Propofol anaesthesia for surgery in late gestation pony mares

Objective To characterize propofol anaesthesia in pregnant ponies. Animals Fourteen pony mares, at 256 ± 49 days gestation, undergoing abdominal surgery to implant fetal and maternal vascular catheters. Materials and methods Pre‐anaesthetic medication with intravenous (IV) acepromazine (20 µg kg^?1), butorphanol (20 µg kg^?1) and detomidine (10 µg kg^?1) was given 30 minutes before induction of anaesthesia with detomidine (10 µg kg^?1) and ketamine (2 mg kg^?1) IV Maternal arterial blood pressure was recorded (facial artery) throughout anaesthesia. Arterial blood gas values and plasma concentrations of glucose, lactate, cortisol and propofol were measured at 20‐minute intervals. Anaesthesia was maintained with propofol infused initially at 200 µg kg^?1 minute^?1, and at 130–180 µg kg^?1 minute^?1 after 60 minutes, ventilation was controlled with oxygen and nitrous oxide to maintain PaCO₂ between 5.0 and 6.0 kPa (37.6 and 45.1 mm Hg) and PaO₂ between 13.3 and 20.0 kPa (100 and 150.4 mm Hg). During anaesthesia flunixin (1 mg kg^?1), procaine penicillin (6 IU) and butorphanol 80 µg kg^?1 were given. Lactated Ringer's solution was infused at 10 mL kg^?1 hour^?1. Simultaneous fetal and maternal blood samples were withdrawn at 85–95 minutes. Recovery from anaesthesia was assisted. Results Arterial blood gas values remained within intended limits. Plasma propofol levels stabilized after 20 minutes (range 3.5–9.1 µg kg^?1); disposition estimates were clearance 6.13 ± 1.51 L minute^?1 (mean ± SD) and volume of distribution 117.1 ± 38.9 L (mean ± SD). Plasma cortisol increased from 193 ± 43 nmol L^?1 before anaesthesia to 421 ± 96 nmol L^?1 60 minutes after anaesthesia. Surgical conditions were excellent. Fetal umbilical venous pH, PO₂ and PCO₂ were 7.35 ± 0.04, 6.5 ± 0.5 kPa (49 ± 4 mm Hg) and 6.9 ± 0.5 kPa (52 ± 4 mm Hg); fetal arterial pH, PO₂ and PCO₂ were 7.29 ± 0.06, 3.3 ± 0.8 kPa (25 ± 6 mm Hg) and 8.7 ± 0.9 kPa (65 ± 7 mm Hg), respectively. Recovery to standing occurred at 46 ± 17 minutes, and was generally smooth. Ponies regained normal behaviour patterns immediately. Conclusions and clinical relevance Propofol anaesthesia was smooth with satisfactory cardiovascular function in both mare and fetus; we believe this to be a suitable anaesthetic technique for pregnant ponies.     

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.     

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).

Intravenous anaesthesia using detomidine, ketamine and guaiphenesin for laparotomy in pregnant pony mares

Objective To characterize intravenous anaesthesia with detomidine, ketamine and guaiphenesin in pregnant ponies. Animals Twelve pony mares, at 260–320 days gestation undergoing abdominal surgery to implant fetal and maternal vascular catheters. Materials and methods Pre‐anaesthetic medication with intravenous (IV) acepromazine (30 µg kg^?1), butorphanol (20 µg kg^?1) and detomidine (10 µg kg^?1) preceded induction of anaesthesia with detomidine (10 µg kg^?1) and ketamine (2 mg kg^?1) IV Maternal arterial blood pressure was measured directly throughout anaesthesia and arterial blood samples were taken at 20‐minute intervals for measurement of blood gases and plasma concentrations of cortisol, glucose and lactate. Anaesthesia was maintained with an IV infusion of detomidine (0.04 mg mL^?1), ketamine (4 mg mL^?1) and guaiphenesin (100 mg mL^?1) (DKG) for 140 minutes. Oxygen was supplied by intermittent positive pressure ventilation (IPPV) adjusted to maintain PaCO₂ between 5.0 and 6.0 kPa (38 and 45 mm Hg), while PaO₂ was kept close to 20.0 kPa (150 mm Hg) by adding nitrous oxide. Simultaneous fetal and maternal blood samples were withdrawn at 90 minutes. Recovery quality was assessed. Results DKG was infused at 0.67 ± 0.17 mL kg^?1 hour^?1 for 1 hour then reduced, reaching 0.28 ± 0.14 mL kg^?1 hour^?1 at 140 minutes. Arterial blood gas values and pH remained within intended limits. During anaesthesia there was no change in heart rate, but arterial blood pressure decreased by 10%. Plasma glucose and lactate increased (10‐fold and 2‐fold, respectively) and cortisol decreased by 50% during anaesthesia. Fetal umbilical venous pH, PO₂ and PCO₂ were 7.34 ± 0.06, 5.8 ± 0.9 kPa (44 ± 7 mm Hg) and 6.7 ± 0.8 kPa (50 ± 6 mm Hg); and fetal arterial pH, PO₂ and PCO₂ were 7.29 ± 0.06, 4.0 ± 0.7 kPa (30 ± 5 mm Hg) and 7.8 ± 1.7 kPa (59 ± 13 mm Hg), respectively. Surgical conditions were good but four ponies required a single additional dose of ketamine. Ponies took 60 ± 28 minutes to stand and recovery was good. Conclusions and clinical relevance Anaesthesia produced with DKG was smooth while cardiovascular function in mare and fetus was well preserved. This indicates that DKG infusion is suitable for maintenance of anaesthesia in pregnant equidae.     

Cardiovascular effects of propofol alone and in combination with ketamine for total intravenous anesthesia in healthy cats

This study was designed to compare the cardiovascular effects of equipotent maintenance of anesthetic doses (determined in a previous study) of propofol and propofol/ketamine, administered with and without noxious stimulation. Six healthy adult cats were anesthetized with propofol (loading dose 6.6 mg kg^?1, infusion 0.22 mg kg^?1 minute^?1), and instrumented to allow determination of blood gas and acid–base balance and measurement of blood pressures and cardiac output. The propofol infusion was continued for a further 60 minutes after which measurements were taken prior to and during application of a noxious stimulus. The propofol infusion was decreased to 0.14 mg kg^?1 minute^?1, and ketamine (loading dose 2 mg kg^?1, infusion 23 µg kg minute^?1) was administered. After a further 60 minutes, measurements were again taken prior to and during application of a noxious stimulus. The data were analyzed, using several Repeated Measures anova (first, ketamine/propofol and noxious stimulation were each treated as within‐subject factors; secondly, the levels of these two factors were combined into a single within‐subject factor). Mean arterial pressure, CVP, PAOP, SI, CI, SVRI, PVRI, oxygen delivery index, oxygen consumption index, oxygen utilization ratio, PvO₂, pHa, PaCO₂, bicarbonate concentration, and BD values collected during propofol administration were not changed by addition of ketamine and reduction of propofol concentration or by application of a noxious stimulus under propofol alone. Application of a noxious stimulus under propofol alone did, however, significantly increase HR and PaO₂, and these responses were not blunted by the addition of ketamine. Compared with propofol, administration of ketamine and reduction of propofol concentration significantly increased PAP and venous admixture, and significantly decreased PaO₂. Although application of a noxious stimulus to cats under propofol alone did not significantly change CVP, SI, CI, PVRI, oxygen delivery index, and oxygen consumption index, significant differences were found in these variables between propofol and propofol/ketamine. In conclusion, propofol alone provided cardiopulmonary stability; addition of ketamine did not improve hemodynamics but did decrease oxygenation.     

Effect of intravenous propofol and remifentanil on heart rate, blood pressure and nociceptive response in acepromazine premedicated dogs

ObjectiveTo investigate the cardiorespiratory, nociceptive and endocrine effects of the combination of propofol and remifentanil, in dogs sedated with acepromazine.Study designProspective randomized, blinded, cross-over experimental trial.AnimalsTwelve healthy adult female cross-breed dogs, mean weight 18.4 ± 2.3 kg.MethodsDogs were sedated with intravenous (IV) acepromazine (0.05 mg kg^?1) followed by induction of anesthesia with IV propofol (5 mg kg^?1). Anesthesia was maintained with IV propofol (0.2 mg kg^?1 minute^?1) and remifentanil, infused as follows: R1, 0.125 μg kg^?1 minute^?1; R2, 0.25 μg kg^?1 minute^?1; and R3, 0.5 μg kg^?1 minute^?1. The same dogs were administered each dose of remifentanil at 1-week intervals. Heart rate (HR), mean arterial pressure (MAP), respiratory rate (f_R), end tidal CO₂ (Pe′CO₂), arterial hemoglobin O₂ saturation, blood gases, and rectal temperature were measured before induction, and 5, 15, 30, 45, 60, 75, 90, and 120 minutes after beginning the infusion. Nociceptive response was investigated by electrical stimulus (50 V, 5 Hz and 10 ms). Blood samples were collected for plasma cortisol measurements. Statistical analysis was performed by anova (p < 0.05).ResultsIn all treatments, HR decreased during anesthesia with increasing doses of remifentanil, and increased significantly immediately after the end of infusion. MAP remained stable during anesthesia (72–98 mmHg). Antinociception was proportional to the remifentanil infusion dose, and was considered satisfactory only with R2 and R3. Plasma cortisol concentration decreased during anesthesia in all treatments. Recovery was smooth and fast in all dogs.Conclusions and clinical relevanceInfusion of 0.25–0.5 μg kg^?1 minute^?1 remifentanil combined with 0.2 mg kg^?1 minute^?1 propofol produced little effect on arterial blood pressure and led to a good recovery. The analgesia produced was sufficient to control the nociceptive response applied by electrical stimulation, suggesting that it may be appropriate for performing 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 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.     

Cardiopulmonary effects and recovery characteristics of horses anesthetized with xylazine–ketamine with midazolam or propofol

Objective

To evaluate cardiopulmonary and recovery characteristics of horses administered total intravenous anesthesia (TIVA) with xylazine and ketamine combined with midazolam or propofol.

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.     

Total intravenous anesthesia with propofol and S(+)‐ketamine in rabbits

ObjectiveTo evaluate total intravenous anesthesia with propofol alone or in combination with S(+)-ketamine in rabbits undergoing surgery.Study designProspective, randomized, blinded trial.AnimalsNine 6-month-old New Zealand white rabbits, weighing 2.5–3 kg.MethodsAnimals received acepromazine (0.1 mg kg^?1) and buprenorphine (20 μg kg^?1) IM, and anesthesia was induced with propofol (2 mg kg^?1) and S(+)-ketamine (1 mg kg^?1) IV. Rabbits received two of three treatments: propofol (0.8 mg kg^?1 minute^?1) (control treatment, P), propofol (0.8 mg kg^?1 minute^?1) + S(+)-ketamine (100 μg kg^?1 minute^?1) (PK100) or propofol (0.8 mg kg^?1 minute^?1) + S(+)-ketamine (200 μg kg^?1 minute^?1) (PK200). All animals received 100% O₂ during anesthesia. Heart rate, mean arterial pressure, hemoglobin oxygen saturation and respiratory rate were measured every 5 minutes for 60 minutes. Blood-gas parameters were measured at zero time and 60 minutes. Additional propofol injections, if necessary, and recovery time were recorded.ResultsAn increase in heart rate was observed in P and PK200 up to 10 minutes after induction of anesthesia. Blood pressure decreased from baseline values during the first 10 minutes in P and PK200, and during the first 15 minutes and between 45 and 55 minutes in PK100. A reduction in respiratory rate was observed after 5 minutes in all treatments. Respiratory acidosis was observed in all treatments. Six (2.8) [median (interquartile range)] further propofol injections were necessary in P, which differed statistically from PK100 [1 (0.2)] and PK200 [2 (0.6)]. Recovery time was shorter in P compared with PK100 and PK200, being [7.5 minutes (4.11)], [17.5 minutes (10.30)], and [12 minutes (10.30)], respectively.Conclusions and clinical relevanceS(+)-ketamine potentiates propofol-induced anesthesia in rabbits, providing better maintenance of heart rate. All of these techniques were accompanied by clinically significant respiratory depression.     

Comparison of azaperone–detomidine–butorphanol–ketamine and azaperone–tiletamine–zolazepam for anaesthesia in piglets

ObjectiveTo investigate a combination of azaperone, detomidine, butorphanol and ketamine (DBK) in pigs and to compare it with the combination of azaperone, tiletamine and zolazepam (TZ).Study designProspective, randomized, blinded, cross–over study.AnimalsTwelve clinically healthy crossbred pigs aged about 2 months and weighing 16–25 kg.MethodsPigs were pre–medicated with azaperone (4 mg kg^?1). Ten minutes later anaesthesia was induced with intramuscular DBK (detomidine 0.08 mg kg^?1, butorphanol 0.2 mg kg^?1, ketamine 10 mg kg^?1) or TZ (tiletamine and zolazepam 5 mg kg^?1). The pigs were positioned in dorsal recumbency. Heart and respiratory rates, posture, anaesthesia score, PaO₂, PaCO₂, pH and bicarbonate concentration were measured. t–test was used to compare the areas under time–anaesthesia index curve (AUC_anindex) between treatments. Data concerning heart and respiratory rates, PaO₂, PaCO₂ and anaesthesia score were analysed with anova for repeated measurements. Wilcoxon signed rank test was used for the data concerning the duration of sedation and anaesthesia.ResultsThe sedation, analgesia and anaesthesia lasted longer after DBK than TZ. The AUC_anscore were 863 ± 423 and 452 ± 274 for DBK and TZ, respectively (p = 0.002). The duration of surgical anaesthesia lasted a median of 35 minutes (0–105 minutes) after DBK and a median of 15 minutes (0–35 minutes) after TZ (p = 0.05). Four pigs after DBK and six after TZ did not achieve the plane of surgical anaesthesia. The heart rate was lower after DBK than after TZ. Both treatments had similar effects on the other parameters measured.ConclusionsAt the doses used DBK was more effective than TZ for anaesthesia in pigs under field conditions.Clinical relevanceThe combinations can be used for sedation and minor field surgery in pigs. The doses and drugs chosen were insufficient to produce a reliable surgical plane of anaesthesia in these young pigs.     

The isoflurane sparing effect of a medetomidine constant rate infusion in horses

This clinical study analysed the anaesthetic sparing effect of a medetomidine constant rate infusion (CRI) during isoflurane anaesthesia in horses. Forty healthy horses undergoing different types of orthopaedic and soft tissue surgeries were studied in a randomized trial. Orthopaedic surgeries were primarily arthroscopies and splint bone extractions. Soft tissue surgeries were principally castrations with one ovariectomy. All horses received 0.03 mg kg^?1 acepromazine IM 1 hour prior to sedation. Group A (11 orthopaedic and nine soft tissue surgeries), was sedated with 1.1 mg kg^?1 xylazine IV, group B (13 orthopaedic and seven soft tissue surgeries) with 7 µg kg^?1 medetomidine IV. Anaesthesia was induced in both groups with 2.2 mg kg^?1 ketamine and diazepam 0.02 mg kg^?1 IV. Maintenance of anaesthesia was with isoflurane (ISO) in 100% oxygen, depth of anaesthesia was always adjusted by the first author. Group B received an additional CRI of 3.5 µg kg^?1 hour^?1 medetomidine. Respiratory rate (RR), heart rate (HR), mean arterial blood pressure (MAP), Fe ′ISO and Fe ′CO₂ were monitored with a methane insensitive monitor (Cardiocap 5, Ohmeda, Anandic, Diessenhofen) and noted every 5 minutes. Arterial blood was withdrawn for gas analysis (PaO₂, PaCO₂) 5 minutes after the induction of anaesthesia and every 30 minutes thereafter. Dobutamine (DOB) was given as a CRI to maintain mean arterial blood pressure above 70 mm Hg. Data were averaged over time (sum of measurements/number of measurements) and tested for differences between groups by unpaired t‐tests. There were no significant differences between the groups in terms of body mass (group A, 508 ± 73.7 kg; group B, 529.25 ± 78.4 kg) or duration of anaesthesia (group A, 125.5 ± 36 minutes; group B, 121.5 ± 48.4 minutes). The mean Fe ′ISO required to maintain a surgical plane of anaesthesia was significantly higher in group A (1.33 ± 0.13%) than in group B (1.07 ± 0.19%; p = 2.78 × 10^?5). Heart rate was different between the two groups (group A, 42.2 ± 8.3; group B, 32.6 ± 3.5; p = 8.8 × 10^?5). Dobutamine requirements were higher in group A (group A, 0.72 ± 0.24 μg kg^?1 minute^?1; group B, 0.53 ± 0.23 μg kg^?1 minute^?1; p = 0.023). Respiratory rate, Fe ′CO₂, PaO₂, PaCO₂ were not different between the groups. Adjustment of anaesthetic depth subjectively was easier with the medetomidine infusion and isoflurane (group B) than with isoflurane as a sole agent (group A). In group A 12 horses and in group B five horses showed purposeful movements on 27 (A) and 12 (B) occasions. They were given thiopental (group A, 0.0114 mg kg^?1 minute^?1; group B, 0.0023 mg kg^?1 minute^?1). In group A, a further 17 horses were given ketamine to deepen anaesthesia (52 occasions, 0.00426 mg kg^?1 minute^?1) whereas in group B only nine horses needed ketamine (34 occasions, 0.00179 mg kg^?1 minute^?1). An infusion of 3.5 µg kg^?1 MED during ISO anaesthesia resulted in a significantly reduced ISO requirement.     

The effects of yohimbine on the pharmacokinetic parameters of detomidine in the horse

ObjectiveTo describe the pharmacokinetics of detomidine and yohimbine when administered in combination.Study designRandomized crossover design.AnimalsNine healthy adult horses aged 9 ± 4 years and weighing of 561 ± 56 kg.MethodsThree dose regimens were employed in the current study. 1) 0.03 mg kg^?1 detomidine IV (D), 2) 0.2 mg kg^?1 yohimbine IV (Y) and 3) 0.03 mg kg^?1 detomidine IV followed 15 minutes later by 0.2 mg kg^?1 yohimbine IV (DY). Each horse received all three dose regimens with a minimum of 1 week in between subsequent regimens. Blood samples were obtained and plasma analyzed for detomidine and yohimbine concentrations by liquid chromatography-mass spectrometry. Data were analyzed using both non-compartmental and compartmental analysis.ResultsThe maximum measured detomidine concentrations were 76.0 and 129.9 ng mL^?1 for the D and DY treatments, respectively. Systemic clearance and volume of distribution of detomidine were not significantly different for either treatment. There was a significant increase in the maximum measured yohimbine plasma concentrations from Y (173.9 ng mL^?1) to DY (289.8 ng mL^?1). Both the Cl and V_d for yohimbine were significantly less (6.8 mL minute^?1 kg^?1 (Cl) and 1.7 L kg^?1 (V_d)) for the DY as compared to the Y treatments (13.9 mL minute^?1 kg^?1 (Cl) and 2.7 L kg^?1 (V_d)). Plasma concentrations were below the limit of quantitation (0.05 and 0.5 ng mL^?1) by 18 hours for both detomidine and yohimbine.Conclusion and clinical relevanceThe Cl and V_d of yohimbine were affected by prior administration of detomidine. The elimination half life of yohimbine remained unaffected when administered subsequent to detomidine. However, the increased plasma concentrations in the presence of detomidine has the potential to cause untoward effects and therefore further studies to assess the physiologic effects of this combination of drugs are warranted.     

The effect of low dose rocuronium bromide on eyeball position, muscle relaxation, and ventilation in dogs

A central eyeball position is often required during sedation or anaesthesia to facilitate examination of the eye. However, use of neuromuscular blockade to produce a central eye position may result in depressed ventilation. This study evaluated the eyeball position, muscle relaxation and changes in ventilation during general anaesthesia after the IV administration of 0.1 mg kg^?1 rocuronium. With client consent, 12 dogs of different breeds, body mass 27.2 ± 11.8 kg, aged 5.6 ± 2.8 years (mean ± SD) were anaesthetized for ocular examination. Pre‐anaesthetic medication was 0.01 mg kg^?1 medetomidine and 0.2 mg kg^?1 butorphanol IV. Anaesthesia was induced with propofol to effect and maintained with 10 mg kg^?1 hour^?1 propofol by infusion. The dogs were placed in left lateral recumbency, their trachea intubated and connected to a circle breathing system (Fi O₂ = 1.0). All dogs breathed spontaneously. The superficial peroneal nerve of the right hind leg was stimulated every 15 seconds with a train‐of‐four (TOF) stimulation pattern and neuromuscular function was assessed with an acceleromyograph (TOF‐Guard). Adequacy of ventilation was measured with the Ventrak 1550. After 10 minutes of anaesthesia to allow stabilisation of baseline values, 0.1 mg kg^?1 rocuronium was administered IV. Minute volume (Vm ), tidal volume (Vt ), respiratory rate (RR), Pe ′CO₂ and maximal depression of T1 and TOF ratio were measured. Data were analysed using a paired t‐test. The changes in the eyeball position were recorded. A total of 100 ± 33 seconds after the injection of rocuronium, T1 was maximally depressed to 62 ± 21% and the TOF ratio to 42 ± 18% of baseline values. Both variables returned to baseline after 366 ± 132 seconds (T1) and 478 ± 111 seconds (TOF). There was no significant reduction in Vm (2.32 ± 1.1 L minute^?1), Vt (124.1 ± 69.3 mL) and RR (10 ± 3.8 breaths minute^?1) and no increase in Pe ′CO₂ (6.5 ± 2.1 kPa (48.8 ± 16.1 mm Hg)) throughout the procedure. The eyeball rotated to a central position 35 ± 7 seconds after rocuronium IV and remained there for a minimum of 20 ± 7 minutes in all dogs. We conclude that rocuronium at a dose of 0.1 mg kg^?1 can be administered to dogs IV with minimal changes in ventilatory variables. The eyeball is fixed in a central position for at least 20 minutes, which greatly facilitates clinical examination.     

Evaluation of cardiorespiratory and biochemical effects of ketamine‐propofol and guaifenesin‐ketamine‐xylazine anesthesia in donkeys (Equus asinus)

ObjectivesTo evaluate the cardiorespiratory and biochemical effects of ketamine-propofol (KP) or guaifenesin-ketamine-xylazine (GKX) anesthesia in donkeys.Study designProspective crossover trial.AnimalsEight healthy, standard donkeys, aged 10 ± 5 years and weighing 153 ± 23 kg.MethodsDonkeys were premedicated with 1.0 mg kg^?1 of xylazine (IV) in both treatments. Eight donkeys were administered ketamine (1.5 mg kg^?1) and propofol (0.5 mg kg^?1) for induction, and anesthesia was maintained by constant rate infusion (CRI) of ketamine (0.05 mg kg^?1 minute^?1) and propofol (0.15 mg kg^?1 minute^?1) in the KP treatment. After 10 days, diazepam (0.05 mg kg^?1) and ketamine (2.2 mg kg^?1) were administered for induction, and anesthesia was maintained by a CRI (2.0 mL kg^?1 hour^?1) of ketamine (2.0 mg mL^?1), xylazine (0.5 mg mL^?1) and guaifenesin (50 mg mL^?1) solution. Quality of anesthesia was assessed along with cardiorespiratory and biochemical measurements.ResultsAnesthetic induction took longer in GKX than in KP. The induction was considered good in 7/8 with KP and in 6/8 in GKX. Anesthetic recovery was classified as good in 7/8 animals in both treatments. Xylazine administration decreased heart rate (HR) in both treatments, but in KP the HR increased and was higher than GKX throughout the anesthetic period. Respiratory rate was higher in GKX than in KP. PaO₂ decreased significantly in both groups during the anesthetic period. Glucose concentrations [GLU] increased and rectal temperature and PCV decreased in both treatments. Arterial lactate [LAC] increased at recovery compared with all time points in KP. [GLU] and calcium were higher in GKX than in KP at recovery.Conclusion and clinical relevanceThese protocols induced significant hypoxemia but no other cardiorespiratory or metabolic changes. These protocols could be used to maintain anesthesia in donkeys, however, they were not tested in animals undergoing surgery.     

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.     

Cardiovascular responses to transvenous electrical cardioversion of atrial fibrillation in anaesthetized horses

ObjectiveTo examine the influence of direct current shock application in anaesthetized horses with atrial fibrillation (AF) and to study the effects of cardioversion to sinus rhythm (SR).Study designProspective clinical study.AnimalsEight horses successfully treated for AF (transvenous electrical cardioversion after amiodarone pre-treatment).MethodsCardioversion catheters and a pacing catheter were placed under sedation [detomidine 10 μg kg^?1 intravenously (IV)]. After additional sedation (5–10 μg kg^?1 detomidine, 0.1 mg kg^?1 methadone IV), anaesthesia was induced with ketamine, 2.2 mg kg^?1 and midazolam, 0.06 mg kg^?1 (IV) in a sling and maintained with isoflurane in oxygen. Flunixin meglumine, 1.1 mg kg^?1, was administered IV. Shocks were delivered as biphasic truncated exponential waves, synchronized with the R-wave of the electrocardiogram. Monitoring included pulse oximetry, electrocardiography, capnography, inhalational anaesthetic agent concentration, arterial blood pressure, LiDCO and PulseCO cardiac index (CI) and arterial blood gases. Values before and after the first unsuccessful shock and before and after cardioversion to SR were compared.ResultsValues before the first shock were comparable to reported values in healthy, isoflurane anaesthetized horses. Reliable CI measurements could not be obtained using the PulseCO technique. Intermittent positive pressure ventilation was required in most horses (bradypnea and/or PaCO₂ >8 kPa, 60 mmHg), while dobutamine was administered in two horses (0.3–0.5 μg kg^?1 minute^?1). After the 1st unsuccessful shock application, systolic arterial pressure (SAP) was decreased (p = 0.025), other recorded values were not influenced (CI measurements not available for this analysis). SR was associated with increases in CI (p = 0.039) and stroke index (p = 0.002) and a decrease in SAP (p = 0.030).Conclusions and clinical relevanceDespite the presence of AF, cardiovascular function was well maintained during anaesthesia and was not affected by shock application. Cardiac index and stroke index increased and SAP decreased after cardioversion.     

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.