Agitated Saline Versus Chest X-ray for Determination of Correct Position of Central Venous Catheter: a Non-inferiority Study

Central venous lines (CVL) are placed in various in-hospital settings like operation theaters, emergency departments, oncology departments, and intensive care units for various purposes. Like any invasive procedures, placement of central lines is invariably associated with certain risks of inadvertent complications which are often life-threatening which occur because of the intricacy of the structures around the vascular access site like pleura, arteries, nerves, heart, etc. Measures such as landmark guidance, electrocardiographic guidance, fluoroscopy/C-arm-guided, and recently ultrasound image guidance have been in place to prevent and/or minimize the occurrence of such complications. Although the incidence of such complications have decreased considerably4, the rates have not reached the nadir.

Failure of confirmation of the correct placement of a CVL can have serious consequences. The consequences of an inadvertently misplaced catheter are grave for the patient be it the failure to elicit the vasopressor effect, unnecessary delay in starting of caustic substances like hypertonic fluids, parenteral nutrition, concentrated agents, etc., these will ultimately increase the morbidity and mortality. Thus, it becomes imperative that we confirm the accurate placement of CVL before infusing anything through these lines.

The confirmation of accurate placement of CVL is usually done by performing a post-procedure chest x-ray (CXR) which is done at the point of care if possible like in ICU or after shifting of patient to a post-operative ward in an operation theater setup. The most important constraint in obtaining CXR after CVL placement is the considerable amount of time it takes before a film is obtained even in center where there is a dedicated portable CXR for that purpose. For CVL placed in the operating theater, it is not always possible to do a portable CXR immediately after the procedure and at many times we have to immediately start infusion/medications through it even before confirmation of their proper placement. Secondly the very well-known problem of radiation hazard is a potential deterrent to the use of CXR each time a CVL is placed. When a large volume ICU is compared, the risk of radiation is inadvertently extended to all of the patients even though lines are placed in some. The hazard of the radiation to the ICU and ED staffs is always a concern considering the difficulty they face in escaping the hazard when they are taking care of sick patients. Thirdly, it is difficult to obtain an accurate CXR film in critical care unit setups where the patient are sometimes unable to hold breaths at inspiration (for the proper x-ray film) and the film so obtained may not be reliable enough to read. Fourthly, the overall costs in obtaining CXR for each and every single central lines placed will add to the overall healthcare costs at a time when the investigators are looking for reasons to cut down on health expenses.

Considering the fact that these lines are placed under ultrasound guidance, the rate of inadvertent complications are very few. But subjecting every single individual to an x-ray cannot always be justified. Nevertheless, this is not to say that central lines should not be confirmed for their proper placement, but certainly there is an imminent need of a simple, reliable, and more cost effective alternative to CXR. The very same ultrasound machine at point of care can be utilized for this purpose addressing most of the limitations of the CXR.

With simple, directed teaching it is possible for anyone with basic knowledge in ultrasound to do a focused point of care ultrasound to evaluate the accurate placement of CVL. This simple approach has several potential benefits. The first one being the saving of precious post-procedure time that is lost in obtaining a chest x-ray. The potential radiation hazard due to CXR is virtually eliminated. The same ultrasound can also be utilized for scanning the thorax to exclude pneumothorax and hemothorax and avoid potential delay in their management. If the sensitivity and specificity of ultrasound in accurately delineating the position of CVL is comparable to the chest x-ray, then obtaining of chest x-ray for confirmation can virtually be eliminated.