Few data about the electroencephalogram and its calculated indices, such as the bispectral index (BIS), have been reported in rabbits. We aimed to evaluate whether a clinically stable anesthesia was mirrored by consistent and stable BIS values and to investigate the effects of modified cerebral blood supply, due to bilateral carotid clamping and re-opening, on BIS values. We also investigated the effects of fentanyl, as an antinociceptive drug, on the BIS. Sixty-eight rabbits undergoing general anesthesia for surgical creation of carotid bifurcation aneurysms were enrolled. The BIS values were recorded at nine selected time points (TPs) during each procedure and before and after fentanyl administration. The BIS values over time were compared with two-way repeated-measures analysis of variance followed by Tukey test, while the Wilcoxon signed rank test was performed to compare values at clamping and re-opening of the carotids as well as before and after fentanyl administration. The BIS values were significantly lower during anesthesia than at the end of anesthesia and at tracheal extubation; no significant differences were found among other TPs. Adequate depth of anesthesia was mirrored by consistent BIS values among rabbits, and alteration of cerebral blood supply did not modify BIS values, except once. Following fentanyl, BIS values did not change in a clinically relevant way.

Buprenorphine has gained widespread popularity for use in rabbits, while much less is known about methadone. Our aim was to compare sedative, analgesic, and respiratory effects of methadone and buprenorphine as part of balanced anaesthesia. Forty-eight female New Zealand white rabbits undergoing calvaria defects were randomly equally assigned to receive either 0.03 mg kg⁻¹ of buprenorphine (group B) or 0.3 mg kg⁻¹ of methadone (group M) in combination with 15 mg kg⁻¹ of ketamine and 0.1 mg kg⁻¹ of dexmedetomidine SC. Fifteen minutes later, sedation was scored. A laryngeal mask was placed, and inhalational anaesthesia started. Rescue intraoperative analgesia was administered based on autonomic variations. Arterial blood gases were analysed intra- and postoperatively. Postoperative analgesia was administered if the Rabbit Grimace Scale (RbtGS) score was ≥4. The Mann–Whitney test, t-test, and relative risk followed by chi-square test were used to compare the treatment groups. Deeper sedation was observed in rabbits of group M than in those of group B. Rescue analgesia was administered intraoperatively to seven animals in group B and five in group M (p = 0.739) and postoperatively to three in group B and twelve in group M (p = 0.013). Rabbits of both groups showed short-term respiratory acidosis. RbtGS scores indicated better and longer analgesia in group B compared to group M.

Background: Both invasive and non-invasive blood pressure measuring methods are used in clinical and experimental work in veterinary medicine and several studies validating these methods are published. The aim of this study was to assess the level of agreement between non-invasive and invasive arterial blood pressure measurements within a wide range of blood pressures in sheep. Six adult Texel-cross female sheep were included. Anaesthesia was induced with IV propofol (4–8 mg/kg) and maintained with sevoflurane in 50% oxygen and air. Blood pressure measurements were simultaneously obtained using both invasive methods (electronic pressure transducer (EPT) connected to the auricular and carotid arteries, and aneroid manometer connected to the auricular artery) and non-invasive methods (the oscillometric device (OD) and Doppler). Carotid artery EPT was considered the ‘gold standard’ to which other methods were compared. The agreement between the two methods was evaluated with the Bland-Altman method, in conditions of normotension, hypertension (MAP > 160 mmHg, induced with phenylephrine), and hypotension (MAP < 50 mmHg, induced with acepromazine). The devices were evaluated using the American College of Veterinary Internal Medicine guidelines. Results: Carotid MAP values ranged from 37 to 192 mmHg. Mean bias and limits of agreement were − 2.8 mmHg and − 11–5.4 mmHg for the auricular EPT MAP; 5.1 mmHg and − 12.2–22.3 mmHg for the aneroid manometer MAP; − 2.7 mmHg and − 23.9–18.6 mmHg for the OD MAP; − 1.5 mmHg and − 20.1–23.2 mmHg for the Doppler SAP; respectively. Correlation coefficients for all methods were > 0.95. Conclusions: Doppler SAP and OD MAP demonstrated acceptable accuracy over a broad blood pressure range, supporting their utility for sheep as surrogate of invasive methods of measuring blood pressure. Auricular EPT was the best surrogate of central arterial pressure to be used in clinical conditions.

The pain associated with experimental myocardial infarction in pigs has never been investigated. We aimed at assessing pain and its correlation with myocardial damage. Twenty-four Göttingen minipigs undergoing closed chest myocardial infarction followed by coronary reperfusion under general balanced anaesthesia were included in the trial. Pain was assessed through mechanical and thermal thresholds, sensitivity to Von Frey filaments and behavioural indicators before (Pre MI), the day after (Post MI) and at the study endpoint (Post MI-endpoint). Over time differences in mechanical thresholds (MT) and thermal thresholds (TT) were assessed using one-sample t-test and their correlations with troponin I/cytokines using logistic regression. In four minipigs at Post MI acute pain requiring analgesia was identified. Pain thresholds decreased significantly at Post MI (MT: 51 [35.6; 74] TT: 44.8 [42.7; 48.7]) and Post MI-endpoint (MT: 47.5 [35; 64.3]; TT: 44.3 [43.1; 48.6]) compared to Pre MI (MT: 72 [53.4; 84], TT: 46.3 [43.8; 53.8]). The response to von Frey filaments remained sporadic. Troponin I highly increased at Post MI, but no correlations with pain thresholds were found. Following balanced anaesthesia, acute pain had low incidence and mild to moderate intensity. Somatic hyperalgesia remained until the study endpoint, but its relevance remains to be unravelled.