Intravenous Therapy: Complications, Fluid Imbalances and Acid-Base Disorders

Factors Determining the Selection of an Intravenous Site

When selecting a site for intravenous (IV) access, consider the following factors:

• Age of the patient
• Dominant hand and arm
• Level of consciousness
• Condition of the skin
• Avoid areas that are injured or damaged
• Characteristics of the veins: choose veins that are good, palpable and straight
• Avoid areas of flexion and joints
• Avoid the arm on the side of a mastectomy or an arteriovenous fistula
• Patient preference
• Duration and type of treatment
• Medications to be administered and their rate of administration

Complications of Intravenous Therapy

1. Infiltration

Causes: Displacement of the catheter or perforation of the vein.

Manifestations: Cold skin, pallor of the area, local discomfort, pain and edema. There is no blood reflux, and the drip flows slowly.

Interventions: Stop the infusion immediately, elevate the extremity, assess the extremity, and cannulate another vein. Notify the physician as needed.

2. Phlebitis

Causes: Large-gauge catheter, prolonged cannulation, administration of irritant substances, or contamination.

Manifestations: Redness, warmth, induration along the venous tract, and pain.

Interventions: Elevate the extremity, stop and remove the catheter, cannulate another vein, do not massage the area, and apply heparinoid ointment.

3. Catheter Dislodgement

Causes: Insufficient or inadequate fixation, or accidental or voluntary removal.

Manifestations: Complete or partial exit of the needle or catheter from the vein.

Interventions: Reinsert the catheter if possible, or stop bleeding by applying pressure with gauze and puncture another area.

4. Obstruction

Causes:

• a) Interruption of flow: external compression, kinking, or blood coagulation; highly viscous solutions
• b) Blood reflux into the system

Manifestations: The system does not flow, stops, or flows slowly.

Interventions: Aspirate the system with a syringe and reposition the limb.

5. Hematoma

Causes: Extravasation of blood from the vein due to inadequate pressure after catheter removal or puncture of the vein.

Manifestations: Pain, discoloration (purple or bluish area).

Interventions: Remove the catheter, apply compression, and use creams and heparinoids.

Fluid and Electrolyte Imbalances

Sodium and water imbalances are associated with changes in sodium concentration and osmolality. The distribution of water affects the extracellular fluid (ECF) and is important for intracellular fluid (ICF). Sodium is essential for the generation and transmission of nerve impulses and for the regulation of acid-base balance.

The digestive tract absorbs food and sodium, and the kidneys regulate sodium levels. Sodium imbalance is associated with volume deficits in the extracellular fluid (ECF).

Hyponatremia

Hyponatremia can result from excessive fluid losses that contain more sodium than water, or from hypoosmolality that causes water to shift into cells. One of the most frequent causes of hyponatremia is the inappropriate use of IV fluids without sodium, which can occur in postoperative patients.

Symptoms: Symptoms are related to increased cell size and manifest primarily in the central nervous system (CNS).

Acid-Base Balance

The body maintains a stable pH by neutralizing acids produced during metabolism through buffers and by regulating the excretion of acids and bases. Most health problems involving acid-base imbalance lead to acidosis or alkalosis.

Alterations in Acid-Base Balance

1. Respiratory acidosis (excess carbon dioxide): Occurs when hypoventilation results in increased CO₂. Carbonic acid accumulates in the blood, dissociates, and lowers the pH. The kidneys compensate by conserving bicarbonate and increasing the secretion of hydrogen ions into the urine.
2. Respiratory alkalosis (carbon dioxide deficit): Occurs with hyperventilation, which decreases PCO₂. Respiratory alkalosis is infrequently compensated by the kidneys.
3. Metabolic acidosis (bicarbonate deficit): Compensated by increased respiratory rate, which reduces CO₂ through the lungs.
4. Metabolic alkalosis (bicarbonate excess): Occurs when there is an increase in bicarbonate or a loss of acid. Compensation is a decrease in respiratory rate, which increases CO₂ in the plasma.

Normal Values

• pH: 7.35–7.45
• PCO₂: 35–45 mmHg
• Bicarbonate (HCO₃^-): 20–30 mEq/L
• PO₂: 80–100 mmHg
• O₂ saturation: 96–100%
• Base excess (BE): ±2