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.

High-dose buprenorphine results in a greater occurrence of postoperative hyperthermia than morphine in a randomized clinical trial in cats undergoing ovariohysterectomy.

OBJECTIVE: To compare the thermoregulatory and analgesic effects of high-dose buprenorphine versus morphine in cats undergoing ovariohysterectomy. ANIMALS: 94 client-owned cats. PROCEDURES: Cats were randomized to receive either buprenorphine 0.24 mg/kg or morphine 0.1 mg/kg subcutaneously (SC) during recovery from ovariohysterectomy. Body temperature measurements were obtained before anesthesia, during anesthesia (averaged), at extubation, and 2, 4, and 16 to 20 hours postoperatively. Signs of pain were assessed, and demographic characteristics were compared between groups. The effects of treatment and time on body temperature, point prevalence of hyperthermia (> 39.2 °C), and pain scores were compared with linear or generalized mixed-effect models. RESULTS: Cats receiving morphine (vs. buprenorphine) were older and heavier (both, P ≤ 0.005). Other group characteristics did not differ between treatments. Cats receiving buprenorphine (vs. morphine) had higher postoperative temperatures (P = 0.03). At 2, 4, and 16 to 20 hours after extubation, the point prevalence of hyperthermia was greater (P = 0.001) for cats receiving buprenorphine (55% [26/47], 44% [21/47], and 62% [27/43], respectively) versus morphine (28% [13/46], 13% [6/46], and 47% [21/44], respectively). There were no differences in pain scores between groups or over time. Five cats receiving buprenorphine and 6 receiving morphine required rescue analgesia within the 24-hour period. CLINICAL RELEVANCE: Administration of buprenorphine (0.24 mg/kg SC), compared with morphine (0.1 mg/kg SC), resulted in higher body temperatures without an apparent advantage with regard to analgesia during the first 20 postoperative hours than morphine. Opioid-induced postoperative hyperthermia could confound the diagnosis of fever from different sources.

Evaluation of noninvasive blood pressure in anesthetized horses: Bias, limits of agreement, and comparative detection of a predetermined mean blood pressure warranting treatment.

Oscillometric blood pressure monitoring may be a practical tool for short procedures or those performed outside of the operating room. Oscillometric and direct blood pressure values in 30 juvenile and adult horses in a clinical setting using mixed effect models were compared. The limits of agreement and percentage errors were also calculated. We evaluated the sensitivity and false positive rate for the oscillometric method to trigger an intervention for treating blood pressure [direct mean arterial pressure (MAP) < 70 mmHg]. Oscillometric MAP and diastolic arterial pressure (DAP) differed from direct values (P < 0.001); systolic arterial pressure (SAP) did not (P = 0.08). Wide limits of agreement were observed. Percentage errors were smaller for SAP (39%) than for MAP and DAP (48% and 72%). The oscillometric monitor indicated there was a requirement for blood pressure treatment with a true positive rate of 82%, consequently, it failed 18% of the times. The false positive rate (unnecessary treatment) was 55%.

Évaluation non invasive de la pression artérielle chez des chevaux anesthésiés: biais, limites d'accord et détection comparative d'une pression artérielle moyenne prédéterminée justifiant un traitement. La surveillance oscillométrique de la pression artérielle peut être un outil pratique pour les procédures courtes ou celles effectuées hors de la salle d'opération. Les valeurs oscillométriques et directes de la pression artérielle chez 30 chevaux juvéniles et adultes en milieu clinique ont été comparées à l'aide de modèles à effets mixtes. Les limites d'accord et les pourcentages d'erreurs furent également calculés. Nous avons évalué la sensibilité et le taux de faux positifs de la méthode oscillométrique pour déclencher une intervention pour le traitement de la pression artérielle [pression artérielle moyenne directe (PAM) < 70 mmHg]. La PAM oscillométrique et la pression artérielle diastolique (PAD) différaient des valeurs directes (P < 0,001); mais pas la pression artérielle systolique (PAS) (P = 0,08). De larges limites d'accord ont été observées. Les pourcentages d'erreurs étaient plus faibles pour PAS (39 %) que pour PAM et PAD (48 % et 72 %). Le moniteur oscillométrique a indiqué qu'il y avait une exigence pour un traitement de la pression artérielle avec un taux de vrais positifs de 82 %, par conséquent, il a échoué 18 % des fois. Le taux de faux positifs (traitement inutile) était de 55 %.(Traduit par Dr Serge Messier).

Evaluation of an oscillometric blood pressure monitor in anesthetized dogs: Agreement with direct measurements and ability to detect hypotension.

We evaluated the agreement between oscillometric and direct blood pressure monitors in anesthetized dogs and evaluated the ability of the oscillometric method to detect MAP <60 mmHg. Forty client-owned dogs, three months to 14 years old, 4.6-50.2 kg, under general anesthesia were studied. Systolic (SAP), mean (MAP) and diastolic (DAP) arterial pressures were measured directly via an arterial catheter and with an oscillometric cuff (Cardell Touch monitor). Paired values were compared with mixed effect models. Bias and limits of agreement (LOA) were calculated. The sensitivity and false negative rate to detect hypotension (invasive MAP <60 mmHg) using an oscillometric MAP <60 and < 70 mmHg were calculated. A receiver operating characteristics (ROC) curve was constructed and the area under the curve calculated. SAP and DAP differed between methods (both P < 0.001), but MAP did not (P = 0.5). Bland-Altman plots showed small biases but wide LOA for all variables. The sensitivity to detect hypotension was 40% with a false negative rate of 60% when using an oscillometric MAP <60 mmHg, and 68% and 32%, respectively, with a MAP <70 mmHg. The area under the ROC curve for MAP was 0.82. While the oscillometric MAP did not differ from invasive values, the device failed to recognize hypotensive events when 60 mmHg was used as the threshold to detect hypotension. Higher MAP values increased the ability to correctly recognize hypotension, but at the expense of a higher incidence of false positives.

Retrospective investigation of an association between high-dose buprenorphine and perpetuation of post-anesthesia hyperthermia in cats following ovariohysterectomy.

OBJECTIVES: We evaluated a potential association between the administration of high-dose buprenorphine and perpetuation of hyperthermia in cats following ovariohysterectomy (OVH). We hypothesized that buprenorphine 0.24 mg/kg subcutaneously (SC) would result in longer-lasting postoperative hyperthermia in cats vs a group receiving morphine 0.1 mg/kg SC. METHODS: Anesthetic records from cats admitted for OVH as part of surgical exercises for second year veterinary medicine students in 2018 and 2019 were collected. All cats were sedated with dexmedetomidine 20 µg/kg and morphine 0.1 mg/kg intramuscularly. Anesthesia was induced with propofol and maintained with isoflurane in oxygen. At extubation, cats received morphine 0.1 mg/kg SC in 2018 and buprenorphine 0.24 mg/kg SC in 2019. Temperature was measured rectally prior to sedation, esophageally during anesthesia and rectally at 1, 4 and 16-20 h after extubation. Demographic data and temperature prior to administration of postoperative opioids were compared with t-tests. The effects of treatment (opioids) and time on postoperative rectal temperature and on the incidence of hyperthermia (temperature >39.2°C) were evaluated with mixed and generalized linear mixed-effect models. Significance was set at P <0.05. RESULTS: There were no differences in demographic characteristics between treatment groups (all P ⩾0.2). Intraoperative esophageal temperature was lower in cats scheduled to receive morphine (mean ± SD 36.6 ± 0.2) than in those receiving buprenorphine (36.9 ± 1.0) (P <0.0001). Postoperative temperature was higher for cats receiving buprenorphine than for those receiving morphine (P <0.0001). The incidence of hyperthermia 16-20 h after opioid administration was 56% for morphine and 73% for buprenorphine (P = 0.03). CONCLUSIONS AND RELEVANCE: Buprenorphine 0.24 mg/kg SC for postoperative analgesia in cats was associated with hyperthermia that persisted for 16-20 h after administration, and the incidence of hyperthermia for this group was higher than in the cats that received morphine 0.1 mg/kg SC.

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.

Sedative and physiologic effects of tiletamine-zolazepam following buccal administration in cats.

OBJECTIVES: The aim of this study was to describe the sedative and some physiological effects of tiletamine-zolazepam following buccal administration (BA) in cats. METHODS: Seven healthy spayed European shorthair cats (three males, four females) were studied twice in this randomized, blinded, crossover study. Each cat received two doses of tiletamine-zolazepam by BA: the low-dose (LD) group consisted of 5 mg/kg of each drug, and the high-dose (HD) group consisted of 7.5 mg/kg of each. Baseline systolic blood pressure (SAP), heart rate (HR), respiratory rate (RR) and a sedation score were recorded prior to administration of each treatment. The same variables plus the percentage of hemoglobin saturated with oxygen as measured by pulse oximetry (SpO2) were recorded at predefined intervals for the next 2 h. RESULTS: All cats completed the study. No retching or vomiting were observed. Hypersalivation was observed in 0/7 and 3/7 for LD and HD groups, respectively (P = 0.2). There were significant changes in scores over time for posture, response to clippers and response to manual restraint for both groups, without differences between groups. RR, HR and SAP changed significantly over time. SAP and RR were significantly lower for the HD than for the LD group. No values for hemoglobin saturation <95% were observed. CONCLUSIONS AND RELEVANCE: BA of tiletamine-zolazepam at the doses studied here is a simple and effective method for chemical restraint in cats, where the LD group had a lower impact on SAP and RR than the HD group.

A comparison between maropitant and metoclopramide for the prevention of morphine-induced nausea and vomiting in dogs.

Morphine is widely used as a preanesthetic agent in dogs, but it often produces signs of nausea and vomiting. Maropitant (MRP) and metoclopramide (MCP) prevent emesis attributable to the opioid agent apomorphine in dogs. We evaluated the antiemetic efficacy and the discomfort in response to SQ injection of MRP [1 mg/kg body weight (BW)], MCP (0.5 mg/kg BW), and normal saline (SAL; 0.1 mL/kg BW) administered to 63 dogs, 45 minutes prior to morphine (0.5 mg/kg BW) and acepromazine (0.05 mg/kg BW). Dogs were observed for signs of nausea (ptyalism, lip licking, and increased swallowing) and vomiting for 30 minutes after morphine/acepromazine. The incidence of emesis was 0% for MRP, 38% for MCP, and 71% for SAL (P < 0.001). The incidence of signs of nausea was not different between groups. Discomfort due to injection was higher after MRP (48%), than after MCP (9.8%) and SAL (4.8%) (P < 0.001).

Comparaison entre le maropitant et la métoclopramide pour la prévention de nausée et des vomissements induits par la morphine chez les chiens. La morphine est largement utilisée comme agent pré-anesthésique chez les chiens, mais elle produit souvent des symptômes de nausée et de vomissements. Le maropitant (MRP) et la métoclopramide (MCP) préviennent le vomissement causé par l'agent opioïde apomorphine chez les chiens. Nous avons évalué l'efficacité antiémétique et l'inconfort en réponse à une injection SC de MRP [1 mg/kg de poids corporel (PC)], de MCP (0,5 mg/kg PC) et d'une solution saline normale (SAL; 0,1 mL/kg PC) administrée à 63 chiens, 45 minutes avant la morphine (0,5 mg/kg PC) et l'acépromazine (0,05 mg/kg PC). Les chiens ont été observés pour détecter des signes de nausée (ptyalisme, lèchement des lèvres et déglutition accrue) et le vomissement pendant 30 minutes après l'administration de morphine/acépromazine. L'incidence du vomissement était de 0 % pour MRP, de 38 % pour MCP et de 71 % pour SAL (P < 0,001). L'incidence des signes de nausée n'était pas différente entre les groupes. L'inconfort attribuable à l'injection était supérieur après MRP (48 %) par rapport à celui après MCP (9,8 %) et SAL (4,8 %) (P < 0,001).(Traduit par Isabelle Vallières).

Maropitant administered orally 2-2.5 h prior to morphine and dexmedetomidine reduces the incidence of emesis in cats.

Objectives The main goal of this study was to test the antiemetic effects of maropitant administered orally 2-2.5 h prior to morphine and dexmedetomidine in cats. Methods Eighty-three healthy female cats were randomized to receive maropitant (8 mg orally; n = 39) or no treatment (control; n = 44), 2-2.5 h prior to morphine 0.1 mg/kg and dexmedetomidine 20 µg/kg intramuscularly. The incidence of sialorrhea, lip licking, retching and vomiting were recorded after morphine/dexmedetomidine injection. Results There were no differences between groups in terms of age or weight. The treated group received a mean ± SD dose of maropitant of 2.9 ± 0.6 mg/kg. The incidence of sialorrhea and lip licking was no different between groups. The incidence of retching (control 36% vs maropitant 13%; P = 0.012) and emesis (control 32% vs maropitant 13%; P = 0.03) was significantly reduced in cats treated with maropitant. Conclusions and relevance Maropitant 8 mg (total dose) administered orally 2-2.5 h prior to morphine and dexmedetomidine significantly reduced, but did not eliminate, the incidences of retching and vomiting. Maropitant did not decrease the occurrence of sialorrhea and lip licking, signs that may be indicative of nausea. Maropitant might be useful for morning administration to prevent emesis in outpatient cats requiring sedation or anesthesia; however, dose regimens or interval of administration might require improvement.

Speed of reversal of vecuronium neuromuscular block with different doses of neostigmine in anesthetized dogs.

OBJECTIVES: Neostigmine is routinely used to reverse non-depolarizing neuromuscular block. Given its indirect mechanism, a plateau may exist whereby increasing doses of neostigmine do not result in clinical benefit. This study was designed to measure the speed of reversal of vecuronium-induced neuromuscular block in isoflurane-anesthetized dogs after the administration of three doses of neostigmine as used in clinical practice. STUDY DESIGN: Prospective, crossover, randomized study. ANIMALS: Seven adult, mixed-breed dogs with a mean ± standard deviation (SD) age of 2.0 ± 0.8 years and weight of 19.1 ± 9.1 kg. METHODS: Dogs were anesthetized on three occasions with isoflurane and administered vecuronium (0.1 mg kg-1) intravenously (IV). The train-of-four (TOF) ratio was measured on the pelvic limb with acceleromyography. When the second twitch of the TOF had returned spontaneously, atropine (0.03 mg kg-1) and neostigmine (0.02, 0.04 or 0.07 mg kg-1) were administered IV. Time to reach a TOF ratio of ≥0.9 after neostigmine administration was recorded. RESULTS: Increasing the dose of neostigmine from 0.02 mg kg-1 to 0.04 mg kg-1 and 0.07 mg kg-1 resulted in significant reductions in mean ± SD reversal times (10.5 ± 2.3, 7.4 ± 1.1 and 5.4 ± 0.5 minutes, respectively) (p < 0.0001) and smaller coefficients of variation (22%, 15% and 10%, respectively). CONCLUSIONS AND CLINICAL RELEVANCE: Increasing the dose of neostigmine from 0.02 mg kg-1 to 0.04 mg kg-1 and 0.07 mg kg-1 produced faster and less variable reversal of vecuronium-induced neuromuscular block in isoflurane-anesthetized dogs. No ceiling effect was observed at this dose range.

Evaluation of neostigmine antagonism at different levels of vecuronium-induced neuromuscular blockade in isoflurane anesthetized dogs.

Residual neuromuscular block (NMB) during recovery from general anesthesia may be minimized by antagonizing NMB with neostigmine. We examined neostigmine for restoring neuromuscular function when administered at 2 levels of vecuronium-induced NMB in dogs. Eight healthy adult dogs received vecuronium 0.1 mg/kg body weight (BW), IV, during isoflurane anesthesia. Recovery from vecuronium occurred spontaneously (control group; C), or was enhanced with neostigmine, 0.04 mg/kg BW, IV, administered when 2 (N2) or 4 (N4) responses to train-of-four (TOF) stimulation were first observed. Duration of NMB was significantly shorter for N2 and N4 than for C. The period of complete NMB was equal for all groups; differences were observed during the recovery phase of NMB. Time of neostigmine-enhanced recovery was significantly shorter for N4 than N2, but overall duration of NMB was not reduced. Recovery from NMB was faster with neostigmine. There is no clinical advantage in delaying neostigmine administration once 2 responses to TOF are present.

Évaluation de l'antagonisme de la néostigmine à différents niveaux de blocage neuromusculaire induits par vécuronium chez les chiens anesthésiés à l'isoflurane. Le bloc neuromusculaire résiduel (BNR) durant le réveil de l'anesthésie générale peut être minimisé en antagonisant le BNR avec de la néostigmine. Nous avons examiné la néostigmine pour le rétablissement de la fonction neuromusculaire lors de l'administration à 2 niveaux de BNR induit par le vécuronium chez les chiens. Huit chiens adultes en santé ont reçu du vécuronium 0,1 mg/kg poids corporel (PC), IV, durant l'anesthésie à l'isoflurane. Le réveil de vécuronium s'est produit spontanément (groupe témoin; C) ou a été rehaussé avec de la néostigmine, 0,04 mg/kg PC, IV, administrée lorsque des réponses 2 (N2) ou 4 (N4) à une stimulation de quatre impulsions «train-of-four¼ (TOF) ont d'abord été observées. La durée du BNR a été significativement écourtée pour N2 et N4 par rapport à C. La période du BNR complet a été égale pour tous les groupes; les différences ont été observées durant la phase de réveil de BNR. La durée du réveil rehaussée à la néostigmine a été significativement écourtée pour N4 par rapport à N2, mais la durée globale de BNR n'a pas été réduite. Le réveil du BNR a été plus rapide avec la néostigmine. Il n'y a pas d'avantage clinique à retarder l'administration de la néostigmine une fois que 2 réponses à TOF sont présentes.(Traduit par Isabelle Vallières).