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.

Retrospective study of the prevalence of factors contributing to successful standing at first attempt in horses recovering from general anesthesia.

OBJECTIVE: Several factors affect the quality of recovery from general anesthesia in horses. These can increase the likelihood of injury. Body and limb position during recovery may correlate with successful standing. The objective of this study was to identify the prevalence of and the factors associated with successful standing at the first attempt in horses undergoing general anesthesia. STUDY DESIGN: Retrospective study. METHODS: Video of recovery and anesthetic records from 221 equine patients were reviewed by six veterinary students. Cases with poor video quality or incomplete anesthetic records were excluded. Demographic variables, type of procedure, perioperative drugs administered, assistance during recovery and body and limb positions during the first attempt to stand were recorded. Association between putative variables (including specific descriptors for body and limb position) and success for standing were analyzed using backward logistic regression; significance was set at 0.05. A decision tree for a successful attempt was created to predict the outcome of a recovery attempt based on these variables. RESULTS: Extension of the carpal joints, head and neck alignment with the thoracic limbs, greater time in lateral recumbency, coordination during sternal recumbency, longer time to first attempt to stand and pelvic limb position were associated with successful standing at the first attempt. The association between extension of the carpal joints with wide base positioning of the pelvic limbs provided the best success rate for standing, whereas the association of flexed carpal joints and head and neck orientation different from the thoracic limbs resulted in a worse success rate. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that certain limb and body positions displayed by horses during recovery may be associated with the likelihood of successful standing at the first attempt. These variables may be useful for assessing recovery quality in future research.

Questionnaire on the process of recovering horses from general anesthesia and associated personnel injury in equine practice.

OBJECTIVE: To collect data about the current practice of recovering horses from general anesthesia and recovery personnel safety. STUDY DESIGN: Online survey. METHODS: An online questionnaire, including questions on general demographic data, recovery drugs, modality and characteristics of equine recovery and morbidity and mortality, was designed and distributed via e-mail to equine practitioners worldwide. RESULTS: Practitioners from 22 countries completed 373 questionnaires; 53% of the participants were board-certified equine surgeons, and the remainder were board-certified anesthesiologists (18%), large animal residents (8%), general practitioners (7%), large animal interns (6%), anesthesia residents (4.5%) and veterinary technicians (1.6%). Respondents were employed by academia (58%) or private practice (42%). Of the respondents employed at a university, 93% had a board-certified anesthesiologist on staff compared with 7% of respondents employed at a private practice. Most of the respondents assist horses during recovery, with 23% assisting every recovery and 44% assisting recovery in the majority of cases. Reasons for choosing to assist horses during recovery were: orthopedic procedures (57%), neurological deficits (49%), bad health (47%), history of poor recovery (44%), foals (42%), draft breeds (30%), magnetic resonance imaging (17%) and computed tomography (16%). Unacceptable recoveries were reported by 77% of participants. Commonly reported complications during recovery with any method were: orthopedic injury (66%), myopathy (54%), skin abrasion (53%) and airway obstruction (37%). The incidences of unacceptable quality of recovery (p = 0.09) or personnel injury (p = 0.56) were not different between assisted and nonassisted recoveries; however, more equine fatalities were reported for assisted recoveries (p < 0.006). Practitioners in academia reported more unacceptable recoveries (p < 0.0007) and personnel injuries (p < 0.002) compared with those in private practice. CONCLUSIONS: The method of recovery differs among hospitals. Recovery personnel injuries associated with assisting horses during recovery are an important and previously unreported finding.

The Canine Postamputation Pain (CAMPPAIN) initiative: a retrospective study and development of a diagnostic scale.

OBJECTIVE: To develop a scale to diagnose and assess the severity of postamputation pain (PAP) in dogs. STUDY DESIGN: Single-center retrospective study. ANIMALS: A total of 66 dogs that underwent thoracic or pelvic limb amputation and 139 dogs that underwent tibial plateau leveling osteotomy (TPLO) at a veterinary teaching hospital. METHODS: An online survey regarding postoperative behavioral changes was sent to owners. Categorical, multiple-choice responses were entered into a univariable logistic regression model and tested for association with amputation using the Wald test. If p < 0.2, variables were forwarded to a multivariable logistic regression model for manual build. Model simplicity and predictive ability were optimized using the area under the receiver operating curve (AUROC) characteristic, and model calibration was assessed using the Hosmer-Lemeshow test. The selected model was converted to an integer scale (0-10), the Canine Postamputation Pain (CAMPPAIN) scale. Univariable logistic regression related each dog's calculated score to the probability of PAP. RESULTS: Multivariable logistic regression identified four independent predictors of PAP (p < 0.05): 1) restlessness or difficulty sleeping, 2) episodes of panic or anxiety, 3) sudden vocalization, and 4) compulsive grooming of the residual limb. Score AUROC was 0.70 (95% confidence interval = 0.63-0.78) with good calibration (Hosmer-Lemeshow statistic p = 0.82). A score of 2 corresponded to a risk probability of 0.5. Taking a score ≥ 2 to indicate PAP, score specificity and sensitivity were 92.1% and 36.4%, respectively. When this score was used to diagnose PAP, prevalence was 36.4% (24/66) and 7.9% (11/139) in the amputation and TPLO groups, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Postamputation pain is characterized by specific postoperative behaviors and appears to affect approximately one-third of canine amputees. The CAMPPAIN scale generated from these data could facilitate diagnosis, treatment and further study of PAP but requires external validation.

Evaluation of a regional nerve block with an experimental formulation of encapsulated lidocaine in sheep.

OBJECTIVE: To compare the duration of nociceptive and proprioceptive blockade from an experimental encapsulated lidocaine preparation with that of conventional lidocaine. STUDY DESIGN: Prospective, blinded, randomly assigned, crossover study. ANIMALS: A total of six adult Dorset ewes, American Society of Anesthesiologists physical status I or II, weighing 60.4 ± 18.0 kg (mean ± standard deviation). METHODS: Under general anesthesia and guided by electrolocation, the common peroneal nerve was blocked unilaterally with encapsulated lidocaine (0.1 mL kg-1, 200 mg mL-1) or conventional lidocaine hydrochloride (0.1 mL kg-1, 20 mg mL-1). Each sheep was administered both treatments with an interval of 2 weeks between treatments. Nociception and proprioception were scored (scales of 0-3) before anesthesia, at 0.5, 1, 2, 4, 8, 12, 16, 20 and 24 hours after completion of local anesthetic injection, and every 12 hours thereafter for 9 days. Nociceptive and proprioceptive blockade ended the first time each score reached '0'; maximum blockade duration was considered and recorded to be the time point immediately prior to this end point. Significance of differences between treatments for duration of blockade was tested with the Wilcoxon rank-sum test. Effects of time and treatment on nociceptive and proprioceptive blockade were evaluated with mixed-effect models. Significance was set at p < 0.05. RESULTS: Compared with conventional lidocaine, nociceptive blockade lasted 88 hours longer with encapsulated lidocaine (p = 0.008), and proprioceptive blockade lasted 6 hours longer (p = 0.03). Significant effects of time (p < 0.0001), treatment (p = 0.0435) and treatment∗time (p < 0.0001) were observed for nociception. Significant effects of time (p < 0.0001) and treatment∗time (p = 0.0058) were observed for proprioception. CONCLUSION: Encapsulated lidocaine produced nociceptive blockade with a duration substantially longer than conventional lidocaine. CLINICAL RELEVANCE: Sustained-release encapsulated lidocaine alleviates pain and may minimize systemic analgesic use.

Postoperative oxygenation in healthy dogs following mechanical ventilation with fractions of inspired oxygen of 0.4 or >0.9.

OBJECTIVE: To evaluate arterial oxygenation during the first 4 postoperative hours in dogs administered different fractions of inspired oxygen (FiO2) during general anesthesia with mechanical ventilation. STUDY DESIGN: Prospective, randomized clinical trial. ANIMALS: A total of 20 healthy female dogs, weighing >15 kg and body condition scores 3-7/9, admitted for ovariohysterectomy. METHODS: Dogs were randomized to breathe an FiO2 >0.9 or 0.4 during isoflurane anesthesia with intermittent positive pressure ventilation. The intraoperative PaO2:FiO2 ratio was recorded during closure of the linea alba. Arterial blood was obtained 5, 60 and 240 minutes after extubation for measurement of PaO2 and PaCO2 (FiO2 = 0.21). Demographic characteristics, duration of anesthesia, PaO2:FiO2 ratio and anesthetic agents were compared between groups with Wilcoxon tests. The postoperative PaO2, PaCO2, rectal temperature, a visual sedation score and events of hypoxemia (PaO2 < 80 mmHg) were compared between groups with mixed-effects models or generalized linear mixed models. RESULTS: Groups were indistinguishable by demographic characteristics, duration of anesthesia, anesthetic agents administered and intraoperative PaO2:FiO2 ratio (all p > 0.08). Postoperative PaO2, PaCO2, rectal temperature or sedation score were not different between groups (all p > 0.07). During the first 4 postoperative hours, hypoxemia occurred in three and seven dogs that breathed FiO2 >0.9 or 0.4 during anesthesia, respectively (p = 0.04). CONCLUSIONS AND CLINICAL RELEVANCE: The results identified no advantage to decreasing FiO2 to 0.4 during anesthesia with mechanical ventilation with respect to postoperative oxygenation. Moreover, the incidence of hypoxemia in the first 4 hours after anesthesia was higher in these dogs than in dogs breathing FiO2 >0.9.

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.

Histological, electrophysiological and clinical effects of thermal radiofrequency therapy of the saphenous nerve and pulsed radiofrequency therapy of the sciatic nerve in dogs.

OBJECTIVE: Thermal radiofrequency (TRF) of the saphenous nerve (a sensory nerve) combined with pulsed radiofrequency (PRF) of the sciatic nerve (a sensory and motor nerve) might relieve intractable stifle osteoarthritis (OA) pain in dogs. The objective was to determine if saphenous nerve TRF induces Wallerian degeneration and if sciatic nerve PRF induces degeneration or dysfunction. STUDY DESIGN: Blinded, controlled, randomized, preclinical study. ANIMALS: A group of six intact, female Beagle dogs aged 14-16 months. METHODS: In each dog, one pelvic limb was assigned randomly to the control group and the other to the treatment group. Dogs were anesthetized and, using ultrasonography, radiofrequency electrodes were positioned adjacent to saphenous and sciatic nerves bilaterally; TRF and PRF were performed only in the treatment limb. Motor nerve conduction velocity (MNCV) was measured in both sciatic nerves 2 weeks later, and the dogs were euthanized. Hematoxylin and eosin-stained sections of saphenous and sciatic nerves were examined using light microscopy. Degeneration and inflammation were scored 0 (none) to 3 (severe). A one-tailed, paired Wilcoxon signed-rank test was used to test for differences in scores and MNCV between control and treatment nerves. RESULTS: Degeneration and inflammation scores were higher in treatment saphenous nerves in 5/6 dogs [83%; 95% confidence interval (CI), 36%, 99%]; however, after Bonferroni correction only degeneration score was higher (p = 0.0313). Degeneration, inflammation or decreased MNCV were not observed in sciatic nerves (each outcome: 0/6 nerves, 0%; 95% CI, 0%, 48%). No dogs experienced postprocedural pain or neurological deficits. CONCLUSIONS AND CLINICAL RELEVANCE: The degeneration in TRF-treated saphenous nerves appears sufficient to impair transmission. Sciatic nerve PRF did not cause degeneration with attendant motor deficits, consistent with a proposed neuromodulatory mechanism. A clinical trial is needed to confirm the combined techniques produce analgesia without motor deficits in dogs with stifle OA.

A retrospective analysis of the epidural use of bupivacaine 0.0625-0.125% with opioids in bitches undergoing cesarean section.

Epidural anesthesia, often used during cesarean surgery, can exacerbate hypotension from general anesthesia and delay discharge due to motor block. Decreasing the local anesthetic dose might reduce those complications. Cases of dogs undergoing cesarean section that were anesthetized without epidural (n = 29) (control) and dogs with low-dose epidural bupivacaine with fentanyl or buprenorphine (n = 37) were reviewed. The incidence of hypotension was equal between groups. Intraoperative opioids were administered more to control (93%) than to treated dogs (18%; P < 0.0001). Epidural bupivacaine 0.0625-0.125% combined with an opioid reduced the use of intraoperative opioids and did not exacerbate arterial hypotension during cesarean section in anesthetized dogs.

Analyse rétrospective de l'utilisation de bupivacaine 0,0625­0,125 % avec des opioïdes lors d'épidurale chez des chiennes soumises à une césarienne. L'anesthésie épidurale, souvent utilisée lors d'une césarienne, peut exacerber l'hypotension due à l'anesthésie générale et retarder le congé à cause d'un bloc moteur. Une diminution de la dose d'anesthésique local pourrait réduire ces complications. Une revue fut effectuée des cas de chiennes soumises à une césarienne et anesthésiées sans épidurale (n = 29) (témoin) et des chiennes avec une épidurale en utilisant une faible dose de bupivacaine avec du fentanyl ou de la buprenorphine (n = 37). L'incidence d'hypotension était égale entre les groupes. Des opioïdes intra-opératoires furent administrés plus fréquemment chez les témoins (93 %) que chez les animaux traités (18 %; P < 0,001). De la bupivacaine 0,0625­0,125 % en épidurale combinée à un opioïde réduisit l'utilisation d'opioïdes intra-opératoires et n'a pas exacerbé l'hypotension artérielle durant la césarienne chez des chiennes anesthésiées.(Traduit par Dr Serge Messier).

Survey of how different groups of veterinarians manage the use of neuromuscular blocking agents in anesthetized dogs.

OBJECTIVE: To analyze practice habits associated with the use, reversal and monitoring of nondepolarizing neuromuscular blocking agents (NMBAs) in dogs by different groups of veterinarians. STUDY DESIGN: Online anonymous survey to veterinarians. POPULATION: Data from 390 answered surveys. METHODS: A questionnaire was sent to e-mail list servers of the American College of Veterinary Anesthesia and Analgesia (ACVAA-list), Sociedad Española de Anestesia y Analgesia Veterinaria (SEEAV-list), Colégio Brasileiro de Anestesiologia Veterinária (Brazilian College of Veterinary Anesthesiology; CBAV-list) and American College of Veterinary Ophthalmologists (ACVO-list) to elicit information regarding use of NMBAs and reversal agents, monitoring techniques, criteria for redosing, reversing and assessing adequacy of recovery of neuromuscular function. Binomial logistic regression was used to test for association between responses and group of veterinarians in selected questions. RESULTS: Veterinarians of the ACVO-list use NMBAs on a higher fraction of their caseload than other groups (all p < 0.0001). Subjective assessment (observation) of spontaneous movement, including spontaneous breathing, is the most common method for assessing neuromuscular function (43% of pooled responses); 18% of participants always reverse NMBAs, whereas 16% never reverse them. Restoration of neuromuscular function is assessed subjectively by 35% of respondents. Residual neuromuscular block is the most common concern regarding the use of NMBAs for all groups of veterinarians. Side effects of reversal agents (anticholinesterases) were of least concern for all groups. CONCLUSIONS AND CLINICAL RELEVANCE: While most veterinarians are concerned about residual neuromuscular block, relatively few steps are implemented to reduce the risks of this complication, such as routine use of quantitative neuromuscular monitoring or routine reversal of NMBAs. These results suggest a limitation in transferring information among groups of veterinarians, or in implementing techniques suggested by scientific research.

Changes in blood volume indicators and dynamic indicators measured with transpulmonary ultrasound velocity during blood depletion and repletion in a neonatal swine model.

BACKGROUND: Dynamic indicators such as pulse pressure and stroke volume variations can be measured to track changes in preload during hemorrhage, and evaluate fluid therapy. However, these dynamic indicators require mechanical ventilation, and might be affected by cardiac dysrhythmias and changes in vascular tone. Blood volume indicators may offer alternatives for assessing changes in volume status. AIMS: The aims of this study were to measure changes in blood volume indicators and dynamic indicators during removal of blood in two stages and subsequent blood replacement in anesthetized, mechanically ventilated, neonatal pigs. METHODS: In eight anesthetized, mechanically ventilated piglets (5-6 weeks old), cardiac index, stroke volume index, total end-diastolic volume, central blood volume, active circulating volume, pulse pressure variation, and stroke volume variation were measured during blood removal in two stages (15 mL kg-1 each stage) and blood replacement (30 mL kg-1 ). Values after each intervention were measured for each parameter. RESULTS: All indicators differed from baseline after removal of 15 mL kg-1 of blood, except for stroke volume variation. Differences between both stages of hemorrhage were only observed for indexed stroke volume, total end-diastolic volume, central blood volume, and pulse pressure variation. CONCLUSION: Total end-diastolic volume and central blood volume changed during blood depletion and repletion, and differed between stages of hemorrhage. These indicators might be useful for assessing volume status instead of, or in addition to cardiac index and dynamic indicators.

Positive and negative staircase effect during single twitch and train-of-four stimulation: a laboratory study in dogs.

A positive staircase effect is well documented during neuromuscular monitoring. However, the increase in twitch amplitude may not remain stable over time. We compared the staircase phenomenon and twitch stability during single twitch (ST) or train-of-four (TOF) stimulation in anesthetized dogs. Force of contraction was measured in ten dogs. Each thoracic limb was stimulated with ST 0.1 Hz or TOF q 12 s for 25 min (random order). No neuromuscular blockers were administered. Every 5 min, ST and T1 amplitudes were compared within and between groups. Stability of twitch amplitude (<5 % change in 5 min) was also evaluated. ST and T1 amplitude increased over time without significant differences between groups. After 10 min of ST stimulation, the average ST amplitude had increased significantly to 107 %, and remained unchanged thereafter. T1 amplitude was significantly greater than baseline only at 5 (111 %) and 10 min (109 %); a decline towards baseline occurred thereafter. Stability was reached after 15 min for all dogs in the ST group, however, three dogs continued to have changes >5 % with TOF. An initial increase in ST amplitude remained stable over the observation period, but the increase in T1 amplitude during TOF was frequently followed by a decay. A stable twitch amplitude (variation <5 % in 5 min) was observed in all dogs with ST after 15 min of stimulation, which was not the case during TOF stimulation. Therefore, it appears at least in dogs, that ST might offer some advantages over T1 for measuring twitch amplitude.

Ultrasound-guided thoracic paravertebral injection in dogs: a cadaveric study.

OBJECTIVE: To describe ultrasound-visualized anatomy and the spread characteristics of a dye injected in the thoracic paravertebral (TPV) space under ultrasound guidance. STUDY DESIGN: Anatomic cadaver study. ANIMALS: Seven dog cadavers. METHODS: One cadaver was used to observe, identify, and describe the relevant TPV anatomy. In the remaining six, the left fifth TPV space was randomly assigned to be injected with either a low volume (LV; 0.05 mL kg-1) or high volume (HV; 0.15 mL kg-1) of dye. Subsequently, the contralateral side was injected with the alternative volume. Anatomic dissections were conducted to determine the incidence of complete spinal nerve staining (>1 cm circumferential coverage), number of contiguous spinal nerves dyed and the absence or presence of solution in particular locations. RESULTS: The ultrasound-visualized anatomy of the TPV space was defined as the intercostal space abaxial to the vertebral body, delimited by the parietal pleura ventrally and the internal intercostal membrane dorsally. The endothoracic fascia divides the paravertebral space into dorsal and ventral compartments. The target nerve was completely dyed in five of six and six of six injections in the LV and HV conditions, respectively. In one LV injection, the nerve was partially dyed. No multisegmental spread affecting contiguous spinal nerves was found in either treatment. Multisegmental spread was found in the ventral compartment of the TPV space, affecting the sympathetic trunk on 3 (0-3) and 3.5 (1-6) vertebral spinal levels in the LV and HV conditions, respectively, but differences between volumes were not significant. No intrapleural, ventral mediastinal or epidural migration was observed. CONCLUSIONS AND CLINICAL RELEVANCE: Ultrasound-guided TPV block is a potentially reliable technique. The LV appeared sufficient to dye a single spinal nerve and multiple sympathetic trunk vertebral levels. Multiple TPV injections may be needed to provide adequate thoracic analgesia in dogs undergoing thoracic surgery.

Recovery from rocuronium-induced neuromuscular block was longer in the larynx than in the pelvic limb of anesthetized dogs.

OBJECTIVE: To determine if neuromuscular monitoring at the pelvic limb accurately reflects neuromuscular function in the larynx after administration of rocuronium in anesthetized dogs. STUDY DESIGN: Prospective experimental study. ANIMALS: Six healthy Beagle dogs. METHODS: Anesthesia was maintained in dogs with isoflurane and a continuous infusion of dexmedetomidine. Rocuronium (0.6 mg kg-1) was administered intravenously to induce neuromuscular block. Train-of-four (TOF) impulses were applied to the left recurrent laryngeal nerve (RLn) and the peroneal nerve (Pn). The evoked TOF ratio (TOFR; T4:T1) was measured with electromyography (EMG) simultaneously at the larynx and at the pelvic limb. Spontaneous recoveries of T1 to 25% (T125%) and 75% (T175%) of twitch height, and to TOFR of 0.70 and 0.90 (TOFR0.90) at each EMG site were compared. RESULTS: Data from five dogs were analyzed. Times to T125% were similar at the pelvic limb and larynx when measured by EMG; time to T175% was slower at the larynx by 6±4 minutes (p=0.012). The larynx had a slower recovery to TOFR0.70 (41±13 minutes) and TOFR0.90 (45±13 minutes) than did the pelvic limb [29±8 minutes (p=0.011) and 33±9 minutes (p=0.003), respectively]. When the pelvic limb EMG returned to TOFR0.70 and TOFR0.90, the larynx EMG TOFR0.70 and TOFR0.90 values were 0.32±0.12 (p=0.001) and 0.38±0.13 (p=0.001), respectively. CONCLUSIONS AND CLINICAL RELEVANCE: After administration of rocuronium, neuromuscular function assessed by EMG recovered approximately 36% slower at the larynx than at the pelvic limb. The results in these dogs suggest that quantitative neuromuscular monitoring instrumented at a pelvic limb may be unable to exclude residual block at the larynx in anesthetized dogs.

Effects of neostigmine or edrophonium on force of contraction when administered at a train-of-four ratio of 0.9 in anesthetized dogs.

OBJECTIVE: Anticholinesterase drugs may produce paradoxical neuromuscular block when administered at shallow levels of neuromuscular block. The objective of this study was to evaluate the effects of neostigmine and edrophonium when administered at near-complete reversal from nondepolarizing block in anesthetized dogs. STUDY DESIGN: Incomplete crossover, randomized, blinded experimental study. ANIMALS: A total of 12 Beagle dogs. METHODS: Each dog was anesthetized twice with propofol and maintained with isoflurane and dexmedetomidine. Intravenous (IV) vecuronium (0.1 mg kg-1) was administered. When the mechanographic train-of-four (TOF) ratio had spontaneously recovered to ≥0.9, either neostigmine (0.04 mg kg-1) or edrophonium (0.5 mg kg-1) was administered IV, preceeded by atropine. Changes in twitch height or TOF ratio were measured for the next 10 minutes. Recurarization was considered to be present if values decreased by ≥10%. RESULTS: Data from four dogs in each treatment were excluded from analysis, resulting in data from five dogs administered both treatments, three dogs administered neostigmine and three dogs administered edrophonium. There was no difference between groups for age, weight, T1 and T4 twitch heights or TOF ratio values, before or after anticholinesterase administration. The TOF ratio decreased by 17% and 18% in two of the eight dogs administered neostigmine, resulting from a larger increase in T1 relative to T4. No reductions in individual twitch amplitudes were recorded in those dogs. When edrophonium was used, no cases of recurarization were observed. CONCLUSIONS AND CLINICAL RELEVANCE: The results support use of edrophonium for reversal of shallow neuromuscular block. The decreases in TOF ratio recorded after neostigmine does not necessarily indicate muscular weakness. Although the clinical implications are uncertain, the results suggest that, at these doses, edrophonium may be preferable to neostigmine for reversal of shallow neuromuscular block in dogs.

Partial neuromuscular block impairs arytenoid abduction during hypercarbic challenge in anesthetized dogs.

OBJECTIVE: To evaluate the effect of two levels of partial neuromuscular block (NMB) on arytenoid abduction, tidal volume (VT) and peak inspiratory flow (PIF) in response to a hypercarbic challenge in anesthetized dogs. STUDY DESIGN: Prospective laboratory study. ANIMALS: Eleven healthy male Beagle dogs aged 3-5 years. METHODS: Dogs were anesthetized with propofol and dexmedetomidine infusions. The rima glottidis was observed via an endoscope placed through a laryngeal mask airway. Atracurium infusion was titrated to obtain two levels of partial NMB. The normalized glottal gap area (NGGA; glottal gap area normalized to height squared of rima glottidis) at peak inspiration during a hypercarbic challenge (10% CO2 inspired for 1 minute) was measured at baseline, during mild [train-of-four (TOF) ratio 0.4-0.6] and shallow (TOF ratio 0.7-0.9) NMB, and 30 minutes after spontaneous recovery from NMB. The VT and PIF were measured at the same time points and compared using anova for repeated measures and Tukey's post hoc tests. RESULTS: The NGGA and VT were significantly lower than baseline during both levels of partial NMB with no difference between mild and shallow NMB (p < 0.05). They returned to baseline values after spontaneous recovery from NMB. PIF was not altered significantly during partial NMB. CONCLUSIONS AND CLINICAL RELEVANCE: The NGGA and VT at peak inspiration in response to a hypercarbic challenge were reduced during partial NMB block, with decreased abduction of the arytenoid cartilages. This dysfunction was present even at shallow levels of NMB.

Prevention of laryngospasm with rocuronium in cats: a dose-finding study.

OBJECTIVE: To identify the dose of rocuronium that will prevent a laryngeal response to water spraying of the glottis in anesthetized cats. STUDY DESIGN: Randomized crossover study. ANIMALS: Eight healthy, adult, short-haired cats, aged 1-4 years, weighing 3.2-6.0 kg. METHODS: Each cat was anesthetized four times and administered one of four doses of rocuronium (0.1, 0.2, 0.3 and 0.6 mg kg(-1) ) in random order. The larynx was observed with a video-endoscope inserted through a laryngeal mask airway. Video-clips of the laryngeal response to a sterile water spray (0.2 mL) were obtained at baseline (without rocuronium) and at maximal effect of each treatment. Glottal closure score (0-2), duration of glottal closure, and number of adductive arytenoid movements were obtained from video-clips of laryngeal responses (reproduced in slow motion) at baseline and after treatment. Two observers blinded to treatment allocation scored the vigor of the laryngeal response on a visual analog scale (VAS). The duration of apnea (up to 5 minutes) was recorded for each treatment. RESULTS: Compared with baseline, rocuronium 0.3 mg kg(-1) and 0.6 mg kg(-1) significantly decreased all glottal scores obtained from the videos (all p < 0.03). Both observers gave lower VAS scores after 0.3 mg kg(-1) (both p = 0.015). Apnea lasting ≥ 5 minutes occurred in none, one, three and seven of eight cats administered doses of rocuronium 0.1, 0.2, 0.3 and 0.6 mg kg(-1) , respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Rocuronium 0.3 mg kg(-1) and 0.6 mg kg(-1) consistently decreased the completeness and duration of the laryngeal response to water spray, and reduced the number of arytenoid adductive movements in response to that stimulus. However, a laryngeal response was never completely prevented. Rocuronium 0.3 mg kg(-1) may be useful for facilitating tracheal intubation. Positive pressure ventilation must be available for cats administered rocuronium.

Comparison of bupivacaine and dexmedetomidine femoral and sciatic nerve blocks with bupivacaine and buprenorphine epidural injection for stifle arthroplasty in dogs.

OBJECTIVE: To compare the quality of anesthesia and analgesia from femoral and sciatic nerve blocks (FS) with bupivacaine and dexmedetomidine with that from an epidural injection (EPI) with bupivacaine and buprenorphine in dogs undergoing unilateral stifle arthroplasty. STUDY DESIGN: Prospective, blinded, randomized, clinical comparison. ANIMALS: Twenty-six dogs weighing 36 ± 10 kg and aged 5 (1-11) years. METHODS: Dogs were randomly assigned to either FS [n = 13; bupivacaine 0.5% (0.5 mg kg(-1) ) plus dexmedetomidine (0.1 µg kg(-1) ) for each nerve] or EPI [n = 13; bupivacaine 0.5% (1 mg kg(-1) ) plus buprenorphine (4 µg kg(-1) )]. Data collected included intraoperative cardiopulmonary variables and postoperative pain scores (Glasgow Composite Pain Scale), sedation scores, opioid consumption, time to urination and time to return of various behaviors. Rescue analgesia (hydromorphone 0.05 mg kg(-1) ) was administered intravenously whenever pain scores were ≥ 6/24. Subsequent data from rescued dogs were excluded from further analysis. RESULTS: No differences were found for any of the variables evaluated during and after anesthesia. Over 60% (nine dogs in FS, eight dogs in EPI) of patients from either group did not need additional analgesia within the 24 hour observational period. Three and four patients in FS and EPI, respectively, that required rescue analgesia did so within the first 30 minutes after extubation; only one patient in EPI required supplemental analgesia more than 4 hours after extubation. One patient in each group did not urinate spontaneously for 24 hours. CONCLUSIONS AND CLINICAL RELEVANCE: Both techniques have the potential to provide sufficient analgesia for up to 24 hours in approximately two-thirds of dogs. Careful observation for signs of pain and preparedness to intervene is still recommended. The incidence of urinary retention was low in both groups. These techniques show promise for providing high-quality analgesia for stifle arthroplasty.

Continuous minimally invasive cardiac output monitoring with the COstatus in a neonatal swine model: recalibration is necessary during vasoconstriction and vasodilation.

BACKGROUND: The COstatus monitor measures cardiac output via the transpulmonary ultrasound dilution method (COTPUD ) after injection of normal saline, and can calculate continuous cardiac output (CCO) from the arterial pressure waveform. The relationship between arterial waveform and COTPUD however, might be degraded during vasoconstriction/vasodilation. OBJECTIVES: To examine if recalibration of arterial waveform-derived CCO is required during mild vasoconstriction/vasodilation. METHODS: In 10 anesthetized piglets (6.6-10.1 kg), two COstatus monitors calculated the CCO from the same femoral arterial waveform before and during infusions of phenylephrine (PE; 1 or 3 mg·kg(-1) ·min(-1) ) and sodium nitroprusside (SNP; 1 or 5 mg·kg(-1) ·min(-1) ), administered in random order. One monitor was recalibrated (CCORecal ) after each intervention, while the other monitor was not (CCONon-Recal ). Recalibration was performed with COTPUD with 1 ml·kg(-1) normal saline as indicator. The effects of each infusion on hemodynamic parameters were compared with baseline using paired t-tests. The bias, limits of agreement (LOA), and percentage error between simultaneous measurements (CCORecal and CCONon-Recal ) were examined with Bland-Altman plots. RESULTS: Infusion of PE significantly increased COTPUD , heart rate (HR), and arterial pressures but not systemic vascular resistance (SVR). Infusion of SNP decreased arterial pressures without affecting COTPUD , HR, and SVR. There was no bias between CCORecal and CCONon-Recal at the baseline, but a small bias was observed during PE and SNP infusions. The LOA increased approximately 10 fold during vasoconstriction and vasodilation. The percentage error increased from ≤ 5% to 32% and 27% during PE and SNP infusions, respectively. CONCLUSION: Continuous cardiac output (CO) measured with the COstatus monitor requires recalibration during vasoconstriction and vasodilation, even if changes in COTPUD or SVR are not substantial.

The kalaemic and neuromuscular effects of succinylcholine in centronuclear myopathy: A pilot investigation in a canine model.

BACKGROUND: Myopathies are generally considered to increase the risk for succinylcholine-induced hyperkalaemia and may affect the duration of action of neuromuscular blockers. Centronuclear (myotubular) myopathy (CNM) is congenital and produces various degrees of muscular weakness and associated complications such as respiratory failure. The effects of succinylcholine and the potentially lethal consequences of hyperkalaemia on patients with CNM are unknown due to its rarity. One source of information is the dog, as CNM occurs naturally in dogs. Because of its remarkable similarity with the disease in man, canine CNM can serve as a model to further our knowledge of the effects of succinylcholine. OBJECTIVES: We examined the kalaemic and neuromuscular effects of succinylcholine in dogs with and without autosomal-recessive CNM. DESIGN: A prospective, experimental study. SETTING: Anaesthesiology laboratory, College of Veterinary Medicine, Cornell University, New York, USA. PATIENTS: Six dogs with autosomal-recessive CNM and six control dogs. INTERVENTIONS: Dogs received succinylcholine 0.3 mg kg during isoflurane anaesthesia. MAIN OUTCOME MEASURES: Whole blood potassium concentration was measured 5 min before and after succinylcholine administration. Neuromuscular function was measured with acceleromyography and single twitch stimulation. RESULTS: All dogs recovered uneventfully from anaesthesia. The increase in potassium concentration [mean (SD)] following succinylcholine was similar between groups: CNM 0.5 (0.4) mmol l and control 0.7 (0.4) mmol l (P = 0.47). Recovery of the single twitch to 25, 75 and 90% was longer in the CNM group (all P < 0.001); 90% recovery took 35.5 (1.18) min for the CNM group and 23.3 (1.68) min for the control group. CONCLUSION: CNM did not exacerbate the increase in blood potassium that is ordinarily seen with succinylcholine. Recovery from succinylcholine was nearly 50% longer in dogs with CNM. Although our sample size is too small to evaluate the incidence of succinylcholine-induced hyperkalaemia, extrapolation of these findings suggests that increased duration of action should be expected if succinylcholine is given to a patient with autosomal-recessive CNM.