Validity and reliability of Doppler ultrasonography and direct arterial blood pressure measurements in anaesthetized dogs weighing less than 5 kg

Objective

To assess the validity and reliability of Doppler ultrasonography (DOP) as compared with invasive arterial blood pressure measurements in anaesthetized dogs weighing less than 5 kg.

Study design

Controlled, prospective, clinical study.

Animals

A total of 41 privately owned dogs weighing less than 5 kg.

Methods

The dogs were anaesthetized, and an intra-arterial catheter was placed aseptically in the dorsal pedal artery of the pelvic limb to perform invasive blood pressure (IBP) measurement. The contralateral metatarsal surface of the foot was clipped in order to perform DOP. Both techniques were used to record blood pressure measurements every 5 minutes during surgical procedures. The blood pressure measurements were categorized into two groups: hypotensive [mean arterial pressure (MAP) < 60 mmHg] and normotensive (MAP between 60 and 120 mmHg). A linear mixed model was used to compare the DOP and IBP values. The results were evaluated according to the requirements of the American College of Veterinary Internal Medicine (ACVIM) guidelines for the validation of devices.

Results

DOP provided higher values compared to the systolic arterial blood pressure (SAP) and MAP of IBP measurements. The closest agreement between the two techniques was found for SAP; the bias was 8.8, and limits of agreement (LOA) were –32.9 and 50.4. Similar results were observed when the IBP technique was categorized. The closest agreement was for SAP in animals categorized as normotensive; the bias was 8.2, and LOAs were –32.8 and 49.2. The level of agreement between DOP and IBP did not meet the ACVIM recommendations.

Conclusions and clinical relevance

Our results suggest there is poor agreement between DOP and IBP measurements in anaesthetized dogs weighing less than 5 kg. Hence, the use of DOP in these animals could be misleading.