Pharmacotherapeutics II: Regulation of Body Fluid Compartments and IV Therapy

Regulation of Body Fluid Compartments

• Fundamentals of Fluid Movement

  • Osmosis: The process of fluid movement across a membrane.

  • Solute: The substance that is dissolved in a fluid.

  • Solvent: The liquid in which a solute is dissolved to form a solution.

  • Core Principle: Water follows the solute. The concentration of solutes determines the direction of water movement.

• Osmolality vs. Osmolarity

  • Osmolality (per kg):

    • Definition: The number of dissolved particles in $1\,kg$ of blood or urine.

    • Unit: $mOsm/kg$.

    • Clinical Focus: It focuses on the concentration of solutes within the body.

  • Osmolarity (per L):

    • Definition: The number of dissolved particles in $1\,L$ of solution.

    • Unit: $mOsm/L$.

    • Clinical Focus: It focuses on water concentration in a specific solution, such as an Intravenous (IV) fluid.

Body Fluid Compartments

• Intracellular Fluid (ICF): Fluid located inside the cells.

• Extracellular Fluid (ECF): Fluid located outside the cells. This is further categorized into:

  • Interstitial Fluid: Fluid located between tissue spaces.

  • Intravascular Fluid: Fluid located inside the blood vessels, also known as plasma.

Parenteral Fluid Therapy (IV Fluids)

• Classification of IV Fluids

  • Crystalloids: Aqueous solutions of mineral salts or other water-soluble molecules.

  • Colloids: Larger molecules that do not pass through semi-permeable membranes (e.g., blood products like Red Blood Cells).

    • Example Case: Simulated CPDA-1 Red Blood Cells used for training, containing distilled water with red colorant. It simulates blood divided from $450\,mL$ of whole blood.

• Types of Fluids Based on Tonicity

  • Isotonic Fluids:

    • Etymology: "Iso" means same; "tonic" refers to the concentration of the solution.

    • Definition: These fluids have the same concentration as plasma.

    • Effect: They add to ECF volume without causing fluid shifts between compartments.

    • Examples:

      • Normal Saline ($0.9\%$ Sodium Chloride Injection USP).

      • $D5W$ ($5\%$ Dextrose Injection USP).

      • Lactated Ringers (LR) (Lactated Ringer's Injection USP).

  • Hypotonic Fluids:

    • Etymology: "Hypo" means low or beneath.

    • Definition: A solution with a lower concentration of solutes compared to plasma.

  • Hypertonic Fluids:

    • Etymology: "Hyper" means excess.

    • Definition: A solution with a higher concentration of solutes compared to plasma.

Other IV Substances and Administration

• Parenteral Nutrition

  • PPN: Peripheral Parenteral Nutrition.

  • TPN: Total Parenteral Nutrition. This is highly concentrated and must be administered through a central line only.

• Medication Administration Methods

  • Continuous: Infused slowly and steadily over a long period.

  • Intermittent: Infused at specific intervals.

  • Bolus: A concentrated dose given rapidly.

Intravenous Catheters and Access

• Peripheral Intravenous Access: Standard IV access in peripheral veins.

• Midline Catheters

  • Think "Midway": These are longer than peripheral IVs but are not threaded all the way to the heart.

  • Includes midlines and mini-midlines.

• Central Lines

  • Think "Center": These bring medications and fluids directly to the center of the body (superior vena cava).

  • PICC (Peripherally Inserted Central Catheter): Inserted in a peripheral vein (usually the arm) and advanced to the heart. Examples include PowerPICC SOLO.

  • Non-tunneled Central Venous Catheter (CVC): Inserted directly into a large vein (jugular or subclavian) without a subcutaneous tunnel. No Dacron cuff is used.

  • Tunneled CVC: Features a subcutaneous tunnel and a Dacron cuff to secure the catheter and provide a barrier to infection.

  • Implanted Port: A device placed under the skin, usually in the chest, for long-term access.

• Ultrasound-Guided IV Placement: The use of ultrasound technology to visualize veins for more accurate catheter insertion.

• Catheter Sizing: Common gauges include $14G, 16G, 18G, 20G, 22G,$ and $24G$.

Safety Warnings and Complications

• Accidental Arterial Placement

  • Warning Signs: Pulsing blood in the tubing.

  • Risks: High pressure, excessive blood flow, localized tissue damage, immediate pain, nerve injury, and embolism risk.

  • Action: The catheter MUST be removed ASAP.

• Nursing Student Policy

  • Students may only perform clinical procedures and administer medications under the supervision of a clinical instructor until competency is demonstrated.

  • After competency is met, staff RN supervision is allowed with instructor approval.

  • Direct Supervision Requirement: An RN or instructor must be physically present for:

    • Preparation and administration of controlled drugs.

    • IV titration.

    • IV medication and fluids, including saline flushes.

• General Complications

  • Air Embolism: Air entering the venous system.

  • Infection: Can occur at the insertion site or systemically (Central Line-associated Bloodstream Infection).

  • Fluid Overload: Excess fluid in the circulatory system, often manifested by distension of the External Jugular Vein.

  • Hematoma: A collection of blood under the skin at the site.

  • Clotting/Obstruction: Occurs when a fibrin mesh or blood clot forms, blocking the vessel or catheter.

    • Mechanism: Vessel injury $\rightarrow$ Clotting factors release $\rightarrow$ Platelet plug $\rightarrow$ Fibrin strands form insoluble clot.

• Infiltration

  • Definition: Seepage of non-vesicant IV fluid into the surrounding tissue.

  • Signs: Cool skin at the site, edema (swelling), and slowed infusion rate.

  • Infiltration Scale:

    • Grade 0: No clinical symptoms.

    • Grade 1: Skin blanched; edema < $1\text{ inch}$ in any direction; cool to touch; with or without pain.

    • Grade 2: Skin blanched; edema $1$ to $6\text{ inches}$ in any direction; cool to touch; with or without pain.

    • Grade 3: Skin blanched, translucent; gross edema > $6\text{ inches}$ in any direction; cool to touch; mild to moderate pain; possible numbness.

    • Grade 4: Skin blanched, translucent, tight, leaking; skin discolored, bruised, swollen; gross edema > $6\text{ inches}$ in any direction; deep pitting tissue edema; circulatory impairment; moderate to severe pain; infiltration of blood products, irritants, or vesicants.

• Extravasation

  • Definition: Infiltration of a vesicant (a medication that causes tissue damage/blistering) into the surrounding tissue.

  • Vesicant Example: Dopamine can cause blistering, necrosis, and inflammation.

• Phlebitis and Thrombophlebitis

  • Phlebitis: Inflammation of the vein.

  • Thrombophlebitis: Inflammation and clot formation due to trauma to the vein.

  • Phlebitis Scale:

    • Grade 0: No clinical symptoms.

    • Grade 1: Erythema (redness) at access site with or without pain.

    • Grade 2: Pain at access site with erythema, edema, or both.

    • Grade 3: Pain at access site; erythema; edema; streak formation; palpable venous cord.

    • Grade 4: Pain at access site; erythema; streak formation; palpable venous cord longer than $1\text{ inch}$; purulent drainage.

IV Flow Rate Calculations

• Drop Factors

  • Micro: Delivers smaller volumes; typically $60\,gtt$ (drops) to deliver $1\,mL$.

  • Macro: Delivers larger volumes; typically $10\,gtt$, $15\,gtt$, or $20\,gtt$ to deliver $1\,mL$.

• Formula for Gravity Flow Rates     $\text{Flow Rate (gtt/min)} = \left[ \frac{\text{Total Volume (mL)}}{\text{Total Time (minutes)}} \right] \times \text{Drop Factor}$

• Calculation Examples

  • Example 1: Administer $1\,gram$ Ceftriaxone in $50\,mL$ of $D5W$ over $30\,minutes$; drop factor is $60\,gtt$.         $\frac{50}{30} = 1.67$         $1.67 \times 60 = 100\,gtt/min$

  • Example 2 (Practice): Administer $4.5\,grams$ of Piperacillin Sodium–Tazobactam Sodium (Zosyn) in $50\,mL$ over $4\,hours$; drop factor is $15\,gtt$.

    • Step 1: Convert hours to minutes: $4\,hours \times 60\,minutes = 240\,minutes$.

    • Step 2: Apply formula:         $\left[ \frac{50}{240} \right] \times 15 = 3.125\,gtt/min$

Questions & Discussion

• Scenario 1: Suspected Infiltration

  • Question: A patient’s hand is swollen, cool to the touch, and aching $20\,minutes$ after starting an infusion. What is the priority action?

  • Answer: Stop the infusion.

  • Rationale: The first action for suspected infiltration is to stop the infusion. Removing the IV and applying compresses are follow-up steps.

• Scenario 2: Extravasation Vesicant Identification

  • Question: Which medication is likely to cause tissue blistering (extravasation)? (Options: Normal Saline, Dopamine, Zosyn, Heparin).

  • Answer: Dopamine.

  • Rationale: Dopamine is a known vesicant that causes tissue necrosis.

• Scenario 3: Grading Phlebitis

  • Question: A patient reports pain; the nurse evaluates the site and finds edema and pain. What is the phlebitis grade?

  • Answer: Grade 2.

  • Rationale: Pain and edema/erythema characterize Grade 2. Grade 3 would require a palpable cord or streak.

• Scenario 4: Identifying Complications

  • Question: An IV site is cool to the touch, swollen, and the fluid rate has slowed. What occurred?

  • Answer: Infiltration.

  • Rationale: Cool skin and slowed infusion are classic signs of infiltration. Phlebitis would cause warmth, and extravasation would usually show erythema (redness).