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1.

Objective

To examine the intrapulmonary gas distribution of low and high tidal volumes (VT) and to investigate whether this is altered by an alveolar recruitment maneuver (ARM) and 5 cmH2O positive end-expiratory pressure (PEEP) during anesthesia.

Study design

Prospective randomized clinical study.

Animals

Fourteen client-owned bitches weighing 26 ± 7 kg undergoing elective ovariohysterectomy.

Methods

Isoflurane-anesthetized dogs in dorsal recumbency were ventilated with 0 cmH2O PEEP and pressure-controlled ventilation by adjusting the peak inspiratory pressure (PIP) to achieve a low (7 mL kg?1; n = 7) or a high (12 mL kg?1; n = 7) VT. Ninety minutes after induction (T90), an ARM (PIP 20 cmH2O for 10 seconds, twice with a 10 second interval) was performed followed by the application of 5 cmH2O PEEP for 35 minutes (RM35). The vertical (ventral=0%; dorsal=100%) and horizontal (right=0%; left=100%) center of ventilation (CoV), four regions of interest (ROI) (ventral, central-ventral, central-dorsal, dorsal) identified in electrical impedance tomography images, and cardiopulmonary data were analyzed using two-way repeated measures anova.

Results

The low VT was centered in more ventral (nondependent) areas compared with high VT at T90 (CoV: 38.8 ± 2.5% versus 44.6 ± 7.2%; p = 0.0325). The ARM and PEEP shifted the CoV towards dorsal (dependent) areas only during high VT (50.5 ± 7.9% versus 41.1 ± 2.8% during low VT, p = 0.0108), which was more distributed to the central-dorsal ROI compared with low VT (p = 0.0046). The horizontal CoV was centrally distributed and cardiovascular variables remained unchanged throughout regardless of the VT, ARM, and PEEP.

Conclusions and clinical relevance

Both low and high VT were poorly distributed to dorsal dependent regions, where ventilation was improved following the current ARM and PEEP only during high VT. Studies on the role of high VT on pulmonary complications are required.  相似文献   

2.

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   

3.

Objective

To evaluate the effects of an alveolar recruitment maneuver (ARM) followed by 5 cmH2O positive end-expiratory pressure (PEEP) in dogs undergoing laparoscopy.

Study design

Prospective, randomized clinical study.

Animals

A group of 20 dogs undergoing laparoscopic ovariectomy.

Methods

Dogs were sedated with acepromazine and methadone intramuscularly; anesthesia was induced with propofol intravenously and maintained with inhaled isoflurane. The following baseline ventilatory setting (BVS) was administered: tidal volume of 12 mL kg–1, inspiratory to expiratory ratio of 1:2, inspiratory pause 25% of inspiratory time, no PEEP and a respiratory rate to maintain end-tidal carbon dioxide tension between 5.3 and 7.3 kPa. Then, 10 minutes after the pneumoperitoneum, 10 dogs (RM) underwent a sustained inflation ARM followed by BVS plus 5 cmH2O PEEP, while 10 dogs (NO-RM) were left with BVS throughout the procedure. Gas exchange and respiratory system mechanics were evaluated before the pneumoperitoneum (PPpre), before ARM (PP10), 30 minutes later (PP30) and 20 minutes after pneumoperitoneum discontinuation (PPpost20). Data were analyzed using anova (p < 0.05).

Results

The Fshunt at PP30 and PPpost20 was lower (p < 0.001) in the RM (2.3 ± 2.2 and 4.7 ± 3.7%) than in the NO-RM (5.2 ± 2.1 and 11.1 ± 5.2%), and PaO2 at PP30 and PPpost20 was higher (p < 0.001) in the RM (67.3 ± 4.2 and 60.1 ± 9.4 kPa) than in the NO-RM (50.2 ± 7.4 and 45.5 ± 11.1 kPa). Static compliance of the respiratory system at PP30 and PPpost20 was greater (p < 0.001) in the RM (2.4 ± 0.2 and 2.1 ± 0.4 mL cmH2O?1 kg–1) than in the NO-RM (0.9 ± 0.4 and 1.2 ± 0.2 mL cmH2O?1 kg–1).

Conclusions and clinical relevance

In dogs undergoing laparoscopy, ARM followed by 5 cmH2O PEEP improves gas exchange and respiratory system mechanics.  相似文献   

4.

Objective

To compare the effects of controlled mechanical ventilation (CMV) and constant positive end-expiratory pressure (PEEP) and interposed recruitment manoeuvres (RMs) with those of CMV without PEEP on gas exchange during general anaesthesia and the early recovery period.

Study design

Prospective, randomized clinical trial.

Animals

A total of 48 Warmblood horses undergoing elective surgery in lateral (Lat) (n = 24) or dorsal (Dors) (n = 24) recumbency.

Methods

Premedication (romifidine), induction (diazepam and ketamine) and maintenance (isoflurane in oxygen) were identical in all horses. Groups Lat- CMV and Dors-CMV (each n = 12) were ventilated using CMV. Groups Lat-RM and Dors-RM (each n = 12) were ventilated using CMV with constant PEEP (10 cmH2O) and intermittent RMs (three consecutive breaths with peak inspiratory pressure of 60 cmH2O, 80 cmH2O and 60 cmH2O, respectively). RMs were applied as required to maintain PaO2 at > 400 mmHg (> 53.3 kPa). Dobutamine was given to maintain mean arterial blood pressure at > 60 mmHg. Physiological parameters were recorded every 10 minutes. Arterial blood gases were measured intra- and postoperatively. Statistical analyses were conducted using analyses of variance (anova), t tests and the Mann–Whitney U-test.

Results

Horses in Dors-RM had higher PaO2 values [478 ± 35 mmHg (63.7 ± 4.6 kPa)] than horses in Dors-CMV [324 ± 45 mmHg (43.2 ± 6 kPa)] during anaesthesia and the early recovery period. There were no differences between horses in groups Lat-CMV and Lat-RM. Other measured parameters did not differ between groups.

Conclusions and clinical relevance

Ventilation with CMV, constant PEEP and interposed RM provided improved arterial oxygenation in horses in dorsal recumbency that lasted into the early recovery period, but had no benefit in horses in lateral recumbency. This mode of ventilation may provide a clinically practicable method of improving oxygenation in anaesthetized horses, especially in dorsal recumbency.  相似文献   

5.

Objective

To examine changes in the distribution of ventilation and regional lung compliances in anaesthetized horses during the alveolar recruitment manoeuvre (ARM).

Study design

Experimental study in which a series of treatments were administered in a fixed order on one occasion.

Animals

Five adult Warmblood horses.

Methods

Animals were anaesthetized (xylazine, midazolam–ketamine, isoflurane), placed in dorsal recumbency and ventilated with 100% oxygen using peak inspiratory pressure (PIP) and positive end-expiratory pressure (PEEP) of 20 cmH2O and 0 cmH2O, respectively. Thoracic electrical impedance tomography (EIT), spirometry and routine anaesthesia monitoring were performed. At 90 minutes after induction of anaesthesia, PIP and PEEP were increased in steps of 5 cmH2O to 50 cmH2O and 30 cmH2O, respectively, and then decreased to baseline values. Each step lasted 10 minutes. Data were recorded and functional EIT images were created using three breaths at the end of each step. Arterial blood samples were analysed. Values for left-to-right and sternal-to-dorsal centre of ventilation (COV), lung compliances and Bohr dead space were calculated.

Results

Distribution of ventilation drifted leftward and dorsally during recruitment. Mean ± standard deviation (SD) values at baseline and highest airway pressures, respectively, were 49.9 ± 0.7% and 48.0 ± 0.6% for left-to-right COV (p = 0.009), and 46.3 ± 2.0% and 54.6 ± 2.0% for sternal-to-dorsal COV (p = 0.0001). Compliance of dependent lung regions and PaO2 increased, whereas compliance of non-dependent lung regions decreased during ARM and then returned to baseline (p < 0.001). Bohr dead space decreased after ARM (p = 0.007). Interestingly, PaO2 correlated to the compliance of the dependent lung (r2 = 0.71, p < 0.001).

Conclusions and clinical relevance

The proportion of tidal volume distributed to dependent and left lung regions increased during ARM, presumably as a result of opening atelectasis. Monitoring compliance of the dependent lung with EIT may substitute PaO2 measurements during ARM to identify an optimal PEEP.  相似文献   

6.

Objective

To investigate the effects of pneumoperitoneum alone or combined with an alveolar recruitment maneuver (ARM) followed by positive end-expiratory pressure (PEEP) on cardiopulmonary function in sheep.

Study design

Prospective, randomized, crossover study.

Animals

A total of nine adult sheep (36–52 kg).

Methods

Sheep were administered three treatments (≥10-day intervals) during isoflurane–fentanyl anesthesia and volume-controlled ventilation (tidal volume: 12 mL kg?1) with oxygen: CONTROL (no intervention); PNEUMO (120 minutes of CO2 pneumoperitoneum); PNEUMOARM/PEEP (PNEUMO protocol with an ARM instituted after 60 minutes of pneumoperitoneum). The ARM (5 cmH2O increases in PEEP of 1 minute duration until 20 cmH2O of PEEP) was followed by 10 cmH2O of PEEP until the end of anesthesia. Cardiopulmonary data were recorded until 30 minutes after abdominal deflation.

Results

PaO2 was decreased from 435–462 mmHg (58.0–61.6 kPa) (range of mean values in CONTROL) to 377–397 mmHg (50.3–52.9 kPa) in PNEUMO (p < 0.05). Quasistatic compliance (Cqst, mL cmH2O?1 kg?1) was decreased from 0.85–0.92 in CONTROL to 0.52–0.58 in PNEUMO. PaO2 increased from 383–385 mmHg (51.1–51.3 kPa) in PNEUMO to 429–444 mmHg (57.2–59.2 kPa) in PNEUMOARM/PEEP (p < 0.05) and Cqst increased from 0.52–0.53 in PNEUMO to 0.70–0.74 in PNEUMOARM/PEEP. Abdominal deflation in PNEUMO did not restore PaO2 and Cqst to control values. Cardiac index (L minute?1 m2) decreased from 4.80–4.70 in CONTROL to 3.45–3.74 in PNEUMO and 3.63–3.76 in PNEUMOARM/PEEP. Compared with controls, ARM/PEEP with pneumoperitoneum decreased mean arterial pressure from 81 to 68 mmHg and increased mean pulmonary artery pressure from 10 to 16 mmHg.

Conclusions and clinical relevance

Abdominal deflation did not reverse the pulmonary function impairment associated with pneumoperitoneum. The ARM/PEEP improved respiratory compliance and reversed the oxygenation impairment induced by pneumoperitoneum with acceptable hemodynamic changes in healthy sheep.  相似文献   

7.

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   

8.

Objective

The aim of this study was to evaluate the effect of continuous positive airway pressure (CPAP) on regional distribution of ventilation and dead space in anaesthetized horses.

Study design

Randomized, experimental, crossover study.

Animals

A total of eight healthy adult horses.

Methods

Horses were anaesthetized twice with isoflurane in 50% oxygen and medetomidine as continuous infusion in dorsal recumbency, and administered in random order either CPAP (8 cmH2O) or NO CPAP for 3 hours. Electrical impedance tomography (and volumetric capnography (VCap) measurements were performed every 30 minutes. Lung regions with little ventilation [dependent silent spaces (DSSs) and nondependent silent spaces (NSSs)], centre of ventilation (CoV) and dead space variables, as well as venous admixture were calculated. Statistical analysis was performed using multivariate analysis of variance and Pearson correlation.

Results

Data from six horses were statistically analysed. In CPAP, the CoV shifted to dependent parts of the lungs (p < 0.001) and DSSs were significantly smaller (p < 0.001), while no difference was seen in NSSs. Venous admixture was significantly correlated with DSS with the treatment time taken as covariate (p < 0.0001; r = 0.65). No differences were found for any VCap parameters.

Conclusions and clinical relevance

In dorsally recumbent anaesthetized horses, CPAP of 8 cmH2O results in redistribution of ventilation towards the dependent lung regions, thereby improving ventilation-perfusion matching. This improvement was not associated with an increase in dead space indicative for a lack in distension of the airways or impairment of alveolar perfusion.  相似文献   

9.

Objective

To establish a noninvasive imaging protocol for rabbit gastrointestinal transit evaluation. To assess the effect of a single injection of buprenorphine on the digestive transit of rabbits via this new technique.

Study design

Prospective, parallel study.

Animals

Fifteen specific pathogen-free male New Zealand White rabbits weighing 2.68 ± 0.28 kg.

Methods

A 10 mL kg–1 barium meal was administered and the rabbits were subjected to serial radiographic and ultrasound examinations without treatment and 1 week later following a single intramuscular dose of 100 μg kg–1 of buprenorphine. Radiographic data from the stomach and caecum were collected and assigned a retention score ranging from 0 (no barium) to 3 (large amount of barium). The resulting scores and pyloric and duodenal contraction counts were analysed using a mixed linear model and are expressed as least square mean (lsm) ± standard error. Transit was estimated based on the apparition time of faeces in the pelvic area and analysed using a Wilcoxon test. A p < 0.05 was considered significant.

Results

Buprenorphine treatment induced a higher lsm number of pyloric (1.73 ± 0.19 versus 0.78 ± 0.19, p < 0.01) and lsm duodenal contractions (17.35 ± 1.04 versus 13.44 ± 1.04, p < 0.01). Buprenorphine administration decreased the lsm barium retention score in the stomach (2.44 ± 0.05 versus 2.64 ± 0.05, p < 0.01), but had no effect on the lsm barium retention score in the caecum. The time to apparition of faeces in the pelvic area was not influenced by buprenorphine administration (p = 0.66).

Conclusions and clinical relevance

A single high dose of buprenorphine appears to have no adverse effect on gastrointestinal motility in healthy rabbits.  相似文献   

10.

Objectives

To investigate whether acupuncture can alter gait in horses as assessed by objective and subjective parameters.

Study design

Prospective, randomized, singleblinded, crossover study.

Animals

Eight adult horses.

Methods

Horses were randomly assigned to a treatment (three acupuncture treatments in 8 days) or control group. Subjective and objective gait analyses were performed before and after each treatment and at 1, 3 and 7 days after the last treatment (time-points 1–9, respectively). Horses were assessed at the trot in a straight line on a hard surface and on the lunge on the left and right reins on a soft surface (conditions 1–3, respectively). After 12 weeks, groups were reversed. Objective gait analysis was performed using inertial sensors and subjective analysis by two board- certified surgeons who reviewed video-recordings. Each limb was assessed for lameness before and after treatment. Lameness and global scores were assigned using 4-point scales. Assessors were blinded to treatment status. The effects of treatment (yes/no), time (1–9) and horse under conditions 1 –3 were compared using a linear mixed-effects model and a generalized estimating equation.

Results

Treatment decreased hip hike difference under all conditions [condition 1: control, 6.3 ± 6.4 mm versus treatment, –0.2 ± 6.4 mm (p = 0.007); condition 2: control, 9.7 ± 7.8 mm versus treatment, 2.8 ± 7.8 mm (p = 0.032); condition 3: control, 7.3 ± 6.3 mm versus treatment, –2.7 ± 6.4 mm (p = 0.003)]. Other parameters also improved significantly under conditions 1 and 3. Based on subjective gait analysis, treatment decreased lameness [odds ratio (OR) 0.51, 95% confidence interval (CI) 0.34–0.78; p = 0.002] but not global (OR 0.53, 95% CI 0.24–1.10; p = 0.12) scores.

Conclusions and clinical relevance

Acupuncture can change horses' gaits to a degree appreciable by objective and subjective analyses.  相似文献   

11.

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   

12.

Objective

To compare the efficacy of three continuous positive airway pressure (CPAP) interfaces in dogs on gas exchange, lung volumes, amount of leak during CPAP and rebreathing in case of equipment failure or disconnection.

Study design

Randomized, prospective, crossover, experimental trial.

Animals

Ten purpose-bred Beagle dogs.

Methods

Dogs were in dorsal recumbency during medetomidine–propofol constant rate infusions, breathing room air. Three interfaces were tested in each dog in a consecutive random order: custom-made mask (M), conical face mask (FM) and helmet (H). End-expiratory lung impedance (EELI) measured by electrical impedance tomography was assessed with no interface (baseline), with the interface only (No-CPAP for 3 minutes) and at 15 minutes of 7 cmH2O CPAP (CPAP-delivery). PaO2 was assessed at No-CPAP and CPAP-delivery, partial pressure of inspired carbon dioxide (PICO2; rebreathing assessment) at No-CPAP and the interface leak (ΔPleak) at CPAP-delivery. Mixed-effects linear regression models were used for statistical analysis (p < 0.05).

Results

During CPAP-delivery, all interfaces increased EELI by 7% (p < 0.001). Higher ΔPleak was observed with M and H (9 cmH2O) in comparison with FM (1 cmH2O) (p < 0.001). At No-CPAP, less rebreathing occurred with M (0.5 kPa, 4 mmHg) than with FM (1.8 kPa, 14 mmHg) and with H (1.4 kPa, 11 mmHg), but also lower PaO2 was measured with M (9.3 kPa, 70 mmHg) than with H (11.9 kPa, 90 mmHg) and FM (10.8 kPa, 81 mmHg).

Conclusions and clinical relevance

All three interfaces can be used to provide adequate CPAP in dogs. The leak during CPAP-delivery and the risk of rebreathing and hypoxaemia, when CPAP is not maintained, can be significant. Therefore, animals should always be supervised during administration of CPAP with any of the three interfaces. The performance of the custom-made M was not superior to the other interfaces.  相似文献   

13.

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   

14.

Objective

The effect of user experience and inflation technique on endotracheal tube cuff pressure using a feline airway simulator.

Study design

Prospective, experimental clinical study.

Methods

Participants included veterinary students at the beginning (group S1) and end (group S2) of their 2-week anaesthesia rotation and veterinary anaesthetists (group A). The feline airway simulator was designed to simulate an average size feline trachea, intubated with a 4.5 mm low-pressure, high-volume cuffed endotracheal tube, connected to a Bain breathing system with oxygen flow of 2 L minute?1. Participants inflated the on-endotracheal tube cuff by pilot balloon palpation and by instilling the minimum occlusive volume (MOV) required for loss of airway leaks during manual ventilation. Intracuff pressures were measured by manometers obscured to participants and ideally were 20–30 cm H2O. Student t, Fisher exact, and Chi-squared tests were used where appropriate to analyse data (p < 0.05).

Results

Participants were 12 students and eight anaesthetists. Measured intracuff pressures for palpation and MOV, respectively, were 19 ± 12 and 29 ± 19 cm H2O for group S1, 10 ± 5 and 20 ± 11 cm H2O for group S2 and 13 ± 6 and 29 ± 18 cm H2O for group A. All groups performed poorly at achieving intracuff pressures within the ideal range. There was no significant difference in intracuff pressures between techniques. Students administered lower (p = 0.02) intracuff pressures using palpation after their training.

Conclusions and clinical relevance

When using palpation and MOV for cuff inflation operators rarely achieved optimal intracuff pressures. Experience had no effect on this skill and, as such, a cuff manometer is recommended.  相似文献   

15.

Objective

To compare the cardiopulmonary effects of low and high doses of fentanyl before and after the correction of bradycardia in isoflurane-anesthetized dogs.

Study design

Prospective, randomized crossover trial.

Animals

Eight healthy male Beagle dogs weighing 11.1 ± 1.3 kg [mean ± standard deviation (SD)] and aged approximately 1 year.

Methods

The dogs were anesthetized with isoflurane [1.3 × minimum alveolar concentration (MAC)] on two occasions and fentanyl was administered intravenously; either low-dose fentanyl, loading dose (33 μg kg–1) and infusion (0.2 μg kg–1 minute–1) or a high-dose, loading dose (102 μg kg–1) and infusion (0.8 μg kg–1 minute–1). Cardiopulmonary variables were measured at three time points in equipotent isoflurane concentrations (1.3 MAC): before fentanyl administration (ISO), during fentanyl-induced bradycardia (ISO–F) and after administration of glycopyrrolate normalized heart rate (ISO–FNHR). Data are mean ± SD.

Results

Heart rate and cardiac index (CI) decreased and systemic vascular resistance index (SVRI) increased at ISO–F in both treatments. Bradycardia and vasoconstriction at ISO–F were greater in high than in low-dose fentanyl (42 ± 7 versus 57 ± 15 beats minute–1 and 3457 ± 1108 versus 2528 ± 968 dyne second cm–5 m–2), respectively. Oxygen delivery index (DO2I) decreased only during high-dose fentanyl. CI and DO2I were higher in both treatments at ISO–FNHR than at ISO–F; however, they were higher only during the high-dose fentanyl than at ISO. SVRI was higher at ISO–F than at ISO and ISO–FNHR in both treatments, and was higher at ISO–F in the high than in the low-dose treatment.

Conclusions and clinical relevance

An overall improvement in cardiovascular function of dogs anesthetized with equipotent isoflurane doses (1.3 MAC) was observed after the treatment of bradycardia only with the high-dose fentanyl.  相似文献   

16.

Objective

To characterize the hemodynamic effects of dexmedetomidine, with or without MK-467, following intramuscular (IM) administration in cats.

Study design

Randomized, crossover, experimental study.

Animals

Six healthy adult male castrated purpose-bred cats.

Methods

Cats were anesthetized with isoflurane in oxygen and instrumented. Cats were administered dexmedetomidine (25 μg kg?1), with (DM) or without (D) MK-467 (600 μg kg?1), IM in the epaxial muscles. Cardiovascular variables, respiratory variables, temperature, and arterial and mixed-venous pH, blood gases and electrolytes were measured prior to drug administration and at various time points for 6 hours thereafter, during anesthesia with isoflurane. Additional variables were calculated from the measurements, using standard equations. Results were analyzed with a two-way repeated-measures analysis of variance, followed by Dunnett’s and paired t tests where appropriate.

Results

Dexmedetomidine resulted in a significant decrease in cardiac index (CI) and significant increases in mean arterial pressure (MAP) and systemic vascular resistance index (SVRI). The addition of MK-467 failed to prevent most of the early cardiovascular effects of dexmedetomidine, but the duration of systemic vasoconstriction was shorter and CI did not decrease. The lowest and highest post-treatment values in each treatment were 0.1 ± 0.03 and 0.13 ± 0.03 L minute?1 BW?0.67 (D) versus 0.14 ± 0.01 and 0.19 ± 0.03 L minute?1 BW?0.67 (DM) for CI, 87 ± 13 and 181 ± 21 mmHg (D) versus 70 ± 11 and 153 ± 18 mmHg (DM) for MAP and 58,948 ± 17,754 and 119,432 ± 40,423 dynes second cm?5 BW?0.67 (D) versus 25,870 ± 3782 and 76,498 ± 17,258 dynes second cm?5 BW?0.67 (DM) for SVRI, respectively.

Conclusion and clinical relevance

IM coadministration of MK-467 and dexmedetomidine in isoflurane-anesthetized cats shortened dexmedetomidine-induced cardiovascular effects. This drug combination may be useful in cats in which longer-lasting hypertension and hemodynamic depression is of concern.  相似文献   

17.

Objective

To examine the effect of sternal or lateral recumbency, with or without cranial extension of the hindlimbs, on the distance between the dorsal lumbosacral laminae in dogs.

Study design

Blinded, randomized, crossover, experimental study.

Animals

A total of 19 canine cadavers.

Methods

Computed tomography of the lumbosacral junction was performed in four positions: sternal and right lateral recumbency, with hindlimbs extended cranially or not. Order of positioning was randomized. The lumbosacral interlaminar (LSI) distance, defined as the distance between the dorsal laminae of the seventh lumbar vertebra (caudal margin) and sacrum (cranial margin), was measured for each position by two independent assessors who were unaware of positioning. Mean distances in each position were compared using a paired t-test, corrected for multiple comparisons.

Results

For n = 19 cadavers [6 female; median (range) age 9 (0.3–16) years; weight, 20.4 (1.0–34.0) kg], cranial extension of the hindlimbs increased the LSI distance, compared with control, in both sternal (9.2 ± 2.2 mm versus 3.1 ± 1.3 mm, p < 0.001) and right lateral recumbency (8.2 ± 1.9 mm versus 4.9 ± 1.5 mm, p < 0.001). With the hindlimbs extended cranially, sternal recumbency increased LSI distance when compared with right lateral recumbency (p < 0.001).

Conclusions and clinical relevance

Cranial extension of the hindlimbs in both sternal and lateral recumbency increases the LSI distance to an extent that is both statistically significant and of potential clinical relevance. Although ease of epidural access or injection was not assessed, the small (1 mm) difference in LSI distance between cranial hindlimb extension in sternal and right lateral recumbency is unlikely to be of clinical relevance. Conversely, cranial extension of the hindlimbs in either sternal or lateral recumbency would be expected to facilitate epidural injection.  相似文献   

18.

Objective

To test whether neurotoxic effects of a bupivacaine liposome injectable suspension differ from those of a standard formulation of bupivacaine hydrochloride (HCl) after intraneural injection into the sciatic nerves in pigs.

Study design

Prospective, randomized study.

Animals

Fifteen pigs, hybrids of Landrace and Large White.

Methods

After the National Ethics Committee approval, 15 pigs were randomly allocated to three groups (n = 5/group) to receive intraneural injections of 4 mL of 1.33% bupivacaine liposome injectable suspension, 0.5% bupivacaine HCl or normal saline. Serial neurologic examinations were conducted to detect sensory and motor response to noxious stimuli using a modified Thalhammer’s scale at 2 hour intervals for the first 12 hours after injection and daily thereafter for 2 weeks. Fiber characteristics (density) of the harvested sciatic nerves were measured during histomorphometric analysis. Inflammatory response was studied using immunohistochemical analysis. Data were tested using analyses of variance; p values for paired comparisons were Bonferroni adjusted.

Results

Compared with bupivacaine HCl, bupivacaine liposome injectable suspension provided longer sensory (11.2 ± 1.8 hours versus 3.2 ± 1.1 hours, respectively, p < 0.0001) and motor (10.0 ± 2.0 hours versus 4.0 ± 1.4 hours respectively, p < 0.0001) blockade. Histomorphometric parameters were similar among the groups. No changes in axonal density or myelin structure indicative of injury to the sciatic nerves were observed in any of the groups. Number of immunopositive cells did not differ between the bupivacaine liposome injectable suspension (23 ± 6 cells per mm2) and the bupivacaine HCl groups (21 ± 4 cells per mm2), p > 0.90.

Conclusions and clinical relevance

Intraneural injections of bupivacaine liposome injectable suspension or bupivacaine HCl in our porcine model did not result in evidence of neurotoxicity.  相似文献   

19.

Objective

To compare the effect of propofol and ketamine/diazepam for induction following premedication on intraocular pressure (IOP) in healthy dogs.

Study design

Prospective, quasi-experimental, unmasked, longitudinal.

Animals

A total of 61 client-owned dogs.

Methods

Dogs were anesthetized twice with a 4 week washout period. Premedication with dexmedetomidine (5 μg kg–1) and hydromorphone (0.1 mg kg–1) intramuscularly was followed by either propofol (4 mg kg–1) or ketamine (5 mg kg–1) and diazepam (0.25 mg kg–1) intravenously for induction and inhaled isoflurane for maintenance. IOP was measured by applanation tonometry using TonoPen-XL before premedication and after 5, 10, 20 and 30 minutes. IOP was measured again immediately after induction and after 3, 5, 10, 15, 20, 30 and 40 minutes. Data were analyzed using one- or two-way repeated measures ANOVA.

Results

No difference was found between right and left IOP (p = 0.45), and data from both the eyes of each dog were averaged and considered as one set of data. Following premedication, IOP was significantly lower at all time points than at baseline when animals were grouped together, mean difference –1.6 ± 0.2 mmHg (p < 0.05). IOP increased immediately (12.2 ± 2.4 mmHg before versus 17.1 ± 3.8 mmHg after) and at 3, 5 (p < 0.001), 10 and 40 minutes (p = 0.009 and 0.045, respectively) after propofol administration. For ketamine/diazepam, IOP was increased immediately post-induction (13.0 ± 2.7 mmHg before versus 14.7 ± 2.8 mmHg after) and at 3, 5 (p < 0.001), 30 and 40 minutes (p = 0.010 and 0.037, respectively).

Conclusions and clinical relevance

Sedation with hydromorphone and dexmedetomidine significantly decreased IOP in normal dogs and may be an appropriate choice for dogs that cannot tolerate acute increases in IOP. However, IOP increased significantly after both induction protocols, abolishing the effect of premedication.  相似文献   

20.

Objective

To compare the induction and recovery characteristics and selected cardiopulmonary variables of midazolam–alfaxalone or midazolam–ketamine in donkeys sedated with xylazine.

Study design

Randomized, blinded, crossover experimental trial.

Animals

A group of seven adult male castrated donkeys weighing 164 ± 14 kg.

Methods

Donkeys were randomly administered midazolam (0.05 mg kg?1) and alfaxalone (1 mg kg?1) or midazolam (0.05 mg kg?1) and ketamine (2.2 mg kg?1) intravenously following sedation with xylazine, with ≥ 7 days between treatments. Donkeys were not endotracheally intubated and breathed room air. Time to lateral recumbency, first movement, sternal recumbency and standing were recorded. Induction and recovery were assigned scores between 1 (very poor) and 5 (excellent). Heart rate (HR), respiratory rate (fR), invasive arterial blood pressures and arterial blood gases were measured before induction and every 5 minutes following induction until first movement.

Results

Time to lateral recumbency (mean ± standard deviation) was shorter after alfaxalone (29 ± 10 seconds) compared with ketamine (51 ± 9 seconds; p = 0.01). Time to first movement was the same between treatments (27 versus 23 minutes). Time to standing was longer with alfaxalone (58 ± 15 minutes) compared with ketamine (33 ± 8 minutes; p = 0.01). Recovery score [median (range)] was of lower quality with alfaxalone [3 (2–5)] compared with ketamine [5 (3–5); p = 0.03]. There were no differences in HR, fR or arterial pressures between treatments. No clinically important differences in blood gases were identified between treatments. Five of seven donkeys administered alfaxalone became hypoxemic (PaO2 <60 mmHg; 8.0 kPa) and all donkeys administered ketamine became hypoxemic (p = 0.13).

Conclusions and clinical relevance

Both midazolam–alfaxalone and midazolam–ketamine produced acceptable anesthetic induction and recovery in donkeys after xylazine sedation. Hypoxemia occurred with both treatments.  相似文献   

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