Onset and duration of action of escalating doses of atracurium in anesthetized healthy goats.

OBJECTIVE: The aim of this study was to describe the onset and duration of action of escalating doses of atracurium in healthy, anesthetized goats. STUDY DESIGN: Randomized, blinded, triple crossover study. Animals A total of eight (five males and three females) healthy goats weighing 42.7-123.5 kg and aged from 11 months to 8 years. METHODS: Goats were anesthetized three times with propofol and anesthesia was maintained with isoflurane. One of three doses of atracurium was administered intravenously 30 minutes after induction: 0.25 mg kg-1 (AT25), 0.5 mg kg-1 (AT50) or 0.75 mg kg-1 (AT75). Acceleromyographic train-of-four ratio (TOFR) followed by train-of-four counts (TOFC) were recorded at 30 second intervals after atracurium administration to determine blockade onset (TOFC = 0). The TOFR followed by TOFC were recorded at 5 minute intervals until return to pre-atracurium baseline (TOFR = 1.0). Normally distributed data were analyzed with repeated measures anova and a Tukey multiple comparison test. Data not normally distributed were analyzed with a Friedman test and a Dunn's multiple comparison test. RESULTS: For AT50 and AT75, 100% of goats achieved TOFC = 0 after atracurium administration. For AT25, however, 87.5% of goats achieved TOFC = 0 after atracurium administration. The onset time was shorter for AT75 [1.5 (0.5-1.5) minutes; median (range)] than for AT25 [2 (1-4) minutes] (p = 0.048). The duration of action [from onset time to complete reversal (TOFR = 1.0)] was significantly shorter for AT25 (52 ± 12 minutes, mean ± SD) than for AT50 (77 ± 18 minutes) (p < 0.001) and AT75 (85 ± 16 minutes) (p < 0.001). There was no significant difference in duration between AT50 and AT75 (p = 0.238). CONCLUSIONS AND CLINICAL RELEVANCE: Doses of 0.5 and 0.75 mg kg-1 atracurium may produce complete neuromuscular blockade in healthy, anesthetized goats.

Sugammadex for reversal of moderate-to-deep rocuronium block in a clinical setting: A retrospective report of 10 dogs.

OBJECTIVE: To compare recovery times of sugammadex with spontaneous recovery from rocuronium-induced neuromuscular block (NMB) in dogs. STUDY DESIGN: Retrospective, unmatchedcase-control study. ANIMALS: A total of 10 dogs administered sugammadex and 10 dogs recovering spontaneously from rocuronium-induced NMB. METHODS: Files of dogs administered rocuronium between March and August 2023 were inspected. The train-of-four (TOF) count at the time of sugammadex administration and the time between administration and TOF ratio >90% (recovery time) were recorded. The recovery time for those not administered reversal agents was considered from the first TOF value >0 until TOF ratio >90%. The dose of sugammadex and the cumulative dose of rocuronium were recorded. Rocuronium doses and recovery times were compared using Mann-Whitney tests. The coefficient of determination (R2) between the cumulative rocuronium dose and sugammadex dose and the recovery time were calculated. RESULTS: Dogs in the sugammadex and spontaneous recovery groups were administered intravenously (IV) 0.76 (0.4-2.6) and 0.61 (0.3-2.9) mg kg-1 of rocuronium, respectively (p = 0.325). Recovery time after 3.9 (2.9-5.5) mg kg-1 of sugammadex IV was 1 (1-3) minutes and was 20 (10-35) min for spontaneous recovery (p < 0.0001). The R2 for rocuronium and sugammadex doses and recovery times were 0.19 (p = 0.2) and 0.012 (p = 0.758). CONCLUSIONS AND CLINICAL RELEVANCE: Sugammadex 2.9-5.5 mg kg-1 reversed moderate (TOF count 1-3) or deep (TOF count 0) rocuronium-induced NMB within 3 minutes, substantially faster than spontaneous recovery.

Sugammadex for reversal of rocuronium-induced neuromuscular blockade during alfaxalone anesthesia in dogs.

OBJECTIVE: To investigate the reversal effect of sugammadex on neuromuscular blockade induced by a single bolus of rocuronium in dogs under alfaxalone anesthesia. STUDY DESIGN: Randomized, prospective, crossover experimental study. ANIMALS: A group of six adult Beagle dogs (three females and three males), weighing 11.3-15.8 kg and aged 6-8 years, were used. METHODS: Dogs were anesthetized twice with a 1.25 times minimum infusion rate of alfaxalone, with a washout period of at least 14 days between experiments. Neuromuscular function was monitored using acceleromyography with train-of-four (TOF) stimulation of the peroneal nerve. After recording the control TOF ratio (TOFRC), rocuronium (0.5 mg kg-1) was administered intravenously. Subsequently, sugammadex (4 mg kg-1) or an equal volume of saline (control treatment) was administered intravenously when the TOF count returned from 0 to 1 after neuromuscular blockade. Time from rocuronium injection to TOF count = 0 (onset time), time from TOF count = 0 to TOF count = 1 (maximum blockade period), time of first twitch amplitude recovery from 0.25 to 0.75 (recovery index), and time from sugammadex or saline administration to TOF ratio/TOFRC ≥ 0.9 (recovery time) were recorded. RESULTS: The onset time and maximum blockade duration did not differ between sugammadex treatment [1.2 (0.7-1.5) minutes and 9.9 (6.3-10.5) minutes, respectively] and control treatment [median (range); 1.0 (0.7-1.1) minutes and 9.9 (8.8-11.5) minutes, respectively] (p = 0.219 and 0.844, respectively). Recovery index was 0.5 (0.3-0.7) minutes in sugammadex treatment, which was shorter than that in control treatment [4.5 (3.7-4.9) minutes] (p = 0.031). Recovery time was 0.8 (0.5-2.8) minutes in sugammadex treatment, which was shorter than that in control treatment [10.5 (6.8-14.3) minutes] (p = 0.031). CONCLUSIONS AND CLINICAL RELEVANCE: Rocuronium-induced neuromuscular blockade was effectively reversed by sugammadex in dogs anesthetized with alfaxalone.

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

OBJECTIVE: To 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 DESIGN: Prospective, randomized, experimental study. ANIMALS: A total of six intact healthy adult male Beagle dogs, weighing 9.1 ± 1.9 kg and aged 3-5 years. METHODS: Dogs 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. RESULTS: When 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. CONCLUSIONS: and 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.

Generalised neuromuscular blockade after intraurethral administration of atracurium besilate in a male cat with urethral obstruction.

A 4-year-old, entire, male, domestic long-haired cat was presented with an acute history of stranguria and dysuria and diagnosed with urolithiasis causing urethral obstruction. The patient was induced to general anaesthesia and several unsuccessful attempts to flush the uroliths retrogradely towards the bladder were made. An intraurethral administration of the neuromuscular blocking agent atracurium was performed as it has been reported to facilitate urethral catheterisation without any side effects. Respiratory arrest developed after 15 minutes from atracurium administration, which was promptly recognized and treated with mechanical ventilation. The absence of muscle contraction in response to a nerve stimulation confirmed a generalised muscle blockade. Approximately 35 minutes after, a muscle response to nerve stimulation appeared. Neostigmine combined with glycopyrrolate was administered resulting in complete recovery from neuromuscular blockade. In conclusion, the use of intraurethral atracurium can result in systemic absorption of the drug with subsequent generalised neuromuscular blockade.

Rocuronium-neuromuscular blockade does not influence the patient state index in anesthetized dogs.

OBJECTIVE: To evaluate the effects of rocuronium and sugammadex on the patient state index (PSI) in dogs anesthetized with propofol. ANIMALS: 6 intact healthy male Beagles. PROCEDURES: Anesthesia was induced with and maintained on a propofol infusion. The estimated plasma propofol concentration (ePC) was recorded. Baseline PSI and train-of-four ratio (TOFR) readings were collected for 2 minutes in stable general anesthesia. Neuromuscular blockade (NMB) was induced with 0.6 mg/kg, IV, rocuronium, and full NMB was confirmed with a TOFR of 0. After 5 minutes, the neuromuscular function was restored with 4 mg/kg sugammadex, IV (reversal), and monitored for 5 minutes. Throughout the data collection, ePC, PSI, and TOFR were recorded every 15 seconds and compared with mixed-effect ANOVA. RESULTS: Baseline ePC, PSI, and TOFR were 3.63 ± 0.38, 41 ± 6, and 0.97 ± 0.08 µg/mL, respectively. There was no difference between the baseline of ePC and PSI from NMB or reversal. Compared to the baseline, the TOFR decreased to 0 with NMB (P < .001) and returned to 0.96 ± 0.08 (P = .721) on reversal. After 5 minutes, sugammadex fully reversed 5 out of 6 dogs to TOFR > 0.90 and partially reversed 1 animal to TOFR = 0.80. CLINICAL RELEVANCE: There was no evidence that NMB with rocuronium and sugammadex-induced reversal interfered with PSI readings under steady-state total intravenous anesthesia with propofol. Further evaluation of PSI is warranted to assess its utility in a clinical population to detect changes in levels of consciousness during NMB.

ED50 and ED95 of rocuronium during alfaxalone anesthesia in dogs.

OBJECTIVE: To determine the median effective dose (ED50) and effective dose required to depress the twitch value by 95% (ED95) of rocuronium during alfaxalone anesthesia in dogs. STUDY DESIGN: A randomized, prospective, crossover experimental study. ANIMALS: A total of eight adult Beagle dogs (four female, four male), weighing 10.3-14.6 kg and aged 6-8 years. METHODS: The dogs were anesthetized three times with 1.25-fold the individual minimum infusion rate of alfaxalone 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) and first twitch of TOF (T1C), a single bolus dose of rocuronium 100, 175 or 250 µg kg-1 (treatments R100, R175 or R250) was administered intravenously. The maximum suppression of the first twitch of TOF (T1) was recorded and calibrated with T1C to construct the dose-response curve, from which ED50 and ED95 were calculated. Time from rocuronium administration to TOF ratio/TOFRC > 0.9 (duration TOFR0.9) was recorded. RESULTS: ED50 and ED95 of rocuronium during alfaxalone anesthesia were 175 and 232 µg kg-1, respectively. The median (range) duration TOFR0.9 was longer in treatment R250 [10.1 (9.2-10.9) minutes] than in treatments R100 [3.1 (2.9-4.4) minutes; p < 0.0001] and R175 [7.7 (6.9-8.1) minutes; p < 0.0001]; and longer in treatment R175 than in treatment R100 (p < 0.0001). CONCLUSIONS AND CLINICAL RELEVANCE: The duration of TOFR0.9 correlated positively with the dosage of rocuronium, indicating that recovery time of rocuronium was also dose-dependent in dogs anesthetized with alfaxalone. The duration TOFR0.9 of rocuronium 250 µg kg-1 was 10 minutes during alfaxalone anesthesia in dogs.

Duration of neuromuscular block is more variable and recovery time is shorter with rocuronium than cisatracurium in anesthetized dogs.

OBJECTIVE: To compare the variability in the duration of action of a single dose of rocuronium or cisatracurium, and duration of subsequent top-up doses in anesthetized dogs. ANIMALS: Thirty dogs requiring ophthalmic surgery with neuromuscular block. PROCEDURES: Neuromuscular function was monitored with train-of-four (TOF) and acceleromyography. Dogs received an initial dose of rocuronium 0.6 mg/kg, or cisatracurium 0.15 mg/kg IV, which produced complete neuromuscular block. Upon return of the first response (T1) of TOF, a third of the initial dose was repeated. The duration of the initial dose and its variability were compared between agents. Duration of subsequent top-up doses was assessed with mixed effect models. Spontaneous (from last return of T1) or neostigmine-enhanced (from administration to complete recovery) recovery times were measured for each agent. RESULTS: Duration of action of the initial dose was [median (range)] 25 (10-60) min with rocuronium and 35 (15-45) min with cisatracurium (p = .231). The variability of rocuronium was 3.25 times larger than cisatracurium (p = .034). Duration of top-up doses did not vary for either agent. Spontaneous recovery was shorter for rocuronium [15 (10-20) min] than cisatracurium [25 (15-45) min] (p = .02). Neostigmine-enhanced recovery times were 5 (5-25) for rocuronium and 10 (5-10) for cisatracurium (p = .491). CONCLUSIONS: Duration of action for a single dose is significantly more variable with rocuronium than cisatracurium. Time to spontaneous recovery was longer for cisatracurium, and cases of unexpectedly long recovery times were observed with both agents. Objective monitoring is recommended.

Comparison of the neuromuscular effects of two infusion rates of rocuronium in anesthetized pigs.

BACKGROUND: Neuromuscular blocking agents are frequently administered to pigs used for research. In humans, administration of the drugs is not without risk and may result in accidental awareness under general anaesthesia and postoperative residual neuromuscular blockade that can lead to serious respiratory complications. Despite the extensive administration, the pharmacodynamics of neuromuscular blocking agents are not thoroughly studied in pigs. Therefore, this study investigates the neuromuscular response of two infusion rates of rocuronium, a commonly used non-depolarizing neuromuscular blocking agent. A group of 14 female Danish Landrace-Yorkshire-Duroc pigs used for supervised surgical training, weighing 40.3 ± 2.1 kg (mean ± SD), were included in the study. They received a loading dose of 0.85 mg/kg rocuronium intravenously followed by infusion of either 2.5 mg/kg/hour (L, low dose) or 5 mg/kg/hour (H, high dose) rocuronium for 30 min. Neuromuscular monitoring was performed with acceleromyography using train-of-four (TOF) stimulation. Onset time, time to reappearance of T1, T4, TOF ratio 90% and 100% were recorded. RESULTS: All pigs in group H experienced loss of T1 throughout rocuronium infusion, whereas six out of seven pigs in group L had reappearance of T1 during rocuronium infusion, with additional reappearance of T4 in three of these pigs. The time to recovery of TOF ratio 90% was 14.0 ± 5.4 (L) and 21.7 ± 6.1 (H) minutes and recovery to TOF ratio 100% was 18.7 ± 6.5 (L) and 27.9 ± 9.2 min (H) (mean ± SD). Substantial inter-animal variation in neuromuscular recovery time was observed. CONCLUSION: The large inter-animal variation in pharmacodynamic profiles emphasizes that individual neuromuscular monitoring and titration to effect should be used routinely in research protocols that include rocuronium. In addition to other important measures, these actions are key in order to avoid overdosing and limit the risk of residual neuromuscular blockade.

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

OBJECTIVE: To compare the effects of sevoflurane, propofol and alfaxalone on the neuromuscular blockade induced by a single intravenous bolus of rocuronium in dogs. STUDY DESIGN: A randomized, prospective, crossover experimental study. ANIMALS: A total of eight adult Beagle dogs (four female, four male), weighing 8.9-15.3 kg and aged 5-7 years. METHODS: The 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. RESULTS: The 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 RELEVANCE: Compared with alfaxalone and propofol, sevoflurane prolonged rocuronium-induced neuromuscular blockade by a significantly greater extent in dogs.

Neuromuscular blockade effects of cisatracurium in 11 cats undergoing ophthalmological surgery anaesthetised with isoflurane.

CASE SERIES SUMMARY: This case series describes the neuromuscular blockade (NMB) following 0.15 mg/kg intravenous (IV) cisatracurium administration in 11 cats undergoing ophthalmological surgery and anaesthetised with isoflurane. Anaesthetic records were analysed retrospectively. Neuromuscular function was assessed by a calibrated train-of-four (TOF) monitor. Cats were 73 ± 53 months old, weighed 4 ± 1 kg and were of American Society of Anesthesiologists' physical classification 2. Duration of anaesthesia and surgery were 144 ± 27 and 94 ± 24 mins, respectively. The lowest TOF count was zero in four cats, four in six cats and for one cat the TOF ratio never decreased below 31%. The time of onset was between 1 and 6 mins after the administration of cisatracurium and the mean duration of action was 20.4 ± 10.1 mins. RELEVANCE AND NOVEL INFORMATION: Cisatracurium at a dose of 0.15 mg/kg IV did not consistently induce a TOF count of zero in all cats. The dose used in these cats did not produce any remarkable cardiovascular side effects. Although the NMB was not complete, the dose given was sufficient to produce central eyeball position, which was the goal of the ophthalmic surgeries.

Neuromuscular blockade with atracurium for ophthalmic surgery in horses-Effects on surgical and anesthetic characteristics and recovery quality.

OBJECTIVE: To study the surgical, anesthetic and recovery qualities of horses receiving either a neuromuscular blocking agent (atracurium) or intravenous lidocaine (treatment groups A and L, respectively). ANIMALS STUDIED: A total of thirty horses presented for ocular surgery were used in this study. PROCEDURE: Horses were randomly assigned to receive either atracurium (group A) or a lidocaine constant rate infusion (group L). Surgical quality was graded on a scale from 1 (excellent)-5 (poor). While anesthetized, the heart rate, oxygen saturation and mean arterial blood pressure, and end-expiratory carbon dioxide and desflurane concentration were monitored and recorded every 5 minutes. Recovery was scored on a scale from 10 (best)-115 (worst). RESULTS: Horses in treatment group A needed significantly less desflurane then horses in treatment group L (p = 0.04). Horses in treatment group A had a significantly better surgery score of 1 (1-2) (median and range) then horses in treatment group L (2.5; 1-5) (p = 0.02). The quality of recovery was significantly better in horses in treatment group A compared with treatment group L, and horses needed significantly less time to reach the standing position. CONCLUSIONS: Atracurium and lidocaine CRI are safe methods of anesthesia for equine patients undergoing ocular surgery. Horses receiving atracurium needed less desflurane and had better surgery and recovery scores than horses receiving a lidocaine constant rate infusion.

The train-of-four or double-burst ratios cannot reliably exclude residual neuromuscular block in cats.

This study investigated the relationship between train-of-four (TOF) or double burst (DBS) ratios (T4:T1 or B2:B1) and twitch (T1) or burst (B1) magnitudes during the recovery from rocuronium-induced neuromuscular block in dogs and cats. The main hypothesis was that TOF or DBS ratios recover after the recovery of T1 or B1, and hence high ratio levels are sensitive indicators of restoration of the neuromuscular function. Six anesthetized dogs and six anesthetized cats received 0.5 mg/kg of rocuronium intravenously. The amplitudes of T1 or B1 were measured with mechanomyography during neuromuscular block until the neuromuscular function recovered fully. The TOF or DBS ratio was recorded concurrently. In dogs, recovery of T1 and B1 preceded the recovery of the TOF and DBS ratios, and T1 and B1 were always ≥90% of recovery when the respective ratio reached 0.9. In contrast, T1 was still depressed in 5/6 cats when the TOF ratio reached 0.9. At that moment, T1 was 72.5 ± 19.8% of recovery. Similarly, the DBS ratio returned to 0.9 when B1 was still <90% in 3/6 cats of recovery. The TOF and DBS fade in dogs consistently disappeared after the magnitude of T1 or B1 were restored, and hence, ratios ≥0.9 are a sensitive indicator that the neuromuscular function recovered. Our observation in cats however show that the spontaneous recovery of neither the TOF nor the DBS ratio of 0.9 can reliably exclude residual block, as the magnitude of T1 or B1 was still depressed in several instances.

Bloqueio motor e sensitivo da lidocaína ou da ropivacaína peridural em cães / [Motor and sensitive blockade provided by epidural lidocaine or ropivacaine in dogs]

Objetivou-se avaliar o bloqueio sensitivo e motor da administração peridural de 0,2mL/kg de duas concentrações de ropivacaína em comparação à lidocaína em cães. Utilizaram-se 24 cães, distribuídos em quatro grupos: NaCl a 0,9% (GS), lidocaína a 2% (GL), ropivacaína a 0,5% (GR5) e ropivacaína a 0,75% (GR7,5). Avaliaram-se a presença de movimentação espontânea, deambulação, sensibilidade superficial e profunda nos momentos cinco, 10, 15, 20, 25, 30, 45, 60, 90, 120, 180, 240 e 300 minutos após peridural. O retorno à movimentação espontânea foi semelhante entre GL (42,50 ± 6,12) e GR7,5 (69,2 ± 58,9). O tempo para deambulação foi mais prolongado em GR7,5 (107,5 ± 79,3) que em GS (9,2 ± 3,8) e em GR5 (32,5 ± 20,9). O retorno da sensibilidade profunda foi maior em GR 7,5 (152,5 ± 89,2) que em GS (5,8 ± 2,0), GR5 (46,7 ± 46,3) e GL (52,5 ± 20,7). O tempo de retorno da sensibilidade superficial foi maior em GR7,5 (205,0 ± 129,3) que em GS (7,5 ± 2,7), GL (72,5 ± 19,9) e GR5 (97,5 ± 55,1). Apesar do retorno precoce da movimentação, ropivacaína 0,75% está relacionada a tempo prolongado de recuperação da função muscular e bloqueio sensitivo mais prolongado que lidocaína e ropivacaína 0,5%.(AU)

The aim of the present study was to evaluate the sensory and motor blockade of epidural 0.5% and 0.75% Ropivacaine or Lidocaine in dogs. Twenty-four dogs were distributed in four groups: 0.9% NaCl (GS), 2% lidocaine (GL), 0.5% ropivacaine (GR5) and 0.75% ropivacaine (GR7.5). Spontaneous movement, ability to walk, superficial, and deep pain response were assessed 5, 10, 15, 20, 25, 30, 45, 60, 90, 120, 180, 240 and 300 minutes after epidural. Time to return to spontaneous movement was similar between GL (42.50 ± 6.12) and GR7.5 (69.2 ± 58.9). Time to return to ambulation was longer in GR7.5 (107.5 ± 79.3) than in GS (9.2 ± 3.8) and GR5 (32.5 ± 20.9). Time to recover deep sensitivity was longer in GR 7.5 (152.5 ± 89.2) than in GS (5.8 ± 2.0), GR5 (46.7 ± 46.3) and GL (52.5 ± 20.7). Time to return superficial sensitivity was longer in GR7.5 (205.0 ± 129.3) when compared to GS (7.5 ± 2.7), GL (72.5 ± 19.9) and GR5 (97.5 ± 55.1). Despite the early return of spontaneous movement, 0.75% ropivacaine is related to longer periods for muscle function recovery and longer sensory block than lidocaine and 0.5% ropivacaine.(AU)

Development of a lateral ultrasound-guided approach for the proximal radial, ulnar, median and musculocutaneous (RUMM) nerve block in cats.

OBJECTIVE: To describe a lateral ultrasound (US)-guided approach to the radial, ulnar, median and musculocutaneous (RUMM) nerves through a single proximal in-plane insertion in cats and to determine whether one or two injection points are required to successfully stain all the target nerves. STUDY DESIGN: Prospective study. ANIMALS: A total of eight client-owned healthy cats and 12 cat cadavers. METHODS: In live cats, the US anatomy of the brachium, the landmarks and the site for needle accesses were determined. Then, 12 thawed feline cadavers were used to assess the spread of dye solution and nerve staining following the US-guided proximal-lateral-humeral RUMM injection using one and two injection points. Each cadaver was injected with 0.15 mL kg-1 of a 0.25% new methylene blue solution in either a single injection aimed for the radial nerve of one limb (G1) or via two sites delivering 0.1 mL kg-1 and 0.05 mL kg-1 aimed for the radial and musculocutaneous nerves of the opposite limb, respectively (G2). Upon dissection, staining of the target nerves around their circumference for length of >1 cm was considered successful. RESULTS: Sonoanatomy was consistent with anatomy upon dissection and target nerves were identified in all cadavers. Staining was 100% successful for the radial, median and ulnar nerves in both groups, and 41.7% and 100% for the musculocutaneous nerve in G1 and G2, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: This novel lateral US-guided approach for the proximal RUMM nerve block allowed a good identification of the nerves and related structures, and it provided a consistent muscular structure through which the needle could be easily guided. An injection performed in two aliquots (within the caudal and cranial compartments of the neurovascular sheath) appeared to be necessary to successfully stain all the target nerves.

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

OBJECTIVE: To compare the neuromuscular blocking effects of cisatracurium during isoflurane versus propofol anesthesia in dogs. STUDY DESIGN: Prospective, randomized study. ANIMALS: A total of 20 healthy, client-owned dogs (16 females, four males) weighing 12.5-22 kg and aged 1-8 years. METHODS: Dogs 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. RESULTS: Incremental 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 RELEVANCE: Cisatracurium-induced neuromuscular blockade was significantly enhanced and prolonged by isoflurane compared with propofol.

Onset and duration of cis-atracurium neuromuscular block during fentanyl and lidocaine infusions in isoflurane-anaesthetised dogs.

BACKGROUND: This retrospective study assessed the onset and duration of the neuromuscular block (NMB) induced by cis-atracurium 0.15 mg/kg intravenously with and without fentanyl or lidocaine infusions in 45 isoflurane-anaesthetised dogs. METHODS: Dogs with neuromuscular function assessed by a calibrated train-of-four (TOF) monitor with stimulation (every 13 s) of the peroneal nerve were included. The onset and duration of the NMB were defined as the time from cis-atracurium administration until TOF=0 and the time during TOF=0 display, respectively. RESULTS: The NMB onset was shorter during fentanyl (mean±sd) (1.9±0.7 minutes; P=0.0042) and lidocaine (2.0±0.7 minutes; P=0.0154) compared with control (2.9±0.8 minutes). The NMB duration was shorter in the fentanyl (27.5±7.3 minutes; P=0.0491), but not in the lidocaine group (32.3±6.9 minutes; P=0.0790), compared with control (33.7±9.1 minutes). The NMB onset was poorly but significantly correlated with the dose of fentanyl and lidocaine administered before cis-atracurium (r=-0.3396; P=0.0225). The fentanyl and lidocaine groups received more crystalloid and colloid boluses than the control. CONCLUSIONS: Fentanyl and lidocaine shortened the NMB onset and the former decreased the NMB duration. Further prospective studies are required to clarify whether this was associated with an indirect decrease in blood pressure or a direct interaction between cis-atracurium and fentanyl and lidocaine.

Can we see fade? A survey of anesthesia providers and our ability to detect partial neuromuscular block in dogs.

OBJECTIVE: To assess the ability to visually detect fade during train-of-four (TOF) or double burst stimulation (DBS) in anesthetized dogs recovering from nondepolarizing neuromuscular block. STUDY DESIGN: Online anonymous survey. POPULATION: Data from 112 participants. METHODS: A web-based survey containing 12 videos of the response to ulnar nerve stimulation with TOF and 12 with DBS obtained at different levels of recovery from rocuronium-induced block was distributed to participants of the American College of Veterinary Anesthesia and Analgesia and the Academy of Veterinary Technicians in Anesthesia and Analgesia e-mail lists. Participants were asked to provide their highest training degree in anesthesiology, watch each video no more than twice, and determine whether fade was present. The probability to correctly recognize fade was calculated using binomial general linear models. General linear models and Tukey's tests were used to assess the effects of level of neuromuscular block, pattern of stimulation, and observers' training on the probability to detect fade. RESULTS: The survey was completed by 53 diplomates, 29 licensed veterinary technicians, 24 residents and six doctors of veterinary medicine (DVMs). The probability to detect fade decreased as partial neuromuscular block became more shallow (p < 0.0001). A TOF or DBS ratio of 0.7 had a 50% chance of being detected. DBS was superior to TOF for detecting fade when the ratio was 0.3-0.69. TOF was superior to DBS when the ratio was 0.7-0.9 (p < 0.0001). There were no differences among groups of observers when assessing fade with TOF or DBS. CONCLUSIONS AND CLINICAL RELEVANCE: Detection of fade from observations of the response to TOF in dogs is unreliable. Advance training in anesthesiology or the use of DBS confers little to no advantage for this subjective test.

Neuromuscular block monitoring after the administration of 1 mg/kg intravenous cis-atracurium in the anaesthetized pig.

Neuromuscular blocking agents should be included as part of a balanced anaesthetic protocol to improve anaesthetic management, although doses are not always established for each species. Cis-atracurium is a benzylisoquinolinium neuromuscular blocking agent with an intermediate duration of action devoid of significant adverse effects previously used in pigs with a wide dosage range. Cis-atracurium was administered at 1 mg/kg bolus to sixteen pigs to establish its time profile and effects. The pigs were premedicated intramuscularly with 4 mg/kg azaperone, 8 mg/kg ketamine and 0.2 mg/kg morphine IM and maintained with isoflurane in oxygen. After cis-atracurium administration, neuromuscular monitoring via acceleromyography was started until the recovery of the 90% of the train of four ratio. Complete decrease in the train of four ratio was accomplished in eleven pigs. Onset of action was 70 s, with a recovery of the fourth twitch at 26 min and a recovery of a train of four ratio greater than 90% in 60 min. In conclusion, 1 mg/kg intravenous cis-atracurium in the pig allowed for a rapid onset of action and a complete recovery after 60 min although high variability in the time profile is seen.

Effects of two levels of partial neuromuscular block with atracurium on the ventilatory response to hypercapnia in anesthetized Beagles.

OBJECTIVE To evaluate effects of 2 levels of partial neuromuscular block on the ventilatory response to a hypercapnic challenge in anesthetized dogs and to evaluate effects of edrophonium for reversing partial neuromuscular block. ANIMALS 6 healthy adult Beagles. PROCEDURES Each dog was anesthetized twice with propofol and dexmedetomidine. End-tidal partial pressure of CO2 (Petco2), tidal volume (Vt), and peak inspiratory flow (PIF) were measured during breathing at rest. Maximal Vt and PIF (VtMAX and PIFMAX, respectively) in response to a hypercapnic challenge consisting of 10% CO2 inhaled for 1 minute were measured. Variables were measured before administration of atracurium (baseline), during moderate (train-of-four [TOF] ratio, 0.3 to 0.5) and mild (TOF ratio, 0.6 to 0.8) atracurium-induced neuromuscular block, and after neuromuscular block recovery (TOF ratio, ≥ 0.9) following administration of edrophonium or saline (0.9% NaCl) solution. Dogs for which any variable returned to < 80% of the baseline value were identified. RESULTS Partial neuromuscular block increased Petco2; it impaired Vt at rest and VtMAX but not PIF at rest and PIFMAX. All variables except Petco2 returned to baseline values when the TOF returned to ≥ 0.9. After recovery from neuromuscular block, significantly more dogs had a VtMAX < 80% of the baseline value when edrophonium was not administered. CONCLUSIONS AND CLINICAL RELEVANCE Partial neuromuscular block in anesthetized Beagles decreased spontaneous ventilation at rest and impaired the response to a hypercapnic challenge. Response to hypercapnic challenge might remain partially impaired after recovery of the TOF ratio to ≥ 0.9.