DOI: 10.1097/01.ccm.0000425285.38504.69
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Issn Print: 0090-3493
Publication Date: 2012/12/01
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Abstract
Introduction:Noninvasive measurement of tissue perfusion may provide a tool to detect occult shock and guide resuscitation. The skin is the first to vasoconstrict in shock and the last to perfuse. Transcutaneous PO2 (PtcO2) changes with PaO2 and FiO2 in non-shock states, but during shock, PtcO2 approximates cardiac output with minimum response to increasing FiO2 and PaO2 due to vasoconstriction of the skin. (1,2) This response called the Oxygen Challenge test (OCT), and has been shown to predict organ failure, mortality, and used as an endpoint of resuscitation. OCT value of?25 implies adequate perfusion, and <25 implies shock. (1,2). Another technology is the tissue hemoglobin oxygen saturation (StO2) on the thenar eminence using near infrared spectroscopy. StO2 values <75-80% as well as very high values >90% implies shock. A new parameter, the Perfusion index (PI) is the ratio of pulsatile to nonpulsatile flow and is part of the cooximeter measuring SpO2 (Masimo, Irvine). PI may provide information on peripheral tissue perfusion.
Hypothesis:There is a relationship between all 3 methods of measuring tissue perfusion.
Methods:Simultaneous measurements of OCT, StO2, and PI were done in critically ill surgical patients during resuscitation and throughout the ICU stay. Positive (+OCT) was defined as?25 mmHg (adequate perfusion); negative (–OCT) was defined as <25 mmHg (inadequate perfusion).
Results:34 patients generated 163 data points. Demographics were: 66 ± 17 yrs of age, 20 males:14 females, APACHE II 22 ± 6, 23 septic shock/severe sepsis, 8 cardiac failure, 22 respiratory failure patients. Correlation existed between StO2 and PI, r=.41 (p<.001), R2=.16, p<.001. There were no differences in StO2 values between +OCT (79 ± 11%) and –OCT (82 ± 6%), (p=.13). There were differences in PI between +OCT (2.5 ± 1.6) vs –OCT (1.8 ± 1.1) groups, p=.03.
Conclusions:StO2 was difficult to use due to a wide range of values associated with adequate perfusion. PI values demonstrated a weak relationship to StO2, and a closer relationship to the OCT but further assessment is needed.1)Yu M et al, Shock 2007;27:615. 2) He,HW et al. Shock 2012;37:152. 3)Crookes BA et al, J Trauma 2005;58:806.
