Why is a totally implantable venous access device necessary?

An intravenous port is used for all therapeutic activities in which intravenous access is periodically needed, such as infusion of chemotherapeutics or parenteral nutrition preparations.

Since it is already there, it can be used for drawing blood for laboratory tests, IVs, transfusion of blood products, pressurized injection of contrast agents during imaging studies - CT or MRI scans.

Venflons are not suitable intravenous accesses for this purpose:

they protrude above the skin, so care must be taken not to accidentally remove them from the vein - the ports are entirely hidden under the skin - they cannot be accidentally removed,
are easily kinked, causing obstruction or stopping the flow of the administered preparation - catheters of properly inserted ports are not kinked,
reduce the lumen of the vein (and therefore the flow of blood) and thus facilitate the irritating effect of the chemotherapeutic agent on the inner wall of the vein. A 0.5 mm radius venflon inserted into a 0.8 mm radius vein reduces its cross-sectional area (and therefore blood flow) by almost 40% - a 1 mm radius port catheter inserted into a 10 mm radius vein reduces its cross-sectional area by 1%,
when pressurized contrast is administered through a venepuncture during imaging studies, more pressure is generated than when using a port catheter with a larger inner diameter. In medicine, higher pressures mean a higher incidence of complications, such as extravasation of contrast at the site where the venepuncture is inserted into the vein.

Chemotherapeutics are very important in the treatment of cancer. For their effective use, a reliable and permanent intravenous access is necessary. Intravenous accesses are either peripheral or central. Peripheral, that is, in simple terms, those accesses where the catheter is a few centimeters long and placed in the veins of the forearms and hands. Central, that is, where the tip of the catheter, regardless of where it is inserted, is near the heart.

Peripheral accesses, so-called venflons, should not be used for more than a few days and should not be used to administer drugs that strongly irritate the blood vessel wall, that is, the therapy does not have to last for months. It is enough for it to be an irritant to the vessel wall, so it should not be used with peripheral access, a venflon.

A known problem during treatment with chemotherapeutics is inflammatory changes in peripheral veins. Veins are unable to withstand drugs so different from blood and physiological fluids. Irritation with aggressive infusions, for example, leads to inflammation and increasing obstruction of the veins. It is also easier for the chemotherapeutic drug to be extravasated outside the lumen of the vessel - the length of a port catheter in a vein is several centimeters, in a venoflon several millimeters. The consequence of extravasation can even be skin necrosis. It is typical for the venous system of the forearms, which has been destroyed by previous courses of chemotherapy, to be punctured at least several times, often more than a dozen times.

Therefore, as soon as the decision for chemotherapy is made and accepted, patients should be informed about the possibility of using an intravenous port. The port provides patients with the comfort of diagnosis and treatment. Drugs used in chemotherapy are much more acidic or alkaline than blood. They cannot be injected into veins such as the forearm, where there is little blood flow, without negative consequences.

In the photos above, the lesions after chemotherapy applied from access through a venflon. And it is not at all necessary to have had multiple infusions to develop inflammatory lesions of peripheral veins that are difficult to heal, painful for many weeks, or skin necrosis.

But the same very aggressive therapeutic substances can be administered into a vein where blood flow is several hundred (closer to a thousand) times greater. That doesn't mean their use will be free of systemic side effects, but local complications can certainly be avoided.

The port allows blood to be drawn for laboratory tests, and therefore there is no substantive justification for drawing blood for testing from a peripheral vein in a patient who has an intravenous port. The port is punctured once, the peripheral vein is punctured at least once as treatment progresses. More punctures means more pain.