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Utility of a Near-Infrared Reflectance Spectroscopy Oximeter in Shock FREE TO VIEW

Leslie Wood; James Aden; Michael Morris; David Bell; John Hunninghake; Victor Convertino; Kevin Chung
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San Antonio Military Medical Center, Joint Base San Antonio, Fort Sam Houston, TX

Chest. 2014;146(4_MeetingAbstracts):234A. doi:10.1378/chest.1995060
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SESSION TITLE: Sepsis & Septic Shock Posters

SESSION TYPE: Original Investigation Poster

PRESENTED ON: Wednesday, October 29, 2014 at 01:30 PM - 02:30 PM

PURPOSE: The objective of this study is to determine whether near-infrared reflectance spectroscopy (NIRS) measurement of deep tissue oxygen saturation (SmO2) and deep tissue pH (pHm) are reflective of shock in critically ill adults.

METHODS: An institutional review board approved, prospective, observational study was performed in adult subjects in 2 intensive care units at our center. After obtaining informed consent, lactate levels were collected at various time points while SmO2 and pHm were continuously measured using a Careguide 1100™ monitor (RMI, Worcester, MA) up to 8 hours daily, for as many as 5 days for each subject. Presence of shock was determined at each time point using any of the following criteria: SBP<90mmHg for >10 minutes, need for vasopressor therapy or lactate level>2mmol/L. Presence of anasarca was defined by upper extremity pitting edema. Mann-Whitney U test was performed to compare continuous variables.

RESULTS: During a 3 month period, 6 subjects were enrolled, providing 15 study days and a total of 38 time point comparisons of shock determination and NIRS measurements. Shock was present at 17 of 38 time points. SmO2 measurements were significantly lower in the shock group compared to the non-shock group (56.8 ± 2.9 vs. 67.0 ± 2.9, p= 0.02) while no significant difference was detected in pHm (7.33 ± 0.02 vs. 7.36 ± 0.02, P=0.23). In the presence of anasarca, both the SmO2 (46 ± 3 vs. 74 ± 5, p=0.001) and pHm (7.25 ± 0.02 vs. 7.34 ± 0.03, p=0.018) were significantly lower in the shock group when compared to the non shock group.

CONCLUSIONS: Our preliminary analysis revealed that SmO2 is significantly lower in shock states. The presence of anasarca did not appear to obscure the reliability of the sensor to detect shock.

CLINICAL IMPLICATIONS: Current medical practice utilizes heart rate and blood pressure as indicators of cardiovascular status and shock. However, these variables are unreliable and are often late indicators of shock. Identification of variables which more efficiently identify shock would have tremendous utility in the management of critically injured patients. Decreases in SmO2 occur in shock and may allow early identification and targeted resuscitation of shock.

DISCLOSURE: The following authors have nothing to disclose: Leslie Wood, James Aden, Michael Morris, David Bell, John Hunninghake, Victor Convertino, Kevin Chung

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