Watching the waves Exploring the concept of fluid tolerance

This thesis investigated the venous excess ultrasound grading system (VExUS) and lung ultrasound (LUS) as determinants of fluid tolerance, alongside hormonal patterns in patients undergoing liver and pancreatic surgery.
In critically ill patients, VExUS grade ≥2 was relatively rare but strongly associated with the composite endpoint of AKI, renal replacement therapy and 30-day mortality (MAKE-30, OR 4.3), with moderate to excellent reproducibility. A systematic review of 32 studies confirmed that in cardiac patients, higher VExUS grades were associated with AKI (OR 4.44) and mortality (OR 3.17), whereas in critically ill patients these associations were less clear. VExUS demonstrated moderate to good accuracy in detecting elevated central venous and right atrial pressure.
Regarding fluid tolerance, most critically ill patients (63%) were fluid tolerant at admission. Pulmonary congestion was the most prevalent congestion type, while systemic congestion was rare, and both seldom occurred simultaneously, indicating that both must be assessed. Systemic congestion related to right ventricular dysfunction and pulmonary congestion to left ventricular dysfunction. After major gastrointestinal surgery, 37% of patients showed reduced fluid tolerance, which was associated with prolonged hospital stay (OR 3.29). Repeated ultrasound assessments proved feasible, though burdensome for some patients.
Concerning hormonal patterns, liver surgery patients showed increased aldosterone levels after resection, with higher ADH levels under restrictive fluid strategies, though neither related to fluid accumulation. Comparing liver and pancreatic surgery revealed similar RAAS activation and comparable copeptin levels, while NT-proBNP decreased after liver surgery but increased after pancreatectomy. Congestion occurred in 33% of patients and was associated with higher preoperative NT-proBNP levels, warranting future investigation.