Adv Exp Med Biol
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The CAS neonatal NIRS system determines absolute regional brain tissue oxygen saturation (SnO2) and brain true venous oxygen saturation (SnvO2) non-invasively. Since NIRS-interrogated tissue contains both arterial and venous blood from arterioles, venules, and capillaries, SnO2 is a mixed oxygen saturation parameter, having values between arterial oxygen saturation (SaO2) and cerebral venous oxygen saturation (SvO2). To determine a reference for SnO2, the relative contribution of SvO2 to SaO2 drawn from a brain venous site vs. systemic SaO2 is approximately 70:30 (SvO2:SaO2). If the relationship of the relative average contribution of SvO2 and SaO2 is known and does not change to a large degree, then NIRS true venous oxygen saturation, SnvO2, can be determined non-invasively using SnO2 along with SaO2 from a pulse oximeter.
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Review
Should dexamethasone be part of routine therapy of bacterial meningitis in industrialised countries?
Two issues are clear from the data available regarding the current place of dexamethasone in routine management of suspected bacterial meningitis in industrialised countries. First, there is now good evidence of benefit from adjunctive dexamethasone therapy which is not confined to Hib meningitis, but in the case of pneumococcal meningitis probably requires that dexamethasone is given with or before, rather than after, parenteral antibiotics. In meningococcal meningitis, statistically significant benefit has not been demonstrated for any outcome, even in meta-analyses, but the point estimate is in the direction of benefit and failure to demonstrate an effect is more likely to be due to limited power from low event rates rather than no benefit; certainly there is no evidence of a detrimental effect. ⋯ In addition, the prospect of clinical trials in children, already limited by small case numbers, will be further reduced when the use of the conjugate pneumococcal vaccines is widespread. In Canada, a trend to decreasing use of corticosteroids was noted between 1991 and 1999, probably reflecting conflicting evidence. (16). Unless clear protocols are in place, the commencement of steroids before or with antibiotics will be difficult to implement in emergency situations, as illustrated by the data from Sydney.