Tips for monitoring the position of a central venous catheter. How placement can go awry--even when the anatomy is normal.

Malpositioning of a central venous catheter can cause potentially life-threatening complications. Knowledge of thoracic anatomy and close attention to proper insertion technique increase the likelihood of, but do not ensure, proper placement. Selection of a right-sided venous entry site reduces the risk of malpositioning. The return of nonpulsatile, dark-colored blood is a strong, but not infallible, indication of venous placement. Do not assume that venous system valves preclude malpositioning. Use chest films to confirm accurate insertion. When these are equivocal, take simultaneous blood samples from a peripheral artery and the central line; the samples will have markedly different blood gas levels if the catheter is in a vein.