Speed of induction of anaesthesia in dogs administered halothane, isoflurane, sevoflurane or propofol in a clinical setting

A dose characterization study evaluating the pharmacodynamics and safety of a concentrated alfaxalone solution (4%) as an intramuscular sedative in dogs

Alfaxalone is a commonly employed veterinary anaesthetic induction and sedation agent. A 4% w/v preserved, aqueous formulation of alfaxalone 'RD0387' (A4%) has recently been developed. To evaluate the sedative effects of A4%, three doses, 5 mg kg-1 (A5); 7.5 mg kg-1 (A7.5) and 10 mg kg-1 (A10) were administered intramuscularly into the epaxial musculature of six healthy adult mixed-breed dogs in an experimental, randomized, blinded, crossover study. Sedation time variables, quality of sedation (including onset of sedation and recovery), physiological variables, response to cephalic vein catheterization and frequency of undesirable events were recorded. Continuous variables were analysed between treatments (one-way ANOVA or restricted maximum likelihood modelling) and within treatments compared with baseline (Tukey's test). Categorical data were analysed between treatments (Kruskal-Wallis' test) and within treatments from baseline (Dunn's test). Significance was set at p < .05. All dogs became sedated (laterally recumbent) and sedation onset was significantly faster in groups A7.5 (9.8 ± 5.3 min) and A10 (9.1 ± 5.6 min) compared to A5 (25.6 ± 16.1 min) (p = .033, p = .027, respectively). Duration of sedation was significantly longer in A10 (168.5 ± 70.6 min) and A7.5 (143.8 ± 58 min) compared to A5 (63.8 ± 28.2 min) (p = .005 and p = .003, respectively). Dogs in A10 had a superior quality of onset of sedation compared to A5 (p = .028). Sedation scores and quality of recovery from sedation were not significantly different between doses. Two dogs (2/6) in A5 were insufficiently sedated for cephalic catheterization. Ataxia was the most frequently observed undesirable event with an overall frequency of 78% (14/18) and 89% (16/18) during sedation onset and recovery, respectively. Overall, A4% administered IM in dogs at 7.5 and 10 mg kg-1 resulted in sufficient sedation for IV catheterization in dogs. To improve the speed and quality of the sedation, it is recommended that future research focuses on combining A4% with other sedative or analgesic drugs.

Comparison of the effect of sedation and general anesthesia on pattern and flash visual evoked potentials in normal dogs

Background

Visual evoked potentials (VEPs) can provide objective functional assessment of the post-retinal visual pathway. This study compared the effects of sedation (butorphanol and dexmedetomidine) and general anesthesia (propofol and sevoflurane) on pattern and flash VEPs. Dogs (n = 13) underwent sedation or anesthesia and VEPs were obtained from 3 subcutaneous recording electrodes placed on the head (O1, Oz, O2).

Results

Pattern VEPs could only be recorded under sedation and a maximum of 3 peaks were identified (N75, P100, N135). Flash VEPs could be recorded under both sedation and anesthesia and a maximum of 5 peaks were identified (N1, P1, N2, P2, N3). The latency of the N1 peak and the baseline-N1 amplitude were significantly longer under general anesthesia.

Conclusion

Visual evoked potentials should be preferentially recorded in dogs sedated with dexmedetomidine and butorphanol, regardless of the stimulus.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03375-5.

Scoping review of quality of anesthetic induction and recovery scales used for dogs

OBJECTIVE

To compare, describe and assess the level of validation of all instruments measuring quality of induction and recovery from anesthesia in dogs.

DATABASES USED

A search was performed using the electronic database PubMed to find articles containing an induction quality scale, a recovery quality scale or both in dogs. Articles not directly accessible through PubMed were obtained through the Auburn University Library website and Google Scholar. The phrases 'induction scoring systems dogs', 'recovery scoring systems dogs', 'anesthetic induction score dogs', and 'anesthetic recovery score dogs' were used for searches using the 'best match search' function. The time frame searched was from 1980 to May 2020. The search was conducted from March 2020 to May 2020.

CONCLUSIONS

A thoroughly tested and validated scale for measuring the quality of induction and recovery does not exist in the current veterinary literature. A large disagreement exists between studies on the use of induction and recovery scales, and many have reported inconsistent results with current instruments. It is recommended that an induction and recovery scale intended for wide-scale use be constructed and tested extensively for psychometric validation and reliability.

A survey of dog and cat anaesthesia in a sample of veterinary practices in New Zealand

AIMS

To survey current anaesthesia practices for dogs and cats in small and mixed animal practices in New Zealand in order to improve anaesthesia education.

METHODS

A questionnaire was sent to 440 small and mixed animal practices, including questions regarding the type of practice, preanaesthetic examination, anaesthetic drugs and management, anaesthetic machines, monitoring and topics of interest for continuing professional development.

RESULTS

Responses were obtained from 113/440 (26%) practices, with 78 (69%) respondents from small and 35 (31%) from mixed animal practices. A preanaesthetic physical examination was carried out by >95% of respondents and premedication was usually given to dogs (112/113; 99%) and cats (95/113; 85%). Acepromazine was the preferred sedative for dogs and cats, with morphine or buprenorphine. Propofol and alfaxalone were the preferred induction agents, and isoflurane was preferred for maintenance in both dogs and cats. A venous catheter was usually placed for anaesthesia in dogs (59/113; 52%), but less so in cats (39/113; 35%). Perioperative fluid was administered at 10 mL/kg/hour by 62/110 (56%) respondents. Intubation was usually used for anaesthesia in dogs (111/112; 99%), and cats (87/112; 78%). Almost 40% of respondents usually administered supplementary oxygen if patients were not intubated. Local analgesia was used by 69/111 (88%) respondents sometimes or always if applicable. Morphine or buprenorphine, and meloxicam were common choices for post-operative analgesia after neuter surgery in dogs and cats. A semiclosed (non-rebreathing) system was used in animals weighing <10 kg, and a Mapleson E or F non-rebreathing circuit was used by 66/109 (61%) practices. Only 15/111 (14%) practices had a ventilator in their practice. A dedicated anaesthetist was usually used by 104/113 (92%) practices, and apnoea alarms, pulse oximeters, thermometers and oesophageal stethoscopes were the main monitoring devices available in practices. Loco-regional block, pain management, and anaesthetic drugs were the main topics of interest for continuing education.

CONCLUSIONS AND CLINICAL RELEVANCE

Responses by the veterinarians taking part in this survey indicated that they had a reasonably good standard of anaesthetic practice. A physical examination was carried out preanaesthesia, and premedication including analgesia was routinely administered to most patients. A dedicated anaesthetist usually monitored patients and most respondents reported they had access to basic anaesthetic monitoring equipment. Areas where changes could lead to improved anaesthetic practice were increased use of I/V catheterisation, endotracheal intubation, and supplementary oxygen, and reduced I/V fluid rates.

The cardiovascular effects of sevoflurane and isoflurane after premedication of healthy dogs undergoing elective surgery

Sevoflurane and isoflurane are commonly used in veterinary anesthesia. The objective of this prospective, randomized, open-label clinical study was to compare the cardiovascular effects of sevoflurane and isoflurane via direct arterial blood pressure measurements and the lithium dilution cardiac output (LDCO) on premedicated healthy dogs undergoing elective tibial plateau leveling osteotomy (TPLO). Nineteen client-owned dogs were included. All dogs were premedicated with hydromorphone (0.05 mg/kg IV and glycopyrrolate 0.01 mg/kg subcutaneously). Ten dogs were anesthetized with sevoflurane and nine dogs were anesthetized with isoflurane. Eighteen dogs were instrumented with a dorsal pedal arterial catheter, and one dog had a femoral arterial catheter. All dogs had continuous, direct systolic (SAP), diastolic (DAP), and mean arterial (MAP) blood pressure readings as well as heart rate (HR), cardiac output (CO), cardiac index (CI), systemic vascular resistance (SVR), systemic vascular resistance index (SVRI), stroke volume variation (SVV), and pulse pressure variation (PPV) recorded q 5 min during the surgical procedure. There was no significant statistical difference in all parameters between the sevoflurane and isoflurane treatment groups. Both sevoflurane and isoflurane inhalant anesthetics appear to have similar hemodynamic effects when used as part of a multimodal anesthetic protocol in premedicated healthy dogs undergoing an elective surgical procedure.

Clinical effects of isoflurane and sevoflurane in lambs

OBJECTIVE

To compare isoflurane and sevoflurane in lambs undergoing prolonged anaesthesia for spinal surgery.

STUDY DESIGN

Prospective randomised clinical study.

ANIMALS

Eighteen Scottish blackface lambs 3-6 weeks of age and weighing 10-17 kg.

METHODS

After intramuscular medetomidine, anaesthesia was induced and maintained with either isoflurane (group I) or sevoflurane (group S) delivered in oxygen. Meloxicam, morphine, a constant rate infusion of ketamine and atracurium were given intravenously (IV) during surgery. Lungs were ventilated to maintain normocapnia. with peak inspiratory pressures of 20-25 cmH(2) O. Ephedrine or dextran 40% was administered when mean arterial pressure (MAP) was <55 mmHg. Intrathecal morphine, and IV meloxicam and edrophonium were injected before recovery. Time to loss of palpebral reflex (TLPR) upon induction, cardiorespiratory variables, time at first swallowing and other movement, tracheal extubation, vocalisation, spontaneous head lifting (>1 minute), reunion with the ewe, and the number of MAP treatments were recorded. Statistical analysis utilised anova, Mann-Whitney, t-test or Pearson's correlation test as relevant. p < 0.05 was considered significant.

RESULTS

End-tidal carbon dioxide (mean ± SD) was significantly lower in group S (5.5 ± 0.6 kPa) than in group I (5.8 ± 0.5 kPa) while MAP (70 ± 11 mmHg) and diastolic arterial blood pressure (60 ± 11 mmHg) were higher in group S than in group I (65 ± 12 and 54 ± 11 mmHg, respectively). No differences were found with TLPR and MAP treatments. Time (median, range) from end of anaesthesia to ewe-lamb reunion was briefer (p = 0.018) in group S (48, 20-63 minutes).

CONCLUSION

Isoflurane and sevoflurane are both suitable for maintaining general anaesthesia in lambs although sevoflurane, as used in this study, allows a more rapid reunion with the ewe.

CLINICAL RELEVANCE

The principal advantage of sevoflurane over isoflurane during prolonged anaesthesia in lambs is a more rapid recovery.