To the Editor,
We read the article written by Dr Dilek Ceyhan et al. on the use of cerebral oximeter in carotid endarterectomy (CEA) surgery.[1] We do agree that cerebral oxymeter is a good monitoring device and is helpful to assess brain tissue oxygenation level in the patients undergoing surgery, but we cannot rely completely on it for CEA.
Carotid endarterectomy is a surgical procedure to reduce the risk of stroke by correcting stenosis in common carotid artery or in internal carotid artery. Endarterectomy is the removal of material from the inside of an artery. There is a high chance of neurological impairment during the procedure. Moreover, reflex bradycardia or heart blocks are frequently caused by the manipulation of the carotid baroreceptors.
We can use cerebral oxymeter device to assess tissue oxygenation. The advantage is that, it is noninvasive technique, does not require pulsatile blood flow, and is easy to interpret. The monitor differentiates two forms of oxygenated and deoxygenated hemoglobin and determines the regional saturation (rSO2) in the frontal lobes.[2] So it does not require only pulsatile blood flow. It determines saturation mainly form venous blood (75%) and also form arterial blood (25%). It has the capability to calculate oxygen saturation of brain tissue even in hypothermia, severe cerebral ischemia and during circulatory arrest.
There are certain limitations to it's use. One should keep in mind that the device uses near infrared spectrometry to estimate oxygen saturation in a sample volume of one small region of brain frontal lobe. It does not involve whole brain. We can get an idea of oxygen status of a small part of brain, so we cannot completely rely on its value in order to protect the cerebral function.[3] Continuous monitoring of the vitals with prompt interventions, use of the shunt, maintaining normocarbia and keeping high mean arterial pressure during arterial clamp are important to successfully manage patient for carotid endarterectomy.
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References
- 1.Ceyhan D, Ovali C. The effect of cerebral oximeter use on the shunt placement concerning carotid endarterectomy surgery. ACA. 2019;22:158–61. doi: 10.4103/aca.ACA_57_18. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Colak Z, Borojevic M, Ivancan V, Gabelica R, Biocina B, Majeric-Kogler V. The relationship between prolonged cerebral oxygen desaturation and postoperative outcome in patients undergoing coronary artery bypass grafting. Coll Antropol. 2012;36:381–8. [PubMed] [Google Scholar]
- 3.Kunst G, Milan Z. Cerebral oximetry: Another blow to non-invasive monitoring? Anaesthesia. 2017;72:1435–8. doi: 10.1111/anae.14064. [DOI] [PubMed] [Google Scholar]