The effect of anesthetic drug choice on accuracy of high-definition oscillometry in laterally recumbent horses.

The research paper analyzes how anesthetic drug choice can impact the accuracy of high-definition oscillometry (HDO), a technique for measuring arterial pressure, in horses that are lying on their side (lateral recumbency). The two anesthetics compared are a combination of xylazine-ketamine-guaifenesin, or TripleDrip (TD), and isoflurane (ISO). The results show that the type of anesthesia doesn’t greatly affect the performance of HDO, but it was noticed that there was more variability with TD compared to ISO.

Methods

• The study involved 24 horses which received anesthesia for procedures that necessitated lateral recumbency.
• The horses were premedicated with xylazine before being induced into anesthesia with diazepam-ketamine.
• Anesthesia was then maintained either through TripleDrip (TD; 12 horses) or isoflurane (ISO; 12 horses).
• A high-definition oscillometry (HDO) device was used to take systolic (SAP), mean (MAP), and diastolic (DAP) arterial pressures, as well as heart rate (HR).
• The measurements were collected using an 8-cm-wide cuff placed around the horse’s tail.
• During the HDO cycling, invasive blood pressure (IBP) levels were recorded, as were SAP, MAP, DAP, and HR.

Results

• The study collected over 110 paired samples for each variable.
• The type of anesthesia did not greatly affect the performance of the HDO although more variability was witnessed in the TD as compared to the ISO.
• Bland-Altman analysis, a statistical method used for comparing two different measurements, demonstrated that HDO tends to overestimate the SAP, MAP, and DAP, suggesting some degree of inaccuracy.
• The degree of accuracy for HDO in TD cases was relatively lower, with 26-40% of HDO measurements being within 10 mmHg of the IBP, as compared to 60-74% in ISO.
• Despite these differences, the statistical analysis showed that there was no significant difference in the numerical gaps between IBP and HDO measurements, regardless of whether TD or ISO was used for anesthesia.
• The study also found that increasing the cuff width:tail girth ratio up to 40% reduces the numerical difference between the IBP and HDO measurements for SAP, MAP, and DAP. This indicates an increased accuracy for HDO.

Conclusions

• The anesthetic choice doesn’t have a considerable effect on the performance of HDO, however, more data variance is present in TD than ISO.
• While HDO tends to overestimate arterial pressure measurements, this inaccuracy can be minimized by optimizing the cuff width:tail girth ratio.
• The study concludes that the correct choice of cuff size, in relation to the girth of the tail, is vital for the accuracy of HDO in measuring arterial pressure in horses.