A comparison of the duration and quality of recovery from isoflurane, sevoflurane and desflurane anaesthesia in dogs undergoing magnetic resonance imaging

Hypothermia and rewarming times during general anesthesia in Hispaniolan Amazon parrots (Amazona ventralis): A comparative study between isoflurane, sevoflurane and desflurane

OBJECTIVE

To evaluate induced hypothermia and rewarming times in Hispaniolan Amazon parrots (HAP; Amazona ventralis) anesthetized using isoflurane, sevoflurane or desflurane, and to describe selected cardiovascular and respiratory effects.

STUDY DESIGN

Randomized, balanced, crossover experimental study.

ANIMALS

A group of 12 adult HAP.

METHODS

Parrots were premedicated with intramuscular butorphanol (0.5 mg kg-1) and anesthetized with the three inhalants with a 7 day washout period between events. Anesthesia was induced using isoflurane at 4 vol%, sevoflurane at 6 vol% or desflurane 12 vol% carried in oxygen, delivered via face mask. After orotracheal intubation, anesthesia maintenance was with end-tidal concentrations of 1.4-2% (Fe'Iso), 2.4-3% (Fe'Sevo) and 8.5-9.2% (Fe'Des). Hypothermia was defined as an esophageal temperature (BT) below 37.8 °C. External heat support was provided when BT dropped to 37.5 °C. Time for temperature decrease from 38.9 °C to 37.5 °C (T1), time to first increase in BT above 37.5 °C (T2) and time from external heat support to achieving 38.9 °C (T3) were recorded and compared via Friedman tests with post hoc Dunn's test. Heart rate, respiratory rate and end-tidal carbon dioxide, amongst other variables, were evaluated.

RESULTS

All inhalants caused hypothermia (T1): isoflurane, 12 (2-37) minutes [median (range)]; sevoflurane, 12 (4-18) minutes; desflurane, 11.5 (6-24) minutes, with no significant differences between treatments (p > 0.05). T2 was significantly (p = 0.042) longer for sevoflurane than for desflurane but not isoflurane. Transient apnea was observed with all inhalants, including 25% of birds anesthetized with sevoflurane. Second-degree atrioventricular block and ventricular escape beats occurred with all inhalants with hypothermia potentially exacerbating cardiac arrhythmias.

CONCLUSIONS AND CLINICAL RELEVANCE

Hypothermia rapidly developed in butorphanol-sedated HAP anesthetized using isoflurane, sevoflurane or desflurane. Sevoflurane prolonged warming time. Hypothermia may be associated with an increased likelihood of bradyarrhythmia in parrots anesthetized with inhalants.

A randomized clinical trial comparing the efficacy of lidocaine administered intravenously, intranasally or as infraorbital nerve block in dogs undergoing rostral rhinosocopy

OBJECTIVE

To compare the efficacy of lidocaine administered intravenously, intranasally or as an infraorbital nerve block in dogs undergoing rostral rhinoscopy.

STUDY DESIGN

Randomized clinical trial.

ANIMALS

A total of 43 client-owned dogs.

METHODS

After premedication with medetomidine 0.01 mg kg-1 and methadone 0.2 mg kg-1 intramuscularly, anaesthesia was induced with propofol and maintained with isoflurane in oxygen. Dogs were randomly allocated to receive 2 mg kg-1 of 2% lidocaine as a bilateral infraorbital nerve block (INB) via the caudal intraoral approach, via bilateral topical intranasal administration (TIA) or as an intravenous bolus (IVB). At 5 minutes following lidocaine administration, responses to rhinoscopy (RR) and biopsies (RB) were evaluated using a simple scoring system (0: no reaction; 1: reaction). Response to the rhinoscopy in the recovery period (RE) was recorded. Recovery quality was scored using a simple descriptive score. Heart rate, respiratory rate and noninvasive arterial blood pressure were recorded. Intravenous (IV) fentanyl 0.001 mg kg-1 was administered if an increase > 20% in any variable occurred. Gross movement was attenuated using propofol 0.5 mg kg-1 IV. Scores were analysed using the Chi-square test with Monte Carlo method. Cardiorespiratory changes among and overtime between groups were compared using one-way anova and one-way anova for repeated measures, respectively, or the correspondent non-parametric tests; p < 0.05.

RESULT

Of the 43 dogs, 42 completed the study. No statistically significant differences were detected in either physical reactions or changes in cardiorespiratory variables for RR, RB, RE or recovery quality, although RB tended to be higher in group TIA (7/10 versus 1/10 INB and 3/13 IVB).Various cardiorespiratory variables changed overtime within groups.

CONCLUSIONS AND CLINICAL RELEVANCE

In dogs, all three investigated techniques attenuated responses during rostral rhinoscopy in dogs, although INB and IVB were more efficacious when biopsies were taken.

Incidence of and risk factors for poor recovery quality in dogs recovering from general anaesthesia-a prospective case control study

OBJECTIVE

To investigate the incidence of and identify risk factors associated with poor quality of recovery in dogs recovering from general anaesthesia.

STUDY DESIGN

Case controlled study.

METHODS

All dogs undergoing general anaesthesia at the University of Liverpool Small Animal Teaching Hospital between January 2020 and January 2021 were eligible for recruitment. Signalment, anaesthetic case management and a recovery score were recorded. Univariable and multivariable logistic and ordinal logistic regression analysis were used to identify factors which impact incidence of poor quality of recovery.

RESULTS

A total of 247 dogs undergoing general anaesthesia were included. Overall, 72 [29.1%; 95% confidence interval (CI) 23.8%-35.1%] dogs experienced a poor quality recovery. Of these, 40 (55.5%) required sedation to manage behaviours associated with poor recovery. Multivariable logistic regression revealed American Society of Anesthesiologists (ASA) physical status classification of III or higher was associated with a decreased incidence of poor quality recovery [odds ratio (OR) = 0.34, 95% CI 0.12-0.93, p = 0.037] and the use of multiple inhalational anaesthetics during one procedure was associated with an increased incidence of poor quality of recovery (OR = 42.5, 95% CI 3.0-598.3, p = 0.005).

CONCLUSIONS AND CLINICAL RELEVANCE

Poor quality recovery is common in dogs recovering from general anaesthesia and sedation is often required for resolution. It is more likely to occur in healthy veterinary patients (ASA I and II). The use of multiple inhalational anaesthetic agents during one procedure should be discouraged as this may increase the likelihood of poor quality of recovery.

The Effect of a Subsequent Dose of Dexmedetomidine or Other Sedatives following an Initial Dose of Dexmedetomidine on Sedation and Quality of Recovery in Cats: Part I

Dexmedetomidine is an a2-agonist commonly used in veterinary practice. Occasionally, the administered dose of dexmedetomidine may result in insufficient sedation, and an additional dose or drug may be required. The sedative effects of seven different drugs administered at subsequent time points after an initial, insufficient dose of dexmedetomidine were evaluated. Seven adult cats participated in this crossover, blind, randomised study. The groups consisted of two consecutive doses of dexmedetomidine (15 + 10 μg/kg) (DD) or a dose of dexmedetomidine (15 μg/kg) followed by either NS 0.9% (DC-control group), tramadol 2 mg/kg (DT), butorphanol 0.2 mg/kg (DBT), buprenorphine 20 μg/kg (DBP), ketamine 2 mg/kg (DK), or midazolam 0.1 mg/kg (DM). Sedation was evaluated using the Grint sedation scale. In all groups, atipamezole was administered at the end of the evaluation, and recovery was assessed using the Lozano and Sams recovery scales. The DC and DM groups exhibited minimal sedative effects. The maximum sedative effect was observed in the DD and DK groups, while sedation in the DD and DK groups was significantly higher compared to the DC group. Recovery in all groups was uneventful, except in the DM group, where it was prolonged and difficult, although no statistically significant difference was detected. Therefore, insufficient sedation with dexmedetomidine can be enhanced by a subsequent dose of dexmedetomidine, ketamine, or butorphanol, whereas the addition of midazolam reduces sedation and prolongs recovery.

Effects of propofol alone or in combination with ketamine on intraocular pressure in unpremedicated dogs

OBJECTIVE

To determine the effects of propofol (P) alone and in combination with ketamine (KP) at ratios of 1:1, 1:2, and 1:3 on intraocular pressure (IOP) in unpremedicated dogs.

ANIMALS STUDIED

A total of 28 cross-bred healthy dogs.

PROCEDURES

Dogs were randomly assigned to one of four groups (n = 7 per group) to receive intravenous P or KP at 1:1, 1:2, and 1:3 ratios, respectively. The infusion was administered at 0.6 mg/kg/min for 60 min. IOP, cardiorespiratory variables, rectal temperature (RT), and pedal reflex were recorded every 5 min for 60 min, starting from baseline (BL).

RESULTS

There was a statistically significant increase in IOP in all groups: P (p = .011), KP 1:1 (p = .003), KP 1:2 (p = .023), and KP 1:3 (p = .008). The IOP increase was less pronounced in the KP 1:2 group and was only significant (p = .023) at T45 compared with BL. A significant correlation was observed between IOP and SpO2 in P (r = -.215, p = .02), KP 1:2 (r = -.579, p < .01), and KP 1:3 (r = -.402, p < .01) groups. IOP significantly increased due to decreased SpO2 below 86.5% (p < .05).

CONCLUSIONS

Propofol alone and in combination with ketamine may increase preexisting IOP in unpremedicated dogs. SpO2 levels below 86.5% may trigger an increase in IOP. Administering KP in a 1:2 ratio at an infusion rate of 0.6 mg/kg/min does not significantly alter IOP for under 45 min in unpremedicated dogs with sufficient oxygenation.

Influence of Constant Rate Infusions of Fentanyl Alone or in Combination With Lidocaine and Ketamine on the Response to Surgery and Postoperative Pain in Isoflurane Anesthetized Dogs Undergoing Unilateral Mastectomy: A Randomized Clinical Trial

The aim of this study was to compare the effects of constant rate infusions (CRI) of fentanyl alone or combined with lidocaine and ketamine (FLK), on physiological parameters, isoflurane requirements and the number of postoperative analgesic rescues in dogs undergoing unilateral mastectomy. Twenty-two dogs were premedicated with acepromazine 0.02 mg/kg and morphine 0.5 mg/kg and anesthetized with propofol and isoflurane. Dogs were randomly assigned to 1 of 2 groups: Fentanyl group (fentanyl 5 µg/kg loading dose [LD] and 9 µg/kg/h CRI; n = 11); FLK group (fentanyl [same doses]; lidocaine 2 mg/kg LD and 3 mg/kg/h CRI; ketamine 1.0 mg/kg LD and 0.6 mg/kg/h CRI; = 11). Intraoperative evaluations were performed before the start of surgery and administration of the treatments (T0); three minutes after the LD (T1); during incision and tissue divulsion (T2); during closure of the surgical wound (T3). Meloxicam (0.1 mg/kg) was administered at T3. Blood samples were collected for determination of plasma concentrations of fentanyl, lidocaine and ketamine. Pain scores and the number of postoperative analgesic rescues with morphine (0.5 mg/kg) were evaluated for 24 hours postoperatively using the short form of the Glasgow Composite Measure Pain Scale. Compared to T0, significant decreases in heart rate (from 84 ± 28 to 53 ± 16 bpm in the Fentanyl group and from 93 ± 16 to 63 ± 15 bpm in FLK) and mean arterial pressure (from 61 ± 5 to 49 ± 10 mmHg in Fentanyl and from 59 ± 3 to 38 ± 6 mmHg in FLK) were observed at T1. Arterial hypotension was transient, with normalization of values at T2 and T3. The expired fraction of isoflurane did not differ significantly between the groups. Plasma concentrations of fentanyl, lidocaine and ketamine remained within the therapeutic range. Postoperatively, the number of dogs requiring analgesic rescue was significantly lower in the FLK (0/11, 0%) than in the Fentanyl group (5/11, 45%). In dogs administered morphine and meloxicam as part of the anesthesia protocol, an intraoperative CRI of FLK abolished the requirement for postoperative analgesic rescue for 24 hours in dogs undergoing mastectomy.

Effects of Anesthesia on Cerebral Blood Flow and Functional Connectivity of Nonhuman Primates

Nonhuman primates (NHPs) are the closest living relatives of humans and play a critical and unique role in neuroscience research and pharmaceutical development. General anesthesia is usually required in neuroimaging studies of NHPs to keep the animal from stress and motion. However, the adverse effects of anesthesia on cerebral physiology and neural activity are pronounced and can compromise the data collection and interpretation. Functional connectivity is frequently examined using resting-state functional MRI (rsfMRI) to assess the functional abnormality in the animal brain under anesthesia. The fMRI signal can be dramatically suppressed by most anesthetics in a dose-dependent manner. In addition, rsfMRI studies may be further compromised by inter-subject variations when the sample size is small (as seen in most neuroscience studies of NHPs). Therefore, proper use of anesthesia is strongly demanded to ensure steady and consistent physiology maintained during rsfMRI data collection of each subject. The aim of this review is to summarize typical anesthesia used in rsfMRI scans of NHPs and the effects of anesthetics on cerebral physiology and functional connectivity. Moreover, the protocols with optimal rsfMRI data acquisition and anesthesia procedures for functional connectivity study of macaque monkeys are introduced.

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.

Effects of sevoflurane anesthesia and abdominal surgery on the systemic metabolome: a prospective observational study

Background

Metabolic status can be impacted by general anesthesia and surgery. However, the exact effects of general anesthesia and surgery on systemic metabolome remain unclear, which might contribute to postoperative outcomes.

Methods

Five hundred patients who underwent abdominal surgery were included. General anesthesia was mainly maintained with sevoflurane. The end-tidal sevoflurane concentration (ET_sevo) was adjusted to maintain BIS (Bispectral index) value between 40 and 60. The mean ET_sevo from 20 min after endotracheal intubation to 2 h after the beginning of surgery was calculated for each patient. The patients were further divided into low ET_sevo group (mean − SD) and high ET_sevo group (mean + SD) to investigate the possible metabolic changes relevant to the amount of sevoflurane exposure.

Results

The mean ET_sevo of the 500 patients was 1.60% ± 0.34%. Patients with low ET_sevo (n = 55) and high ET_sevo (n = 59) were selected for metabolomic analysis (1.06% ± 0.13% vs. 2.17% ± 0.16%, P < 0.001). Sevoflurane and abdominal surgery disturbed the tricarboxylic acid cycle as identified by increased citrate and cis-aconitate levels and impacted glycometabolism as identified by increased sucrose and D-glucose levels in these 114 patients. Glutamate metabolism was also impacted by sevoflurane and abdominal surgery in all the patients. In the patients with high ET_sevo, levels of L-glutamine, pyroglutamic acid, sphinganine and L-selenocysteine after sevoflurane anesthesia and abdominal surgery were significantly higher than those of the patients with low ET_sevo, suggesting that these metabolic changes might be relevant to the amount of sevoflurane exposure.

Conclusions

Sevoflurane anesthesia and abdominal surgery can impact principal metabolic pathways in clinical patients including tricarboxylic acid cycle, glycometabolism and glutamate metabolism. This study may provide a resource data for future studies about metabolism relevant to general anaesthesia and surgeries.

Trial registration

www.chictr.org.cn. identifier: ChiCTR1800014327.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-021-01301-0.

Dexmedetomidine combined with etomidate or emulsified isoflurane for induction reduced cardiopulmonary response in dogs

To investigate the effects of etomidate, emulsified isoflurane, and their combination with dexmedetomidine on physiological parameters, electrocardiogram (ECG) results, and the quality of induction and recovery during isoflurane maintenance anaesthesia. 5 mixed-breed dogs received each of four treatments: etomidate (E group); emulsified isoflurane (EI group); both dexmedetomidine and etomidate (DE group); or both dexmedetomidine and emulsified isoflurane (DEI group). All drugs were IV injection administered for induction, followed by 1.5 MAC (minimal alveolar concentration) of isoflurane to maintain anaesthesia. Rectal temperature (RT), respiratory rate (RR), heart rate (HR), mean arterial pressure (MAP), and ECG were measured at baseline, 0, 5, 10, 20, 40, and 60 minutes after intubation. The quality of induction and recovery was evaluated for all dogs. All the anaesthetic procedures provided good conditions for induction of anaesthesia. The quality of induction and recovery in the E group was worse than other groups. The decrease of RR in the E and DE groups was stronger than that in the EI and DEI groups. The dogs in the E group had the most significant prolongation of the Q-T interval and changes in the S-T segment. Deviation and extension of the S-T segment were noted in the El group. The dogs in the DE and DEI groups had fewer changes in the ECG results than those in the E and EI groups. The addition of dexmedetomidine caused less effect on cardiopulmonary parameters and the ECG results than either etomidate or emulsified isoflurane alone. Thus, etomidate or emulsified isoflurane in combination with dexmedetomidine may be useful clinically for the induction of anaesthesia.

Effects of hyaluronidase on ropivacaine or bupivacaine regional anaesthesia of the canine pelvic limb

OBJECTIVE

To determine the effect of hyaluronidase on time to onset and offset of anaesthesia in ropivacaine or bupivacaine femoral-ischiatic nerve blocks.

STUDY DESIGN

Blinded randomized crossover trial.

ANIMALS

Eight dogs.

METHODS

Each dog underwent four treatments separated into two blocks - initially, the ropivacaine treatment block: RS (ropivacaine 0.5% plus saline 0.9%) and RH (ropivacaine 0.5% plus hyaluronidase 100 IU mL^-1), followed 3 weeks later by the bupivacaine treatment block: BS (bupivacaine 0.5% plus saline) and BH (bupivacaine 0.5% plus hyaluronidase). The local anaesthetics were administered at 0.1 mL kg^-1 per site. Hyaluronidase and saline were administered at 0.02 mL kg^-1 per site. Performance of femoral-ischiatic blocks was aided by a combined ultrasound-electrolocation technique. The mechanical nociceptive threshold was measured, until offset or 360 minutes, using an algometer to ascertain baseline, onset and offset of anaesthesia. Onset and offset of anaesthesia were defined as a 25% increase above and as a return to <25% above baseline nociceptive threshold readings, respectively.

RESULTS

The median (range) onset of anaesthesia for RS and RH was 21 (3-60) and 12 (3-21) minutes, respectively (p = 0.141), and offset was 270 (90-360) and 180 (30-300) minutes, respectively (p = 0.361). By contrast, the median (range) onset of anaesthesia for BS and BH was 24 (3-60) and 9 (3-27) minutes, respectively (p = 0.394), and offset was 360 (240-360) and 330 (210-360) minutes, respectively (p = 0.456).

CONCLUSION AND CLINICAL RELEVANCE

Hyaluronidase had no effect on the onset and offset times of ropivacaine and bupivacaine femoral-ischiatic nerve blocks in dogs compared with saline. The onset and offset times were highly variable in all treatments. Clinically, the high variability of the onset and offset times of the regional anaesthesia of these local anaesthetic drugs means that clinicians must monitor the animal's response and, if required, provide additional analgesic drugs.

The use of desflurane for neurosurgical procedures in rhesus macaque ( Macaca mulatta)

Volatile agents are widely used to anaesthetise laboratory non-human primates as they allow a rapid induction and recovery as well as an easy adjustment of the anaesthesia plan. Desflurane is currently the volatile agent with the lowest solubility in blood, and hence enables the most rapid onset of anaesthesia and most rapid recovery. This study aimed to investigate the suitability of desflurane for maintenance of general anaesthesia in rhesus macaques undergoing elective experimental neurosurgery. Fourteen primates (five males and nine females) were sedated with ketamine (10 mg kg^-1) and anaesthesia was induced with propofol (usually 8 mg kg^-1 IV). Anaesthesia was maintained with desflurane (5.9 ± 0.8 %) and alfentanil (0.2-0.5 µg kg^-1 min^-1 IV). Animals were mechanically ventilated. Meloxicam (0.3 mg kg^-1) and methylprednisolone infusion (5.4 mg kg^-1 h^-1) were also administered. All the primates were successfully anaesthetised and no severe complications related to the procedure or the anaesthesia regimen occurred. No major differences in physiological parameters and recovery times between the male and female groups were found. Emergence from anaesthesia was rapid (male 5.2 ± 2.4 min; female 4.1 ± 1.7 min) but its quality was assessed as equivalent to two other volatile anaesthetics, isoflurane and sevoflurane. These had previously been assessed for neuroanaesthesia in rhesus macaques. In conclusion, this study demonstrated that desflurane was suitable for maintenance of general anaesthesia for elective experimental neurosurgical procedures in rhesus macaque. However the vasodilatory action of the desflurane may limit its use in cases of severe intracranial hypertension or systemic hypotension.

Reliability of video recordings to evaluate quality of anesthesia recovery in dogs

OBJECTIVE

To assess the reliability of using video recordings to evaluate anesthesia recovery in dogs.

STUDY DESIGN

Prospective study.

ANIMALS

A total of 30 dogs undergoing surgery.

METHODS

Recovery monitoring and video recording lasted from extubation until 1 hour later. Scoring was done in real time at the end of the hour by a graduate student using three systems: a simple descriptive scale, visual analog scale and numeric rating scale. Videos were distributed to three American College of Veterinary Anesthesia and Analgesia board-certified anesthesiologist raters as well as the original rater to score. These videos were revisited 4 months later, and the recoveries were scored again. To assess reliability, Cohen's and Fleiss' kappa values evaluated the agreement between sessions. Wilcoxon signed-rank tests were run comparing each observer's two sessions. Recoveries were classified as 'good' or 'bad' according to the cut-off values for each system.

RESULTS

Correlation values among raters ranged from 0.50 to 0.82 and from 0.26 to 0.60 in the first and second session, respectively. Bland-Altman plots revealed biases between 0.133 and 1.633 points for each of the three scoring systems. Cohen's kappa had agreement ranging from 0.29 to 0.79 during the first viewing and from 0.17 to 0.44 during the second. Fleiss' kappa values were 0.06, 0.16, 0.22 and 0.26 for various data combinations. Considering overall recovery, Fleiss' kappa showed agreement ranging from 0.54 to 0.71 and from 0.13 to 0.49 for the first and second session, respectively. Of the 12 Wilcoxon tests run, seven found significantly different scores between the two scoring sessions. The recoveries given an overall good or bad were the same on both occasions that they were reviewed.

CONCLUSIONS AND CLINICAL RELEVANCE

The use of a video to evaluate recovery in dogs should be used with caution. Individual raters' agreement for specific scores was poor, but evaluating recovery overall had perfect agreement.

Comparison of emergence times and quality between isoflurane and sevoflurane in rhesus macaque (Macaca mulatta) undergoing neurosurgical procedure

Volatile agents for anaesthesia are widely used for anaesthetizing laboratory primates, and isoflurane is one of the most frequently used agents. Sevoflurane has been shown to offer a more rapid recovery than isoflurane in a number of species, but no comparisons have been made in non-human primates. This study compared the recovery characteristics of isoflurane and sevoflurane in rhesus macaques undergoing experimental neurosurgery. Twelve primates (7 males and 5 females) were randomly allocated to the treatment groups. They were sedated with ketamine (10 mg/kg) and anaesthesia was induced with propofol (usually 8 mg/kg intravenously [IV]). Anaesthesia was maintained with either sevoflurane (SEVO) (2.2 ± 0.4%) or isoflurane (ISO) (1.2 ± 0.2%) and alfentanil (0.2–0.5 µg/kg/min IV) for 332–592 min. Animals were mechanically ventilated. Meloxicam (0.3 mg/kg) and methylprednisolone infusion (5.4 mg/kg/h) were also administered. Time to extubation after cessation of anaesthesia was significantly shorter with sevoflurane (ISO: 7.0 ± 1.8 min; SEVO: 3.6 ± 1.5; *P = 0.005) as was the time to the animal sitting unaided (ISO: 15.7 ± 8.2 min; SEVO: 7.1 ± 1.7 min; *P = 0.004) . No significant difference in the quality of recovery following isoflurane or sevoflurane anaesthesia was found. In conclusion, isoflurane and sevoflurane are both suitable volatile agents for the maintenance of general anaesthesia in rhesus macaques undergoing experimental neurosurgical procedures. The two volatile agents presented a similar emergence quality profile, however sevoflurane anaesthesia was associated with a faster recovery, offering the possibility of conducting earlier post-operative neurological assessment.

Isoflurane, sevoflurane and desflurane use in cane toads (Rhinella marina)

Anaesthetic chamber concentrations of isoflurane, sevoflurane and desflurane that resulted in loss of righting reflex within 15 minutes in 50 per cent of toads (Rhinella marina) exposed (ED_50-LRR<15MIN) were identified. The median and range ED_50-LRR<15MIN was 1.4 (0.9–1.4) per cent for isoflurane, 1.75 (1.1–1.9) per cent for sevoflurane and 4.4 (4.3–5.5) per cent for desflurane. Subsequently, toads were exposed to 1.5 times the ED_50-LRR<15MIN and times to loss and return of righting reflex were identified. All toads for all anaesthetics lost righting reflex. The median and range loss of righting reflex was 4:00 (3:00–5:30) minutes for isoflurane, 4:45 (3:30–7:00) minutes for sevoflurane, and 4:15 (4:00–5:30) minutes for desflurane and was not different between anaesthetics. Time to return of righting reflex was 175 (123–211) minutes for isoflurane, 192 (116–383) minutes for sevoflurane and 74 (52–220) minutes for desflurane. Time to return of righting reflex was significantly shorter for desflurane compared with isoflurane or sevoflurane. The use of isoflurane, sevoflurane or desflurane can be used to provide immobilisation to cane toads and potentially other anurans. Induction times are likely similar when using an anaesthetic chamber to provide anaesthesia. However recovery time may take twice as long when utilising isoflurane or sevoflurane over desflurane.

Perianesthetic complications in dogs undergoing magnetic resonance imaging of the brain for suspected intracranial disease

OBJECTIVE

To evaluate the occurrence of perianesthetic complications in dogs undergoing MRI for suspected intracranial disease and identify risk factors associated with observed complications.

DESIGN

Retrospective case-control study.

ANIMALS

238 client-owned dogs undergoing MRI of the brain.

PROCEDURES

Signalment, clinical signs, neurologic examination findings, presumptive diagnosis, anesthesia-related variables, whether CSF was collected and CSF analysis results, severe perianesthetic complications (need for a ventilator following anesthesia or perianesthetic death), and anesthetic recovery time were recorded. Selected factors were compared between dogs with and without intracranial lesions and dogs with and without perianesthetic complications (including severe complications and prolonged anesthetic recovery [> 20 minutes from the end of anesthesia to extubation]).

RESULTS

3 of 149 (2%) dogs with and 0 of 89 dogs without intracranial lesions required ventilation following anesthesia; the difference was nonsignificant. Recovery time was significantly longer in dogs with (median, 15 minutes) than in dogs without (10 minutes) intracranial lesions. Abnormal mentation prior to anesthesia was the only clinical sign that differed significantly between dogs with (15/26 [58%]) and without (70/212 [33%]) perianesthetic complications. A significantly larger proportion of dogs with perianesthetic complications had intracranial masses (13/26 [50%]), compared with dogs without these complications (56/212 [26%]).

CONCLUSIONS AND CLINICAL RELEVANCE

Dogs with complications were more likely to have had intracranial lesions than were dogs without complications, but few dogs had severe complications. Abnormal mentation was more common in dogs with than in dogs without complications. Prospective studies to further evaluate perianesthetic risk factors and procedures for improving outcomes in these patients are warranted.