Intravenous (IV) therapy involves placing a plastic cannula directly into a vein to deliver fluids, electrolytes, blood products, or medications straight into the systemic circulation. This route bypasses the digestive tract entirely, offering immediate bioavailability compared to oral or subcutaneous administration.
Common clinical indications include:
Successful cannulation depends on understanding peripheral vein structure. Veins feature three tissue layers: the tunica intima (smooth inner lining), the tunica media (middle muscular and elastic layer), and the tunica adventitia (outer supportive connective tissue). Unlike arteries, veins possess one-way valves that prevent backflow against gravity and have thinner, less muscular walls.
The ideal peripheral veins for cannulation are located in the upper extremities. The dorsal venous network of the hand, the cephalic and basilic veins of the forearm, and the median cubital vein are primary choices. Lower extremity veins are generally avoided in adults due to an increased risk of deep vein thrombosis and sluggish circulation.
Gathering the correct equipment before approaching the patient prevents unnecessary delays and contamination. Essential supplies include a peripheral cannula of appropriate gauge, a tourniquet, antiseptic skin prep (like chlorhexidine or alcohol), sterile gauze, transparent dressing, an extension set or infusion tubing, and prescribed IV fluids.
Infusion solutions are categorized by tonicity:
Before initiating IV therapy, nurses must verify the medical prescription, check patient identification, and assess for allergies, particularly to latex, adhesives, or antiseptics. Assess the patient's dominant hand, previous IV sites, and any circulatory or lymphatic impairments, such as a prior mastectomy or dialysis fistula, which forbid cannulation on that specific limb.
Psychological preparation is equally vital. Explain the procedure simply, acknowledge any anxiety, and position the patient comfortably in a semi-Fowler's position or lying flat if they tend to vasovagal during punctures.
Ensuring the correct volume of fluid is infused over the prescribed duration requires precise mathematical calculation. Nurses use gravity infusion sets with specific drop factors (drops per milliliter), typically 15 drops/mL, 20 drops/mL, or micro-drip tubing at 60 drops/mL.
The standard formula for gravity flow rate is: $$\text{Flow Rate (gtt/min)} = \frac{\text{Total Volume (mL)} \times \text{Drop Factor (gtt/mL)}}{\text{Time in Minutes}}$$
Alternatively, when using electronic infusion pumps, the rate is programmed directly in milliliters per hour (mL/hr). Nurses must routinely monitor infusion pumps and gravity drip chambers to prevent accidental fluid overload or run-dry situations.
Intravenous therapy carries local and systemic risks that require vigilance.
Local complications:
Systemic complications include fluid overload, bloodstream infection, and air embolism. Prevention centers on strict aseptic technique during insertion, regular site inspections, rotating peripheral sites every 72 to 96 hours according to hospital policy, and immediate removal of the cannula at the first sign of complications.
Maintaining an open, clean IV line preserves vascular access and minimizes infection. Dressings must remain clean, dry, and intact; replace them immediately if they become soiled or loose. Tubing changes should follow institutional infection control guidelines, typically every 72 to 96 hours for continuous infusions.
When therapy is complete or complications arise, discontinue the IV by clamping the tubing, gently removing the dressing, and pulling the cannula out parallel to the skin. Apply immediate pressure with sterile gauze for at least two to three minutes until bleeding stops, then secure with a clean bandage. Inspect the removed catheter tip to ensure it is intact.