Risk of anaesthetic mortality in dogs and cats: an observational cohort study of 3546 cases

Objective To evaluate the anaesthetic death risk for dogs and cats in a French private practice. Study design Observational cohort study. Animal population All small animals anesthetized at the Centre Hospitalier Vétérinaire des Cordeliers between April 15th, 2008 and April 15th, 2010. Methods General anaesthesia was defined as a drug‐induced unconsciousness characterised by a controlled and reversible depression of the central nervous system and analgesia, sufficient to allow endotracheal intubation. Patient outcome (alive or dead) was assessed at the end of anaesthesia defined as the meeting point of the return of consciousness, rectal temperature >36 °C and ability to maintain sternal recumbency. Death occurring during anaesthesia was recorded. Relationship between anaesthetic death and ASA status, species, age, nature of the procedure, anaesthetic protocol and occurrence of epidural administration of a combination of morphine and bupivacaine were analysed. Results During the study period 3546 animals underwent general anaesthesia. The overall death rate in the present study was 1.35% (48 in 3546, 95% CI 0.96–1.75). The death rate of healthy animals (ASA 1 and 2) was 0.12% (3 in 2602 95% CI 0.02–0.34). For sick animals (ASA status 3 and over), the overall death rate was 4.77% (45 in 944 95% CI 3.36–6.18). The death rates in the ASA 3, 4 and 5 categories were 2.90%, 7.58% and 17.33%, respectively. The main factor associated with increased odds of anaesthetic death in ASA categories 3 and over was poor health status (ASA physical status classification). The nature of the procedure the patient underwent and epidural administration of a combination of morphine and bupivacaine were not correlated with the occurrence of death during anaesthesia. Neither species nor age effects were detected. Conclusion and clinical relevance Specific factors were associated with increased odds of anaesthetic death, especially poor health status. Efforts must be directed towards thorough preoperative patient evaluation and improvement of clinical conditions if possible. Identification of risk factors before anaesthesia should lead to increased surveillance by trained staff. This could result in better outcomes.     

Survey on small animal anaesthesia

OBJECTIVE: To ascertain anaesthetic practices currently for dogs and cats in Australia. METHODS: A questionnaire was distributed to 4,800 veterinarians throughout Australia, seeking data on numbers of dogs and cats anaesthetised per week; drug preferences for anaesthetic premedication, induction and maintenance; use of tracheal intubation, supplemental nitrous oxide and anaesthetic antagonists; and types of vaporisers, breathing systems and anaesthetic monitoring devices used or available. Additional questions concerned proportions of different animal types seen in the practice, and the respondent's university and year of graduation. RESULTS: The response rate was 19%; 95% of respondents graduated from Australian universities, about half since 1985. Most responses (79%) came from mainly small animal practices. On average 16 dogs and 12 cats were anaesthetised each week. Premedication was used more often in dogs than cats, with acepromazine and atropine most favoured in both species. For anaesthetic induction, thiopentone was most preferred in dogs and alphaxalone/alphadolone in cats. Inhaled agents, especially halothane, were preferred for maintenance in both species. Most respondents usually employed tracheal intubation when using inhalational anaesthetic maintenance, but intubation rates were lower during injectable anaesthetic maintenance and a minority of respondents provided supplemental O2. Nitrous oxide was administered regularly by 13% of respondents. The agents most frequently used to speed recovery from anaesthesia were doxapram and yohimbine. The most widely used vaporisers were the Fluotec Mark III and the Stephens machine. Most (95%) respondents used a rebreathing circuit for large dogs and a non-rebreathing system was used for small dogs by 68% of respondents. Most respondents (93%) indicated some form of aid was available to monitor general anaesthesia: the three most mentioned were an apnoea alarm, oesophageal stethoscope and electrocardiogram. CONCLUSION: Diverse approaches were evident, but there appeared to be less variation in anaesthetising dogs: premedication was more frequent and less varied in type, while thiobarbituates dominated for induction and inhalants for maintenance. Injectable maintenance techniques had substantial use in cats, but little in dogs. Evident disparity between vaporisers available and circuits used suggested either confusion in terminology or incorrect use of some vaporisers in-circuit. While most respondents used monitoring equipment or a dedicated observer to invigilate anaesthesia, the common reliance on apnoea alarms is of concern, because of unproven reliability and accuracy.     

A survey of dog and cat anaesthesia in a sample of veterinary practices in New Zealand

AIMS: To survey current anaesthesia practices for dogs and cats in small and mixed animal practices in New Zealand in order to improve anaesthesia education.

METHODS: A questionnaire was sent to 440 small and mixed animal practices, including questions regarding the type of practice, preanaesthetic examination, anaesthetic drugs and management, anaesthetic machines, monitoring and topics of interest for continuing professional development.

RESULTS: Responses were obtained from 113/440 (26%) practices, with 78 (69%) respondents from small and 35 (31%) from mixed animal practices. A preanaesthetic physical examination was carried out by >95% of respondents and premedication was usually given to dogs (112/113; 99%) and cats (95/113; 85%). Acepromazine was the preferred sedative for dogs and cats, with morphine or buprenorphine. Propofol and alfaxalone were the preferred induction agents, and isoflurane was preferred for maintenance in both dogs and cats. A venous catheter was usually placed for anaesthesia in dogs (59/113; 52%), but less so in cats (39/113; 35%). Perioperative fluid was administered at 10?mL/kg/hour by 62/110 (56%) respondents. Intubation was usually used for anaesthesia in dogs (111/112; 99%), and cats (87/112; 78%). Almost 40% of respondents usually administered supplementary oxygen if patients were not intubated. Local analgesia was used by 69/111 (88%) respondents sometimes or always if applicable. Morphine or buprenorphine, and meloxicam were common choices for post-operative analgesia after neuter surgery in dogs and cats. A semiclosed (non-rebreathing) system was used in animals weighing <10?kg, and a Mapleson E or F non-rebreathing circuit was used by 66/109 (61%) practices. Only 15/111 (14%) practices had a ventilator in their practice. A dedicated anaesthetist was usually used by 104/113 (92%) practices, and apnoea alarms, pulse oximeters, thermometers and oesophageal stethoscopes were the main monitoring devices available in practices. Loco-regional block, pain management, and anaesthetic drugs were the main topics of interest for continuing education.

CONCLUSIONS AND CLINICAL RELEVANCE: Responses by the veterinarians taking part in this survey indicated that they had a reasonably good standard of anaesthetic practice. A physical examination was carried out preanaesthesia, and premedication including analgesia was routinely administered to most patients. A dedicated anaesthetist usually monitored patients and most respondents reported they had access to basic anaesthetic monitoring equipment. Areas where changes could lead to improved anaesthetic practice were increased use of I/V catheterisation, endotracheal intubation, and supplementary oxygen, and reduced I/V fluid rates.     

Routine veterinary anaesthetic management practices in South Africa

A survey of the routine anaesthetic management of dogs and cats during sterilisation by veterinarians in South Africa was conducted. This report describes the premedication, induction and maintenance agents most commonly used in dogs and cats. Information about monitoring of patients during the procedure and who is responsible for induction of anaesthesia and monitoring was obtained. Questionnaires were analysed with regard to demographic data, practice size, continuing education, the number of surgical procedures and sterilisations performed per week and an estimate of yearly mortality. Acetylpromazine is the most commonly used premedication in dogs and xylazine in cats. Thiopentone in dogs and alphaxalone/alphadolone in cats were the induction agents most commonly used. Alphaxalone/alphadolone in cats and halothane in dogs are the most commonly used maintenance agents. Records of anaesthesia are poorly kept and monitoring of patients is poorly performed. Respiratory rate is the parameter most commonly monitored (90.7%), and in most cases is the sole parameter. On average 10.34 +/- 8.25 cats were operated per week, of which 5.45 +/- 5.60 were sterilised; 17.79 +/- 11.61 dogs were operated per week, of which 8.65 +/- 7.10 were sterilised. In total, 190 patients died under anaesthesia, a mortality rate of 1:1,243. Just over 50% of practitioners had attended continuing education courses during their careers.     

Romifidine as a premedicant to propofol induction and infusion anaesthesia in the dog

The effects of premedication with four different intravenous doses of romifidine (20, 40, 80 and 120 (μg/kg body weight) and a saline placebo were compared in a group of 20 adult beagles of both sexes, undergoing anaesthesia with propofol for a clinical dental procedure. Anaesthesia was induced 10 minutes after premedication and maintained by intravenous infusion of propofol for a period of 30 minutes. Romifidine had a marked synergistic effect with propofol and reduced the required induction and infusion doses by more than 60 per cent for a standard level of anaesthesia; the synergistic effect was dose related. Following premedication, propofol produced no significant alteration of respiratory rate, heart rate or rectal temperature. Anaesthesia was found to be more stable following romifidine premedication at all doses studied. The quality of induction was unaltered by the dose of the romifidine. Recovery from anaesthesia was smooth and of a similar quality in all cases. There were no differences in the recovery times between the unpremedicated group and the dogs premedicated with any dose of romifidine studied. There were no adverse effects noted following this anaesthetic regimen. The marked dose-related synergism with propofol induction and infusion anaesthesia is relevant should romifidine be used in the dog in clinical veterinary practice.     

The risk of death: the confidential enquiry into perioperative small animal fatalities

Objective To estimate the risks of anaesthetic and sedation‐related mortality in companion animals in the UK. (The Confidential Enquiry into Perioperative Small Animal Fatalities, CEPSAF). Study design A prospective cohort study with nested case–control study. Animal population All small animals anaesthetized and sedated at participating centres between June 2002 and June 2004. Methods Patient outcomes at 48 hours (alive, dead and killed) were recorded. Anaesthetic and sedation‐related death was defined as death where surgical or pre‐existing medical causes did not solely cause death. Species‐specific risks of anaesthetic‐related death and 95% confidence intervals (95% CI) were calculated. Risks were also estimated in the sub‐sets of dogs, cats and rabbits that were either healthy or sick (ASA 1–2 and 3–5, respectively). Results One hundred and seventeen veterinary practices participated in the study and 98 036 dogs, 79 178 cats and 8209 rabbits were anaesthetized and sedated. Overall risks of anaesthetic and sedation‐related death in dogs were 0.17% (1 in 601, 95% CI 0.14–0.19%), in cats 0.24% (1 in 419, 95% CI 0.20–0.27%) and in rabbits 1.39% (1 in 72, 95% CI 1.14–1.64%) within 48 hours of the procedure. In healthy dogs, cats and rabbits, the risks were estimated to be 0.05% (1 in 1849, 95% CI 0.04–0.07%), 0.11%, (1 in 895, 95% CI 0.09–0.14%) and 0.73% (1 in 137, 95% CI 0.54–0.93%), respectively. In sick dogs, cats and rabbits, the risks were 1.33%, (1 in 75, 95% CI 1.07–1.60%), 1.40% (1 in 71, 95% CI 1.12–1.68%) and 7.37% (1 in 14, 95% CI 5.20–9.54%), respectively. Postoperative deaths accounted for 47% of deaths in dogs, 61% in cats and 64% in rabbits. Most other small animal species had higher mortality risks. Conclusions and clinical relevance Small animal anaesthesia appears to be increasingly safe. Greater patient care in the postoperative period could reduce fatalities.     

Comparison of sevoflurane and isoflurane in dogs anaesthetised for clinical surgical or diagnostic procedures

OBJECTIVES: To assess attributes of sevoflurane for routine clinical anaesthesia in dogs by comparison with the established volatile anaesthetic isoflurane. METHODS: One hundred and eight dogs requiring anaesthesia for elective surgery or diagnostic procedures were studied. The majority was premedicated with 0.03 mg/kg of acepromazine and 0.01 mg/kg of buprenorphine or 0.3 mg/kg of methadone before induction of anaesthesia with 2 to 4 mg/kg of propofol and 0.5 mg/kg of diazepam. They were randomly assigned to receive either sevoflurane (group S, n=50) or isoflurane (group I, n=58) in oxygen and nitrous oxide for maintenance of anaesthesia. Heart rate, respiratory rate, indirect arterial blood pressure, haemoglobin saturation, vaporiser settings, end-tidal carbon dioxide and anaesthetic concentration and oesophageal temperature were measured. Recovery was timed. Data were analysed using analysis of variance and non-parametric tests. RESULTS: Heart rate (85 to 140/minute), respiratory rate (six to 27/minute) and systolic arterial blood pressure (80 to 150 mmHg) were similar in the two groups. End-tidal carbon dioxide between 30 and 60 minutes (group S 6.4 to 6.6 and group I 5.8 to 5.9 per cent) and vaporiser settings throughout (group S 2.1 to 2.9 and group I 1.5 to 1.5 per cent) were higher in group S. There was no difference in time to head lift (18+/-16 minutes), sternal recumbency (28+/-22 minutes) or standing (48+/-32 minutes). No adverse events occurred. CLINICAL SIGNIFICANCE: Sevoflurane appeared to be a suitable volatile anaesthetic for maintenance of routine clinical anaesthesia in dogs.     

Sedative and analgesic effects of buprenorphine,combined with either acepromazine or dexmedetomidine,for premedication prior to elective surgery in cats and dogs

ObjectiveTo evaluate the sedative and analgesic effects of intramuscular buprenorphine with either dexmedetomidine or acepromazine, administered as premedication to cats and dogs undergoing elective surgery.Study designProspective, randomized, blinded clinical study.AnimalsForty dogs and 48 cats.MethodsAnimals were assigned to one of four groups, according to anaesthetic premedication and induction agent: buprenorphine 20 μg kg^?1 with either dexmedetomidine (dex) 250 μg m^?2 or acepromazine (acp) 0.03 mg kg^?1, followed by alfaxalone (ALF) or propofol (PRO). Meloxicam was administered preoperatively to all animals and anaesthesia was always maintained using isoflurane. Physiological measures and assessments of pain, sedation and mechanical nociceptive threshold (MNT) were made before and after premedication, intraoperatively, and for up to 24 hours after premedication. Data were analyzed with one-way, two-way and mixed between-within subjects anova, Kruskall–Wallis analyses and Chi squared tests. Results were deemed significant if p ≤ 0.05, except where multiple comparisons were performed (p ≤ 0.005).ResultsCats premedicated with dex were more sedated than cats premedicated with acp (p < 0.001) and ALF doses were lower in dex cats (1.2 ± 1.0 mg kg^?1) than acp cats (2.5 ± 1.9 mg kg^?1) (p = 0.041). There were no differences in sedation in dogs however PRO doses were lower in dex dogs (1.5 ± 0.8 mg kg^?1) compared to acp dogs (3.3 ± 1.1 mg kg^?1) (p < 0.001). There were no differences between groups with respect to pain scores or MNT for cats or dogs.ConclusionChoice of dex or acp, when given with buprenorphine, caused minor, clinically detectable, differences in various characteristics of anaesthesia, but not in the level of analgesia.Clinical relevanceA combination of buprenorphine with either acp or dex, followed by either PRO or ALF, and then isoflurane, accompanied by an NSAID, was suitable for anaesthesia in dogs and cats undergoing elective surgery. Choice of sedative agent may influence dose of anaesthetic induction agent.     

Complications of exploratory coeliotomy in 70 cats

Records of all cats that had undergone exploratory coeliotomy at the University of Edinburgh during the period November 1995 to July 2002 were reviewed. Seventy records were retrieved. There were 30 cats in which infection or inflammatory disorders predominated, 17 cats with neoplasia, three cats with trauma and 20 cats with other disorders. Exploratory coeliotomy was performed for diagnostic purposes in 28 cats (40 per cent), treatment in 34 cats (49 per cent) and for diagnosis and treatment in eight cats (11 per cent). Methods of intraoperative diagnosis included incisional biopsy of abdominal organs (52 cats), cytology (two cats), microbiology (17 cats) and gross appearance (17 cats). Fifty-eight cats (83 per cent) survived the hospitalisation period. Complications occurred in 18 cats (26 per cent) and were related to anaesthesia (four cats), the underlying disease process (15 cats), surgery (five cats) and were undetermined in one cat.     

Clinical evaluation of Alfaxan-CD® as an intravenous anaesthetic in young cats

Objective   To describe and evaluate the use of Alfaxan-CD ® as an intravenous anaesthetic in young cats.
Design   Thirty-five Domestic Short-hair cats aged from 3 to 12 months were admitted into the University Veterinary Teaching Hospital-Sydney for elective surgery. Anaesthesia was induced with Alfaxan-CD® and maintained with isoflurane: 22 cats received no premedication and 13 cats received acepromazine (0.03 mg/kg) and butorphanol (0.3 mg/kg) subcutaneously 30 min prior to induction.
Qualitative and quantitative data for induction and recovery were recorded. Physiological parameters were recorded at 0, 2 and 5 min post induction, and every 5 min thereafter until the end of the procedure.
Results   Intravenous injection of Alfaxan-CD® resulted in rapid induction of anaesthesia with a mean time to intubation of 122 s. The mean dose of Alfaxan-CD® used was 4.2 mg/kg in unpremedicated cats and 2.7 mg/kg in premedicated cats. All cats maintained a heart rate above 95 beats/min. No cat developed hypoxaemia. Hypercapnoea was detected in 4 cats and hypotension was observed in 18 cats. Time to extubation ranged from 1 to 9 min. The mean time to sternal recumbency for premedicated cats was 11 min; 77% of premedicated cats and 23% of unpremedicated cats had a recovery score of 1 or 2.
Conclusion   Alfaxan-CD® is an effective anaesthetic agent in young healthy cats, providing a smooth induction and rapid recovery. Cats that were premedicated with acepromazine and butorphanol prior to induction with Alfaxan-CD® had better recovery scores than those that were not premedicated.     

Complications of saffan anaesthesia in cats

Complications associated with Saffan anaesthesia were recorded following 100 administrations of the anaesthetic to cats. Hyperaemia or oedema of the pinnae or forepaws was recorded in 69 per cent of administrations. Other common complications included coughing and partial laryngean spasm at intubation, cyanosis, postoperative vomiting and opisthotonus. Suggestions are made for minimising the incidence of such complications.     

An evidence‐based medicine approach to small animal anaesthetic mortality in a referral practice: the influence of initiating three recommendations on subsequent anaesthetic deaths

ObjectiveTo evaluate anaesthetic death after implementation of recommendations and its risk factors in a small animal practice.Study designObservational cohort study.AnimalsAll cats and dogs anaesthetized at the Centre Hospitalier Vétérinaire des Cordeliers during two periods, from April 15th, 2008 to April 15th, 2010 (period 1) and from June 15th, 2010 to August 24th, 2011 (period 2).MethodsDeath occurring during or before full recovery from anaesthesia was recorded. At the end of period 1, a logistic regression model was generated to describe anaesthetic death and identify risk factors. Potential risk factors in our practice setting were identified, and three recommendations, relating to improving physical status and anaesthetic/analgesic regimen implemented for period 2. The relationship between anaesthetic death and recorded variables were analyzed, and where relevant, compared between periods.ResultsSix thousand two hundred and thirty-one animals underwent general anaesthesia. The overall death rate during period 1 was 1.35% (48 in 3546, 95% CI [1.0–1.7%]) and during period 2 was 0.8% (21 in 2685, 95% CI [0.6–1.2%]). For sick animals (ASA status 3 and over), the overall death rate was 4.8% (45 of 944 95% [CI 3.5–6.4%]) during period 1 and 2.2% (18 of 834 95% CI [1.3–3.5%]) during period 2; this represented a significant decrease in death rate in period 2 (p = 0.002). In period 2, the main factors associated with an increased odds ratio of anaesthetic death were poor health status (ASA physical status classification) and old age. Species, gender, anaesthetic regimen, the nature and urgency of the procedure were not associated with risk.Conclusion and clinical relevanceFollowing evidence based recommendations, the death rate related to anaesthesia was significantly decreased during period 2 compared to period 1. Application of evidence-based medicine may contribute to an effective approach to decrease death rates. Other factors, not monitored in this study, may also have had an impact.     

Propofol as an intravenous anaesthetic agent in dogs

Studies in dogs with an emulsion formulation of the intravenous anaesthetic, propofol, showed that induction of anaesthesia was smooth and it was possible to maintain anaesthesia by intermittent injection. The mean dose for induction of anaesthesia in unpremedicated dogs was 5.95 mg/kg body-weight. When no premedication was administered anaesthesia was maintained by a total dose of approximately 0.806 mg/kg/minute. Premedication with between 0.02 and 0.04 mg/kg of acepromazine reduced the mean induction dose by about 30 per cent and the maintenance dose by more than 50 per cent. In 68 unpremedicated dogs given one dose, recovery was complete in a mean time of 18 minutes and after maintenance of anaesthesia by intermittent injection in 65 dogs the mean recovery time was 22 minutes from administration of the last dose. Premedication with acepromazine did not produce statistically significant increases in these recovery times. The quiet, rapid and complete recovery proved to be most valuable in cases where the animal had to be returned to the owners' care with the minimum of delay.     

Changes in heart rate, mean arterial pressure, blood biochemistry, plasma glucose, plasma lactate and some plasma enzymes during sufentanil/halothane anaesthesia in horses

Nine horses were each anaesthetised for 40 min using SufentaniVhalothane. No surgery was performed. After premedication (detomidine 5 pgkg bwt iv) induction of anaesthesia was achieved by a combination of guaiphenesinlthiopentone. Anaesthesia was maintained by inhalation of halothane (0.8%) in oxygen. Six horses (Group 1) received 1 pgkg bwt sufentanil followed by a second injection (1 pg/kg bwt) after 20 min. Three horses (Group 2) received 2 pg/kg bwt sufentanil also followed by a second injection (2 pg/kg bwt) after 20 min. Each sufentanil injection produced a slight decrease in mean arterial blood pressure with a gradual return to the initial pressure. Bradycardia was also observed. Sufentanil injection induced apnoea needing artificial ventilation. Arterial blood was sampled for analysis during the anaesthetic procedure. At the end of anaesthesia, 1 h and 24 h after rising, venous blood was sampled to determine concentrations of lactate dehydrogenase (LDH), aspartate aminotransferase (AST) and creatine phosphokinase (CPK). Values obtained were compared with values in blood taken before premedication. Plasma glucose and lactate concentrations just before sufentanil administration, at the end of anaesthesia and 1 h after rising were compared to control values. Plasma glucose concentration increased significantly during anaesthesia but returned to normal values 1 h after rising. All other parameters stayed within physiological ranges. In both groups spontaneous respiration returned 20–25 min after the second sufentanil injection. Recovery was uneventful.     

The Stress Responses Involved in General Anaesthesia in Cattle

Anaesthesia was induced in four adult Friesian cows with intravenous thiopentone (10 mg/kg) after either intramuscular saline (2ml), acepromazine (0.05mg/kg) or xylazine pre- medication (0.05 mg/kg). At least 4 weeks was allowed to alapse between each anaesthetic in each cow. The stress involved in induction of and recovery from anaesthesia was assessed by measuring pulse and respiration rates, plasma cortisol and glucose concentrations, total plasma protein concentration and haematocrit at 10–15 minute intervals from 60 min prior to premedication to the time when the animals stood after anaesthesia. Recovery from anaesthesia was associated with an increase in cortisol concentration. This response was significantly attenuated by premedication with xylazine but not acepromazine. Xylazine produced a marked hyperglycaemia in comparison to the other premedicants. Anaesthesia was associated a marked increase in pulse rate and slight increase in haematocrit, but these changes were not markedly affected by the premedication given. Recovery from anaesthesia was deemed to be the most stressful period of short-term general anaesthesia.     

Demographic,preoperative and anaesthesia-related risk factors for unsatisfactory recovery quality in horses undergoing emergency abdominal surgery

ObjectiveTo determine demographic, preoperative and anaesthesia-related variables that may be associated with unsatisfactory recovery quality in horses undergoing emergency abdominal surgery (colic) in an equine teaching hospital.Study designRetrospective case series.AnimalsA total of 313 horses.MethodsThe anaesthetic records of horses admitted for surgical treatment of colic between 2005 and 2018 were examined. Overall quality of recovery was assessed as dangerous, poor, fair, good or excellent. The following categories were constructed as a dichotomic variable: unsatisfactory recovery (poor and dangerous recoveries) and satisfactory recovery (excellent, good and fair recoveries). Univariable and multivariable analyses were performed to evaluate the association between all studied variables and recovery.ResultsAll recoveries were unassisted. Unsatisfactory recovery quality totalled 17.2% (3.5% and 13.7% were dangerous and poor recoveries, respectively), whereas satisfactory recoveries totalled 82.8% (26.2%, 40.9% and 15.7% were fair, good and excellent recoveries, respectively). Univariable analysis showed that unsatisfactory recoveries were associated with high preoperative packed cell volume, pain behaviour, poor premedication and induction quality, high intraoperative mean heart rate, low mean arterial blood pressure, dobutamine dose ≥1.5 μg kg^–1 minute^–1, non-administration of romifidine, long anaesthesia time and prolonged time to stand. The multivariable model showed that factors strongly associated with unsatisfactory recovery quality were dobutamine dose ≥1.5 μg kg^–1 minute^–1 [adjusted odds ratio (AOR) = 6.60; 95% confidence interval (CI), 2.91–14.96], poor premedication quality (AOR=4.60; 95% CI, 1.73–12.23) and a time to stand > 70 minutes (AOR=2.59; 95% CI, 1.13–5.91).Conclusions and clinical relevanceOur study shows that high dobutamine requirements, poor premedication quality and a prolonged time to stand are risk factors for unsatisfactory recovery quality in horses undergoing anaesthesia for colic surgery. Addressing these factors may enable clinicians to improve the quality of recovery phase.     

Analysis of the frequency spectrum of the equine electroencephalogram during halothane anaesthesia

The electroencephalogram (EEG) has been used in human clinical anaesthesia as an indicator of cortical activity and as an indicator of the depth of anaesthesia. It would be useful if it provided a reliable indication of the depth of anaesthesia of horses. In this study anaesthesia was induced with thiopentone and maintained with halothane in nine ponies. The end tidal halothane concentration (P_E-Hal) was monitored and 20 seconds of EEG were recorded at 0·8 per cent, 1·0 per cent and 1·2 per cent halothane, equivalent to the minimum alveolar concentration (mac), 1·25 mac and 1.5 mac. Each 20 second block of data was divided into one second segments and averaged to give one second of averaged EEG from which a frequency spectrum was obtained by using a fast Fourier transformation. The power of the waveform at low frequency (1 to 3 Hz) was compared with that at higher frequency (9 to 11 Hz). The median frequency and 95th percentile (spectral edge) were also calculated. The spectral edge frequency had the best correlation with P_E-Hal     

Respiratory and cardiac arrest under general anaesthesia: treatment by acupuncture of the nasal philtrum

The philtrum point VG 26 (Jen Chung) was needled in 69 cases of respiratory depression or apnoea in dogs and cats during induction or maintenance of general anaesthesia. Respiration was restored to normal or near normal rates within 10 to 30 seconds of insertion of the needle in all the cases. In seven cases of anaesthetic apnoea with concurrent cardiac arrest and absence of vital signs, the revival rate was 43 per cent. Those which recovered required four to 10 minutes of acupuncture stimulation. In eight cases of collapse due to other causes, the revival rate was 25 per cent. The cases included five sheep in shock following liver biopsy, two cases of haemorrhagic shock (dog, cat) and one terminal collapse in chronic congestive heart failure (dog).     

Target-controlled infusion of propofol in dogs--evaluation of four targets for induction of anaesthesia

Four groups of 20 dogs were anaesthetised by means of target-controlled infusions of propofol designed to achieve 2.5 microg/ml, 3.0 microg/ml, 3.5 microg/ml or 4.0 microg/ml of propofol in blood. The dogs' pulse rate and respiratory rate were recorded before premedication and induction, immediately after endotracheal intubation and three and five minutes later (times 0, 3 and 5, respectively), and their arterial blood pressure was recorded oscillometrically just before induction and at times 0, 3 and 5. The targets of 2.5, 3.0, 3.5 and 4.0 microg/ml resulted in the successful induction of anaesthesia in 13 (65 per cent), 16 (80 per cent), 20 (100 per cent) and 20 (100 per cent) of the dogs, respectively. The incidence of postinduction apnoea was 0 (0 per cent), one (5 per cent), two (10 per cent) and eight (40 per cent) at time 5 for groups 2.5, 3.0, 3.5 and 4.0 mug/ml, respectively, and its incidence at time 5 was significantly higher in the 4.0 microg/ml group (P<0.05) than in the other groups. In all the groups there was a significant (P<0.05) decrease in blood pressure between just before induction and the later measurements. Although there were no statistically significant differences between the groups in terms of inducing anaesthesia at a specific target, a target of 3.5 microg/ml appears to ensure a successful induction of anaesthesia without a significant increase in the incidence of apnoea.     

Cardiopulmonary effects of three different anaesthesia protocols in cats.

To develop an alternative anaesthetic regimen for cats with cardiomyopathy, the cardiopulmonary effects of three different premedication-induction protocols, followed by one hour maintenance with isoflurane in oxygen: air were evaluated in six cats. Group I: acepromazine (10 microg/kg) + buprenorphine (10 microg/kg) IM, etomidate (1-2 mg/kg) IV induction. Group II: midazolam (1 mg/kg) + ketamine (10 mg/kg) IM induction. Group III: medetomidine (1.5 mg/m2 body surface) IM, propofol (1-2 mg/kg) IV induction. Heart rate, arterial blood pressure, arterial blood gases, respiration rate, and temperature were recorded for the duration of the experiment. In group I the sedative effect after premedication was limited. In the other groups the level of sedation was sufficient. In all groups premedication resulted in a reduced blood pressure which decreased further immediately following induction. The reduction in mean arterial pressure (MAP) reached statistical significance in group I (142+/-22 to 81+/-14 mmHg) and group II (153+/-28 to 98+/-20 mmHg) but not in group III (165+/-24 to 134+/-29 mmHg). Despite the decrease in blood pressure, MAP was judged to have remained within an acceptable range in all groups. During maintenance of anaesthesia, heart rate decreased significantly in group III (from 165+/-24 to 125+/-10 b.p.m. at t=80 min). During anaesthesia the PCO2 and PO2 values increased significantly in all groups. On the basis of the results, the combination acepromazine-buprenorphine is preferred because heart rate, MAP, and respiration are acceptable, it has a limited sedative effect but recovery is smooth.