Trace element status in critical illness polyneuropathy

Abstract

Critical illness polyneuropathy (CIP) is a term for neuromuscular weakness acquired by patients treated in a hospital intensive care unit (ICU). It is thought to affect almost half of all patients admitted and causes delayed weaning from mechanical ventilation, increased requirement for renal replacement therapy and increased length of stay in ICU. Although evidence is inconsistent, increased mortality has been shown in patients who experience CIP. The pathophysiology of CIP remains largely unexplained but it is known to be associated with sepsis and systemic inflammatory response syndrome (SIRS), which can lead to multi-organ failure. Recently the potential of antioxidants and minerals to modulate the immunological processes contributing to SIRS has been an area of increasing interest. Large scale trials are currently underway to establish if intravenous supplementation of selenium is of benefit in the ICU population. In certain clinical conditions it has been shown that enteral feeds enriched with specific trace elements, vitamins and lipids can improve outcomes for ICU patients. However, very little work has been done to specifically investigate any potential contribution of nutritional status to the development of CIP. The present study investigated if plasma levels of trace elements are different in CIP patients compared to matched controls. This retrospective case-control study investigated eighteen patients diagnosed with CIP at the Royal Liverpool University Hospital ICU over a thirteen-month period. Information collected included length of stay, mortality data, use of inotropic drugs and steroids, nutritional intake and biochemical markers including plasma levels of zinc, selenium and copper. Mean length of stay in ICU was more than doubled in CIP patients compared to controls (p=0.002). Patients with CIP were also less likely to survive their ICU admission compared with controls (p=0.034). No significant differences were found between any of the plasma trace element levels or biochemical markers apart from alkaline phosphatase levels, a marker of liver function. The retrospective nature of this study caused several limitations with the methodology, which made it difficult to draw firm conclusions from the results. Further research is required to investigate the role of trace elements and antioxidants in the pathophysiology and treatment of CIP.