Adverse Reactions in Horses that Underwent General Anesthesia and Cervical Myelography

Abstract

BackgroundThe study was prompted by a perceived high prevalence of myelographic complications varying in severity and type, and attributed to the contrast material or the procedure.Hypotheses1. Any adverse reaction (AAR) is associated with a change in CSF volume induced either by removal of CSF or addition of contrast material. 2. AAR occurs more frequently in horses with higher premyelography neurologic grade. 3. Nonspecific hyperthermia is attenuated by anti‐inflammatory and osmotic agents.AnimalsHorses (n = 278) that underwent myelography between 2000 and 2012 at 5 institutions: A (87), B (68), C (65), D (46), and E (12).MethodsMulti‐institutional, retrospective, observational cross‐sectional study.Results AAR were observed in 95/278 (34%) horses, were associated with longer general anesthesia time (P = .04) and higher contrast‐medium volume (P = .04); euthanasia because of AAR was performed in 5/278 (2%) horses. Adverse neurologic reactions were the most common type of complication observed occurring in 15/278 (5%) and 42/235 (18%) of horses in the intra‐ and postmyelography periods. A relationship between AAR and premyelography neurologic grade was not identified (P = .31). Nonspecific hyperthermia was observed in 25/235 (11%) horses; no relationship was observed with administration of anti‐inflammatory drugs and osmotic agents (P = .30).Conclusions and clinical importanceThe category of AAR occurred in one‐third of the horses generally was mild and self‐limiting. These reactions were associated with increased contrast‐medium volume and longer anesthesia time; but, no specific procedural recommendations could be made because of small odds ratios (OR) of <2 for each 1 mL increase in contrast material and for each 1 minute of additional anesthesia time.

Use of contrast media in computed tomography and magnetic resonance imaging in horses: Techniques, adverse events and opportunities

“…Self-limiting hypertension in horses is likely due to peripheral vasoconstriction and systemic pain responses [143], while in man, tachycardia develops with hypotension due to intravascular fluid shifts and is usually classified as at least a moderate [144]. Although considered rare in horses, severe adverse events can be fatal [142,145].…”

“…In man, severe events are typically allergic-like with ionic ICM, while cardiopulmonary with nonionic ICM [136]. Severe adverse events in horses include anaphylactoid reactions, seizure, hypo/hypertension and bronchospasm [139][140][141][142]. Self-limiting hypertension in horses is likely due to peripheral vasoconstriction and systemic pain responses [143], while in man, tachycardia develops with hypotension due to intravascular fluid shifts and is usually classified as at least a moderate [144].…”

“…Delayed adverse events: In one equine study, nonspecific hyperthermia occurred in 25/92 (27%) cases which self-resolved without treatment [142].…”

“…Another study using ionic ICM revealed 4/97 (4%) horses developed cutaneous signs (urticaria or facial oedema) that all self-resolved [143]. In man, the lack of follow-up in outpatient procedures likely underestimates true prevalence of delayed adverse events [8,137,146,147] and this is equally probable in equine studies [142]. Although usually self-limiting in horses, anti-inflammatory, or anti-histamine treatments may be beneficial.…”

“…Similar changes occur with iopamidol and both are less damaging than metrizamide [145,[175][176][177][178][179][180][181] analogous to other species [182][183][184][185]. Despite the lack of reports confirming use of 350 mg I/mL to be detrimental, most equine clinicians still adhere to human guidelines [104,142,186,187].…”