Agreement between invasive blood pressure measured centrally and peripherally in anaesthetized horses.

This study aimed to examine the accuracy of invasive blood pressure measurements taken from different arteries in anaesthetized horses and assess the effect of two different health conditions on these measurements.

Methodology

• The researchers performed a projected randomized study involving eight horses ranging in age from 4 to 23 years and with an average body weight of 493 ± 33 kg.
• The horses were anaesthetized and positioned on their backs. Invasive blood pressure was then measured simultaneously using catheters placed in the horses’ facial, metatarsal, and carotid arteries.
• Cardiovascular function and the level of agreement between the arteries were assessed before and during the administration of phenylephrine and sodium nitroprusside – medications used to manipulate blood pressure.
• The observed changes were recorded at each sample time, which included measurements of systolic (SAP), mean (MAP), and diastolic (DAP) arterial pressures for each artery, as well as cardiac output (Q˙t) and systemic vascular resistance (SVR).

Results

• Using Bland-Altman analysis, the researchers found the largest difference in systolic arterial pressure recorded in carotid and metatarsal arteries. The mean (bias) of the difference was 2 mmHg, but the range (limits of agreement) was -15 to 19 mmHg.
• The mean arterial pressure recorded in the carotid and facial arteries had a bias of 2 mmHg and a limits of agreement of -4 to 9 mmHg. The comparison of carotid and metatarsal arteries showed a bias of 5 mmHg with a limits of agreement of -4 to 14 mmHg.
• The diastolic arterial pressure showed the closest agreement between the carotid and facial arteries, with a bias of 1 mmHg and a limits of agreement of -3 to 5 mmHg.
• Regression analysis indicated that cardiac output minimally influenced the agreement between the mean arterial pressure (MAPc and MAPf).

Conclusions

• Overall, the researchers found that blood pressure measurements taken from the carotid artery were higher than those taken from the peripheral arteries. This could potentially lead to over-treatment of low blood pressure (hypotension) conditions because central pressures are maintained.
• The difference in measurements between the central and peripheral sites was not largely influenced by systemic vascular resistance and cardiac output.