Chemotherapeutic agents are administered to patients both in monotherapy and in combination - according to a regimen established for the specific disease entity, in repeated cycles. Typically, drugs are selected for their different mechanisms of action to improve the efficacy of therapy. It is understood that combination therapy carries a higher risk of side effects.

Routes of administration and risk of complications

Cytotoxic drugs come in oral form, can be administered subcutaneously (e.g. cytarabine, methotrexate, bleomycin), directly into the medullary canal (for CNS tumours, e.g. methotrexate). Infusions into body cavities are also practised, e.g. urothelial cancers - intravesical (e.g. mitomycin C), primary and secondary peritoneal cancers - cisplatin, doxorubicin. Before and during chemotherapy, adverse effects resulting not only from the drug itself, as a highly toxic substance, but also from the route of administration should be considered. The subcutaneous route is only suitable for drugs that do not have a local irritant effect and that can be contained in the dose due in a small volume. Drugs administered into the medullary canal must not be neurotoxic. Perfusion of body cavities, e.g. intraperitoneally, may not give early general adverse effects, as the drugs enter the systemic circulation in minimal concentrations. However, adverse effects are encountered at distant follow-up, e.g. states of chronic gastrointestinal obstruction, which sometimes require emergency surgical intervention (related to tissue scarring during healing of limited inflammation caused by local toxicity of cytostatics). The choice of intravenous route of administration, statistically the most common, is also associated with a wide spectrum of complications. The infusion of the drug itself may cause hypersensitivity reactions of varying degrees of severity in the patient, unrelated not to the toxic potential of the drug, but to the individual organism's reaction. The first symptom may be localised reddening of the skin near the site of injection, with rash and tissue swelling. As the reaction intensifies, general symptoms may become apparent: a drop in blood pressure, bronchospasm with a feeling of dyspnoea and anxiety, angioedema. These result from the mobilisation of natural immune mechanisms - reactions that can also occur with the administration of common drugs from other groups, e.g. analgesics or antibiotics. Of the local reactions to drug administration, it is important to mention phlebitis - a sterile, toxic mechanism that increases the risk of extravasation during subsequent drug infusions.

Extravasation as a complication

Cytostatic extravasation is the unintentional seepage or leakage of drug into the perivascular space during or shortly after an intravenous infusion. The consequences of extravasation can vary - depending on the drug administered, its concentration, the volume extravasated, the location of the cannula and the rate of administration as well as the speed of the medical staff's response to the event. Many factors are known to increase the risk of extravasation. Of the most relevant, the technical ones are the site of injection, the method of vessel cannulation and the injection technique.

Technical aspects of injections

The anatomically optimal site of administration is the forearm. Visible, wide, easily accessible veins and sufficient distance from the joints ensure safety and comfort for the patient. In addition, the well-developed subcutaneous tissue protects against possible nerve and tendon damage in the event of leakage. A particularly unfavourable area that should be avoided, especially when administering highly irritating cytostatic drugs, is the inner side of the wrist. The vessels, nerves and tendons run very superficially here and are not protected by the surrounding tissues, increasing the risk of their damage if the drug leaks into the tissues. In addition, the ulnar flexure, the foot area and other vessels in close proximity to tendons, nerves or arteries should be avoided. The quality of the patient's venous network itself influences the increased risk of extravasation. The elderly have fragile veins with small diameters and often an atherosclerotic remodelled wall-very susceptible to damage. Ulcerations in this group of patients can be extensive, involving long stretches of the vessel together with surrounding tissues. Even if there is no direct damage to the vessel wall, its low strength combined with increased pressure during drug administration may result in rupture, microleakage - small, but sufficient to initiate local necrosis. It is also important to consider the condition of the tissues in the area of the planned injection - poor, e.g. after trauma, local irradiation for oncological or other indications, in the course of systemic diseases, with lymphoedema (e.g. women after radical mastectomy), scarring.