The use of the nondepolarizing neuromuscular blocking drug cis-atracurium in dogs

Objective This clinical trial attempted to evaluate the potency, onset and duration of action of cis‐atracurium in dogs. Animals Twenty dogs aged between 1 and 15 years and weighing between 15 and 85 kg admitted for a variety of elective, surgical procedures under general anaesthesia. Materials and methods Following induction of general anaesthesia, the effects of an intravenous loading dose of cis‐atracurium (0.1 mg kg^?1) were evaluated by counting visual responses to train of four (TOF) nerve stimulation. Incremental doses of 0.02 or 0.04 mg kg^?1 cis‐atracurium were administered when the first of four responses to TOF stimulation was present. Results An initial dose of 0.1 mg kg^?1 eliminated all four TOF responses in 18 out of 20 dogs. The same dose, repeated 10 minutes later in two animals in which blockade was incomplete, abolished all responses. In dogs receiving 0.1 mg kg^?1 cis‐atracurium neuromuscular blockade lasted 27.2 ± 9.3 minutes. Up to six incremental doses were given in individual animals; incremental doses appeared to be noncumulative. No untoward side‐effects were observed with the use of this drug. There was considerable variation between individuals in response to cis‐atracurium. Conclusions Cis‐atracurium is an effective neuromuscular blocking agent in the dog, although its potency varies. Clinical Relevance Further studies are required to determine whether observed differences in potency are related to age, breed or sex. Cis‐atracurium may prove useful in dogs with impaired renal and or hepatic function.     

Use of rocuronium administered by continuous infusion in dogs

OBJECTIVE: A clinical trial to determine whether continuous infusion administration technique was suitable for maintaining neuromuscular blockade with rocuronium bromide in dogs. ANIMALS: Twenty-two dogs, 10 males and 12 females, median age 2 years 4 months, median weight 32 kg undergoing elective surgical procedures under general anaesthesia: ASA classification I or II. MATERIALS AND METHODS: After induction of anaesthesia, neuromuscular function was evaluated using train-of-four (TOF) stimulation of the dorsal buccal branch of the facial nerve. A bolus dose of 0.5 mg kg(-1) rocuronium was administered intravenously and an infusion of 0.2 mg kg(-1) hour(-1) was started immediately. Neuromuscular blockade was assessed visually by counting the number of twitches observed during TOF stimulation repeated at 10-second intervals. RESULTS: The bolus dose of rocuronium abolished the response to TOF stimulation in 21 of the 22 dogs. The median onset time of neuromuscular blockade (complete loss of all four twitches) was 82 seconds (range 38-184 seconds). Median infusion duration was 76 minutes (range 20.3-146 minutes). CONCLUSIONS AND CLINICAL RELEVANCE: This protocol of rocuronium administration was considered to be effective in dogs. Constant infusion of rocuronium is easily applicable to clinical practice and further work is required on infusion titration.     

Effects of sevoflurane,propofol or alfaxalone on neuromuscular blockade produced by a single intravenous bolus of rocuronium in dogs

ObjectiveTo compare the effects of sevoflurane, propofol and alfaxalone on the neuromuscular blockade induced by a single intravenous bolus of rocuronium in dogs.Study designA randomized, prospective, crossover experimental study.AnimalsA total of eight adult Beagle dogs (four female, four male), weighing 8.9–15.3 kg and aged 5–7 years.MethodsThe dogs were anesthetized three times with 1.25× minimum alveolar concentration of sevoflurane (SEVO treatment) and 1.25× minimum infusion rate of propofol (PROP treatment) or alfaxalone (ALFX treatment) at intervals of ≥14 days. Neuromuscular function was monitored with train-of-four (TOF) stimulation of the peroneal nerve by acceleromyography. After recording the control TOF ratio (TOFRC), a single bolus dose of rocuronium (1 mg kg^–1) was administered intravenously. The times from rocuronium administration to achieving TOF count 0 (onset time), from achieving TOF count 0 to the reappearance of TOF count 4 (clinical blockade period), from 25% to 75% of TOFRC (recovery index) and from achieving TOF count 0 to TOF ratio/TOFRC >0.9 (total neuromuscular blockade duration) were recorded.ResultsThe onset time and recovery index did not differ among the treatments. The median clinical blockade period was longer in the SEVO treatment [27.3 (26.0–30.3) minutes] than in PROP [16.6 (15.4–18.0) minutes; p = 0.002] and ALFX [22.4 (18.6–23.1) minutes; p = 0.017] treatments; and longer in the ALFX treatment than in the PROP treatment (p = 0.020). The mean total neuromuscular blockade duration was longer in the SEVO treatment (43.7 ± 9.9 minutes) than in PROP (25.1 ± 2.7 minutes; p < 0.001) and ALFX (32.5 ± 8.4 minutes; p = 0.036) treatments.Conclusions and clinical relevanceCompared with alfaxalone and propofol, sevoflurane prolonged rocuronium-induced neuromuscular blockade by a significantly greater extent in dogs.     

Diabetes mellitus does not affect the neuromuscular blocking action of atracurium in dogs

Objective

To compare the duration of action of atracurium in diabetic and nondiabetic dogs.

A clinical study of the effects of rocuronium in isoflurane-anaesthetized cats

OBJECTIVE: To evaluate the neuromuscular blocking and chronotropic effects of rocuronium bromide in cats anaesthetized for surgery. STUDY DESIGN: Prospective clinical trial. ANIMALS: Twenty-two healthy cats of mixed breed presented for ovariectomy (n = 13) or castration (n = 9). Mean body mass (+/-SD) was 3.6 +/- 0.65 kg and mean age was 10.25 +/- 2.63 months. METHODS: Anaesthesia was induced with intravenous (IV) midazolam (0.3 mg kg(-1)), ketamine (3 mg kg(-1)) and butorphanol (0.4 mg kg(-1)). Tracheal intubation was performed and anaesthesia was maintained with isoflurane delivered in 100% oxygen. Neuromuscular function was monitored using acceleromyography applied at the ulnar nerve. This was stimulated by using the train-of-four (TOF) stimulus pattern (2 Hz) delivered every 15 seconds. The first train was made to establish baseline values for the first twitch (T1) and the TOF-ratio (T4:T1). Rocuronium (0.6 mg kg(-1) IV) was given and the following periods were recorded beginning at the end of injection: (1) lag time (LT) - to the first signs of T1 depression; (2) onset time (OT) - to the total ablation of T1; (3) duration of action (T1(25)) - to 25% recovery of the baseline value for T1; (4) T1(50)- to 50% baseline T1 restoration; (5) to TOF-ratios of 0.7 and 0.9. The time taken for T1 to recover from 75% to 25% depression (T1(25-75)) was also recorded. Heart rate (HR) was taken every minute for 15 minutes, beginning 5 minutes before rocuronium was injected. RESULTS: Rocuronium (0.6 mg kg(-1)) had a mean LT of 15.0 +/- 0 seconds, OT of 46 +/- 11 seconds and T1(25) of 13.2 +/- 2.7 minutes. The mean time for TOF 0.7 and 0.9 was 17.3 +/- 5.4 and 20.7 +/- 5.4 minutes respectively. The mean T1(25-75) was 4.8 +/- 2.4 minutes. No significant changes in HR were observed at any of the time intervals recorded. CONCLUSION: Rocuronium is an effective nondepolarizing muscle relaxant in the cat under the clinical conditions of this study. It has a rapid onset, a short duration of action and did not cause significant changes in HR.     

Comparison of the neuromuscular blocking effects of cisatracurium during isoflurane or propofol anesthesia in dogs

ObjectiveTo compare the neuromuscular blocking effects of cisatracurium during isoflurane versus propofol anesthesia in dogs.Study designProspective, randomized study.AnimalsA total of 20 healthy, client-owned dogs (16 females, four males) weighing 12.5–22 kg and aged 1–8 years.MethodsDogs undergoing elective surgery were randomized in equal numbers to an isoflurane (ISO) or propofol (PPF) group. Other drugs used during anesthesia were equal between groups. Single-twitch (ST) stimulation was used to monitor neuromuscular response. After recording the baseline ST (T0), cumulative doses of cisatracurium (0.05 mg kg^–1) were administered intravenously until ST/T0 ≤5%. Effective doses 50 (ED₅₀) and 95 (ED₉₅) of cisatracurium in each group were calculated from group dose-response curves. Recovery of ST (TR) was defined as spontaneous recovery of ST to 80–120% of T0 remaining stable for 2 minutes. The ST after each dose of cisatracurium, duration 25% (time after the last dose until 25% recovery of TR), recovery index (time to recovery from 25% to 75% of TR) and duration to TR (time after the last dose until recovery of TR) were recorded.ResultsIncremental doses of cisatracurium, median (range), were 2 (1–3) in ISO and 4 (2–5) in PPF to achieve ≥95% depression of ST/T0 (p < 0.01). ED₅₀ and ED₉₅ were 20 μg kg^–1 and 117 μg kg^–1 in ISO and 128 μg kg^–1 and 167 μg kg^–1 in PPF, respectively. The duration 25%, recovery index and duration to TR, median (range), were longer in ISO [22.6 (10.3–24.3), 5.3 (3.0–7.8) and 36.1 (20.1–49.7) minutes, respectively] than in PPF [10.2 (6.8–16.5), 3.0 (2.0–3.8) and 17.7 (14.2–28.7) minutes, respectively] (p < 0.01).Conclusions and clinical relevanceCisatracurium-induced neuromuscular blockade was significantly enhanced and prolonged by isoflurane compared with propofol.     

Rocuronium infusion: A higher rate is needed in diabetic than nondiabetic dogs

Objective

To determine the infusion rates that maintain the train-of-four (TOF) ratio within 20–70% in dogs and compare the infusion rates between diabetic and nondiabetic dogs.

cis-Atracurium in dogs with and without porto-systemic shunts

OBJECTIVE: To evaluate the non-depolarizing neuromuscular blocking drug cis-atracurium in dogs with porto-systemic shunts, and to compare it in clinically normal animals. ANIMALS: Thirteen dogs of mixed breed and sex, aged between 3 and 31 months old, weighing 2.2-25.5 kg, with ASA physical status II-IV, and undergoing surgical attenuation of porto-systemic shunt. A control group of 11 bitches of mixed breed, between 8 and 60 months old, and weighing 4.5-41.0 kg, all ASA physical status I, undergoing routine ovarohysterectomy were also studied. MATERIALS AND METHODS: Pre-anaesthetic medication was an opioid analgesic, given either alone or in combination with acepromazine. Following induction of general anaesthesia with intravenous (IV) propofol and oro-tracheal intubation, anaesthesia was maintained using isoflurane in either oxygen or oxygen and nitrous oxide. Ventilation was controlled. The train of four (TOF) technique was used to monitor neuromuscular blockade. An initial dose of 0.1 mg kg(-1)cis-atracurium was given IV and additional doses of 0.03 mg kg(-1)cis-atracurium were administered when at least one twitch of the TOF was present. RESULTS: Except for one dog that was killed during surgery because its anomaly was inoperable, all animals recovered satisfactorily from anaesthesia and surgery. In dogs with porto-systemic shunt, onset of neuromuscular blockade was 3.1 +/- 1.1 minutes (mean +/- SD) and in control dogs was 3.4 +/- 0.7 minutes (not significantly different). Neuromuscular blockade lasted 34 +/- 13 minutes in dogs with porto-systemic shunt and 29 +/- 17 minutes in control dogs (not significantly different). CONCLUSIONS: The presence of porto-systemic shunt did not affect the rate of onset or duration of action of cis-atracurium. CLINICAL RELEVANCE: cis-Atracurium may have a use in veterinary anaesthesia for producing neuromuscular blockade in dogs with hepatic insufficiency, including those with porto-systemic shunt.     

Recovery from neuromuscular block in dogs: restoration of spontaneous ventilation does not exclude residual blockade

ObjectiveTo evaluate if return of spontaneous ventilation to pre-relaxation values indicates complete recovery from neuromuscular blockade.Study designProspective, with each individual acting as its own control.AnimalsTen healthy adult female Beagle dogs weighing 6.2–9.4 kg.MethodsDogs were anesthetized with propofol, dexemedetomidine and isoflurane. Spontaneous ventilation was assessed by measuring end-tidal CO₂, expired tidal volume, peak inspiratory flow, respiratory rate and minute ventilation. Vecuronium 25 μg kg^?1 IV was administered and neuromuscular block was evaluated by measuring the train-of-four (TOF) ratio with acceleromyography in the hind limb. During spontaneous recovery from neuromuscular block, the TOF ratio when each ventilatory variable returned to baseline was recorded.ResultsThis dose of vecuronium produced moderate neuromuscular block in all dogs, with TOF ratio values of 0–18% at maximal block. Expired tidal volume, peak inspiratory flow and minute ventilation returned to pre-relaxation values when the median TOF ratio was ≤ 20%. The median TOF ratio was 42% when the end-tidal CO₂ returned to pre-relaxation values.Conclusions and clinical relevanceSignificant residual neuromuscular block could be measured at the hind limb with acceleromyography when ventilation had spontaneously returned to pre-vecuronium values. Monitoring spontaneous ventilation, including end-tidal CO₂, expired tidal volume, peak inspiratory flow or minute ventilation cannot be used as a surrogate for objective neuromuscular monitoring, and this practice may increase the risk of postoperative residual paralysis.     

Twitch potentiation: a potential source of error during neuromuscular monitoring with acceleromyography in anesthetized dogs

ObjectiveTo measure twitch potentiation (the staircase phenomenon) in anesthetized dogs, and assess its relevance during neuromuscular monitoring with acceleromyography (AMG).Study designRandomized, prospective clinical trial.AnimalsSixteen dogs undergoing ovariohysterectomy.MethodsUnder isoflurane anesthesia, neuromuscular function was monitored with train-of-four (TOF) stimuli every 15 seconds and quantified by AMG. Neuromuscular blockade (NMB) was produced with 0.15 mg kg^?1 atracurium IV. Dogs were randomly divided into two groups; a potentiation group (PG) in which TOF stimulation was applied for 20 minutes before atracurium was administered; and a control group (CG) where no such time was allowed. In both groups, the AMG was calibrated (at tCAL) just before atracurium was administered. TOF stimulation continued throughout the experiment in all dogs. The height of the first twitch (T₁) (expressed as a fraction of T₁ at tCAL) and train-of-four ratio (TOFR) were recorded until TOFR returned to ≥90%.ResultsIn PG, T₁ increased significantly (p = 0.0078) from a median of 102% (range, 95, 109) at baseline to 118% (100, 142) at 20 minutes. In PG, no difference was found between T₁ at tCAL (immediately before atracurium administration) and T₁ when neuromuscular transmission returned (p = 0.42). In the CG, T₁ increased significantly between tCAL and the time neuromuscular transmission returned (p = 0.027). TOFR did not increase during twitch potentiation (all p = 0.32).Conclusions and clinical relevanceT₁ increased significantly during 20 minutes of uninterrupted TOF stimulation in the absence of NMB, establishing that twitch potentiation occurs in anesthetized dogs. With no time for potentiation, T₁ increased during the course of recovery from NMB; this phenomenon introduces a bias in T₁ measurements and could affect studies reporting potency and duration of NMB based on T₁ or single twitches. TOFR was unaltered by potentiation emphasizing its clinical usefulness for excluding post-operative residual NMB.     

Neuromuscular blockade with rocuronium bromide for ophthalmic surgery in horses

Purpose The production of a central eye to ease surgical access for intraocular surgery is generally dependent on the depth of anesthesia. The aim of this study was to evaluate the eyeball position under muscle relaxation with rocuronium during general anesthesia. Material and methods Twenty horses, body weight 480 ± 62 kg; age 12.6 ± 6.2 years (mean ± SD) were anesthetised for various ophthalmic surgeries. Horses were premedicated with acepromazine, xylazine, and butorphanol intravenously and anesthesia induced with ketamine and diazepam. Anesthesia was maintained with isoflurane in 100% oxygen and 0.6 mL/kg/h of an infusion containing midazolam, ketamine, and xylazine diluted in 500 mL 0.9% NaCl. Horses were mechanically ventilated. Neuromuscular function was assessed with an acceleromyograph (TOF‐Guard^®) and the N. peroneus superficialis was stimulated every 15 s with a train‐of‐four stimulation pattern. A dose of 0.3 mg/kg rocuronium was administered intravenously. The changes in the eyeball position were recorded. Results The dose of 0.3 mg/kg rocuronium produced a 100% neuromuscular block in all horses. Onset time and clinical duration of block was 2.38 ± 2.02 min (range 0.5–8) and 32 ± 18.6 min (range 7.7–76.2), respectively. The globe rotated to central position within 31 ± 2.8 s. The whole iris was visible after 42 ± 7.7 s in all horses. No additional bolus of rocuronium was necessary for any surgery. Conclusion Neuromuscular blockade with rocuronium bromide can be used safely to facilitate ophthalmic surgery in equines.     

The effect of low dose rocuronium on globe position, muscle relaxation and ventilation in dogs: a clinical study

OBJECTIVE: The purpose of this study was to evaluate globe position, muscle relaxation and changes in ventilatory parameters after intravenous administration of 0.1 mg/kg rocuronium. STUDY DESIGN: Prospective clinical study. ANIMAL STUDIED: Sixteen dogs of different breeds, with a body weight of 22.1 +/- 13 kg and age of 5.6 +/- 2.8 years (mean +/- SD), were anesthetized for a short ophthalmic examination requiring central position of the globe. PROCEDURES: All dogs were premedicated with 0.005 mg/kg medetomidine and 0.1 mg/kg methadone IV. Anesthesia was induced with propofol to effect and maintained with 10 mg/kg/h propofol by continuous rate infusion. Following endotracheal intubation all dogs breathed 100% oxygen via an anesthetic circle system. Neuromuscular function was assessed with an acceleromyograph (TOF-Guard, Organon Teknika NV, Turnhout, Belgium) and by stimulation of the nervus peroneus superficialis. The ventilation parameters were measured using spirometry and capnography. After baseline measurements 0.1 mg/kg rocuronium was administered IV. Minute volume (MV), tidal volume (Vt), respiratory rate (RR), end expiratory carbon dioxide concentration (PE'CO(2)) and maximal depression of the response of the first twitch (T1) of train-of-four (TOF) stimulation and train-of-four ratio (TOFR) was measured. The change in the position of the globe was recorded. RESULTS: T1 decreased to 61 +/- 18% and the TOF ratio to 45 +/- 21% of baseline values. Both parameters returned to baseline after 9 min. There was no significant reduction in MV, TV and RR and no increase in PE'CO(2). The globe rotated to a central position of 45 +/- 7.7 s after administration of rocuronium and remained there for 23 +/- 10.8 min in all dogs. CONCLUSION: Rocuronium administered intravenously at a dose of 0.1 mg/kg to dogs causes a central position of the globe but minimal impairment of ventilation parameters.     

Use of cis-atracurium to maintain moderate neuromuscular blockade in experimental pigs

Objective

To determine the dose of cis-atracurium needed to produce a moderate neuromuscular blockade (NMB) in pigs.

Use of neuromuscular blockade with rocuronium bromide for intubation in cats

ObjectiveTo determine whether neuromuscular blockade with rocuronium bromide (RB) would improve endotracheal intubation (EI) conditions in comparison with topical lidocaine hydrochloride (LH).Study designRandomized prospective study.AnimalsForty seven healthy cats of unspecified breed, aged 17 ± 11 months and weighing 2.8 ± 0.8 kg, undergoing elective procedures.MethodsAnesthesia was induced with xylazine (XZ) (1.1 mg kg^?1 IM) and tiletamine‐zolazepam (XTZ) (7 mg kg^?1 IM) and EI was attempted. Cats which could not be intubated at the first attempt (n = 34), were randomly medicated with either 0.1 mL LH 10% spray on the laryngeal mucosa (n = 17) or 0.6 mg kg^?1 intravenous RB (n = 17). Sixty seconds later, a second attempt at EI was performed. The effect of both drugs was assessed using a previously published scale (Sandor Agoston). EI conditions associated with laryngoscopy, vocal cord position and movement, cough, patient movement, time and attempts needed in order to perform EI were recorded. Heart rate and end‐expired CO₂ concentration were monitored.ResultsGroups were comparable in age, weight, gender and hematological parameters. Clinically acceptable EI conditions were not significantly different between RB and LH assisted groups (p = 0.31). However, there was a significant difference in cough, vocal cord movement and position between the RB and the LH groups. The group intubated at the first attempt and receiving neither RB nor LH coughed persistently (11/13). The cats receiving RB had to be ventilated for 10–28 minutes.Conclusions and clinical relevanceThe present study shows that, when used in cats anesthetized with XTZ, RB paralyzes the internal laryngeal muscles keeping the vocal cords in an intermediate position (paramedial) 60 seconds after being administered. RB is an effective alternative to LH to overcome the airway protective reflexes when performing EI but requires ventilatory support until the paralysis wears off.     

The post-tetanic count during vecuronium-induced neuromuscular blockade in halothane-anaesthetized dogs

ObjectiveTo evaluate the post‐tetanic count (PTC) for predicting the return of reversible neuromuscular blockade at the n. facialis–m. nasolabialis (nF–mNL) and n. ulnaris–mm. carpi flexorii (nU–mCF) nerve‐muscle units (NMUs) during profound vecuronium neuromuscular blockade in halothane‐anaesthetized dogs.Study designRandomized, prospective, experimental study.AnimalsTwenty‐five dogs (seven male 18 female) undergoing surgery; mean age: 4.8 years; mean body weight 22 kg.MethodsThirty minutes after acepromazine (0.05 mg kg^?1) and morphine (0.5 mg kg^?1) pre‐medication, anaesthesia was induced with intravenous (IV) thiopental and maintained with halothane, N₂O and O₂. The lungs were mechanically ventilated and end‐tidal halothane concentration (Fe′_HAL) maintained at 1.04%. Neuromuscular transmission was monitored using the train‐of‐four count (TOFC) at one nF–mNL and both nU–mCF units. Vecuronium (50 µg kg^?1 IV) was injected after 15 minutes constant Fe′_HAL. When the first twitch (T1) at both nU–mCF units had disappeared (t = 0) one (randomly allocated) ulnar nerve was stimulated every 5 minutes using PTC; TOF stimulation continued at the other sites. The PTC was plotted against the interval between recording time and T1's reappearance at the other NMUs.ResultsAt t = 0, the mean PTC in the contralateral nU–mCF unit was 18 (range 0–20). Mean PTC was a minimum at t = 5, rising to the maximum (20) at 25 minutes. Six dogs were vecuronium‐resistant as monitored by PTC. Excluding data from these revealed a strong negative relationship between ulnar PTC and the time taken for T1's return at the facial (r = ?0.7018; p < 0.00001) and contralateral ulnar (r = ?0.8409; p < 0.00001) NMUs.Conclusion and clinical relevancePost‐tetanic count monitoring beginning >5 minutes after the TOFC at nU–mCF = 0 provided a reliable estimate of T1's return at ulnar and facial NMUs.     

The effects of medetomidine on the action of vecuronium in dogs anaesthetized with halothane and nitrous oxide

ObjectiveTo quantify the effects of medetomidine on the onset and duration of vecuronium-induced neuromuscular blockade in dogs.Study designRandomized, prospective clinical study.AnimalsTwenty-four, healthy, client-owned dogs of different breeds, aged between 6 months and 10 years and weighing between 5.0 and 40.0 kg undergoing elective surgery.MethodsDogs were randomly allocated to two groups. Pre-anaesthetic medication in group M+ was intramuscular acepromazine (ACP) 25 μg kg⁻¹, morphine 0.5 mg kg⁻¹ and medetomidine 5 μg kg⁻¹. Group M− received ACP and morphine only, at the same dose rate. After induction with thiopental, anaesthesia was maintained with halothane in oxygen and nitrous oxide. End-tidal halothane concentration was maintained at 1.1%. Neuromuscular blockade was produced with intravenous vecuronium (50 μg kg⁻¹) and monitored using a train of four stimulus applied at the ulnar nerve. The times taken for loss and reappearance of the four evoked responses (twitches [T]) were recorded. Normal and nonparametric data were analysed with an independent t-test and Mann-Whitney's U-test, respectively.ResultsThe fourth twitch (T4) disappeared at similar times in each group: 107 ± 19; [72–132] (mean ± SD; [range]) seconds in M+ and 98 ± 17 [72–120] seconds in M− dogs. The first twitch (T1) was lost at 116 ± 15; [96–132] seconds in group M+ and 109 ± 19; [72–132] seconds in M−. The fourth twitch returned significantly earlier in M+ dogs: 20.8 ± 3.8 [14–28] minutes compared with 23.8 ± 2.7 [20–27] minutes (p = 0.032). The duration of drug effect (T4 absent) was significantly shorter (p = 0.027) in M+ (18.9 ± 3.7 minutes) compared with M− dogs (22.2 ± 2.9 minutes). The recovery rate (interval between reappearance of T1 and T4) was significantly more rapid (p = 0.0003) in medetomidine recipients (3.0 ± 1.2 versus 5.2 ± 1.3 minutes).Conclusion and clinical relevance Medetomidine 5 μg kg⁻¹ as pre-anaesthetic medication shortened the duration of effect of vecuronium in halothane-anaesthetized dogs and accelerated recovery, but did not affect the onset time. These changes are of limited clinical significance.     

Diabetes mellitus affects the duration of action of vecuronium in dogs

ObjectiveTo compare the duration of action of vecuronium in diabetic dogs with a control group.Study designProspective clinical study.AnimalsForty client-owned diabetic (n = 20) and non-diabetic dogs.MethodsDogs were considered free from other concurrent disease based on clinical examination and laboratory data. After pre-anaesthetic medication with acepromazine and methadone, anaesthesia was induced with intravenous (IV) propofol and maintained with isoflurane-nitrous oxide in oxygen. Neuromuscular blockade (NMB) was achieved with vecuronium, 0.1 mg kg^?1 IV and its effects recorded by palpation (pelvic limb digital extension) and electromyography (m. tibialis cranialis) of responses (twitches; T) to repeated train-of-four (TOF) nerve stimulation. Time to onset of NMB was the period between vecuronium injection and loss of fourth twitch (T4) in the TOF pattern recorded by EMG and palpation. Duration of NMB was defined as the time from drug administration to return of T1 by palpation (T1_tactile) and EMG (T1_EMG). Times to return of T2-4 were also recorded. Time from induction of anaesthesia to vecuronium injection was recorded. Heart rate, non-invasive mean arterial pressure, body temperature, end-tidal isoflurane and end-tidal CO₂ concentrations were recorded at onset of NMB and when T1_EMG returned. Loss and return of palpable and EMG responses for diabetic and non-diabetic dogs were compared using t-tests and Mann Whitney U-tests.ResultsThere were significant (p < 0.05) differences between diabetic and non-diabetic dogs for the return of all four palpable and EMG responses. Times (mean ± SD) for return of T1_tactile were 13.2 ± 3.5 and 16.9 ± 4.2 minutes in diabetic and non-diabetic dogs respectively. There were no differences between diabetic and non-diabetic dogs in the time to onset of vecuronium with EMG or tactile monitoring.Conclusions and clinical relevanceThe duration of action of vecuronium was shorter in diabetic dogs as indicated by both tactile and EMG monitoring.     

Efficacy of topical rocuronium bromide as a mydriatic agent in domestic pigeons (Columba livia)

This study was conducted to investigate the efficacy of rocuronium bromide as mydriatic agent in domestic pigeons (Columba livia). This study was done in two phases. In the first phase, rocuronium bromide (0.20 mg/20 µl) was topically instilled to the right eye (OD) of eight domestic pigeons. Pupil diameter was measured before instillation (T0), and at 5 (T05) and 10 (T10) min after instillation, and every 10 min thereafter until 160 (T160) min. Pupillary light reflex (PLR) was assessed using a scoring system at the same time points. In the second phase, the same dosage was instilled twice in the span of 10 min into both eyes (OU) of four pigeons (eight eyes). Measurements were done accordingly. The iris color in the first phase were: gravel, pearl and bull eye. All irises in the second phase were bull eye. Mydriasis were observed in 6/8 (75%) pigeons in the first phase. Maximal mydriasis was observed at T30 (mean pupil diameter=4.62 ± 0.13 mm). Pupil diameter in the treated eye was significantly different from contralateral eye and from T0 since T05 (P=0.017 and P=0.006, respectively)−T120 (P=0.043 and P=0.044, respectively). PLR was disappeared from T10 (P=0.034) to T90 (P=0.041). In the second phase, mydriasis was only observed in 2/8 eyes. This study suggested that rocuronium bromide was able to produce mydriasis in pigeons other than bull eye iris.     

Evaluation of a three-axial acceleromyography monitor in dogs compared with mechanomyography

ObjectiveTo compare the ratio of the train-of-four (TOF) and double burst stimulation (DBS) obtained with three-axial acceleromyography (AMG) and mechanomyography (MMG) in dogs during recovery from a rocuronium-induced neuromuscular block.Study designProspective, randomized, experimental study.AnimalsA total of six intact healthy adult male Beagle dogs, weighing 9.1 ± 1.9 kg and aged 3–5 years.MethodsDogs were anesthetized with intravenous (IV) dexmedetomidine and propofol, and isoflurane in oxygen. Neuromuscular function was measured with AMG and MMG in the contralateral thoracic limbs. Rocuronium (0.5 mg kg^–1) was administered IV, and the TOF and DBS ratios measured. During neuromuscular block offset, MMG values were recorded when AMG first reached ratios of 0.9 and 1.0. True recovery from neuromuscular block was determined as MMG ratio ≥ 0.9. The false-positive (AMG ≥ 0.9 or 1.0, and MMG ratio < 0.9) rate was determined. Paired values were compared, and bias and limits of agreement were calculated. Receiver operating characteristic (ROC) curves were created.ResultsWhen AMG first reached 0.9 and 1.0 during recovery, MMG values were lower (p < 0.040). When AMG reached 0.9, the false-positive rate was 29% with TOF and 27% with DBS. It decreased to 12% (TOF) and 11% (DBS) when a ratio of 1.0 was used. AMG values were higher than paired MMG values (p < 0.001). The AMG overestimated MMG by 24% and 22% for TOF and DBS, respectively. Areas under the ROC curves (95% confidence interval) were 0.91 (0.89, 0.94) and 0.86 (0.81, 0.94) for TOF and DBS, respectively.Conclusionsand clinical relevance The three-axial AMG monitor overestimated neuromuscular function and, in some cases, indicated adequate recovery despite the MMG ratio being < 0.9. A TOF or DBS ratio of at least 1.0 should be considered when monitoring recovery of neuromuscular block with this AMG device.