Sedation levels in dogs: a validation study

Pharmacokinetics and pharmacodynamics of intravenous dexmedetomidine (2 μg∙kg-1) in dogs

This study assessed the pharmacokinetics and pharmacodynamics of low-dose dexmedetomidine after IV bolus in dogs. Six healthy adult dogs (6.8 ± 3.0 kg) received dexmedetomidine (2 μg.kg-1 IV) over 2 min, using an infusion pump. Blood samples were collected totaling 5 h of monitoring. A validated UHPLC-MS/MS method was used to determine the plasma concentration of dexemedetomidine. For pharmacodynamics, HR, RR, oscillometric MBP, Grint END sedation score were evaluated at baseline (T0), every 3 min (T3 to T21), and after 30 (T30) and 60 (T60) minutes, with p < 0.05. T1/2 was 28.28 ± 6.14 min; the area under the curve was 467.44 ± 60.42 ng/mL/min. The total clearance was 5.46 ± 0.41 mL/min/kg, the Vdss was 146.19 ± 21.04 mL/kg, and the C max was 3.13 ± 1.15 ng/mL. HR (bpm) decreased significantly from T6 (79 ± 21) to T21 (78 ± 31) compared to T0 (116 ± 28). RR(mpm) decreased from T3 (43 ± 44) to T60 (41 ± 23), with T0 being 70 ± 48. The MBP (mmHg) increased at T18 (151 ± 34), T21 (152 ± 35), and T30 (140 ± 27), compared to T0 (111 ± 22). Sedation occurred at all times post-bolus, with a maximum peak at T12 (END 8 ± 6). The low dose of dexmedetomidine provided sedation in all animals, characterizing rapid metabolization and elimination. However, cardiovascular effects still may have negative repercussions in dogs with hemodynamic comorbidities, highlighting the caution and individualization of its use in certain patients.

Pharmacokinetics of a continuous intravenous infusion of hydromorphone in healthy dogs

Introduction

Dosing recommendations for hydromorphone intravenous constant rate infusion (IV CRI) are derived from simulations following IV bolus administration. While this extrapolated dose regimen has been described clinically, pharmacokinetics (PK) of hydromorphone infusions in dogs are not yet described. The study objective was to describe the PK of hydromorphone in healthy dogs receiving an IV bolus followed by an IV CRI for 48 h.

Methods

A prospective, experimental study was performed involving the administration of hydromorphone (0.1 mg/kg IV bolus then IV CRI 0.01 mg/kg/h over a 48 h period) to 6 healthy Beagle dogs. Blood samples were collected at 16 time points between 0 and 58 h relative to the initial bolus. Plasma hydromorphone concentrations were analyzed by high pressure liquid chromatography with tandem mass spectrometry detection. Pharmacokinetic parameter estimates were obtained with compartmental methods using commercially available software.

Results

A two-compartment model with first order elimination was used. At the end of the infusion, median (range) plasma hydromorphone concentrations were 6.8 (5.5-19.6) ng/mL. The median total body clearance was 30.4 (19.8-36.7) mL/min/kg; volume of distribution at steady state was 4.5 (3.2-7.8) L/kg; and terminal elimination half-life was 11.2 (7.6-24.3) h.

Conclusion

Hydromorphone (0.1 mg/kg IV bolus then IV CRI of 0.01 mg/kg/h) maintained steady-state plasma concentrations above the minimum human analgesic target in healthy Beagle dogs with minimal side effects. Further studies are needed to determine the effective plasma concentrations of hydromorphone in painful dogs.

Full spectrum cannabidiol-rich extract reduced propofol dosage required for anesthetic induction in dogs-a pilot study

Introduction

Cannabinoids show great therapeutic potential, but their effect on anesthesia still remains unclear. Use of chronic recreational Cannabis in humans undergoing anesthetic procedures tends to require a higher dose when compared to non-users. On the other hand, studies on rodents and dogs have shown that cannabinoid agonists may potentiate certain anesthetics. This contrast of effects possibly occurs due to different time lengths of administration of different phytocannabinoids at different doses, and their distinct effects on the Endocannabinoid System, which is also affected by anesthetics such as propofol and isoflurane.

Methods

Twenty-seven healthy male dogs, client-owned, ranging from 1 to 7 years, and from 5 to 35 kg were selected, mean weight 15.03±7.39 kg, with owners volunteering their animals to participate in the research performed in the Federal University of Santa Catarina (UFSC). Dogs were randomized into 3 groups. The Control Group (CON, n = 9), receiving only Extra Virgin Olive Oil, the same oil-base used in the treatment groups. Group 2 (G2, n = 9) received 2 mg/kg of total phytocannabinoids, and Group 3 (G3, n = 9) received 6 mg/kg of total phytocannabinoids. All groups received their treatments transmucosally, 75 min before their induction with propofol. Heart and respiratory rate, blood pressure, temperature and sedation were evaluated prior to, and at 30, 60, and 75  min after administration of the fsCBD-rich extract or Placebo extract. Preanesthetic medication protocol was also included across all treatment groups, 15  min before induction. Parametric data was analyzed with one-way ANOVA, followed by Student-Newman-Keuls (SNK) if significant statistical differences were found. Non-parametric data was analyzed using Friedman's test, followed by Dunn test for comparisons between all timepoints in the same group. Kruskal-Wallis followed by Dunn was utilized for between groups comparisons. Propofol dose necessary for induction was analyzed through One-way ANOVA followed by Tukey's Multiple Comparisons Test, using Instat by Graphpad, and differences were considered statistically significant when p < 0.05. Our analysis assessed if statistical significance was present between time points in the same group, and between groups in the same time points.

Results

In our study, 6  mg/kg of total phytocannabinoids were able to reduce the dose of propofol necessary for induction by 23% when compared to the control group. The fsCBD-rich extract did not produce significant sedation within or between groups, although statistically significant differences in heart rate and systolic blood pressure were found.

Discussion

Our findings indicate that phytocannabinoids could be an adjunct option in anesthesia, although further research is necessary to better confirm this data. Additionally, further research is needed to determine the best dosage, delivery method, time for administration, ideal molecular profile for desired effects, safety, drug-drug interactions, and transurgical effects.

Comparison of sedation with dexmedetomidine administered subcutaneously at 2 different locations on the head in dogs

Objective

This study aimed to compare the sedative effects of dexmedetomidine administered to dogs subcutaneously (SC) at the Governing Vessel 20 (GV20) acupuncture point and at another point on the head.

Animals and procedure

Ten client-owned dogs were included. Dogs were sedated 2 times, 14 d apart, with 200 μg/m2 of dexmedetomidine, SC, at GV20 and at a point at the base of the ear (SC-head). The sedation was assessed with a sedation scale and a Dynamic and Interactive Visual Analogue Scale (DIVAS). The ease of performing radiographic studies, physiological parameters, and adverse events were recorded. Statistical linear mixed-effect models (ANOVA) were applied. Statistical significance was set at P < 0.05.

Results

The time to sedation and sedation scores were similar for both groups. The level of sedation achieved was adequate to perform orthopedic radiographs for 9/10 (90%) cases in the GV20 group and 8/10 (80%) cases in the SC-head group. Heart and respiratory rates decreased significantly over time in both groups (P < 0.001). Adverse events were infrequent and self-limiting.

Conclusion

Our study provides evidence that SC administration of dexmedetomidine on the head, at the GV20 point or at the base of the ear, is easy and provides a sufficient level of sedation to obtain orthopedic radiographs in dogs.

Clinical evaluation of the sedative, antinociceptive and cardiorespiratory effects of intranasal dexmedetomidine combined with methadone in healthy dogs

In this prospective, randomised, blinded clinical study, we compared the sedative, antinociceptive and cardiorespiratory effects of intranasal (IN) dexmedetomidine at 5 μg/kg (diluted with 0.03 mL/kg NaCl 0.9%, DEX) with or without methadone (0.3 mg/kg; DEXMET), through a mucosal atomization device to one nostril in twenty healthy client-owned dogs. At 5-min intervals over 45 min, sedation score, onset, cardiopulmonary variables, mechanical nociceptive thresholds (MNTs) were assessed, also ease of administration, adverse effects, and response to IV catheterization. Statistical analysis employed t-test, the Mann-Whitney U, repeated measures ANOVA and Chi-square tests as appropriate (P < 0.05). Higher sedation ocurred in DEXMET (7 [5-10]) compared to DEX (5 [2-7]) from 15 to 30 min (P < 0.01, median [interquartile range]). Heart rate was lower in DEXMET (P < 0.01; 65% reduction vs. 41% in DEX, P = 0.001). The MNTs were higher in DEXMET than DEX from 15 to 45 min (P < 0.01), peaking at T30 (17.1 ± 3.8, DEXMET and 8.5 ± 5.4 N, DEX). No differences were observed in mean arterial blood pressure and respiratory rate. Intranasal administration was considered easy for 8 dogs per group. Reverse sneezing (8 dogs; P < 0.001), sialorrhea and retching (4 and 2 dogs, respectively) occurred in DEXMET. Response to catheterisation was lower in DEXMET than DEX (P = 0.039; 2 and 7 dogs, respectively). In conclusion, intranasal methadone (0.3 mg/kg) increased the sedative and antinociceptive effects produced by dexmedetomidine (5 μg/kg) in healthy dogs and resulted in lower heart rate.

Comparison of a blind and an ultrasound-guided technique for Retrobulbar anesthesia in dogs undergoing unilateral subconjunctival enucleation

OBJECTIVE

This study compared the quality of retrobulbar anesthesia using a blind inferior-temporal palpebral approach (ITP) with an ultrasound-guided supratemporal (ST) technique in dogs undergoing unilateral enucleation.

ANIMAL STUDIED

Twenty-one client-owned dogs were undergoing enucleation.

PROCEDURES

Dogs were randomly assigned to receive ITP (n = 10) or ST (n = 11) with 0.5% ropivacaine at 0.1 mL/cm of neurocranial length. The anesthetist was blinded to the technique. Intraoperative data included cardiopulmonary variables, inhalant anesthetics requirement, and requirement for rescue analgesia (intravenous fentanyl 2.5 mcg/kg). Postoperative data included pain scores, sedation scores, and need for intravenous hydromorphone (0.05 mg/kg). Treatments were compared using Wilcoxon's rank sum test or Fisher's exact test as appropriate. Comparison of variables over time were tested using a mixed effect linear model on rank. Significance was set at p = 0.05.

RESULTS

Intraoperative cardiopulmonary variables and inhalant requirements were not different between groups. Dogs receiving ITP required median (interquartile range, IQR) 1.25 (0, 2.5) mcg/kg intraoperative fentanyl while those receiving ST required none (p < 0.01). Intraoperative fentanyl was required in 5/10 and 0/11 of dogs in the ITP and ST groups, respectively (p = 0.01). Postoperative analgesia requirements were not significantly different between groups; 2/10 and 1/10 dogs in the ITP and ST groups, respectively. Sedation score negatively affected pain score (p < 0.01).

CONCLUSIONS

The ultrasound-guided ST technique was more effective at decreasing intraoperative opioid requirements than the blind ITP approach in dogs undergoing unilateral enucleation.

Evaluation of the use of intranasal atipamezole to reverse the sedative effects of xylazine in dogs

OBJECTIVE

To assess the ability of intranasal atipamezole to reverse sedative effects of xylazine in dogs.

DESIGN

Prospective proof-of-concept study.

SETTING

University research laboratory.

ANIMAL

Six healthy, staff-owned dogs.

INTERVENTIONS

Dogs were sedated with 1.1 mg/kg of xylazine intravenously. The sedation score of each dog was recorded every 5 minutes until they achieved a sedation score of >13/21 for 3 readings. Once achieved, 0.3 mg/kg of atipamezole was administered intranasally using a mucosal atomization device. Sedation scores continued to be recorded every 5 minutes until successful reversal was achieved (<4/21).

MEASUREMENTS AND MAIN RESULTS

Average times to standing and normal wakefulness after administration of intranasal atipamezole were 6 minutes, 30 seconds and 7 minutes, 20 seconds, respectively.

CONCLUSIONS

Intranasal atipamezole successfully reversed the sedation effects of xylazine. The findings of this study provide justification for future controlled prospective studies into the potential use of intranasal atipamezole in a variety of settings including exposure to xylazine in operational canines as well as bioavailability studies for optimal dosing.

A dose characterization study evaluating the pharmacodynamics and safety of a concentrated alfaxalone solution (4%) as an intramuscular sedative in dogs

Alfaxalone is a commonly employed veterinary anaesthetic induction and sedation agent. A 4% w/v preserved, aqueous formulation of alfaxalone 'RD0387' (A4%) has recently been developed. To evaluate the sedative effects of A4%, three doses, 5 mg kg-1 (A5); 7.5 mg kg-1 (A7.5) and 10 mg kg-1 (A10) were administered intramuscularly into the epaxial musculature of six healthy adult mixed-breed dogs in an experimental, randomized, blinded, crossover study. Sedation time variables, quality of sedation (including onset of sedation and recovery), physiological variables, response to cephalic vein catheterization and frequency of undesirable events were recorded. Continuous variables were analysed between treatments (one-way ANOVA or restricted maximum likelihood modelling) and within treatments compared with baseline (Tukey's test). Categorical data were analysed between treatments (Kruskal-Wallis' test) and within treatments from baseline (Dunn's test). Significance was set at p < .05. All dogs became sedated (laterally recumbent) and sedation onset was significantly faster in groups A7.5 (9.8 ± 5.3 min) and A10 (9.1 ± 5.6 min) compared to A5 (25.6 ± 16.1 min) (p = .033, p = .027, respectively). Duration of sedation was significantly longer in A10 (168.5 ± 70.6 min) and A7.5 (143.8 ± 58 min) compared to A5 (63.8 ± 28.2 min) (p = .005 and p = .003, respectively). Dogs in A10 had a superior quality of onset of sedation compared to A5 (p = .028). Sedation scores and quality of recovery from sedation were not significantly different between doses. Two dogs (2/6) in A5 were insufficiently sedated for cephalic catheterization. Ataxia was the most frequently observed undesirable event with an overall frequency of 78% (14/18) and 89% (16/18) during sedation onset and recovery, respectively. Overall, A4% administered IM in dogs at 7.5 and 10 mg kg-1 resulted in sufficient sedation for IV catheterization in dogs. To improve the speed and quality of the sedation, it is recommended that future research focuses on combining A4% with other sedative or analgesic drugs.

Comparison of sedation with dexmedetomidine/atipamezole administered subcutaneously at GV20 acupuncture point with usual routes of administration in dogs presented for orthopaedic radiographs

OBJECTIVES

To evaluate the efficacy of subcutaneous administration of dexmedetomidine/atipamezole at the Governing Vessel 20 (GV20) acupuncture point compared with other administration routes (intramuscular and intravenous) in dogs presented for orthopaedic radiographs.

MATERIALS AND METHODS

Prospective, randomised, blinded, controlled clinical study. Sixty-four client-owned dogs were randomly injected with 200 μg/m2 of dexmedetomidine intramuscular (lumbar muscles) (n=20), intravenous (n=23) or subcutaneous at the GV20 point (n=21). Following radiographs, dogs received 2000 μg/m2 of atipamezole intramuscular (n=31), or subcutaneous at the GV20 point (n=27). Degree and time to sedation and recovery were assessed using a sedation scale and a Dynamic and Interactive Visual Analog Scale (DIVAS). Clinical physiological variables and adverse events were used. Statistical linear mixed-effect models (analysis of variance) and Cox models were performed. Significance was set at P-value <0.05.

RESULTS

Sedation was insufficient to perform orthopaedic radiographs in six dogs in the intramuscular group. The time to sedation was significantly longer, and sedation scale and DIVAS scores were significantly lower in the intramuscular group. The intravenous group had significantly higher sedation scale and DIVAS scores than the GV20 group. No significant differences were observed between the intramuscular and GV20 recovery groups, although the time effect was significantly more pronounced in the GV20 recovery group.

CLINICAL SIGNIFICANCE

Subcutaneous administration of dexmedetomidine and atipamezole at GV20 provided effective sedation and recovery in dogs undergoing orthopaedic radiographic studies. GV20 administration provided a clinically similar level of sedation to the intravenous route, and greater and faster sedation and similar recovery to intramuscular.

Alfaxalone provides reliable sedation for intradermal allergen testing in dogs and does not significantly affect results when compared to dexmedetomidine

BACKGROUND

Dexmedetomidine (Dexmedetomidine hydrochloride-Dexdomitor; Zoetis) is the preferred sedative used for canine intradermal allergen testing (IDT) in the United States. Alfaxalone (Alfaxan Multidose; Jurox Animal Health) is a neuroactive steroid, and its effect on sedation and allergen reactivity scores is unknown.

HYPOTHESIS/OBJECTIVES

We hypothesised that alfaxalone would produce an adequate level of sedation with fewer cardiovascular adverse effects and would not affect allergen reactivity scores or histamine wheal size compared to dexmedetomidine.

MATERIALS AND METHODS

Twenty client-owned dogs were included in two groups: 10 atopic and 10 nonatopic. In a randomised, controlled, blinded, cross-over design all dogs underwent two modified IDT, 1-4 weeks apart, using intravenous dexmedetomidine (2.87-5.22 μg/kg) or alfaxalone (1.8-2.4 mg/kg). Anaesthetic parameters and sedation level were recorded over 25 min using a validated canine sedation scale described by Grint et al. (Small Anim Pract, 2009, 50, 62). Simultaneously, both objective and subjective reactivity scores were measured in technical triplicates at 10, 15 and 20 min. The modified IDT included eight allergens, histamine-positive and saline-negative controls.

RESULTS

Alfaxalone produced a significantly higher sedation score across all time points (p < 0.05). All objective scores were significantly correlated to the corresponding subjective scores (Spearman R = 0.859, p < 0.0001). Sedative used did not significantly affect subjective allergen scores for nine atopic dogs (p > 0.05, 15 min). Sedative used did not affect the diameter of objective scores for individual allergens and histamine wheals (p > 0.05, 15 min).

CONCLUSIONS AND CLINICAL RELEVANCE

Intravascular alfaxalone is an alternative sedative for IDT in dogs. Alfaxalone may be preferred to dexmedetomidine in some clinical scenarios as a result of having fewer cardiovascular adverse effects.

Nursing strategies for the mechanically ventilated patient

The goal of this manuscript is to provide a comprehensive and multi-disciplinary review of the best nursing practices of caring for mechanically ventilated patients. By reviewing human medicine literature, the authors will extrapolate procedures that have been found to be most effective in reducing the risk of mechanical ventilation (MV) complications. Paired with review of the current standards in veterinary medicine, the authors will compile the best practice information on mechanically ventilated patient care, which will serve as a detailed resource for the veterinary nursing staff. Written from a nursing standpoint, this manuscript aims to consolidate the nursing assessment of a mechanically ventilated patient, addressing both systemic and physical changes that may be encountered during hospitalization. The goal of this review article is to present information that encourages a proactive approach to nursing care by focusing on understanding the effects of polypharmacy, hemodynamic changes associated with MV, complications of recumbent patient care, and sources of hospital acquired infections. When applied in conjunction with the more technical aspects of MV, this manuscript will allow veterinary technicians involved in these cases to understand the dynamic challenges that mechanically ventilated patients present, provide guidance to mitigate risk, address issues quickly and effectively, and create an up-to date standard of practice that can be implemented.

Cardiorespiratory Effects and Desflurane Requirement in Dogs Undergoing Ovariectomy after Administration Maropitant or Methadone

General anesthesia for ovariectomy in dogs is based on a balanced anesthesia protocol such as using analgesics along with an inhalant agent. While opioids such as fentanyl and methadone are commonly used for their analgesic potency, other drugs can also have analgesic effects. Maropitant, an antiemetic for dogs and cats, has also been shown to exert analgesic effects, especially on visceral pain. The aim of this study was to compare the cardiorespiratory effects and analgesic properties of maropitant and methadone combined with desflurane in dogs undergoing ovariectomy. Two groups of 20 healthy mixed-breeds bitches undergoing elective ovariectomy received intravenous either maropitant at antiemetic dose of 1 mg kg^-1 or methadone at the dose of 0.3 mg kg^-1. Cardiorespiratory variables were collected before premedication, 10 min after sedation and during surgery. Recovery quality and postoperative pain were evaluated 15, 30, 60, 120, 240 and 360 min postoperatively. Results showed that maropitant produced analgesia and reduced the requirement of desflurane in amounts similar to those determined by methadone (5.39 ± 0.20% and 4.91 ± 0.26%, respectively) without significant difference, while maintaining heart rate, arterial blood pressure, respiratory rate and carbon dioxide end-tidal partial pressure even at a more satisfactory level. Therefore, maropitant may be recommended as an analgesic drug for abdominal surgery not only in healthy dogs but also in those with reduced cardiorespiratory compensatory capacities or at risk of hypotension, especially when combined with a sedative such as dexmedetomidine.

Effect of Classical Music on Depth of Sedation and Induction Propofol Requirements in Dogs

The main objective of this prospective, randomized, blind, cross-over experimental study was to evaluate the effect of classical music on the depth of sedation and propofol requirements for the induction of anaesthesia in dogs. Twenty dogs were involved, and each was subjected to three different treatments with a 3-month gap: Chopin music, Mozart music, and no music, via loudspeakers. The dogs were premedicated with acepromazine and butorphanol by intramuscular injection, and anaesthesia was induced using propofol intravenously. To compare the depth of sedation and propofol requirements for the induction of anaesthesia among the different treatments, we utilized non-parametric tests (Kruskal-Wallis test) for the depth of sedation due to a slight deviation from the normal distribution and parametric (ANOVA) for propofol requirements. When exposed to music (Chopin or Mozart), dogs exhibited deeper sedation and required less propofol for their intubation compared to the no-music treatment (p < 0.05). Exposure to classical music had a positive impact on the level of sedation, and more profound central nervous system depression seemed to contribute to approximately 20% lower propofol dose requirements for tracheal intubation. Therefore, classical music during the preoperative period appeared to exert a beneficial effect, at least when applying the specific pre-anaesthetic medications used in the present study.

Evaluation of the Analgesic Efficacy of Undiluted Intraperitoneal and Incisional Ropivacaine for Postoperative Analgesia in Dogs after Major Abdominal Surgery

Recommendations for intraperitoneal (IP) and incisional (INC) administration of local anaesthetics after visceral surgery exist, but evidence is scarce. This prospective, randomized, blinded, controlled, clinical trial compared postoperative pain in dogs undergoing major abdominal surgery. Sixteen client-owned dogs were anaesthetized with a standardized balanced protocol including opioids and received either 2 mg/kg ropivacaine IP (0.27 mL/kg) and a 1 mg/kg INC splash (0.13 mL/kg) or equal volumes of saline. Influence of the treatment on heart rate (HR) and postoperative pain was assessed using the Short Form of the Glasgow Composite Pain Scale (GCPS-SF), a dynamic interactive visual analogue scale (DIVAS) and mechanical nociceptive threshold testing (MNT). Data was tested with mixed ordinal regression and log linear mixed models for 0.5, 1, 2, 3, 4, 6, 8, 10 and 12 h after extubation. Rescue analgesia was given to 3/8 dogs after ropivacaine and 0/8 dogs after saline. GCPS-SF and MNT were not different between groups. DIVAS was slightly higher after ropivacaine (odds increased by 5.44 (confidence interval (CI) 1.17-9.96, p = 0.012)), and HR after ropivacaine was 0.76 * that after saline (CI 0.61-0.96, p = 0.02) with no effect of time (p = 0.1). Undiluted ropivacaine IP and INC was not beneficial for postoperative analgesia.

Sedative effects and changes in cardiac rhythm with intravenous premedication of medetomidine, butorphanol and ketamine in dogs

OBJECTIVE

To determine the sedative effects and characteristics of cardiac rhythm with intravenous (IV) premedication of medetomidine, butorphanol and ketamine in dogs.

STUDY DESIGN

Prospective, blinded, randomized clinical trial.

ANIMALS

A total of 116 client-owned healthy dogs undergoing elective surgery.

METHODS

Dogs were randomly allocated one of four groups: group M, medetomidine 5 μg kg^-1; group B, butorphanol 0.2 mg kg^-1; group MB, medetomidine 5 μg kg^-1 and butorphanol 0.2 mg kg^-1; or group MBK, medetomidine 5 μg kg^-1, butorphanol 0.2 mg kg^-1 and ketamine 1 mg kg^-1 IV. Sedation was assessed using a numerical descriptive scale. Heart rate (HR) and rhythm were monitored; propofol dose (mg kg^-1 IV) to allow orotracheal intubation was documented. Data were analysed using anova, accounting for multiple testing with the Tukey honest significant difference test.

RESULTS

Sedation scores varied significantly between all groups at all time points, except between groups MB and MBK at four time points. HR decreased in all groups: most in groups M and MB, least in group B. HR was initially higher in group MBK than in groups M and MB. Arrhythmias occurred in all groups: group B showed second-degree atrioventricular blocks occasionally, all other groups showed additionally ventricular escape complexes and bundle branch blocks. Dose of propofol required for orotracheal intubation was significantly higher in group B (5.0 ± 2.0 mg kg^-1) than in group M (2.6 ± 0.6 mg kg^-1). Although no difference could be demonstrated between groups MB (1.4 ± 0.6 mg kg^-1) and MBK (0.9 ± 0.8 mg kg^-1), both groups required significantly less propofol than group M.

CONCLUSION AND CLINICAL RELEVANCE

Medetomidine-based premedication protocols led to various bradyarrhythmias. Addition of subanaesthetic doses of ketamine to medetomidine-based protocols resulted in higher HRs, fewer bradyarrhythmias and fewer animals that required propofol for intubation without causing side effects in healthy dogs.

Intraocular pressure and cardiovascular effects of dexmedetomidine premedication and tiletamine-zolazepam for anesthetic induction in dogs

Background and Aim

The effect of anesthetic drugs on intraocular pressure (IOP) is an important concern in ophthalmic surgery. The impact of dexmedetomidine (DEX) combined with tiletamine-zolazepam on IOP is scarcely studied. This study aimed to evaluate IOP and cardiovascular effects in dogs after premedication with 5 μg/kg (DEX5) or 10 μg/kg (DEX10) of intramuscular DEX followed by intravenous tiletamine-zolazepam administration for induction of anesthesia in healthy dogs.

Materials and Methods

Eighteen dogs, American Society of Anesthesiologists I or II, without ocular abnormality were investigated. All dogs were randomly divided into the DEX5 (n = 9) and DEX10 groups (n = 9). The IOP, heart rate (HR), systolic blood pressure (SBP), oxygen saturation, and sedation scale were measured before premedication (baseline), after premedication at 5, 10, 15, and 20 min, after tiletamine-zolazepam administration, after endotracheal intubation, and post-operative.

Results

There were no significant differences between the groups at any time point. The DEX5 and DEX10 groups had significantly decreased HR values at 10 min compared with baseline. The IOP at 20 min was significantly lower compared to the baseline in the DEX10 group. Moreover, the DEX10 group showed increased IOP, HR, SBP, and sedation scale values after induction and intubation compared with 20 min, but these values did not differ significantly from baseline. All parameters of both groups did not change significantly between post-operative and baseline.

Conclusion

Intramuscular DEX (10 μg/kg) is an appropriate premedication in ophthalmic examination or surgical procedures. Moreover, it could be combined with tiletamine-zolazepam for generalized anesthesia in dogs with an ophthalmic problem, as it had no clinically significant effects on IOP or cardiovascular values.

Comparison of the sedative and analgesic effects of butorphanol with acepromazine, midazolam, or dexmedetomidine following propofol induction and isoflurane maintenance in canines

Adequate sedation and excellent depth of analgesia were recorded in all the four groups after induction to the end of surgical procedure, however, significantly higher sedation score and depth of analgesia were observed in group D and significantly lower was observed in group A in comparison to other groups. Butorphanol with acepromazine, midazolam, or dexmedetomidine provides adequate sedation and analgesia in the dogs, before induction with propofol, so it made handling of the animals proper and safe before induction. Dexmedetomidine produces most profound sedation and analgesia followed by midazolam and acepromazine along with butorphanol.

Analgesic efficacy of ultrasound-guided transversus abdominis plane block in dogs undergoing ovariectomy

Background

In medicine, the transversus abdominis plane (TAP) block has been shown as an effective method of analgesia in several surgical procedures. In this context, this prospective, randomized, blinded study aimed to evaluate the analgesic efficacy of TAP block, guided by ultrasound in female dogs submitted to ovariectomy.

Methods

Therefore, 32 animals randomly assigned in two groups (n = 16) were used. Groups consisted of TAP block control (TBC) which received water injection (0.2 ml kg⁻¹ point), and TAP block bupivacaine (TBB) which received bupivacaine (0.2 ml kg⁻¹ point at 0.25%); both groups were submitted to four-point approach. Animals were pre-medicated with acepromazine (0.03 mg kg⁻¹) and meperidine (2 mg kg⁻¹) IM, propofol was used as anesthetic induction (3–5 mg kg⁻¹) IV, and isoflurane was used to maintain. To standardize groups, the animals received a continuous infusion of remifentanil (0.2μg kg⁻¹ min) and rocuronium (0.6 mg kg⁻¹) IV in the intraoperative period. Variables measured were the heart and respiratory rates, blood pressure, temperature, peripheral oxyhemoglobin saturation, exhaled carbon dioxide concentration, exhaled isoflurane concentration, serum cortisol, analgesia, and sedation. Before the pre-anesthetic medication (Baseline) and 1, 2, 4, 6, and 8 h after extubation, pain and sedation were assessed using a numeric rating scale (NRS), Glasgow composite measure pain scale (GCMPS-SF), and sedation scale. Moreover, serum cortisol was measured at different moments.

Results

The results show that in the intraoperative period, there was no significant difference between groups. After surgery, in TBC, 13 out of 16 animals required analgesic rescue, whereas, in TBB, this occurred only in one animal. Regarding the measurement of serum cortisol, the TBC group showed a significant difference when compared to the baseline time in the traction of the first ovary (p < 0.0001), 2 h (p = 0.0441), and 8 h (p = 0.0384) after extubation. In TBB, cortisol showed a significant increase only in the traction of the first ovary and 2 h after extubation (p < 0.0001).

Conclusion

The technique using ultrasound-guided TAP block in two points approach by hemiabdomen with 0.2 ml kg⁻¹ bupivacaine 0.25% was effective in providing post-operative analgesia in dogs undergoing ovariectomy.

Development of reference intervals for pupillometry in healthy dogs

BACKGROUND

Pupillometry, the measurement of pupil size and reactivity to a stimulus, has various uses in both human and veterinary medicine. These reflect autonomic tone, with the potential to assess nociception and emotion. Infrared pupillometry reduces inaccuracies that may occur when the pupillary light reflex is determined subjectively by the examiner. To our knowledge, there are no published studies outlining normal reference intervals for automated pupillometry in dogs.

OBJECTIVE

The objective of this study was to develop de novo automated pupillometry reference intervals from 126 healthy canine eyes.

METHODS

The pupillary light reflex (PLR) was measured with a handheld pupillometer (NeurOptics™ PLR-200™ Pupillometer). Parameters recorded included maximum pupil diameter (MAX), minimum pupil diameter (MIN), percent constriction (CON), latency (LAT), average constriction velocity (ACV), maximum constriction velocity (MCV), average dilation velocity (ADV) and time to 75% pupil diameter recovery (T75). One measurement was obtained for each eye.

RESULTS

The following reference intervals were developed: MAX (6.05-11.30 mm), MIN (3.76-9.44 mm), CON (-37.89 to -9.64 %), LAT (0.11-0.30 s), ACV (-6.39 to -2.63 mm/ s), MCV (-8.45 to -3.75 mm/s), ADV (-0.21-1.77 mm/s), and T75 (0.49-3.20 s).

CLINICAL SIGNIFICANCE

The reference intervals developed in this study are an essential first step to facilitate future research exploring pupillometry as a pain assessment method in dogs.

Postoperative Acupuncture is as Effective as Preoperative Acupuncture or Meloxicam in Dogs Undergoing Ovariohysterectomy: a Blind Randomized Study

Background

Acupuncture has the same analgesic effect as non-steroidal antiinflammatory drugs and opioids. It is challenging to perform preoperative acupuncture in unmanageable animals, while the residual postoperative anesthetic effect facilitates the performance of acupuncture postoperatively.

Objectives

To compare preoperative acupuncture or meloxicam versus postoperative acupuncture for postoperative analgesia after ovariohysterectomy.

Methods

This is a horizontal prospective positive control blind randomized experimental study. Thirty-six dogs were randomly divided into three groups: GA (preemptive acupuncture), GPA (postoperative acupuncture), and GM (meloxicam 0.2 mg/kg IV preoperatively). After sedation with acepromazine (0.05 mg/kg IM), anesthesia was induced with propofol (5.3 ± 0.3 mg/kg) and maintained with isoflurane/O2. Fentanyl (2 μg/kg, IV) was administered immediately before surgery. Bilateral acupuncture was performed at acupoints Large intestine 4, Spleen 6, and Stomach 36 for 20 minutes, before (GA) or immediately after surgery (GPA). Pain was evaluated by an observer blind to the treatment using the Glasgow scale before and for 24 hours after ovariohysterectomy. Dogs with a score ≥ 6 received rescue analgesia with morphine (0.5 mg/kg IM). Nonparametric data were analyzed by the Kruskal-Wallis test, followed by Dunn's test and parametric data by ANOVA followed by Tukey's test.

Results

Two GA and one GPA dogs received rescue analgesia once. Two GM dogs received rescue analgesia and one of those was treated again twice. There were no differences in the number of dogs receiving rescue analgesia between groups (p = 0.80).

Conclusion

Postoperative acupuncture was as effective as preoperative acupuncture or meloxicam in female dogs undergoing ovariohysterectomy.

Laparoscopic versus Open Ovariectomy in Bitches: Changes in Cardiorespiratory Values, Blood Parameters, and Sevoflurane Requirements Associated with the Surgical Technique

The aim of this study was to examine the cardiorespiratory and blood changes associated with pneumoperitoneum (PNP) in laparoscopic ovariectomy (LAP Ove), as well as sevoflurane requirements, comparing them to those determined in open surgery (LPT Ove). The study was performed in 16 bitches submitted to LAP or LPT Ove. The cardiorespiratory and end-tidal sevoflurane concentration values were recorded as follows: at the beginning of surgery (T1), after the right ovary resection (T2), after the left ovary resection (T3), and after surgical closure (T4). Blood samples were taken before and after PNP. Among the cardiorespiratory parameters, no differences were observed in the values of end-tidal CO2, minute volume, and heart rate. In the LAP Ove group, a significant increase in inspiratory pressures and a decreased compliance were identified at T2 and T3. Significant higher arterial pressure values were observed in both groups at T2 and T3, with this increase especially marked at T2 in the LPT Ove group. Sevoflurane requirements were significantly higher in the LPT group during ovarian resection. Finally, in terms of the hematochemical parameters, statistical differences were recorded between pre- and post-operative assessments, but not between both surgical groups. The pathophysiological effects associated with PNP seemed to be transient and well-tolerated by healthy dogs.

Description and validation of a new descriptive and multiparametric numeric rating scale to assess sedation in cats

The objective of this study was to design and assess the validity and reliability of a new feline multiparametric sedation scale (FMSS). A total of 89 household cats were recruited, enabling a total of 534 sedation assessments. Every assessment was performed by 3 blinded observers with varying expertise levels (Level 1: Student; Level 2: RVT; Level 3: ACVAA diplomate or senior resident). For comparison purposes, a visual analogue scale (VAS) and a Simple Qualitative Scale (SQS) were also used concurrently, with the VAS considered the gold standard. The new scale had excellent inter-observer agreement among experience groups with weighted Kappa scores of 0.84 (Levels 1 versus 2), 0.82 (Levels 2 versus 3), and 0.84 (Levels 1 versus 3), with P < 0.0001 for all comparisons. There was a high degree of association between FMSS and VAS (r = 0.90, P < 0.0001) and between FMSS and SQS (r = 0.89, P < 0.0001). Final FMSS numerical values were paired with levels of sedation with None = 0 (0 to 5), Mild = 4 (1 to 7), Moderate = 6 (2 to 10), and Profound = 12 (7 to 12); furthermore, differences were detected between pre- and post-sedation evaluations (P = 0.001). This scale demonstrated internal consistency and sensitivity even when evaluating drugs or doses with minimal sedative effects and there was very strong interrater reliability, independent of experience level. Based on this clinical study, we concluded that the use of this sedation scale is appropriate when objective numerical sedation quantification is required, in either a clinical or research setting.

Perioperative Analgesic Efficacy of Yamamoto New Scalp Acupuncture for Canine Mastectomy Combined with Ovariohysterectomy: a Randomized, Controlled Clinical Trial

Background

Yamamoto New Scalp Acupuncture (YNSA) is a therapy based on the stimulation of points on the scalp and applied to treat different states of pain.

Objectives

To investigate the analgesic efficacy of YNSA for dogs undergoing radical unilateral mastectomy with ovariohysterectomy.

Methods

Twenty-four dogs were randomly distributed into two treatments (n = 12, per group): bilateral stimulation of basic B, D, and E points (YNSA group) and no application of acupuncture (control group). All dogs were sedated with morphine; anesthesia was induced with propofol and maintained with isoflurane. Fentanyl was intraoperatively administered to control cardiovascular responses to surgical stimulation. Postoperative pain was assessed using an interactive visual analog scale (IVAS) and the short-form of the Glasgow Composite Pain Scale (CMPS-SF). Morphine was administered as rescue analgesia. Data were analyzed using t-tests, Fisher's exact test, Mann-Whitney U test, and Friedman test (p < 0.05).

Results

Intraoperatively, the number of dogs requiring supplemental analgesic and the number of doses of fentanyl were lower in the YNSA group than in the control group (p = 0.027-0.034). The IVAS pain scores recorded from 0.5 h to 1 h post-extubation in the YNSA group were lower than those in the control group (p = 0.021-0.023). Postoperative rescue analgesia and CMPS-SF pain scores did not differ between the groups.

Conclusion

YNSA decreases intraoperative fentanyl requirements and provides minimal postoperative analgesic benefits to dogs undergoing unilateral mastectomy with ovariohysterectomy.

The effect of splash block on the need for analgesia in dogs subjected to video-assisted ovariectomy

Objectives

The present study aimed to demonstrate the efficacy of splash block using lidocaine to provide additional analgesia during ovariectomy in bitches. To identify an acute intraoperative nociceptive response, three clinical parameters were used: increased blood pressure, heart rate and respiratory rate.

Material and Methods

Forty healthy bitches were randomly assigned to receive 2% lidocaine (L group) topical application (splash block) on both ovaries (2 mg/kg each), or an equal volume of NaCl 0.9% at the same sites (C group). A fentanyl bolus (2 µg/kg) was administered intraoperatively in response to an increase in blood pressure, heart rate or respiratory rate during surgery (> 30% compared with the pre‐incisional values).

Results

Local lidocaine administration significantly reduced the need for supplementary fentanyl. Dogs in the L group showed greater intraoperative hemodynamic stability and lower surgical pain than those in the C group. In addition to the routine anaesthetic protocol, the local anaesthesia used in the present study was safe and caused no cardiopulmonary suppression. In addition, it significantly reduced the need for mandatory systemic or rescue analgesia.

Clinical Significance

Ovariectomy is a common surgical procedure in bitches. Analgesia during this procedure is important because intraoperative pain can cause negative effects that prevent patient recovery. This study aimed to demonstrate the analgesic efficacy of lidocaine splash block in video‐assisted ovariectomy in dogs. The results showed that splash block improved surgical analgesia during canine laparoscopic ovariectomy. Considering its relative simplicity, low cost, and safety, splash block could be used in daily clinical practice.

Effect of Sedation on the Neurological Examination of the Patellar and Withdrawal Reflexes in Healthy Dogs

Introduction: Pain, temperament, fear, and anxiety can prevent safe and accurate evaluation of common neurologic reflexes in dogs. When sedation is used it is unknown how the neurological examination, and specifically patellar and withdrawal reflexes are affected, and, if present, how long any effect might last. The purpose of this study is to investigate the effect of sedation on the evaluation of select common limb spinal reflexes in healthy dogs.

Material and Methods: Fourteen healthy dogs with normal neurologic exams were included. After placing joint landmarks, patellar reflex and pelvic and thoracic limb withdrawal reflexes were tested. Joint angles were measured, obtaining reflex angle endpoints, change in angle, and change in time to reflex completion. These measurements were recorded at different time points: prior to sedation (awake timepoint), 15 and 30 min following administration of standardized sedation protocol of dexmedetomidine and butorphanol, and 15 and 30 min following administration of a standardized reversal agent, atipamazole.

Results: For patellar reflex, the stifle end angle increased from 91.5 to 108.55 degrees (p < 0.0001) 15 min following sedation, and remained increased at 104.5 degrees (p < 0.0001) 30 min following sedation. Stifle change in angle increased from 9.6 to 24.4 degrees (p < 0.0001) 15 min following sedation, and remained increased at 20.85 degrees (p < 0.0001) and 11 degrees (p = 0.012) at 30 min sedation and 15 min reversal. Tarsal joint in pelvic withdrawal and elbow in thoracic withdrawal reflexes did not differ in at any timepoint of sedation or reversal when compared with the awake timepoint, for end angle or change in angle. The increases in end angle and change in angle for patellar reflex generated a change in time for patellar reflex from 0.12 s (awake) to 0.129 s (15 min sedation) which was statistically significant (p = 0.041). Change in time did not differ for pelvic withdrawal or thoracic withdrawal.

Discussion/Conclusions: Reflexes were elicited in all dogs under sedation. Sedation does not affect the evaluation of the withdrawal reflex on any limb but improves the visualization of the patellar reflex in this group of neurologically normal dogs.

A Pharmacokinetic-Pharmacodynamic Study of Intravenous Midazolam and Flumazenil in Adult New Zealand White-Californian Rabbits (Oryctolagus cuniculus)

Flumazenil, a competitive GABAA receptor antagonist, is commonly used in rabbits to shorten sedation or postanesthetic recovery after benzodiazepine administration. However, no combined pharmacokinetic (PK) and pharmacodynamic (PD) data are available to guide its administration in this species. In a prospective, randomized, blinded, crossover study design, the efficacy of IV flumazenil (FLU; 0.05 mg/kg) or saline control (SAL; equal volume) to reverse the loss of righting reflex (LORR) induced by IV midazolam (1.2 mg/kg) was investigated in 15 New Zealand white rabbits (2.73 to 4.65 kg, 1 y old). Rabbits were instrumented with arterial (central auricular artery) and venous (marginal auricular vein) catheters. After baseline blood sampling, IV midazolam was injected (T0). Flumazenil or saline (FLU/SAL) was injected 30 s after LORR. Arterial blood samples were collected at 1 and 3 min after midazolam injection, and at 1, 3, 6, 10, 15, 21, 28, 36, 45 and 60 min after injection with flumazenil. Plasma samples for midazolam, 1-OH-midazolam and flumazenil were analyzed using high performance liquid chromatography-high-resolution mass spectrometry and the time to return of righting reflex (ReRR) was compared between groups (Wilcoxon test). FLU terminal half-life, plasma clearance and volume of distribution were 26.3 min [95%CI: 23.3 to 29.3], 18.74 mL/min/kg [16.47 to 21.00] and 0.63 L/kg [0.55 to 0.71], respectively. ReRR was 25 times faster in rabbits treated with FLU (23 [8 to 44] s) compared with SAL (576 [130 to 1141] s; 95%CI [425 to 914 s]). Return of sedation (lateral recumbency) occurred in both groups (7/13 in FLU; 12/13 in SAL) with return of LORR in a few animals (4/13 in FLU; 7/13 in SAL) at 1540 [858 to 2328] s. In the population and anesthesia protocol studied, flumazenil quickly and reliably reversed sedation induced by midazolam injection. However, the potential return of sedation after flumazenil administration warrants careful monitoring in the recovery period.

Effects of perioperative saphenous and sciatic nerve blocks, lumbosacral epidural or morphine-lidocaine-ketamine infusion on postoperative pain and sedation in dogs undergoing tibial plateau leveling osteotomy

OBJECTIVE

To compare the quality of postoperative analgesia and sedation after preoperative saphenous and sciatic nerve blockade, preoperative lumbosacral epidural injection and perioperative intravenous (IV) morphine, lidocaine and ketamine infusions in dogs undergoing stifle arthroscopy and tibial plateau leveling osteotomy (TPLO) under general anesthesia.

STUDY DESIGN

Prospective, blinded, randomized, clinical comparison study.

ANIMALS

A total of 45 dogs weighing 33.9 (15.9-56.7) kg and aged 5.2 (1.0-12.0) years, mean (range), undergoing elective unilateral TPLO for spontaneous cranial cruciate ligament rupture.

METHODS

Client-owned dogs were enrolled. Dogs were randomly assigned to one of three groups: group MLK, perioperative IV morphine, lidocaine and ketamine infusion; group EPID, lumbosacral epidural with ropivacaine and morphine; or group SSNB, saphenous and sciatic nerve blockade with ropivacaine. Routine stifle arthroscopy followed by TPLO surgery was performed. Sedation and pain scores were assessed at 0, 2, 4, 8 and 24 hours following extubation. Rescue analgesia was administered as prescribed by Glasgow composite pain score-short form score >5.

RESULTS

Sedation scores for MLK were higher than EPID and SSNB. Pain scores for SSNB were lower than those for EPID and MLK. No significant differences were found in anesthesia duration or surgery duration among groups. No dogs required rescue analgesia.

CONCLUSIONS AND CLINICAL RELEVANCE

Although analgesia was adequate in all groups, the best combination of analgesia without increased sedation was recorded for SSNB.

Comparison between dexmedetomidine and acepromazine in combination with methadone for premedication in brachycephalic dogs undergoing surgery for brachycephalic obstructive airway syndrome

OBJECTIVE

To compare dexmedetomidine with acepromazine for premedication combined with methadone in dogs undergoing brachycephalic obstructive airway syndrome (BOAS) surgery.

STUDY DESIGN

Randomized, blinded clinical study.

ANIMALS

A group of 40 dogs weighing mean (± standard deviation) 10.5 ± 6 kg, aged 2.6 ± 1.9 years.

METHODS

Dogs received either acepromazine 20 μg kg^-1 (group A) or dexmedetomidine 2 μg kg^-1 (group D) intramuscularly with methadone 0.3 mg kg^-1. Anaesthesia was induced with propofol and maintained with sevoflurane. Sedation (0-18), induction (0-6) and recovery (0-5) qualities were scored. Propofol dose, hypotension incidence, mechanical ventilation requirement, extubation time, additional sedation, oxygen supplementation, regurgitation and emergency intubation following premedication or during recovery were recorded. Data were analysed using t tests, Mann-Whitney U or Chi-square tests.

RESULTS

Group A dogs were less sedated [median (range): 1.5 (0-12)] than group D [5 (1-18)] (p = 0.021) and required more propofol [3.5 (1-7) versus 2.4 (1-8) mg kg^-1; p = 0.018]. Induction scores [group A: 5 (4-5); group D 5 (3-5)] (p = 0.989), recovery scores [group A 5 (4-5); group D 5(3-5)](p = 0.738) and anaesthesia duration [group A:93 (50-170); group D 96 (54-263) minutes] (p = 0.758) were similar between groups. Time to extubation was longer in group A 12.5 (3-35) versus group D 5.5 (0-15) minutes; (p = 0.005). During recovery, two dogs required emergency intubation (p > 0.99) and five dogs required additional sedation (p > 0.99). Oxygen supplementation was required in 16 and 12 dogs in group A and D, respectively (p = 0.167); no dogs in group A and one dog in group D regurgitated (p = 0.311).

CONCLUSIONS AND CLINICAL RELEVANCE

Dexmedetomidine 2 μg kg^-1 produces more sedation but similar recovery quality to acepromazine 20 μg kg^-1 combined with methadone in dogs undergoing BOAS surgery.

Impact of flow and temperature on non-dyspnoeic dogs' tolerance undergoing high-flow oxygen therapy

OBJECTIVES

To prospectively describe the impact of gas flow rate and temperature on dog's tolerance of high-flow nasal oxygen therapy during recovery from anaesthesia, hypothesizing that higher flow rates and temperatures will decrease tolerance.

MATERIALS AND METHODS

Twelve non-dyspnoeic client-owned dogs recovering from general anaesthesia were included in this study. After extubation, a nasal cannula was positioned and high-flow nasal oxygen therapy was initiated. Two flow rates (two or four time the theoretical minute ventilation: HF2 and HF4), each of them combined with two temperatures (31 and 37°C: T31 and T37), were randomly applied (four conditions per dog). For each condition, cardiovascular and respiratory parameters (heart rate, respiratory rate, systolic arterial blood pressure and pulse oximeter oxygen saturation), sedation score and tolerance score were recorded at initiation (T₀ ) and after 10 minutes of accommodation (T₁₀ ).

RESULTS

Sedation scores were not significantly different between the four conditions. Cardiovascular and respiratory parameters were not significantly different between any condition at both T₀ and T₁₀ . Tolerance scores were good and not significantly different between any flow rate or temperature (HF2-T31: 4 (2-4), HF4-T31: 4 (2-4), HF2-T37: 4 (2-4), HF4-T37: 4 (1-4)).

CLINICAL SIGNIFICANCE

The gas flow rates and temperatures studied have no impact on tolerance during the recovery period of non-dyspnoeic dogs, and high-flow nasal cannula is well tolerated. Further studies are required to confirm these results in dyspnoeic dogs.

Lumbar Epidural: Anatomical and Clinical Study in Dogs Submitted to Ovariohysterectomy

Epidural anesthesia minimizes perioperative pain in dogs. It is considered that epidural solution dispersion in cadavers is similar to alive dogs. The objective of the anatomical study was to compare the dispersion of 0.2 mL/kg 0.25% bupivacaine and iohexol via lumbar epidural (L1–L2) under fluoroscopic guidance in 10 thawed cadavers (GC) and 13 female dogs (G0.25) (5–15 kg; body score 4/5). The objective of the clinical study was to evaluate postoperative analgesic consumption and sedation for 6 h after extubation of dogs submitted to ovariohysterectomy when using 0.25% (G0.25; n = 10) bupivacaine with the intraoperative use of fentanyl (GF; n = 10). Parametric data were compared by the t-test and non-parametric data by the Mann Whitney test. Pain and sedation scores were evaluated over time by the Friedman test, followed by the Dunn test. Alive dogs presented greater epidural dispersion (17 ± 3 vertebrae) than thawed cadavers (11 ± 4 vertebrae; p = 0.002). All dogs treated with fentanyl and only one dog treated with 0.25% epidural bupivacaine presented pain scores above the cut-off point of the Glasgow Composite Measure Pain Scale Short-Form (GCMPS-SF) and required postoperative rescue analgesia up to 6 h after extubation. The sedation score was higher at all postoperative moments compared to preoperative moments in the G0.25 and GF, except for evaluations performed at 5 and 6 h after extubation in the GF. Greater sedation was observed immediately after extubation in the GF compared to the G0.25, and there was greater sedation in the G0.25 compared to the GF from 3 to 6 h after extubation. The conclusion of the anatomical study was that L1–L2 epidural bupivacaine dispersion is lower in canine thawed cadavers than in alive dogs. Conclusion of the clinical study was that lumbar epidural anesthesia improved postoperative analgesia and produced longer postoperative sedation when compared to fentanyl.

Comparison of the efficacy of 2 sedative protocols in pediatric dogs undergoing brainstem auditory-evoked response testing

This study compared the quality of sedation with dexmedetomidine or alfaxalone during brainstem auditory-evoked response (BAER) tests in 6- to 17-week-old dogs. This was a prospective, randomized clinical study involving 19 client-owned pediatric dogs of breeds with reported congenital deafness. Group A (G_A) received alfaxalone, 2 mg/kg body weight (BW) (n = 9) and group D (G_D) dexmedetomidine, 0.005 mg/kg BW, and postprocedure antagonism with atipamezole (n = 10) intramuscularly. Time from injection to sedation, duration of sedation, sedation scores, need for re-dosing, rectal temperature, pulse and respiratory rate were recorded at baseline, before and after the BAER test, and once recovered from sedation. Pulse rate was significantly lower in G_D (P = 0.004) and the number of re-dosing was significantly higher in G_A (P = 0.011). Both sedation protocols allowed good quality BAER test recordings in pediatric dogs. Sedation with dexmedetomidine required less re-dosing, whereas alfaxalone maintained more physiological pulse rates.

Pharmacokinetics and efficacy of trazodone following rectal administration of a single dose to healthy dogs

OBJECTIVE

To determine the pharmacokinetics and efficacy of trazodone following rectal administration of a single dose to healthy dogs.

ANIMALS

6 healthy adult dogs.

PROCEDURES

Each dog received a single dose of trazodone (approx 8 mg/kg) per rectum. Trazodone tablets were crushed into a powder, mixed with 5 mL of tap water, and injected into the rectum via a red rubber catheter. Sedation scores were assigned, and blood samples were collected for determination of plasma trazodone concentration at predetermined times before and after drug administration. Pharmacokinetic parameters were estimated by noncompartmental analysis.

RESULTS

Plasma trazodone concentration remained below the detection limit for 1 dog even though it became moderately sedate. Median (interquartile [25th to 75th percentile] range [IQR]) maximum plasma trazodone concentration and volume of distribution and clearance corrected for bioavailability were 1.00 μg/mL (0.66 to 1.40 μg/mL), 10.3 L/kg (7.37 to 14.4 L/kg), and 639 mL/kg/h (594 to 719 mL/kg/h), respectively. Median time to maximum plasma trazodone concentration and elimination half-life were 15 minutes (range, 15 to 30 minutes) and 12 hours (IQR, 7.99 to 12.7 hours), respectively. All dogs became mildly or moderately sedate, and the extent of sedation was maximal at a median of 30 minutes (IQR, 30 to 60 minutes) after trazodone administration. No adverse effects were observed.

CONCLUSIONS AND CLINICAL RELEVANCE

Rectal administration of trazodone may be a viable option for sedation and treatment of anxiety in dogs for which administration of sedatives and anxiolytics by other routes is contraindicated. Further research is necessary to better elucidate the pharmacokinetics and efficacy of trazodone following rectal administration and determine optimal dosing.

Postoperative pain behaviours in rabbits following orthopaedic surgery and effect of observer presence

Rabbits are widely used in studies focusing on pain. However, pain is undertreated in this species and one possible factor to explain this is the lack of evaluation methods. The objective of this study was to identify behaviours related to orthopaedic pain in rabbits and to evaluate the influence of the presence of an observer on these behaviours. Twenty-eight rabbits undergoing orthopaedic surgery and filmed 24 hours before surgery, and 1 hour (before rescue analgesia), 4 hours (3 hours after rescue analgesia), and 24 hours post-recovery were observed in the presence and absence of an observer. The frequency and/or duration of behaviours were compared over time and between the presence and absence of the observer using the Friedman and Wilcoxon tests respectively. Data are expressed as median and interquartile range and a significant difference was considered when p<0.05. At 1 hour post-recovery, the rabbits showed reduced activity, hopping, change posture, position in the cage, explore, and open eyes in both the presence and absence of the observer. In the absence of the observer, quadrupedal posture, interact with pinecone, and eat carrot also decreased, while wince behaviour increased. In the presence of the observer, before surgery, the rabbits were less active (Presence-280; 162–300, Absence-300; 300–300) and presented a lower duration of explore (Presence-3; 0–32, Absence-40; 4–63). Post-recovery the rabbits flinched less (Presence-0; 0–0, Absence-0; 0–1) and suspended the affected limb less (Presence-0; 0–0, Absence-0; 0–65). After rescue analgesia the rabbits put weight on and raised the affected limb less (Presence-0; 0–0, Absence-0; 0–2) and licked the affected area less (Presence-0; 0–0, Absence-0; 0–2). These findings demonstrate that the presence of the observer inhibited pain-free behaviours in the rabbits, leading to a false impression of pain, and after the surgery the rabbits masked some pain signs related to the affected area.

Effect of Medetomidine, Dexmedetomidine, and Their Reversal with Atipamezole on the Nociceptive Withdrawal Reflex in Beagles

The objectives were: (1) to compare the antinociceptive activity of dexmedetomidine and medetomidine, and (2) to investigate its modulation by atipamezole. This prospective, randomized, blinded experimental trial was carried out on eight beagles. During the first session, dogs received either medetomidine (MED) (0.02 mg kg-1 intravenously (IV)] or dexmedetomidine (DEX) [0.01 mg kg-1 IV), followed by either atipamezole (ATI) (0.1 mg kg-1) or an equivalent volume of saline (SAL) administered intramuscularly 45 min later. The opposite treatments were administered in a second session 10-14 days later. The nociceptive withdrawal reflex (NWR) threshold was determined using a continuous tracking approach. Sedation was scored (0 to 21) every 10 min. Both drugs (MED and DEX) increased the NWR thresholds significantly up to 5.0 (3.7-5.9) and 4.4 (3.9-4.8) times the baseline (p = 0.547), at seven (3-11) and six (4-9) minutes (p = 0.938), respectively. Sedation scores were not different between MED and DEX during the first 45 min (15 (12-17), p = 0.67). Atipamezole antagonized sedation within 25 (15-25) minutes (p = 0.008) and antinociception within five (3-6) minutes (p = 0.008). Following atipamezole, additional analgesics may be needed to maintain pain relief.

Sedative and cardiorespiratory effects of intramuscular administration of alfaxalone and butorphanol combined with acepromazine, midazolam, or dexmedetomidine in dogs

OBJECTIVE

To evaluate the sedative and cardiorespiratory effects of IM administration of alfaxalone and butorphanol combined with acepromazine, midazolam, or dexmedetomidine in dogs.

ANIMALS

6 young healthy mixed-breed hounds.

PROCEDURES

Dogs received each of 3 treatments (alfaxalone [2 mg/kg] and butorphanol [0.4 mg/kg] combined with acepromazine [0.02 mg/kg; AB-ace], midazolam [0.2 mg/kg; AB-mid], or dexmedetomidine [0.005 mg/kg; AB-dex], IM) in a blinded, randomized crossover-design study with a 1-week washout period between treatments. Sedation scores and cardiorespiratory variables were recorded at predetermined time points. Data were analyzed by use of mixed-model ANOVA and linear generalized estimating equations with post hoc adjustments.

RESULTS

All treatments resulted in moderate to deep sedation (median score, ≥ 15/21) ≤ 5 minutes after injection. Sedation scores did not differ among treatments until the 40-minute time point, when the score was higher for AB-dex than for other treatments. Administration of AB-dex resulted in median scores reflecting deep sedation until 130 minutes, versus 80 and 60 minutes for AB-ace and AB-mid, respectively, after injection. Heart rate, cardiac output, and oxygen delivery decreased significantly after AB-dex, but not AB-ace or AB-mid administration. Respiratory variables remained within clinically acceptable ranges after all treatments. Undesirable recovery characteristics were observed in 4 dogs after AB-mid treatment. Four dogs required atipamezole administration 180 minutes after AB-dex injection.

CONCLUSIONS AND CLINICAL RELEVANCE

All protocols produced reliable sedation. The results indicated that in young, healthy dogs, AB-mid may produce undesirable recovery characteristics; AB-dex treatment caused cardiovascular depression and should be used with caution.

The SIESTA (SEAAV Integrated evaluation sedation tool for anaesthesia) project: Initial development of a multifactorial sedation assessment tool for dogs

OBJECTIVE

The aim of the study was to develop a multifactorial tool for assessment of sedation in dogs.

METHODS

Following a modified Delphi method, thirty-eight veterinary anaesthetists were contacted to describe the following levels of awareness: no-sedation, light, moderate, profound sedation and excitation. The answers were summarized in descriptors for each level. A questionnaire was created with all the variables obtained from the descriptors. The questionnaire was returned to the panel of anaesthetists to be used before and after real sedations in conjunction with the previous 5-point categorical scale. Data obtained were analysed using the classification-tree and random-forest methods.

RESULTS

Twenty-three anaesthetists (60%) replied with descriptions. The descriptors and study variables were grouped in categories: state-of-mind, posture, movements, stimuli-response, behaviour, response-to-restraint, muscle tone, physiological data, facial-expression, eye position, eyelids, pupils, vocalization and feasibility-to-perform-intended-procedure. The anaesthetists returned 205 completed questionnaires. The levels of awareness reported by the anaesthetists were: no sedation in 92, mild (26), moderate (37) and profound in 50 cases. The classification-tree detected 6 main classifying variables: change in posture, response-to-restraint, head-elevation, response-to-toe-pinching, response-to-name, and movements. The random-forest found that the following variables: change in posture, response-to-restraint, head-elevation, response-to-name, movements, posture, response-to-toe-pinching, demeanour, righting-reflex and response-to-handclap, were classified correctly in 100% awake, 62% mild, 70% moderate and 86% of profound sedation cases.

DISCUSSION AND CONCLUSION

The questionnaire and methods developed here classified correctly the level of sedation in most cases. Further studies are needed to evaluate the validity of this tool in the clinical and research setting.

Addition of magnesium sulfate to intraperitoneal ropivacaine for perioperative analgesia in canine ovariohysterectomy

Magnesium may be used as an adjunctive analgesic for perioperative pain management because of its antinociceptive properties. This study investigated the analgesic efficacy of intraperitoneal ropivacaine combined with magnesium sulfate in canine ovariohysterectomy. Forty-five dogs sedated with acepromazine/meperidine and anesthetized with propofol/isoflurane were randomly distributed into three treatments, administered intraperitoneally (n = 15 per group): saline solution (group S), 0.25% ropivacaine (3 mg/kg) alone (group R), or in combination with magnesium sulfate (20 mg/kg, group R-Mg). Intravenous fentanyl was given to control cardiovascular responses to surgical stimulation. Postoperative pain was assessed using an Interactive Visual Analog Scale (IVAS), the short form of the Glasgow Composite Pain Scale, and mechanical nociceptive thresholds. Morphine/meloxicam was administered as rescue analgesia. Intraoperatively, the R-Mg group required less fentanyl (p = .02) and exhibited higher incidence of hypotension (systolic arterial pressure <90 mm Hg, p = .006) compared with the S group. Lower IVAS pain scores were recorded during the first hour in the R-Mg group than the other groups (p = .007-.045). Postoperative rescue analgesia did not differ between groups. Intraperitoneal magnesium sulfate administration, in spite of decreasing intraoperative opioid requirements, increased the incidence of hypotension with minimal evidence of postoperative analgesic benefits.

Prevalence and management of pain in dogs in the emergency service of a veterinary teaching hospital

A prospective, observational, cross-sectional study documenting the prevalence of pain in dogs presented to the emergency service of a veterinary teaching hospital and their handling (times to triage, examination, treatment) was conducted. Pain was assessed and compared using a validated and an unvalidated pain assessment scale. Sedation was monitored using a validated scale. A first evaluation was completed in 109 dogs. A second evaluation was completed for 95 dogs: 36 (38%) were identified as painful and 53% (19/36) were provided analgesia in the clinic. The remainder either did not receive analgesia (6/36, 17%) or were prescribed an analgesic for administration at home (11/36, 31%). Of dogs receiving analgesia in the clinic, most showed a decrease in pain score (15/19, 79%). Pain assessment scales were positively correlated (r = 0.69, P < 0.0001) but the unvalidated scale was insensitive in discriminating changes. Between painful and non-painful dogs, progression did not differ: admission to treatment [P = 0.96, 95% confidence interval (CI): -23 to 22 minutes] and examination to treatment (P = 0.73, 95% CI: 14 to 20 minutes). Suboptimal analgesic use suggests focused training in pain assessment and analgesic use guided by a validated pain assessment scale, is warranted.

Effects of acupuncture at Pericardium-6 and Stomach-36 on nausea, sedation and gastrointestinal motility in healthy dogs administered intravenous lidocaine infusions

The objectives of this study were to assess gastrointestinal transit times, sedation, and signs of nausea associated with intravenous lidocaine infusions in dogs following targeted acupuncture at Pericardium-6 (PC6) and Stomach-36 (ST36). In a randomized, blind crossover design, 6 healthy, adult Beagles were fed thirty 1.5 mm barium-impregnated polyethylene spheres (BIPS), then were subject to 30 minutes of: 1) no acupuncture, 2) bilateral targeted acupuncture at PC6 and ST36, or 3) bilateral non-target acupuncture at Lung-5 (LU5) and Bladder-55 (BL55). Lidocaine was immediately administered at 1 mg/kg intravenously followed by 50 μg/kg/min. BIPS were tracked radiographically; sedation and nausea were scored at baseline (Time 0) and for 11 hours during lidocaine infusions. Transit times and sedation and nausea scores were analyzed with a linear mixed-effects model; the number of BIPS at defined time points was analyzed with a piecewise linear mixed-effects model. All P values were two-sided and P < 0.05 was considered significant. Sedation and nausea scores did not differ between treatments at any time point (all P > 0.05). However, nausea scores in all groups were significantly greater at Times 5 through 7 and at Time 11 compared to Time 0 whereas sedation scores in all groups were significantly greater at Times 2 through 11 compared to Time 0 (all P < 0.05). The number of BIPs found out of the stomach, the number found in the large intestine, gastric emptying and gastrointestinal transit times did not differ between treatments (all P > 0.05). Acupuncture at PC6 and ST36 did not alleviate nausea and sedation associated with lidocaine infusions in clinically normal animals or affect gastric emptying and gastrointestinal transit.

Comparison of the sedative effects of alfaxalone and methadone with or without midazolam in dogs

This blinded, randomized, prospective study evaluated the sedative and physiologic effects of a combination of alfaxalone and methadone with or without midazolam in adult dogs. Sixteen dogs received methadone (0.5 mg/kg body weight) and alfaxalone (1 mg/kg body weight), either with or without midazolam (0.5 mg/kg body weight), by intramuscular injection. Quality of sedation, heart rate, respiratory rate, systolic arterial pressure, rectal temperature, arterial oxygen saturation of hemoglobin, and dose of alfaxalone required for endotracheal intubation were recorded. Sedation score increased over time in both groups; however, dogs premedicated with methadone and alfaxalone appeared significantly less sedated than dogs premedicated with midazolam at 15, 20, and 25 minutes post-injection (P = 0.04). Dogs receiving methadone and alfaxalone were almost 5 times more likely to show excitement than those receiving midazolam (P = 0.03). We concluded that adding midazolam to an intramuscular combination of methadone and alfaxalone cannot be recommended in healthy dogs.

Evaluation of anesthesia produced by ketofol in acepromazine- or medetomidine-sedated dogs

OBJECTIVE

A randomized, blinded clinical study was conducted to evaluate ketofol (Ketamine + Propofol combination) anesthesia in 12 entire male mongrel dogs sedated with either acepromazine (ACP) or medetomidine.

MATERIALS AND METHODS

Group A (6) dogs were pre-medicated with ACP and Group B (6) dogs with medetomidine. Anesthesia was induced and maintained using ketofol (ketamine and propofol). Routine open pre-scrotal castration was performed. Sedation score and ease of arousal were assessed and recorded. Duration and depth of anesthesia were evaluated using apnea and the absence of palpebral and pedal reflexes, attempts to stand up, and muscle tremors and post-operative pain. Simple statistics were compared using Student t-test and Mann-Whitney test (p < 0.05).

RESULTS

Medetomidine-sedated dogs had higher sedation scores compared to ACP-sedated dogs. Medetomidine-ketofol produced significantly (p < 0.05) longer duration of anesthesia (24.5 ± 3.1 min) compared to ACP-ketofol (10.0 ± 4.4 min). Sixty-seven percent of dogs anesthetized with ACP-ketofol required top up with ketofol to complete the castration. However, none of the Med-ketofol anesthetized dogs required top up. Med-ketofol produced a more profound depth of anesthesia and smoother recovery from anesthesia compared to ACP-ketofol. Med-ketofol (median score 6) attained better overall post-operative analgesia compared to ACP-ketofol (median score 7), though not statistically significant (p = 0.25). Although both protocols provided adequate anesthesia for castration, top up was required to complete the operation in more than half of ACP-ketofol anesthetized dogs, making Med-ketofol a better protocol.

CONCLUSION

The study recommends the use of Med-ketofol anesthesia for castration in a dog, and post-operative analgesia to be administered with either protocol, but more so in ACP-ketofol anesthetized dogs undergoing castration.