We present bedside insertion of a PICC into a patient with BMI 84.8 kg/m2 using a Sherlock 3CG® TCS. PICC is suitable for critically ill patients due to its advantages over CVC, including less risk of procedure-related complications and bloodstream infection [5]. A PICC is generally inserted via a cephalic or basilic vein of the upper arm, but it is sometimes displaced due to the long detention distance, so malposition of the catheter tip is one of the most common complications [6, 7]. Therefore, PICC is generally placed while being confirmed under fluoroscopic visualization. However, since it was a risk for this case to be transferred from the ICU, a PICC was inserted at the bedside using Sherlock 3CG® TCS.
The Sherlock 3CG® TCS is composed of an external magnetic sensor at the catheter tip and an IC-ECG guidance system. The magnetic sensor guidance system graphically shows the catheter tip on a bedside monitor. Therefore, catheter malposition can be recognized at an early stage if it strays into the right internal jugular vein or left innominate vein. As the catheter tip advances into the inferior vena cava, the P wave of the IC-ECG increases as it approaches the CAJ. A negative deflection appears in the P wave if the catheter tip passes through the CAJ, so the PICC should be placed at the highest P wave which is the appropriate insertion distance. Combination of these two systems present capacity to be inserted PICCs without using fluoroscopy [4].
The detectable depth of the magnetic sensor is 3–11 cm according to the standard limit. In our case, the distance from the chest wall to the CAJ was about 15 cm on the computerized tomography scan. Additionally, when a patient’s chest is not flat, the sensor will rest at an angle, causing an effect known as parallax. The difference between the point of view of the sensor and the user can be several centimeters. Therefore, in our case, the magnetic guidance system did not work due to the thick and angled subcutaneous tissue in the precordium. On the other hand, since the IC-ECG had worked accurately, we placed the catheter tip where the P wave is highest. It has been reported that an X-ray for confirmation when using Sherlock 3CG® TCS is unnecessary [8], but we confirmed that the tip position by the chest X-ray because the magnetic sensor did not worked. Success rates have not been reported when either the magnetic guidance or the IC-ECG failed to work properly, but in this case, the catheter tip was placed in the appropriate position.