Injury severity and serum amyloid A correlate with plasma oxidation-reduction potential in multi-trauma patients: a retrospective analysis

Background: In critical injury, the occurrence of increased oxidative stress or a reduced antioxidant status has been observed. The purpose of this study was to correlate the degree of oxidative stress, by measuring the oxidation-reduction potential (ORP) of plasma in the critically injured, with injury severity and serum amyloid A (SAA) levels. Methods: A total of 140 subjects were included in this retrospective study comprising 3 groups: healthy volunteers (N = 21), mild to moderate trauma (ISS < 16, N = 41), and severe trauma (ISS >= 16, N = 78). For the trauma groups, plasma was collected on an almost daily basis during the course of hospitalization. ORP analysis was performed using a microelectrode, and ORP maxima were recorded for the trauma groups. SAA, a sensitive marker of inflammation in critical injury, was measured by liquid chromatography/ mass spectrometry. Results: ORP maxima were reached on day 3 (+/- 0.4 SEM) and day 5 (+/- 0.5 SEM) for the ISS < 16 and ISS >= 16 groups, respectively. ORP maxima were significantly higher in the ISS < 16 (-14.5 mV +/- 2.5 SEM) and ISS >= 16 groups (-1.1 mV +/- 2.3 SEM) compared to controls (-34.2 mV +/- 2.6 SEM). Also, ORP maxima were significantly different between the trauma groups. SAA was significantly elevated in the ISS >= 16 group on the ORP maxima day compared to controls and the ISS < 16 group. Conclusion: The results suggest the presence of an oxidative environment in the plasma of the critically injured as measured by ORP. More importantly, ORP can differentiate the degree of oxidative stress based on the severity of the trauma and degree of inflammation.