Fundamentals of IV Therapy: Tubing, Infusion Types, and Clinical Administration

IV Tubing Components and Mechanics

• Tubing Length and Volume Displacement:

  • Standard IV tubing length is approximately $24$ inches.

  • Medication bag sizes often range from $50\,\text{mL}$ to $250\,\text{mL}$.

  • A significant clinical risk is the "dead space" in the tubing. If a $50\,\text{mL}$ bag is used with standard length tubing, approximately half of the medication may remain in the line and not actually reach the patient unless properly flushed.

• Ports:

  • IV lines feature ports which are access points designed to connect additional tubing or syringes for medication administration and fluid mixing.

• Drip Chambers:

  • The drip chamber identifies the rate of fluid movement. If it is not appropriately filled, it may affect the visualization of the infusion.

• Locking Mechanisms:

  • Tubing possesses two primary ways to lock or control flow:

  1. Roller Clamp: A wheel-based manual control to adjust or stop flow.

  2. Push Button/Plan Lock: A simple mechanical switch used to stop flow immediately.

Primary and Secondary Infusion Dynamics

• Primary Infusion:

  • Defined by its role as a continuous infusion.

  • It can consist of simple saline ($NaCl$) or specific medications.

  • The primary tubing is the main line that runs through "the brain" (the electronic infusion pump).

• Secondary Infusion (Piggyback):

  • Secondary medications are typically intermittent infusions.

  • They are commonly scheduled at specific intervals, such as every $6$ hours or every $8$ hours.

  • The secondary tubing is connected to the primary tubing, usually at a port located above the pump.

  • Clinical Rule: If a medication is being run in tandem, the secondary bag must be hung higher than the primary bag when relying on gravity to ensure the secondary medication infuses first.

• Safety and Interdependence:

  • It is possible to run a primary medication against a secondary medication.

  • Both infusions must pass through the electronic pump ("the brain") to ensure accurate dosage and rate control.

Syringe Medication and Pediatric Carriers

• Pediatric Medication Delivery:

  • In pediatric settings, small-volume medication often comes in syringes.

  • These syringes are connected to what is called a Carrier or a primary line.

• Rate Synchronization:

  • The carrier line is programmed to the same rate as the initial infusion. For example, if an infusion is set at $3\,\text{mL/h}$, the carrier or primary will also be set at $3\,\text{mL/h}$.

• Flushing Techniques:

  • If a dose is small (e.g., $1.5\,\text{mg}$, which might only be a fraction of a milliliter), it may get stuck in the tubing.

  • To ensure the full dose reaches the patient, a flush is connected and programmed at the same rate as the medication (e.g., programmed for a volume of $2\,\text{mL}$ at the same speed) to push the drug into the patient's system.

Vesicants, Patient Comfort, and Rate Adjustments

• Vesicants and Harsh Irritants:

  • Certain medications, such as Potassium ($K^+$), are described as harsh or vesicants.

  • Patients may complain of a "burning" sensation during the infusion of these substances.

• Intervention for Burning:

  • If a patient complains of burning at the IV site, the nurse may slow down the infusion rate provided it remains within the "minimum safe rate of infusion" ordered by the physician.

  • Slowing the rate often alleviates the discomfort while maintaining safety and therapeutic efficacy.

Nutrition and Fluid Management

• Total Parenteral Nutrition (TPN):

  • TPN is used for patients at risk for malnutrition who cannot receive nutrition through other means.

  • TPN is frequently administered alongside fat/lipid emulsions.

  • Maintenance: TPN tubing must be changed every $24$ hours to prevent bacterial growth and maintain system integrity.

• Hypoglycemia Management:

  • For patients with chronic hypoglycemia (low blood sugar), providers may select between different dextrose concentrations, such as $D5W$ or higher, depending on the severity of the low sugar levels.

• Fluid Concentration Terminology:

  • A concentration of $0.45\%$ is commonly referred to in clinical settings as "half-normal saline" or just "half."

Pharmaceutical Calculations and Concentrations

• Key Documentation Elements:

  • When charting or calculating, focus on:

  1. Time calculation (duration of infusion).

  2. Rate calculation (volume over time).

  3. Concentration.

• Defining Concentration:

  • Concentration is the amount of drug available in a specific volume.

  • Example: If a nurse is asked for the concentration, they might state, "The concentration is $1.5\,\text{mg}$ for every $5\,\text{mL}$."