Propofol-halothane-nitrous oxide/oxygen anaesthesia for mega-voltage radiotherapy in dogs

Observations were made on 49 dogs aged 3–13 years, of ASA Grades I and 11, during 83 periods of mega-voltage radiotherapy. The dogs weighed 5.847.0 kg and the total duration of anaesthesia ranged from 12–52 min (mean ± sem, 22 ± 8). No premedication was given. Anaesthesia was induced with iv propofol and, following endotracheal intubation, maintained with halothane/nitrous oxide/oxygen and intermittent injections of propofol. The dose of propofol needed to induce jaw relaxation sufficient for intubation was 3.5–10.8 mgkg bwt (5.67 ± 0.15) administered over 7–137 s (36 ± 2). On 91 occasions in 54 periods of anaesthesia, supplementary doses of propofol ranging from 0.2–4.9 mg/kg bwt (1.42 ± 0.14) were needed during positioning for irradiation. The times elapsing from extubation to swallowing, response to voice, spontaneous head lifting and walking were 3, 6, 7 and 13 min, respectively. A 12% incidence of tonic-clonic movements indicated that the method of anaesthesia cannot be regarded as entirely satisfactory for mega-voltage radiotherapy.     

The effects of halothane and nitrous oxide on the pharmacokinetics of propofol in dogs

The pharmacokinetics of propofol, 6.5 mg/kg, administered as a bolus dose intravenously (i.v.) were studied in six dogs (group 1). The effect of maintaining anaesthesia with halothane and nitrous oxide in oxygen on propofol pharmacokinetics was also investigated in six dogs undergoing routine anaesthesia (group 2). Induction of anaesthesia was rapid in all animals. Post-induction apnoea was a feature in three of the 12 dogs. The blood propofol concentration-time profile was best described by a bi-exponential decline in two dogs in group 1 and in 3 dogs in group 2, and by a tri-exponential decline in four dogs in group 1 and 3 dogs in group 2. The elimination half-life was long in both groups (90.9 min and 75.2 min, respectively), the volume of distribution at steady state large (4889 and 4863 ml/kg) and the clearance rapid (58.6 and 56.3 ml/kg.min). There were no significant differences between the groups, thus indicating that maintenance of anaesthesia with halothane and nitrous oxide had no effect on the pharmacokinetics of propofol in the dog.     

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.     

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. 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 regimes myocardial oxygen consumption appeared to increase with increasing duration of anaesthesia. Propofol infusion was associated with a 16 per cent incidence of vomiting in the recovery period. Maintenance of anaesthesia in healthy dogs by the continuous infusion of propofol appeared to be safe but less satisfactory than the use of halothane/nitrous oxide.     

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.     

Speed of induction of anaesthesia in dogs administered halothane, isoflurane, sevoflurane or propofol in a clinical setting

OBJECTIVE: To compare the speed and quality of induction of general anaesthesia using three different inhalant agents and one intravenous agent, in healthy dogs undergoing desexing surgery. MATERIALS AND METHODS: Less excitable dogs were not premedicated; others were premedicated with intramuscular acepromazine and morphine. Anaesthesia induction protocol was randomly assigned, with halothane, isoflurane or sevoflurane delivered by mask, or propofol delivered intravenously. Maximum vaporiser settings were used for inhalant inductions. Induction of anaesthesia was considered complete at the time of endotracheal intubation. Quality of induction was scored by the administering veterinarian. RESULTS: Seventy-one dogs were enrolled. Twenty-four received no premedication and 47 received premedication. Isoflurane inductions were significantly faster than halothane inductions (2.86 +/- 0.25 vs 3.71 +/- 0.22 min; mean +/- SE, P = 0.013). Sevoflurane inductions (3.29 +/- 0.24 min) were not significantly different from either halothane (3.71 +/- 0.22 min, P = 0.202) or isoflurane inductions (2.86 +/- 0.25 min, P = 0.217). Induction with propofol (1.43 +/- 0.13 min) was significantly faster than inhalant induction (P < 0.001 in each case). Premedication decreased the dose requirement and time to induction for dogs induced with propofol, but did not significantly change the time to intubation for inhalant inductions. Dogs administered propofol and/or premedication were significantly more likely to have an excellent quality of induction, but there was no difference between inhalant agents in terms of induction quality. CONCLUSION: Sevoflurane possesses chemical properties that should produce a more rapid induction of anaesthesia in comparison to halothane or isoflurane. However, in clinical practice patient related factors outweigh this improvement.     

Anaesthetic regimes for cataract removal in the dog

Dogs scheduled for elective removal of non-diabetic cataracts were assigned to one of four anaesthetic regimes. Thiopentone (Intraval Sodium; RMB Animal Health) or propofol (Rapinovet; Coopers Pitman-Moore) was used as the induction agent and with each agent half the animals were paralysed with vecuronium (Nor-curon; Organon Teknika) and ventilated mechanically, and half breathed spontaneously. Anaesthesia was maintained with halothane (Halothane-M&B; RMB Animal Health) and nitrous oxide (BOC) in oxygen. The use of muscle relaxants significantly improved the eye position and significantly reduced the lowest halothane vaporiser setting used during anaesthesia. Propofol produced a significantly shorter recovery time than thiopentone.     

Development of an opiate-based anaesthetic technique for use in dogs with cardiomyopathy.

An opiate-based anaesthetic technique has been developed for use in dogs with end-stage heart failure due to dilated cardiomyopathy. It has been used in dogs undergoing translocation of the left latissimus dorsi around the descending thoracic aorta to create an autologous counterpulsation system. Anaesthesia was induced with barbiturate (10 mg/kg thiopentone) and fentanyl (500 micrograms) and maintained by an infusion of fentanyl (0.5 micrograms/kg/minute) [corrected] in addition to halothane (0.1 to 0.5 per cent) and nitrous oxide (20 to 60 per cent). This technique provided safe anaesthesia for major intrathoracic surgery.     

A comparison of preoperative morphine and buprenorphine for postoperative analgesia for arthrotomy in dogs

The aim of this study was to compare morphine with the partial agonist, buprenorphine, for postoperative analgesic effects, when administered preoperatively for elective arthrotomy in dogs. Fifty two dogs were anaesthetized for stifle, elbow, or hock arthrotomy. The dogs were premedicated 30 min prior to induction of anaesthesia with 0.03 mg/kg acepromazine intramuscularly, and either 0.3 mg/kg morphine or 0.01 mg/kg buprenorphine intramuscularly (allocated randomly). Anaesthesia was induced with thiopentone and maintained with halothane in an oxygen/nitrous oxide mixture. Pain and sedation were assessed preoperatively, and 0.5, 1, 2, 3, 5, and 7 h after the halothane was switched off, with a visual analogue scale scoring system. Pain scores did not differ significantly (morphine group median postoperative score from 30 to 40 mm, buprenophine group median postoperative score from 36 to 43 mm) and analgesia was considered adequate in the majority of cases (score less than 40 mm). Morphine produced significantly more sedation at 0.5 h after anaesthesia only. It was concluded that both opioids are equally suitable analgesics for postoperative analgesia for the elective arthrotomy in dogs.     

Medetomidine as a premedicant in dogs and its reversal by atipamezole

Medetomidine (10, 20, 40 μg/kg) was used as a premedicant before thiopentone, halothane and nitrous oxide anaesthesia in 60 dogs undergoing a variety of elective surgical and diagnostic procedures at the University of Liverpool Small Animal Hospital. The efficacy of the sedation produced by the three dose groups was evaluated using a sedation scoring system which is presented. Induction of anaesthesia was accomplished using 1–25 per cent thiopentone sodium administered slowly to effect. The mean dose of thiopentone required for intubation following 10 μ-g/kg medetomidine (group 1) was 6–9 mg/kg (SD ± 2–3 mg/kg), following 20 μ-g/kg medetomidine (group 2) was 4–5 mg/kg (SD ± 1–6 mg/kg) and following 40 μg/kg (group 3) was 2–4 mg/kg (SD ± 2–5 mg/kg). Induction of anaesthesia was generally smooth and significant apnoea (greater than 45 seconds) was not noted. Anaesthesia was maintained in all cases using halothane vapourised in a one part oxygen to two parts nitrous oxide mixture, delivered to the patient via a suitable non-breathing circuit (Magill, Bain or T Piece). At the conclusion of the procedure, atipamezole (50, 100, 200 μg/kg) was administered intramuscularly to half of the dogs in each group (10 dogs). Dogs receiving atipamezole recovered rapidly and smoothly to sternal recumbency, group 1 taking 8-5 minutes (SD ± 2–7 minutes), group 2 taking 11-8 minutes (SD ± 3–6 minutes), and group 3 taking 12-6 minutes (sd ± 4–5 minutes). When atipamezole was not administered a dose dependent increase in recumbency time occurred.     

Effect of propofol at two injection rates or thiopentone on post-intubation apnoea in the dog

Ventilatory effects at induction of anaesthesia were studied following intubation in 66 dogs anaesthetised using thiopentone (10 mg/kg) or propofol (4 mg/kg, injected rapidly or 4 mg/kg, injected slowly). Acepromazine and morphine preanaesthetic medication was administered, and anaesthesia was maintained with halothane in nitrous oxide and oxygen. The time from connection of the breathing system to the first breath was measured. Apnoea was defined as cessation of spontaneous respiration for 15 seconds or longer. Respiratory rate and minute volume were measured for the first five minutes of anaesthesia. Propofol was associated with a greater incidence of apnoea than thiopentone (59 per cent and 64 per cent compared with 32 per cent), but this difference was not statistically significant. Time to first breath was significantly longer with propofol than thiopentone and longest with the slower injection of propofol (P<0.05) (median of four seconds for thiopentone, 19.5 seconds for the propofol rapid injection, and 28.8 seconds for the propofol slow injection). In conclusion, the induction agent and speed of injection affect the incidence and duration of post-intubation apnoea.     

Hepatic effects of halothane, isoflurane or sevoflurane anaesthesia in dogs

The effects of halothane, isoflurane and sevoflurane anaesthesia on hepatic function and hepatocellular damage were investigated in dogs, comparing the activity of hepatic enzymes and bilirubin concentration in serum. An experimental study was designed. Twenty-one clinically normal mongrel dogs were divided into three groups and accordingly anaesthetized with halothane (n = 7), isoflurane (n = 7) and sevoflurane (n = 7). The dogs were 1-4 years old, and weighed between 13.5 and 27 kg (18.4 +/- 3.9). Xylazine HCI (1-2 mg/kg) i.m. was used as pre-anaesthetic medication. Anaesthesia was induced with propofol 2 mg/kg i.v. The trachea was intubated and anaesthesia maintained with halothane, isoflurane or sevoflurane in oxygen at concentrations of 1.35, 2 and 3%, respectively. Intermittent positive pressure ventilation (tidal volume, 15 ml/kg; respiration rate, 12-14/min) was started immediately after intubation and the anaesthesia lasted for 60 min. Venous blood samples were collected before pre-medication, 24 and 48 h, and 7 and 14 days after anaesthesia. Serum level of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) and gamma-glutamyltransferase (GGT), lactate dehydrogenase (LDH GGT) activities and bilirubin concentration were measured. Serum AST, ALT and GGT activities increased after anaesthesia in all groups. In the halothane group, serum AST and ALT activities significantly increased all the time after anaesthesia compared with baseline activities. But in the isoflurane group AST and ALT activities increased only between 2 and 7 days, and in the sevoflurane group 7 days after anaesthesia. GGT activity was increased in the halothane group between 2 and 7 days, and in the isoflurane and sevoflurane groups 7 days after anaesthesia. All dogs recovered from anaesthesia without complications and none developed clinical signs of hepatic damage within 14 days. The results suggest that the use of halothane anaesthesia induces an elevation of serum activities of liver enzymes more frequently than isoflurane or sevoflurane from 2 to 14 days after anaesthesia in dogs. The effects of isoflurane or sevoflurane anaesthesia on the liver in dogs is safer than halothane anaesthesia in dogs.     

The effect of pre-anaesthetic medication on the incidence of cardiac arrhythmias during halothane anaesthesia in cats

Objective To compare the incidence of arrhythmias in cats receiving either acepromazine or diazepam for pre-anaesthetic medication prior to halothane anaesthesia.
Study design A blinded, randomized clinical study.
Animals Forty-six healthy cats undergoing surgery.
Methods Animals were allocated to one of two groups for pre-anaesthetic medication. Group 1 received diazepam (0.2 mg kg⁻¹). Group 2 received acepromazine (0.02 mg kg⁻¹). The trial drug was administered intramuscularly in combination with buprenorphine (0.01 mg kg⁻¹) 30 minutes prior to induction of anaesthesia with propofol (approximately 5 mg kg⁻¹). Anaesthesia was maintained using halothane: delivered concentration was 1–2% carried in oxygen and nitrous oxide via an endotracheal tube attached to an Ayre's T-piece (with Jackson-Rees modification) breathing system. The incidence of cardiac arrhythmias was determined by continuously monitoring the electrocardiogram from the time of induction until recovery occurred. Demographical group characteristics were compared using analysis of variance. The incidence of cardiac arrhythmias was compared by the Chi squared test. Statistical significance was set at the 5% level.
Results The two groups were similar in weight, age, length and type of procedure undertaken. The incidence of arrhythmias was the same in each group (3/23 cases) ( p = 1.0).
Conclusions The incidence of cardiac arrhythmias in this study did not appear to be influenced by the nature of pre-anaesthetic medication.
Clinical relevance The incidence of cardiac arrhythmias under halothane anaesthesia was 13% in this study. Acepromazine did not appear to exert an anti-arrhythmic effect. This may not be the case in a larger scale study.     

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.     

Effect of hypothermia on recovery from general anaesthesia in the dog

OBJECTIVE: To discern the effects of anaesthesia protocols and decreasing core body temperature on time to recovery from general anaesthesia. MATERIALS AND METHODS: Healthy adult dogs undergoing desexing surgery were enrolled. More excitable dogs were premedicated with intramuscular acepromazine and morphine; calmer dogs were not premedicated. Anaesthesia was induced using halothane, isoflurane or sevoflurane delivered by mask, or by intravenous propofol, and maintained in standard fashion using one of the three inhalant agents. Thermostat controlled heat mats were used during surgical preparation and surgery. Oesophageal temperature was recorded throughout surgery. The time from cessation of anaesthetic administration until the dog successfully raised itself to sternal recumbency was considered the time of recovery. RESULTS: Sixty-nine dogs completed the study, 42 males anaesthetised for 60.4 +/- 20.5 min, and 27 females anaesthetised for 85.4 +/- 33.2 min. Oesophageal temperature at the end of surgery was 36.8 +/- 0.80 degrees C. Oesophageal temperature had a significant effect on recovery time, with lower temperatures contributing to slower recoveries. Premedication significantly lengthened recovery times. The choice of induction or maintenance anaesthetic agent had no effect on recovery time. DISCUSSION: Hypothermia is a common complication of general anaesthesia and surgery. Amongst other deleterious effects, it is associated with slower recovery from anaesthesia, likely due to a number of different mechanisms.     

Propofol compared with propofoVguaiphenesin after detornidine premedication for equine surgery

Anaesthesia using propofol alone and in combination with guaiphenesin, after detomidine premedication, was evaluated for performance of minor surgical procedures (castration and tenotomy) in horses. Twelve male horses were premedicated with 0.015 mg/kg of detomidine intravenously (iv) and divided into two groups of six. One group of horses received 2 mg/kg of propofol iv and the other group received 0.5 mg/kg of propofol mixed with 100 mg/kg of a 7.5% solution of guaiphenesin in saline iv. Induction of anaesthesia was fast and smooth in both groups. All horses were easily intubated immediately afterwards but intubation was easier in the horses which received propofol and guaiphenesin. Heart rate fell by 20% in both groups after detomidine injection, stabilising between 45 and 53 beats/minute during anaesthesia with no difference between the groups. Respiratory depression developed after detomidine injection and was slightly intensified after induction of anaesthesia. Respiratory rate was significantly lower in the propofol group (14 ± 3 breaths/minute) than with propofol/guaiphenesin (19 ± 4 breaths/minute) at five minutes after induction. Anaesthesia induced respiratory acidosis in both groups and hypoxaemia also occurred, but once the horses stood up the arterial blood oxygen partial pressure returned to basal values. Surgical time ranged between 8 and 16 minutes and with the exception of one horse in the propofol/guaiphenesin group the horses did not show signs of pain or discomfort during surgery. Recovery to standing was fast and took 26 ± 2 minutes in the propofol and 29 ± 5 minutes in the propofol/ guaiphenesin group. Most horses stood up at the first attempt with minimal ataxia. These two anaesthetic techniques appear to be useful for minor surgical procedures performed within 16 minutes of induction of anaesthesia.     

Effects of thiopentone halothane-nitrous oxide anaesthesia compared to ketamine-xylazine anaesthesia on the DC recorded dog electroretinogram

Eleven ophthal-moscopically healthy dark adapted dogs were examined by DC ERG technique with single flash full field illumination starting with near b-wave threshold blue (tests 1-3) and white (tests 4-6) stimuli of different intensity and ending with 30 Hz photopic flicker smuli (test 7) after light adaptation. All animals were anaesthetized using 2 different anaesthetic methods: Anaesthesia I (A I): Induction with thiopentone sodium, continued with halothane and nitrous oxide in oxygen. Anaesthesia II (A II): Praemedication with xylazine hydrochloride followed by anaesthesia with ketamine hydrochloride. A minimum interval of 1 week was kept between all anaesthesias.The a- and b-wave amplitudes and latencies were determined. Statistical analysis of results indicated that the a- and b-waves were elicited by weaker intensities in A II. In Tests 3-6 the a-wave was highly significantly (P < 0.001), higher in amplitude in AII than in A I. Differencies in b-wave amplitudes were not statistically significant (except Test 1). The b-wave latencies were longer in AI in Test 2 (using low intensity blue light). The a-wave latencies were slightly shorter in AII in Test 6 (using high intensity white light).In additional experiments the selective action of the different agents (except N₂O) used in AI and AII was studied. Thiopentone alone given to 3 dogs seemed to depress the a-wave selectively.Halothane given separately to 3 dogs lowered both the a- and b-wave amplitudes. Ketamine given with a neuromuscular blocking agent to three dogs resulted in responses almost identical to those in AII.Xylazine with vecuronium given to 4 dogs resulted in responses with slighly depressed a- and b-waves in comparison to ketamine with vecuronium.The results indicate that when developing an animal model for the electrophysiologic study of human retinal dystropies, the actions of different anaesthetics upon the ERG components are of great importante.     

Induction of anaesthesia in dogs and cats with propofol

Propofol was used to induce anaesthesia in 89 dogs and 13 cats of either sex, various breeds and of widely different ages and weights; they varied considerably in physical condition and were anaesthetised for a variety of investigations and surgical procedures. They were premedicated with acepromazine, papaveretum, diazepam, pethidine, atropine and scopolamine in different combinations. After induction with propofol, anaesthesia was maintained with halothane, isoflurane, methoxyflurane and enflurane and, or, nitrous oxide. The mean (+/- sd) induction doses of propofol in unpremedicated and premedicated animals were 5.2 +/- 2.3 mg/kg and 3.6 +/- 1.4 mg/kg respectively for dogs, and 5.0 +/- 2.8 mg/kg and 5.3 +/- 4.3 mg/kg for cats. There were no differences between the sexes. Premedication did not affect recovery times. The incidence of side effects was very low. One dog showed evidence of pain when propofol was injected. No incompatibility was observed between propofol and the premedicants and other anaesthetic agents used.     

A preliminary investigation comparing pre-operative morphine and buprenorphine for postoperative analgesia and sedation in cats

Objective To compare the postoperative analgesic and sedative properties of buprenorphine and morphine in cats. Study Design Prospective, randomized, blinded study. Animals Thirty‐two domestic cats undergoing surgery. Methods Cats received pre‐anaesthetic medication with acepromazine (0.05 mg kg^?1) given intramuscularly and were randomly allocated to group M and given morphine (0.1 mg kg^?1) intramuscularly (IM) or to group B and given buprenorphine (0.01 mg kg^?1) IM. Anaesthesia was induced with propofol and maintained with halothane in oxygen and nitrous oxide. Pain and sedation scores using visual analogue scales, and heart and respiratory rates, were measured immediately before, and 30, 60, 120, 180, 300 and 420 minutes after anaesthesia. Results Pain scores were significantly lower at 60, 120 and 180 minutes after anaesthesia in group B. Group B also had higher heart rates at 30 minutes. There were no other statistically significant differences between the groups. Clinical relevance Buprenorphine (0.01 mg kg^?1) appeared to provide better postoperative analgesia than morphine (0.1 mg kg^?1) and may also have a longer duration of action.     

The effects of nitrous oxide on recovery from isoflurane anaesthesia in dogs

O bjectives : To assess rate and quality of recovery from anaesthesia where isoflurane was delivered in oxygen or oxygen/nitrous oxide.
M ethods : Dogs anaesthetised with propofol were randomly allocated to receive isoflurane maintenance in either 100 per cent oxygen (group 1) or 66 per cent nitrous oxide (N₂O)/34 per cent oxygen (group 2). Time from end of anaesthesia to achieving sternal recumbency was recorded. Incidence of adverse behaviours (vocalisation, uncontrolled head movement and restlessness) were assessed. Recovery quality was recorded on a visual analogue scale (VAS) (anchored at 0 with "best possible" recovery and "did not recover" at 100 mm). Age, weight, gender, anaesthetic duration, mean vaporiser setting, VAS scores, recovery times, postoperative temperature and behavioural scores were compared (chi-squared test, Mann-Whitney U test or t -test as appropriate, significance P≤0·05).
R esults : Objective data from 54 dogs were analysed, only VAS data where the observer was unaware of treatment group were used (n=33). Recovery was faster in group 2 dogs (median 10 min [range 4 to 31] compared with 14 minutes [3 to 43] in group 1, P=0·049) with less restlessness (0 [0 to 4] compared with 2 [0 to 4] in group 1, P=0·013) and uncontrolled head movement (0 [0 to 4] compared with 1 [0 to 3] in group 1, P<0·001). However, VAS scores were not statistically different between groups (group 1: mean 39·4 mm [s.d. 24·0)]; group 2: 30·1 mm [25·9]; P=0·303).
C linical S ignificance : Addition of N₂O to isoflurane anaesthesia results in a lower incidence of adverse behaviour (for example restlessness) and marginally faster recovery.