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.     

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.     

Hemodynamic effects of target-controlled infusion of propofol alone or in combination with a constant-rate infusion of remifentanil in dogs

The objective of this study was to evaluate the hemodynamic effects of target-controlled infusion (TCI) of propofol alone or in combination with a constant-rate infusion (CRI) of remifentanil. Six adult dogs were given 2 treatments in a randomized crossover study with a 7-day interval between treatments. Treatment 1 was propofol (P) and treatment 2 was propofol and remifentanil (P-Rem), without any premedication. Propofol was induced using a TCI system with a predicted plasma concentration (Cp) of 6.0 μg/mL. Anesthesia was maintained within the Cp range (0.65 to 3.0 μg/mL) for 120 min and remifentanil was administered at a rate of 0.3 μg/kg body weight (BW) per minute, CRI. Cardiopulmonary variables were recorded before (baseline), during, and 120 min after drug administration. Heart rate (HR) decreased significantly in the P-Rem group (46%) compared with baseline values. In the P-Rem group, the cardiac index (CI) decreased significantly (49% to 58%) and the stroke volume (SV) decreased compared with baseline values. The systemic vascular resistance index (SVRI) increased significantly in the P-Rem group compared with baseline values. There was no difference in mean arterial pressure (MAP) between the groups. Central venous pressure (CVP) and pulmonary artery occlusion pressure (PAOP) significantly increased in the P-Rem group compared with baseline values. In conclusion, the hemodynamic changes observed in this study indicate a compromise of the cardiovascular system, although the dogs in this study were healthy/euvolemic and there was no change in preload. More studies are required in order to evaluate the actual safety of the combination of propofol and remifentanil in patients with reduced cardiac reserve.     

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.     

Dexmedetomidine constant rate infusion for 24 hours during and after propofol or isoflurane anaesthesia in dogs

OBJECTIVE: To evaluate cardiovascular and respiratory effects and pharmacokinetics of a 24-hour intravenous constant rate infusion (CRI) of dexmedetomidine (DMED) during and after propofol (PRO) or isoflurane (ISO) anaesthesia in dogs. STUDY DESIGN: Prospective, randomized, cross-over study. ANIMALS: Ten healthy adult Beagles. METHODS: Instrumented dogs received a DMED-loading bolus (25 microg m(-2)) at time 0 followed by a 24-hour CRI (25 microg m(-2) hour(-1)), with PRO or ISO induction/maintenance of anaesthesia during the first 2 hours (PRO and ISO treatment groups, respectively). Cardiovascular, respiratory, blood gas, airway gas, serum chemistry variables and DMED plasma concentration data were collected at -15, 5, 15, 30, 45, 60, 90 and 120 minutes. A number of cardiorespiratory and tissue oxygenation variables were calculated from the above data. After the 2-hours of anaesthesia, heart and respiratory rates and electrocardiograms were recorded and DMED plasma concentrations were determined for up to 26 hours. RESULTS: Vasopressor effects and the decrease in heart rate (HR) and cardiac index induced by DMED were greater for PRO than ISO, but were within clinically acceptable ranges. Adequate oxygenation was maintained above the critical O(2) delivery level. The overall incidence of unfavourable arrhythmias was low and tended to vary inversely with HR. Mean DMED plasma concentration ranged from 0.23 to 0.47 ng mL(-1) for both groups during the 24-hour CRI with a mean elimination half-life of approximately 0.46 hour. CONCLUSION AND/CLINICAL RELEVANCE: DMED CRI resulted in typical alpha(2)-agonist induced haemodynamic changes with minimal respiratory effects, and appeared to be an efficacious adjunct during and after PRO or ISO anaesthesia in healthy dogs.     

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.     

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.     

Effects of medetomidine premedication on propofol infusion anaesthesia in dogs

Observations of cardiovascular and respiratory parameters were made on six dogs anaesthetized on two separate occasions for 120 minutes with a propofol infusion, once without premedication and once following premedication with 10 μg kg-¹ of intramuscular medetomidine. During anaesthesia the heart rate and cardiac index tended to be lower following medetomidine premedication, while the mean arterial pressure was significantly greater (p<0.05). Although the differences were not statistically significant, the systemic vascular resistance, pulmonary vascular resistance and stroke volume index were also greater in dogs given medetomidine. The mean arterial oxygen and carbon dioxide tensions were similar under both regimens, but in 2 dogs supplementary oxygen had to be administered during anaesthesia to alleviate severe hypoxaemia on both occasions they were anaesthetized. Minute and tidal volumes of respiration tended to be greater in dogs not given medetomidine but medetomidine premedication appeared to have no effect on venous admixture. Dogs given medetomidine received intramuscular atipamezole at the end of the 120 min. propofol infusion; the mean time from induction of anaesthesia to walking without ataxia was 174. min in the unpremedicated dogs and 160 min. in the dogs given atipamezole. The mean blood propofol concentration at which the dogs walked without ataxia was higher in the unpremedicated animals (2.12 ± 0.077 μg. ml-¹ compared with 1.27 ± 0.518 μg. ml-¹ in the premedicated dogs). The oxygen delivery to the tissues was lower after medetomidine premedication (p = 0.03) and the oxygen consumption was generally lower after medetomidine premedication but the difference did not achieve statistical significance. No correlation could be demonstrated between blood propofol concentration and cardiac index, systemic or pulmonary vascular resistance indices, systolic, diastolic or mean arterial blood pressures.     

A comparison of propofol infusion and propofol/isoflurane anaesthesia in dexmedetomidine premedicated dogs

The effects of propofol infusion were compared with propofol/isoflurane anaesthesia in six beagles premedicated with 10 microg/kg intramuscular (i.m.) dexmedetomidine. The suitability of a cold pressor test (CPT) as a stress stimulus in dogs was also studied. Each dog received isoflurane (end tidal 1.0%, induction with propofol) with and without CPT; propofol (200 microg/kg/min, induction with propofol) with and without CPT; premedication alone with and without CPT in a randomized block study in six separate sessions. Heart rate and arterial blood pressures and gases were monitored. Plasma catecholamine, beta-endorphin and cortisol concentrations were measured. Recovery profile was observed. Blood pressures stayed within normal reference range but the dogs were bradycardic (mean heart rate < 70 bpm). PaCO2 concentration during anaesthesia was higher in the propofol group (mean > 57 mmHg) when compared with isoflurane (mean < 52 mmHg). Recovery times were longer with propofol than when compared with the other treatments. The mean extubation times were 8 +/- 3.4 and 23 +/- 6.3 min after propofol/isoflurane and propofol anaesthesia, respectively. The endocrine stress response was similar in all treatments except for lower adrenaline level after propofol infusion at the end of the recovery period. Cold pressor test produced variable responses and was not a reliable stress stimulus in the present study. Propofol/isoflurane anaesthesia was considered more useful than propofol infusion because of milder degree of respiratory depression and faster recovery.     

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.     

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.     

Comparative study of propofol or propofol and ketamine for the induction of anaesthesia in dogs

The effects of propofol alone or propofol and ketamine for the induction of anaesthesia in dogs were compared. Thirty healthy dogs were premedicated with acepromazine and pethidine, then randomly allocated to either treatment. Anaesthesia was induced with propofol (4 mg/kg bodyweight intravenously) (group 1), or propofol and ketamine (2 mg/kg bodyweight of each intravenously) (group 2). Anaesthesia was maintained with halothane, delivered in a mixture of oxygen and nitrous oxide (1:2) via a non-rebreathing Bain circuit. Various cardiorespiratory parameters were monitored at two, five, 10, 15, 20, 25 and 30 minutes after induction, and the animals were observed during anaesthesia and recovery, and any adverse effects were recorded. During anaesthesia, the heart rate, but not the systolic arterial pressure, was consistently higher in group 2 (range 95 to 102 beats per minute) than in group 1 (range 73 to 90 beats per minute). Post-induction apnoea was more common in group 2 (11 of 15) than in group 1 (six of 15). Muscle twitching was observed in three dogs in each group. Recovery times were similar in both groups. Propofol followed by ketamine was comparable with propofol alone for the induction of anaesthesia in healthy dogs.     

Use of a combination of propofol and fentanyl, alfentanil, or sufentanil for total intravenous anesthesia in cats

OBJECTIVE: To determine the cardiorespiratory effects of an i.v. infusion of propofol alone or in association with fentanyl, alfentanil, or sufentanil in cats and, for each combination, the minimal infusion rate of propofol that would inhibit a response to noxious stimuli. DESIGN: Randomized crossover study. ANIMALS: 6 cats. PROCEDURE: Cats were anesthetized 4 times in random order. After i.v. administration of fentanyl, alfentanil, sufentanil, or saline (0.9% NaCl) solution, anesthesia was induced with propofol (7 mg/kg 13.2 mg/lb], i.v.) and maintained for 90 minutes with a continuous infusion of propofol in conjunction with fentanyl (0.1 microg/kg/min [0.045 microg/lb/min]), alfentanil (0.5 microg/kg/min [0.23 microg/lb/min]), sufentanil (0.01 microg/kg/min [0.004 microg/lb/min]), or saline solution (0.08 mL/kg/min [0.036 mL/lb/min]). RESULTS: Minimal infusion rate of propofol required to prevent a response to a noxious stimulus was higher when cats received saline solution. After 70 minutes, minimal infusion rate of propofol was significantly higher with fentanyl than with sufentanil. Decreases in heart rate, systolic blood pressure, rectal temperature, and respiratory rate were detected with all treatments. Oxygen saturation did not change significantly, but end-tidal partial pressure of carbon dioxide increased with all treatments. There were no significant differences in recovery times or sedation and recovery scores among treatments. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that infusion of propofol in combination with fentanyl, alfentanil, or sufentanil results in satisfactory anesthesia in cats.     

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.     

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.     

A step towards effect-site target-controlled infusion with propofol in dogs: a ke0 for propofol

Target-controlled infusion (TCI) anesthesia using target effect-site concentration rather than plasma concentration provides less drug consumption, safer anesthesia, less undesired side effects and improved animal welfare. The aim of this study was to calculate the constant that converts propofol plasma into effect-site concentration ( k _e0) in dogs, and to implement it in a TCI system and compare it with the effect on the central nervous system (CNS). All dogs were subjected to general anesthesia using propofol. Fourteen dogs were used as the pilot group to calculate k _e0, using the t _peak method. Fourteen dogs were used as the test group to test and validate the model. R ugloop ii ^® software was used to drive the propofol syringe pump and to collect data from S/5 Datex monitor and cerebral state monitor. The calculated k _e0 was incorporated in an existing pharmacokinetic model (Beths Model). The relationship between propofol effect site concentrations and anesthetic planes, and propofol plasma and effect-site concentrations was compared using Pearson's correlation analysis. Average t _peak was 3.1 min resulting in a k _e0 of 0.7230 min⁻¹. The test group showed a positive correlation between anesthetic planes and propofol effect-site concentration ( R  = 0.69; P <  0.0001). This study proposes a k _e0 for propofol with results that demonstrated a good adequacy for the pharmacokinetic model and the measured effect. The use of this k _e0 will allow an easier propofol titration according to the anesthetic depth, which may lead to a reduction in propofol consumption and less undesired side effects usually associated to high propofol concentrations in dogs.