Central venous saturation in septic shock: co-oximetry vs gasometry.

OBJECTIVES: Central venous oxygen saturation calculated by gasometry (Gaso-Scvo2) is more available than central venous oxygen saturation measured by co-oximetry (Co-oxy-Scvo2) in environments with less resources and underdeveloped countries. Therefore, we aimed to determine the agreement between Co-oxy-Scvo2 and Gaso-Scvo2 and between central venous oxygen tension measured by gasometry (Gaso-Pcvo2) and Co-oxy-Scvo2, respectively. DESIGN AND SETTINGS: This is a prospective study in a university hospital's intensive care unit. PATIENTS: Sixteen patients were studied during the first 48 hours after diagnosis of septic shock. All patients were intubated, connected to mechanical ventilation, and resuscitated according to the standards of care. MEASUREMENTS AND RESULTS: One hundred eleven pairs of central venous blood measurements were analyzed both by conventional gasometry and co-oximetry. Bland and Altman analysis between Co-oxy-Scvo2 and Gaso-Scvo2 showed lack of agreement (1.7 [-10.7, +14.2]). A Gaso-Scvo2 less than 70% had a positive predictive value of 63% in relation to Co-oxy-Scvo2, and its negative predictive value was 90% with 20% false-positives and 5% false-negatives. The area under the receiver operator characteristic curve of Gaso-Pcvo2 to discriminate a Co-oxy-Scvo2 greater than or equal to 70% was 0.87 (confidence interval, 0.80-0.93), and the best cut-off point was a Gaso-Pcvo2 more than 40 mm Hg, (sensitivity, 75%; specificity, 93%). CONCLUSIONS: The reliability of Gaso-Scvo2 determination during the resuscitation phase of septic shock is not acceptable. There is a good agreement between a Gaso-Pcvo2 more than 40 mm Hg and a Co-oxy-Scvo2 greater than or equal to 70%. Our results suggest that given these limitations, Gaso-Scvo2 results should be interpreted with caution, helped by Gaso-Pcvo2 measurements and in context with other perfusion parameters.

Incidencia de beta-lactamasas de espectro extendido en el Hospital Clínico de la Universidad de Chile / Incidence of extended-spectrum beta-lactamases in University of Chile Clinical Hospital

Las Betalactamasas de espectro extendido (BLEE) son enzimas de configuración plasmídica producidas por bacterias que hidrolizan los antibióticos betalactámicos. La aparición de cepas bacterianas productoras de BLEE, constituye un problema de salud pública que afecta a todo tipo de instituciones y a la comunidad en general. Este estudio tiene como objetivo determinar las incidencia de BLEE en pacientes hospitalizados del Hospital Clínico de la Universidad de Chile. Se estudió un total de 238 cepas en el periodo julio-agosto 2004; de las cuales 184 correspondieron a de E. coli, 39 a K. pneumoniae y 15 a K. oxytoca, utilizándose el test confirmatorio de BLEE según estándar NCCLS 2004. Se encontró una incidencia de BLEE para E. coli de un 10.3 por ciento, para K. pneumoniae de 28.2 por ciento y de K. oxytoca de 20 por ciento, respectivamente. La distribución de los aislamientos de las cepas BLEE (+) en los distintos servicios del Hospital fue diversa: E. coli se encontró principalmente, en los servicios de medicina y cirugía, y K. pneumoniae en los servicios críticos. Los resultados del estudio permitieron conocer la incidencia y distribución de BLEEs en el Hospital Clínico de la Universidad de Chile y justificaron la implementación de esta técnica de diagnóstico como parte de la rutina del laboratorio de microbiología.