Introduction
Background
Volume depletion is a common complication of illness observed in pediatric patients presenting to the emergency department (ED). At times, it is the presenting complaint. Early recognition and early intervention are important to prevent progression to shock and cardiovascular collapse.
Pathophysiology
Pediatric dehydration is frequently the result of gastroenteritis, characterized by vomiting and diarrhea. However, other causes of dehydration may include poor oral intake due to diseases such as stomatitis, insensible losses due to fever, or osmotic diuresis from uncontrolled diabetes mellitus.
The terms dehydration and volume depletion are commonly used interchangeably to denote intravascular fluid depletion. However, it is useful for clinicians to understand that volume depletion is distinct from dehydration.
Volume depletion denotes contraction of the total intravascular plasma pool, whereas dehydration denotes loss of plasma-free water disproportionate to loss of sodium, the main intravascular solute. The distinction is important because volume depletion can exist with or without dehydration, and dehydration can exist with or without volume depletion.
In children with dehydration, the most common underlying problem actually is volume depletion, not dehydration. Intravascular sodium levels are within the reference range, indicating that excess free water is not being lost from plasma. Rather, the entire plasma pool is contracted with solutes (mostly sodium) and solvents (mostly water) lost in proportionate quantities. This is volume depletion without dehydration. The most common cause is excessive extrinsic loss of fluids.
Pediatric patients, especially those younger than 4 years, tend to be more susceptible to volume depletion as a result of vomiting, diarrhea, or increases in insensible water losses. Significant fluid losses may occur rapidly. The turnover of fluids and solute in infants and young children can be as much as 3 times that of adults. This is because of the following:
- Higher metabolic rates
- Increased body surface area to mass index
- Higher body water contents (Water comprises approximately 70% of body weight in infants, 65% in children, and 60% in adults.)
Volume depletion can be concurrent with hyponatremia. This is characterized by plasma volume contraction with free water excess. An example is a child with diarrhea who has been given tap water to replete diarrheal losses. Free water is replenished, but sodium and other solutes are not.
In hyponatremic volume depletion, the patient may appear more ill clinically than fluid losses indicate. The degree of volume depletion may be clinically overestimated. Serum sodium levels less than 120 mEq/L may result in seizures. If intravascular free water excess is not corrected during volume replenishment, the shift of free water to the intracellular fluid compartment may cause cerebral edema.
With true dehydration, plasma volume contracts with disproportionate further free water loss. An example is the child with diarrhea whose fluid losses have been replenished with hypertonic soup, boiled milk, baking soda, or improperly diluted infant formula. Volume has been restored, but free water has not.
In hypernatremic volume depletion, the patient may appear less ill clinically than fluid losses indicate. The degree of volume depletion may be underestimated. Usually, at least a 10% volume deficit exists with hypernatremic volume depletion.
As in hyponatremia, hypernatremic volume depletion may result in serious central nervous system (CNS) effects as a result of structural changes in central neurons. However, cerebral shrinkage occurs instead of cerebral edema. This may result in intracerebral hemorrhage, seizures, coma, and death. For this reason, volume restoration must be performed gradually over 24 hours or more. Gradual restoration prevents a rapid shift of fluid across the blood-brain barrier and into the intracellular fluid compartment.
Potassium considerations
Potassium shifts between intracellular and extracellular fluid compartments occur more slowly than free water shifts. Serum potassium level may not reflect intracellular potassium levels. Although a potassium deficit is present in all patients with volume depletion, it is not usually clinically significant. However, failure to correct for a potassium deficit during volume repletion may result in clinically significant hypokalemia. Potassium should not be added to replacement fluids until adequate urine output is obtained.
Acid and base problems
Clinicians may observe derangements of acid-base balance with volume depletion. Some degree of metabolic acidosis is common, especially in infants.
Mechanisms include bicarbonate loss in stool and ketone production. Hypovolemia causes decreased tissue perfusion and increased lactic acid production. Decreased renal perfusion causes decreased glomerular filtration rate, which, in turn, leads to decreased hydrogen (H+) ion excretion. These factors combine to produce a metabolic acidosis.
In most patients, acidosis is mild and easily corrected with volume restoration (as increased renal perfusion permits excretion of excess H+ ions in the urine). Administration of glucose-containing fluids further decreases ketone production.
Frequency
United States
Pediatric dehydration, particularly that due to gastroenteritis, is a common ED complaint. Approximately 200,000 hospitalizations and 300 deaths per year are attributed to gastroenteritis each year.
International
According to the Centers for Disease Control and Prevention (CDC), for children younger than 5 years, the annual incidence of diarrheal illness is approximately 1.5 billion, while deaths are estimated between 1.5 and 2.5 million. Though these numbers are staggering, they actually represent an improvement from the early 1980s, when the death rate was approximately 5 million per year.1
Mortality/Morbidity
- Morbidity varies with the degree of volume depletion and the underlying cause.
- The severely volume-depleted infant or child is at risk for death from cardiovascular collapse.
- Hyponatremia resulting from replacement of free water alone may cause seizures.
- Improper management of volume repletion may cause iatrogenic morbidity or mortality.
Age
Infants and younger children are more susceptible to volume depletion than older children.
Clinical
History
The goal of the history and physical examination is to determine the severity of the child's condition. Classifying the degree of dehydration as mild, moderate, or severe accurately allows for appropriate therapy and disposition of the patient in a timely fashion.
Obtaining a complete history from the parent or caregiver is important because it provides clues to the type of dehydration present.
The emergency physician should be diligent in obtaining the following information:
- Feeding pattern and fluids given
- Number of wet diapers compared with normal
- Fluid loss (eg, vomiting, oliguria or anuria, diarrhea)
- Possible ingestions
- Activity
- Medications
- Heat and sunlight exposures
Physical
The following table highlights the physical findings seen with different levels of pediatric dehydration.
Open table in new window
Table
| Symptom | Mild (<3% body weight lost) | Moderate (3-9% body weight lost) | Severe (>9% body weight lost) |
| Mental status | Normal, alert | Restless or fatigued, irritable | Apathetic, lethargic, unconscious |
| Heart rate | Normal | Normal to increased | Tachycardia or bradycardia |
| Quality of pulse | Normal | Normal to decreased | Weak, thready, impalpable |
| Breathing | Normal | Normal to increased | Tachypnea and hyperpnea |
| Eyes | Normal | Slightly sunken | Deeply sunken |
| Fontanelles | Normal | Slightly sunken | Deeply sunken |
| Tears | Normal | Normal to decreased | Absent |
| Mucous membranes | Moist | Dry | Parched |
| Skin turgor | Instant recoil | Recoil <2 seconds | Recoil >2 seconds |
| Capillary refill | <2 seconds | Prolonged | Minimal |
| Extremities | Warm | Cool | Mottled, cyanotic |
| Symptom | Mild (<3% body weight lost) | Moderate (3-9% body weight lost) | Severe (>9% body weight lost) |
| Mental status | Normal, alert | Restless or fatigued, irritable | Apathetic, lethargic, unconscious |
| Heart rate | Normal | Normal to increased | Tachycardia or bradycardia |
| Quality of pulse | Normal | Normal to decreased | Weak, thready, impalpable |
| Breathing | Normal | Normal to increased | Tachypnea and hyperpnea |
| Eyes | Normal | Slightly sunken | Deeply sunken |
| Fontanelles | Normal | Slightly sunken | Deeply sunken |
| Tears | Normal | Normal to decreased | Absent |
| Mucous membranes | Moist | Dry | Parched |
| Skin turgor | Instant recoil | Recoil <2 seconds | Recoil >2 seconds |
| Capillary refill | <2 seconds | Prolonged | Minimal |
| Extremities | Warm | Cool | Mottled, cyanotic |
Of these, the most accurate in identifying the level of dehydration are capillary refill, skin turgor, and breathing. The least accurate are mental status, heart rate, and fontanelle appearance.
Causes
In most cases, volume depletion in children is from fluid losses from vomiting or diarrhea.
Vomiting may be caused by any of the following systems or processes:
- CNS (eg, infections, space-occupying lesions)
- GI (eg, gastroenteritis, obstruction, hepatitis, liver failure, appendicitis, peritonitis, intussusception, volvulus, pyloric stenosis, toxicity [ingestion, overdose, drug effects])
- Endocrine (eg, diabetic ketoacidosis [DKA], congenital adrenal hypoplasia, Addisonian crisis)
- Renal (eg, infection, pyelonephritis, renal failure, renal tubular acidosis)
- Psychiatric (eg, psychogenic vomiting) - This is not seen in infants and is rare in children compared with adults.
Diarrhea may be caused by any of the following systems or processes:
- GI (eg, gastroenteritis, malabsorption, intussusception, irritable bowel, inflammatory bowel disease, short gut syndrome)
- Endocrine (eg, thyrotoxicosis, congenital adrenal hypoplasia, Addisonian crisis, diabetic enteropathy)
- Psychiatric (eg, anxiety)
- Volume depletion not caused by vomiting or diarrhea may be divided into renal or extrarenal causes.
- Renal causes include use of diuretics, renal tubular acidosis, and renal failure (eg, trauma, obstruction, salt-wasting nephritis). The effects of diabetes insipidus, hypothyroidism, and adrenal insufficiency also fall into this category.
- Extrarenal causes include third-space extravasation of intravascular fluid (eg, pancreatitis, peritonitis, sepsis, heart failure); insensible losses from fever, sweating, burns, or pulmonary processes; poor oral intake; and hemorrhage.
More on Pediatrics, Dehydration |
 Overview: Pediatrics, Dehydration |
| Differential Diagnoses & Workup: Pediatrics, Dehydration |
| Treatment & Medication: Pediatrics, Dehydration |
| Follow-up: Pediatrics, Dehydration |
| References |
| Next Page » |
References
King CK, Glass R, Bresee JS, et al. Managing acute gastroenteritis among children: oral rehydration, maintenance, and nutritional therapy. MMWR Recomm Rep. Nov 21 2003;52(RR-16):1-16. [Medline].
Spandorfer PR, Alessandrini EA, Joffe MD, Localio R, Shaw KN. Oral versus intravenous rehydration of moderately dehydrated children: a randomized, controlled trial. Pediatrics. Feb 2005;115(2):295-301. [Medline].
Freedman SB, Adler M, Seshadri R, Powell EC. Oral ondansetron for gastroenteritis in a pediatric emergency department. N Engl J Med. Apr 20 2006;354(16):1698-705. [Medline].
2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. Dec 13 2005;112(24 Suppl):IV1-203. [Medline].
Alhashimi D, Alhashimi H, Fedorowicz Z. Antiemetics for reducing vomiting related to acute gastroenteritis in children and adolescents. Cochrane Database Syst Rev. Oct 18 2006;CD005506. [Medline].
American Academy of Pediatrics. Practice parameter: the management of acute gastroenteritis in young children. American Academy of Pediatrics, Provisional Committee on Quality Improvement, Subcommittee on Acute Gastroenteritis. Pediatrics. Mar 1996;97(3):424-35. [Medline].
Barkin RM, Ward DG. Infectious diarrheal disease and dehydration. In: Marx JA. Rosen's Emergency Medicine: Concepts and Clinical Practice. Vol 3. 6th ed. Philadelphia, Pa: Mosby/Elsevier; 2006:2623-34.
Bezerra JA, Stathos TH, Duncan B, Gaines JA, Udall JN Jr. Treatment of infants with acute diarrhea: what's recommended and what's practiced. Pediatrics. Jul 1992;90(1 Pt 1):1-4. [Medline].
Carcillo JA, Davis AL, Zaritsky A. Role of early fluid resuscitation in pediatric septic shock. JAMA. 1991;266(9):1242-5. [Medline].
De Bruin WJ, Greenwald BM, Notterman DA. Fluid resuscitation in pediatrics. Crit Care Clin. Apr 1992;8(2):423-38. [Medline].
Holliday M. The evolution of therapy for dehydration: should deficit therapy still be taught?. Pediatrics. Aug 1996;98(2 Pt 1):171-7. [Medline].
Idris AH, Melker RJ. High-flow sheaths for pediatric fluid resuscitation: a comparison of flow rates with standard pediatric catheters. Pediatr Emerg Care. Jun 1992;8(3):119-22. [Medline].
Kallen RJ, Lonergan JM. Fluid resuscitation of acute hypovolemic hypoperfusion states in pediatrics. Pediatr Clin North Am. Apr 1990;37(2):287-94. [Medline].
Kersten H. Oral ondansetron decreases the need for intravenous fluids in children with gastroenteritis. J Pediatr. Nov 2006;149(5):726. [Medline].
Lozon MM. Pediatric vascular access and blood sampling techniques. In: Roberts JR, Hedges JR. Clinical Procedures in Emergency Medicine. 4th ed. Philadelphia: WB Saunders; 2004:357-8.
Mange K, Matsuura D, Cizman B, et al. Language guiding therapy: the case of dehydration versus volume depletion. Ann Intern Med. Nov 1 1997;127(9):848-53. [Medline].
Steiner MJ, DeWalt DA, Byerley JS. Is this child dehydrated?. JAMA. Jun 9 2004;291(22):2746-54. [Medline].
Wathen JE, MacKenzie T, Bothner JP. Usefulness of the serum electrolyte panel in the management of pediatric dehydration treated with intravenously administered fluids. Pediatrics. Nov 2004;114(5):1227-34. [Medline].
Further Reading
Keywords
dehydration, dehydration in kids, dehydration in baby, dehydration symptoms, dehydration treatment, water loss, fluid loss, diarrhea, vomiting, volume depletion, hypovolemia, fluid deficit
