Intravenous

Injection

Intravenous therapy, often referred to as IV therapy, is a medical procedure that involves the direct introduction of liquid substances into a person's vein. The term "intravenous" is derived from the Latin words meaning "within a vein". This therapy can either be intermittent or continuous; in instances of continuous administration, it is termed as an intravenous drip.

IV treatment

The primary advantage of the intravenous route over other routes of administration is its rapidity. It is the quickest way to disperse fluids and medicines across the body. Intravenous methods are exclusively employed for specific treatments, such as blood transfusions and lethal injections.

Types of Intravenous Access Devices

Different intravenous access devices cater to various medical needs and situations. Here's a comprehensive breakdown:

1. Needle and Syringe

The most basic form of IV access, it involves a syringe attached to a hollow needle. The needle penetrates the skin to access a vein, allowing the syringe's contents to be injected directly into the bloodstream. Typically, an arm vein, particularly one of the metacarpal veins, is used. Often a tourniquet is used initially to enlarge the vein. This method is commonly adopted for intravenous drug use, especially for euphoriants like heroin, or when a patient needs to self-administer intravenous medication at home. It's also handy for immediate delivery of essential medications in emergencies. However, in regulated health care environments, this method is rarely used as it provides only a single dose of medication.

USMC IV

2. Peripheral IV Lines

Predominantly used in hospitals and paramedic services, the peripheral IV line involves a short catheter inserted through the skin into a peripheral vein. Peripheral veins exclude those located in the chest or abdomen. Veins in the arm and hand are generally used, but occasionally, leg and foot veins or the scalp veins in infants might be selected. The external portion of the catheter can be linked to a syringe or an IV infusion line. The size or gauge of the catheter varies, with 16-gauge being a general-purpose line for blood transfusions and 18-, 20-, and 22-gauge serving as all-purpose lines for various medical procedures.

Blood Donation

3. Central IV Lines

A Central IV line features a catheter that ends within a major vein, such as the superior vena cava, inferior vena cava, or the right atrium of the heart. Benefits include:

Swift delivery of fluids and medicines, ensuring instant distribution throughout the body. Ability to deliver multiple medications simultaneously, even if incompatible in a single tube. The possibility to monitor vital variables like central venous pressure. However, they are associated with higher risks, including bleeding, bacteremia, and gas embolism. There are multiple types of central IVs, differentiated by the path the catheter takes to reach the vein.

Peripherally Inserted Central Catheter (PICC)

A PICC line is introduced into a peripheral vein and then gently pushed upward until the catheter resides in the superior vena cava or the right atrium. It is beneficial for patients requiring prolonged treatment, though it does have some limitations due to its diameter.

Central Venous Lines

These are types of catheters that access central veins directly. Examples include Hickman line or Broviac catheters, which are designed to reduce infection risks.

Implantable Ports

Often known by brand names like Port-a-Cath or MediPort, these are central venous lines that do not have an external connector. They are especially beneficial for patients needing long-term intermittent treatments.

Methods of Intravenous Therapy

The IV therapy can be classified based on the form of delivery:

Intravenous Drip

The continuous infusion of liquids, with or without medication, using an IV access device is known as an intravenous drip. It is used to rectify dehydration, electrolyte imbalances, administer medications, or conduct blood transfusion.

Types of IV Fluids

IV drips utilize two primary types of fluids: crystalloids and colloids. Crystalloids are solutions containing mineral salts or other water-soluble molecules, while colloids have larger, insoluble molecules, e.g., blood. The choice of fluid depends on the patient's specific needs and the chemical properties of the medication being administered.

For detailed compositions and effects of common crystalloid solutions, you can refer to the provided tables. Intravenous fluids must always be sterile.

Composition of Common Crystalloid Solutions

Solution	Other Name	[Na+]	[Cl-]	[Glucose]
D5W	5% Dextrose	0	0	252
2/3D & 1/3S	3.3% Dextrose / 0.3% saline	51	51	168
Half-normal saline	0.45% NaCl	77	77	0
Normal saline	0.9% NaCl	154	154	0
Ringer's lactate	Lactated Ringer	130	109	0

Ringer's lactate also has 28 mmol/L lactate, 4 mmol/L K⁺ and 3 mmol/L Ca²⁺. Ringer's acetate (ASERING) also has 28 mmol/L acetate, 4 mmol/L K⁺ and 3 mmol/L Ca²⁺.

Effect of Adding One Litre

Solution	Change in ECF	Change in ICF
D5W	333 mL	667 mL
2/3D & 1/3S	556 mL	444 mL
Half-normal saline	667 mL	333 mL
Normal saline	1000 mL	0 mL
Ringer's lactate	900 mL	100 mL

Equipment for Infusion

Intravenous cannula

The typical IV infusion set is composed of:

• A sterile container (can be a glass bottle, plastic bottle, or plastic bag) containing fluids.
• An attached drip chamber for observing the flow rate and minimizing air bubbles.
• A lengthy sterile tube with a clamp for flow regulation.
• Connectors for the access device and for allowing "piggybacking" of a secondary infusion set, for instance, adding an antibiotics dose to an ongoing fluid drip.

An infusion pump offers meticulous control of the flow rate and quantity administered. For non-critical flow rate changes or in the absence of pumps, a gravity drip technique is employed by placing the bag higher than the patient and using the clamp for flow control.

A rapid infuser becomes essential if the patient needs a significant flow rate and the IV access device can handle it. It might be a cuff that's inflatable around the fluid bag or an electrical counterpart that can also warm the infused fluid.

Intermittent Infusion

Intermittent infusion is prescribed when medications are required periodically without the need for additional fluid. It employs the techniques of a regular IV drip (either pump or gravity). After administering the complete medication dose, the tubing disconnects from the IV access device. Certain drugs are also given via IV push, where a syringe is attached to the IV access and the drug is injected. After injecting medication into the IV fluid stream, measures ensure its delivery to the patient, typically by letting the fluid stream flow. Occasionally, a "flush" might be used post-injection to expedite medicine delivery into the bloodstream.

Intravenous Therapy Risks

Intravenous therapy, while beneficial, comes with risks. It should be conducted by trained individuals, supervised medically, and with the right equipment.

Infection

Skin breaches can introduce infections. Though IV insertion is done sterilely, organisms like Staphylococcus aureus or Candida albicans might penetrate via the insertion point or equipment might inadvertently introduce bacteria.

Local infections lead to observable swelling, redness, and fever. A septicemia condition arises when bacteria spread bloodstream-wide, potentially causing rapid and severe consequences. A contaminated central IV can directly introduce bacteria into the main circulation, escalating the septicemia risk.

Phlebitis

Phlebitis is the irritation of veins from foreign body presence or the infused solutions. It manifests as swelling, pain, and redness around the affected vein. The symptoms might be alleviated with warmth, limb elevation, or flow rate adjustments without necessarily removing the IV. Repeated injections can cause peripheral veins, especially in intravenous drug users and chemotherapy patients, to become sclerotic and hard to access.

Infiltration

Infiltration happens when the IV catheter exits or pierces the vein into surrounding tissues. This demands IV relocation. Although symptoms like pain and swelling are temporary, continuous fluid infiltration into subdermal tissues can cause compression injuries, termed infiltration injuries.

Fluid Overload

Fluid overload emerges when fluids are administered beyond the body's absorption or excretion capacity. It can lead to conditions like hypertension, heart failure, and pulmonary edema.

Electrolyte Disbalance

Providing an imbalanced solution can upset the patient's sodium, potassium, and other electrolyte levels. Regular blood tests are often conducted in hospitals to oversee these levels.

Embolism

Embolisms are blockages in vessels caused by delivered solid masses or air bubbles through IV. Peripheral IVs have a diminished embolism risk compared to central IVs.

Air embolisms below 30 milliliters usually dissolve harmlessly in the bloodstream. Larger volumes can obstruct pulmonary circulation or even halt the heart. Veins are preferred for IV administration because air bubbles can exit through the lungs. Heart defects causing right-to-left shunts make patients susceptible to embolisms even from smaller air amounts.

The fatality risk from air embolism remains extremely low, partly due to its challenging diagnosis.

See Also

• Life support
• Blood transfusion
• Blood substitutes

External References

• Nursewise
• UWash
• IV Catheter

Intravenous Resources
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