Pediatric Fluid Management

Excerpt

Administration of fluid resuscitation is essential in critically ill children. Fluid management is critical when providing acute care in the emergency department or hospitalized children. Early and appropriate fluid administration improves outcomes and reduces mortality in children. Water is essential for cellular homeostasis. There are two major fluid compartments: the intracellular fluid (ICF) and the extracellular fluid (ECF). Two-thirds of the total body water (TBW) is intracellular. The TBW varies with age; 70% in infants, 65% in children, and 60% in adults. The human body has strict physiologic control to maintain a balance of fluid and electrolytes. However, in disease states, these mechanisms may be overwhelmed. Dehydration occurs due to the significant depletion of water and electrolytes. It commonly increases morbidity and mortality in children. Infants and young children are quite sensitive to even a small degree of dehydration. This may be due to:

1. Greater fluid requirements secondary to a higher metabolic rate

2. Higher insensible losses due to increased surface area

3. Lack of ability to relate or communicate their thirst to the caregivers

The physiology of children presenting with dehydration and shock is different from adults. Children have a higher cardiac reserve, allowing them to compensate for significant volume loss much longer than adults. Initially, near age-appropriate vital signs may be present despite ongoing fluid losses. Children maintain cardiac output by raising their heart rate. In children, hypotension is a late finding.

Emergent intravenous fluid administration is required if there is any evidence of inadequate or poor perfusion suggested by:

1. Delayed capillary refill

2. Tachycardia

3. Poor color

4. Oliguria

5. Hypotension

Tachycardia and delayed capillary refill indicate moderate dehydration. The primary goal is to restore circulatory volume rapidly to prevent collapse. Correcting the intravascular volume loss with fluids improves cardiac output and reduces mortality.

Dehydration due to diarrhea mainly occurs due to the contraction of intravascular fluid volume while maintaining intracellular volume. However, severe dehydration presents with early signs of hypovolemic shock. Dehydration is usually expressed as a percent of body weight loss. However, baseline hydrated weights are rarely available in the emergency department.

Clinically, the degree of dehydration is often divided into the following;

1. Mild 5%

2. Moderate 10%

3. Severe >15%

Minimal dehydration is defined as a loss of less than 3% of body weight.

The assessment of the severity of dehydration is essential, as therapy instituted should be based on its severity. However, this assessment of the extent of volume depletion may be difficult. It is difficult to accurately distinguish varying degrees of dehydration based on clinical examination alone. For example, infants and young children with mild dehydration may present with either minimal or no clinical findings other than reduced urine output. Also, children with moderate dehydration manifest with dry mucous membranes, decreased skin turgor, tachycardia with a prolonged capillary refill, and abnormal respiratory pattern.

Treatment recommendations are based on the assessment of dehydration severity. Vital signs and physical exam should be frequently monitored to guide and assess the severity of dehydration. A JAMA study revealed three clinical signs clinically helpful in recognizing 5% or greater dehydration: delayed capillary refill, abnormal skin turgor, and an abnormal respiratory pattern. The presence of the following decreases the likelihood of clinically relevant dehydration: normal-appearing, moist mucous membranes, and absence of sunken eyes.

With a few exceptions, labs possess a limited role in the diagnosis of dehydration. The measurement of electrolytes to determine the co-derangement of sodium is a notable exception. Value also exists in a patient unable to eat, especially young children, monitoring to determine the need for dextrose as a component of fluids. BUN shows partial linear relation to the degree of dehydration, but overall is non-specific. The most useful lab test to determine the degree of dehydration is bicarb less than 17 mEq/L.