Effect of medetomidine infusion on the anaesthetic requirements of desflurane in dogs

The objective of this paper was to evaluate the effect of constant rate infusion of medetomidine on the anaesthetic requirements of desflurane in dogs. For this, six healthy dogs were studied. Measurements for baseline were taken in the awake, unsedated dogs, then each dog received intravenously (i.v.) three anaesthetic protocols: M (no medetomidine infusion), M0.5 (infusion of medetomidine at 0.5 microg/kg/h, i.v.) or M1 (infusion of medetomidine at 1 microg/kg/h, i.v.). All dogs were sedated with medetomidine (2 microg/kg, i.v.) and measurements repeated in 10 min. Induction of anaesthesia was delivered with propofol (3 mg/kg, i.v.) and maintained with desflurane for 90 min to achieve a defined surgical plane of anaesthesia in all cases. After tracheal intubation infusion of medetomidine was initiated and maintained until the end of anaesthesia. Cardiovascular, respiratory, arterial pH (pHa) and arterial blood gas tensions (PaO(2), PaCO(2)) variables were measured during the procedure. End tidal desflurane concentration (EtDES) was recorded throughout anaesthesia. Time to extubation, time to sternal recumbency and time to standing were also noted. Heart rate and respiratory rate were significantly decreased during sedation in all protocols compared to baseline values. Mean heart rate, mean arterial pressure, systolic arterial pressure, diastolic arterial pressure, respiratory rate, tidal volume, arterial oxygen saturation, end-tidal CO(2), pHa, PaO(2), and PaCO(2) during anaesthesia were similar for all protocols. EtDES for M (8.6 +/- 0.8%) was statistically higher than for M0.5 (7.6 +/- 0.5%) and M1 (7.3 +/- 0.7%) protocols. Infusion of medetomidine reduces desflurane concentration required to maintain anaesthesia in dogs.     

Infusion of a combination of propofol and medetomidine for long-term anesthesia in ponies

OBJECTIVE: To determine the minimal infusion rate of propofol in combination with medetomidine for long-term anesthesia in ponies and the effects of atipamezole on recovery. ANIMALS: 12 ponies. PROCEDURE: Ponies were sedated with medetomidine (7 microg/kg of body weight, IV). Ten minutes later, anesthesia was induced with propofol (2 mg/kg, IV). Anesthesia was maintained for 4 hours, using an infusion of medetomidine (3.5 microg/kg per hour, IV) and propofol at a rate sufficient to prevent ponies from moving after electrical stimulation. Arterial blood pressures and blood gas analysis, heart rates, and respiratory rates were monitored. For recovery, 6 ponies were given atipamezole (60 microg/kg, IV). Induction and recovery were scored. RESULTS: Minimal propofol infusion rates ranged from 0.06 to 0.1 mg/kg per min. Mean arterial blood pressure was stable (range, 74 to 86 mm Hg), and heart rate (34 to 51 beats/min) had minimal variations. Variable breathing patterns were observed. Mean PaO2 (range, 116 to 146 mm Hg) and mean PaCO2 (range, 48 to 51 mm Hg) did not change significantly with time, but hypoxemia was evident in some ponies (minimal PaO2, 47 mm Hg). Recovery was fast and uneventful with and without atipamezole (completed in 20.2 and 20.9 minutes, respectively). CONCLUSIONS AND CLINICAL RELEVANCE: Infusion of a combination of medetomidine and propofol was suitable for prolonged anesthesia in ponies. Recovery was rapid and uneventful. A combination of propofol and medetomidine may prove suitable for long-term anesthesia in horses. Monitoring of blood gases is essential because of potential hypoxemia.     

Dexmedetomidine or medetomidine premedication before propofol-desflurane anaesthesia in dogs

The objective of this study was to evaluate dexmedetomidine as a premedicant in dogs prior to propofol-desflurane anaesthesia, and to compare it with medetomidine. Six healthy dogs were anaesthetized. Each dog received intravenously (i.v.) five preanaesthetic protocols: D1 (dexmedetomidine, 1 microg/kg, i.v.), D2 (dexmedetomidine, 2 microg/kg, i.v.), M1 (medetomidine, 1 microg/kg, i.v.), M2 (medetomidine, 2 microg/kg, i.v.), or M4 (medetomidine, 4 microg/kg, i.v.). Anaesthesia was induced with propofol (2.3-3.3 mg/kg) and maintained with desflurane. The following variables were studied: heart rate (HR), mean arterial pressure, systolic arterial pressure, diastolic arterial pressure, respiratory rate (RR), arterial oxygen saturation, end-tidal CO2, end-tidal concentration of desflurane (EtDES) required for maintenance of anaesthesia and tidal volume. Arterial blood pH (pHa) and arterial blood gas tensions (PaO2, PaCO2) were measured during anaesthesia. Time to extubation, time to sternal recumbency and time to standing were also recorded. HR and RR decreased significantly during sedation in all protocols. Cardiorespiratory variables during anaesthesia were statistically similar for all protocols. EtDES was significantly different between D1 (8.1%) and D2 (7.5%), and between all doses of medetomidine. Desflurane requirements were similar for D1 and M2, and for D2 and M4 protocols. No statistical differences were observed in recovery times. The combination of dexmedetomidine, propofol and desflurane appears to be effective for induction and maintenance of general anaesthesia in healthy dogs.     

Comparison of thiopentone/guaifenesin, ketamine/guaifenesin and ketamine/midazolam for the induction of horses to be anaesthetised with isoflurane

Forty-eight horses subjected to elective surgery were randomly assigned to three groups of 16 horses. After premedication with 0.1 mg/kg acepromazine intramuscularly and 0.6 mg/kg xylazine intravenously, anaesthesia was induced either with 2 g thiopentone in 500 ml of a 10 per cent guaifenesin solution, given intravenously at a dose of 1 ml/kg (group TG), or with 100 mg/kg guaifenesin and 2.2 mg/kg ketamine given intravenously (group KG), or with 0.06 mg/kg midazolam, and 2.2 mg/kg ketamine given intravenously (group KM). Anaesthesia was maintained with isoflurane. The mean (sd) end tidal isoflurane concentration (per cent) needed to maintain a light surgical anaesthesia (stage III, plane 2) was significantly lower in group KM (0.91 [0.03]) than in groups TG (1.11 [0.03]) and KG (1.14 [0.03]). The mean (sd) arterial pressure (mmHg) was significantly lower in group KG (67.4 [2.07]) than in groups TC (75.6 [2.23]) and KM (81.0 [2.16]). There were no significant differences in the logarithm of the heart rate, recovery time or quality of recovery between the three induction groups. However, pronounced ataxia was observed in the horses of group KM, especially after periods of anaesthesia lasting less than 75 minutes.     

Medetomidine-ketamine anaesthesia induction followed by medetomidine-propofol in ponies: infusion rates and cardiopulmonary side effects

REASONS FOR PERFORMING STUDY: To search for long-term total i.v. anaesthesia techniques as a potential alternative to inhalation anaesthesia. OBJECTIVES: To determine cardiopulmonary effects and anaesthesia quality of medetomidine-ketamine anaesthesia induction followed by 4 h of medetomidine-propofol anaesthesia in 6 ponies. METHODS: Sedation consisted of 7 microg/kg bwt medetomidine i.v. followed after 10 min by 2 mg/kg bwt i.v. ketamine. Anaesthesia was maintained for 4 h with 3.5 microg/kg bwt/h medetomidine and propofol at minimum infusion dose rates determined by application of supramaximal electrical pain stimuli. Ventilation was spontaneous (F(I)O2 > 0.9). Cardiopulmonary measurements were always taken before electrical stimulation, 15 mins after anaesthesia induction and at 25 min intervals. RESULTS: Anaesthesia induction was excellent and movements after pain stimuli were subsequently gentle. Mean propofol infusion rates were 0.89-0.1 mg/kg bwt/min. No changes in cardiopulmonary variables occured over time. Range of mean values recorded was: respiratory rate 13.0-15.8 breaths/min; PaO2 29.1-37.9 kPa; PaCO2 6.2-6.9 kPa; heart rate 31.2-40.8 beats/min; mean arterial pressure 90.0-120.8 mmHg; cardiac index 44.1-59.8 ml/kg bwt/min; mean pulmonary arterial pressure 11.8-16.4 mmHg. Recovery to standing was an average of 31.1 mins and ponies stood within one or 2 attempts. CONCLUSIONS: In this paper, ketamine anaesthesia induction avoided the problems encountered previously with propofol. Cardiovascular function was remarkably stable. Hypoxaemia did not occur but, despite F(I)O2 of > 0.9, minimal PaO2 in one pony after 4 h anaesthesia was 8.5 kPa. POTENTIAL RELEVANCE: The described regime might offer a good, practicable alternative to inhalation anaesthesia and has potential for reducing the fatality rate in horses.     

Cardiopulmonary effects of romifidine and detomidine used as premedicants for ketamine/halothane anaesthesia in ponies

The cardiopulmonary effects of romifidine at 80 microg/kg (R80) or 120 pg/kg (R120), and detomidine at 20 pg/kg (D20) when used as premedicants for ketamine/halothane anaesthesia were investigated in six ponies. Using a blinded crossover design, acepromazine (0-04 mg/kg) was administered followed by the alpha-2 agonist. Anaesthesia was induced with ketamine at 2.2 mg/kg and maintained with halothane (expired concentration 1.0 per cent) in oxygen for three hours. During anaesthesia, arterial blood pressure, cardiac index, PaO2 and PmvO2 decreased, and systemic vascular resistance and PaCO2 increased. The cardiac indices for R80, R120 and D20 were, respectively, 39, 39 and 32 ml/kg/minute at 30 minutes and 29, 29 and 26 ml/kg/minute at 180 minutes. The alpha-2 agonists had similar cardiovascular effects, but PaO2 was significantly lower with R120. The quality of anaesthesia was similar in all three groups.     

Cardiopulmonary effects of prolonged anesthesia via propofol-medetomidine infusion in ponies

OBJECTIVE: To determine cardiopulmonary effects of total IV anesthesia with propofol and medetomidine in ponies and effect of atipamezole on recovery. ANIMALS: 10 ponies. PROCEDURE: After sedation was induced by IV administration of medetomidine (7 microg/kg of body weight), anesthesia was induced by IV administration of propofol 12 mg/kg) and maintained for 4 hours with infusions of medetomidine (3.5 microg/kg per hour) and propofol 10.07 to 0.11 mg/kg per minute). Spontaneous respiration was supplemented with oxygen. Cardiopulmonary measurements and blood concentrations of propofol were determined during anesthesia. Five ponies received atipamezole (60 microg/kg) during recovery. RESULTS: During anesthesia, mean cardiac index and heart rate increased significantly until 150 minutes, then decreased until cessation of anesthesia. Mean arterial pressure and systemic vascular resistance index increased significantly between 150 minutes and 4 hours. In 4 ponies, PaO2 decreased to < 60 mm Hg. Mean blood propofol concentrations from 20 minutes after induction onwards ranged from 2.3 to 3.5 microg/ml. Recoveries were without complications and were complete within 28 minutes with atipamezole administration and 39 minutes without atipamezole administration. CONCLUSIONS AND CLINICAL RELEVANCE: During total IV anesthesia of long duration with medetomidine-propofol, cardiovascular function is comparable to or better than under inhalation anesthesia. This technique may prove suitable in equids in which prompt recovery is essential; however, in some animals severe hypoxia may develop and oxygen supplementation may be necessary.     

Total intravenous anaesthesia with propofol or propofol/ketamine in spontaneously breathing dogs premedicated with medetomidine

The cardiorespiratory parameters, the depth of anaesthesia and the quality of recovery were evaluated in six spontaneously breathing dogs that had been premedicated with medetomidine (40 microg/kg, supplemented with 20 microg/kg an hour later), administered with either propofol (1 mg/kg followed by 0.15 mg/kg/minute, intravenously), or with ketamine (1 mg/kg followed by 2 mg/kg/hour, intravenously) and propofol (0.5 mg/kg followed by 0.075 mg/kg/minute, intravenously). The dogs' heart rate and mean arterial blood pressure were higher and their minute volume of respiration and temperature were lower when they were anaesthetised with propofol plus ketamine, and a progressive hypercapnia leading to respiratory acidosis was more pronounced. When the dogs were anaesthetised with propofol/ketamine they recovered more quickly, but suffered some unwanted side effects. When the dogs were anaesthetised with propofol alone they recovered more slowly but uneventfully.     

Effects of four anaesthetic protocols on the neurological and cardiorespiratory variables of puppies born by caesarean section

Twenty-four bitches which had been in labour for less than 12 hours were randomly divided into four groups of six. They all received 0.5 mg/kg of chlorpromazine intravenously as premedication, followed 15 minutes later by either 8 mg/kg of thiopentone intravenously (group 1), 2 mg/kg of ketamine and 0.5 mg/kg of midazolam intravenously (group 2), 5 mg/kg of propofol intravenously (group 3), or 2.5 mg/kg of 2 per cent lidocaine with adrenaline and 0.625 mg/kg of 0.5 per cent bupivacaine with adrenaline epidurally (group 4). Except for group 4, the bitches were intubated and anaesthesia was maintained with enflurane. The puppies' heart and respiratory rates and their pain, sucking, anogenital, magnum and flexion reflexes were measured as they were removed from the uterus. The puppies' respiratory rate was higher after epidural anaesthesia. In general the puppies' neurological reflexes were most depressed after midazolam/ketamine, followed by thiopentone, propofol and epidural anaesthesia.     

A clinical comparison of two anaesthetic protocols using lidocaine or medetomidine in horses

OBJECTIVE: To compare the effects of two balanced anaesthetic protocols on end-tidal isoflurane (Fe'ISO), cardiopulmonary performance and quality of recovery in horses. DESIGN: Prospective blinded randomized clinical study. ANIMALS: Sixty-nine client-owned horses, American Society of Anesthesiologists category I and II, undergoing elective surgery. METHODS: The horses were premedicated with acepromazine (0.03 mg kg(-1)) IM 30-60 minutes before induction of anaesthesia and were randomly assigned to one of two treatments: in group L (37 horses) xylazine (1 mg kg(-1)) and in group M (31 horses) medetomidine (7 microg kg(-1)) was administered IV for sedation. Anaesthesia was induced 5 minutes later with ketamine (2.2 mg kg(-1)) and diazepam (0.02 mg kg(-1)) IV and maintained with isoflurane in oxygen/air (initial FIO2 0.40-0.50) and a constant rate infusion (CRI) of either lidocaine (2 mg kg(-1)/15 minutes loading dose followed by 50 microg kg(-1) minute(-1)) (group L) or medetomidine (3.5 microg kg(-1) hour(-1)) (group M). If horses showed movement or nystagmus, additional thiopental or ketamine was administered. Heart rate, mean arterial pressure (MAP), Fe'ISO and arterial blood gases were measured. Cardiac output was measured with the lithium dilution method in 10 (group L) and 11 (group M) horses every 45 minutes. Recovery was scored. RESULTS: Heart rate and the cardiac index (CI) were significantly higher in group L with changes over time. In group M, MAP was significantly higher during the first 50 minutes. Group L needed more additional ketamine and thiopental to maintain a surgical plane of anaesthesia and Fe'ISO was significantly higher from 70 minutes. Recovery was longer in group M and of better quality. The significance level was set at p < 0.05. CONCLUSIONS AND CLINICAL RELEVANCE: In group M, maintenance of stable anaesthetic depth was easier and lower Fe'ISO was required to maintain a surgical plane of anaesthesia. Recoveries were longer but of better quality. The CI was higher in group L but cardiovascular function was generally well maintained in both groups.     

Cardiopulmonary effects of a medetomidine-ketamine combination administered intravenously in gopher tortoises

OBJECTIVE: To determine whether IV administration of a combination of medetomidine and ketamine depresses cardiopulmonary function in healthy adult gopher tortoises. DESIGN: Prospective study. ANIMALS: 3 adult male and 3 adult female nonreleasable gopher tortoises. PROCEDURE: Prior to the study, carotid and jugular catheters were surgically placed in each tortoise for blood collection, direct arterial blood pressure monitoring, and drug administration. Heart rate, direct carotid arterial blood pressure, and body temperature were measured before and every 5 minutes for 45 minutes after IV injection of medetomidine (100 microg/kg [45.5 microg/lb]) and ketamine (5 mg/kg [2.3 mg/lb]). Carotid arterial blood samples were collected before and 5, 15, 30, and 45 minutes after medetomidine-ketamine administration to determine pH, PO2, and PCO2. Atipamezole (500 mg/kg [227 microg/lb], IV) was administered 30 minutes after administration of medetomidine-ketamine. RESULTS: The medetomidine-ketamine combination caused a moderate increase in arterial blood pressure, and moderate hypercapnia and hypoxemia. There were no significant changes in heart rate or body temperature. Intravenous administration of atipamezole rapidly induced severe hypotension. CONCLUSIONS AND CLINICAL RELEVANCE: The combination of medetomidine and ketamine administered IV resulted in effective short-term immobilization adequate for minor diagnostic procedures in gopher tortoises. This combination also caused moderate hypoventilation, and it is recommended that a supplemental source of oxygen or assisted ventilation be provided. Atipamezole administration hastens recovery from chemical immobilization but induces severe hypotension. It is recommended that atipamezole not be administered IV for reversal of medetomidine in tortoises and turtles.     

Total intravenous anaesthesia in the horse with propofol

The use of propofol, solubilised in a non-ionic emulsifying agent, for the induction and maintenance of anaesthesia in experimental ponies was assessed. Pilot studies revealed that premedication with xylazine (0.5 mg/kg bodyweight [bwt]) intravenously (iv) followed by propofol (2.0 mg/kg bwt) iv provided a satisfactory smooth induction. Two infusion rates (0.15 mg/kg bwt/min and 0.2 mg/kg bwt/min) were compared for maintenance of anaesthesia. An infusion rate of 0.2 mg/kg/min produced adequate anaesthesia in these ponies. Cardiovascular changes included a decrease in arterial pressure and cardiac output during maintenance. Respiratory depression was manifested by a decrease in rate and an increase in arterial carbon dioxide tension. Recovery after 1 h anaesthesia was rapid and smooth. In conclusion, induction and maintenance of anaesthesia with propofol in premedicated ponies proved a satisfactory technique.     

Effects of postoperative ketamine infusion on pain control and feeding behaviour in bitches undergoing mastectomy

OBJECTIVES: To determine if ketamine administered to bitches at the end of a mastectomy, followed by a six-hour constant rate infusion (CRI), improved postoperative opioid analgesia and feeding behaviour. METHODS: The bitches were randomised into three groups: the placebo group received 0.09 ml/kg isotonic saline intravenously followed by a six-hour CRI of 0.5 ml/kg/hour, the low-dose ketamine received 150 microg/kg ketamine intravenously followed by a six-hour CRI of 2 microg/kg/minute and the high-dose ketamine group received 700 microg/kg ketamine intravenously followed by a six-hour CRI of 10 microg/kg/minute. Any additional opioids given were recorded at the time of extubation and at intervals after extubation. Food intake was evaluated eight (T8) and 20 (T20) hours after extubation by measuring the per cent coverage of basal energy requirements (BER). RESULTS: No significant difference was observed for opioid requirements between the three groups. The mean percentages of BER coverage did not differ significantly at T8 but the difference between the high-dose and low-dose ketamine groups (P=0.014), and the high-dose ketamine and placebo groups (P=0.038) was significant at T20. CLINICAL SIGNIFICANCE: This study demonstrated that 700 microg/kg ketamine given intravenously postoperatively followed by a six-hour ketamine CRI of 10 microg/kg/minute improved patient feeding behaviour.     

Antagonistic activities of atipamezole, 4-aminopyridine and yohimbine against medetomidine/ketamine-induced anaesthesia in cats

The objectives of this trial were to determine the ability of atipamezole, 4-aminopyridine and yohimbine to reverse the anaesthetic effects of a combination of medetomidine and ketamine in cats. Forty healthy cats were anaesthetised with 80 micrograms/kg medetomidine combined with 5 mg/kg ketamine. Thirty minutes later atipamezole (200 or 500 micrograms/kg), 4-aminopyridine (500 or 1000 micrograms/kg) or yohimbine (250 or 500 micrograms/kg) were injected intramuscularly. The doses of antagonists were randomised, so that each dose was administered to five cats, and 10 cats were injected only with physiological saline. Atipamezole clearly reversed the anaesthesia and bradycardia induced by medetomidine and ketamine. The mean (+/- sd) arousal times were 28 (+/- 4.7), 5.8 (+/- 1.8) and 7 (+/- 2.1) minutes in the placebo group, and the groups receiving 200 and 500 micrograms/kg atipamezole, respectively. The heart rates of the cats receiving 200 micrograms/kg atipamezole rapidly returned to values close to the initial ones, but 15 minutes after the injection of 500 micrograms/kg atipamezole a significant tachycardia was observed. All the cats showed moderate signs of ataxia during the recovery period. A dose of 500 micrograms/kg yohimbine also clearly reversed the anaesthetic effects of medetomidine/ketamine but 250 micrograms/kg was not effective. The dose of 500 micrograms/kg allowed a smooth recovery with no particular side effects except for some signs of incomplete antagonism of the ketamine effects, ie, ataxia and muscular incoordination. With 4-aminopyridine there were no statistically significant effects on the recovery, or the heart and respiratory rates of the cats anaesthetised with medetomidine/ketamine.     

Stress responses during total intravenous anaesthesia in ponies with detomidine - guaiphenesin - ketamine

Six ponies were anaesthetised for two hours with intermittent injections of a combination of guaiphenesin (72 mg/kg/hr), ketamine (1.4 mg/kg/hr) and detomidine (0.015 mg/kg/hr) after premedication with detomidine 0.01 mg/kg and induction of anaesthesia with guaiphenesin 50 mg/kg and ketamine 2 mg/kg. Induction of anaesthesia was smooth, the ponies were easily intubated and after intubation breathed 100% oxygen spontaneously. During anaesthesia mean pulse rate ranged between 31–44 beats per minute and mean respiratory rate between 12–23 breaths per minute. Mean arterial blood pressure remained between 110–130 mm Hg, mean arterial carbon dioxide tension between 6.1–6.9 kPa and pH between 737–7.42. Arterial oxygen tension was over 23 kPa throughout anaesthesia. Plasma glucose increased to more than 25 mmol per litre during anaesthesia; there was no change in lactate or ACTH concentration and plasma cortisol concentration decreased. Recovery was rapid and smooth. A guaiphenesin, ketamine and detomidine combination appeared to offer potential as a total intravenous technique for maintenance of anaesthesia in horses.     

Continuous infusion of ketamine in hypovolemic dogs anesthetized with desflurane

Objective: To evaluate the cardiorespiratory effects of continuous infusion of ketamine in hypovolemic dogs anesthetized with desflurane. Design: A prospective experimental study. Animals: Twelve mixed breed dogs allocated into 2 groups: saline (n=6) and ketamine (n=6). Interventions: After obtaining baseline measurements (time [T] 0) in awake dogs, hypovolemia was induced by the removal of 40 mL of blood/kg over 30 minutes. Anesthesia was induced and maintained with desflurane (1.5 minimal alveolar concentration) and 30 minutes later (T75) a continuous intravenous (IV) infusion of saline or ketamine (100 μg/kg/min) was initiated. Cardiorespiratory evaluations were obtained 15 minutes after hemorrhage (T45), 30 minutes after desflurane anesthesia, and immediately before initiating the infusion (T75), and 5 (T80), 15 (T90), 30 (T105) and 45 (T120) minutes after beginning the infusion. Measurements and main results: Hypovolemia (T45) reduced the arterial blood pressures (systolic arterial pressure, diastolic arterial pressure [DAP] and mean arterial pressure [MAP]), cardiac (CI) and systolic (SI) indexes, and mean pulmonary arterial pressure (PAP) in both groups. After 30 minutes of desflurane anesthesia (T75), an additional decrease of MAP in both groups was observed, heart rate was higher than T0 at T75, T80, T90 and T105 in saline‐treated dogs only, and the CI was higher in the ketamine group than in the saline group at T75. Five minutes after starting the infusion (T80), respiratory rate (RR) was lower and the end‐tidal CO₂ (ETCO₂) was higher compared with values at T45 in ketamine‐treated dogs. Mean values of ETCO₂ were higher in ketamine than in saline dogs between T75 and T120. The systemic vascular resistance index (SVRI) was decreased between T80 and T120 in ketamine when compared with T45. Conclusions: Continuous IV infusion of ketamine in hypovolemic dogs anesthetized with desflurane induced an increase in ETCO₂, but other cardiorespiratory alterations did not differ from those observed when the same concentration of desflurane was used as the sole anesthetic agent. However, this study did not evaluate the effectiveness of ketamine infusion in reducing desflurane dose requirements in hypovolemic dogs or the cardiorespiratory effects of ketamine–desflurane balanced anesthesia.     

Cardiorespiratory effects of desflurane in dogs given romifidine or medetomidine before induction of anesthesia with propofol

The objective of this study was to evaluate the use of desflurane after induction of anesthesia with propofol in dogs sedated with romifidine or medetomidine. Each of 8 healthy dogs received intravenously, in random order, 3 preanesthetic protocols: romifidine, 40 microg/kg of body weight (BW) (R40); romifidine, 80 microg/kg BW (R80); and medetomidine, 10 microg/kg BW (MED). Cardiovascular and respiratory variables were recorded during the procedure. Time to extubation, time to sternal recumbency, and time to standing were also recorded. Heart rate and respiratory rate decreased significantly during sedation from baseline values, but there were no differences between the means for the 3 preanesthetic protocols. Mean values for heart rate, mean arterial blood pressure, systolic arterial pressure, diastolic arterial pressure, respiratory rate, tidal volume, arterial oxygen saturation, end-tidal CO2 level, pH, and arterial blood gas values during anesthesia were similar for the 3 protocols. The mean end-tidal desflurane concentration was significantly lower with the R80 protocol than with the R40 protocol. The mean time to extubation was significantly shorter with the R40 protocol than with the R80 and MED protocols.     

Maintenance of anaesthesia in sheep with isoflurane, desflurane or sevoflurane

Rapid recovery from anaesthesia is advantageous in small ruminants, to reduce the risk of regurgitation. Theoretically, the least soluble inhalation agents should result in the fastest recoveries, but using additional injectable agents may negate this advantage. This study compared three inhalation agents for the maintenance of anaesthesia in sheep. Eighteen ewes that were to undergo orthopaedic surgery were allocated to one of three groups. Each group was premedicated with xylazine (0.1 mg/kg intramuscularly), anaesthesia was induced using ketamine (2 mg/kg) and midazolam (0.03 mg/kg) intravenously and analgesia provided by buprenorphine (0.008 mg/kg intramuscularly). Anaesthesia was then maintained with either isoflurane, sevoflurane or desflurane. Cardiopulmonary parameters were monitored throughout. All three inhalation agents provided adequate stable anaesthesia and there was no significant difference between the groups in their cardiopulmonary parameters or their recovery times. The mead (sd) postanaesthetic times to first swallow, first chewing attempts and ability to maintain their head lifted for five minutes were, respectively, 3.95 (2.53), 6.37 (3.68) and 32.8 (18.1) minutes for isoflurane, 3.62 (0.98), 7.66 (0.78) and 38.8 (16.6) minutes for sevoflurane, and 4.37 (1.65), 6.95 (1.52) and 29.8 (11.5) minutes for desflurane. Two sheep had poor quality recoveries after the use of sevoflurane, but all the other sheep recovered uneventfully. All three inhalation agents were suitable for the maintenance of anaesthesia in sheep but, as used in this study, there were no differences between them in speed of recovery.     

Simultaneous infusions of propofol and ketamine in ponies premedicated with detomidine: a pharmacokinetic study

The pharmacokinetics of propofol and ketamine administered together by infusion were investigated in four ponies. Blood propofol and plasma ketamine and norketamine concentrations were measured by high performance liquid chromatography. After premedication with detomidine (20 μg kg⁻¹) anaesthesia was induced with ketamine (2·2 mg kg ⁻¹ intravenously). The trachea was intubated and the ponies were allowed to breathe 100 per cent oxygen. A bolus dose of propofol (0·5 mg kg⁻¹) was then administered intravenously and propofol and ketamine were infused for 60 and 45 minutes, respectively. The average mean infusion rate of propofol was 0·136 mg kg⁻¹ min⁻¹, and the ketamine infusion rate was maintained at 50 μg kg⁻¹ min⁻¹. The mean (SD) elimination half-lives of propofol and ketamine were 69·0 (8·0) and 89·8 (26·7) minutes, the mean volumes of distribution at steady state were 0·894 (0·161) litre kg⁻¹ and 1·432 (0·324) litre kg⁻¹ the mean body clearances were 33·1 (4·5) and 23·9 (3·8) ml kg⁻¹ min⁻¹ and the mean residence times for the infusion were 87·1 (4·1) and 110·7 (8·2) minutes, respectively. Norketamine, the main metabolite of ketamine, was detected throughout the sampling period. The mean residence time for norketamine was 144 (16) minutes. All the ponies recovered quickly from the anaesthesia; the mean times to sternal recumbency and standing were 11·1 (5·3) and 30·0 (20·8) minutes, respectively, from the end of the infusion.