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.     

Continuous infusion of propofol or intermittent bolus of tiletamine‐zolazepam in squirrel monkeys (Saimiri sciureus)

ObjectiveTo investigate an infusion of propofol for anesthesia in comparison to tiletamine-zolazepam anesthesia, evaluating physiological variables and recovery in squirrel monkeys.Study designProspective non-blinded randomized study.AnimalsEight healthy squirrel monkeys (Saimiri sciureus), aged 3 years and weighing 0.340–0.695 kg.MethodsPremedication was intramuscular midazolam (0.5 mg) and meperidine (4 mg). Anesthesia was induced with intravenous (IV) propofol (4 mg kg^?1 minute^?1) and maintained with propofol starting at 0.4 mg kg^?1 minute^?1 (PRO, n = 4) or IV tiletamine-zolazepam (5 mg kg^?1) and maintained with supplementary doses of TZ (TZ, n = 4). Cardiopulmonary variables were measured continuously. Arterial blood gases and lactate concentration were measured at the end of anesthesia. Quality and times of recovery were determined. Repeatedly measured data for significant differences were tested between groups with t-test and within groups by anova.ResultsMedian time for induction of anesthesia in PRO was 180 seconds. Mean maintenance infusion rate of propofol was 0.43 ± 0.05 mg kg^?1 minute^?1, varying during the 1 hour period. One monkey died after administration of TZ; others required 1, 4, or 8 supplemental doses. Cardiopulmonary variables were similar between groups, but hypotension was recorded. Recovery times to ventral recumbency in PRO (32 ± 17 minutes) and TZ (84 ± 11 minutes) and normal ambulation in PRO (58 ± 22 minutes) and TZ (358 ± 109minutes) were significantly different (p < 0.05). Recovery quality was superior in PRO, with less ataxia and fewer unsuccessful attempts to stand. Lactate concentration was not different between treatments.Conclusions and clinical relevanceCardiopulmonary variables were similar between protocols, aside from the higher incidence of hypotension in PRO, indicating that further studies with a larger number of animals are required. Compared to tiletamine-zolazepam, propofol anesthesia provided faster and superior anesthetic recovery in these animals.     

Cardiovascular,respiratory, electrolyte and acid–base balance during continuous dexmedetomidine infusion in anesthetized dogs

ObjectiveTo evaluate the cardiovascular, respiratory, electrolyte and acid–base effects of a continuous infusion of dexmedetomidine during propofol–isoflurane anesthesia following premedication with dexmedetomidine.Study designProspective experimental study.AnimalsFive adult male Walker Hound dogs 1–2 years of age averaging 25.4 ± 3.6 kg.MethodsDogs were sedated with dexmedetomidine 10 μg kg^?1 IM, 78 ± 2.3 minutes (mean ± SD) before general anesthesia. Anesthesia was induced with propofol (2.5 ± 0.5 mg kg^?1) IV and maintained with 1.5% isoflurane. Thirty minutes later dexmedetomidine 0.5 μg kg^?1 IV was administered over 5 minutes followed by an infusion of 0.5 μg kg^?1 hour^?1. Cardiac output (CO), heart rate (HR), ECG, direct blood pressure, body temperature, respiratory parameters, acid–base and arterial blood gases and electrolytes were measured 30 and 60 minutes after the infusion started. Data were analyzed via multiple linear regression modeling of individual variables over time, compared to anesthetized baseline values. Data are presented as mean ± SD.ResultsNo statistical difference from baseline for any parameter was measured at any time point. Baseline CO, HR and mean arterial blood pressure (MAP) before infusion were 3.11 ± 0.9 L minute^?1, 78 ± 18 beats minute^?1 and 96 ± 10 mmHg, respectively. During infusion CO, HR and MAP were 3.20 ± 0.83 L minute^?1, 78 ± 14 beats minute^?1 and 89 ± 16 mmHg, respectively. No differences were found in respiratory rates, PaO₂, PaCO₂, pH, base excess, bicarbonate, sodium, potassium, chloride, calcium or lactate measurements before or during infusion.Conclusions and clinical relevanceDexmedetomidine infusion using a loading dose of 0.5 μg kg^?1 IV followed by a constant rate infusion of 0.5 μg kg^?1 hour^?1 does not cause any significant changes beyond those associated with an IM premedication dose of 10 μg kg^?1, in propofol–isoflurane anesthetized dogs. IM dexmedetomidine given 108 ± 2 minutes before onset of infusion showed typical significant effects on cardiovascular parameters.     

A comparison of cardiopulmonary function,recovery quality,and total dosages required for induction and total intravenous anesthesia with propofol versus a propofol‐ketamine combination in healthy Beagle dogs

ObjectiveTo compare cardiopulmonary function, recovery quality, and total dosages required for induction and 60 minutes of total intravenous anesthesia (TIVA) with propofol (P) or a 1:1 mg mL⁻¹ combination of propofol and ketamine (KP).Study designRandomized crossover study.AnimalsTen female Beagles weighing 9.4 ± 1.8 kg.MethodsDogs were randomized for administration of P or KP in a 1:1 mg mL⁻¹ ratio for induction and maintenance of TIVA. Baseline temperature, pulse, respiratory rate (f_R), noninvasive mean blood pressure (MAP), and hemoglobin oxygen saturation (SpO₂) were recorded. Dogs were intubated and spontaneously breathed room air. Heart rate (HR), f_R, MAP, SpO₂, end tidal carbon dioxide tension (Pe’CO₂), temperature, and salivation score were recorded every 5 minutes. Arterial blood gas analysis was performed at 10, 30, and 60 minutes, and after recovery. At 60 minutes the infusion was discontinued and total drug administered, time to extubation, and recovery score were recorded. The other treatment was performed 1 week later.ResultsKP required significantly less propofol for induction (4.0 ± 1.0 mg kg⁻¹ KP versus 5.3 ±1.1 mg kg⁻¹ P, p = 0.0285) and maintenance (0.3 ± 0.1 mg kg⁻¹ minute⁻¹ KP versus 0.6 ±0.1 mg kg⁻¹ minute⁻¹ P, p = 0.0018). Significantly higher HR occurred with KP. Both P and KP caused significantly lower MAP compared to baseline. MAP was significantly higher with KP at several time points. P had minimal effects on respiratory variables, while KP resulted in significant respiratory depression. There were no significant differences in salivation scores, time to extubation, or recovery scores.Conclusions and clinical relevanceTotal intravenous anesthesia in healthy dogs with ketamine and propofol in a 1:1 mg mL⁻¹ combination resulted in significant propofol dose reduction, higher HR, improved MAP, no difference in recovery quality, but more significant respiratory depression compared to propofol alone.     

Determining an optimum propofol infusion rate for induction of anaesthesia in healthy dogs: a randomized clinical trial

ObjectiveTo determine an optimum infusion rate of propofol that permitted rapid tracheal intubation while minimizing the duration of postinduction apnoea.Study designProspective, randomized, blinded clinical trial.AnimalsA total of 60 client-owned dogs presented for elective neutering and radiography.MethodsDogs were randomly allocated to one of five groups (groups A–E) to have propofol at an infusion rate of 0.5, 1, 2, 3, or 4 mg kg^–1 minute^–1, respectively, following intramuscular premedication with methadone 0.5 mg kg^–1 and dexmedetomidine 5 μg kg^–1. Propofol administration was stopped when adequate conditions for tracheal intubation were identified. Time to tracheal intubation and duration of apnoea were recorded. If oxygen haemoglobin saturation decreased to < 90%, manual ventilation was initiated. A one-way analysis of covariance was conducted to compare the effect of propofol infusion rate on duration of apnoea and intubation time whilst controlling for covariates, followed by post hoc tests. The significance level was set at p < 0.05.ResultsPropofol infusion rate had a significant effect on duration of apnoea (p = 0.004) and intubation time (p < 0.001) after controlling for bodyweight and sedation scores, respectively. The adjusted means (± standard error) of duration of apnoea were significantly shorter in groups A and B (49 ± 39 and 67 ± 37 seconds, respectively) than in groups C, D and E (207 ± 34, 192 ± 36 and 196 ± 34 seconds, respectively). Group B (115 ± 10 seconds) had a significantly shorter intubation time than group A (201 ± 10 seconds, p < 0.001).Conclusions and clinical relevanceAn infusion rate of 1.0 mg kg^–1 minute^–1 (group B) appears to offer the optimal compromise between speed of induction and duration of postinduction apnoea.     

A comparison of cardiopulmonary and anesthetic effects of an induction dose of alfaxalone or propofol in dogs

ObjectiveTo compare the physiological parameters, arterial blood gas values, induction quality, and recovery quality after IV injection of alfaxalone or propofol in dogs.Study designProspective, randomized, blinded crossover.AnimalsEight random-source adult female mixed-breed dogs weighing 18.7 ± 4.5 kg.MethodsDogs were assigned to receive up to 8 mg kg^?1 propofol or 4 mg kg^?1 alfaxalone, administered to effect, at 10% of the calculated dose every 10 seconds. They then received the alternate drug after a 6-day washout. Temperature, pulse rate, respiratory rate, direct blood pressure, and arterial blood gases were measured before induction, immediately post-induction, and at 5-minute intervals until extubation. Quality of induction, recovery, and ataxia were scored by a single blinded investigator. Duration of anesthesia and recovery, and adverse events were recorded.ResultsThe mean doses required for induction were 2.6 ± 0.4 mg kg^?1 alfaxalone and 5.2 ± 0.8 mg kg^?1 propofol. After alfaxalone, temperature, respiration, and pH were significantly lower, and PaCO₂ significantly higher post-induction compared to baseline (p < 0.03). After propofol, pH, PaO₂, and SaO₂ were significantly lower, and PaCO₂, HCO₃, and PA-aO₂ gradient significantly higher post-induction compared to baseline (p < 0.03). Post-induction and 5-minute physiologic and blood gas values were not significantly different between alfaxalone and propofol. Alfaxalone resulted in significantly longer times to achieve sternal recumbency (p = 0.0003) and standing (p = 0.0004) compared to propofol. Subjective scores for induction, recovery, and ataxia were not significantly different between treatments; however, dogs undergoing alfaxalone anesthesia were more likely to have ≥1 adverse event (p = 0.041). There were no serious adverse events in either treatment.Conclusions and clinical relevanceThere were no clinically significant differences in cardiopulmonary effects between propofol and alfaxalone. A single bolus of propofol resulted in shorter recovery times and fewer adverse events than a single bolus of alfaxalone.     

Hypnotic effects and pharmacokinetics of a single bolus dose of propofol in Japanese macaques (Macaca fuscata fuscata). [corrected

ObjectiveTo describe the hypnotic effects of a single bolus dose of propofol in Japanese macaques, and to develop a pharmacokinetic model.Study designProspective experimental trial.AnimalsFour male macaques (5-6 years old, 8.0-11.2 kg).MethodsThe macaque was restrained and 8 mg kg^?1 of propofol was administrated intravenously at 6 mg kg^?1 minute^?1. Behavioural changes without stimuli (first experiment) then responses to external stimuli (the second experiment) were assessed every 2 minutes for 20 minutes. Venous blood samples were collected before and at 1, 5, 15, 30, 60, 120 and 210 minutes after drug administration, and plasma concentrations of propofol were measured (third experiment). Pharmacokinetic modelling was performed using NONMEM VI.ResultsMacaques were recumbent without voluntary movement for a mean 14.0 ± 2.7 SD (range 10.5-16.2) or 10.0 ± 3.4 (7.2-14.5) minutes and recovered to behave as pre-administration by 25.1 ± 3.6 (22.1-30.1) or 22.2 ± 1.5 (21.1-24.3) minutes after the end of propofol administration without or with stimuli, respectively. Respiratory and heart rates were stable throughout the experiments (28-68 breaths minute^?1 and 72-144 beats minute^?1, respectively). Our final pharmacokinetic model included three compartments and well described the plasma concentration of propofol. The population pharmacokinetic parameters were: V₁ = 10.4 L, V₂=8.38 L, V₃=72.7 L, CL₁= 0.442 L minute^?1, CL₂= 1.14 L minute^?1, CL₃= 0.313 L minute^?1, (the volumes of distribution and the clearances for the central, rapid and slow peripheral compartments, respectively).ConclusionsIntravenous administration of propofol (8 mg kg^?1) at 6 mg kg^?1 minute^?1 to Japanese macaques had a hypnotic effect lasting more than 7 minutes. A three-compartment model described propofol plasma concentrations over more than 3 hours.Clinical relevanceThe developed pharmacokinetic parameters may enable simulations of administration protocols to maintain adequate plasma concentration of propofol.     

RESEARCH PAPER: Evaluation of cardiovascular,respiratory and biochemical effects,and anesthetic induction and recovery behavior in horses anesthetized with a 5% micellar microemulsion propofol formulation

ObjectiveTo characterize cardiovascular, respiratory and biochemical effects and recovery behavior associated with a 3‐hour continuous infusion of a micellar microemulsion propofol formulation in horses.Study designProspective experimental trial.AnimalsSix healthy adult horses, 9 ± 2 years old and weighing 557 ± 14 kg.MethodsAll horses received xylazine (1 mg kg^?1, IV) 5 minutes prior to anesthetic induction. Each horse was anesthetized on two occasions with a 5% micellar microemulsion propofol formulation (2 mg kg^?1, IV); first as a single bolus (phase I) and then as a 3‐hour continuous infusion (phase II). Propofol pharmacokinetics were obtained from phase I and used to determine the starting infusion rates in phase II. Anesthetic induction and recovery characteristics were quantitatively and qualitatively assessed. Cardiovascular, respiratory and biochemical parameters were monitored during anesthesia and recovery.ResultsInduction quality varied, ranging from good to poor. Standing and overall recovery quality scores were consistently excellent in phase I but more variability was observed among horses in phase II. Heart rate (HR) and mean arterial pressure (MAP) were adequately maintained but marked hypoventilation developed. There were only minimal changes in blood biochemical analytes following anesthesia.Conclusions and clinical relevanceThe micellar microemulsion propofol formulation, administered as a 3‐hour continuous infusion, showed similar results compared to those previously described with a commercially available propofol preparation. However, based on present findings, use of propofol as a primary anesthetic in horses for prolonged periods of anesthesia requires further study to determine the limits of safety and clinical applicability.     

Total intravenous anesthesia in domestic chicken (Gallus gallus domesticus) with propofol alone or in combination with methadone,nalbuphine or fentanyl for ulna osteotomy

ObjectiveTo compare the propofol infusion rate and cardiopulmonary effects during total intravenous anesthesia with propofol alone and propofol combined with methadone, fentanyl or nalbuphine in domestic chickens undergoing ulna osteotomy.Study designProspective, randomized, experiment trial.AnimalsA total of 59 healthy Hissex Brown chickens weighing 1.5 ± 0.2 kg.MethodsAnesthesia was induced with propofol (9 mg kg^–1) administered intravenously (IV) and maintained with propofol (1.2 mg kg^–1 minute^–1) for 30 minutes. Birds were intubated and supplemented with 100% oxygen through a nonrebreathing circuit under spontaneous ventilation. Thereafter, each animal was randomly assigned to one of four groups: group P, no treatment; group PM, methadone (6 mg kg^–1) intramuscularly (IM); group PN, nalbuphine IM (12.5 mg kg^–1); and group PF, fentanyl IV (30 μg kg^–1 loading dose, 30 μg kg^–1 hour^–1 constant rate infusion). During the osteotomy surgery, the propofol infusion rate was adjusted to avoid movement of birds and provide adequate anesthesia. Pulse rate, invasive blood pressure, respiratory frequency, end-tidal carbon dioxide partial pressure (Pe′CO₂) and hemoglobin oxygen saturation (SpO₂) were recorded.ResultsData were available from 58 chickens. The mean ± standard deviation propofol infusion rate (mg kg^–1 minute^–1) for the duration of anesthesia was: group P, 0.81 ± 0.15; group PM, 0.66 ± 0.11; group PN, 0.60 ± 0.14; and group PF, 0.80 ± 0.07. Significant differences were P versus PM (p = 0.042), P versus PN (p = 0.002) and PF versus PN (p = 0.004). Pulse rate, blood pressure and SpO₂ remained acceptable for anesthetized birds with minor differences among groups. Values of Pe′CO₂ >60 mmHg (8 kPa) were observed in all groups.Conclusions and clinical relevanceMethadone and nalbuphine, but not fentanyl, decreased the propofol infusion rate required for anesthesia maintenance, but resulted in no obvious benefit in physiological variables.     

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.     

Cardiopulmonary and isoflurane‐sparing effects of epidural or intravenous infusion of dexmedetomidine in cats undergoing surgery with epidural lidocaine

ObjectiveTo compare the cardiorespiratory, anesthetic-sparing effects and quality of anesthetic recovery after epidural and constant rate intravenous (IV) infusion of dexmedetomidine (DEX) in cats given a low dose of epidural lidocaine under propofol-isoflurane anesthesia and submitted to elective ovariohysterectomy.Study designRandomized, blinded clinical trial.AnimalsTwenty-one adult female cats (mean body weight: 3.1 ± 0.4 kg).MethodsCats received DEX (4 μg kg^?1, IM). Fifteen minutes later, anesthesia was induced with propofol and maintained with isoflurane. Cats were divided into three groups. In GI cats received epidural lidocaine (1 mg kg^?1, n = 7), in GII cats were given epidural lidocaine (1 mg kg^?1) + DEX (4 μg kg^?1, n = 7), and in GIII cats were given epidural lidocaine (1 mg kg^?1) + IV constant rate infusion (CRI) of DEX (0.25 μg kg^?1 minute^?1, n = 7). Variables evaluated included heart rate (HR), respiratory rate (f_R), systemic arterial pressures, rectal temperature (RT), end-tidal CO₂, end-tidal isoflurane concentration (e′ISO), arterial blood gases, and muscle tone. Anesthetic recovery was compared among groups by evaluation of times to recovery, HR, f_R, RT, and degree of analgesia. A paired t-test was used to evaluate pre-medication variables and blood gases within groups. anova was used to compare parametric data, whereas Friedman test was used to compare muscle relaxation.ResultsEpidural and CRI of DEX reduced HR during anesthesia maintenance. Mean ± SD e′ISO ranged from 0.86 ± 0.28% to 1.91 ± 0.63% in GI, from 0.70 ± 0.12% to 0.97 ± 0.20% in GII, and from 0.69 ± 0.12% to 1.17 ± 0.25% in GIII. Cats in GII and GIII had longer recovery periods than in GI.Conclusions and clinical relevanceEpidural and CRI of DEX significantly decreased isoflurane consumption and resulted in recovery of better quality and longer duration, despite bradycardia, without changes in systemic blood pressure.     

Effect of alfaxalone infusion on the electroencephalogram of dogs anaesthetized with halothane

ObjectiveTo describe the effects of alfaxalone on the canine electroencephalogram (EEG).Study designExperimental study.AnimalsEight healthy adult Huntaway dogs.MethodsAnaesthesia was induced with propofol and maintained with halothane (0.85-0.95 end-tidal volume %) in oxygen. Animals were ventilated to maintain stable end-tidal CO₂ and halothane concentrations. Following a 30 minute stabilisation period, alfaxalone (0.5 mg kg^?1) was infused intravenously over a 5 minute period. The electroencephalogram was recorded from the beginning of the stabilisation period until 60 minutes following the start of alfaxalone treatment. Data were subjected to fast Fourier transformation, and median frequency, 95% spectral edge frequency and total EEG power were calculated. Two-factorial repeated measures anova (time and EEG channels were factors) was used for statistical analysis (p<0.05).ResultsA shift in the dominant frequency band from beta to delta after alfaxalone treatment and occasional burst suppression were observed. Median frequency decreased significantly below baseline (9.2 ± 1.4 Hz) (mean ± SD) during alfaxalone infusion. The lowest value (4.8 ± 1.2 Hz) was recorded 5 minutes after the start of infusion. Spectral edge frequency also decreased below baseline (26.2 ± 1.5 Hz) and the lowest value (22.6 ± 1.5 Hz) also was detected at 5 minutes after the start of infusion. Total EEG power did not change significantly. In some frequencies EEG power increased soon after the start of alfaxalone infusion, then decreased below baseline later (biphasic pattern).Conclusions and clinical relevanceAlfaxalone induced biphasic changes on EEG and decreased F₅₀ and F₉₅ in halothane anaesthetized dogs.     

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.     

Bispectral index in dogs at three intravenous infusion rates of propofol

ObjectiveTo establish the correlation between the bispectral index (BIS) and different rates of infusion of propofol in dogs.Study designProspective experimental trial.AnimalsEight adult dogs weighing 6–20 kg.MethodsEight animals underwent three treatments at intervals of 20 days. Propofol was used for induction of anesthesia (10 mg kg⁻¹ IV), followed by a continuous rate infusion (CRI) at 0.2 mg kg⁻¹ minute⁻¹ (P2), 0.4 mg kg⁻¹ minute⁻¹ (P4) or 0.8 mg kg⁻¹ minute⁻¹ (P8) for 55 minutes. The BIS values were measured at 10, 20, 30, 40, and 50 minutes (T10, T20, T30, T40, and T50, respectively) after the CRI of propofol was started. Numeric data were submitted to analysis of variance followed by Tukey test (p < 0.05).ResultsThe BIS differed significantly among groups at T40, when P8 was lower than P2 and P4. At T50, P8 was lower than P2. The electromyographic activity (EMG) in P2 and P4 was higher than P8 at T40 and T50.ConclusionsAn increase in propofol infusion rates decreases the BIS values and EMG.     

A clinical trial of propofol infusion anaesthesia in dogs

Studies were carried out on 40 dogs premedicated with acepromazine (0·05 mg. kg^-1) and atropine (0·02 mg. kg^-1) to determine the minimum infusion rate of propofol needed to maintain anaesthesia and to compare the quality of the anaesthesia with that produced by halothane/nitrous oxide/oxygen. In 30 dogs anaesthesia was induced with propofol and maintained with a continuous infusion and in the other ten dogs anaesthesia was induced with thiopentone and maintained with the inhalation agents. An infusion rate of 0·4 mg. kg^-1 min^-1 of propofol produced surgical anaesthesia in dogs breathing oxygen or oxygen-enriched air. Cardiovascular and respiratory effects were similar to those in dogs anaesthetized with halothane/nitrous oxide and with both anaesthetic regimens myocardial oxygen consumption appeared to increase with increasing duration of anaesthesia. A possible familial susceptibility resulting in a more prolonged recovery was revealed and propofol infusion was associated with a 16 per cent incidence of vomiting in the recovery period. It was concluded that in canine anaesthesia the continuous infusion of propofol to maintain anaesthesia in healthy dogs was safe but less satisfactory than the use of halothane/nitrous oxide.     

Comparison of alfaxalone and propofol administered as total intravenous anaesthesia for ovariohysterectomy in dogs

ObjectiveTo compare the anaesthetic and cardiopulmonary effects of alfaxalone with propofol when used for total intravenous anaesthesia (TIVA) during ovariohysterectomy in dogs.Study designA prospective non-blinded randomized clinical study.AnimalsFourteen healthy female crossbred bitches, aged 0.5–5 years and weight 16–42 kg.MethodsDogs were premedicated with acepromazine 0.01 mg kg^?1 and morphine 0.4 mg kg^?1. Anaesthesia was induced and maintained with either propofol or alfaxalone to effect for tracheal intubation followed by an infusion of the same agent. Dogs breathed spontaneously via a ‘circle’ circuit, with oxygen supplementation. Cardiopulmonary parameters (respiratory and heart rates, end-tidal carbon dioxide, tidal volume, and invasive blood pressures) were measured continuously and recorded at intervals related to the surgical procedure. Arterial blood samples were analysed for blood gas values. Quality of induction and recovery, and recovery times were determined. Non-parametric data were tested for significant differences between groups using the Mann–Whitney U-test and repeatedly measured data (normally distributed) for significant differences between and within groups by anova.ResultsBoth propofol and alphaxalone injection and subsequent infusions resulted in smooth, rapid induction and satisfactory maintenance of anaesthesia. Doses for induction (mean ± SD) were 5.8 ± 0.30 and 1.9 ± 0.07 mg kg^?1 and for the CRIs, 0.37 ± 0.09 and 0.11 ± 0.01 mg kg^?1 per minute for propofol and alfaxalone respectively. Median (IQR) recovery times were to sternal 45 (33–69) and 60 (46–61) and to standing 74 (69–76) and 90 (85–107) for propofol and alphaxalone respectively. Recovery quality was good. Cardiopulmonary effects did not differ between groups. Hypoventilation occurred in both groups.Conclusions and clinical relevanceFollowing premedication with acepromazine and morphine, both propofol and alphaxalone produce good quality anaesthesia adequate for ovariohysterectomy. Hypoventilation occurs suggesting a need for ventilatory support during prolonged infusion periods with either anaesthetic agent.     

Anaesthetic and cardiorespiratory effects of a constant rate infusion of fentanyl in isoflurane‐anaesthetized sheep

ObjectiveTo determine the anaesthetic and cardiorespiratory effects of a constant rate infusion of fentanyl in sheep anaesthetized with isoflurane and undergoing orthopaedic surgery.Study designProspective, randomised, ‘blinded’ controlled study.AnimalsTwenty healthy sheep (weight mean 41.1 ± SD 4.5 kg).MethodsSheep were sedated with intravenous (IV) dexmedetomidine (4 μg kg⁻¹) and morphine (0.2 mg kg⁻¹). Anaesthesia was induced with propofol (1 mg kg⁻¹ minute⁻¹ to effect IV) and maintained with isoflurane in oxygen and a continuous rate infusion (CRI) of fentanyl 10 μg kg⁻¹ hour⁻¹ (group F) or saline (group P) for 100 minutes. The anaesthetic induction dose of propofol, isoflurane expiratory fraction (Fe’iso) required for maintenance and cardiorespiratory measurements were recorded and blood gases analyzed at predetermined intervals. The quality of recovery was assessed. Results were compared between groups using t-tests or Mann–Whitney as relevant.ResultsThe propofol induction dose was 4.7 ± 2.4 mg kg⁻¹. Fe’iso was significantly lower (by 22.6%) in group F sheep than group P (p = 0). Cardiac index (mean ± SD mL kg⁻¹ minute⁻¹) was significantly (p = 0.012) lower in group F (90 ± 15) than group P (102 ± 35). Other measured cardiorespiratory parameters did not differ statistically significantly between groups. Recovery times and recovery quality were statistically similar in both groups.Conclusions and clinical relevanceFentanyl reduced isoflurane requirements without clinically affecting the cardiorespiratory stability or post-operative recovery in anaesthetized sheep undergoing orthopaedic surgery.     

Continuous infusion of propofol in dogs premedicated with methotrimeprazine

Objective To evaluate the cardiopulmonary and clinical effects of three different infusion rates of propofol in dogs premedicated with methotrimeprazine. Study design Randomized experimental trial. Animals Ten healthy adult mixed‐breed male and female dogs, weighing from 14 to 20 kg. Methods Dogs were premedicated with methotrimeprazine [1 mg kg^?1 intravenously (IV)] followed by induction of anesthesia with 4.5 mg kg^?1 of propofol IV and maintenance with propofol for 60 minutes as follows: T1, 0.2 mg kg^?1 minute^?1; T2, 0.3 mg kg^?1minute^?1; and T3, 0.4 mg kg^?1minute^?1. Heart rate (HR), respiratory rate (RR), mean arterial pressure (MAP), end‐tidal CO₂ (P_ETCO₂), arterial hemoglobin O₂ saturation, arterial blood gases, and pedal and cutaneous reflexes were measured before and 5, 10, 20, 30, 45 and 60 minutes after the beginning of the propofol infusion. Statistical analysis was performed using an anova . Results Heart rate increased during anesthesia in all cases and arterial blood pressure decreased only in dogs in the T3 category. Respiratory depression was proportional to the infusion rate of propofol. Muscle relaxation was satisfactory, but analgesia was inadequate in the three treatments. Conclusions The infusion of 0.2–0.4 mg kg^?1 minute^?1 of propofol produced a dose‐dependent respiratory depression. The presence of a pedal withdrawal reflex and marked cardiovascular responses to this noxious stimulus suggests that anesthesia may not be of sufficient depth for surgery to be carried out. Clinical relevance Although several studies have been performed using propofol in animals, few studies have investigated the cardiopulmonary and analgesic effects with different doses. The determination of an adequate propofol infusion rate is necessary for the routine use of this intravenous anesthetic for the maintenance of anesthesia during major surgical procedures in dogs.     

Total intravenous anesthesia with ketamine–medetomidine–propofol in horses

Propofol is a potentially useful intravenous anesthetic agent for total intravenous anesthesia (TIVA) in horses. The purpose of this study was to compare the anesthetic and cardiorespiratory effects of TIVA following the administration of propofol alone(P–TIVA) and ketamine–medetomidine–propofol (KM–P–TIVA) in adult horses. The carotid artery was translocated to a subcutaneous position during TIVA with P–TIVA (n = 6) or KM–P–TIVA (n = 6). All horses were premedicated with medetomidine [0.005 mg kg^–1, intravenously (IV)]. Anesthesia was induced with midazolam (0.04 mg kg^–1 IV) and ketamine (2.5 mg kg IV). All horses were orotracheally intubated and breathed 100% oxygen. The KM drug combination (ketamine 40 mg mL^–1 and medetomidine 0.05 mg mL^–1) was infused at a rate of 0.025 mL kg^–1 hour^–1. Subsequently, a loading dose of propofol (0.5 mg kg^–1, bolus IV) was administered to all horses; surgical anesthesia (determined by horse response to incision and surgical manipulation, positive response being purposeful or spontaneous movement of limbs or head) was maintained by varying the propofol infusion rate as needed. Arterial blood pressure and HR were also monitored. Both methods of producing TIVA provided excellent general anesthesia for the surgical procedure. Anesthesia time was 115 ± 17 (mean ± SD) and 112 ± 11 minutes in horses anesthetized with KM–P–TIVA and P–TIVA, respectively. The infusion rate of propofol required to maintain surgical anesthesia with KM–P–TIVA was significantly less than for P–TIVA (mean infusion rate of propofol during anesthesia; KM–P–TIVA 0.15 0.02 P–TIVA 0.23 ± 0.03 mg kg^–1 minute^–1, p = 0.004). Apnea occurred in all horses lasting 1–2 minutes and intermittent positive pressure ventilation was started. Cardiovascular function was maintained during both methods of producing TIVA. There were no differences in the time to standing after the cessation of anesthesia (KM–P–TIVA 62 ± 10 minutes versus P–TIVA 87 ± 36 minutes, p = 0.150). The quality of recovery was good in KM–P–TIVA and satisfactory in P–TIVA. KM–P–TIVA and P–TIVA produced clinically useful general anesthesia with minimum cardiovascular depression. Positive pressure ventilation was required to treat respiratory depression. Respiratory depression and apnea must be considered prior to the use of propofol in the horse.