An abrupt reduction in end-tidal carbon-dioxide during neurosurgery is not always due to venous air embolism: a capnograph artefact

Abstract

Venous air embolism (VAE) is a well recognized complication during neurosurgery. Pre-cordial doppler and trans-esophageal echocardiography are sensitive monitors for the detection of VAE. A sudden, abrupt reduction in the end-tidal carbondioxide (ETCO2) pressure with associated hypotension during neurosurgery might suggest VAE, when more sensitive monitors are not available. We describe an unusual cause for sudden reduction in ETCO2 during neurosurgery and discuss the mechanism for such presentation.

Venous air embolism in neurosurgery

“…8 Capnography is a readily available and economic diagnostic tool, with moderate sensitivity and specificity for diagnosing air embolism when the patient is awake or under general anesthesia.…”

“…7 It may also occur with the patient in lateral decubitus, supine or prone position. 8 The procedures more commonly associated with VAE are craniotomy in the sitting position, surgery of the posterior fossa, and craniosynostosis repair. 9,10 In pediatric neurosurgery the incidence reported has ranged between 9.8 and 0.42%.…”

Journal of clinical monitoring and computing 2014 end of year summary: respiration

“…The Journal of Clinical Monitoring and Computing has featured several articles in 2014 focused on capnography including one paper on its use during high frequency oscillatory ventilation (HFOV) [14] two papers highlighting two clinical scenarios and the importance of interpreting capnograms in clinical context [15,16] and a technically oriented paper that highlights some of issues and tradeoffs with the design and testing of a mainstream capnometer [17]. As these papers and others published in the past in this journal have illustrated, the application of capnography, time and volumetric, are varied [18] and the clinical use of capnography is growing being driven in part by recent changes expanding the use of capnography in the ASA basic monitoring during anesthesia standards [19] and AHA CPR guidelines [20].…”

“…In a letter to the editor, Vinay et al [15] present in the form of a case report a warning about an abrupt and apparently artifactual reduction in end-tidal carbon dioxide readings during neurosurgery when using low flow rate sidestream capnography. The abrupt change in carbon dioxide (28-9 mm Hg), it was reported, was not associated with changes in blood pressure, heart rate or amplitude of the photoplethymographic waveform.…”

Embolismo aéreo venoso en neurocirugía

“…Una reducción súbita en el nivel de CO 2 espirado asociada a hipotensión arterial, es altamente sugestiva de embolismo aéreo 8 . La capnografía es una herramienta diagnóstica de fácil acceso y económica, con moderada sensibilidad y especificidad, que permite hacer el diagnóstico de embolismo aéreo cuando el paciente está despierto o bajo anestesia general.…”