The concern is the injection of a hypertonic contrast agent considered to be vesicants into the deep upper arm location of a midline catheter. Deep veins could mean that fluid in the tissue may go undetected and potentially damage large arteries and nerves in the area. Many clinicians report that a midline catheter will not typically produce a blood return, thus eliminating one component of a complete clinical assessment of catheter patency.
One the positive side, evidence is showing that longer catheters are needed when ultrasound is used to access deep vessels. Higher rates of infiltration/extravasation are reported when deep veins are used, even with 1.8 and 2 inch long catheters. This may indicate tht a 3 inch long catheter could be safer than a 2 inch catheter in the veins of the upper extremity.
At the present time, there is a distinct need for more research on midline catheters and the midline tip location. I am aware of 2 simple descriptive clinical studies on the newer midline catheters labeled for power injection. These studies included a brief statement about small numbers of patients having the midline catheter used for contrast injection. These studies did not include details of the types of contrast agents used, the rates of injection, or the dwell time of the midline catheter when the contrast was injected.
Extravasation with contrast agents happens, although it is reported to have very low rates usually less than 1%. In my experience as an expert witness, I have seen about 15 cases of contrast extravasation however all have involved short peripheral catheters inserted in the hand, wrist or antecubital fossa. No cases have involved a midline catheter or midline tip location. The bottom line is we need more data for these critical clinical decisions.