Effects of acepromazine on pulmonary gas exchange and circulation during sedation and dissociative anaesthesia in horses

OBJECTIVE: To study pulmonary gas exchange and cardiovascular responses to sedation achieved with romifidine and butorphanol (RB) alone, or combined with acepromazine, and during subsequent tiletamine-zolazepam anaesthesia in horses. ANIMALS: Six (four males and two females) healthy Standardbred trotters aged 3-12 years; mass 423-520 kg. STUDY DESIGN: Randomized, cross-over, experimental study. MATERIALS AND METHODS: Horses were anaesthetized on two occasions (with a minimum interval of 1 week) with intravenous (IV) tiletamine-zolazepam (Z; 1.4 mg kg(-1)) after pre-anaesthetic medication with IV romifidine (R; 0.1 mg kg(-1)) and butorphanol (B; 25 microg kg(-1) IV). At the first trial, horses were randomly allocated to receive (protocol ARBZ) or not to receive (protocol RBZ) acepromazine (A; 35 microg kg(-1)) intramuscularly (IM) 35 minutes before induction of anaesthesia. Each horse was placed in left lateral recumbency and, after tracheal intubation, allowed to breathe room air spontaneously. Respiratory and haemodynamic variables and ventilation-perfusion (; multiple inert gas elimination technique) ratios were determined in the conscious horse, after sedation and during anaesthesia. One- and two-way repeated-measures anova were used to identify within- and between-technique differences, respectively. RESULTS: During sedation with RB, arterial oxygen tension (PaO(2)) decreased compared to baseline and increased mismatch was evident; there was no O(2) diffusion limitation or increase in intrapulmonary shunt fraction identified. With ARB, PaO(2) and remained unaffected. During anaesthesia, intrapulmonary shunt occurred to the same extent in both protocols, and mismatching increased. This was less in the ARBZ group. Arterial O(2) tension decreased in both protocols, but was lower at 25 and 35 minutes of anaesthesia in RBZ than in ARBZ. During sedation, heart rate (HR) and cardiac output (Qt) were lower while arterial-mixed venous oxygen content differences and haemoglobin concentrations were higher in RBZ compared with ARBZ. Total systemic vascular resistance, mean systemic, and mean pulmonary arterial pressures were higher during anaesthesia with RBZ compared to ARBZ. CONCLUSIONS AND CLINICAL RELEVANCE: Acepromazine added to RB generally improved haemodynamic variables and arterial oxygenation during sedation and anaesthesia. Arterial oxygenation was impaired as a result of increased shunt and mismatch during anaesthesia, although acepromazine treatment reduced disturbances and falls in PaO(2) to some extent. Haemodynamic variables were closer to baseline during sedation and anaesthesia when horses received acepromazine. Acepromazine may confer advantages in healthy normovolaemic horses.     

The Effects of the Method of Calculation on the Evaluation of the Pharmacokinetic Parameters of Oxytetracycline After Intravenous Administration to Calves

Errecalde, J.O., Mestorino, N. and Mariño, E.L., 1997. The effects of the method of calculation on the evaluation of the pharmacokinetic parameters of oxytetracycline after intravenous administration to calves. Veterinary Research Communications, 21 (4), 273-281The aim of this study was to assess the differences in the values of the pharmacokinetic parameters attributable to the use of either linear or nonlinear regression analysis and to find the effect of weighting schemes on these differences. Six calves received 20 mg/kg oxytetracycline i.v. Blood samples were drawn during 72 h. The assay of the drug was performed microbiologically. A bicompartmental pharmacokinetic model was used, kinetic analysis being carried out by linear regression (LR) and by weighted least-squares nonlinear regression (WLSNLR). Statistical analysis included a test for normality, the Kruskall-Wallis test and ANOVA with log transformation.The A0, and B0 did not show any statistically significant differences attributable to the mathematical method used. On the other hand, the statistically significant differences in the values found using the Kruskall-Wallis test and ANOVA with log transformation could be attributed to the different methods employed. ANOVA with log transformation determined statistically significant differences between the parameters obtained by linear analysis and those obtained by WLSNLR when the weighting (w) was 1. When weights were 1/x, 1/x2 or 1/ x, no statistically significant differences were found. The optimal weighting scheme was w = 1/x2 because of a more homogeneous scatter and random distribution of residuals about the abcissa axis in a plot of weighted residuals in the ordinate versus time in the abcissa. It was concluded that the use of these different procedures can give major variations in the apparent value of , the most important pharmacokinetic parameter. The correct selection of the weighting procedure is therefore fundamental in obtaining the best estimate of this pharmacokinetic parameter in WLSNLR.     

Pharmacokinetics of tapentadol in laying hens and its residues in eggs after multiple oral dose administration

1. The aim of the study was to evaluate the pharmacokinetics (PKs) of tapentadol (TAP), a novel opioid analgesic, in laying hens after intravenous (IV) and oral (PO) administration and to quantify the concentrations of TAP residues in eggs.

2. Twenty healthy laying hens were divided into three groups: A (n = 6), B (n = 6) and C (n = 8). The study was conducted in two phases. Groups A and B received TAP by IV and PO routes at the dose of 1 and 5 mg/kg, respectively.

3. No visible adverse effects were observed after administration of the drug. TAP plasma concentrations were detectable up to 4 h following administration. Following IV administration, TAP plasma concentrations were only higher than the minimal effective concentration (148 ng/ml) reported for humans for 1 h. After single PO administration, plasma concentrations of TAP would not conform to software algorithms and the PK parameters were not calculated. TAP concentration following multiple PO doses at 5 mg/kg for 5 d was found to be higher and more persistent (12 h vs. 7 h) in yolk compared with albumen.

4. This is the first PK study on the novel atypical opioid TAP in laying hens. Further studies are required to investigate the analgesic efficacy and actual effective plasma concentration of TAP in this species.     

A controlled randomized clinical trial to assess postoperative analgesia after thiopental–isoflurane anaesthesia or total intravenous anaesthesia with alfaxalone in dogs

Alfaxalone, a synthetic neuroactive steroid, has been attributed with properties including sedation, anaesthesia and analgesia. The clinical relevance of any analgesic properties of alfaxalone has not been demonstrated. This study was a prospective, blinded, randomized, negative control clinical trial in 65 healthy dogs presented for ovariohysterectomy. Anaesthesia was induced and maintained, for Group 1 (TIVA) dogs (n = 30) with intravenous alfaxalone alone and for Group 2 dogs (n = 35) with thiopental followed by isoflurane in 100% oxygen inhalation. After ovariohysterectomy, quantitative measures of pain or nociception were recorded at 15 min intervals for 4 hr using three independent scoring systems, a composite measure pain scale (CMPS), von Frey threshold testing and measures of fentanyl rescue analgesia. The mean CMPS scores of Group 2 (THIO/ISO) dogs remained higher than Group 1 (TIVA) dogs from 15 to 135 min post‐surgery but this difference was not statistically significant. There were no significant differences between groups in the proportions of dogs requiring rescue fentanyl analgesia, the total fentanyl dose used or the time to first fentanyl dose. The Von Frey threshold testing was found to be unsuitable for measurement of pain in this experimental model. When administered as total intravenous anaesthesia, alfaxalone did not provide analgesia in the postoperative period.     

速眠新麻醉剂在山羊胚胎移植手术中的应用

【目的】筛选适合于山羊胚胎移植的速眠新静脉注射麻醉剂量。【方法】以关中奶山羊为试验动物,速眠新Ⅱ注射液为麻醉剂,研究静脉注射麻醉时,不同剂量速眠新Ⅱ注射液对不同体重组(28~35,36~45和46~55kg)山羊的麻醉效果;同时比较了速眠新Ⅱ注射液2种麻醉方法(静脉注射和肌肉注射)对山羊生理指标,心电图,麻醉山羊的诱导期、麻醉期、苏醒期,麻醉苏醒后山羊的采食、反刍及精神状况的影响。【结果】(1)山羊胚胎移植受体静脉麻醉时,山羊体重为28~35,36~45及46~55 kg时,最适宜麻醉剂量分别为0.4,0.4和0.5 mL/只。(2)与麻醉前相比,麻醉后山羊的体温升高,呼吸次数和心率均降低。(3)2种麻醉方法下,麻醉效果优、良山羊的心电图均正常,无差异。(4)速眠新Ⅱ注射液静脉注射麻醉时,山羊的诱导期、麻醉期和苏醒期均较短,在苏醒后0.5 h,92.8%和87.5%的山羊可以采食和反刍,95.3%的山羊精神状况良好;苏醒后1 h基本上全部可以恢复正常。【结论】采用静脉注射麻醉山羊进行胚胎移植手术,速眠新Ⅱ注射液用药剂量小,且安全、有效,明显优于肌肉注射。     

Bispectral index in dogs at three intravenous infusion rates of propofol

ObjectiveTo establish the correlation between the bispectral index (BIS) and different rates of infusion of propofol in dogs.Study designProspective experimental trial.AnimalsEight adult dogs weighing 6–20 kg.MethodsEight animals underwent three treatments at intervals of 20 days. Propofol was used for induction of anesthesia (10 mg kg⁻¹ IV), followed by a continuous rate infusion (CRI) at 0.2 mg kg⁻¹ minute⁻¹ (P2), 0.4 mg kg⁻¹ minute⁻¹ (P4) or 0.8 mg kg⁻¹ minute⁻¹ (P8) for 55 minutes. The BIS values were measured at 10, 20, 30, 40, and 50 minutes (T10, T20, T30, T40, and T50, respectively) after the CRI of propofol was started. Numeric data were submitted to analysis of variance followed by Tukey test (p < 0.05).ResultsThe BIS differed significantly among groups at T40, when P8 was lower than P2 and P4. At T50, P8 was lower than P2. The electromyographic activity (EMG) in P2 and P4 was higher than P8 at T40 and T50.ConclusionsAn increase in propofol infusion rates decreases the BIS values and EMG.     

The effects of propofol, isoflurane and sevoflurane on vecuronium infusion rates for surgical muscle relaxation in dogs

OBJECTIVE: To compare the constant rate infusion (CRI) of vecuronium required to maintain a level of neuromuscular blockade adequate for major surgeries, e.g. thoracotomy or laparotomy, in dogs anaesthetized with a CRI of fentanyl and either propofol, isoflurane or sevoflurane. STUDY DESIGN: Prospective, randomized, cross-over study. ANIMALS: Thirteen male beagles (age, 9-22 months; body mass 6.3-11.3 kg). MATERIALS AND METHODS: Dogs were anaesthetized with propofol (24 mg kg(-1) hour(-1) IV CRI; group P), isoflurane (1.3% end-tidal concentration; group I) or sevoflurane (2.3% end-tidal concentration; group S) with fentanyl (5 microg kg(-1) hour(-1) IV, CRI). Sixty to seventy minutes after induction of anaesthesia, vecuronium was administered at a rate of 0.4, 0.3 and 0.2 mg kg(-1) hour(-1) in groups P, I and S respectively. To determine the degree of neuromuscular block, a peripheral nerve was stimulated electrically using the train-of-four (TO4) stimulus pattern. Evoked muscle contractions were evaluated using a neuromuscular monitoring device. Once the TO4 ratio reached 0, the continuous infusion rate was decreased and adjusted to maintain a TO4 count of 1. Continuous infusion was continued for 2 hours. The infusion rate of vecuronium was recorded 20, 40, 60, 80, 100 and 120 minutes after the start of infusion. RESULTS: The mean continuous infusion rates of vecuronium during stable infusion were 0.22 +/- 0.04 (mean +/- SD), 0.10 +/- 0.02 and 0.09 +/- 0.02 mg kg(-1) hour(-1) in groups P, I and S respectively. There were statistically significant differences between the rates in groups P and I and between the rates in groups P and S. Conclusions and clinical relevance In healthy dogs, the recommended maintenance infusion rate of vecuronium is 0.2 mg kg(-1) hour(-1) under CRI propofol-fentanyl anaesthesia and 0.1 mg kg(-1) hour(-1) during CRI fentanyl-isoflurane or sevoflurane anaesthesia.     

Fragmentation of intravenous catheters in three horses

Fragmentation of an intravenous, polytetrafluoroethylene catheter occurred in three horses. The retained fragment was identified in the cervical region by radiography and in the jugular vein by ultrasonography. The retained fragment was removed successfully by jugular venotomy.     

Attitudes of Spanish-speaking veterinarians interested in anaesthesia towards use of total intravenous anaesthesia in dogs: a survey study

ObjectivesTo describe Spanish-speaking veterinary anaesthetists’ attitudes towards use of total intravenous anaesthesia (TIVA) in dogs.Study designProspective online voluntary survey.PopulationData from 300 answered surveys.MethodsAn anonymous questionnaire was sent via e-mail to representatives of the four largest Spanish-speaking veterinary anaesthesia and analgesia associations. It was distributed through mailing lists (Spain, Argentina, Mexico) or social media (Spain, Chile) to gather information on the use, opinions and perceived advantages of TIVA, as well as on preferred alternatives to isoflurane for providing general anaesthesia. Logistic regression was used to test for response associations.ResultsA total of 275 (92%) respondents had used TIVA (24% rarely, 36% sometimes, 40% very often or always). There was an association between a higher rate of TIVA usage and a low specialization level, less clinical experience and unavailability of anaesthetic gas scavenging systems. The main reasons for not using TIVA were lack of familiarity with the technique (92%), unavailability of infusion pumps (32%), established institutional anaesthetic protocol (32%), and technical difficulty (20%). Among frequent TIVA users, a higher proportion reported the greater ease of TIVA use (52%) compared to those that did not perceive such benefit (17%) [odds ratio (OR) = 5.2; 95% confidence interval (CI95), 1.7–16.6; p = 0.004). More respondents did not consider TIVA more expensive (60%) (OR = 2.1; CI95, 1.0–4.3; p = 0.034), more difficult to perform (59%) (OR = 2.5; CI95, 1.3–4.9; p = 0.006) or to manage the equipment (53%) (OR = 3.3; CI95, 1.4–7.8; p = 0.008), than inhalational anaesthetics. During isoflurane shortages, respondents reportedly preferred using an alternative inhalational agent (59%) rather than TIVA (47%).Conclusions and clinical relevanceTIVA use is widespread among veterinarians within the surveyed associations. Frequent TIVA users reported greater perceived advantages. In situations of isoflurane shortage, an alternative inhalational anaesthetic was preferred over TIVA.