The cardiopulmonary effects of anesthetic induction with isoflurane,ketamine‐diazepam or propofol‐diazepam in the hypovolemic dog

ObjectiveTo evaluate and compare the cardiopulmonary effects of induction of anesthesia with isoflurane (Iso), ketamine–diazepam (KD), or propofol–diazepam (PD) in hypovolemic dogs.Study designProspective randomized cross–over trial.AnimalsSix healthy intact, mixed breed, female dogs weighing 20.7 ± 4.2 kg and aged 22 ± 2 months.MethodsDogs had 30 mL kg^?1 of blood removed at a rate of 1.5 mL kg^?1 minute^?1 under isoflurane anesthesia. Following a 30–minute recovery period, anesthesia was reinduced. Dogs were assigned to one of three treatments: isoflurane via facemask using 0.5% incremental increases in the delivered concentration every 30 seconds, 1.25 mg kg^?1 ketamine and 0.0625 mg kg^?1 diazepam intravenously (IV) with doses repeated every 30 seconds as required, and 2 mg kg^?1 propofol and 0.2 mg kg^?1 diazepam IV followed by 1 mg kg^?1 propofol increments IV every 30 seconds as required. Following endotracheal intubation all dogs received 1.7% end–tidal isoflurane in oxygen. Cardiopulmonary variables were recorded at baseline (before induction) and at 5 or 10 minute intervals following endotracheal intubation.ResultsInduction time was longer in Iso (4.98 ± 0.47 minutes) compared to KD (3.10 ± 0.47 minutes) or PD (3.22 ± 0.45 minutes). To produce anesthesia, KD received 4.9 ± 2.3 mg kg^?1 ketamine and 0.24 ± 0.1 mg kg^?1 diazepam, while PD received 2.2 ± 0.4 mg kg^?1 propofol and 0.2 mg kg^?1 diazepam. End–tidal isoflurane concentration immediately following intubation was 1.7 ± 0.4% in Iso. Arterial blood pressure and heart rate were significantly higher in KD and PD compared to Iso and in KD compared to PD. Arterial carbon dioxide partial pressure was significantly higher in PD compared to KD and Iso immediately after induction.Conclusions and clinical relevanceIn hypovolemic dogs, KD or PD, as used in this study to induce anesthesia, resulted in less hemodynamic depression compared to isoflurane.     

Fentanyl or midazolam for co-induction of anaesthesia with propofol in dogs

ObjectivePropofol may cause adverse effects (e.g. apnoea, hypotension) at induction of anaesthesia. Co-induction of anaesthesia may reduce propofol requirements. The effect of fentanyl or midazolam on propofol dose requirements and cardiorespiratory parameters was studied.Study designRandomized, controlled, blinded clinical study.AnimalsSixty-six client owned dogs (35 male, 31 female, ASA I-II, age 6–120 months, body mass 4.7–48.0 kg) were selected.MethodsPre-medication with acepromazine (0.025 mg kg⁻¹) and morphine (0.25 mg kg⁻¹) was administered by intramuscular injection. After 30 minutes group fentanyl-propofol (FP) received fentanyl (2 μg kg⁻¹), group midazolam-propofol (MP) midazolam (0.2 mg kg⁻¹) injected over 30 seconds via a cephalic catheter and in a third group, control-propofol (CP), the IV catheter was flushed with an equivalent volume of heparinized saline. Anaesthesia was induced 2 minutes later, with propofol (4 mg kg⁻¹minute⁻¹) administered to effect. After endotracheal intubation anaesthesia was maintained with a standardized anaesthetic protocol. Pulse rate, respiratory rate (RR) and mean arterial pressure (MAP) were recorded before the co-induction agent, before induction, and 0, 2 and 5 minutes after intubation. Apnoea ≥30 seconds was recorded and treated. Sedation after pre-medication, activity after the co-induction agent, quality of anaesthetic induction and endotracheal intubation were scored.ResultsPropofol dose requirement was significantly reduced in FP [2.90 mg kg⁻¹(0.57)] compared to CP [3.51 mg kg⁻¹ (0.74)] and MP [3.58 mg kg⁻¹(0.49)]. Mean pulse rate was higher in MP than in CP or FP (p = 0.003). No statistically significant difference was found between groups in mean RR, MAP or incidence of apnoea. Activity score was significantly higher (i.e. more excited) (p = 0.0001), and quality of induction score was significantly poorer (p = 0.0001) in MP compared to CP or FP. Intubation score was similar in all groups.Conclusions and clinical relevanceFentanyl decreased propofol requirement but did not significantly alter cardiovascular parameters. Midazolam did not reduce propofol requirements and caused excitement in some animals.     

Heart rate,arterial pressure and propofol-sparing effects of guaifenesin in dogs

ObjectiveTo evaluate the heart rate (HR) and systemic arterial pressure (sAP) effects, and propofol induction dose requirements in healthy dogs administered propofol with or without guaifenesin for the induction of anesthesia.Study designProspective blinded crossover experimental study.AnimalsA total of 10 healthy adult female Beagle dogs.MethodsDogs were premedicated with intravenous (IV) butorphanol (0.4 mg kg^–1) and administered guaifenesin 5% at 50 mg kg^–1 (treatment G50), 100 mg kg^–1 (treatment G100) or saline (treatment saline) IV prior to anesthetic induction with propofol. HR, invasive sAP and respiratory rate (f_R) were recorded after butorphanol administration, after guaifenesin administration and after propofol and endotracheal intubation. Propofol doses for intubation were recorded. Repeated measures analysis of variance (anova) was used to determine differences in propofol dose requirements among treatments, and differences in cardiopulmonary values over time and among treatments with p < 0.05 considered statistically significant.ResultsPropofol doses (mean ± standard deviation) for treatments saline, G50 and G100 were 3.3 ± 1.0, 2.7 ± 0.7 and 2.1 ± 0.8 mg kg^–1, respectively. Propofol administered was significantly lower in treatment G100 than in treatment saline (p = 0.04). In treatments G50 and G100, HR increased following induction of anesthesia and intubation compared with baseline measurements. HR was higher in treatment G100 than in treatments G50 and saline following induction of anesthesia. In all treatments, sAP decreased following intubation compared with baseline values. There were no significant differences in sAP among treatments. f_R was lower following intubation than baseline and post co-induction values and did not differ significantly among treatments.Conclusions and clinical relevanceWhen administered as a co-induction agent in dogs, guaifenesin reduced propofol requirements for tracheal intubation. HR increased and sAP and f_R decreased, but mean values remained clinically acceptable.     

Midazolam,as a co‐induction agent,has propofol sparing effects but also decreases systolic blood pressure in healthy dogs

ObjectiveTo evaluate the effects of the co-administration of midazolam on the dose requirement for propofol anesthesia induction, heart rate (HR), systolic arterial pressure (SAP) and the incidence of excitement.Study designProspective, randomized, controlled and blinded clinical study, with owner consent.AnimalsSeventeen healthy, client owned dogs weighing 28 ± 18 kg and aged 4.9 ± 3.9 years old.MethodsDogs were sedated with acepromazine 0.025 mg kg^?1 and morphine 0.25 mg kg^?1 intramuscularly (IM), 30 minutes prior to induction of anesthesia. Patients were randomly allocated to receive midazolam (MP; 0.2 mg kg^?1) or sterile normal saline (CP; 0.04 mL kg^?1) intravenously (IV) over 15 seconds. Propofol was administered IV immediately following test drug and delivered at 3 mg kg^?1 minute^?1 until intubation was possible. Scoring of pre-induction sedation, ease of intubation, quality of induction, and presence or absence of excitement following co-induction agent, was recorded. HR, SAP and respiratory rate (f_R) were obtained immediately prior to, immediately following, and 5 minutes following induction of anesthesia.ResultsThere were no significant differences between groups with regard to weight, age, gender, or sedation. Excitement occurred in 5/9 dogs following midazolam administration, with none noted in the control group. The dose of propofol administered to the midazolam group was significantly less than in the control group. Differences in HR were not significant between groups. SAP was significantly lower in the midazolam group compared with baseline values 5 minutes after its administration. However, values remained clinically acceptable.Conclusions and clinical relevanceThe co-administration of midazolam with propofol decreased the total dose of propofol needed for induction of anesthesia in sedated healthy dogs, caused some excitement and a clinically unimportant decrease in SAP.     

A comparison of induction of anaesthesia using a target-controlled infusion device in dogs with propofol or a propofol and alfentanil admixture

ObjectiveTo compare induction targets, and the haemodynamic and respiratory effects, of propofol, or as an admixture with two different concentrations of alfentanil, delivered via a propofol target-controlled infusion (TCI) system.Study designProspective blinded randomized clinical study.Animals Sixty client-owned dogs scheduled for elective surgery under general anaesthesia. Mean body mass (SD) 28.5 kg (8.7) and mean age (SD) 3.5 years (2.4).MethodsDogs received pre-anaesthetic medication of acepromazine (0.03 mg kg⁻¹) and morphine (0.2 mg kg⁻¹) administered intramuscularly. Animals were randomly assigned to receive one of three induction protocols: propofol alone (group 1), a propofol/alfentanil (11.9 μg mL⁻¹) admixture (group 2), or a propofol/alfentanil (23.8 μg mL⁻¹) admixture (group 3), via a TCI system. Blood target concentrations were increased until endotracheal intubation was achieved, and induction targets were recorded. Heart rate (HR), respiratory rate (f_r) and non-invasive arterial blood pressure were recorded pre-induction, at endotracheal intubation (time 0) and at 3 and 5 minutes post-intubation (times 3 and 5, respectively). Data were analysed using anova for normally distributed data or Kruskal–Wallis test, with significance assumed at p < 0.05.ResultsThere were no significant differences between groups with respect to age, body mass, HR, f_r, systolic and diastolic blood pressure. The blood propofol targets to achieve endotracheal intubation were significantly higher in group 1 compared with groups 2 and 3. Mean arterial blood pressure (MAP) was significantly higher in group 1 at time 0 when compared with groups 2 and 3.Conclusions and clinical relevanceInduction of anaesthesia with a TCI system can be achieved at lower blood propofol targets when using a propofol/alfentanil admixture compared with using propofol alone. However, despite reduced targets with both propofol/alfentanil admixture groups, MAP was lower immediately following endotracheal intubation than when using propofol alone.     

An evaluation of anaesthetic induction in healthy dogs using rapid intravenous injection of propofol or alfaxalone

ObjectiveTo evaluate quality of anaesthetic induction and cardiorespiratory effects following rapid intravenous (IV) injection of propofol or alfaxalone.Study designProspective, randomised, blinded clinical study.AnimalsSixty healthy dogs (ASA I/II) anaesthetized for elective surgery or diagnostic procedures.MethodsPremedication was intramuscular acepromazine (0.03 mg kg^?1) and meperidine (pethidine) (3 mg kg^?1). For anaesthetic induction dogs received either 3 mg kg^?1 propofol (Group P) or 1.5 mg kg^?1 alfaxalone (Group A) by rapid IV injection. Heart rate (HR), respiratory rate (f_R) and oscillometric arterial pressures were recorded prior to induction, at endotracheal intubation and at 3 and 5 minutes post-intubation. The occurrence of post-induction apnoea or hypotension was recorded. Pre-induction sedation and aspects of induction quality were scored using 4 point scales. Data were analysed using Chi-squared tests, two sample t-tests and general linear model mixed effect anova (p < 0.05).ResultsThere were no significant differences between groups with respect to sex, age, body weight, f_R, post-induction apnoea, arterial pressures, hypotension, SpO₂, sedation score or quality of induction scores. Groups behaved differently over time with respect to HR. On induction HR decreased in Group P (?2 ± 28 beats minute^?1) but increased in Group A (14 ± 33 beats minute^?1) the difference being significant (p = 0.047). However HR change following premedication also differed between groups (p = 0.006). Arterial pressures decreased significantly over time in both groups and transient hypotension occurred in eight dogs (five in Group P, three in Group A). Post-induction apnoea occurred in 31 dogs (17 in Group P, 14 in Group A). Additional drug was required to achieve endotracheal intubation in two dogs.Conclusions and Clinical relevanceRapid IV injection of propofol or alfaxalone provided suitable conditions for endotracheal intubation in healthy dogs but post-induction apnoea was observed commonly.     

Dose and cardiopulmonary effects of propofol alone or with midazolam for induction of anesthesia in critically ill dogs

ObjectiveTo determine the dose and cardiopulmonary effects of propofol alone or with midazolam for induction of anesthesia in American Society of Anesthesiologists status ≥III dogs requiring emergency abdominal surgery.Study designProspective, randomized, blinded, clinical trial.AnimalsA total of 19 client-owned dogs.MethodsDogs were sedated with fentanyl (2 μg kg^–1) intravenously (IV) for instrumentation for measurement of heart rate, arterial blood pressure, cardiac index, systemic vascular resistance index, arterial blood gases, respiratory rate and rectal temperature. After additional IV fentanyl (3 μg kg^–1), the quality of sedation was scored and cardiopulmonary variables recorded. Induction of anesthesia was with IV propofol (1 mg kg^–1) and saline (0.06 mL kg^–1; group PS; nine dogs) or midazolam (0.3 mg kg^–1; group PM; 10 dogs), with additional propofol (0.25 mg kg^–1) IV every 6 seconds until endotracheal intubation. Induction/intubation quality was scored, and anesthesia was maintained with isoflurane. Variables were recorded for 5 minutes with the dog in lateral recumbency, breathing spontaneously, and then in dorsal recumbency with mechanical ventilation for the next 15 minutes. A general linear mixed model was used with post hoc analysis for multiple comparisons between groups (p < 0.05).ResultsThere were no differences in group demographics, temperature and cardiopulmonary variables between groups or within groups before or after induction. The propofol doses for induction of anesthesia were significantly different between groups, 1.9 ± 0.5 and 1.1 ± 0.5 mg kg^–1 for groups PS and PM, respectively, and the induction/intubation score was significantly better for group PM.Conclusions and clinical relevanceMidazolam co-induction reduced the propofol induction dose and improved the quality of induction in critically ill dogs without an improvement in cardiopulmonary variables, when compared with a higher dose of propofol alone.     

The effect of body condition on propofol requirement in dogs

ObjectiveTo determine if body condition score (BCS) influences the sedative effect of intramuscular (IM) premedication or the dose of intravenous (IV) propofol required to achieve endotracheal intubation in dogs.Study designProspective clinical study.AnimalsForty–six client–owned dogs undergoing general anaesthesia.MethodsDogs were allocated to groups according to their BCS (BCS, 1 [emaciated] to 9 [obese]): Normal–weight Group (NG, n = 25) if BCS 4–5 or Over–weight Group (OG, n = 21) if BCS over 6. Dogs were scored for sedation prior to IM injection of medetomidine (5 μg kg^?1) and butorphanol (0.2 mg kg^?1) and twenty minutes later anaesthesia was induced by a slow infusion of propofol at 1.5 mg kg^?1 minute^?1 until endotracheal intubation could be achieved. The total dose of propofol administered was recorded. Data were tested for normality then analyzed using Student t–tests, Mann–Whitney U tests, chi–square tests or linear regression as appropriate.ResultsMean ( ± SD) propofol requirement in NG was 2.24 ± 0.53 mg kg^?1 and in OG was 1.83 ± 0.36 mg kg^?1. The difference between the groups was statistically significant (p = 0.005). The degree of sedation was not different between the groups (p = 0.7). Post–induction apnoea occurred in 11 of 25 animals in the NG and three of 21 in OG (p = 0.052).ConclusionsOverweight dogs required a lower IV propofol dose per kg of total body mass to allow tracheal intubation than did normal body condition score animals suggesting that IV anaesthetic doses should be calculated according to lean body mass. The lower dose per kg of total body mass may have resulted in less post–induction apnoea in overweight/obese dogs. The effect of IM premedication was not significantly affected by the BCS.Clinical relevanceInduction of general anaesthesia with propofol in overweight dogs may be expected at lower doses than normal–weight animals.     

A dose titration study into the effects of diazepam or midazolam on the propofol dose requirements for induction of general anaesthesia in client owned dogs,premedicated with methadone and acepromazine

ObjectiveTo assess the effect of a benzodiazepine co–induction on propofol dose requirement for induction of anaesthesia in healthy dogs, to describe any differences between midazolam and diazepam and to determine an optimal benzodiazepine dose for co–induction.Study designProspective, randomised, blinded placebo controlled clinical trial.AnimalsNinety client owned dogs (ASA I–III, median body mass 21.5kg (IQR 10–33)) presented for anaesthesia for a variety of procedures.MethodsDogs were randomised to receive saline 0.1 mL kg^?1, midazolam or diazepam at 0.2, 0.3, 0.4 or 0.5 mg kg^?1. All dogs received 0.01 mg kg^?1 acepromazine and 0.2 mg kg^?1 methadone intravenously (IV). Fifteen minutes later, sedation was assessed and scored prior to anaesthetic induction. Propofol, 1 mg kg^?1, was administered IV, followed by the treatment drug. Further propofol was administered until endotracheal intubation was possible. Recorded data included patient signalment, sedation score, propofol dosage and any adverse reactions.ResultsMidazolam (all groups combined) significantly reduced propofol dose requirement compared to saline (p < 0.001) and diazepam (p = 0.008). Midazolam (0.4 mg kg^?1) significantly reduced propofol dose requirement (p = 0.014) compared to saline, however other doses failed to reach statistical significance. Diazepam did not significantly reduce propofol dose requirement compared to saline (p = 0.089). Dogs weighing <5 kg, regardless of treatment group, required a greater propofol dose than those weighing 5–40 kg (p = 0.002) and those >40 kg (p = 0.008). Dogs which were profoundly sedated required less propofol than those which were mildly sedated (p < 0.001) and adequately sedated (p = 0.003).Conclusions and clinical relevanceMidazolam (0.4 mg kg^?1) given IV after 1 mg kg^?1 of propofol significantly reduced the further propofol dose required for intubation compared to saline. At the investigated doses, diazepam did not have significant propofol dose sparing effects.     

Evaluation of different doses of propofol in xylazine pre-medicated horses

Objective To characterize responses to different doses of propofol in horses pre‐medicated with xylazine. Animals Six adult horses (five females and one male). Methods Each horse was anaesthetized four times with either ketamine or propofol in random order at 1‐week intervals. Horses were pre‐medicated with xylazine (1.1 mg kg^?1 IV over a minute), and 5 minutes later anaesthesia was induced with either ketamine (2.2 mg kg^?1 IV) or propofol (1, 2 and 4 mg kg^?1 IV; low, medium and high doses, respectively). Data were collected continuously (electrocardiogram) or after xylazine administration and at 5, 10 and 15 minutes after anaesthetic induction (arterial pressure, respiratory rate, pH, PaO₂, PaCO₂ and O₂ saturation). Anaesthetic induction and recovery were qualitatively and quantitatively assessed. Results Differences in the quality of anaesthesia were observed; the low dose of propofol resulted in a poorer anaesthetic induction that was insufficient to allow intubation, whereas the high dose produced an excellent quality of induction, free of excitement. Recorded anaesthesia times were similar between propofol at 2 mg kg^?1 and ketamine with prolonged and shorter recovery times after the high and low dose of propofol, respectively (p < 0.05; ketamine, 38 ± 7 minutes; propofol 1 mg kg^?1, 29 ± 4 minutes; propofol 2 mg kg^?1, 37 ± 5 minutes; propofol 4 mg kg^?1, 50 ± 7 minutes). Times to regain sternal and standing position were longest with the highest dose of propofol (32 ± 5 and 39 ± 7 minutes, respectively). Both ketamine and propofol reversed bradycardia, sinoatrial, and atrioventricular blocks produced by xylazine. There were no significant alterations in blood pressure but respiratory rate, and PaO₂ and O₂ saturation were significantly decreased in all groups (p < 0.05). Conclusion The anaesthetic quality produced by the three propofol doses varied; the most desirable effects, which were comparable to those of ketamine, were produced by 2 mg kg^?1 propofol.     

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

ObjectiveTo evaluate the clinical efficacy and cardiorespiratory effects of alfaxalone as an anaesthetic induction agent in dogs with moderate to severe systemic disease.Study designRandomized prospective clinical study.AnimalsForty dogs of physical status ASA III-V referred for various surgical procedures.MethodsDogs 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).ResultsTreatment 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 relevanceInduction 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.     

Comparison of propofol with ketofol,a propofol‐ketamine admixture,for induction of anaesthesia in healthy dogs

ObjectiveTo compare anaesthetic induction in healthy dogs using propofol or ketofol (a propofol-ketamine mixture).Study designProspective, randomized, controlled, ‘blinded’ study.AnimalsSeventy healthy dogs (33 males and 37 females), aged 6–157 months and weighing 4–48 kg.MethodsFollowing premedication, either propofol (10 mg mL^?1) or ketofol (9 mg propofol and 9 mg ketamine mL^?1) was titrated intravenously until laryngoscopy and tracheal intubation were possible. Pulse rate (PR), respiratory rate (f_R) and arterial blood pressure (ABP) were compared to post-premedication values and time to first breath (TTFB) recorded. Sedation quality, tracheal intubation and anaesthetic induction were scored by an observer who was unaware of treatment group. Mann–Whitney or t-tests were performed and significance set at p = 0.05.ResultsInduction mixture volume (mean ± SD) was lower for ketofol (0.2 ± 0.1 mL kg^?1) than propofol (0.4 ± 0.1 mL kg^?1) (p < 0.001). PR increased following ketofol (by 35 ± 20 beats minute^?1) but not consistently following propofol (4 ± 16 beats minute^?1) (p < 0.001). Ketofol administration was associated with a higher mean arterial blood pressure (MAP) (82 ± 10 mmHg) than propofol (77 ± 11) (p = 0.05). TTFB was similar, but ketofol use resulted in a greater decrease in f_R (median (range): ketofol -32 (-158 to 0) propofol -24 (-187 to 2) breaths minute^?1) (p < 0.001). Sedation was similar between groups. Tracheal intubation and induction qualities were better with ketofol than propofol (p = 0.04 and 0.02 respectively).Conclusion and clinical relevanceInduction of anaesthesia with ketofol resulted in higher PR and MAP than when propofol was used, but lower f_R. Quality of induction and tracheal intubation were consistently good with ketofol, but more variable when using propofol.     

Comparison of racemic ketamine and S-ketamine as agents for the induction of anaesthesia in goats

ObjectiveTo compare racemic ketamine and S-ketamine as induction agents prior to isoflurane anaesthesia.Study designProspective, blinded, randomized experimental study.AnimalsThirty-one healthy adult goats weighing 39-86 kg.MethodsGoats were premedicated with xylazine (0.1 mg kg^?1) intravenously (IV) given over 5 minutes. Each goat was assigned randomly to one of two treatments for IV anaesthetic induction: group RK (15 goats) racemic ketamine (3 mg kg^?1) and group SK (16 goats) S-ketamine (1.5 mg kg^?1). Time from end-injection to recumbency was measured and quality of anaesthetic induction and condition for endotracheal intubation were scored. Anaesthesia was maintained with isoflurane in oxygen for 90 minutes. Heart rate, invasive arterial blood pressure, oxygen saturation, temperature, end-tidal carbon dioxide and isoflurane were recorded every 5 minutes. Arterial blood samples were taken for analysis every 30 minutes. Recovery time to recurrence of swallowing reflex, to first head movement and to standing were recorded and recovery quality was scored. Two-way repeated measures anova, Mann-Whitney and a Mantel-Cox tests were used for statistical analysis as relevant with a significance level set at p < 0.05.ResultsInduction of anaesthesia was smooth and uneventful in all goats. There was no statistical difference between groups in any measured parameter. Side effects following anaesthetic induction included slight head or limb twitching, moving forward and backward, salivation and nystagmus but were minimal. Endotracheal intubation was achieved in all goats at first or second attempt. Recovery was uneventful on all occasions. All goats were quiet and needed only one or two attempts to stand.Conclusions and clinical relevanceS-ketamine at half the dose rate of racemic ketamine in goats sedated with xylazine and thereafter anaesthetised with isoflurane induces the same clinically measurable effects.     

Comparison between continuous rate infusion and target-controlled infusion of propofol in dogs: a randomized clinical trial

ObjectiveTo compare a propofol continuous rate infusion (CRI) with a target-controlled infusion (TCI) in dogs.Study designRandomized prospective double-blinded clinical study.AnimalsA total of 38 healthy client-owned dogs.MethodsDogs premedicated intramuscularly with acepromazine (0.03 mg kg^–1) and an opioid (pethidine 3 mg kg^–1, morphine 0.2 mg kg^–1 or methadone 0.2 mg kg^–1) were allocated to P-CRI group (propofol 4 mg kg^–1 intravenously followed by CRI at 0.2 mg kg^–1 minute^–1), or P-TCI group [propofol predicted plasma concentration (Cp) of 3.5 μg mL^–1 for induction and maintenance of anaesthesia via TCI]. Plane of anaesthesia, heart rate, respiratory rate, invasive blood pressure, oxygen haemoglobin saturation, end-tidal carbon dioxide and body temperature were monitored by an anaesthetist blinded to the group. Numerical data were analysed by unpaired t test or Mann–Whitney U test, one-way analysis of variance and Dunnett’s post hoc test. Categorical data were analysed with Fisher’s exact test. Significance was set for p < 0.005.ResultsOverall, propofol induced a significant incidence of relative hypotension (mean arterial pressure 20% below baseline, 45%), apnoea (71%) and haemoglobin desaturation (65%) at induction of anaesthesia, with a higher incidence of hypotension and apnoea in the P-CRI than P-TCI group (68% versus 21%, p = 0.008; 84% versus 58%, p = 0.0151, respectively). Propofol Cp was significantly higher at intubation in the P-CRI than P-TCI group (4.83 versus 3.5 μg mL^–1, p < 0.0001), but decreased during infusion, while Cp remained steady in the P-TCI group. Total propofol administered was similar between groups.Conclusions and clinical relevanceBoth techniques provided a smooth induction of anaesthesia but caused a high incidence of side effects. Titration of anaesthesia with TCI caused fewer fluctuations in Cp and lower risk of hypotension compared with CRI.     

Effects of ketamine or midazolam continuous rate infusions on alfaxalone total intravenous anaesthesia requirements and recovery quality in healthy dogs: a randomized clinical trial

ObjectiveTo determine the alfaxalone dose reduction during total intravenous anaesthesia (TIVA) when combined with ketamine or midazolam constant rate infusions and to assess recovery quality in healthy dogs.Study designProspective, blinded clinical study.AnimalsA group of 33 healthy, client-owned dogs subjected to dental procedures.MethodsAfter premedication with intramuscular acepromazine 0.05 mg kg^-1 and methadone 0.3 mg kg^-1, anaesthetic induction started with intravenous alfaxalone 0.5 mg kg^-1 followed by either lactated Ringer’s solution (0.04 mL kg^-1, group A), ketamine (2 mg kg^-1, group AK) or midazolam (0.2 mg kg^-1, group AM) and completed with alfaxalone until endotracheal intubation was achieved. Anaesthesia was maintained with alfaxalone (6 mg kg^-1 hour^-1), adjusted (±20%) every 5 minutes to maintain a suitable level of anaesthesia. Ketamine (0.6 mg kg^-1 hour^-1) or midazolam (0.4 mg kg^-1 hour^-1) were employed for anaesthetic maintenance in groups AK and AM, respectively. Physiological variables were monitored during anaesthesia. Times from alfaxalone discontinuation to extubation, sternal recumbency and standing position were calculated. Recovery quality and incidence of adverse events were recorded. Groups were compared using parametric analysis of variance and nonparametric (Kruskal-Wallis, Chi-square, Fisher’s exact) tests as appropriate, p < 0.05.ResultsMidazolam significantly reduced alfaxalone induction and maintenance doses (46%; p = 0.034 and 32%, p = 0.012, respectively), whereas ketamine only reduced the alfaxalone induction dose (30%; p = 0.010). Recovery quality was unacceptable in nine dogs in group A, three dogs in group AK and three dogs in group AM.Conclusions and clinical relevanceMidazolam, but not ketamine, reduced the alfaxalone infusion rate, and both co-adjuvant drugs reduced the alfaxalone induction dose. Alfaxalone TIVA allowed anaesthetic maintenance for dental procedures in dogs, but the quality of anaesthetic recovery remained unacceptable irrespective of its combination with ketamine or midazolam.     

Minimum infusion rate and hemodynamic effects of propofol, propofol-lidocaine and propofol-lidocaine-ketamine in dogs

ObjectiveTo evaluate the effects of a constant rate infusion (CRI) of lidocaine alone or in combination with ketamine on the minimum infusion rate (MIR) of propofol in dogs and to compare the hemodynamic effects produced by propofol, propofol-lidocaine or propofol-lidocaine-ketamine anesthesia.Study designProspective, randomized cross-over experimental design.AnimalsFourteen adult mixed-breed dogs weighing 15.8 ± 3.5 kg.MethodsEight dogs were anesthetized on different occasions to determine the MIR of propofol alone and propofol in combination with lidocaine (loading dose [LD] 1.5 mg kg^?1, CRI 0.25 mg kg^?1 minute^?1) or lidocaine (LD 1.5 mg kg^?1, CRI 0.25 mg kg^?1 minute^?1) and ketamine (LD 1 mg kg^?1, CRI 0.1 mg kg^?1 minute^?1). In six other dogs, the hemodynamic effects and bispectral index (BIS) were investigated. Each animal received each treatment (propofol, propofol-lidocaine or propofol-lidocaine-ketamine) on the basis of the MIR of propofol determined in the first set of experiments.ResultsMean ± SD MIR of propofol was 0.51 ± 0.08 mg kg^?1 minute^?1. Lidocaine-ketamine significantly decreased the MIR of propofol to 0.31 ± 0.07 mg kg^?1 minute^?1 (37 ± 18% reduction), although lidocaine alone did not (0.42 ± 0.08 mg kg^?1 minute^?1, 18 ± 7% reduction). Hemodynamic effects were similar in all treatments. Compared with the conscious state, in all treatments, heart rate, cardiac index, mean arterial blood pressure, stroke index and oxygen delivery index decreased significantly, whereas systemic vascular resistance index increased. Stroke index was lower in dogs treated with propofol-lidocaine-ketamine at 30 minutes compared with propofol alone. The BIS was lower during anesthesia with propofol-lidocaine-ketamine compared to propofol alone.Conclusions and clinical relevanceLidocaine-ketamine, but not lidocaine alone, reduced the MIR of propofol in dogs. Neither lidocaine nor lidocaine in combination with ketamine attenuated cardiovascular depression produced by a continuous rate infusion of propofol.     

Total intravenous anaesthesia by boluses or by continuous rate infusion of propofol in mute swans (Cygnus olor)

ObjectiveTo investigate intravenous (IV) propofol given by intermittent boluses or by continuous rate infusion (CRI) for anaesthesia in swans.Study designProspective randomized clinical study.AnimalsTwenty mute swans (Cygnus olor) (eight immature and 12 adults) of unknown sex undergoing painless diagnostic or therapeutic procedures.MethodsInduction of anaesthesia was with 8 mg kg^?1 propofol IV. To maintain anaesthesia, ten birds (group BOLI) received propofol as boluses, whilst 10 (group CRI) received propofol as a CRI. Some physiological parameters were measured. Anaesthetic duration was 35 minutes. Groups were compared using Mann–Whitney U-test. Results are median (range).ResultsAnaesthetic induction was smooth and tracheal intubation was achieved easily in all birds. Bolus dose in group BOLI was 2.9 (1.3–4.3) mg kg^?1; interval between and number of boluses required were 4 (1–8) minutes and 6 (4–11) boluses respectively. Total dose of propofol was 19 (12.3–37.1) mg kg^?1. Awakening between boluses was very abrupt. In group CRI, propofol infusion rate was 0.85 (0.8–0.9) mg kg^?1 minute^?1, and anaesthesia was stable. Body temperature, heart and respiratory rates, oxygen saturation (by pulse oximeter) and reflexes did not differ between groups. Oxygen saturations (from pulse oximeter readings) were low in some birds. Following anaesthesia, all birds recovered within 40 minutes. In 55 % of all, transient signs of central nervous system excitement occurred during recovery.Conclusions and clinical relevance8 mg kg^?1 propofol appears an adequate induction dose for mute swans. For maintenance, a CRI of 0.85 mg kg^?1 minute^?1 produced stable anaesthesia suitable for painless clinical procedures. In contrast bolus administration, was unsatisfactory as birds awoke very suddenly, and the short intervals between bolus requirements hampered clinical procedures. Administration of additional oxygen throughout anaesthesia might reduce the incidence of low arterial haemoglobin saturation.     

Propofol and fentanyl infusions in dogs of various breeds undergoing surgery

ObjectiveTo report the cardiovascular variables, anaesthetic effects and recovery quality of an anaesthesia technique using variable rate infusion propofol combined with constant rate infusion fentanyl in dogs undergoing elective surgery.Study designProspective clinical trial.AnimalsA total of 27 dogs, aged 2.7 ± 2.65 years and weighing 24 ± 11 kg.MethodsFollowing intramuscular acepromazine (0.03 or 0.05 mg kg^?1) and subcutaneous carprofen (4 mg kg^?1) pre-medication, anaesthesia was induced with propofol (4.0 ± 0.5 mg kg^?1) intravenously (IV). All dogs were ventilated with 100% oxygen to maintain normocapnia. Propofol was infused at 0.4 mg kg^?1 minute^?1 for 20 minutes and then at 0.3 mg kg^?1minute^?1. If mean arterial blood pressure (MAP) decreased below 70 mmHg, propofol infusion was reduced by 0.1 mg kg^?1 minute^?1. Five minutes after induction of anaesthesia, fentanyl was administered (2 μg kg^?1) IV followed by the infusion at 0.5 μg kg^?1 minute^?1 and atropine (40 μg kg^?1) IV. Heart rate, MAP, respiratory rate, tidal volume, end-tidal carbon dioxide, presence of reflexes, movements and recovery times and quality were recorded.ResultsMean anaesthetic duration was 131 ± 38.5 minutes. Mean heart rate peaked 10 minutes after atropine injection and gradually declined, reaching pre-anaesthetic values at 55 minutes. MAP easily was maintained above 70 mmHg. Mean times to return of spontaneous ventilation, extubation, head lift and sternal recumbency were 21 ± 10.1, 33 ± 14.6, 43 ± 19.7 and 65 ± 23.4 minutes, respectively. Recovery was smooth and quiet. The time to sternal recumbency was significantly correlated with the duration of anaesthesia and total dose of propofol; time to extubation was correlated to total dose of propofol.Conclusion and clinical relevancePropofol and fentanyl infusions provided stable cardiovascular function and satisfactory conditions for surgery. Some modifications of infusion rates are required to improve the long-recovery times.     

Propofol–medetomidine–ketamine total intravenous anaesthesia in thiafentanil–medetomidine-immobilized impala (Aepyceros melampus)

Objective

To characterize a propofol–medetomidine-ketamine total intravenous anaesthetic in impala (Aepyceros melampus).