Utility of Serum Electrolyte Determination in Dehydrated Pediatric Patients

Abstract & Commentary

Source: Wathen JE, et al. Usefulness of the serum electrolyte panel in the management of pediatric dehydration treated with intravenously administered fluids. Pediatrics 2004; 114:1227-1234.

A serum electrolyte panel (SEP) often is obtained in the management of pediatric patients dehydrated due to gastroenteritis and needing intravenous fluids. The usefulness of this practice was evaluated prospectively in a convenience sample of 182 children, 2 months to 9 years of age, seen in a pediatric emergency department (PED) with an observation unit. Outcome measures included frequency of an abnormal SEP, changes in management as a result of the SEP, relationship of SEP results to patient disposition, and unscheduled return visits (URV). The ability of physicians to predict an abnormal SEP also was studied.

One hundred-eleven patients (61%) had mild dehydration, 55 (30%) were moderately dehydrated, and 16 (9%) had severe dehydration. One hundred sixty-five patients (91%) were discharged from the PED, with seven (4%) having URVs. Seventeen patients (9%) were admitted with two having URVs. Eighty-eight patients (48%) had one or more abnormal SEP values, most commonly from low bicarbonate levels, high blood urea nitrogen (BUN) levels, hypoglycemia, hypokalemia, and hypernatremia. Significantly low serum bicarbonate levels (less than 13 mmol/L) were noted in those children younger than one year, as well as those with a higher estimated degree of dehydration, and more diarrhea. Low serum bicarbonate and glucose levels were associated most commonly with changes in clinical management.

In only 19 (10%) patients did an abnormal SEP change management. Physicians were able to predict only 58% of clinically significant SEP results.

Commentary by Raemma Luck, MD

The American Academy of Pediatrics (AAP) practice parameter on the management of acute gastroenteritis recommends that an SEP be considered in patients with moderate to severe dehydration and those needing intravenous fluids.1 The authors should be commended for raising some questions regarding the value of routinely obtaining an SEP in dehydrated patients needing intravenous fluids. The results of the study showed that 48% of patients had one or more abnormal SEP results, but in only 10% of cases did this change the management. The authors did not break down the clinically significant study results as to the degree of dehydration. Breaking down the results as to which groups have clinically relevant values would provide more useful information to the physician and perhaps limit laboratory testing to a certain subset of patients.

The authors have pointed out that infants younger than one year had lower serum bicarbonate levels despite similar degrees of dehydration. They also were more likely to receive additional intravenous fluids in the observation unit. Correlating significant SEP results with the age group (e.g., younger than or older than one year), in addition to the degree of dehydration, would refine what we know and add depth to the study.

The majority of patients in the study had only mild dehydration (61%), yet they were receiving intravenous fluids. The AAP still recommends oral rehydration therapy for mild to moderate dehydration.1 However, there has been a documented gap between this clinical guideline and what is done currently in clinical practice.2 A survey revealed that physicians are more likely to use intravenous therapy in cases where vomiting is the major symptom.2 The use of adjunctive medications, such as ondansetron, has been shown to decrease vomiting and also decrease the need for admission.3,4 Oral ondansetron, in conjunction with oral rehydration, might obviate the need for intravenous fluids in some patients with mild dehydration but continued vomiting.3 It also has been shown that parenteral ondansetron was effective in reducing vomiting as well as reducing hospitalization in those patients with gastroenteritis who need intravenous fluids.4 This would be useful especially in busy EDs where beds are tight and in those EDs without observation units. Ability to tolerate fluids also would decrease the number of URVs, which in this study was nearly 5% of the total cases.

Clinicians were able to predict only 58% of significant SEP values. One of ten patients had results that altered management. Hence, once a decision is made to give intravenous fluids, the practice of obtaining an SEP, consistent with AAP recommendations, is here to stay.

Dr. Luck is assistant professor of pediatric emergency medicine and director of continuing medical education and the International Health Program at Temple University Children’s Medical Center, Philadelphia.


1. American Academy of Pediatrics, Provisional Committee on Quality Improvement, Subcommittee on Acute Gastroenteritis. Practice Parameter: The management of acute gastroenteritis in young children. Pediatrics 1996; 97:424-435.

2. Ozuah PO, et al. Oral rehydration, emergency physicians, and practice parameters: A national survey. Pediatrics 2002;109:259-261.

3. Ramsook C, et al. A randomized clinical trial comparing oral ondansetron with placebo in children with vomiting from acute gastroenteritis. Ann Emerg Med 2002; 39:397-403.

4. Reeves JJ, et al. Ondansetron decreases vomiting associated with acute gastroenteritis: A randomized controlled trial. Pediatrics 2002;109:e62.