Fluid Imbalances

Fluid balance is critical for maintaining cellular function, tissue perfusion, and organ viability. Nurses must rapidly identify fluid imbalances and intervene appropriately to prevent life-threatening complications.

Understanding Fluid Compartments

The body's total body water (approximately 60% of body weight in adults) is distributed between two main compartments:

• Intracellular Fluid (ICF) - Fluid inside cells (about 2/3 of total body water)
• Extracellular Fluid (ECF) - Fluid outside cells, including intravascular (plasma) and interstitial (between cells)

Fluid moves between compartments based on osmotic and hydrostatic pressure gradients. When these mechanisms fail, fluid imbalances occur.

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Hypovolemia (Fluid Volume Deficit)

Hypovolemia occurs when there is a loss of both water and electrolytes from the extracellular compartment. This is one of the most common fluid disorders encountered in acute care settings.

Causes of Hypovolemia

Clinical Manifestations of Hypovolemia

The body attempts to compensate for fluid loss through sympathetic nervous system activation:

Cardiovascular Signs:

• Tachycardia (compensatory)
• Hypotension (systolic BP < 90 mmHg or drop > 20 mmHg from baseline)
• Weak, thready pulse
• Orthostatic hypotension (drop > 20 mmHg when standing)
• Flat neck veins (when supine)

Skin and Mucous Membranes:

• Poor skin turgor (tenting)
• Dry mucous membranes
• Decreased capillary refill (> 3 seconds)
• Cool, pale extremities

Renal Signs:

• Oliguria (urine output < 0.5 mL/kg/hr)
• Concentrated urine (specific gravity > 1.030)
• Elevated BUN and creatinine

Neurological Signs:

• Altered mental status
• Confusion
• Dizziness

Nursing Interventions for Hypovolemia

Fluid Resuscitation:

1. Establish IV access - Use large-bore catheter (18-gauge or larger)
2. Administer isotonic crystalloids:
   • 0.9% Sodium Chloride (Normal Saline)
   • Lactated Ringer's solution
3. Bolus therapy - 500 mL to 1 L over 15-30 minutes for severe deficits
4. Blood products - For hemorrhagic shock (type-specific or O-negative)

Monitoring:

• Vital signs every 15 minutes during active resuscitation
• Urine output via Foley catheter (goal: > 0.5 mL/kg/hr)
• Central venous pressure (CVP) if central line present
• Daily weights (same time, same scale, same clothing)

Exam Tip: The goal urine output for adequate fluid resuscitation is 0.5 mL/kg/hr for adults. For a 70 kg patient, this equals approximately 35 mL/hour.

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Hypervolemia (Fluid Volume Excess)

Hypervolemia occurs when there is excess fluid in the intravascular compartment. The body cannot effectively eliminate excess fluid, leading to systemic congestion.

Causes of Hypervolemia

Clinical Manifestations of Hypervolemia

Cardiovascular Signs:

• Bounding pulse
• Hypertension
• Jugular vein distension (JVD)
• S3 heart sound (ventricular gallop)
• Elevated CVP

Respiratory Signs:

• Crackles (rales) in lung bases
• Dyspnea
• Orthopnea (difficulty breathing when lying flat)
• Tachypnea
• Cough with frothy sputum (pulmonary edema)

Peripheral Signs:

• Peripheral edema (dependent - ankles, sacrum)
• Weight gain (rapid)
• Ascites (fluid accumulation in abdomen)
• Hepatomegaly

Nursing Interventions for Hypervolemia

Medications:

1. Loop diuretics - Furosemide (Lasix) 20-80 mg IV
   • Monitor for hypokalemia
   • Check potassium levels before and after
2. Potassium-sparing diuretics - Spironolactone for liver patients

Positioning:

• Elevate head of bed 30-45 degrees (High Fowler's)
• Facilitates breathing and reduces venous return

Restrictions:

• Sodium restriction (< 2 g/day)
• Fluid restriction (typically 1.5-2 L/day)

Monitoring:

• Daily weights (1 kg = 1 L of fluid)
• Strict intake and output (I&O)
• Lung sounds every 4 hours
• Oxygen saturation

Exam Tip: When a patient has both crackles and peripheral edema, think fluid overload. Elevate the HOB first to improve breathing, then prepare for diuretic administration.

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Comparison: Hypovolemia vs. Hypervolemia

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Key Points for the NCLEX

• Daily weights are the most accurate way to assess fluid status changes
• Orthostatic vital signs help identify hypovolemia (check BP and pulse lying, sitting, standing)
• JVD assessment requires the patient at 45-degree angle; distension above the clavicle is abnormal
• For hemorrhagic hypovolemia, blood products are essential after crystalloid resuscitation
• Loop diuretics require potassium monitoring; low potassium increases digoxin toxicity risk