The effects of morphine on the recovery of horses from halothane anaesthesia

OBJECTIVE: To investigate the effects of peri-operative morphine on the quality and duration of recovery from halothane anaesthesia in horses. STUDY DESIGN: Prospective randomized study. ANIMALS: Twenty-two client owned horses, ASA category I or II. METHODS: Horses undergoing elective surgical procedures were divided into two groups and paired according to procedure, body position during surgery, body mass and breed. Group M+ received morphine by intravenous injection (0.15 mg kg(-1)) before induction of anaesthesia and then by infusion (0.1 mg kg(-1) hour(-1)) during anaesthesia. Group M- received the same anaesthetic agents except that morphine was excluded. At the end of surgery, the horses were placed in a recovery box and allowed to recover without assistance. Recoveries were recorded on videotape, beginning when the anaesthetist left the recovery box, and ending when the horse stood up. Recoveries were assessed from digital video recordings by three observers, unaware of treatment. The time to first movement, attempting and attaining sternal recumbency and standing were recorded. The quality of various aspects of the recovery was assessed to produce a total recovery score; high numerical values indicate poor recoveries. The duration of anaesthesia and the total dose of morphine administered were recorded. RESULTS: The mean morphine dose (95% CI) was 147 (135-160) mg [equivalent to 0.27 (0.25-0.29) mg kg(-1)]. The recovery scores (median, 95% CI) for the M- and M+ groups were 25, 19-41 and 20, 14-26, respectively. Total score increased as duration of anaesthesia increased, independent of treatment. Untreated (M-) horses made more attempts to achieve sternal recumbency: mean number of attempts (95% CI) for M- was 4.5 (2.7-6.2) compared with 2.0 (1.4-2.6) (M+). Untreated horses made more attempts to stand (2.1, 1.6-2.6) compared with the morphine recipients (1.3, 1.1-1.5). Time to standing (in minutes) was significantly (p = 0.0146) longer for the untreated (31.3, 24.3-38.3) compared with treated animals (26.6, 20.9-32.3). The interval between the first movement in recovery to the time at standing was significantly (p < 0.001) longer for M- (14.5, 12.1-16.9 minutes) compared with M+ animals (7.4, 5.0-9.8 minutes). CONCLUSIONS AND CLINICAL RELEVANCE: Recoveries from anaesthesia in the morphine recipients were characterized by fewer attempts to attain sternal recumbency and standing, and a shorter time from the first recovery movement to the time of standing.     

Bispectral monitoring in dogs subjected to ovariohysterectomy and anesthetized with halothane, isoflurane or sevoflurane

ObjectiveTo assess the effect of halothane (H), isoflurane (I) or sevoflurane (S) on the bispectral index (BIS), and the effect of the addition of meperidine in dogs subjected to ovariohysterectomy.Study designProspective, randomized, blinded, clinical trial.AnimalsForty-eight female mixed-breed dogs, with weights varying from 10 to 25 kg.MethodsAll dogs were premedicated with acepromazine (A) (0.1 mg kg^?1 IM) or A and meperidine (M) (3 mg kg^?1 IM) and they were divided into six groups of eight animals (AH, AMH, AI, AMI, AS, and AMS). Fifteen minutes after premedication they were anesthetized with propofol (5 mg kg^?1 IV) and then orotracheally intubated. Anesthesia was maintained with halothane, isoflurane or sevoflurane, respectively. The BIS,

variables were recorded at 15 minutes after administering pre-anesthetic medication (T0); 10 minutes of anesthesia maintenance (T1); right ovarian pedicle ligation (T2); muscle suturing (T3); skin suture (T4) and 10 minutes after terminating the inhalant anesthetic (T5), respectively.ResultsBIS values were decreased at all times when compared to the baseline values in all groups (p < 0.05). In the comparative assessment between groups, the values obtained at T0 and T1 were similar for all groups. At T2, the values in AMH were lower than those obtained in AI, AMI and AS (p < 0.05). At the same time significantly higher values were found for AI when compared to AMS (p < 0.01). There was a correlation between the bispectral index and the expired anesthetic fraction in all groups.Conclusions and clinical relevanceWithin groups given the same inhalant anesthetic the bispectral index was a good indicator for the degree of hypnosis in dogs, indicating a good correlation with the amount of anesthetic and the nociceptive stimulation. BIS was a less reliable indicator of relative anesthetic depth when comparing equipotent end-tidal concentrations between the three inhalants.     

Anaesthesia in horses using halothane and intravenous ketamine–guaiphenesin: a clinical study

Objective The aim of this study was to define and evaluate a combined inhalation?intravenous anaesthetic protocol for use in equine anaesthesia. Study design Prospective, randomized clinical trial. Animals Twenty‐eight horses (body mass 522 ± 82; 330–700 kg [mean ± SD; range]) with a mean age of 6 ± 4 years (range: 2–18 years) presented to the university hospital for various surgical procedures requiring general anaesthesia. Materials and methods Animals were randomly allocated to one of two treatment groups. Anaesthesia was maintained in 14 horses with halothane alone (H group). The mean end‐tidal halothane concentration was 1.24%. In the second group (n = 14) anaesthesia was maintained with both halothane (end‐tidal concentration 0.61%) and a continuous infusion of a ketamine–guaiphenesin mixture (HKG group). The two techniques were compared in terms of qualitative differences and cardiopulmonary effects. Results The stability of anaesthesia was significantly greater in group HKG and the need for dobutamine to maintain blood pressure was significantly less. Recovery times and quality were acceptable in all cases. There were no significant differences between the groups. Conclusions The infusion of ketamine and guaiphenesin in horses receiving low inspired concentrations of halothane provides suitable surgical anaesthesia and lowers the risk of hypotension. Clinical relevance The anaesthetic technique described in this study is a useful and practical alternative to inhalation anaesthesia using halothane alone.     

A comparison of recovery times and characteristics with sevoflurane and isoflurane anaesthesia in horses undergoing magnetic resonance imaging

Objective To compare recovery times and quality following maintenance of anaesthesia with sevoflurane or isoflurane after a standard intravenous induction technique in horses undergoing magnetic resonance imaging (MRI). Study design Prospective, randomised, blinded clinical study. Animals One hundred ASA I/II horses undergoing MRI. Materials and methods Pre‐anaesthetic medication with intravenous acepromazine and romifidine was followed by induction of anaesthesia with diazepam and ketamine. The animals were randomised into two groups to receive either sevoflurane or isoflurane in oxygen. Horses were subjectively scored (0–5) for temperament before sedation, for quality of sedation, induction and maintenance and anaesthetic depth on entering the recovery area. Recoveries were videotaped and scored by an observer, unaware of the treatment, using two scoring systems. Times to the first movement, head lift, sternal recumbency and standing were recorded along with the number of attempts to achieve sternal and standing positions. Variables were compared using a Student t‐test or Mann–Whitney U‐test (p < 0.05), while the correlation between subjective recovery score and other relevant variables was tested calculating the Spearman Rank correlation coefficient and linear regression modelling performed when significant. Results Seventy‐seven horses entered the final analysis, 38 received isoflurane and 39 sevoflurane. Body mass, age and duration of anaesthesia were similar for both groups. There were no differences in recovery times, scoring or number of attempts to achieve sternal recumbency and standing between groups. Weak, but significant, correlations were found between the subjective recovery score for the pooled data from both groups and both temperament and time in sternal recumbency. Conclusions No differences in recovery times or quality were detected following isoflurane or sevoflurane anaesthesia after intravenous induction. Clinical relevance Sevoflurane affords no obvious advantage in recovery over isoflurane following a standard intravenous induction technique in horses not undergoing surgery.     

Effects of peri-operative morphine administration during halothane anaesthesia in horses

OBJECTIVE: To study the effects of morphine on haemodynamic variables, blood gas values and the requirement for additional anaesthetic drugs in horses undergoing surgery. STUDY DESIGN: Prospective randomized study. METHODS: Thirty-eight client-owned horses, ASA(American Society of Anesthesiologists) category I or II, undergoing elective surgical procedures, were studied. Horses were divided between two groups, and were paired according to operation, anaesthetist, body position during surgery, mass and breed. Group M+ received morphine by intravenous (IV) injection (0.15 mg kg(-1)) before induction of anaesthesia and then by infusion (0.1 mg kg(-1) hour(-1)) throughout anaesthesia. Group M- received the same anaesthetic technique (pre-anaesthetic medication with romifidine (100 microg kg(-1)) IV; induction with ketamine (2.2 mg kg(-1)) and diazepam (50 microg kg(-1)) IV; maintenance with halothane), except that morphine was excluded. Both groups received flunixin IV (1.1 mg kg(-1)) before surgery. Both groups also received 50% nitrous oxide for the first 10 minutes of anaesthesia. During anaesthesia, end-tidal halothane was maintained at 0.9% (+/-0.1%) in both groups. Heart rate (HR) and respiratory rate (fr), systolic, mean and diastolic arterial pressures were recorded every 5 minutes. Arterial blood samples were analysed every 20 minutes. Additional anaesthetics (ketamine and midazolam) were administered whenever the horse moved. Dobutamine was infused to maintain mean arterial pressure (MAP) > 58 mm Hg, but was discontinued when MAP reached 68 mm Hg. Mechanical ventilation was imposed when PaCO(2) exceeded 9.3 kPa (70 mm Hg). RESULTS: Haemodynamic data (HR and MAP) and blood gas measurements were analysed using repeated measure analysis using a mixed covariance pattern model (SAS version 8.2). A Student's t-test was used to investigate differences between groups in the doses of additional anaesthetics required. There were no significant differences between M+ or M- groups in MAP (p = 0.65), HR (p = 0.74), PaO2 (p = 0.40) or PaCO2 (p = 0.20). Fewer horses in the M+ group received additional anaesthetics (15.8% compared to 21.1% in M- group), and the mean dose of ketamine required was higher in the M- group (mean +/- SD: M-, 0.93 +/- 0.70; M+, 0.45 +/- 0.17). These differences were not statistically significant (p = 0.28). CONCLUSIONS: Pre-anaesthetic and peri-operative morphine administration is not associated with significant haemodynamic or ventilatory changes. Horses receiving morphine tended to receive fewer and lower doses of additional anaesthetic drugs, although this was not statistically significant.     

Endocrine, haematological and metabolic responses to sevoflurane anaesthesia in lambs

Objective To compare the magnitude and duration of the peri‐operative haematological, endocrine and metabolic effects of surgery performed under sevoflurane anaesthesia. Study Design Prospective randomized study. Animals Ten, 55‐day‐old lambs of both sexes, mean weight 20.8 ± 0.3 kg (range 18.5–23.6 kg). Methods Animals were randomly allocated to two equal groups. All were anaesthetized with sevoflurane for 3 hours. Surgery (end‐to‐end anastomosis of the right carotid artery and right jugular vein) was performed in animals of Group 1 only. The electrocardiogram, pulse oximetry, cardiac output and noninvasive arterial blood pressure (NIBP) were monitored. Venous blood samples (5 mL) were taken 30 minutes before induction of anaesthesia (T = 0) and 1 (T1), 24 (T2), 48 hours (T3) and 7 days (T4) after anaesthesia in order to measure plasma cortisol, ACTH, insulin, cyclic adenosine monophosphate (cAMP), glucose, protein concentrations and haematological variables. Results Sevoflurane decreased NIBP (minimum mean value: 64 ± 3 mm Hg) in both groups. Plasma cortisol and ACTH concentration increased in Group 1 (maximum mean values: cortisol: 136.2 nmol L^?1, ACTH: 54.5 pmol L^?1) and Group 2 (maximum mean values: cortisol: 128.7 nmol L^?1, ACTH: 44.0 pmol L^?1). Cyclic AMP increased only in Group 1 (9.3 nmol) 1 hour after anaesthesia. Neutrophilia, lymphopaenia and a decreased PCV were observed in both groups 1 hour after anaesthesia. Plasma protein and glucose concentrations did not change. Conclusions Increased ACTH and cortisol concentrations recorded 1 hour after anaesthesia suggest that sevoflurane induces a stress response in lambs. Clinical relevance The study did not identify the mechanism by which sevoflurane induces a stress response although hypotension is implicated.     

The effect of nitrous oxide on halothane, isoflurane and sevoflurane requirements in ventilated dogs undergoing ovariohysterectomy

OBJECTIVE: To examine the effect of 64% nitrous oxide (N2O) on halothane (HAL), isoflurane (ISO) or sevoflurane (SEV) requirements in dogs undergoing ovariohysterectomy. STUDY DESIGN: Prospective, randomized, clinical trial. ANIMALS: Ninety, healthy dogs of (mean +/- SD) body weight 21.2 +/- 10.0 kg and age 17.8 +/- 22.8 months. MATERIALS AND METHODS: After premedication with acepromazine, hydromorphone and glycopyrrolate, anesthesia was induced with thiopental administered to effect. Dogs received one of six inhalant protocols (n = 15 group): HAL; HAL/N2O; ISO; ISO/N2O; SEV; or SEV/N2O. End-tidal CO2 was maintained at 40 +/- 2 mmHg with intermittent positive pressure ventilation (IPPV). Body temperature, heart rate, indirect systemic arterial blood pressures, inspired and end-tidal CO2, volatile agent, N2O and O2 were recorded every 5 minutes. The vaporizer setting was decreased in 0.25-0.5% decrements to elicit a palpebral reflex, and this level maintained. Statistical analysis included two-way anova for repeated measures with Bonferroni's correction factor and statistical significance assumed when p < 0.05. Percentage reduction in end-tidal volatile agent was calculated at 60 minutes after starting study. RESULTS: End-tidal HAL, ISO and SEV decreased when N2O was administered. Percentage reduction: HAL (12.4%); ISO (37.1%) and SEV (21.4%). Diastolic, mean and systolic blood pressures increased in ISO/N2O compared with ISO. Heart rate increased in ISO/N2O and SEV/N2O compared with ISO and SEV, respectively. Systolic, mean and diastolic blood pressures increased in SEV compared with HAL and ISO. Systolic, mean, diastolic blood pressures and heart rate increased in SEV/N2O and ISO/N2O compared with HAL/N2O. CONCLUSIONS: N2O reduces HAL, ISO and SEV requirements in dogs undergoing ovariohysterectomy. Cardiovascular stimulation occurred when N2O was used with ISO, less so with SEV and not with HAL     

Electrocardiographic indicators of excitability in horses for predicting recovery quality after general anaesthesia

ObjectiveTo determine whether preoperative electrocardiographic measurements linked to sympathetic nervous activity could be used to predict recovery quality after general anaesthesia in horses.Study designProspective, clinical study.AnimalsEighteen adult client-owned horses.MethodsThe electrocardiogram (ECG) was recorded presurgery in horses under three standard conditions: stabled unattended; with a groom whilst being led along a standard course; alone in the induction box. After surgery, each animal's recovery quality was scored by eight experienced anaesthetists or technicians using Donaldson's scoring system (2000). The digitized ECG recordings were analyzed for T-wave morphology, mean heart rate (HR), HR variability (HRV) and HRV derivatives including mean R-R interval, standard deviation of normal intervals (SDNN) and the root mean square of successive intervals (RMSSD), low (LF) and high frequency (HF) activity and the LF/HF ratio in both fast Fourier transformed and autoregressive spectra. Correlations between ECG variables and recovery score were examined using Spearman's rank correlation.ResultsThere was no significant correlation between preanaesthetic ECG measurements and recovery quality.ConclusionsPredictions of recovery quality after general anaesthesia in horses cannot be based on preanaesthetic ECG variables.Clinical relevanceMeasures other than those based on the ECG should be investigated as predictors of recovery quality.     

Cardiopulmonary effects of sufentanil long acting on sevoflurane anaesthesia in dogs

OBJECTIVE: To evaluate the cardiopulmonary effects of sufentanil long acting (SLA) in sevoflurane-anaesthetized dogs. STUDY DESIGN: Randomized prospective study. Animals Forty female dogs (beagles) aged 1-2 years, weighing 11.97 +/- 1.40 kg. MATERIALS AND METHODS: The dogs were divided into five groups of eight. Two control groups were used: group A received intramuscular (IM), SLA (50 microg kg(-1)) alone, while group B received the SLA vehicle followed by sevoflurane anaesthesia for 90 minutes. In the other groups, SLA (50 microg kg(-1) IM) was given immediately before (group C(0)), 15 minutes before (group D(15)) or 30 minutes (group E(30)) before induction [with intravenous (IV) thiopental] of sevoflurane anaesthesia lasting for 90 minutes. Heart rate, arterial blood pressure, respiratory rate (f(r)), arterial oxygen haemoglobin saturation and end-tidal sevoflurane concentration (Fe'SEVO) were measured every 10 minutes during anaesthesia and at 2, 4 and 24 hours after induction (not Fe'SEVO). Acid-base and blood gas analyses were performed. RESULTS: Sufentanil LA reduced heart rate and increased arterial CO(2) tensions during anaesthesia. Respiratory depression was least in group E(30) compared with groups C(0) and D(15). Bradycardia was present for at least 24 hours. Respiratory rate was least in group B although arterial O(2) and CO(2) tension values were acceptable up to 24 hours after anaesthesia. CONCLUSIONS: Pre-anaesthetic medication with SLA moderately aggravated the cardiopulmonary effects of sevoflurane. CLINICAL RELEVANCE: In spite of a moderate depressant effect on cardiorespiratory parameters, SLA may be of use as pre-anaesthetic medication before sevoflurane anaesthesia in dogs. Intermittent positive pressure ventilation may occasionally be necessary.     

Effects of detomidine or romifidine during maintenance and recovery from isoflurane anaesthesia in horses

ObjectiveTo evaluate the effects of detomidine or romifidine on cardiovascular function, isoflurane requirements and recovery quality in horses undergoing isoflurane anaesthesia.Study designProspective, randomized, blinded, clinical study.AnimalsA total of 63 healthy horses undergoing elective surgery during general anaesthesia.MethodsHorses were randomly allocated to three groups of 21 animals each. In group R, horses were given romifidine intravenously (IV) for premedication (80 μg kg^–1), maintenance (40 μg kg^–1 hour^–1) and before recovery (20 μg kg^–1). In group D2.5, horses were given detomidine IV for premedication (15 μg kg^–1), maintenance (5 μg kg^–1 hour^–1) and before recovery (2.5 μg kg^–1). In group D5, horses were given the same doses of detomidine IV for premedication and maintenance but 5 μg kg^–1 prior to recovery. Premedication was combined with morphine IV (0.1 mg kg^–1) in all groups. Cardiovascular and blood gas variables, expired fraction of isoflurane (Fe′Iso), dobutamine or ketamine requirements, recovery times, recovery events scores (from sternal to standing position) and visual analogue scale (VAS) were compared between groups using either anova followed by Tukey, Kruskal-Wallis followed by Bonferroni or chi-square tests, as appropriate (p < 0.05).ResultsNo significant differences were observed between groups for Fe′Iso, dobutamine or ketamine requirements and recovery times. Cardiovascular and blood gas measurements remained within physiological ranges for all groups. Group D5 horses had significantly worse scores for balance and coordination (p = 0.002), overall impression (p = 0.021) and final score (p = 0.008) than group R horses and significantly worse mean scores for VAS than the other groups (p = 0.002).Conclusions and clinical relevanceDetomidine or romifidine constant rate infusion provided similar conditions for maintenance of anaesthesia. Higher doses of detomidine at the end of anaesthesia might decrease the recovery quality.     

Effect of morphine on the bispectral index during isoflurane anesthesia in dogs

ObjectiveTo assess the effect of morphine on the bispectral index (BIS) in dogs during isoflurane anesthesia maintained at a constant end–tidal concentration.Study designProspective, randomized, experimental trial.AnimalsEight adult Beagle dogs, weighing between 7.1 and 9.8 kg.MethodsAnesthesia was induced with isoflurane via a face mask. Dog's tracheas were intubated and anesthesia maintained with isoflurane at a constant end–tidal concentration (e′Iso) of 1.81% for a 30–minute equilibration period. Pulmonary ventilation was controlled to normocapnia. After equilibration, baseline values were recorded prior to intravenous administration of morphine sulfate (0.5 mg kg^?1) (MT) or an equal volume of saline (CT). Measurements for heart rate, systolic, diastolic and mean arterial pressure (SAP, DAP and MAP) were recorded at 10, 20, 30, 45, 60, 75, 90, 105 and 120 minutes after treatment. Bispectral index was recorded every 10 seconds for 3 minutes for each time measurement. Venous blood samples were collected at baseline, 10, 20, 30, 45, 60 and 120 minutes for determination of morphine serum concentrations. Anesthesia was discontinued after the last measurement and dogs were allowed to recover.ResultsBaseline BIS for MT and CT at 1.81%e′Iso were 63 ± 10 and 58 ± 9, respectively. Bispectral index in MT was 4–8% lower at 20, 75, 90 and 105 minutes compared with CT. There were no differences in BIS between baseline and any subsequent measurement within either MT or CT. Heart rate, SAP, MAP, and DAP decreased after morphine administration.Conclusion and clinical relevanceIntravenous administration of 0.5 mg kg^?1 morphine sulfate did not cause clinically significant changes in the BIS of unstimulated dogs during isoflurane anesthesia at an e′Iso of 1.81%.     

A study of the effect of hemorrhage on the cardiorespiratory actions of halothane, isoflurane and sevoflurane in the dog

OBJECTIVE: To compare the cardiorespiratory changes induced by equipotent concentrations of halothane (HAL), isoflurane (ISO) and sevoflurane (SEVO) before and after hemorrhage. STUDY DESIGN: Prospective, randomized clinical trial. ANIMALS: Twenty-four healthy adult dogs weighing 15.4 +/- 3.4 kg (mean +/- SD). METHODS: Animals were randomly allocated to one of three groups (n = 8 per group). In each group, anesthesia was maintained with 1.5 minimum alveolar concentration of HAL (1.3%), ISO (1.9%) and SEVO (3.5%) in oxygen. Controlled ventilation was performed to maintain eucapnia. Cardiorespiratory variables were evaluated at baseline (between 60 and 90 minutes after induction), immediately after and 30 minutes after the withdrawal of 32 mL kg(-1) of blood (40% of the estimated blood volume) over a 30-minute period. RESULTS: During baseline conditions, ISO and SEVO resulted in higher cardiac index (CI) than HAL. Heart rates were higher with SEVO at baseline, while mean arterial pressure (MAP) and mean pulmonary arterial pressure did not differ between groups. Although heart rate values were higher for ISO and SEVO after hemorrhage, only ISO resulted in a higher CI when compared with HAL. In ISO-anesthetized dogs, MAP was higher immediately after hemorrhage, and this was related to better maintenance of CI and to an increase in systemic vascular resistance index from baseline. CONCLUSIONS: Although the hemodynamic responses of ISO and SEVO are similar in normovolaemic dogs, ISO results in better maintenance of circulatory function during the early period following a massive blood loss. CLINICAL RELEVANCE: Inhaled anesthetics should be used judiciously in animals presented with blood loss. However, if an inhalational agent is to be used under these circumstances, ISO may provide better hemodynamic stability than SEVO or HAL.     

Differences in need for hemodynamic support in horses anesthetized with sevoflurane as compared to isoflurane

OBJECTIVE: To study whether hemodynamic function in horses, particularly mean arterial blood pressure (MAP), is better maintained with sevoflurane than isoflurane, thus requiring less pharmacological support. STUDY DESIGN: Prospective randomized clinical investigation. Animals Thirty-nine racehorses undergoing arthroscopy in lateral recumbency. METHODS: Horses were assigned to receive either isoflurane (n = 20) or sevoflurane (n = 19) at 0.9-1.0 minimum alveolar concentration (MAC) for maintenance of anesthesia. Besides routine clinical monitoring, cardiac output (CO) was measured by lithium dilution. Hemodynamic support was prescribed as follows: when MAP decreased to <70 mmHg, patients were to receive infusion of 0.1% dobutamine, which was to be discontinued at MAP >85 mmHg or heart rate >60 beats minute(-1). Statistical analysis of results, given as mean +/- SD, included a clustered regression approach. RESULTS: Average inhalant anesthetic time [91 +/- 35 (isoflurane group) versus 97 +/- 26 minutes (sevoflurane group)] and dose (in MAC multiples), volume of crystalloid solution infused, and cardiopulmonary parameters including CO were similar in the two groups, except heart rate was 8% higher in isoflurane than sevoflurane horses (p < 0.05). To maintain MAP >70 mmHg, isoflurane horses received dobutamine over a significantly longer period (55 +/- 26 versus 28 +/- 21% of total anesthetic time, p < 0.01) and at a 51% higher dose than sevoflurane horses (41 +/- 19 versus 27 +/- 23 microg kg(-1) MAC hour(-1); p = 0.058), with 14/20 isoflurane animals and only 9/19 sevoflurane horses being infused with dobutamine at >30 microg kg(-1) MAC hour(-1) (p < 0.05). Dobutamine infusion rates were consistently lower in the sevoflurane as compared to the isoflurane group, with differences reaching significance level during the 0-30 minutes (p < 0.01) and 61-90 minutes periods (p < 0.05). CONCLUSIONS AND CLINICAL RELEVANCE: Horses under sevoflurane anesthesia may require less pharmacological support in the form of dobutamine than isoflurane-anesthetized horses. This could be due to less suppression of vasomotor tone.     

Serum biochemical indicators of hepatobiliary function in dogs following prolonged anaesthesia with sevoflurane or isoflurane

Objective To investigate the changes in serum enzymes considered as biochemical indicators of hepatobiliary function in dogs following 5 hours of anaesthesia with isoflurane (ISO) or sevoflurane (SEVO). Study design Experimental randomized crossover study, with intervals of at least 15 days between successive treatments. Animals Eight healthy adult mongrel dogs, four male, four female, weight 13.6–21.6 kg. Methods Treatments consisted of anaesthesia with ISO or SEVO at 1 or 1.5 minimum alveolar concentration (MAC) delivered in oxygen. MAC was taken as 1.39% for ISO and 2.36% for SEVO. Anaesthesia was induced by mask then, after endotracheal intubation, maintained according to the treatment protocol using a small animal circle system. Cardiopulmonary monitoring was carried out. Venous blood samples, obtained by needle puncture, were taken at 24 hours and 2, 7 and 14 days post anaesthesia. Serum concentrations of total protein, aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase, (LDH), alkaline phosphatase (ALP), gamma‐glutamyltransferese and total bilirubin were measured. Changes with time and with treatment were compared by Friedman analysis, Wilcoxon Signed test and Kruskal‐Wallis test as relevant. p‐ value < 0.05 was considered significant. Results Compared to base‐line values, at 24 hours post‐anaesthesia there were significant increases in AST, ALT, ALP and LDH following one or more of the treatments, but by 2 days residual changes were not significant. At 24 hours, AST for treatment 1.5 MAC ISO was higher than 1 MAC ISO (p < 0.002), and LDH higher for 1.5 MAC SEVO than 1 MAC SEVO. Conclusion and clinical relevance Both ISO and SEVO, at concentrations used for clinical anaesthesia, produce transient moderate effects on some hepatobiliary enzyme concentrations in dogs.     

Effects of hypercapnic hyperpnea on recovery from isoflurane or sevoflurane anesthesia in horses

Objective To test the hypothesis that hypercapnic hyperpnea produced using endotracheal insufflation with 5–10% CO₂ in oxygen could be used to shorten anesthetic recovery time in horses, and that recovery from sevoflurane would be faster than from isoflurane. Study design Randomized crossover study design. Animals Eight healthy adult horses. Methods After 2 hours’ administration of constant 1.2 times MAC isoflurane or sevoflurane, horses were disconnected from the anesthetic circuit and administered 0, 5, or 10% CO₂ in balance O₂ via endotracheal tube insufflation. End‐tidal gas samples were collected to measure anesthetic washout kinetics, and arterial and venous blood samples were collected to measure respiratory gas partial pressures. Horses recovered in padded stalls without assistance, and each recovery was videotaped and evaluated by reviewers who were blinded to the anesthetic agent and insufflation treatment used. Results Compared to isoflurane, sevoflurane caused greater hypoventilation and was associated with longer times until standing recovery. CO₂ insufflation significantly decreased anesthetic recovery time compared to insufflation with O₂ alone without significantly increasing PaCO₂. Pharmacokinetic parameters during recovery from isoflurane with CO₂ insufflation were statistically indistinguishable from sevoflurane recovery without CO₂. Neither anesthetic agent nor insufflation treatment affected recovery quality from anesthesia. Conclusions and clinical relevance Hypercapnic hyperpnea decreases time to standing without influencing anesthetic recovery quality. Although the lower blood gas solubility of sevoflurane should favor a shorter recovery time compared to isoflurane, this advantage is negated by the greater respiratory depression from sevoflurane in horses.     

Intravenous sufentanil‐midazolam versus sevoflurane anaesthesia in medetomidine pre‐medicated Himalayan rabbits undergoing ovariohysterectomy

ObjectiveTo compare physiological effects of sufentanil-midazolam with sevoflurane for surgical anaesthesia in medetomidine premedicated rabbits.Study designProspective, randomized controlled experimental study.AnimalsEighteen female Himalayan rabbits, weight 2.1 ± 0.1 kg.MethodsPremedication with 0.1 mg kg⁻¹ medetomidine and 5 mg kg⁻¹ carprofen subcutaneously, was followed by intravenous anaesthetic induction with sufentanil (2.3 μg mL⁻¹) and midazolam (0.45 mg mL⁻¹). After endotracheal intubation, anaesthesia was maintained with sufentanil-midazolam (n = 9) or sevoflurane (n = 9). Ovariohysterectomy was performed. Intermittent positive pressure ventilation was performed as required. Physiological variables were studied perioperatively. Group means of physiologic data were generated for different anaesthetic periods. Data were compared for changes from sedation, and between groups by anova. Post-operatively, 0.05 mg kg⁻¹ buprenorphine was administered once and 5 mg kg⁻¹ carprofen once daily for 2–3 days. Rabbits were examined and weighed daily until one week after surgery.ResultsSmooth induction of anaesthesia was achieved within 5 minutes. Sufentanil and midazolam doses were 0.5 μg kg⁻¹ and 0.1 mg kg⁻¹, during induction and 3.9 μg kg⁻¹ hour⁻¹ and 0.8 mg kg⁻¹ hour⁻¹ during surgery, respectively. End-tidal sevoflurane concentration was 2.1% during surgery. Assisted ventilation was required in nine rabbits receiving sufentanil-midazolam and four receiving sevoflurane. There were no differences between groups in physiologic data other than arterial carbon dioxide. In rabbits receiving sevoflurane, mean arterial pressure decreased pre-surgical intervention, heart rate increased 25% during and after surgery and body weight decreased 4% post-operatively. Post-operative problems sometimes resulted from catheterization of the ear artery.ConclusionSevoflurane and sufentanil-midazolam provided surgical anaesthesia of similar quality. Arterial blood pressure was sustained during sufentanil-midazolam anaesthesia and rabbits receiving sevoflurane lost body weight following ovariohysterectomy. Mechanical ventilation was required with both anaesthetic regimens.Clinical relevanceAnaesthesia with sufentanil-midazolam in medetomidine premedicated healthy rabbits is useful in the clinical and the research setting, as an alternative to sevoflurane.