The sensation of burning, stinging, or discomfort during an intravenous (IV) infusion is a common experience. This discomfort signals that the fluid or the catheter is irritating the delicate inner lining of the vein, known as the endothelium. While uncomfortable, this reaction is often temporary and not a sign of a catastrophic problem. Understanding the causes, which are broadly categorized as chemical or mechanical, helps address the issue quickly.
Chemical Properties of the IV Fluid
The body’s internal environment is highly regulated, requiring any fluid introduced into the bloodstream to closely match blood chemistry. Two main properties of the IV solution, its pH and its osmolarity, can cause irritation if they deviate too far from the body’s normal range.
pH Imbalance
The pH of human blood is tightly maintained between 7.35 and 7.45. Chemical phlebitis, or vein inflammation, occurs when the infused fluid is significantly more acidic or alkaline than the blood. Solutions with a pH outside the range of 5 to 9 irritate the endothelial cells lining the vein wall, causing a burning sensation. Acidic medications, such as the antibiotic vancomycin or the heart medication amiodarone, are common causes of this irritation.
Osmolarity
Osmolarity refers to the concentration of particles dissolved within the fluid. Normal blood plasma has an osmolarity of approximately 290 milliosmoles per liter (mOsm/L). If an IV solution is hypertonic (highly concentrated), it pulls water out of surrounding cells, causing endothelial cells to shrink. This rapid fluid shift triggers pain and a burning feeling. Highly concentrated fluids, such as Dextrose 50% or certain nutritional solutions, often exceed the recommended limit of 600 mOsm/L for peripheral veins, leading to discomfort.
Conversely, solutions that are too hypotonic (less concentrated) cause cells to absorb water and swell, disrupting cell balance and causing irritation. Fluids with extreme osmolarity can damage the vein wall, resulting in inflammation.
Mechanical and Site-Specific Irritation
The physical presence and location of the catheter can cause irritation and a burning sensation, independent of the fluid’s chemistry.
Infiltration and Extravasation
One frequent cause of localized pain is infiltration, which occurs when the IV catheter slips out of the vein. The fluid then leaks into the surrounding subcutaneous tissue. This accumulation stretches the tissue and nerves, causing discomfort, swelling, and a cool feeling at the site. A more serious issue is extravasation, which involves a vesicant (tissue-damaging medication) leaking out of the vein. The burning sensation is often more intense because the leaked fluid actively damages the surrounding soft tissue.
Catheter Size and Infusion Rate
The catheter itself can cause mechanical phlebitis, which is inflammation resulting from the catheter rubbing against the inner wall of the vessel. This irritation is more likely if the catheter is too large for the vein or if the IV is placed near a joint, where movement causes friction. The rate and temperature of the infusion also contribute to temporary discomfort. Infusing a cold solution, such as refrigerated blood products, can cause brief stinging as the liquid hits the warmer vessel lining. Rapid infusion into a small vein can increase pressure, leading to a temporary ache or burning sensation.
What to Do When Your IV Burns
If you feel a burning, stinging, or aching sensation at your IV site, notify your nurse or healthcare provider immediately. Do not wait for the discomfort to subside, as early identification of issues like infiltration prevents further tissue irritation. You should avoid manipulating the IV line or trying to adjust the catheter yourself.
The healthcare provider will assess the site for signs of infiltration, such as swelling, firmness, or temperature changes. They will check the infusion rate and may temporarily stop the flow to evaluate the problem. If infiltration is confirmed, the IV must be removed and restarted in a different vein.
To alleviate discomfort, the nurse may slow the infusion rate if the issue is due to a concentrated or irritating medication. This allows the body’s natural blood flow to dilute the solution more effectively. For mechanical or chemical irritation, they may apply a warm or cool compress to soothe the inflamed vein.