Sonographic position monitoring of central venous catheters by microbubble-injection in real time: development of a new procedure

Abstract

Background: Central venous catheter placement requires immediate confirmation of its orthotopic position in the central vena cava to avoid arterial or paravasal infusions which could potentially harm the patient. The correct position is usually verified by chest x-ray or ECG. Echocardiography might offer a fast and safe alternative. This study aimed at developing a new non-invasive, ultrasound-based procedure to determine the orthotopic position of Central Venous Catheters (CVC) position by sonographic detection of injected Microbubbles (MB) Methods: With approval of the local ethics committee 95 patients with 98 CVC and 5 peripheral catheters were examined. The appearance of MB in the right heart can be observed after injection of agitated saline in the subcostal four-chamber view. MB are hyperechogenic and dissolve later. The time from injection at the catheter to the appearance in the RV can be recorded by M-Mode registration allowing an exact measurement independent of user interaction and reaction. To determine positioning, time of appearance of MB was recorded. The transit time was correlated with radiologically confirmed catheter positions. A self assessment of the procedures practicability was performed on a linear anologue scale (0-100%). Results: We report a total of 95 Patients (65.0+/-18 years, 57% male). The jugular vein was used in 85 and the subclavian vein in 13 cases. The main diagnoses requiring catheter placement were pneumonia (n=49), aortic valve reconstruction (n=9), myocardial infarction (n=6), heart failure (n=6), gastrointestinal bleeding (n=6) or others (n=9). In 95 patients with radiologically confirmed orthotopic position MB appeared in the right heart in less than one second after injection with a reliability of 100%. In 3 patients, quantitatively measured appearance of MB was even below 0.5 seconds. In 5 patients with peripheral venous catheters MB were observed later than 2 sec after injection and in one patient with a heterotopic CVC within 1-2 seconds after injection. Duration of the procedure was 146 (111) seconds (mean, (SD)). Physician's impression of practicalness was 91% (linear analogue self assessment). Conclusion: Ultrasound-based real-time position monitoring of CVC by this new description of the MB-injection technique has the potential to serve as an alternative to X-ray or other methods. Appearance of MBs in less than one second can be assumed to predict orthotopic position with high accuracy. Appearance of MB in more than two seconds indicates malpositioning. Transit times between one and two seconds require additional X-ray confirmation.