Lipid peroxidation parameters and antioxidant status of critically ill intensive care unit patients

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Lipid peroxidation (LPO) is believed to play a crucial role in several disorders involving free radical action. Especially intensive care unit (ICU) patients suffer from situations, which lead to formation of free radicals and subsequent LPO, eg septicemia, multi organ failure or ischemic situations. Methods for the measurement of LPO products are usually restricted to specialists due to relatively complicated methodology. On the other hand, there is demand for routine methods to monitor LPO and/or antioxidative capacity of ICU patients. The scope of this study was to evaluate and compare some methods for the measurement of LPO products and antioxidant capacity with special respect to therapeutic intervention and clinical outcome of the patients.

Ten consecutive ICU patients (2 female, 8 male) received daily antioxidant infusions including glutamine. Blood samples were drawn daily at 8:00 and 11:00 a.m. before onset of infusion therapy. After the end of infusion therapy, one sample was taken each day at 15:00 p.m. Each patient was monitored for 6 to 8 consecutive days. Plasma was obtained by centrifugation and was stored at -80°C until use. Malonic dialdehyde (MDA) was determined by HPLC and used as a reference method. Total antioxidant status (TAS, Randox, U.K.) was determined photometrically at 560 nm. Human antibodies against oxidised LDL (oLAb) were measured by ELISA (EliTec, Austria) in addition to our routine diagnostic program.

During the observation period, one patient (male, 39 years) died, while all others recovered. None of the three methods evaluated was clearly indicative for the fatal outcome, although trends could be observed. Out of more than 200 single determinations, less than 10% were within the normal range for MDA (<0.7 μmol/l)and TAS (1.3–1.77 mmol/l). Every third sample exceeded the normal range of MDA twofold (>1.4 μmol/l), and half of the samples gave antioxidant capacities of less than half of the normal range of TAS (<0.7 mmol/l). In samples taken after antioxidant therapy, there was a clear trend to higher TAS levels, but not high enough to strike the normal range. Concerning oLAb titres, compared with normal healthy subjects, we observed a significant trend towards lower titres, especially in septicemic patients.

These data convincingly support the hypothesis, that LPO is one very important factor in a great variety of disorders of ICU patients. Although none of the parameters evaluated was indicative for the fatal outcome of one patient, results obtained by these methods clearly showed the critical situation of these ICU patients and were to some extent indicative for therapeutical success. Due to their relative simplicity, TAS and oLAb can be adapted to routine laboratories with clinical chemistry and/or ELISA equipment. MDA measurement still requires a HPLC unit. From these results it is tempting to speculate upon importance of antioxidant therapies for the outcome of critically ill ICU patients, but further research is necessary to find clear and convincing solutions for that aspect.

Dedication

The authors dedicate this study to Prof. H. Esterbauer, who died in early 1997.