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Vet Anaesth Analg [journal]
- Chronotropic effect of propofol or alfaxalone following fentanyl administration in healthy dogs. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2014 Apr 16.
To compare the effect of alfaxalone and propofol on heart rate (HR) and blood pressure (BP) after fentanyl administration in healthy dogs.Prospective, randomised clinical study.Fifty healthy client owned dogs (ASA I/II) requiring general anaesthesia for elective magnetic resonance imaging for neurological conditions.All dogs received fentanyl 7 μg kg(-1) IV and were allocated randomly to receive either alfaxalone (n = 25) or propofol (n = 25) to effect until endotracheal (ET) intubation was possible. Heart rate and oscillometric BP were measured before fentanyl (baseline), after fentanyl (Time F) and after ET intubation (Time GA). Post-induction apnoea were recorded. Data were analysed using Fisher's exact test, Mann Whitney U test and one-way anova for repeated measures as appropriate; p value <0.05 was considered significant.Dogs receiving propofol showed a greater decrease in HR (-14 beat minute(-1) , range -47 to 10) compared to alfaxalone (1 beat minute(-1) , range -33 to 26) (p = 0.0116). Blood pressure decreased over the three time periods with no difference between groups. Incidence of post-induction apnoea was not different between groups.Following fentanyl administration, anaesthetic induction with propofol resulted in a greater negative chronotropic effect while alfaxalone preserved or increased HR.Following fentanyl administration, HR decreases more frequently when propofol rather than alfaxalone is used as induction agent. However, given the high individual variability and the small change in predicted HR (-7.7 beats per minute after propofol), the clinical impact arising from choosing propofol or alfaxalone is likely to be small in healthy animals. Further studies in dogs with myocardial disease and altered haemodynamics are warranted.
- Pharmacokinetic-pharmacodynamic modelling of intravenous buprenorphine in conscious horses. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2014 Apr 16.
Describe the pharmacokinetics of buprenorphine and norbuprenorphine in horses and to relate the plasma buprenorphine concentration to the pharmacodynamic effects.Single phase non-blinded study.Six dedicated research horses, aged 3-10 years and weighing 480-515 kg.Thermal and mechanical nociceptive thresholds, heart and respiratory rates and locomotor activity were measured before and 15, 30, 45 & 60 minutes and 2, 4, 6, 8, 12 & 24 hours post-administration of 10 μg kg(-1) buprenorphine IV. Intestinal motility was measured 1, 6, 12 & 24 hours after buprenorphine administration. Venous blood samples were obtained before administration of buprenorphine 10 μg kg(-1) IV and 1, 2, 4, 6, 10, 15, 30, 45 & 60 minutes, and 2, 4, 6, 8, 12 & 24 hours afterwards. Plasma buprenorphine and norbuprenorphine concentrations were measured using a liquid chromatography-tandem mass spectroscopy (LC-MS/MS) assay with solid-phase extraction. A non-compartmental method was used for analysis of the plasma concentration-time data and plasma buprenorphine concentrations were modelled against two dynamic effects (change in thermal threshold and mechanical threshold) using a simple Emax model.Plasma buprenorphine concentrations were detectable to 480 minutes in all horses and to 720 minutes in two out of six horses. Norbuprenorphine was not detected. Thermal thresholds increased from 15 minutes post-buprenorphine administration until the 8-12 hour time points. The increase in mechanical threshold ranged from 3.5 to 6.0 Newtons (median: 4.4 N); and was associated with plasma buprenorphine concentrations in the range 0.34-2.45 ng mL(-1) .The suitability of the use of buprenorphine for peri-operative analgesia in the horse is supported by the present study.
- Utility of transesophageal electrocardiography to guide optimal placement of a transesophageal pacing catheter in dogs. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2014 Apr 16.
To determine if the transesophageal atrial (A) wave amplitude or ventricular (V) wave amplitude can be used to guide optimal positioning of a transesophageal pacing catheter in dogs.Prospective clinical study.Fourteen client owned healthy dogs with a median weight of 15.4 kg (IQR = 10.6-22.4) and a median age of 12 months (IQR = 6-12).Transesophageal atrial pacing (TAP) using a 6 Fr pacing catheter was attempted in dogs under general anesthesia. The pacing catheter was inserted orally into the esophagus to a position caudal to the heart. With the pulse generator set at a rate 20 beats minute(-1) above the intrinsic sinus rate, the catheter was slowly withdrawn until atrial pacing was noted on a surface electrocardiogram (ECG). Then the catheter was withdrawn in 1 cm increments until atrial capture was lost. Minimum pacing threshold (MPT) and transesophageal ECG were recorded at each site. Amplitudes of the A and V waves on transesophageal ECG were then measured and their relationship to MPT was evaluated.TAP was achieved in all dogs. In 9/14 dogs the site of lowest overall MPT was the same as the site of maximal A wave deflection. In dogs with at least three data points, linear regression analysis of the relationship between the estimated site of the lowest overall MPT compared to estimated site of the maximal A and V waveform amplitudes demonstrated a strong correlation (R(2) = 0.99).Transesophageal ECG A and V waveforms were correlated to MPT and could be used to direct the placement of a pacing catheter. However, the technique was technically challenging and was not considered to be clinically useful to guide the placement of a pacing catheter.
- Handheld mechanical nociceptive threshold testing in dairy cows - intra-individual variation, inter-observer agreement and variation over time. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2014 Apr 16.
To examine the use of handheld methodology to assess mechanical nociceptive threshold (MNT) on cows kept loose-housed.Prospective randomized partial cross-over experimental study. A one-factor (test day) design was used to evaluate MNT over time.One hundred and fifteen healthy, loose-housed Danish Holstein cattle.We evaluated intra-individual variation, inter-observer agreement and variation over time of MNT using two handheld devices and two stimulation sites. Mechanical, ramped stimulations were performed with an algometer (6.5 mm diameter steel probe, 0-10.0 kgf) or an electronic von Frey device (plastic tip with diameter 0.8 mm, 0-1000 gf). Each cow received 5-6 consecutive stimulations within a 2 × 5 cm skin area on the dorsal or lateral aspect of the left third metatarsus until an avoidance reaction occurred. We investigated the difference in precision [expressed as coefficient of variation (CV)] between the combinations of devices and stimulation sites. The inter-observer agreement and the difference in MNT between test day 1, 3, 7, 10 and 24 were investigated for selected combinations. Data were analysed in mixed models and Bland-Altman as relevant.The CVs did not differ [range 0.34-0.52 (p = 0.1)]. Difference between observers (95% limits) was 0.2 kgf (2.8) and 4 gf (369) for the algometer and von Frey device, respectively. Mechanical nociceptive threshold increased from 361 on test day one to 495 gf on test day 24 (p < 0.01).All methods showed a high degree of intra-individual variation, and no combination of device and stimulation site showed superior precision. Mean difference between observers was low, and MNT was not consistent over time. Further development of the methods is required before they can be used in research to investigate possible relations between claw lesions and hyperalgesia.
- Cardiopulmonary effects during anaesthesia induced and maintained with propofol in acepromazine pre-medicated donkeys. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2014 Apr 16.
To evaluate the cardiopulmonary effects of anaesthesia induced and maintained with propofol in acepromazine pre-medicated donkeys.Prospective experimental study.Six healthy male donkeys weighing 78-144 kg.Donkeys were pre-medicated with intravenous (IV) acepromazine (0.04 mg kg(-1) ). Ten minutes later, anaesthesia was induced with IV propofol (2 mg kg(-1) ) and anaesthesia maintained by continuous IV infusion of the propofol (0.2 mg kg(-1) minute(-1) ) for 30 minutes. Baseline measurements of physiological parameters, and arterial blood samples were taken before the acepromazine administration, then 5, 15, 30, 45, and 60 minutes after the induction of anaesthesia. Changes from baseline were analysed by anova for repeated measures.When compared with baseline (standing) values, during anaesthesia heart rate increased throughout: significant at 5 (p = 0.001) and 15 (p = 0.015) minutes. Mean arterial blood pressure increased significantly only at 15 minutes (p < 0.001). Respiratory rate and arterial pH did not change significantly. PaO2 was lower throughout anaethesia, but this only reached significance at 15 minutes (p = 0.041). PaCO2 was statistically (but not clinically) significantly reduced at the times of 30 (p = 0.02), 45 (p = 0.01) and 60 (p = 0.04). Rectal temperature decreased significantly at all times of the study.Administration of propofol by the continuous infusion rate for the maintenance of anaesthesia resulted in stable cardiopulmonary effects and could prove to be clinically useful in donkeys.
- Evaluation of analgesic and physiologic effects of epidural morphine administered at a thoracic or lumbar level in dogs undergoing thoracotomy. [Journal Article]
- Vet Anaesth Analg 2014 Mar; 41(2):205-11.
To evaluate the analgesic and physiological effects of epidural morphine administered at the sixth and seventh lumbar or the fifth and sixth thoracic vertebrae in dogs undergoing thoracotomy.Prospective, randomized, blinded trial.Fourteen mixed-breed dogs, weighing 8.6 ± 1.4 kg.The animals received acepromazine (0.1 mg kg⁻¹) IM and anesthesia was induced with propofol (4 mg kg)⁻¹ IV. The lumbosacral space was punctured and an epidural catheter was inserted up to the region between the sixth and seventh lumbar vertebrae (L, n = 6) or up to the fifth or sixth intercostal space (T, n = 8). The dogs were allowed to recover and after radiographic confirmation of correct catheter position, anesthesia was reinduced with propofol IV and maintained with 1.7% isoflurane. Following stabilization of monitored parameters, animals received morphine (0.1 mg kg⁻¹) diluted in 0.9% NaCl to a final volume of 0.25 mL kg⁻¹ via the epidural catheter, and after 40 minutes, thoracotomy was initiated. Heart rate and rhythm, systolic, mean and diastolic arterial pressures, respiratory rate, arterial hemoglobin oxygen saturation, partial pressure of expired CO₂ and body temperature were measured immediately before the epidural administration of morphine (0 minute) and every 10 minutes during the anesthetic period. The Melbourne pain scale and the visual analog scale were used to assess postoperative pain. The evaluation began 3 hours after the epidural administration of morphine and occurred each hour until rescue analgesia.There were no important variations in the physiological parameters during the anesthetic period. The post-operative analgesic period differed between the groups, being longer in T (9.9 01.6 hours) compared with L (5.8 ± 0.8 hours).The use of morphine, at a volume of 0.25 mL kg 0.1, administered epidurally over the thoracic vertebrae provided longer lasting analgesia than when deposited over the lumbar vertebrae.
- Variety of non-invasive continuous monitoring methodologies including electrical impedance tomography provides novel insights into the physiology of lung collapse and recruitment – case report of an anaesthetized horse. [Journal Article]
- Vet Anaesth Analg 2014 Mar; 41(2):196-204.
The use of alveolar recruitment maneuvers during general anaesthesia of horses is a potentially useful therapeutic option for the ventilatory management. While the routine application of recruitments would benefit from the availability of dedicated large animal ventilators their impact on ventilation and perfusion in the horse is not yet well documented nor completely understood.A healthy 533 kg experimental horse underwent general anaesthesia in lateral recumbency. During intermittent positive pressure ventilation a stepwise alveolar recruitment maneuver was performed.Anaesthesia was induced with ketamine and midazolam and maintained with isoflurane in oxygen using a large animal circle system. Mechanical ventilation was applied in pressure ventilation mode and an alveolar recruitment maneuver performed employing a sequence of ascending and descending positive end expiratory pressures. Next to the standard monitoring, which included spirometry, additionally three non-invasive monitoring techniques were used: electrical impedance tomography (EIT), volumetric capnography and respiratory ultrasonic plethysmography. The functional images continuously delivered by EIT initially showed markedly reduced ventilation in the dependent lung and allowed on-line monitoring of the dynamic changes in the distribution of ventilation during the recruitment maneuver. Furthermore, continuous monitoring of compliance, dead space fraction, tidal volumes and changes in end expiratory lung volume were possible without technical difficulties. FOLLOW: up The horse made an unremarkable recovery.The novel non-invasive monitoring technologies used in this study provided unprecedented insights into the physiology of lung collapse and recruitment. The synergic information of these techniques holds promise to be useful when developing and evaluating new ventilatory strategies in horses.
- Determination of the Minimum Infusion Rate (MIR) of alfaxalone required to prevent purposeful movement of the extremities in response to a standardised noxious stimulus in goats. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2014 Mar 28.
To determine the minimum infusion rate (MIR) of alfaxalone required to prevent purposeful movement of the extremities in response to noxious stimulation.Prospective, experimental.Eight healthy goats; four does and four wethers.Anaesthesia was induced with alfaxalone 3 mg kg(-1) intravenously (IV). A continuous IV infusion of alfaxalone, initially at 0.2 mg kg(-1) minute(-1) , was initiated. Following endotracheal intubation the goats breathed spontaneously via a circle breathing circuit delivering supplementary oxygen. The initial infusion rate was maintained for 30 minutes before testing for responses. The stimulus was clamping on the proximal (soft) part of one digit of the hoof with Vulsellum forceps for 60 seconds. In the absence or presence of purposeful movement of the extremities, the infusion rate was reduced or increased by 0.02 mg kg(-1) minute(-1) and held constant for 30 minutes before claw-clamping again. Alfaxalone MIR was calculated as the mean of the infusion rates that allowed and abolished movement. Cardio-respiratory parameters were measured. Recovery from general anaesthesia was timed and quality scored. Results are presented as median (range).The MIR of alfaxalone was 0.16 (0.14-0.18) mg kg(-1) minute(-1) or 9.6 (8.4-10.8) mg kg(-1) hour(-1) . Induction of and recovery from anaesthesia were excitement-free. Cardio-respiratory changes were minimal, although compared to baseline HR increased, and at 2 minutes post-induction, (prior to oxygen supplementation), PaO2 decreased significantly from 84 (80-88) to 70 (51-72) mmHg [11.2 (10.7-11.7) to 9.3 (6.8-9.6) kPa]. Sporadic muscle twitches, unrelated to depth of anaesthesia, were observed during the period of general anaesthesia. Time (minutes) to sternal recumbency and standing were 4.0 (3.0-10.0) and 41.5 (25.0-57.0) respectively.Alfaxalone can be used for total intravenous anaesthesia (TIVA) in goats and is associated with minimal adverse effects. Oxygen supplementation is advised, especially when working at higher altitudes.
- The cardiopulmonary effects of a peripheral alpha-2-adrenoceptor antagonist, MK-467, in dogs sedated with a combination of medetomidine and butorphanol. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2014 Mar 28.
To compare the cardiopulmonary effects of intravenous (IV) and intramuscular (IM) medetomidine and butorphanol with or without MK-467.Prospective, randomized experimental cross-over.Eight purpose-bred beagles (two females, six males), 3-4 years old and weighing 14.5 ±1.6 kg (mean ± SD).All dogs received four different treatments as follows: medetomidine 20 μg kg(-1) and butorphanol tartrate 0.1 mg kg(-1) IV and IM (MB), and MB combined with MK-467,500 μg kg(-1) (MBMK) IV and IM. Heart rate (HR), arterial blood pressures (SAP, MAP, DAP), central venous pressure (CVP), cardiac output, respiratory rate (fR ), rectal temperature (RT) were measured and arterial blood samples were obtained for gas analysis at baseline and at 3, 10, 20, 30, 45 and 60 minutes after drug administration. The cardiac index (CI), systemic vascular resistance index (SVRI) and oxygen delivery index (DO2 I) were calculated. After the follow-up period atipamezole 50 μg kg(-1) IM was given to reverse sedation.HR, CI and DO2 I were significantly higher with MBMK after both IV and IM administration. Similarly, SAP, MAP, DAP, CVP, SVRI and RT were significantly lower after MBMK than with MB. There were no differences in fR between treatments, but arterial partial pressure of oxygen decreased transiently after all treatments. Recoveries were uneventful following atipamezole administration after all treatments.MK-467 attenuated the cardiovascular effects of a medetomidine-butorphanol combination after IV and IM administration.
- Alfaxalone or ketamine-medetomidine in cats undergoing ovariohysterectomy: a comparison of intra-operative parameters and post-operative pain. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2014 Mar 28.
To compare post-operative pain in cats after alfaxalone or ketamine- medetomidine anaesthesia for ovariohysterectomy (OHE) and physiologic parameters during and after surgery.Prospective 'blinded' randomized clinical study.Twenty-one healthy cats.Cats were assigned randomly into two groups: Group A, anaesthesia was induced and maintained with alfaxalone [5 mg kg(-1) intravenously (IV) followed by boli (2 mg kg(-1) IV); Group MK, induction with ketamine (5 mg kg(-1) IV) after medetomidine (30 μg kg(-1) intramuscularly (IM)], and maintenance with ketamine (2 mg kg(-1) IV). Meloxicam (0.2 mg kg(-1) IV) was administered after surgery. Basic physiological data were collected. At time T = -2, 0, 0.5, 1, 2, 4, 6, 8, 12, 16, 20, and 24 hours post-operatively pain was assessed by three methods, a composite pain scale (CPS; 0-24 points), a visual analogue scale (VAS 0-100 mm), and a mechanical wound threshold (MWT) device. Butorphanol (0.2 mg kg(-1) IM) was administered if CPS was scored ≥13. Data were analyzed using a general linear model, Kruskal-Wallis analyses, Bonferroni-Dunn test, unpaired t-test and Fisher's exact test as relevant. Significance was set at p < 0.05.VASs were significantly higher at 0.5, 1, 2, 4, and 20 hours in group A; MWT values were significantly higher at 8 and 12 hours in group MK. Post-operative MWT decreased significantly compared to baseline in both groups. There was no difference in CPS at any time point. Five cats required rescue analgesia (four in A; one in MK).Anaesthesia with ketamine-medetomidine was found to provide better post-surgical analgesia than alfaxalone in cats undergoing OHE; however, primary hyperalgesia developed in both groups. Alfaxalone is suitable for induction and maintenance of anaesthesia in cats undergoing OHE, but administration of additional sedative and analgesic drugs is highly recommended.