sedation or anaesthesia, cTnI concentrations were above the detection limit in 22 out of 66 (33%) of dogs. Compared to basal values, cTnI concentrations significantly increased at 6 and 12 hours in all groups and at day 4 in group M. There were no differences in cTnI concentration between groups at baseline, at 6 hours and at 4 days. At 12 hours, cTnI concentrations were significantly higher in groups M and P + S, respectively, compared to group M + P + S.

Conclusions and clinical relevance

Oxygenation during anaesthesia and reduction of propofol and sevoflurane dose due to the sparing effects of medetomidine might have played a role in alleviation of myocardial hypoxic injury as indicated by the less severe and short-lived increase of cTnI in the M + P + S group.  相似文献   

5.

Objective

To describe the anaesthetic, physiological and side effects of intramuscular (IM) medetomidine and ketamine, followed by inhalational anaesthesia with sevoflurane, in Nile crocodiles (Crocodylus niloticus).

Study design

Observational trial.

Animals

Ten juvenile captive-bred Nile crocodiles undergoing surgical implantation of skeletal beads and muscular electrodes.

Methods

During preanaesthetic examination, the following variables were assessed: heart (HR) and respiratory (fR) rates, and response to palpebral, corneal and toe- and tail-pinch withdrawal reflexes. The crocodiles were injected IM with an initial combination of medetomidine and ketamine and re-evaluated at 5 minute intervals for 20 minutes, or until they appeared unresponsive. If that did not occur, the drugs were redosed according to a decision tree based on the observed effects. The righting, biting and palatal valve reflexes were assessed in the unresponsive crocodiles, and used to confirm anaesthetic induction. Anaesthesia was maintained with sevoflurane in oxygen. At the end of surgery, medetomidine was antagonized with IM atipamezole.

Results

The decision tree identified 0.3 mg kg?1 medetomidine and 15 mg kg?1 ketamine as a useful drug combination, which resulted in anaesthetic induction and surgical anaesthesia 16 ± 8 and 16 (25–20) minutes after injection, respectively. Compared to baseline, HR and fR significantly decreased after anaesthetic induction (p < 0.001), but then remained stable throughout surgery. Intraoperatively, cloacal temperature [27 (26–30) °C] did not change over time (p = 0.48). The total dose of atipamezole was 2 (1–3) mg kg?1 and time to recovery was 36 (20–60) minutes. Perioperative complications were not observed.

Conclusions

and clinical relevance Medetomidine and ketamine, injected IM and followed by sevoflurane anaesthesia, may be regarded as a useful anaesthetic technique for juvenile Nile crocodiles undergoing minimally invasive experimental surgery.  相似文献   

6.

Objective

To assess the cardiopulmonary effects caused by reverse Trendelenburg position (RTP) at 5° and 10° in sevoflurane-anesthetized yearling steers.

Study design

Prospective, experimental study.

Animals

Eight Holstein steers aged (mean ± standard deviation) 12 ± 2 months and weighing 145 ± 26 kg.

Methods

In the first phase of the study, the individual minimum alveolar concentration (MAC) of sevoflurane was determined using electrical stimulation. In the second phase, the effects of RTP were assessed. The animals were anesthetized on three separate events separated by ≥7 days in an incomplete crossover design: control treatment using a table without tilt (RTP0); treatment with the table at 5° RTP (RTP5) and table tilted 10° RTP (RTP10). Subjects were physically restrained in dorsal recumbency on the table, which was already tilted according to each treatment. Anesthesia was induced with sevoflurane at 8% in 5 L minute–1 oxygen via face mask followed by maintenance with sevoflurane at 1.3 MAC and spontaneous breathing. Cardiopulmonary variables were obtained immediately after instrumentation (T0) and then after 30, 60, 120 and 180 minutes (T30, T60, T120 and T180, respectively).

Results

The mean sevoflurane MAC for the eight steers was 2.12 ± 0.31%. Cardiac output was lower at all time points and the systemic vascular resistance index was higher at T120 and T180 in RTP10 compared with RTP0. Oxygen consumption was lower at T0 and at T180 in RTP10 compared with RTP0 and at all time points except T30 compared with RTP5. Oxygen extraction was lower at T0 in RTP10 compared with RTP0 and RTP5, and at T60 and T180 compared with RTP5.

Conclusions and clinical relevance

RTP 5° and 10° did not improve ventilatory and oxygenation variables in sevoflurane-anesthetized steers when compared with no tilt, however the cardiovascular variables were adversely affected in RTP10.  相似文献   

7.

Objective

To compare two methods of Bohr–Enghoff physiological dead space to tidal volume ratio (Vd/VtBohr–Enghoff) determination using a mixing chamber and an E-CAiOVX metabolic monitor.

Study design

Prospective, clinical, method-comparison study.

Animals

Twenty horses anaesthetized for elective orthopaedic procedures.

Methods

Horses were anaesthetized with isoflurane in oxygen and the lungs were mechanically ventilated (Vt 15 ± 2 mL kg?1). Arterial blood was sampled to provide arterial partial pressure of carbon dioxide (PaCO2) for dead space calculation using a metabolic monitor. Mixed expired partial pressure of carbon dioxide (PēCO2) obtained from the custom-made mixing chamber was recorded at the time of arterial blood sampling. Dead space fraction was calculated using the Enghoff modification of the Bohr equation. Agreement between the methods was assessed by Bland–Altman test. A clinically acceptable error was defined to be ≤ 10%.

Results

Forty-nine simultaneous Vd/VtBohr–Enghoff results were obtained. There was no clinically significant bias between the mixing chamber and E-CAiOVX. The limits of agreement were within a priori defined error (bias ± 95% limits of agreement: ?0.022 ± 0.078).

Conclusions and clinical relevance

Acceptable agreement was found between the two methods. The E-CAiOVX metabolic monitor might be a suitable device for measuring Vd/VtBohr–Enghoff in anaesthetized horses.  相似文献   

8.

Objective

To evaluate the pharmacokinetics of two doses of tramadol during isoflurane anaesthesia in sheep and their ability to prevent the cardiovascular response induced by surgical stimulation.

Study design

Prospective randomized controlled study.

Animals

A total of 12 healthy sheep (mean weight, 47.5 ± 7.9 kg) undergoing lumbar transpedicular intervertebral disk nucleotomy.

Methods

Sheep were sedated with medetomidine, anaesthesia was induced with propofol and maintained with isoflurane at 1.5 vol.%. Baseline heart rate and blood pressure were measured and sheep were randomly assigned an intravenous injection of tramadol (4 or 6 mg kg?1). Fentanyl was injected as rescue analgesic if cardiovascular parameters were increased more than 20% compared to baseline. If those variables were below 20% of baseline, the concentration of isoflurane was gradually decreased until parameters returned to the original value. Blood collections were performed at pre-assigned times, and concentrations of tramadol and O-desmethyltramadol (M1) assessed by high-performance liquid chromatography.

Results

Time from premedication to anaesthesia induction, anaesthesia time, propofol dose and intraoperative body temperature were similar between doses. Cardiovascular variables remained between ±20% of baseline value, and no statistical difference was observed between treatments. Regardless of the dose of tramadol administered, arterial blood pressure was statistically higher than baseline 10 minutes after tramadol administration, but it gradually returned to previous values. A two-compartment model and a non-compartment model described the pharmacokinetics of tramadol and M1, respectively. Plasma concentrations of tramadol rapidly decreased in the first 2 hours for both doses with an elimination half-life of more than 40 minutes. The M1 maximum concentration was similar for both doses, and it was detected in plasma after 35 minutes.

Conclusions and clinical relevance

Both doses of tramadol provided adequate cardiovascular stability during spinal surgery in sheep. The pharmacokinetic variables may be used to plan the dosage regime during general anaesthesia.  相似文献   

9.

Introduction

To determine the biologic variability of N-terminal pro-brain natriuretic peptide (NTproBNP) in healthy dogs and dogs with various stages of myxomatous mitral valve disease (MMVD).

Animals

Thirty-eight privately owned dogs: 28 with MMVD and 10 healthy controls.

Materials and methods

Prospective clinical study with comprehensive evaluation used to group dogs as healthy or into three stages of MMVD based on current guidelines. NTproBNP was measured hourly, daily, and weekly. For each group, analytical (CVA), within-subject (CVI), and between-subject (CVG) coefficients of variability were calculated in addition to percent critical change value (CCV) and index of individuality (IoI).

Results

For healthy dogs, calculated NTproBNP values were: CVA = 4.2%; CVI = 25.2%; CVG = 49.3%; IoI = 0.52, and CCV = 70.8%. For dogs with MMVD, calculated NTproBNP values were: CVA = 6.2%; CVI = 20.0%; CVG = 61.3%; IoI = 0.34, and CCV = 58.2%.

Conclusions

Biologic variability affects NTproBNP concentrations in healthy dogs and dogs with MMVD. Monitoring serial individual changes in NTproBNP may be clinically relevant in addition to using population-based reference ranges to determine changes in disease status.  相似文献   

10.

Objective

To compare time to desaturation after induction of anesthesia following administration of oxygen via face mask or flow-by for 3 minutes.

Study design

Randomized crossover study.

Animals

A group of six healthy adult dogs weighing 15.0 ± 3.4 kg.

Methods

Dogs were anesthetized twice separated by 14 days. Intramuscular administration of dexmedetomidine (4 μg kg?1), acepromazine (0.01 mg kg?1) and butorphanol (0.2 mg kg?1) provided sedation for percutaneous insertion of a catheter into the tracheal lumen. The tip was advanced to the thoracic inlet and position confirmed using fluoroscopy. Using a sample aspiration rate 200 mL minute?1, inspired (FIO2) and end-tidal oxygen (Fe′O2) were measured. Oxygen (100 mL kg?1 minute?1) was delivered into a circle delivery system and administered to the dog for 3 minutes via face mask or flow-by from the circle Y-piece 2.5 cm from the nares. Then, propofol was administered to induce anesthesia and apnea. A pulse oximeter (lingual probe) measured hemoglobin saturation (SpO2). At SpO2 90% (desaturation point), an endotracheal tube was inserted to allow administration of oxygen and artificial ventilation. Arterial blood and data were collected at baseline (before oxygen administration), 5 seconds after induction of anesthesia, and every 30 seconds until the desaturation point was reached. Data were analyzed using an unpaired and paired t test with (p < 0.05).

Results

FIO2, Fe′O2 and PaO2 (mean ± standard deviation) were significantly higher after mask preoxygenation [89.7 ± 5.5%, 83.0 ± 7.6% and 394 ± 112 mmHg (52.4 ± 14.9 kPa)] compared with flow-by [30.0 ± 5.4%, 22.7 ± 3.8% and 133 ± 22 mmHg (17.7 ± 2.9 kPa)], respectively. Time to desaturation was significantly longer after mask treatment compared with flow-by (187 ± 67 versus 66 ± 17 seconds).

Conclusions and clinical relevance

Mask preoxygenation provided longer time to desaturation compared with the flow-by technique tested.  相似文献   

11.

Objective

To compare the effects of general anaesthesia using sevoflurane or alfaxalone on the brainstem auditory evoked response (BAER) test in adult healthy cats.

Study design

Prospective, clinical, ‘blinded’, crossover study.

Animals

Ten feral adult healthy cats.

Methods

Premedication consisted of dexmedetomidine (0.01 mg kg–1) intramuscularly (IM). The first general anaesthesia was induced and maintained with sevoflurane (treatment S) for physical examination, BAER test, complete blood tests, thoracic radiographs and abdominal ultrasound. The second general anaesthesia was induced with alfaxalone (treatment A) IM (2 mg kg–1) and maintained with alfaxalone (10 mg kg–1 hour–1) for the BAER test, followed by neutering surgery.The BAER recordings were compared for differences in latencies, amplitudes and waveform morphology. Data were analysed using Student's t test and Wilcoxon rank test for paired samples for parametric and non-parametric data, respectively. Statistical significance was set at p < 0.05.

Results

General anaesthesia was uneventful; normal BAER comprising five peaks could be identified in both treatments. Mean ± SD latencies were 1.05 ± 0.09, 1.83 ± 0.11, 2.52 ± 0.19, 3.43 ± 0.17 and 4.39 ± 0.15 ms and 1.03 ± 0.04, 1.81 ± 0.73, 2.53 ± 0.15, 3.37 ± 0.13 and 4.33 ± 0.13 ms in treatments S and A, respectively. Median (interquartile range) amplitudes were 2.83 (0.67), 1.27 (0.41), 0.30 (0.40), 1.05 (0.82), 0.61 (0.38) microvolts and 2.84 (1.21), 1.49 (1.18), 0.26 (0.32), 0.91 (0.50) and 0.92 (0.64) microvolts in treatments S and A, respectively. There were no statistically significant differences in mean latencies or median amplitudes between both the anaesthetics.

Conclusions and clinical relevance

This study demonstrates that there were no statistically significant differences between both the anaesthetics on the BAER test in adult healthy cats. Moreover, two possible anaesthetic protocols are described for cats undergoing this electrodiagnostic test.  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

We determined the possible effects of a peripherally acting α2-adrenoceptor antagonist, MK-467, on the absorption of intramuscularly (IM) coadministered medetomidine, butorphanol and midazolam.

Study design

Randomized, experimental, blinded crossover study.

Animals

Six healthy Beagle dogs.

Methods

Two IM treatments were administered: 1) medetomidine hydrochloride (20 μg kg–1) + butorphanol (100 μg kg–1) + midazolam (200 μg kg–1; MBM) and 2) MBM + MK-467 hydrochloride (500 μg kg–1; MBM–MK), mixed in a syringe. Heart rate was recorded at regular intervals. Sedation was assessed with visual analog scales (0–100 mm). Drug concentrations in plasma were analyzed with liquid chromatography–tandem mass spectrometry, with chiral separation of dex- and levomedetomidine. Maximum drug concentrations in plasma (Cmax) and time to Cmax (Tmax) were determined. Paired t-tests, with Bonferroni correction when appropriate, were used for comparisons between the treatments.

Results

Data from five dogs were analyzed. Heart rate was significantly higher from 20 to 90 minutes after MBM–MK. The Tmax values for midazolam and levomedetomidine (mean ± standard deviation) were approximately halved with coadministration of MK-467, from 23 ± 9 to 11 ± 6 minutes (p = 0.049) for midazolam and from 32 ± 15 to 18 ± 6 minutes for levomedetomidine (p = 0.036), respectively.

Conclusions and clinical relevance

MK-467 accelerated the absorption of IM coadministered drugs. This is clinically relevant as it may hasten the onset of peak sedative effects.  相似文献   

14.

Objective

To determine the optimal endotracheal tube size in Beagle dogs using thoracic radiography.

Study design

Prospective, randomized, crossover experimental study.

Animals

A total of eight healthy adult Beagle dogs.

Methods

Lateral thoracic radiographs were used to measure the internal tracheal diameter at the thoracic inlet. This measurement was multiplied by 60, 70 and 80% to determine the outer diameter of the endotracheal tube for each dog. In each treatment, medetomidine (5 μg kg?1) was administered intravenously (IV) for premedication. Anesthesia was induced with alfaxalone (2 mg kg?1) IV and maintained with isoflurane. After induction of anesthesia, the resistance to passage of the endotracheal tube through the trachea was scored by a single anesthesiologist. Air leak pressures (Pleak) were measured at intracuff pressures (Pcuff) of 20 and 25 mmHg (27 and 34 cmH2O). The results were analyzed using Friedman tests and repeated measures anova.

Results

There were statistically significant increases in resistance as the endotracheal tube size increased (p = 0.003). When Pcuff was 20 mmHg, mean Pleak for the 60, 70 and 80% treatments were 9.7 ± 6.7, 16.2 ± 4.2 and 17.4 ± 3.9 cmH2O, respectively, but no significant differences were found. When Pcuff was 25 mmHg, mean Pleak for the 60, 70 and 80% treatments were 10.6 ± 8.5, 19.7 ± 4.9 and 20.8 ± 3.6 cmH2O, respectively, and statistically significant increases were found between treatments 60 and 70% (p = 0.011) and between treatments 60 and 80% (p = 0.020). Three dogs in the 80% treatment had bloody mucus on the endotracheal tube cuff after extubation.

Conclusions and clinical relevance

Results based on resistance to insertion of the endotracheal tube and the ability to achieve an air-tight seal suggest that an appropriately sized endotracheal tube for Beagle dogs is 70% of the internal tracheal diameter measured on thoracic radiography.  相似文献   

15.

Objective

To record the cardiopulmonary effects of pleural CO2 positive pressure insufflation in anesthetized horses.

Study design

Prospective study.

Animals

Seven horses (mean ± standard deviation, 530.9 ± 68.1 kg) undergoing terminal surgery.

Methods

Horses were sedated with xylazine. Anesthesia was induced with ketamine–propofol and maintained with isoflurane, positive pressure ventilation, detomidine infusion, and butorphanol with the horses in dorsal recumbency. Baseline measurements were cardiac output, heart rate, pulmonary and systemic arterial and right atrial blood pressures, body temperature, expired and inspired gas concentrations, and arterial and mixed venous blood gases, electrolytes, glucose, and lactate concentrations. An 18 gauge 6.6 cm needle was inserted into the right pleural cavity midway between the sternum and dorsal midline in the sixth or seventh intercostal space for pleural pressure (PP) measurement. A 14 gauge 18 cm needle placed 5 cm below the previous needle allowed CO2 insufflation into the pleural cavity. All measurements were repeated after: needle insertion, at 2, 5, and 8 mmHg PPs, and after pleural gas removal (GR). Data were compared with baseline using one-way analysis of variance with repeated measures. p < 0.05 was considered significant.

Results

Actual PPs were within 1.1 mmHg of the targeted PP. Pulmonary systolic and mean arterial pressures, alveolar dead space to tidal volume ratio, and isoflurane requirements increased at 8 mmHg PP and GR. Cardiac index decreased at 5 mmHg PP. Stroke index decreased at 2 mmHg PP to GR. PaO2 decreased at 5 mmHg PP to GR. PaCO2 increased at 8 mmHg PP and GR. Oxygen delivery decreased at 5 and 8 mmHg PP. Intrapulmonary shunt fraction and lactate concentration increased with GR.

Conclusions and clinical relevance:

Severe adverse cardiopulmonary effects arise from CO2 positive pressure insufflation into the right hemithorax in dorsally recumbent isoflurane-anesthetized horses. PP should be ≤2 mmHg.  相似文献   

16.

Objective

To assess the reaction of client-owned dogs to intravenous (IV) catheter placement after applying a local anaesthetic (EMLA) or placebo cream for either 30 or 60 minutes.

Study design

Prospective, randomized, blinded, placebo-controlled, clinical trial.

Animals

A total of 202 client-owned dogs of various breeds.

Methods

With owner consent, dogs were randomly allocated to one of four treatment groups: EMLA 60 minutes, EMLA 30 minutes, Placebo 60 minutes and Placebo 30 minutes. After the cream was applied for the allocated time, an IV catheter was placed and the behavioural reaction of the dog was scored. The reaction score was analysed using a Kruskal–Wallis test followed by Mann–Whitney U tests of the multiple pairwise comparisons, with Bonferroni correction.

Results

A large number of dogs, even in the placebo groups, did not react to IV catheter placement. However, the Kruskal–Wallis test showed an overall difference between treatment groups (χ2 = 11.029, df = 3, p = 0.012). The pairwise comparisons showed a lower overall reaction score in the EMLA 60 group than in the EMLA 30 and Placebo 60 groups (adjusted p = 0.018 and adjusted p = 0.044, respectively).

Conclusions and clinical relevance

This study shows that EMLA cream applied for 60 minutes reduces the behavioural reaction of dogs to IV catheter placement; therefore, this intervention can be advocated for routine use in veterinary medicine to enhance the welfare of dogs undergoing IV catheter placement.  相似文献   

17.

Objectives

To determine the endotracheal tube cuff pressure produced with two inflation techniques, in two brands of endotracheal tube in cats. To determine the inspiratory pressure which produces an audible leak when the intracuff pressure is 30 cmH2O.

Study design

Prospective, clinical, randomized study.

Animals

A total of 40 client-owned healthy adult cats.

Methods

Following induction of anaesthesia, endotracheal intubation was performed with a Parker Flex-Tip PFLP (Parker; n = 20) or Flexicare VentiSeal (Flexicare; n = 20) endotracheal tube. For each cat, the endotracheal tube cuff was inflated using two methods, minimum occlusive volume (MOV) and pilot balloon palpation (PBP). Intracuff pressure was recorded. Cuff pressure was then set at 30 cmH2O and the pressure within the breathing system when a manual breath first caused an audible leak was measured.

Results

PBP pressure was lower for Parker (36 ± 13 cmH2O) compared with Flexicare (45 ± 13 cmH2O, p = 0.048). MOV pressure was not different between tube types (56 ± 28 versus 66 ± 25 cmH2O for Parker and Flexicare, respectively, p = 0.247). MOV produced a higher pressure than PBP for Parker (56 ± 28 versus 36 ± 13 cmH2O, p = 0.001) and Flexicare (66 ± 25 versus 45 ± 13 cmH2O, p = 0.007). When intracuff pressure was set at 30 cmH2O, 95% of cats did not develop an audible leak until the inspiratory pressure was greater than 10 and 12 cmH2O for Parker and Flexicare tubes, respectively.

Conclusions

PBP produced lower cuff pressures than MOV, although both techniques produced a cuff pressure above that at which mucosal blood flow is believed to be restricted. A cuff pressure of 30 cmH2O may be sufficient to prevent audible leak in most cats if respiratory pressures are kept at 10–12 cmH2O or below.

Clinical relevance

To ensure a safe endotracheal tube cuff pressure, use of a specifically designed pressure gauge is recommended.  相似文献   

18.

Objective

To study the effect of heterothermia on anaesthetic drug requirements in semi-free ranging Arabian oryx and to assess the temperature quotient (Q10) of oxygen consumption.

Study design

Prospective observational study and controlled metabolic experiment.

Animals

Sixty-eight anaesthetic events in 59 Arabian oryx from Mahazat As-Sayd protected area, Saudi Arabia

Methods

Anaesthesia was induced by remote injection of 25 mg ketamine, 10 mg midazolam and 0.5 mg medetomidine with a variable amount of etorphine based on a target dosage of 20 μg kg–1 and subjective assessment of body mass. Animals not recumbent within 15 minutes or insufficiently anaesthetized were physically restrained and administered supplementary etorphine intravenously depending on the anaesthetic depth. Body temperature (Tb) was measured rectally immediately upon handling of each animal. From six anaesthetized oryx, expiratory gasses for oxygen analysis and metabolic rate calculation were collected at two Tbs; before and after submersion in ice water for approximately 30 minutes.

Results

Forty-two animals (62%) became recumbent with the initial dose, with a mean induction time (± standard deviation) of 9 ± 2 minutes. The remaining animals could be handled but needed 0.3 ± 0.1 mg etorphine intravenously to reach the desired level of anaesthesia. There was a significant positive correlation between Tb and effective etorphine dosage (R2 = 0.48, p < 0.0001). Average Tb of the six animals in which metabolic rate was measured decreased from 40.0 ± 0.5°C immediately after induction to 35.5 ± 0.5°C after cooling. This reduction was associated with a reduction in oxygen uptake from 3.11 ± 0.33 to 2.22 ± 0.29 mL O2 minute–1 kg–1, reflected in Q10 of 2.17 ± 0.14.

Conclusions and clinical relevance

Tb significantly affects anaesthetic requirements in Arabian oryx and should be considered when selecting dosages for anaesthetic induction for species showing diurnal heterothermy.  相似文献   

19.

Objective

To evaluate an ultrasound-guided technique for adductor canal (AC) block by describing the distribution of methylene blue around the AC, popliteal fossa, saphenous, tibial and common fibular nerves in dog cadavers.

Study design

Prospective experimental trial.

Animals

Ten mixed breed canine cadavers weighing 28.55 ± 3.94 kg.

Methods

Ultrasound scans of the AC were performed bilaterally in 10 canine cadavers. A high-frequency linear transducer was placed on the long axis of the pectineus muscle and using an in-plane technique, an insulated needle was introduced at a proximal to distal direction into the AC. Methylene blue 0.1% (0.3 mL kg?1) was administered followed by dissection. The presence of dye over the target nerves for ≥2 cm was considered successful distribution. Three of 10 cadavers were submitted to computed tomography (CT) and one of them to magnetic resonance (MR) evaluation.

Results

Methylene blue reached the AC in 20 (100%) and the popliteal fossa in 17 (85%) pelvic limbs. Staining was successful in the saphenous nerve (4.0 ± 1.57 cm) in 11 (55%) limbs, tibial nerve (2.65 ± 0.8 cm) in six (30%) and common fibular nerve (2.7 ± 0.9 cm) in four (20%). There was no evidence of staining around the motor branches of the femoral nerve. No intraneural or intravascular dye spread was found during dissections. Contrast distribution to the popliteal fossa was observed in three limbs (50%) in CT and in one (50%) MR image.

Conclusions and clinical relevance

Although the tibial and common fibular nerves were not stained as often as the saphenous nerve, dye was encountered throughout the popliteal fossa near the nerves. The AC block may be useful for intra and postoperative analgesia in stifle surgery with minimal femoral motor dysfunction. However, further study is required to confirm its efficacy and safety in vivo.  相似文献   

20.

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   

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