Pediatric emergency medicine trisk 132

concentration of 2% to 2.5%. Soda, juice, popsicles, and soups are inappropriate
rehydration solutions in dehydrated infants and children and should be
discouraged as they do not have the appropriate glucose-to-sodium ratio and are
not absorbed as easily as electrolyte solutions. Studies have evaluated half
strength apple juice (mixed with water) as an alternate therapy as compared to
ORT and have found fewer treatment failures most likely secondary to patient
taste preference. In developing countries, the addition of zinc supplementation in
patients older than 6 months of age with diarrhea has been shown to have
improved outcomes however current evidence does not show a benefit in wellnourished children in settings with low prevalence of zinc deficiency.
TABLE 22.4
ONDANSETRON DOSING FOR GASTROENTERITIS
Patient weight
(kg)

Dose

8–15
>15–30
>30

2-mg orally disintegrating tablet (½ tablet)
4-mg orally disintegrating tablet
8-mg orally disintegrating tablet

The amount of fluid to be administered is dependent on the degree of
dehydration. Mild dehydration reflects up to 5% weight loss, so 5% of the child’s
body weight (50 mL/kg) should be administered as small-volume frequent feeds.
Moderate dehydration represents up to 10% weight loss, so 10% of the child’s
weight (100 mL/kg) should be administered. An easy rule of thumb to remember
is that a mildly dehydrated patient can receive 1 mL/kg every 5 minutes and a
moderately dehydrated patient can receive 2 mL/kg every 5 minutes. As the child

tolerates the feeds, the volume can be increased as well as the frequency. The
rehydration should be completed over a 4-hour time frame ( Fig. 22.2 ). ORT has
been shown to be equivalent to IV fluid therapy in terms of rehydration efficacy
and it has been shown that it takes less time to institute therapy with ORT (i.e.,
teach the parents how to administer the fluids) than to start an IV line in a child,
and there is less staff time involved in administering care to these patients as well
as shorter ED stays. There are a significant number of patients with gastroenteritis
who will be unable to perform ORT and will subsequently require alternative
methods for rehydration. Nasogastric (NG) tube use is an acceptable alternative
as it has been shown to be as effective as IV hydration. They are relatively easy to


place, do not need radiographic confirmation of placement, and the patient does
not need to remain awake while receiving the rehydration solution. A small
feeding tube is better tolerated for fluid administration than a larger NG tube.
Since NG tubes are considered a very noxious intervention, practitioners and
parents may choose parenteral rehydration over NG.

FIGURE 22.2 Oral rehydration therapy.

Parenteral Rehydration
Approximately 20% of patients will be unable to tolerate oral syringe
administration of ORT because of persistent vomiting, high stool outputs, or
inability to cooperate. If the patient is unable to tolerate ORT or is severely
dehydrated, then administration of 20-mL/kg boluses of isotonic saline or lactated
Ringer solution intravenously would be appropriate. The number of boluses
required depends on the patient’s physiologic response to the fluid that has been
administered. Once the initial resuscitation phase is completed, the patient will
need to be reassessed to see if maintenance fluids are necessary for ongoing
losses or continued inability to tolerate ORT. For ages 28 days to 18 years, the

recommended maintenance fluid is D5NS with 20 mEq/L of potassium chloride.


Notable exceptions include patients with extremely voluminous watery diarrhea,
major burn patients who continue to require isotonic fluids, children with diabetic
ketoacidosis who do not require dextrose initially, and children with severe
metabolic derangements where rapid correction will lead to severe complications.
The fluid rate is determined by the estimated fluid deficit, ongoing losses, and
maintenance fluid requirements ( Fig. 22.3 ). Usually, 50% of the child’s fluid
deficit is given over the first 8 hours in addition to one-third of the daily
maintenance fluid requirements. In hypertonic states, after initial stabilization
with isotonic fluids, the replacement solution is given more slowly to allow
equilibration across the blood–brain barrier (see Chapter 100 Renal and
Electrolyte Emergencies ).
Parenteral rehydration via an IV catheter has been used extensively. The
advantages of IV rehydration are numerous including familiarity with the
procedure, widespread acceptance, and direct vascular access to rehydrate a
patient. There are disadvantages associated with IV catheter use, primarily
difficulty in obtaining access in dehydrated children, particularly those younger
than 3 years, pain associated with placement, and the time and resources required
for placement. Subcutaneous rehydration is a method to deliver fluids
parenterally that was common prior to the widespread use of IV catheters. There
is evidence that using human recombinate hyaluronidase (Hylenex) with a
subcutaneous catheter may be an alternative for mild and moderately dehydrated
children who have failed ORT. It is a method that can also be used as a bridge to
getting IV access in severely dehydrated patients however intraosseous access
should also be considered in the severely ill. Hyaluronidase temporarily dissolves
hyaluronic acid and allows fluid to be administered subcutaneously, which is
subsequently absorbed into the vascular system. Advantages of subcutaneous
fluid administration include ease of placement and decreased pain with insertion.

More research in this new modality is required.


FIGURE 22.3 Calculation of deficit therapy using the example of a child with estimated 10%
dehydration and emergency department (ED) weight of 9 kg.

CONCLUSION