Assessing Vascular Tone and Fluid Balance in Septic and Cardiogenic Shock: A Feasibility Study on Skin Water Loss as a Diagnostic Tool.

Background/Objectives: Fluid management in shock remains a clinical challenge, with ongoing debate about optimal guidance. Despite advanced technologies, fluid balance assessment is often inadequate. The SkInShock study investigated whether transepidermal water loss (TEWL) measurements could improve fluid balance estimation and serve as a non-invasive marker of vascular tone in patients with septic or cardiogenic shock. Methods: In this prospective single-center feasibility study (DRKS00027981), TEWL was measured daily in eight mechanically ventilated patients using a Tewameter® (Courage+Khazaka, Cologne, Germany), which quantifies transcutaneous water evaporation. Total daily skin water loss was calculated either via direct TEWL measurements or an estimation formula (6 mL/kg/day + 20%/°C deviation from 37 °C). Systemic vascular resistance index (SVRI) was measured simultaneously using PiCCO® technology (Pulsion Medical Systems, Munich, Germany) to evaluate the relationship between TEWL and vascular tone. Results: TEWL values were consistent across most body sites, except the forehead. TEWL-based estimates of skin water loss were significantly lower than formula-based estimates (p < 0.01). Formula-based values overestimated water loss at low TEWL levels and underestimated it at higher levels, with deviations reaching ±100%. While absolute TEWL values did not correlate with SVRI, intra-individually normalized values showed a significant negative correlation, indicating that higher skin water loss corresponded to lower vascular tone. Conclusions: TEWL measurement is feasible in ICU patients and may enhance fluid balance assessment and vascular tone monitoring. Our preliminary findings indicate that this non-invasive method could complement current diagnostics but warrants further investigation in larger cohorts.