Mortality and morbidity in equine anaesthesia

Abstract

Equine peri-anaesthetic mortality and morbidity are of interest to anaesthetists, practitioners, horse owners and insurance companies. The largest prospective study, 'The Confidential Enquiry into Perioperative Equine Fatalities' (CEPEF) was conducted more than 20 years ago. It included over 40,000 horses from multiple centres and reported mortality to be 1.9% that decreased to 0.9% when only elective cases were considered. This is in stark contrast to mortality rates in small animal (dogs: 0.17%, cats: 0.24%) and human anaesthesia (0.04-7/10,000). In spite of developments in understanding the pathophysiology of equine anaesthesia mortality has not decreased in the intervening years. The main contributors to peri-anaesthetic equine mortality are cardiac arrest, fractures and myopathy or neuropathy. Spinal cord myelopathy and cerebral necrosis are less common. Malignant hyperthermia and hyperkalaemic periodic paralysis are diseases associated with genetic mutations that can be triggered during general anaesthesia and may be fatal if not recognised and treated immediately. Morbidities are reported less frequently, presumably because often they do not cause permanent harm and may resolve within a short period of time. Complications in equine anaesthesia are numerous and include injuries at induction and recovery, damage to the airway associated with orotracheal or nasotracheal intubation, post-anaesthetic myopathy or neuropathy, regurgitation and aspiration of stomach contents, ocular injuries and complications associated with intravascular cannulation. Hypotension, hypoventilation, hypoxaemia, hypothermia and dysrhythmias may occur both during the maintenance phase of anaesthesia but also in recovery. Airway obstruction during recovery has repeatedly been reported over the years as causing pulmonary oedema, which is often fatal if the airway is not restored extremely quickly. This review summarises the literature on the risk of mortality and morbidity. Information has been gathered from single case reports as well as larger research studies.

Post‐anaesthetic spinal cord myelomalacia in horses: A review and a presumptive clinical case presentation

“…Post‐anaesthetic spinal cord myelomalacia needs to be differentiated from post‐anaesthetic myopathies and/or neuropathies, and fractures (Joubert et al, 2005; Küls & Rocchi, 2017; Ragle et al, 2011). Post‐anaesthetic myopathies are associated with decreased muscle perfusion related to hypotension, prolonged anaesthetic duration, lateral recumbency and larger body mass (Deutsch & Taylor, 2021). Raised muscle enzyme levels and the presence of myoglobinuria might develop and could be used to support the diagnosis of post‐anaesthetic myopathies (Grandy et al, 1987; Trim, 1997).…”

“…Raised muscle enzyme levels and the presence of myoglobinuria might develop and could be used to support the diagnosis of post‐anaesthetic myopathies (Grandy et al, 1987; Trim, 1997). Furthermore, in the presence of a post‐anaesthetic myopathy, the affected muscle(s) might be painful, firm and swollen on palpation (Deutsch & Taylor, 2021; Young, 2005). A horse with a bilateral femoral nerve paralysis may show pelvic limb motor deficits similar to a horse with PSCM (Küls & Rocchi, 2017).…”

Recovery after General Anaesthesia in Adult Horses: A Structured Summary of the Literature

“…Avoiding complications [9] (4) Recovery of horses from anesthesia [10] Postanaesthetic myopathy (5) Equine postanesthetic myopathy-An update [16] Pulmonary function GA (6) Pulmonary function in the horse during anaesthesia: A review [17] Upper airway during recovery (7) Post-anaesthetic pulmonary oedema in horses: A review [7] (8) Mitigating the risk of airway obstruction during recovery from anaesthesia: The way is far from clear [18] Complications during GA (9) Complications in equine anesthesia [19] (10) Equine anaesthesia-associated mortality: where are we now? [2] (11) Anaesthesia-related complications in horses-results of the last few years [20] (12) Editorial: Anesthetic risk and complications in veterinary medicine [21] (13) Mortality and morbidity in equine anaesthesia [22] Complications during GA in the clinically ill horse (14) Anesthesia in horses with colic syndrome: Analysis of 48 cases and literature review [23] (15) Anesthesia of the critically ill equine patient [24] (16) Incisional infections associated with ventral midline celiotomy in horses [25] Complications during GA in orthopaedics (17) Anesthetic management and recovery of large orthopedic patients [26] (18) Fracture fixation in horses: Recent developments in implants, management and recovery-A rewiew [27] (19) Bog spavin: Recognising the problem is the first step towards recovery [28] Complications during GA in late-term mares (20) Anesthesia and sedation for late-term mares [29] Effects of α 2 -agonists (21) Pre-anesthetic medication in the horse part IV. Sedative-hypnotics and drug mixtures [30] (22) The responses to the use of detomidine (Domosedan) in the horse [31] (23) Use of the alpha-2 agonists xylazine and detomidine in the perianaesthetic period in the horse [32] (24) Is there a place for dexmedetomidine in equine anaesthesia and analgesia?…”

“…Four reviews focused on specific complications during recovery such as post-anaesthetic myopathy (PAM) [16] and respiratory tract problems [7,17,18]. Eleven publications described the complications of all the phases of general anaesthesia, focussing on the recovery in general [2,[19][20][21][22] and in particular cases such as sick patients [23][24][25], orthopaedics [26][27][28] and pregnant mares [29]. The other 21 narrative reviews/expert opinions focussed on the effects of different drugs in anaesthesia with references to the recovery phase .…”

Benefits of equine thoracoscopy

“…When dorsal or lateral recumbency is utilised for thoracoscopy, general anaesthesia is required. In the horse, general anaesthesia has increased the risk of complications including myopathy, post‐anaesthetic ileus and associated risks of recovery (Deustch & Taylor, 2022). In addition, when under general anaesthesia, insufflation with carbon dioxide is required as bilateral pneumothorax is more likely to occur (Doherty, et al, 2022).…”