Correlation between brain tissue oxygen tension and regional cerebral oximetry in uninjured human brain under conditions of changing ventilation strategy.

Controversy surrounds regional cerebral oximetry (rSO2) because extracranial contamination and unmeasured changes in cerebral arterial:venous ratio confound readings. Correlation of rSO2 with brain tissue oxygen (PbrO2), a "gold standard" for cerebral oxygenation, could help resolve this controversy but PbrO2 measurement is highly invasive. This was a prospective cohort study. The primary aim was to evaluate correlation between PbrO2 and rSO2 and the secondary aim was to investigate the relationship between changing ventilation regimens and measurement of PbrO2 and rSO2. Patients scheduled for elective removal of cerebral metastases were anesthetized with propofol and remifentanil, targeted to a BIS range 40-60. rSO2 was measured using the INVOS 5100B monitor and PbrO2 using the Licox brain monitoring system. The Licox probe was placed into an area of normal brain within the tumor excision corridor. FiO2 and minute ventilation were sequentially adjusted to achieve two set points: (1) FiO2 0.3 and paCO2 30 mmHg, (2) FiO2 1.0 and paCO2 40 mmHg. PbrO2 and rSO2 were recorded at each. Nine participants were included in the final analysis, which showed a positive Spearman's correlation (r = 0.50, p = 0.036) between PbrO2 and rSO2. From set point 1 to set point 2, PbrO2 increased from median 6.0, IQR 4.0-11.3 to median 22.5, IQR 9.8-43.6, p = 0.015; rSO2 increased from median 68.0, IQR 62.5-80.5 to median 83.0, IQR 74.0-90.0, p = 0.047. Correlation between PbrO2 and rSO2 is evident. Increasing FiO2 and PaCO2 results in significant increases in cerebral oxygenation measured by both monitors.

Informed consent for anesthesia: a review of practice and strategies for optimizing the consent process.

PURPOSE: Patients must receive information in a manner that promotes understanding so they can make informed decisions about anesthesia and other medical interventions. Unfortunately, history is replete with examples of the negative consequences of inadequate disclosure of information and lack of patient understanding. While obtaining consent for anesthesia poses unique challenges, the ability of the anesthesiologist to engage the patient in meaningful discussion is critical as a means to ensure that the patient is truly informed. This narrative review aims to: 1) discuss the process of informed consent as it applies to anesthesia practice; 2) describe the salient issues related to patient capacity, disclosure, understanding, decision-making, and documentation of the informed consent process; and 3) discuss current strategies to improve the presentation and understanding of consent information. SOURCE: Review of the extant literature, including the authors' own research. PRINCIPAL FINDINGS: Despite the ethical imperative of informed consent, many decision-makers have limited understanding of medical information. The reasons for this are multifactorial but often result from incomplete disclosure and presentation of generic information that does not take into account differences in information needs, values, and preferences of individual patients. Several simple strategies are available, however, that can enhance decision-makers' understanding of both written and verbal information. CONCLUSIONS: Despite the unique challenges of obtaining consent for anesthesia on the day of surgery, attention to the manner in which information for anesthesia care is provided and adoption of simple strategies to enhance understanding can go a long way to ensure that decision-makers are appropriately informed.