Letter to the editor
We read with interest the review on the pathophysiology of ‘happy’ hypoxemia in COVID-19 by Dhont et al. published in BMC Respiratory Research [1]. This exhaustive review, describing the pathophysiological abnormalities in COVID-19 that might explain the disconnect between the severity of hypoxemia and the relatively mild respiratory discomfort reported by the patients, aims at improving decision-making and management among the physicians treating COVID-19. Very recent articles and reviews on the neurological manifestations of COVID-19 report patients with severe COVID-19 at risk for multifocal microvascular hemorrhagic and ischemic lesions [2–7]. Therefore, it would be very valuable to monitor the brain oxygenation state in mechanically ventilated patients with COVID-19.
In the last decades, brain oxygenation has been successfully monitored noninvasively and transcranially in the operative room and in the intensive care unit by commercial near-infrared spectroscopy (NIRS) brain oximeters [8–11]. These oximeters provide the intensivists with a continuous measure of the prefrontal cortex oxyhemoglobin saturation (ScO2, %). Unlike conventional fingertip pulse oximetry, ScO2 does not rely on a pulsating flow, and reflects the balance between oxygen supply and demand in the arteriolar, capillary and venular beds of the brain cortex underlying the prefrontal area over the sensor is located. Detailed cerebral oximetry guidelines have recently been drawn up by the Japanese Society of Cardiovascular Anesthesiologists [12].
To the best of our knowledge, so far the use of cerebral oximetry on ventilated COVID-19 patients has never been reported. In this framework, we suggest that the ScO2 monitoring in these patients might serve as an “early warning indicator” of the decreased brain oxygen delivery. The ScO2 data can be utilized to optimize cerebral oxygen supply and demand, inversing the decreased cerebral perfusion and/or preventing protracted brain ischemia.
Interestingly, cortical oximetry is utilized in an ongoing clinical trial of the Hvidovre University Hospital (Denmark) aiming to examine whether ScO2 could be a more useful parameter than peripheral arterial oxygen saturation, measured by fingertip pulse oximetry, to guide clinical titration of permissive hypoxemia in COVID-19 acute respiratory distress syndrome patients [13].
Acknowledgements
Not applicable.
Abbreviations
- NIRS
Near-infrared spectroscopy
- ScO2
Oxyhemoglobin saturation
Authors’ contributions
MF: drafted the letter, edited and reviewed the final submission. VQ: provided content input, critical feedback, edited and reviewed the final submission. The author(s) read and approved the final manuscript.
Funding
None.
Availability of data and materials
Not applicable.
Ethics approval and consent to participate
Not applicable.
Consent for publication
Not applicable.
Competing interests
MF: no funding to declare or any conflicts of interest related to this work.
VQ: no funding to declare or any conflicts of interest related to this topic.
Footnotes
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
References
- 1.Dhont S, Derom E, Van Braeckel E, Depuydt P, Lambrecht BN. The pathophysiology of ‘happy’ hypoxemia in COVID-19. Respir Res. 2020;21(1):198. doi: 10.1186/s12931-020-01462-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Ahmad I, Rathore FA. Neurological manifestations and complications of COVID-19: a literature review. J Clin Neurosci. 2020;77:8–12. doi: 10.1016/j.jocn.2020.05.017. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Gupta A, Madhavan MV, Sehgal K, et al. Extrapulmonary manifestations of COVID-19. Nat Med. 2020;26(7):1017–1032. doi: 10.1038/s41591-020-0968-3. [DOI] [PubMed] [Google Scholar]
- 4.Jaunmuktane Z, Mahadeva U, Green A, et al. Microvascular injury and hypoxic damage: emerging neuropathological signatures in COVID-19. Acta Neuropathol. 2020;140(3):397–400. doi: 10.1007/s00401-020-02190-2. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Kremer S, et al. Brain MRI findings in severe COVID-19: a retrospective observational study. Radiology. 2020:202222. 10.1148/radiol.2020202222. [DOI] [PMC free article] [PubMed]
- 6.Nepal G, Rehrig JH, Shrestha GS, Shing YK, Yadav JK, Ojha R, et al. Neurological manifestations of COVID-19: a systematic review. Crit Care. 2020;24(1):421. doi: 10.1186/s13054-020-03121-z. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Whittaker A, Anson M, Harky A. Neurological manifestations of COVID-19: a systematic review and current update. Acta Neurol Scand. 2020;142(1):14–22. doi: 10.1111/ane.13266. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Benni PB, MacLeod D, Ikeda K, Lin HM. A validation method for near-infrared spectroscopy based tissue oximeters for cerebral and somatic tissue oxygen saturation measurements. J Clin Monit Comput. 2018;32(2):269–284. doi: 10.1007/s10877-017-0015-1. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Eyeington CT, Ancona P, Osawa EA, Cutuli SL, Eastwood GM, Bellomo R. Modern technology-derived normative values for cerebral tissue oxygen saturation in adults. Anaesth Intensive Care. 2019;47(1):69–75. doi: 10.1177/0310057X18811962. [DOI] [PubMed] [Google Scholar]
- 10.Ferrari M, Quaresima V. Review: near infrared brain and muscle oximetry: from the discovery to current applications. J Near Infrared Spectr. 2012;20(1):1–14. doi: 10.1255/jnirs.973. [DOI] [Google Scholar]
- 11.Tosh W, Patteril M. Cerebral oximetry. BJA Educ. 2016;16(12):417–421. doi: 10.1093/bjaed/mkw024. [DOI] [Google Scholar]
- 12.Yoshitani K, Kawaguchi M, Ishida K, Maekawa K, Miyawaki H, Tanaka S, et al. Guidelines for the use of cerebral oximetry by near-infrared spectroscopy in cardiovascular anesthesia: a report by the cerebrospinal Division of the Academic Committee of the Japanese Society of Cardiovascular Anesthesiologists (JSCVA) J Anesth. 2019;33(2):167–196. doi: 10.1007/s00540-019-02610-y. [DOI] [PubMed] [Google Scholar]
- 13.Clinical Trial: effects of cardiovascular and pulmonary optimization on cerebral oxygenation in COVID-19 patients with severe ARDS (NIRS-COV). ClinicalTrials.gov Identifier: NCT04392089. https://clinicaltrials.gov/ct2/show/NCT04392089. Accessed 24 Aug 2020.
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
Not applicable.