Читать книгу Complications in Equine Surgery - Группа авторов - Страница 239

Sedation and ataxia following epidural administration of different drugs is common in the horse, especially following alpha‐2 adrenergic agonist drugs, due to their systemic absorption and central nervous system effects [72]. Detomidine causes more systemic effects (sedation, head drop, ataxia) than xylazine when administered epidurally, due to its increased lipophilicity and systemic absorption [73]. There are several studies reporting ataxia following epidural administration of alpha‐2 adrenergic agonists in horses, especially detomidine [74]. Recumbency has been reported following the administration of 50 microg/kg epidural detomidine in a horse [75].

Local anesthetic drugs cause non‐specific blockade of nerve transmission, therefore causing motor as well as sensory blockade. Ataxia of the hind limbs and potentially recumbency may occur when high doses of a local anesthetic are administered into the sacrococcygeal or intercoccygeal epidural space due to excessive cranial migration (blockade of the caudal lumbar and cranial sacral spinal roots) [76].

Epidural ketamine can also cause ataxia, although this is usually mild [77].

Epidurally‐administered opioid drugs (e.g. morphine, methadone, etc.) do not produce motor blockade and therefore do not cause ataxia [78].

Some cases of ataxia/recumbency may be related to a local compressive effect from the injected volume of solution, and not to the spinal effects of the drug, due to fast administration of a high volume [79]. A total epidural volume of 20 mL administered at a rate of 1 mL every 10 seconds was painful in a study in horses, and the authors concluded that this was possibly due to compression of sacral and lumbar spinal roots [78].