Key result
Ultrasound Doppler and NIRS detected similar changes in limb hemodynamics and drug potency in response to intra-arterial vasoconstrictors, with the strongest correlations observed for drugs targeting the distal microcirculation.
Why the study?
Are ultrasound Doppler and near-infrared spectroscopy equally capable of tracking pharmacologically induced changes in peripheral hemodynamics?
Are ultrasound Doppler and near-infrared spectroscopy equally capable of tracking pharmacologically induced changes in peripheral hemodynamics?
Ultrasound Doppler and NIRS are both capable of tracking pharmacologically induced changes in peripheral hemodynamics, but their correlation depends on the specific receptor landscape targeted by the agonist.
Answers are grounded in this paper and cite their sources.
May not yet inform method selection for peripheral monitoring; leaves open comparative utility of Doppler vs NIRS in patients.
Ultrasound Doppler and near-infrared spectroscopy (NIRS) are routinely used for noninvasive monitoring of peripheral hemodynamics in both clinical and experimental settings. However, the comparative ability of these methodologies to detect changes in microvascular and whole limb hemodynamics during pharmacological manipulation of vascular smooth muscle receptors located at varied locations within the arterial tree is unknown. Thus, in 10 healthy subjects (25 ± 2 yr), changes in resting leg blood flow (ultrasound Doppler; femoral artery) and muscle oxygenation (oxyhemoglobin + oxymyoglobin; vastus lateralis) were simultaneously evaluated in response to intra-arterial infusions of phenylephrine (PE, 0.025-0.8 μg·kg(-1)·min(-1)), BHT-933 (2.5-40 μg·kg(-1)·min(-1)), and angiotensin II (ANG II, 0.5-8 ng·kg(-1)·min(-1)). All drugs elicited significant dose-dependent reductions in leg blood flow and oxyhemoglobin + oxymyoglobin. Significant relationships were found between ultrasound Doppler and NIRS changes across doses of PE (r(2) = 0.37 ± 0.08), BHT-933 (r(2) = 0.74 ± 0.06), and ANG II (r(2) = 0.68 ± 0.13), with the strongest relationships evident with agonists for receptors located preferentially "downstream" in the leg microcirculation (BHT-933 and ANG II). Analyses of drug potency revealed similar EC50 between ultrasound Doppler and NIRS measurements for PE (0.06 ± 0.02 vs. 0.10 ± 0.01), BHT-933 (5.0 ± 0.9 vs. 4.5 ± 1.3), and ANG II (1.4 ± 0.8 vs. 1.3 ± 0.3). These data provide evidence that both ultrasound Doppler and NIRS track pharmacologically induced changes in peripheral hemodynamics and are equally capable of determining drug potency. However, considerable disparity was observed between agonist infusions targeting different levels of the arterial tree, suggesting that receptor landscape is an important consideration for proper interpretation of hemodynamic monitoring with these methodologies.
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Ives et al. (2014) studied Healthy (n=10). Intra-arterial infusions of phenylephrine, BHT-933, and angiotensin II was evaluated on Relationship between ultrasound Doppler and NIRS changes across doses of pharmacological agonists (r2 = 0.37 ± 0.08 for PE, r2 = 0.74 ± 0.06 for BHT-933, r2 = 0.68 ± 0.13 for ANG II, p=<0.05). Ultrasound Doppler and NIRS detected similar changes in limb hemodynamics and drug potency in response to intra-arterial vasoconstrictors, with the strongest correlations observed for drugs targeting the distal microcirculation.
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