Plasma levels of high-energy compounds compared with severity of illness in critically ill patients in the intensive care unit

Abstract

Background: Plasma metabolic changes have been shown to reflect deterioration of the energy state of tissue in studies in animals. This study evaluates whether high-energy compounds and their metabolites in plasma reflect the clinical condition and predict outcome in critically ill patients.

Methods: Thirteen critically ill patients with major trauma, severe septic shock, or cardiogenic shock (initial Acute Physiology and Chronic Health Evaluation [APACHE] II score > or = 16) were studied. The APACHE II score was recorded daily until discharge from the intensive care unit or death. The plasma contents of adenosine triphosphate, adenosine diphosphate, adenosine, inosine, hypoxanthine, creatine phosphate, creatine, uric acid, and lactic acid were determined daily. Fifteen healthy volunteers were used as control subjects.

Results: All patients with an APACHE II score of 12 or less at some time during their stay in the intensive care unit survived (n = 4); all patients with a score of 26 or higher died (n = 5). The initial APACHE II median score for survivors was 21 (range 16 to 25; n = 7) and for nonsurvivors 24 (range 17 to 28; n = 6) (difference not significant). The final APACHE II score for the survivors was 11 (range 3 to 16) and for nonsurvivors 29 (range 20 to 47) (p < 0.01). The plasma metabolites were grouped according to the patients' APACHE II score of the day. There was a positive correlation between the severity of metabolic derangement and the APACHE II score. The plasma contents of adenosine triphosphate and creatine phosphate were depleted with higher APACHE II scores (p < 0.01), whereas creatine and uric acid levels increased progressively (p < 0.001). The levels of adenosine, inosine, hypoxanthine, and lactic acid were elevated significantly in critically ill patients.

Conclusions: Grouping patients with successively higher APACHE II scores revealed specific patterns of altered plasma metabolism, possible reflecting different levels of tissue adenylate energy charge. However, neither the initial individual APACHE II score nor any initial plasma metabolic level had any prognostic value in this group of critically ill patients, although the deterioration of the physiologic parameters was coexistent with specific metabolic changes.