wikipedia entry on Central Line for Leukemia
Comments from Wilbur Lam, MD, PhD on the importance of monitoring and keeping the Central Line clear.
- How oncologists and cardiologists use lines are completely different. For an oncologist (especially pediatric), the central line is quite literally the lifeline of the patient. If the line doesn’t work, patients can’t get chemo OR pain meds OR (often) food (they’re stomach is so blasted from the chemo the only nutrition they can get is intravenous). So, If the line doesn’t work, the oncologist is worthless. Once the line doesn’t work, we have to call the surgeon to put in a new line and that can take days and another trip to OR with general anesthesia – so there are issues of cost, efficiency, and safety.
- I agree that’s easy to tell when the line is clogged – yes, the nurse can’t draw/push fluid. But that’s not the point, the point is to see if we can predict malfunction before it happens so we can make provisions: use meds (including tPA), give the surgeons a heads-up, etc to minimize the time without a functional line
- However, I completely disagree with him on the tPA point, at least with my patient population. The stuff works only a minority (~30%) of the time no matter how long we give and we can get to dangerous doses sometimes. It might have to do with the fact that we have to use smaller lines and they are much easier to completely obstruct. As you are stating, tPA is likely to be more effective in the case of partial rather than complete obstruction, establishing the need for the device we are planning. But currently, we have no way of knowing until it’s too late. If we knew there was partial obstruction, than that could be an early indicator to give tPA. Finally, in patients with cancer, there is a known phenomenon that they are more predisposed to clotting (there’s a risk for bleeding as well – which I can go into later – but this may prevent surgery for another line). This clotting predisposition is due to a number of reasons including their chemo, their baseline level of inflammation, and other cormorbidities related to their disease.
I think the point here, because there are nuances, is for us to initially focus on the pediatric and pediatric cancer population, at least in part because that’s the setting I know and operate in. There, the need is clear – no question about it; I face this almost every day. Once we get going, I think it would be easy to extend to other subspecialties, but there are subtleties in the ways different types of docs use and view these lines. Remember, it ain’t no big deal for an adult cardiac patient to have a line removed (you can take it out and put it in an a new one even in the patient’s room). But for a kid with cancer, this is a huge problem – without a functional line, they might as well just go home without any treatment for their cancer or their pain.
Monitoring Options:
- Standard Radiologic Procedures: CT, MRI, US, X-ray, etc. Here, US has the best portability. Unclear if contrast is adequate or if views are adequate to monitor clot in Central Line. Should be ruled out before building new CL or before building a new scanner.
- Smart Central Lines: It is certainly feasible to embed sensors (assuming these don't increase the risk of clotting!) into Central Lines. We need a sensor that can easily distinguish saline, blood, and clot. Could be conductivity, salinity, pH, viscosity, opacity, acoustic reflection coefficient, etc. Many sensors would allow for higher spatial resolution (albeit in 1D) and excellent normalization.
- A Dedicated Scanner: One could imagine creating a 1D (A-mode) Ultrasound scanner that displays acoustic reflection coefficient versus distance along the central line lumen. 1D imaging greatly improves dynamic contrast of the changes, by resolving the clot at each spatial position.
The thesis below worked on guided waves. Note that the waveguide (the plastic tube) must satisfy certain conditions at the frequency of interest to satisfy total internal reflection and to avoid excessive losses during the roundtrip echo. In particular, it appears a very low shear modulus plastic would be key.