What’s new in anaesthesia and analgesia? - Veterinary Practice
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What’s new in anaesthesia and analgesia?

Our monthly summary of the latest academic publications on this month’s spotlight topic of anaesthesia and pain management

Device may improve safety of horses recovering from general anaesthesia

Luis Campoy and others, Cornell University, Ithaca, New York State

Horses have the highest rate of complications following general anaesthesia of any domestic species. This often involves catastrophic orthopaedic injuries that are likely to be career ending. The authors investigated the efficacy of a novel device intended to prevent injuries in horses during recovery from anaesthesia by minimising the risk of a high-energy fall. It consists of a computer-controlled belay system with sensors that detect a fall and instantly apply a corrective force. The system – termed the recovery-enhancing device (RED) – was used in 10 horses undergoing general anaesthesia, and their responses were compared with those in 10 horses undergoing unassisted recovery. Three independent observers assessed the recovery of these horses using a composite grading scale. The scores were found to be significantly better in the RED group. The authors conclude that this device has the potential to reduce the number and severity of injuries to both horses and personnel during the recovery period.

American Journal of Veterinary Research, 85

Dexmedetomidine sedation given subcutaneously via the GV20 acupuncture point

Claire Leriquier and others, University of Montreal, Canada

Dexmedetomidine is an alpha-2-adrenergic receptor agonist used widely as a sedative agent when administered either intravenously or intramuscularly. The authors investigated the quality of sedation achieved when giving the same agent subcutaneously via the Governing Vessel 20 (GV20) acupuncture point in dogs undergoing orthopaedic examinations. Atipamezole, the agent used to reverse sedation with this compound, was later administered at the same acupuncture point, which lies on the dorsal midline of the canine skull. Their findings show that dexmedetomidine and atipamezole administered subcutaneously at the GV20 acupuncture point provided effective sedation and recovery in dogs undergoing radiographic procedures. The level of sedation was similar to that achieved with intravenous administration, and the speed of sedation and recovery was faster than that observed with intramuscular administration.

Journal of Small Animal Practice, 64, 759-768

Treatment of hypotension in anaesthetised dogs maintained with isoflurane

Christopher Quinn, Charles Sturt University, New South Wales

Hypotension is a common and potentially life-threatening complication of general anaesthesia in canine patients. Several options for addressing this issue, such as crystalloid or colloid fluids and pharmacological treatments to increase cardiac output, have been proposed. The author assessed the current evidence on which treatment may be most effective in healthy euvolaemic dogs undergoing general anaesthesia maintained with isoflurane. A reduction in the dose of isoflurane may correct the hypotension, but this approach may not always be feasible. Overall, an infusion of dopamine appears to be the most reliable pharmacological option for consistently increasing blood pressure and cardiac output and correcting hypotension.

Australian Veterinary Journal, 102, 264-273

Seizures in dogs after intravenous anaesthetic drug withdrawal

Kaitlyn Dreese and others, University of Pennsylvania, Philadelphia

Human patients requiring long-term analgesia and sedation for mechanical ventilation can develop tolerance to the drugs used, resulting in a range of abnormal signs termed iatrogenic withdrawal syndrome. The authors encountered similar responses in three puppies around three months of age undergoing long-term mechanical ventilation for suspected non-cardiogenic pulmonary oedema. The three patients received intravenous anaesthesia involving four various agents: dexmedetomidine, fentanyl, midazolam and propofol. Each dog was weaned off the sedatives after five to six days of mechanical ventilation, whereupon they developed seizures. They were treated with an anticonvulsant and were discharged without further incident.

Journal of Veterinary Emergency and Critical Care, 34, 173-178

Lidocaine infusion improves survival in rabbits with gastrointestinal obstructions

Gail Huckins and others, University of Wisconsin-Madison

Gastrointestinal obstruction is a common and potentially fatal condition in rabbits often associated with pellets of compressed hair in the proximal duodenum. Cases present with acute anorexia, absent faecal production, depression, hypothermia, abdominal distension and hypovolaemic shock. The animals may be treated medically or surgically, but the prognosis is likely to be guarded. The authors describe the findings in a retrospective series of 64 events in 56 individual rabbits which received a lidocaine constant rate infusion. Nearly 90 percent of patients that received the lidocaine infusion survived to discharge, compared with 56 percent of rabbits that did not. It was also found that male rabbits receiving systemic lidocaine had a better survival rate than females.

Journal of the American Veterinary Medical Association, 262, 61-67

Comparison of three analgesic agents in cats undergoing ovariohysterectomy

Mariela Goich and others, Andres Bello University, Santiago, Chile

Cats may not always receive adequate perioperative analgesia, largely due to the difficulties in recognising pain in this species and the likelihood that pain-associated behaviour is mistaken for fear or stress. The authors investigated the analgesic efficacy of three opioid agents – tramadol, morphine and methadone – when neutering female cats. Each of the agents provided satisfactory post-operative analgesia for up to six hours; however, intraoperative analgesia was insufficient in most cases. Post-anaesthetic hyperthermia occurred with all three opioids but was seen most frequently in the tramadol group.

Journal of Feline Medicine and Surgery, 26

Association between body mass and hypotension in dogs under general anaesthesia

Lucy Miller and others, University of Edinburgh

Hypotension is the most commonly reported complication of general anaesthesia in dogs. If the mean arterial blood pressure falls below 60mmHg, it is likely to cause inadequate perfusion and may result in organ damage. The authors investigated the influence of body mass on hypotension in this species. They retrospectively examined the records from 1,789 dogs. Their results show that dogs with a body mass below around 5kg were at increased risk of hypotension, along with dogs belonging to brachycephalic breeds. When dogs in those groups undergo general anaesthesia, extra care must be taken to monitor blood pressure, and methods should be readily available to treat hypotension.

Journal of Small Animal Practice, 64, 687-695

Isoflurane reduces hypoxia-induced apoptosis in cultured liver cells

Patricia Obeid and others, Mississippi State University

Studies in human transplant patients have indicated that contact with sevoflurane- and isoflurane-loaded lipid emulsions can exert protective effects in limiting the cellular damage that may result from oxygen deprivation. The authors investigated the effects of the two anaesthetic agents on cultured canine hepatocytes. The cells were treated with emulsified isoflurane or sevoflurane after being exposed to 1 percent oxygen. A day after starting reoxygenation, there was significantly less apoptosis in the treated cells than in those exposed to the lipid alone. This attribute of the two halogenated anaesthetics could provide an alternative treatment for use in live patients submitted for surgical stabilisation of organs and tissues at risk of ischaemia and reperfusion injury.

American Journal of Veterinary Research, 85

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