COMPARISON OF ISOFLURANE AND SEVOFLURANE FOR SHORT-TERM ANESTHESIA IN MEERKATS (SURICATA SURICATTA)-ARE THERE BENEFITS THAT OUTWEIGH COSTS?

Meerkats ( Suricata suricatta ) are routinely anesthetized with isoflurane in zoo and field settings. Twenty healthy adult meerkats of mixed age and sex held in the Zoological Society of London's collection were anesthetized with 4% isoflurane by face mask for routine health examinations. The procedure was repeated 5 mo later in the same group of animals utilizing sevoflurane at 5% for induction, and again 3 mo later with sevoflurane at 6.5% for induction to approximate equipotency with isoflurane. The speed and quality of induction and recovery were compared between the two volatile anesthetic agents. There was no statistically significant difference in the speed of induction across any of the anesthetic regimes. There was a significant difference in recovery times between isoflurane and 6.5% sevoflurane (427 ± 218 and 253 ± 65 sec, respectively [mean ± SD]). Under the conditions of this study, sevoflurane at 6.5% induction dose resulted in better quality induction and recovery than sevoflurane at 5% induction or isoflurane. The mean heart and respiratory rates during anesthesia were higher using 5% sevoflurane for induction but there was no significant difference in either rate between isoflurane and sevoflurane used at a 6.5% induction dose. This study suggests that sevoflurane at a dose of 6.5% for induction and 4% for maintenance is a safe and effective anesthetic agent in healthy adult meerkats. Rapid return to normal behavior after anesthesia is important in all zoo species but particularly so in animals with a complex social and hierarchical structure such as meerkats. For this species, the advantage afforded by the speed of recovery with sevoflurane may offset the cost in certain circumstances.

Ventriculo-arterial coupling detects occult RV dysfunction in chronic thromboembolic pulmonary vascular disease.

Chronic thromboembolic disease (CTED) is suboptimally defined by a mean pulmonary artery pressure (mPAP) <25 mmHg at rest in patients that remain symptomatic from chronic pulmonary artery thrombi. To improve identification of right ventricular (RV) pathology in patients with thromboembolic obstruction, we hypothesized that the RV ventriculo-arterial (Ees/Ea) coupling ratio at maximal stroke work (Ees/Eamax sw) derived from an animal model of pulmonary obstruction may be used to identify occult RV dysfunction (low Ees/Ea) or residual RV energetic reserve (high Ees/Ea). Eighteen open chested pigs had conductance catheter RV pressure-volume (PV)-loops recorded during PA snare to determine Ees/Eamax sw This was then applied to 10 patients with chronic thromboembolic pulmonary hypertension (CTEPH) and ten patients with CTED, also assessed by RV conductance catheter and cardiopulmonary exercise testing. All patients were then restratified by Ees/Ea. The animal model determined an Ees/Eamax sw = 0.68 ± 0.23 threshold, either side of which cardiac output and RV stroke work fell. Two patients with CTED were identified with an Ees/Ea well below 0.68 suggesting occult RV dysfunction whilst three patients with CTEPH demonstrated Ees/Ea ≥ 0.68 suggesting residual RV energetic reserve. Ees/Ea > 0.68 and Ees/Ea < 0.68 subgroups demonstrated constant RV stroke work but lower stroke volume (87.7 ± 22.1 vs. 60.1 ± 16.3 mL respectively, P = 0.006) and higher end-systolic pressure (36.7 ± 11.6 vs. 68.1 ± 16.7 mmHg respectively, P < 0.001). Lower Ees/Ea in CTED also correlated with reduced exercise ventilatory efficiency. Low Ees/Ea aligns with features of RV maladaptation in CTED both at rest and on exercise. Characterization of Ees/Ea in CTED may allow for better identification of occult RV dysfunction.

Effects of different doses of dexmedetomidine on anaesthetic induction with alfaxalone--a clinical trial.

OBJECTIVE: To document the effects of two doses of dexmedetomidine on the induction characteristics and dose requirements of alfaxalone. STUDY DESIGN: Randomized controlled clinical trial. ANIMALS: Sixty one client owned dogs, status ASA I-II. METHODS: Dogs were allocated randomly into three groups, receiving as pre-anaesthetic medication, no dexmedetomidine (D0), 1 µg kg(-1) dexmedetomidine (D1 ) intramuscularly (IM) or 3 µg kg(-1) dexmedetomidine IM (D3). All dogs also received 0.2 mg kg(-1) methadone IM. Level of sedation was assessed prior to induction of anaesthesia. Induction of general anaesthesia was performed with alfaxalone administered intravenously to effect at a rate of 1 mg kg(-1) minute(-1) ; the required dose to achieve tracheal intubation was recorded. Anaesthesia was maintained with isoflurane in oxygen. Cardiopulmonary parameters were recorded throughout the anaesthetic period. Quality of intubation, induction and recovery of anaesthesia were recorded. Quantitative data were compared with one-way anova or Kruskal-Wallis test. Repeated measures were log-transformed and analysed with repeated measures anova (p < 0.05). RESULTS: Treatment groups were similar for categorical data, with exception of sedation level (p < 0.001). The doses (mean ± SD) of alfaxalone required for intubation were D0 1.68 ± 0.24, D1 1.60 ± 0.36 and D3 1.41 ± 0.43, the difference between D0 and D3 being statistically significant (p = 0.036). Heart and respiratory rates during the anaesthetic period were significantly different over time and between groups (p < 0.001); systolic arterial blood pressure was significantly different over time (p < 0.001) but not between groups (p = 0.833). Induction quality and recovery scores were similar between groups (p = 1.000 and p = 0.414, respectively). CONCLUSIONS AND CLINICAL RELEVANCE: The administration of alfaxalone resulted in a good quality anaesthetic induction which was not affected by the dose of dexmedetomidine. Dexmedetomidine at 3 µg kg(-1) IM combined with methadone provides good sedation and enables a reduction of alfaxalone requirements.

Comparison of quality of recovery from anaesthesia in cats induced with propofol or alfaxalone.

OBJECTIVE: To assess the quality and length of recovery from anaesthesia induced with either propofol or alfaxalone and maintained with isoflurane, in cats undergoing short procedures in private veterinary practice. STUDY DESIGN: Prospective, blinded, randomized study. ANIMALS: Ninety-three healthy mixed breed cats. METHODS: After premedication with intramuscular acepromazine (0.05 mg kg(-1)) and buprenorphine (0.01 mg kg(-1)), cats were randomly allocated to receive either propofol (Group P) or alfaxalone (Group A) for induction of anaesthesia. Following endotracheal intubation, anaesthesia was maintained with isoflurane vaporized in oxygen. The quality of induction, physiological parameters throughout anaesthesia and the duration of both surgery and anaesthesia were recorded. The level of ambient noise, recovery times, number of attempts to stand, reaction of the cat to touch 15 minutes after extubation, and other relevant characteristics of the recovery period were noted and a video recording of the recovery was made. The videos were assessed by a second, blinded anaesthetist, using simple descriptive and visual analogue scales. RESULTS: No statistically significant differences between groups with respect to preoperative data, premedication, surgery, anaesthesia and recovery times and scores were observed. There was a statistically significant difference in the number of patients paddling and trembling on recovery in Group A (p = 0.032) even though there was no statistically significant difference in the level of ambient noise in the recovery ward or in the overall quality of recovery. CONCLUSIONS: Both propofol and alfaxalone provide good recovery characteristics in premedicated cats undergoing short procedures in clinical settings. Alfaxalone induction was associated with more episodes of paddling and trembling during recovery. CLINICAL RELEVANCE: Both agents would appear appropriate for induction of anaesthesia in cats for short procedures.

Clinical efficacy and cardiorespiratory effects of alfaxalone, or diazepam/fentanyl for induction of anaesthesia in dogs that are a poor anaesthetic risk.

OBJECTIVE: To evaluate the clinical efficacy and cardiorespiratory effects of alfaxalone as an anaesthetic induction agent in dogs with moderate to severe systemic disease. STUDY DESIGN: Randomized prospective clinical study. ANIMALS: Forty dogs of physical status ASA III-V referred for various surgical procedures. METHODS: Dogs were pre-medicated with intramuscular methadone (0.2 mg kg(-1) ) and allocated randomly to one of two treatment groups for induction of anaesthesia: alfaxalone (ALF) 1-2 mg kg(-1) administered intravenously (IV) over 60 seconds or fentanyl 5 µg kg(-1) with diazepam 0.2 mg kg(-1) ± propofol 1-2 mg kg(-1) (FDP) IV to allow endotracheal intubation. Anaesthesia was maintained with isoflurane in oxygen and fentanyl infusion following both treatments. All dogs were mechanically ventilated to maintain normocapnia. Systolic blood pressure (SAP) was measured by Doppler ultrasound before and immediately after anaesthetic induction, but before isoflurane administration. Parameters recorded every 5 minutes throughout subsequent anaesthesia were heart and respiratory rates, end-tidal partial pressure of carbon dioxide and isoflurane, oxygen saturation of haemoglobin and invasive systolic, diastolic and mean arterial blood pressure. Quality of anaesthetic induction and recovery were recorded. Continuous variables were assessed for normality and analyzed with the Mann Whitney U test. Repeated measures were log transformed and analyzed with repeated measures anova (p<0.05). RESULTS: Treatment groups were similar for continuous and categorical data. Anaesthetic induction quality was good following both treatments. Pre-induction and post-induction systolic blood pressure did not differ between treatments and there was no significant change after induction. The parameters measured throughout the subsequent anaesthetic procedures did not differ between treatments. Quality of recovery was very, quite or moderately smooth. CONCLUSIONS AND CLINICAL RELEVANCE: Induction of anaesthesia with alfaxalone resulted in similar cardiorespiratory effects when compared to the fentanyl-diazepam-propofol combination and is a clinically acceptable induction agent in sick dogs.

Incidence of elevation of cardiac troponin I prior to and following routine general anaesthesia in dogs.

OBJECTIVE: To estimate the incidence of raised cTnI after general anaesthesia in dogs and to explore major risk factors influencing this. STUDY DESIGN: Prospective clinical study. Animals A total of 107 (ASA physical status 1-2) dogs, 63% male and 37% female, median age 5 years (range 0.3-13.4), median weight 24.4 kg (range 4.2-66.5 kg) undergoing anaesthesia for clinical purposes. METHODS: Venous blood samples were taken within 24 hours prior to induction and 24 hours after the termination of anaesthesia. Serum concentrations of cardiac troponin I were measured using a chemiluminescent enzyme immunometric assay with a lower level of detection of 0.20 ng mL(-1) (below this level <0.20 ng mL(-1)). Continuous data were assessed graphically for normality and paired and unpaired data compared with the Wilcoxon signed ranks and Mann-Whitney U-tests respectively. Categorical data were compared with the Chi squared or Fisher's exact test as appropriate (p < 0.05). RESULTS: Of the 107 dogs recruited, 100 had pre- and post-anaesthetic cTnI measured. The median pre-anaesthesia cTnI was '<0.20' ng mL(-1) (range '<0.20'-0.43 ng mL(-1)) and the median increase from pre-anaesthesia level was 0.00 ng mL(-1) (range -0.12 to 0.61 ng mL(-1)). Fourteen dogs had increased cTnI after anaesthesia relative to pre-anaesthesia (14%, 95% CI 7.2-20.8%, range of increase 0.03-0.61 ng mL(-1)). Six animals had cTnI levels that decreased (range 0.02-0.12 ng mL(-1)). Older dogs were more likely to have increased cTnI prior to anaesthesia (OR = 5.32, 95% CI 1.35-21.0, p = 0.007) and dogs 8 years and over were 3.6 times as likely to have an increased cTnI after anaesthesia (95% CI 1.1-12.4, p = 0.028). CONCLUSION AND CLINICAL RELEVANCE: Increased cTnI after anaesthesia relative to pre-anaesthesia levels was observed in a number of apparently healthy dogs undergoing routine anaesthesia.

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

OBJECTIVE: To compare the recovery after anaesthesia with isoflurane, sevoflurane and desflurane in dogs undergoing magnetic resonance imaging (MRI) of the brain. STUDY DESIGN: Prospective, randomized clinical trial. ANIMALS: Thirty-eight dogs weighing 23.7 +/- 12.6 kg. METHODS: Following pre-medication with meperidine, 3 mg kg(-1) administered intramuscularly, anaesthesia was induced intravenously with propofol (mean dose 4.26 +/- 1.3 mg kg(-1)), the trachea was intubated, and an inhalational anaesthetic agent was administered in oxygen. The dogs were randomly allocated to one of three groups: group I (n = 13) received isoflurane, group S (n = 12) received sevoflurane and group D (n = 13) received desflurane. Parameters recorded included cardiopulmonary data, body temperature, end-tidal anaesthetic concentration, duration of anaesthesia, and recovery times and quality. Qualitative data were compared using chi-squared and Fisher's exact tests and quantitative data with anova and Kruskal-Wallis test. Post-hoc comparisons for quantitative data were undertaken with the Mann-Whitney U-test. RESULTS: The duration of anaesthesia [mean and standard deviation (SD)] in group I was: 105.3 (27.48) minutes, group S: 120.67 (19.4) minutes, and group D: 113.69 (26.68) minutes (p = 0.32). Times to extubation [group I: 8 minutes, (interquartile range 6-9.5), group S: 7 minutes (IQR 5-7), group D: 5 minutes (IQR 3.5-7), p = 0.017] and to sternal recumbency [group I: 11 minutes (IQR 9.5-13.5), group S: 9.5 minutes (IQR 7.25-11.75), group D: 7 minutes (range 3.5-11.5), p = 0.048] were significantly different, as were times to standing. One dog, following sevoflurane, had an unacceptable quality of recovery, but most other recoveries were calm, with no significant difference between groups. CONCLUSIONS AND CLINICAL RELEVANCE: All three agents appeared suitable for use. Dogs' tracheas were extubated and the dogs recovered to sternal recumbency most rapidly after desflurane. This may be advantageous for animals with some neurological diseases and for day case procedures.

The isoflurane-sparing and clinical effects of a constant rate infusion of remifentanil in dogs.

OBJECTIVE: To evaluate the isoflurane-sparing and clinical effects of two constant rate infusions of remifentanil in healthy dogs undergoing orthopaedic surgery. STUDY DESIGN: Prospective, randomized clinical study. ANIMALS: Forty-one American Society of Anesthesiologists I-II client-owned dogs (age, 7 months-9 years; body mass 11-59 kg). METHODS: Dogs were randomly assigned to one of three groups and received either: intramuscular (IM) meperidine 2 mg kg(-1) every 2 hours throughout surgery (control group (C); n = 13); remifentanil infused intravenously (IV) at 0.1 microg kg(-1) minute(-1) (low remifentanil group (L); n = 14) or remifentanil infused at 0.25 microg kg(-1) minute(-1) IV (high remifentanil group (H); n = 14). Anaesthesia was induced with thiopental administered to effect and maintained using isoflurane in 100% oxygen. During controlled ventilation when the end-tidal CO(2) was maintained between 4.65 and 5.98 kPa [35-45 mmHg], the end-tidal isoflurane concentration (e'iso%), mean arterial blood pressure (MAP) and heart rate (HR) were measured every 5 minutes. Bradycardia (HR < 40 minute(-1) lasting >5 minutes) was corrected with 0.01 mg kg(-1) IV glycopyrrolate. Data were analysed using the Kruskal-Wallis test with a post-hoc Mann-Whitney U-test and Bonferroni correction. Statistical significance was accepted at < or = 0.05. Data are expressed as mean +/- standard deviation. RESULTS: The e'iso% was reduced in a dose-dependent manner by remifentanil. In C, e'iso% was 1.28 +/-0.13 and was significantly different from L (0.78 +/- 0.17, p < 0.001) and H (0.65 +/- 0.16, p < 0.001). HR was significantly different between groups (p < 0.001). There were no significant differences in MAP between groups. Glycopyrrolate was required in two, three and six dogs in the C, L and H groups respectively. CONCLUSIONS: Remifentanil infusion reduced the isoflurane concentration required for surgical anaesthesia during orthopaedic surgery. CLINICAL RELEVANCE: Remifentanil infusions may be a useful additive to isoflurane anaesthesia in healthy dogs.