A method to monitor urinary carbon dioxide in patients with septic shock


Severe sepsis and septic shock are life-threatening conditions with mortality rates exceeding 31% (Levy et al., 2012) [1]. Septicemia was the most expensive US hospital condition in 2011 (Torio and Andrews, 2006) [2]. Urinary carbon dioxide may provide rapid, clinically useful information about a patient's status, empowering physicians to intervene earlier and improve septic shock mortality. The objective of this paper is to validate a protocol with a Severinghaus-type CO2 probe for the measurement of urinary CO2 of septic shock patients. This protocol includes (i) sampling urine from a Foley catheter in an intensive care unit setting, (ii) storing samples until analysis at a separate facility, (iii) calibration of the Severinghaus-type CO2 sensor, and (iv) measuring urinary CO2 levels. We discuss the preparation and stability of standard solutions, storage of urine samples, and the performance characteristics of the Severinghaus type CO2 sensor in relation to mock urine samples, urine quality control standards, and urine samples from healthy volunteers as well as patients in severe sepsis or septic shock. We report the influence of the sample pH, temperature, and ionic strength on the precision and accuracy of the measurements of urinary CO2 levels and show that the protocol developed for the quantitative assessment of urinary CO2 levels is adequate for the analysis of urine samples collected from a Foley catheter.

Publication Title

Sensors and Actuators, B: Chemical