Optimizing ICU patient care through ultrasound: Central venous catheterization and lung ultrasound

This thesis explores how ultrasound can improve interventions and diagnostics for ICU patients, focusing on two main themes: complications of central venous catheterization (CVC) and the role of lung ultrasound in critical care. Central Venous Access CVC is essential in critical care but carries risks of mechanical, thrombotic, and infectious complications. Misplacement and pneumothorax are critical concerns, traditionally detected using chest X-ray. However, ultrasound may offer a faster, safer, and radiation-free alternative. A systematic review and a multicenter study (Chapters 2 and 3) confirmed that ultrasound has high specificity (0.99) and reasonable sensitivity (~0.70) for detecting CVC malposition and pneumothorax. Several ultrasound protocols were assessed for guiding CVC placement. One approach involves a second operator visualizing the guidewire in the heart, ensuring correct placement before advancing the catheter. Another method uses a single operator and a micro-convex transducer to track guidewire progression via the right clavicular fossa, allowing efficient verification of CVC placement. A third technique utilizes contrast-enhanced ultrasound post-insertion to confirm catheter positioning. While effective, this approach does not allow immediate correction of malpositioned CVCs. The study found a lower-than-expected CVC malposition rate (3.3%), raising questions about whether routine verification is always necessary. Beyond mechanical complications, catheter-related thrombosis is a frequent but often incidental finding. Chapter 4's observational study found a high prevalence (56%) and incidence (65.7 cases per 1,000 catheter days) of thrombosis. Surprisingly, thrombosis was not linked to increased mortality but was associated with pulmonary embolism. This challenges current management strategies, suggesting that anticoagulation should be patient-specific. COVID-19 patients demonstrated a significantly higher risk of catheter-related thrombosis, likely due to a hypercoagulable state (Chapter 5). A multicenter case-control study found an 18-fold increased risk, which was mitigated by higher prophylactic anticoagulation. Similarly, Chapter 6 showed that ICU patients with COVID-19 had an increased risk of catheter-related infections, particularly when in a prone position. This highlights the need for stricter infection control protocols. Ultrasound and the Respiratory System Lung ultrasound is an emerging diagnostic tool for respiratory failure in ICU patients. Chapter 7 evaluated a 6-zone protocol against CT, finding it reliable for detecting consolidation and pleural effusion, though slightly less accurate for pneumothorax. A 12-zone protocol provided minimal additional benefit, reinforcing the efficiency of the 6-zone approach. The reproducibility of B-line quantification (Chapter 8) was evaluated, revealing significant variability between observers and transducers. Standardization is necessary to ensure consistency in clinical practice. Chapter 9 examined pneumonia diagnosis in ICU patients with lung consolidation. The study found that dynamic air bronchogram had high specificity, while color Doppler pulsatile flow had high sensitivity. A combined approach significantly improved diagnostic accuracy. Finally, Chapter 10 investigated a holistic ultrasound protocol to predict extubation failure. While the approach showed limited predictive value, it challenged previous assumptions about diaphragm thickening fraction as a predictor. Overall, this thesis highlights the potential of ultrasound to enhance ICU diagnostics and interventions, particularly in CVC placement and lung pathology, while also identifying areas requiring further optimization.