Cardiorespiratory findings during iohexol contrast myelography in horses under total intravenous anaesthesia

Abstract

SummaryBackgroundIohexol myelography is used to investigate cervical vertebral pathology in horses but the cardiorespiratory changes during the procedure under total intravenous anaesthesia (TIVA) have not yet been reported.ObjectivesTo analyse heart rate (HR), arterial blood pressure (ABP) and respiratory rate (RR) changes in horses during iohexol contrast myelography under TIVA.Study designRetrospective review of anaesthetic records.MethodsAnaesthetic records from 70 horses undergoing iohexol contrast myelography under TIVA were reviewed. Heart rate, arterial blood pressure and respiratory rate at six time points; baseline (10 min prior to needle insertion), needle insertion, withdrawal of cerebrospinal fluid (CSF), iohexol contrast injection, needle removal and post‐procedure (10 min after needle removal) were analysed. Data were analysed using paired and two‐sample t‐tests, Mann–Whitney U test, Wilcoxon signed rank test, ANOVA, Pearson’s correlation and logistic regression.ResultsForty‐five records contained complete data. Mean HR and ABP were not significantly different from baseline at any time point during the procedure. Overall, median RR was significantly higher during contrast injection (p < 0.001), at needle removal (p < 0.001) and post‐procedure (p < 0.001) compared to baseline. Premedication with acepromazine, romifidine and butorphanol (ARB) was associated with a significantly lower RR at needle removal compared to premedication with romifidine (R), romifidine and butorphanol (RB) or acepromazine and romifidine (AR) (p < 0.05). Premedication with ARB or AR was associated with a lower incidence of tachypnoea (RR >20 breaths/min) at needle removal compared to R and RB (p = 0.005).Main limitationsRetrospective design and small sample size.ConclusionsThere was little fluctuation in HR and ABP during iohexol myelography in healthy horses under TIVA. Tachypnoea occurred during or after subarachnoid iohexol administration in 55% of horses. Acepromazine premedication reduced the incidence of tachypnoea, however, the cause of this respiratory response requires further investigation.