Fluids, Electrolytes, and Urinary Calculi: A Clinical Guide

Electrolyte Imbalances

Electrolytes carry electrical charges that are vital for nerve conduction and muscle contraction. Even minor deviations can be catastrophic.

Sodium ($\text{Na}^+$)

Sodium is the primary determinant of serum osmolality and water distribution.

• Hyponatremia: Characterized by lethargy, muscle weakness, headache, and seizures. If replacing sodium, it must be done gradually to avoid neurological risks.
• Hypernatremia: Presents as extreme thirst, dry mucous membranes, muscle twitching, and weakness. Treatment involves hypotonic fluids (such as $0.3\% \text{ NS}$) and diuretics to lower sodium levels.

Potassium ($\text{K}^+$)

Potassium is essential for cardiac and neuromuscular function. Because of its impact on the heart, potassium imbalances are high-priority emergencies.

• Hypokalemia: Leads to muscle weakness, leg cramps, and lethal cardiac dysrhythmias, specifically characterized by U waves and flat T waves.
• Hyperkalemia: This is a life-threatening condition. Clinical signs include muscle weakness, respiratory distress, and dangerous ECG changes such as peaked T waves and widened QRS complexes.
• Priority Interventions: For hyperkalemia, treatments include calcium gluconate (to stabilize the heart), insulin with dextrose (to shift K+ into cells), or dialysis.

CRITICAL SAFETY ALERT: Never administer potassium ($\text{K}^+$) via the subcutaneous (SQ) or intramuscular (IM) routes. When administering IV potassium, it must be diluted and the rate must be strictly controlled to prevent cardiac arrest.

Calcium ($\text{Ca}^{2+}$) and Magnesium ($\text{Mg}^{2+}$)

• Hypocalcemia: Manifests as tetany and paresthesia (tingling) of the fingers and lips. Nurses must assess for two specific signs:
  1. Chvostek’s sign: Facial twitching when the facial nerve is tapped.
  2. Trousseau’s sign: A carpal spasm induced by inflating a blood pressure cuff.
• Hypomagnesemia: Often presents alongside hypocalcemia. It is characterized by hyperactive deep tendon reflexes (DTRs), muscle tetany, and ECG changes like PVCs.

Urinary Calculi

Urinary calculi, or stones, can occur anywhere in the urinary tract, causing intense pain and potential obstruction.

Nephrolithiasis and Ureterolithiasis

• Nephrolithiasis: Stones located in the kidney, typically causing pain in the costovertebral/flank region.
• Ureterolithiasis: Stones located in the ureter, often causing wave-like, excruciating pain that radiates toward the abdomen or thighs.

Clinical Manifestations: Patients often present with "renal colic" (severe pain), nausea, vomiting, hematuria (blood in urine), and potentially oliguria ($< 400\text{ mL/day}$) or anuria ($< 100\text{ mL/day}$) if an obstruction occurs. An obstruction is considered a medical emergency.

Management and Lithotripsy

The priority intervention for urinary calculi is pain management.

A common procedure is lithotripsy (shock wave therapy), which uses shock waves to break stones into smaller pieces.

• Post-procedure expectations: It is normal to see hematuria (blood in urine) for up to 24 hours and to experience bruising or pain on the side.
• Red Flags: If the patient develops a fever or chills, notify the provider immediately, as this may indicate an infection.

Patient Teaching and Diet

To prevent stone recurrence and assist in stone passage, educate the patient on the following:

1. Hydration: Increase fluid intake to at least $3\text{ L/day}$ to flush the system.
2. Activity: Encourage ambulation to help the stone move through the urinary tract.
3. Monitoring: Strain all urine to catch stones for laboratory analysis.
4. Dietary Restrictions:
   • Limit sodium.
   • Limit calcium (dairy products).
   • Avoid oxalates (chocolate, wine).
   • Limit purines (red meat, organ meats, beer).