An intravenous (IV) line is a thin tube inserted into a vein, typically in the arm or hand, designed to deliver fluids, medications, or nutrients directly into the bloodstream. While placing the line may cause a momentary sting, a sustained burning or stinging sensation during the infusion should not be ignored. This discomfort signals irritation to the delicate inner lining of the blood vessel, known as the endothelium. Understanding the possible causes is essential for ensuring the safety and effectiveness of the treatment.
Infusion Characteristics That Cause Discomfort
The chemical properties of the fluid being infused can directly irritate the vein wall, causing a burning sensation independent of the IV’s physical placement. One factor is the solution’s pH level, which measures its acidity or alkalinity. Blood plasma naturally maintains a tight pH range between 7.35 and 7.45. Infusates with a pH significantly outside this range, such as highly acidic medications, can chemically damage the vein’s inner cells, causing chemical phlebitis.
Many medications are formulated to be acidic to maintain stability. Infusions with a pH below 5 or above 9 are considered high-risk for peripheral veins. Highly acidic substances, such as certain antibiotics or concentrated electrolyte solutions, lead to irritation as the body attempts to neutralize the foreign substance. This chemical insult causes inflammation and the characteristic burning pain.
Another factor is the solution’s osmolarity, which is the concentration of dissolved particles within the fluid. Human blood plasma osmolarity is approximately 290 mOsm/L. Fluids that are significantly hypertonic (having a much higher concentration) can draw water out of the surrounding endothelial cells via osmosis. This cellular dehydration irritates the vein wall and causes a painful, burning sensation.
Solutions with an osmolarity greater than 600 mOsm/L are considered high-risk for infusion into smaller peripheral veins. The rate of delivery also influences discomfort. Infusing a high-risk solution too quickly can overwhelm the vein’s ability to dilute the fluid with blood, intensifying the irritation and burning feeling.
Site-Specific Issues and Vein Irritation
Physical complications at the insertion site are frequent causes of burning pain, often indicating the fluid is not flowing correctly. One common issue is phlebitis, which is inflammation of the vein wall triggered by mechanical, chemical, or bacterial irritation. Symptoms include localized pain, tenderness, warmth, and redness. The vein may sometimes feel like a firm, palpable cord beneath the skin.
A more immediate cause of burning is infiltration, which occurs when the IV catheter punctures or slips out of the vein. This causes non-vesicant fluid to leak into the surrounding subcutaneous tissue. The patient typically feels pain and a burning sensation at the site. The area around the IV site will also become noticeably swollen, puffy, and cool to the touch as the fluid pools outside the blood vessel.
Extravasation is a more serious form of infiltration where a vesicant medication (an agent capable of causing blistering and tissue death) leaks out of the vein. While both infiltration and extravasation cause swelling and pain, extravasation involves a more intense burning and stinging, with the potential for severe tissue injury.
Mechanical irritation from the catheter itself can also cause discomfort, especially if the line is placed in an area of flexion, such as the wrist or elbow joint. Constant movement can cause the plastic cannula to rub against the vein wall, leading to inflammation and pain. If the catheter size is too large for the chosen vein, it can also impede blood flow and increase the risk of phlebitis.
When to Alert a Healthcare Provider
A burning or stinging feeling during an IV infusion should always be reported to a healthcare provider immediately, as it is often the first sign of a complication. Never attempt to adjust the flow rate, remove the IV line, or apply compresses without consulting a nurse or doctor. Promptly communicating the discomfort allows the care team to assess the site and intervene before a minor issue becomes serious.
Several definitive warning signs signal a serious complication requiring urgent professional attention. These red flags include intense, unrelieved pain that goes beyond a mild burn, or any sign of severe swelling that causes the skin to look tight or shiny. Skin changes, such as blanching (abnormal paleness) or the skin feeling significantly cool to the touch, strongly suggest fluid is leaking into the tissue.
Other symptoms to report immediately include pus or discharge at the insertion site, which may indicate an infection, or systemic reactions like fever and chills. Although rare, difficulties breathing or chest pain could signal a widespread reaction requiring emergency medical evaluation. When alerting the provider, note the exact time the burning started and the specific medication or fluid received to help diagnose the underlying issue quickly.