5.3 Intravenous Fluid Therapy, Total Parenteral Nutrition, and Blood Products

Intravenous Fluid Therapy

Intravenous (IV) fluid therapy is one of the most common interventions you'll encounter in nursing practice. It's used to maintain fluid balance, correct electrolyte disturbances, deliver nutrients, and replace blood components. Choosing the right solution depends on what the patient needs, and getting it wrong can cause real harm. This section covers the types of IV solutions, total parenteral nutrition, and blood products.

Types of Intravenous Solutions

IV solutions fall into two broad categories: crystalloids and colloids. The difference comes down to molecule size and where the fluid ends up once it's in the body.

Crystalloids

Crystalloids contain small molecules (electrolytes, dextrose) that pass freely through capillary membranes. They distribute between the intravascular and interstitial spaces. Crystalloids are classified by their tonicity relative to extracellular fluid:

• Isotonic solutions (0.9% NaCl, lactated Ringer's) have an osmolarity close to that of blood plasma (~275–295 mOsm/L). They stay mostly in the intravascular space initially and are the go-to choice for fluid resuscitation and maintenance.
• Hypotonic solutions (0.45% NaCl, D5W once dextrose is metabolized) have a lower osmolarity than plasma. Water shifts out of the vasculature and into cells, which makes these useful for cellular dehydration and hypernatremia. Avoid in patients with increased intracranial pressure, since the fluid shift can worsen cerebral edema.
• Hypertonic solutions (3% NaCl, D10W) have a higher osmolarity than plasma. They pull water out of cells and into the vasculature. These are reserved for severe hyponatremia or situations requiring rapid intravascular volume expansion. Hypertonic saline (3% NaCl) must be given via an infusion pump with close monitoring.

Colloids

Colloids contain large molecules that are too big to cross capillary membranes, so they stay in the intravascular space longer than crystalloids. This helps maintain oncotic pressure, the osmotic force exerted by plasma proteins that keeps fluid inside blood vessels.

• Natural colloids: Albumin (5% or 25%) and fresh frozen plasma. Albumin 25% is a potent volume expander because it draws interstitial fluid into the vasculature.
• Synthetic colloids: Hydroxyethyl starch (hetastarch) and dextran. These mimic the effects of natural colloids but carry additional risks, including coagulopathy and renal injury. Their use has declined in recent years due to safety concerns.

Crystalloids vs. Colloids

Fluid and Electrolyte Balance

IV fluid therapy directly affects fluid, electrolyte, and acid-base balance. A few principles to keep in mind:

• Osmolarity of the solution determines the direction of water movement between compartments. Always match the solution to the patient's clinical picture.
• Electrolyte content varies by solution. Lactated Ringer's contains potassium and calcium in addition to sodium, so it's contraindicated in hyperkalemia. Normal saline (0.9% NaCl) in large volumes can cause hyperchloremic metabolic acidosis because of its high chloride content.
• Monitor intake and output, daily weights, and lab values (sodium, potassium, chloride, bicarbonate) to assess whether therapy is working.

Total Parenteral Nutrition

Total parenteral nutrition (TPN) delivers complete nutrition intravenously when the GI tract can't be used (e.g., bowel obstruction, severe pancreatitis, short bowel syndrome). It bypasses digestion entirely.

Components of Parenteral Nutrition

TPN formulations are customized to each patient and include:

• Macronutrients
  • Dextrose (carbohydrates): primary calorie source
  • Amino acids (protein): support tissue repair and immune function
  • Lipid emulsions (soybean oil, olive oil, or fish oil-based): provide essential fatty acids and concentrated calories
• Micronutrients
  • Electrolytes: sodium, potassium, calcium, magnesium, phosphate
  • Vitamins: B-complex, C, A, D, E, K
  • Trace elements: zinc, copper, selenium, manganese, chromium

Administration and Monitoring

1. Central vs. peripheral access: TPN with high osmolarity (>900 mOsm/L) requires a central venous catheter (subclavian, internal jugular, or PICC line). Lower-osmolarity formulations can go through a peripheral line (called PPN, peripheral parenteral nutrition), but this is only suitable for short-term use.
2. Infusion rate: Start slowly and increase gradually to allow the body to adjust, particularly to the glucose load. Never abruptly discontinue TPN, as this can cause rebound hypoglycemia. Taper the rate before stopping.
3. Blood glucose monitoring: Dextrose in TPN can cause significant hyperglycemia. Check blood glucose every 4–6 hours initially, and expect insulin to be added to the TPN bag or given separately.
4. Infection prevention: The central line is a major infection risk. Use strict aseptic technique during dressing changes and tubing changes. Dedicated TPN lines should not be used for other infusions.
5. Lab monitoring: Check a comprehensive metabolic panel, magnesium, phosphorus, and triglycerides regularly. Watch for refeeding syndrome in malnourished patients, which causes dangerous drops in phosphate, potassium, and magnesium as the body shifts from catabolic to anabolic metabolism.
6. Liver function: Long-term TPN can cause parenteral nutrition-associated liver disease (PNALD). Monitor liver enzymes and bilirubin.

Blood Products

Blood product transfusions replace specific components that the patient is missing. Each product has distinct indications and nursing considerations.

Types of Blood Products

• Packed red blood cells (PRBCs) treat anemia and acute blood loss by restoring oxygen-carrying capacity. One unit typically raises hemoglobin by about 1 g/dL. PRBCs must be ABO and Rh compatible and are infused through a blood administration set with a 170–260 micron filter.
• Fresh frozen plasma (FFP) contains all clotting factors and plasma proteins. It's used to treat coagulopathies (elevated INR/PT), massive transfusion protocols, and plasma volume replacement. FFP must be ABO compatible but does not require Rh matching.
• Platelets treat thrombocytopenia or platelet dysfunction. They're often transfused when the platelet count drops below 10,000/µL (or below 50,000/µL before a procedure). Platelets are stored at room temperature and have a short shelf life (5 days), which increases infection risk.
• Cryoprecipitate is rich in fibrinogen, factor VIII, von Willebrand factor, and factor XIII. It's used for hypofibrinogenemia, hemophilia A, and von Willebrand disease.

Transfusion Reactions

Monitoring for transfusion reactions is a core nursing responsibility. Key steps:

1. Verify the patient's identity and blood product compatibility with two nurses at the bedside (per facility policy).
2. Obtain baseline vital signs before starting the transfusion.
3. Infuse slowly for the first 15 minutes and stay with the patient. Most severe reactions occur early.
4. Monitor vital signs per protocol (typically at 15 minutes, 30 minutes, then hourly).
5. If a reaction is suspected (fever, chills, urticaria, dyspnea, hypotension, back/flank pain), stop the transfusion immediately, keep the IV line open with normal saline, and notify the provider.

Common reaction types include:

• Febrile non-hemolytic: fever and chills without hemolysis; most common reaction
• Allergic: urticaria, itching; mild cases may be treated with diphenhydramine and the transfusion restarted per provider order
• Acute hemolytic: ABO incompatibility causes rapid RBC destruction; presents with fever, flank pain, hemoglobinuria, and hypotension. This is a medical emergency.
• Transfusion-related acute lung injury (TRALI): acute respiratory distress within 6 hours of transfusion; requires supportive care

Correction of Fluid and Electrolyte Imbalances

Selecting the right IV therapy depends on the specific imbalance. Here's a summary of common corrections:

Hypovolemia

• First-line: isotonic crystalloids (0.9% NaCl or lactated Ringer's) to restore intravascular volume
• Colloids (albumin, hetastarch) if oncotic pressure is low or large crystalloid volumes are ineffective

Hypernatremia (serum sodium >145 mEq/L)

• Hypotonic solutions (0.45% NaCl, D5W) to dilute excess sodium
• Free water replacement via oral intake or enteral feeding
• Correct gradually: no faster than 10–12 mEq/L per 24 hours to avoid cerebral edema

Hyponatremia (serum sodium <135 mEq/L)

• Severe/symptomatic: hypertonic saline (3% NaCl) with close monitoring; correct no faster than 8–12 mEq/L per 24 hours to prevent osmotic demyelination syndrome (formerly called central pontine myelinolysis)
• Euvolemic or hypervolemic: fluid restriction and diuretics to promote free water excretion

Hypokalemia (serum potassium <3.5 mEq/L)

• Potassium chloride (KCl) supplementation, either IV (added to maintenance fluids, never pushed as a bolus) or oral
• IV potassium should not exceed 10 mEq/hour via peripheral line (20 mEq/hour via central line with cardiac monitoring)
• Monitor for cardiac arrhythmias (flattened T waves, U waves on ECG) and muscle weakness

Hyperkalemia (serum potassium >5.0 mEq/L)

Treatment follows a stepwise approach based on urgency:

1. Calcium gluconate IV to stabilize the cardiac membrane and prevent fatal arrhythmias (works within minutes but does not lower potassium)
2. Regular insulin with dextrose (typically 10 units insulin + 25g D50) to drive potassium into cells temporarily
3. Sodium bicarbonate if acidosis is present, which also promotes intracellular potassium shift
4. Loop diuretics (furosemide) to promote renal excretion of potassium
5. Sodium polystyrene sulfonate (Kayexalate) or patiromer to bind potassium in the GI tract for slower removal
6. Dialysis for refractory or life-threatening cases