An observational study on intracutaneous sodium storage in intensive care patients and controls

The development of ICU-acquired sodium disturbances is not fully understood. Alterations in non-osmotic skin sodium storage, hypothetically inflammation-driven, could play a role. To investigate this in critically ill patients we conducted a patient-control study with skin punch biopsies in patients with sepsis (n = 15), after coronary artery bypass grafting (CABG, n = 15) and undergoing total hip arthroplasty (THA-controls, n = 15) respectively, together representing a range in severity of systemic inflammation. Biopsies were taken within 24 hours (sepsis) and within 2 hours (CABG) after ICU-admission, and prior to arthroplasty. Biopsies were analysed for sodium content. In addition immunostainings and quantitative real time PCR were performed. The primary aim of this study was to detect possible differences in amounts of cutaneous sodium. The secondary aims were to quantify inflammation and lymphangiogenesis with concomitant markers. The highest amounts of both water and sodium were found in patients with sepsis, with slightly lower values after CABG and the lowest amounts in THA-controls. Correlation between water and sodium was 0.5 (p<0.01). In skin biopsies in all groups comparable amounts of macrophages, T-cells and lymph vessels were found. In all groups comparable expression of inflammation markers were found. However, higher mRNA transcript expression levels of markers of lymphangiogenesis were found in patients with sepsis and after CABG. The conjoint accumulation of water and sodium points towards oedema formation. However, the correlation coefficient of 0.5 leaves room for alternative explanations, including non-osmotic sodium storage. No signs of dermal inflammation were found, but upregulation of markers of lymphangiogenesis could indicate future lymphangiogenesis.