Spinal cord autoregulation using near-infrared spectroscopy under normal, hypovolemic, and post-fluid resuscitation conditions in a swine model: a comparison with cerebral autoregulation

Tadayoshi Kurita,Shingo Kawashima,Yoshiki Nakajima,Koji Morita

doi:10.1186/s40560-020-00443-6

Tadayoshi Kurita, Shingo Kawashima + Show 2 more

Open Access

https://doi.org/10.1186/s40560-020-00443-6

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Abstract

BackgroundFew studies have investigated spinal cord autoregulation using near-infrared spectroscopy (NIRS). Here, we assessed spinal cord autoregulation under normal, hypovolemic, and post-fluid resuscitation conditions compared with cerebral autoregulation.MethodsTen pigs (36.1 ± 1.1 kg) were anesthetized with 2.5% isoflurane, before phenylephrine administration at 0.5, 1, 2, and 5 μg kg−1 min−1 in a stepwise fashion at 10-min intervals (baseline), followed by similar administration of sodium nitroprusside (SNP). Hypovolemia was induced by a 600-ml bleed (25% estimated total blood volume). Only phenylephrine was readministered (same protocol). Hypovolemia was reversed by infusing 600 ml hydroxyethyl starch, before readministering phenylephrine and SNP. The relationships between mean arterial pressure (MAP) and cerebral, thoracic, and lumbar spinal cord tissue oxygenation indices (TOIs) were evaluated.ResultsThoracic and lumbar spinal cord TOIs were approximately 15% and 10% lower, respectively, than the cerebral TOI at similar MAPs. The average relationship between MAP and each TOI showed an autoregulatory pattern, but negative correlations were observed in the cerebral TOI during phenylephrine infusion. A 600-ml bleed lowered each relationship < 5% and subsequent fluid resuscitation did not change the relationship. Individual oxygenation responses to blood pressure indicated that the spinal cord is more pressure-passive than the cerebrum. Paradoxical responses (an inverse relationship of tissue oxygenation to MAP) were observed particularly in cerebrum during phenylephrine infusion and were rare in the spinal cord.ConclusionsSpinal cord autoregulation is less robust than cerebral autoregulation and more pressure-dependent. Similar to cerebral oxygenation, spinal cord oxygenation is volume-tolerant but is more sensitive to hypotension.

Highlights

Few studies have investigated spinal cord autoregulation using near-infrared spectroscopy (NIRS)
Because the data for the lumbar spinal cord Tissue oxygenation index (TOI) were lost from one pig, the lumbar spinal cord results were evaluated from nine animals
The thoracic spinal cord TOI significantly increased under the baseline condition (3%, P = 0.0051 vs. pre-infusion), and the thoracic and lumbar spinal cord TOIs increased during the hypovolemic condition (10%, P < 0.0001; and 11%, P = 0.0003 vs. pre-infusion, respectively) during phenylephrine infusions

Summary

Introduction

Few studies have investigated spinal cord autoregulation using near-infrared spectroscopy (NIRS). Cerebral autoregulation was evaluated using nearinfrared spectroscopy (NIRS) in several studies [4,5,6,7,8,9], which treated cerebral oxygenation as a surrogate indicator of cerebral blood flow. Clinical guidelines recommend elevating mean arterial pressure (MAP) to increase spinal cord perfusion in patients with acute spinal cord injury. They recommend increasing MAP to 85–90 mmHg using vasopressors and/or intravenous fluids to protect the spinal cord and improve the neurological outcome [20]. There have been few studies investigating the impact of blood pressure alterations and/or circulatory blood volume changes on spinal cord oxygenation

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