Evaluation of the nociception-antinociception balance using the Parasympathetic Tone Activity index in dogs anaesthetized for castration.

OBJECTIVE: To evaluate the performance of the Parasympathetic Tone Activity (PTA) index in assessing the nociception-antinociception balance in anaesthetized dogs undergoing castration. STUDY DESIGN: Prospective clinical study. ANIMALS: A group of 22 healthy client-owned dogs. METHODS: The dogs underwent general anaesthesia, with continuous monitoring of mean and instantaneous PTA (PTAm, PTAi), mean arterial pressure and heart rate. The values of these variables were divided according to the occurrence or absence of a haemodynamic reaction (HDR) at different time points: during surgical preparation, cutaneous incision, testicles extraction, cutaneous suture, after fentanyl administration, and after dexmedetomidine administration during recovery. Data were collected initially and 1, 3 and 5 minutes after each time point. The performance of the dynamic variation of the PTA (ΔPTA) to predict HDR or its resolution within 3 or 5 minutes was assessed using receiver operating characteristic (ROC) curves analysis. A p value < 0.05 was considered significant. RESULTS: During HDR, a decrease in PTAi (-34% and -31%) and PTAm (-26% and -30%) occurred at 3 (p = 0.005; p = 0.004) and 5 minutes (p = 0.001), respectively. After fentanyl administration, a decrease in haemodynamic variables occurred with a 45% increase in PTAi (p = 0.004). The ROC curve analysis of pooled data of the ΔPTAi for the prediction of HDR within 3 minutes indicated an area under the curve (AUC) of 0.70 (p = 0.0016) (threshold value: -16%). After fentanyl administration, the ROC curve analysis of ΔPTAi for the prediction of resolution of HDR within 3 minutes indicated an AUC of 0.69 (threshold value: +12%). CONCLUSIONS AND CLINICAL RELEVANCE: The PTAi appears to be an interesting tool to assess the nociception-antinociception balance. However, further studies with a variety of clinical scenarios and anaesthesia protocols are required to conclude on its performance.

Successful Cardiopulmonary Resuscitation in a Sevoflurane Anaesthetized Horse That Suffered Cardiac Arrest at Recovery.

A 17-year-old mare undergoing dental surgery suffered a cardiac arrest while being transferred from the surgical theatre to the recovery box. This complication was diagnosed early, thus allowing a prompt start to the cardiopulmonary resuscitation maneuvers. External thoracic compressions, intermittent positive pressure ventilation, and adrenaline administration were at the core of this successful resuscitation. Although it was not possible to confirm the cause of cardiac arrest in this horse, a Bezold-Jarisch reflex due to potential decrease on venous return because of postural change and drug interactions was hypothesized. Based on this report, it appears advisable to smoothly change the position of anaesthetized patient; furthermore, the administration of drugs affecting cardiovascular hemodynamics or sympatho-vagal balance to animals while changing their recumbency should be avoided.

Alfaxalone for total intravenous anaesthesia in bitches undergoing elective caesarean section and its effects on puppies: a randomized clinical trial.

OBJECTIVE: To evaluate the effects and reliability of alfaxalone constant rate infusion (CRI) in comparison to isoflurane to maintain anaesthesia in bitches undergoing elective caesarean section. STUDY DESIGN: Prospective, randomized, 'blinded' clinical trial. ANIMALS: Twenty-two client-owned bitches and 94 puppies. METHODS: Bitches were randomly assigned to receive an alfaxalone CRI [0.2 mg kg(-1)  minute(-1) intravenously (IV), and once the last puppy was delivered, the dose was halved; n = 11] or 2% (vaporizer dial setting) isoflurane (n = 11) for maintenance of anaesthesia. All dogs were induced with alfaxalone (3 mg kg(-1) ) IV. Additional alfaxalone (0.3 mg kg(-1) IV) was administered if the depth of anaesthesia was inadequate and the total dose was calculated. Bitches were mechanically ventilated. Analgesia was administered after the delivery of puppies. Physiological variables were recorded every 5 minutes. The bitches' recovery times were also recorded. Quality of induction and recovery were evaluated. Puppies' vigour was evaluated with a modified Apgar score at 5 and 60 minutes after birth. Puppies' survival rates at 24 and 48 hours and at 15 days were recorded. Data were analysed using an anova, Student's t-test or Wilcoxon rank-sum test. RESULTS: The rescue dose of alfaxalone was higher (p = 0.01); bitches' recoveries were longer (p < 0.001) and puppies' Apgar scores were significantly lower at 5 and 60 minutes (p < 0.001 and p = 0.003, respectively) with alfaxalone than with isoflurane. However, no significant differences were found for puppies' survival between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Alfaxalone CRI seems to be a possible protocol for puppies and bitches undergoing elective caesarean sections. However, bitches recovered more slowly and puppy Apgar scores were lower in comparison to isoflurane.

Effect of Pre- and Postoperative Phenylbutazone and Morphine Administration on the Breathing Response to Skin Incision, Recovery Quality, Behavior, and Cardiorespiratory Variables in Horses Undergoing Fetlock Arthroscopy: A Pilot Study.

This prospective blinded randomized study aimed to determine whether the timing of morphine and phenylbutazone administration affects the breathing response to skin incision, recovery quality, behavior, and cardiorespiratory variables in horses undergoing fetlock arthroscopy. Ten Standardbred horses were premedicated with acepromazine (0.04 mg kg(-1) IM) and romifidine (0.04 mg kg(-1) IV). Anesthesia was induced with diazepam (0.05 mg kg(-1)) and ketamine (2.2 mg kg(-1)) IV at T0. Horses in group PRE (n = 5) received morphine (0.1 mg kg(-1)) and phenylbutazone (2.2 mg kg(-1)) IV after induction and an equivalent amount of saline after surgery. Horses in group POST (n = 5) received the inversed treatment. Anesthesia was maintained with isoflurane 2% in 100% oxygen. Hypotension (mean arterial pressure <60 mmHg) was treated with dobutamine. All horses breathed spontaneously. Dobutamine requirements, respiratory rate (f R), heart rate (HR), mean arterial blood pressure, end-tidal CO2, inspired (i) and expired (e) tidal and minute volume (V T and [Formula: see text]), inspiratory time (IT), and the inspiratory gas flow (V Ti/IT) were measured every 5 min. Data were averaged during four 15 min periods before (P1 and P2) and after the incision (P3 and P4). Serial blood-gas analyses were also performed. Recoveries were unassisted, video recorded, and scored by three anesthetists blinded to the treatment. The postoperative behavior of the horses (25 demeanors), HR, and f R were recorded at three time points before induction (T0-24 h, T0-12 h, and T0-2 h) and six time points after recovery (TR) (TR + 2, 4, 6, 12, 24, 48 h). Data were compared between groups using a Wilcoxon test and within groups using a Friedman test or a Kruskal-Wallis signed-rank test when applicable. Tidal volumes (V Te and V Ti) were higher in PRE than in POST during all the considered periods but the difference between groups was only significant during P2 (V Te in mL kg(-1) in PRE: 13 [9, 15], in POST: 9 [8, 9], p = 0.01). None of the other variables were significantly different between and within groups. Under our experimental conditions, skin incision did not affect respiratory variables. Administration of pre- versus postoperative phenylbutazone and morphine did not influence recovery quality, HR, f R, or animal behavior.