[Positioning of central venous catheters using ECG]

The position of a central venous catheter has to be controlled. As a supplement to radiography of the chest the position of the catheter tip can be documented by means of ECG. The ECG is recorded with the catheter tip functioning as one of the electrodes. If the catheter tip is situated in the right atrium the ECG will record an elevated P-wave. When the catheter is pulled back into the vena cava superior the atrial-P will assume a normal shape. The position of the catheter tip correlates with the morphology of the P-wave. An ECG recording performed during insertion of the catheter can be used to achieve correct positioning of the catheter to start with and thereby reduce the frequency of having to replace wrongly positioned catheters. Intraoperatively the ECG recording is a practical method of achieving correct and extracardial placement of the catheter tip.