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Autonomic nervous system (ANS) activity can modify cardiovascular parameters in response to nociceptive stimuli or drugs in anesthetized animals. The aim of this study was to determine if a surgical nociceptive stimulus and morphine, ketamine, and dobutamine administration would modify ANS activity observed as a change in the mean parasympathetic tone activity (PTAm) in anesthetized horses. In 20 anesthetized horses, heart rate (HR), mean arterial pressure (MAP), and PTAm were monitored before and 1, 3, and 5 min after surgical incision, and before and 10 min after the administration of morphine (0.2 mg/kg IV). If nystagmus or spontaneous ventilation was observed, ketamine (0.5 mg/kg IV) was given, and the three variables were registered before and 3 and 5 min afterward. If MAP reached ≤ 62 mmHg, a dobutamine infusion was administered, and the three variables were recorded before and 5 min after starting/increasing the infusion (0.25 μg/kg/min IV every 5 min). The three variables were registered before and 1, 3, and 5 min after a PTAm decrease of ≥ 20%, HR increase of ≥ 10%, or MAP increase of ≥ 20%. The PTAm decreased 3 min after the administration of ketamine and 1 min after a PTA event. The surgical incision, dobutamine, and morphine did not modify PTAm. The absence of changes in ANS activity after the nociceptive stimulus and lack of correlation between PTAm and HR or MAP suggest that PTAm is a poor indicator of sympathetic activation under the study conditions. Ketamine seems to affect ANS activity by decreasing PTAm.

BackgroundThe bispectral index (BIS) has been evaluated as an indicator of central nervous system (CNS) depression in horses during general anaesthesia. The spectral entropy is another electroencephalographic device and it has not been evaluated yet in horses.ObjectivesTo determine if spectral entropy can assess anaesthetic depth during the different phases of anaesthesia, define the value of state and response entropy during surgical plane of anaesthesia and compare them with BIS.Study designClinical, prospective, non‐blinded observational study.MethodsThirty‐five horses ASA I or II undergoing scheduled surgical procedure were used. BIS and electromyography (EMG) with a BIS monitor and state and response entropy with a spectral entropy monitor were recorded at baseline after receiving 5 µg/kg bwt i.v. of medetomidine (sedation period), during the anaesthetic maintenance with isoflurane and medetomidine (intraoperative period) and once the trachea was extubated (recovery period). A general linear model for repeated measurements was employed. Correlation and agreement between methods were also assessed. Data are presented as mean ± SD.ResultsState entropy, response entropy and EMG showed significant differences according to the anaesthetic period (P < .001). There was no significant difference in BIS between baseline and sedation period, but there were differences between the remainder of the periods (P < .001). BIS (53.4 ± 11.2) was significantly higher (P < .001) than response entropy (35.1 ± 7.1) and state entropy (27.4 ± 4.8) during surgical plane of anaesthesia. The ICC between BIS and response entropy was 0.56 and between BIS and state entropy was 0.43, without agreement between them.Main limitationsThe need to shave the skin in contact with the sensors and the difficulty in taking measurements during recovery period.ConclusionsSpectral entropy can be used to detect the different periods of an anaesthetic protocol, with the lowest values during the intraoperative period. A low correlation and no concordance were observed between both methods.

This study aimed to determine the performance of the averaged parasympathetic tone activity (PTAm) and its dynamic variation (ΔPTA) to assess intraoperative nociception in relation to heart rate (HR) and direct mean arterial pressure (MAP) in dogs undergoing laparoscopic ovariectomy. This prospective, observational, clinical study included 32 bitches. The PTAm, HR, MAP, and bispectral index (BIS) were assessed before (pre-stimulus), as well as 1 min and 2 min after, four surgical stimuli: insufflation, introduction of trocars, and removal of the left and right ovaries. A two-way ANOVA was performed to compare PTAm, HR, MAP, and BIS data across surgical stimuli. A ≥ 20% drop in PTAm or a ≥ 20% increase in HR and/or MAP regarding the pre-stimulus values was considered a PTAm-drop and/or a hemodynamic response, respectively. The performance of PTAm pre-stimulus, PTAm 1 min, and ΔPTA in predicting the hemodynamic response was assessed by calculation of the area under the receiver operating characteristic (ROC) curve. At insufflation, PTAm decreased after 1 ( p = 0.010) and 2 ( p = 0.045)min, and ΔPTA was different ( p = 0.005) between dogs that presented hemodynamic response and dogs that did not. At PTAm-drop, MAP increased after 1 min ( p = 0.001) and 2 min ( p = 0.001) with respect to pre-stimulus value, whereas HR and BIS did not change. ROC curves showed a threshold value of PTAm pre-stimulus ≤51 to detect hemodynamic response (sensitivity 69%, specificity 52%). The PTAm and ΔPTA only assessed intraoperative nociception during insufflation. The PTAm pre-stimulus association to the hemodynamic response in anaesthetized dogs showed poor sensitivity and no specificity.

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The present case report describes the management of two alpacas undergoing repair of a metatarsal and a distal tibial fracture, respectively. Both animals received ketamine and medetomidine intramuscularly, resulting in deep sedation. Endotracheal intubation was performed, and general anaesthesia was maintained with sevoflurane. An in‐plane ultrasound‐guided sciatic nerve block was performed at the level of the mid‐thigh with bupivacaine 0.5% before surgery as part of the analgesic treatment. Meloxicam was administered. Heart rate, arterial blood pressure and respiratory rate were stable during the surgery, despite the use of a low end‐tidal sevoflurane concentration. No opioids were required intraoperatively. Duration of the anaesthesia was 205 and 255 minutes, respectively. Extubation was performed 12 and 6 minutes after discontinuing sevoflurane administration, respectively. In both cases, regional anaesthesia of the sciatic nerve improved the intraoperative management of alpacas that required surgical treatment for fractures.

This case report describes the anaesthesia of a ram undergoing an exploratory laparotomy, which suffered from respiratory distress during the perioperative period. On the morning of surgery, the animal presented with oedematous ears, most likely caused by a tight-fitting muzzle that had been used for preoperative fasting. After sedation, a mild stridor was heard. During endotracheal intubation, a swollen larynx was observed, and a frothy discharge emerged through the endotracheal tube after placement. Most likely, the tight muzzle caused a partial obstruction of the nostrils, increasing the respiratory effort and causing an increase in the pressure gradient, which provoked laryngeal and pulmonary oedema. Treatment consisted of repeated suctioning of fluid from the endotracheal tube, furosemide, dexamethasone, mechanical ventilation with 100% oxygen during anaesthesia and oxygen supplementation during recovery. Despite moderately low arterial oxygen tension during anaesthesia, the animal recovered uneventfully and did not show further signs of respiratory distress.