Effect of Systemic Nitric Oxide Synthase Inhibition on Optic Disc Oxygen Partial Pressure in Normoxia and in Hypercapnia

Petropoulos, Ioannis K.; Pournaras, Jean-Antoine; Stangos, Alexandros Athanasios; Pournaras, Constantin J.

doi:10.1167/iovs.08-2413

Cited by 5 publications

(2 citation statements)

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“…Mechanisms underlying ocular vasodilatory capacity in hypercapnia have been essentially studied in animals. They involve metabolic intermediates such as nitric oxide in the retina, 62 the optic disc, 63 and the brain, 64 prostaglandins, 59,65 and a reduction in intracellular pH in retinal capillary pericytes. 61,66,67 The absence of effect of hypercapnia on ONHBF and ChBF could be related to the species difference regarding tissue-related vasoreactivity (in relationship to the size of vessels), the retinal arterioles being less sensitive to hypercapnia than cerebral arteries, 59,68 and the impact of hypercapnia on the orthosympathic system projecting on the choroid.…”

Section: Bf Response To Hypercapniamentioning

confidence: 99%

Hypoxic, Hypercapnic, and Hyperoxic Responses of the Optic Nerve Head and Subfoveal Choroid Blood Flow in Healthy Humans

Gallice

Zhou

Aptel

et al. 2017

Invest. Ophthalmol. Vis. Sci.

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Citation: Gallice M, Zhou T, Aptel F, et al. Hypoxic, hypercapnic, and hyperoxic responses of the optic nerve head and subfoveal choroid blood flow in healthy humans. Invest Ophthalmol Vis Sci. 2017;58:5460-5467. DOI:10.1167/iovs.17-21855 PURPOSE. To investigate the impact of different gas mixtures (hyperoxia, hypoxia, and hypercapnia) on the optic nerve head (ONH) and choroidal (Ch) hemodynamics.METHODS. Twenty-three healthy subjects (28 6 6 years) took part in the study. Variations in inspired oxygen and carbon dioxide fraction were produced by a gas mixing device. Arterial oxygen saturation (SpO 2 ) was measured continuously using a transcutaneous sensor and endtidal carbon dioxide partial pressure by capnography. The experiment comprised three successive periods: 3-minute baseline (room air breathing), 15-minute gas mixture inhalation (normocapnic hypoxia, hypercapnia, or hyperoxia), and 15-minute recovery (room air breathing). Laser Doppler flowmeter parameters-velocity (VEL), volume (VOL), and flow (BF) of red blood cells-were measured. Two-way ANOVAs were performed for statistical analysis.RESULTS. In response to hyperoxia, ONHBF significantly decreased by À18% 6 6% (P ¼ 0.04) from baseline, due to significant changes in VEL (À12% 6 3% P ¼ 0.0002). During hypoxia at 85% SpO 2, ONH VEL increased by þ12% 6 3% (P ¼ 0.0009), whereas VOL and BF did not change significantly. ChBF significantly increased by þ7% 6 2% (P ¼ 0.004) in response to hypoxia, due to significant changes in VEL þ5% 6 2% (P ¼ 0.03). Both Ch and ONHBFs did not vary significantly in response to hypercapnia.CONCLUSIONS. The magnitude of the blood flow response is the most significant during hyperoxia for ONH and hypoxia for ChBF. For ONHBF, a 37% difference between hyperoxia and hypoxia can be useful when vasoreactivity to O 2 will be tested in patients.

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Section: Bf Response To Hypercapniamentioning

confidence: 99%

Hypoxic, Hypercapnic, and Hyperoxic Responses of the Optic Nerve Head and Subfoveal Choroid Blood Flow in Healthy Humans

Gallice

Zhou

Aptel

et al. 2017

Invest. Ophthalmol. Vis. Sci.

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“…As retinal and ONH vessels are not sympathetically innervated, the mechanism that underlies their autoregulation system is the balanced result of myogenic and metabolic components that maintain constant blood flow during changes in PPm (Pournaras et al 2008). Having an animal or human subject breath various mixtures of gases can reveal the role of blood O 2 and CO 2 on the modulation of arterial and capillaries retinal and ONH blood flow regulation (Petropoulos et al 2005(Petropoulos et al , 2009Pournaras et al 2008).…”

Section: Regulation Of Blood Flow In Retina and Optic Nerve Head (Onh)mentioning

confidence: 99%

Vision impairment during cardiac surgery and extracorporeal circulation: current understanding and the need for further investigation

Nenekidis

Pournaras

Tsironi

et al. 2011

Acta Ophthalmologica

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Extracorporeal circulation (ECC) constitutes a supreme tool for heart surgery allowing the surgeon to work on a secure surgical field by bypassing the cardiopulmonary system. However, pathophysiological hemodynamic changes occur from the use of the heart-lung device that regulates the venous return, cardiac output and oxygenation of blood. This condition is well described as 'surgical hypothermic controlled shock', or in cases of severe hypothermia, the term 'total arrest' is used to denote the lowest level of preservation that the body tolerates with respect to its metabolic needs. Hemodynamic Changes During ECCSignificant changes in homoeostasis occur at the very beginning of ECC as systemic vasodilatation prevails in order to maintain proper blood flow within vital organs. Additionally, the administration of heparin potentiates this vasodilatory effect. Following the establishment of hypothermia (moderate hypothermia, down to 25°C, or severe hypothermia, down to 18°C), the peripheral resistance increases because of severe vasoconstriction. During this phase, the metabolic profile changes because of the decreased metabolic demands of the organism. In general, it is believed that at a temperature of 29-30°C within approximately 130 min of ECC, the energy loss is approximately 330 KJ in a 75-to 90-kg patient (Pacifico et al. 1970 ABSTRACT. The aim of this article was to provide a comprehensive review of current knowledge regarding ocular hemodynamic alterations affecting the retinal neuroglial cells and optic nerve head (ONH) function during cardiac surgery. Literature indicates that visual loss after heart surgery is a rare but devastating complication provoked by two main causes of optic ischaemia and infarction during on-pump cardiac procedures: microembolism and ⁄ or hypoperfusion.Retinal ischaemia and ischaemic optic neuropathy are two possible major consequences of extracorporeal circulation in cardiac surgery. The hemodynamic modifications within the vascular beds of retina and ONH during cardiovascular operations have been incompletely studied. Consequently, it is of great interest to investigate the hemodynamic changes during cardiopulmonary bypass within the choroidal, retinal and optic nerve microcirculations as well as other potential causes of vaso-occlusion. Maintaining stable hemodynamic parameters during cardiovascular surgery seems to be the key to prevent visual impairment.

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Respiratory Acid–Base Disorders

Madias

Adrogué

2013

Seldin and Giebisch's the Kidney

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Effect of Systemic Nitric Oxide Synthase Inhibition on Optic Disc Oxygen Partial Pressure in Normoxia and in Hypercapnia

Abstract: Whereas systemic NOS inhibition did not affect optic disc PO(2) in normoxia, a blunting effect was noted on the CO(2)-induced optic disc PO(2) increase. Nitric oxide appears to mediate the hypercapnic optic disc PO(2) increase.

Cited by 5 publications

References 42 publications

Hypoxic, Hypercapnic, and Hyperoxic Responses of the Optic Nerve Head and Subfoveal Choroid Blood Flow in Healthy Humans

Hypoxic, Hypercapnic, and Hyperoxic Responses of the Optic Nerve Head and Subfoveal Choroid Blood Flow in Healthy Humans

Vision impairment during cardiac surgery and extracorporeal circulation: current understanding and the need for further investigation

Respiratory Acid–Base Disorders

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