University of Southern Denmark Retinal Vascular Oxygen Saturation

University of Southern Denmark

Retinal vascular oxygen saturation increases after cardiac surgery

Dinesen, Sebastian; Jensen, Pia S; Bloksgaard, Maria; Mey, Jo De; Lindholt, Jes S; Rasmusssen, Lars M; Grauslund, Jakob

Published in: Acta Ophthalmologica

DOI: 10.1111/aos.14084

Publication date: 2019

Document version: Accepted manuscript

Citation for pulished version (APA): Dinesen, S., Jensen, P. S., Bloksgaard, M., Mey, J. D., Lindholt, J. S., Rasmusssen, L. M., & Grauslund, J. (2019). Retinal vascular oxygen saturation increases after cardiac surgery. Acta Ophthalmologica, 97(6), e941- e942. https://doi.org/10.1111/aos.14084

Go to publication entry in University of Southern Denmark's Research Portal

Terms of use This work is brought to you by the University of Southern Denmark. Unless otherwise specified it has been shared according to the terms for self-archiving. If no other license is stated, these terms apply:

• You may download this work for personal use only. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying this open access version If you believe that this document breaches copyright please contact us providing details and we will investigate your claim. Please direct all enquiries to [email protected]

Download date: 27. Sep. 2021 Retinal vascular oxygen saturation increases after cardiac surgery.

Sebastian Dinesen1, Pia S. Jensen2, Maria Bloksgaard3, PhD, Jo De Mey3, 4, 5, PhD, Jes S.Lindholt4, 6, 7, DMSc, Lars M. Rasmusssen2, 6, 7, DMSc, Jakob Grauslund1, 7, DMSc

1. Department of Ophthalmology, Odense University Hospital, Odense, Denmark.

2. Department of Clinical Biochemistry and Pharmacology, Odense University Hospital, Odense, Denmark.

3. Department of Molecular Medicine, University of Southern Denmark, Odense, Denmark.

4. Department of Cardiac, Thoracic and Vascular Surgery, Odense University Hospital, Odense, Denmark.

5. Department of Pharmacology and Personalized Medicine, Maastricht University, Maastricht, the Netherlands.

6. Centre of Individualized Medicine in Arterial Diseases (CIMA), Odense University Hospital, Odense, Denmark.

7. Department of Clinical Research, University of Southern Denmark, Odense, Denmark.

Corresponding author Jakob Grauslund, Department of Ophthalmology, Odense University Hospital, Sdr. Boulevard 29, 5000 Odense, Denmark. E-mail: [email protected] Phone: 6541 2782 Fax number: 6612 6387

Main text: 564 words

Editor,

The retinal vascular tree is the only part of the human microvascular system available for direct in vivo inspection. Retinal metabolism can be measured non-invasively and well-validated by retinal oximetry (Hardarson, 2013). Disturbances in retinal oximetry have consistently been demonstrated in ischaemic diseases like diabetic retinopathy and retinal vein occlusion (Rilven et al., 2017). Likewise, changes in retinal arteriolar (raSatO2) and venular (rvSatO2) oxygen saturation have been found in extra ocular diseases like chronic obstructive pulmonary disease and Alzheimer’s disease (Eliasdottir, 2018; Einarsdottir et al., 2016).

The present study aimed to evaluate the potential effect of cardiac surgery on the retinal microvascular oxygen saturation to clarify the interplay between the retinal and the systemic microvascular system. We included nine Caucasian participants scheduled for cardiovascular surgery, recruited at the Department of Cardiac, Thoracic and Vascular Surgery, Odense University Hospital. Patients had baseline oximetry imaging on the day before the surgery. The follow-up examination was performed when pace-wires and monitoring scope had been decoupled between four and six days after surgery. Patients with age <18 years, mental inability, ocular disease and need for re-surgery were excluded. One patient was excluded at baseline on behalf of these criteria. Ocular mydriasis was achieved with tropicamide 1% and phenylephedrine 10%. Retinal oximetry imaging (Oxymap T1, V.2.4.2, Reykjavik, Iceland) was captured after two minutes in dimmed light. We selected the eye estimated to have the best potential for high quality imaging and disc centred images were obtained. The images were graded with the Oxymap analyser software in accordance with a pre-specified protocol (Hardarson, 2013) by a trained grader (SD). A p-value < 0.05, calculated using Stata Intercooled 15 (StataCorp, College Station, Texas, USA), was considered to denote statistical significance.

Five out of eight were men and the median age was 68 years (range 59 to 79 years). One patient had isolated coronary artery bypass grafting (CABG), five had isolated aortic valve replacement and two had combined CABG and aortic valve replacement.

The median retinal oxygen saturation was increased post-operatively in both arterioles

(90.8% vs. 94.9%, p=0.04, Wilcoxon Rank sum test) and venules (50.8% vs. 69.7%, p=0.01). In six out of eight patients, raSatO2 was increased after surgery whereas it was unchanged in one and decreased in one other patient. The change after surgery ranged from minus 3.2% to plus 7.8%. All patients displayed elevated rvSatO2 after surgery. This decrease ranged from 5.0% to 24.3%.

Figure 1 shows the changes in both raSatO2 and rvSatO2 observed in the individual subjects.

raSatO2 and rvSatO2 were increased after major cardiovascular surgery in a small Caucasian population. Restoration of cardiac output following coronary re- vascularization or most likely cardiac valve replacement may have enhanced systemic blood flow reflected in the retinal circulation. The increase in retinal blood flow then reduced the extraction of oxygen per unit of time from arterioles, as a result of increased linear velocity of the blood (Jeppesen & Bek, 2018). Consequently, we measured increased concentrations of oxygen in both arterioles and venules. One can speculate why auto-regulation of blood flow did not attenuate the increased perfusion to ensure optimal conditions for sufficient oxygen extraction by the tissues. Chronic vasoconstriction may have rendered the arterioles rigid and less contractile.

In conclusion, non-invasive retinal oximetry may be used to measure changes in the systemic circulation. The present study adds to the available evidence, but more studies are needed to extend the current knowledge.

References

Hardarson, S. H. (2013). Retinal oximetry. Acta Ophthalmol, 91 Thesis 2, 1-47. Rilven, S., Torp, T. L., & Grauslund, J. (2017). Retinal oximetry in patients with ischaemic retinal diseases. Acta Ophthalmol, 95(2), 119-127. Eliasdottir, T. S. (2018). Retinal oximetry and systemic arterial oxygen levels. Acta Ophthalmol, 96 Suppl A113, 1-44. Einarsdottir, A. B., Hardarson, S. H., Kristjansdottir, J. V., Bragason, D. T., Snaedal, J., & Stefansson, E. (2016). Retinal oximetry imaging in Alzheimer's disease. J Alzheimers Dis, 49(1), 79-83. Jeppesen, S. K., & Bek, T. (2018). The Retinal Oxygen Saturation Measured by Dual Wavelength Oximetry in Larger Retinal Vessels is Influenced by the Linear Velocity of the Blood. Curr Eye Res, 1-7.

Figure legend Mean retinal arteriolar (red) and venular (blue) oxygen saturation before and after cardiac surgery in eight patients from Odense University Hospital, Odense, Denmark. * = p < 0.05. *** = p < 0.001.

Figure 1