The phenomenon of direct aspiration and its possible clinical applications

Background: Critically ill patients in intensive care units (ICUs) often require organ support, including mechanical ventilation, vasopressors, and dialysis. Central venous catheters (CVCs) are commonly used for drug administration, while central dialysis catheters (CDKs) enable continuous renal replacement therapy (CRRT). This thesis investigated the potential phenomenon of direct aspiration of a drug infused in a CVC into the CDK during CRRT, leading to unintended clearance, and explored its clinical implications and also physicians’ catheter insertion practices. To achieve this, experimental animal models and a cross-sectional survey study were employed. Methods and Results: Study I examined the impact of catheter placement on drug concentration and vasopressor requirements. Results showed lower antibiotic concentrations and a twofold increase in noradrenaline demand, during CRRT, when CVC and CDK were placed in the same vessel compared to separate vessels. Study II assessed antibiotic clearance under endotoxaemic conditions, demonstrating higher clearance in CRRT when both catheters were in the same vessel. Study III explored how different CVC-CDK tip distances influenced clearance, during CRRT. The lowest clearance was observed when catheter tips were parallel or when the CVC tip was closer to the heart than the CDK. Study IV investigated European ICU physicians’ catheter placement preferences. The right internal jugular vein was the preferred site for both CVC and CDK. Ultrasound was frequently used for insertion but less often for tip position confirmation. Notably, 70% of respondents expressed concerns regarding catheter tip positioning in the same vessel, and 30% had suspected drug aspiration from a CVC into a CDK during their clinical careers. Conclusion: Direct aspiration of drugs from a CVC into a CDK can occur during CRRT, potentially affecting drug clearance. European physicians prefer the right internal jugular vein for placement regarding both catheters, with ultrasound frequently used for insertion but less often for tip confirmation.