Abstract
Objectif
Montrer que l’index bispectral (BIS) n’est pas uniquement un moyen de surveillance de la profondeur de l’anesthésie, mais qu’une chute rapide de l’index peut être reliée à une souffrance cérébrale importante.
Constatations cliniques
Plusieurs observations cliniques montrent qu’une chute inexpliquée du BIS peut être rattachée à une ischémie cérébrale. Ainsi, les potentiels évoqués somesthésiques ont baissé parallèlement à la baisse du BIS pendant le clampage carotidien chez un patient de 58 ans subissant une endartériectomie carotidienne. Aussi chez un patient de 62 ans qui subissait la résection d’un anévrisme aortique, le BIS a diminué de 40–50 % à 8 % à mesure que diminuait l’index cardiaque et la saturation en O2 du sang veineux central. Le BIS est revenu à la normale quand le bas débit cardiaque a été corrigé à l’aide de médicaments.
Conclusion
Bien que le BIS soit un bon moyen de surveillance de la profondeur de l’anesthésie, plusieurs facteurs indépendants de l’anesthésie sont à l’origine de modifications du BIS. Ajuster le niveau d’anesthésie uniquement sur les données du BIS serait une erreur. Malgré sa sensibilité et sa spécificité insuffisantes dans cette indication, l’intérêt du BIS serait de permettre de dépister un état de souffrance cérébrale.
Abstract
Purpose
To show that the bispectral index (BIS) is not only a monitor of the depth of anesthesia but that acute decreases of the index may be related to severe cerebral ischemia.
Clinical features
Several clinical observations suggest that an unexplained fall of the BIS may be the result of cerebral ischemia. Somatosensory evoked potentials decreased in parallel to the decrease in BIS during carotid clamping in a 58-yr-old patient undergoing carotid endarterectomy. In a 62-yr-old patient undergoing resection of an aortic aneurysm, the BIS decreased from 40–50% to 8% as the cardiac index and central venous O2 saturation decreased. The BIS returned to normal values when the low cardiac output was corrected pharmacologically.
Conclusion
While the BIS is a well accepted monitor of the depth of anesthesia, several factors, unrelated to anesthesia, can modify the index. Thus, to adjust the level of anesthesia based solely on the BIS could be inappropriate. While the sensitivity and specificity of the BIS for this indication have not been determined, we suggest that the BIS may be useful to detect severe cerebral ischemia.
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Mérat, S., Lévecque, J.P., Gulluche, Y.L. et al. Intérêt potentiel du BIS pour détecter une souffrance cérébrale importante. Can J Anesth 48, 1066–1069 (2001). https://doi.org/10.1007/BF03020370
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DOI: https://doi.org/10.1007/BF03020370