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

Abstract

Background: Few 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. Methods: Ten 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. Results: Thoracic 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.Conclusions: Spinal 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.

Impact of high-dose vasopressor during endotoxic shock on the cerebral, lingual, hepatic, and renal microcirculation evaluated by near-infrared spectroscopy in swine

“…In the liver, the TOI was pressure dependent over a wide MAP range, whereas, in the tongue, it was independent of blood pressure over a wide MAP range. These findings were consistent with those of our previous reports (11–13), indicating that the brain, tongue (muscle), and kidney are well autoregulated, whereas liver autoregulation is weak.…”

Mechanism of Increased Spinal Cord Blood Flow due to Noradrenaline Administration Using Vascular Resistance: An Experimental Study Using a Canine Model

“…In previous animal experiments, we have also observed that noradrenaline administration caused both SCBF and SCPP to increase in extensive SA clamping and non-clamping models [ 9 ]. In an experimental study by Kurita et al using near-infrared spectroscopy as a method of evaluating spinal cord circulation in order to assess the balance of oxygen supply and demand in the spinal cord, the use of an α-adrenoreceptor agonist was seen to increase O 2 delivery to the spinal cord [ 20 ]. Noradrenaline has thus been experimentally demonstrated to improve spinal cord circulation from the perspectives of both SCBF and O 2 delivery.…”

Near-infrared spectroscopy to monitor spinal cord oxygenation in οpen thoraco-abdominal aortic surgery. A case series

“…Depending on several vascular and metabolic factors, a safe pressure level does not always ensure an adequate flow. Indeed, in animal models, spinal cord autoregulation is less robust than cerebral autoregulation and more pressure-dependent, hence SC is more sensitive to hypotension 16 . Noteworthy, Vanpeteghem et al, found different effects of phenylephrine and ephedrine on cerebral oxygen saturation and paraspinal oxygen saturation.…”