As a guideline for oral rehydration, 50 mL/kg of the ORSshould be given within 4 hours to patients with mild dehydration, and 100 mL/kg should be given over 4 hours to patientswith moderate dehydration. Supplementary ORS is given toreplace ongoing losses from diarrhea or emesis. An additional 10 mL/kg of ORS is given for each stool. Fluid intakeshould be decreased if the patient appears fully hydrated earlier than expected or develops periorbital edema. After rehydration, patients should resume their usual diet (breast milk,formula).
When rehydration is complete, maintenance therapy should be started, using 100 mL of ORS/kg in 24 hours until the diarrhea stops. Breastfeeding or formula feeding should be maintained and not delayed for more than 24 hours. Patients with more severe diarrhea require continued supervision. The volume of ORS ingested should equal the volume of stool losses. If stool volume cannot be measured, an intake of 10 to 15 mL of ORS/kg/hr is appropriate.
Parenteral nutrition (PN) is necessary when enteral feeding is inadequate to meet the nutritional needs of a patient. Enteral nutrition is always preferred because it is more physiologic, less expensive, and associated with fewer complications. Fewer complications are expected if at least some nutrition can be provided enterally.
A variety of clinical situations necessitate PN (Table 34-1).Acute PN is frequently given in an intensive care unit when there is poor tolerance of enteral feeds, potentially secondary to a transient ileus; concerns regarding bowel ischemia; or the risk of aspiration pneumonia. Short bowel syndrome is the most common indication for long-term PN; it may be caused by a congenital gastrointestinal anomaly or acquired after necrotizing enterocolitis (see Chapter 63). Some patients with a chronic indication for PN eventually may be transitioned to partial or full enteral feedings.
PN can be given via either a peripheral intravenous (IV) line or a central venous line. Long-term PN should be given via a central venous line (CVL). Acute PN may be given peripherally, although a temporary CVL often is used. Most children with cancer or receiving a bone marrow transplant have a
CVL. A peripherally inserted central catheter is an excellent source of central access for acute PN because of the lower risk for complications than with a standard CVL.
A peripheral IV line has two major limitations. First, it frequently fails, necessitating interruption of PN and potentiallypainful placement of a new line. Second, high-osmolality solutions cause phlebitis of peripheral veins; this limits the dextroseand amino acid content of peripheral PN. The dextrose contentof peripheral PN cannot be greater than 12%, with a lower limitif the amino acid concentration is high. Lipid emulsion has a low osmolality; therefore, it can be administered peripherallyvia the same IV line as the dextrose and amino acid solution. Patients can receive adequate nutrition via a peripheral IV line,but the volume of PN needs to be higher than is necessary whencentral access is available because of the limitations on dextrose and amino acid concentration. This situation may be problematic in patients who cannot tolerate larger fluid volumes.
PN can provide calories, amino acids, electrolytes, minerals, essential fatty acids, vitamins, iron, and trace elements. The calories in PN are from dextrose and fat. The amino acids in PN are a potential source of calories, but they should be used predominantly for protein synthesis. PN is given as two separate solutions: a dextrose plus amino acid solution and a 20% lipid emulsion. The dextrose solution has all of the other components of PN except for fat.