Abstract
This study was undertaken to examine the variation of the arterial to end-tidal PCO2 (Pa-PetCO2 difference during prolonged neurosurgical anaesthesia. Hyperventilation is often used to reduce intracranial pressure in neurosurgical patients. Continuous end-tidal CO2 monitoring is used as a guide between arterial CO2 measurements. We examined the stability of the Pa-PetCO2 difference in 21 patients undergoing elective craniotomies lasting greater than four hours. A balanced neuroanaesthetic technique was used with the ventilation variables at the discretion of the attending anaesthetist. Once patients were positioned for surgery, simultaneous samples of arterial PCO2 through an arterial catheter, and end-tidal PCO2 via a mass spectrometer were obtained. The Pa-PETCO2 differences of each patient were plotted against time and a slope was derived with simple linear regression. The mean slope for all patients was then computed. There were no changes in the Pa-PETCO2 difference with time (P > 0.05) suggesting a constant relationship between the arterial and end-tidal PCO2 measurements over time. We conclude that end-tidal PCO2 can be used as a reliable guide to estimate arterial PCO2 during neurosurgical procedures of greater than four hours duration once the Pa-PetCO2 difference has been established.
Résumé
Cette étude vise à étudier les variations de la différence entre la PaCO2 artérielle et télé-expiratoire (Pa-PetCO2) pendant l’anesthésie neurochirurgicale de longue durée. On utilise souvent l’hyperventilation pour diminuer la pression intracranienne en neurochirurgie. Le monitorage continu de CO2 téléexpiratoire est utilisé entre les analyses du CO2 artériel. Nous étudions la stabilité de la différence Pa-PetCO2 chez 21 patients soumis à une craniotomie réglée dont la durée dépasse quatre heures. Une technique neuro-anesthésique équilibrée est utilisée dont les paramètres respiratoires sont laissés à la discrétion de l’anesthésiste responsable. Une fois les patients installés pour la chirurgie, des échantillons de sang pour la PaCO2 sont prélevés par un cathéter artériel, et ceux la PCO2 télé-expiratoire par un spectromètre de masse. Pour chaque patient, un tracé des différences Pa-PETCO2 mis en rapport avec le temps est réalisé et une courbe avec régression linéaire simple en est dérivée. La pente moyenne pour tous les patients est ensuite calculée. Le fait qu’il n’y ait pas de changement de la différence PaCO2-PETCO2 en rapport avec le temps (P > 0,05) suggère que la relation entre les mesures artérielles et télé-expiratoires de la PCO2 est constante dans le temps. Nous concluons que la PCO2 télé-expiratoire estime de façon fiable la PCO2 artérielle pendant les interventions neurochirurgicales qui durent quatre heures et plus, une fois la différence Pa-PETCO2 établie.
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Sharma, S.K., McGuire, G.P. & Cruise, C.J.E. Stability of the arterial to end-tidal carbon dioxide difference during anaesthesia for prolonged neurosurgical procedures. Can J Anaesth 42, 498–503 (1995). https://doi.org/10.1007/BF03011688
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DOI: https://doi.org/10.1007/BF03011688