Environmental sustainability in veterinary anaesthesia.

OBJECTIVE: Attention is drawn to the potential of global warming to influence the health and wellbeing of the human race. There is increasing public and governmental pressure on healthcare organisations to mitigate and adapt to the climate changes that are occurring. The science of anaesthetic agents such as nitrous oxide and the halogenated anaesthetic agents such as greenhouse gases and ozone-depleting agents is discussed and quantified. Additional environmental impacts of healthcare systems are explored. The role of noninhalational anaesthetic pharmaceuticals is discussed, including the environmental life-cycle analyses of their manufacture, transport, disposal and use. The significant role of anaesthetists in recycling and waste management, resource use (particularly plastics, water and energy) and engagement in sustainability are discussed. Finally, future directions for sustainability in veterinary anaesthesia are proposed. CONCLUSIONS: Veterinary anaesthetists have a considerable opportunity to drive sustainability within their organisations through modification of their practice, research and education. The principles of sustainability may help veterinary anaesthetists to mitigate and adapt to our environmental crisis. Due to their particular impact as greenhouse gases, anaesthetic agents should be used conservatively with the lowest safe fresh gas flow possible. Technologies for reprocessing anaesthetic agents are described.

Reversal of neuromuscular block in companion animals.

OBJECTIVE: To review the evidence regarding the reversal of neuromuscular block (NMB) in companion animals with emphasis on the development and use of newer agents. DATABASE USED: Data sources include scientific reviews and original research publications in both human and veterinary literature using Pubmed and Scopus as search data bases. Unpublished and locally published data on reversal of NMB are presented. CONCLUSIONS: Residual NMB has been shown to increase morbidity and mortality in humans and needs to be avoided. It can be detected only by adequate neuromuscular monitoring. The proper use of reversal agents avoids residual NMB and recurarization should not occur. Anticholinesterase inhibitors, such as edrophonium and neostigmine have been used to reverse NMB when the need for this has been established. Reversal is influenced by several factors and a number of undesirable side- effects of these drugs have been reported. Sugammadex, a γ-cyclodextrin, which was designed specifically to encapsulate rocuronium, is more rapid in its actions, has fewer side effects and can reverse profound NMB induced by aminosteroidal muscle relaxants.

Acid-base and electrolyte balance following administration of three crystalloid solutions in dogs undergoing elective orthopaedic surgery.

OBJECTIVE: To compare acid-base balance and incidence of hyperchloraemic metabolic acidosis following administration of three crystalloid solutions to dogs undergoing anaesthesia for orthopaedic surgery. STUDY DESIGN: Prospective, randomised, clinical study. ANIMALS: Sixty dogs. METHODS: During a non-standardised anaesthetic, 0.9% saline (S), Hartmann's solution (H) or a polyionic glucose-free maintenance solution (M) was administered IV at 10 mL kg(-1)  hour(-1) . Venous blood pH, PCO2 , PCV, total protein, urea, sodium, potassium and chloride concentrations were measured at induction of anaesthesia (T0) and after 2 hours of fluid therapy (T2). Base excess (BE), bicarbonate, corrected chloride concentration (corrCl), osmolality, change in plasma volume (PV) and strong ion gap (SIG) were calculated. Changes in variables within groups (1-sample Student's t-test/Wilcoxon signed rank test) and between groups (1-way anova/Kruskal-Wallis) were assessed. Data are presented as median (interquartile range). Significance was set at p < 0.05. RESULTS: No significant differences existed between groups for pH, PCO2 , PCV, total protein, urea, potassium, corrCl, PV and SIG. Potassium significantly increased in all groups. Significant differences existed between groups S and M for BE, sodium, chloride, bicarbonate and osmolality, and between groups H and M for sodium and osmolality. Chloride concentration significantly changed from 116 (114-117) to 117 (116-119) mmol L(-1) in group S, 116 (115-118) to 115 (113-117) mmol L(-1) in group H and 116 (115-118) to 114 (113-118)  mmol L(-1) in group M. In groups H and M, sodium and osmolality decreased, and BE and bicarbonate concentration increased significantly. Plasma volume increased by 28 (14-44)%, 25 (5-40)% and 24 (13-33)% in groups S, H and M, respectively. CONCLUSION AND CLINICAL RELEVANCE: Hyperchloraemic metabolic acidosis did not develop after intraoperative 0.9% saline, Hartmann's solution or maintenance solution at 10 mL kg(-1)  hour(-1) for 2 hours in dogs undergoing elective orthopaedic surgery. Bicarbonate and BE increased after Hartmann's and maintenance solutions. Increases in potassium concentration were unexplained.

Use of rocuronium administered by continuous infusion in dogs.

OBJECTIVE: A clinical trial to determine whether continuous infusion administration technique was suitable for maintaining neuromuscular blockade with rocuronium bromide in dogs. ANIMALS: Twenty-two dogs, 10 males and 12 females, median age 2 years 4 months, median weight 32 kg undergoing elective surgical procedures under general anaesthesia: ASA classification I or II. MATERIALS AND METHODS: After induction of anaesthesia, neuromuscular function was evaluated using train-of-four (TOF) stimulation of the dorsal buccal branch of the facial nerve. A bolus dose of 0.5 mg kg(-1) rocuronium was administered intravenously and an infusion of 0.2 mg kg(-1) hour(-1) was started immediately. Neuromuscular blockade was assessed visually by counting the number of twitches observed during TOF stimulation repeated at 10-second intervals. RESULTS: The bolus dose of rocuronium abolished the response to TOF stimulation in 21 of the 22 dogs. The median onset time of neuromuscular blockade (complete loss of all four twitches) was 82 seconds (range 38-184 seconds). Median infusion duration was 76 minutes (range 20.3-146 minutes). CONCLUSIONS AND CLINICAL RELEVANCE: This protocol of rocuronium administration was considered to be effective in dogs. Constant infusion of rocuronium is easily applicable to clinical practice and further work is required on infusion titration.

A comparison of extradural and intravenous methadone on intraoperative isoflurane and postoperative analgesia requirements in dogs.

OBJECTIVE: To compare the effects of intravenous (IV) and extradural (ED) methadone on end-tidal isoflurane concentration (Fe'ISO) and postoperative analgesic requirements in dogs undergoing femoro-tibial joint surgery. STUDY DESIGN: Randomized, blinded, clinical study. Animals Twenty-four healthy client-owned dogs undergoing surgical repair of ruptured cruciate ligaments. METHODS: Dogs were randomly assigned to two groups of 12 animals and received either ED or IV methadone (0.3 mg kg(-1) diluted with saline to 0.2 mL kg(-1)). Pre-anaesthetic medication was IV acepromazine (0.05 mg kg(-1)). Anaesthesia was induced with propofol and maintained initially with an Fe'ISO of 1.0% delivered in oxygen. Methadone was injected with the dogs in sternal recumbency; the observer was unaware of the administration route. At 10 minutes (stimulation 1) and 20 minutes (stimulation 2) after methadone administration pelvic limb reflexes were tested by digit-clamping. The time at skin incision (stimulation 3), joint-capsule incision (stimulation 4), tibial tuberosity drilling (stimulation 5), fabellar suturing (stimulation 6) and extracapsular tightening (stimulation 7) were noted. Changes in heart rate (HR) and respiratory rate and arterial blood pressure associated with surgery were recorded along with the corresponding Fe'ISO. After 20 minutes of anaesthesia, Fe'ISO was decreased to the minimum required to maintain stable anaesthesia. Immediately after tracheal extubation, 1, 2, 3 and 6 hours postoperatively and on the morning after surgery, the degree of pain present was assessed using a numerical rating scale. The HR, respiratory rates and blood pressure were also recorded at these times. Serum cortisol and blood glucose concentrations were measured before pre-anaesthetic medication and at each postoperative pain scoring interval except at 1 and 2 hours. Ketoprofen (2 mg kg(-1)), carprofen (4 mg kg(-1)) or meloxicam (0.2 mg kg(-1)) were given by subcutaneous injection whenever pain scoring indicated moderate discomfort was present. RESULTS: Controlled ventilation was required in six dogs which stopped breathing after IV methadone. The median Fe'ISO at stimulus 5 was 1.0% in the IV and 0.83% in the ED group. At stimulus 6, Fe'ISO was 1.0% in the IV and 0.8% in the ED group; the difference was statistically significant (p

cis-Atracurium in dogs with and without porto-systemic shunts.

OBJECTIVE: To evaluate the non-depolarizing neuromuscular blocking drug cis-atracurium in dogs with porto-systemic shunts, and to compare it in clinically normal animals. ANIMALS: Thirteen dogs of mixed breed and sex, aged between 3 and 31 months old, weighing 2.2-25.5 kg, with ASA physical status II-IV, and undergoing surgical attenuation of porto-systemic shunt. A control group of 11 bitches of mixed breed, between 8 and 60 months old, and weighing 4.5-41.0 kg, all ASA physical status I, undergoing routine ovarohysterectomy were also studied. MATERIALS AND METHODS: Pre-anaesthetic medication was an opioid analgesic, given either alone or in combination with acepromazine. Following induction of general anaesthesia with intravenous (IV) propofol and oro-tracheal intubation, anaesthesia was maintained using isoflurane in either oxygen or oxygen and nitrous oxide. Ventilation was controlled. The train of four (TOF) technique was used to monitor neuromuscular blockade. An initial dose of 0.1 mg kg(-1)cis-atracurium was given IV and additional doses of 0.03 mg kg(-1)cis-atracurium were administered when at least one twitch of the TOF was present. RESULTS: Except for one dog that was killed during surgery because its anomaly was inoperable, all animals recovered satisfactorily from anaesthesia and surgery. In dogs with porto-systemic shunt, onset of neuromuscular blockade was 3.1 +/- 1.1 minutes (mean +/- SD) and in control dogs was 3.4 +/- 0.7 minutes (not significantly different). Neuromuscular blockade lasted 34 +/- 13 minutes in dogs with porto-systemic shunt and 29 +/- 17 minutes in control dogs (not significantly different). CONCLUSIONS: The presence of porto-systemic shunt did not affect the rate of onset or duration of action of cis-atracurium. CLINICAL RELEVANCE: cis-Atracurium may have a use in veterinary anaesthesia for producing neuromuscular blockade in dogs with hepatic insufficiency, including those with porto-systemic shunt.

Comparison of two thiopental infusion rates for the induction of anaesthesia in dogs.

OBJECTIVE: To compare the induction dose requirements of thiopental using two different infusion rates for induction of anaesthesia in dogs. STUDY DESIGN: Prospective, randomized study. ANIMALS: Fifty, healthy (ASA I or II) client-owned dogs with a mean age of 4.1 years and a mean mass of 20.4 kg undergoing elective surgery. MATERIALS AND METHODS: Animals were randomly assigned to receive an infusion of 2.5% thiopental at a rate of either 0.1 ml kg(-1) minute(-1) or 0.4 ml kg(-1)minute(-1), 30-40 minutes after pre-anaesthetic medication with intramuscular acepromazine (0.025 mg kg(-1)) and pethidine (3.5 mg kg(-1)). Thiopental administration was controlled by a precision syringe driver. Statistical analyses of the results, using the outcome 'mg kg(-1) required for induction' (log-transformed) included unpaired t-tests for all categorical data (thiopental infusion rate, breed, sex, obesity, sedation quality) and univariable linear regression for continuous variables (mass, age). All variables were then considered in a multivariable linear regression model. The quality of induction with the two different infusion rates was also assessed. RESULTS: After controlling for quality of sedation, the thiopental induction dose requirement was significantly less (p < 0.001) with the slower infusion rate (median = 7.5 mg kg(-1); range 4.9-13.7) compared with the faster infusion rate (median =11.0 mg kg(-1); range 6.6-18.0). The quality of sedation also affected the dose required (p = 0.03). The slower infusion rate was associated with a significantly poorer induction quality (p = 0.03) [corrected] CONCLUSIONS: Slow thiopental infusion (0.1 ml kg(-1) minute(-1)) for anaesthesia induction after acepromazine/pethidine pre-anaesthetic medication reduced the induction dose requirement, although the quality of induction was inferior. CLINICAL RELEVANCE: The induction dose of thiopental was reduced with a slower administration rate and so slow administration is recommended in thiopental-sensitive animals.