Fluids and Electrolytes

Chapter 34 Fluids and Electrolytes



Kathy N. Shaw, MD, MSCE



1 How do you estimate the extent of dehydration in children?


Since serial weights on the same scale are rarely available in the emergency department (ED) setting, rely on the physical examination to estimate the degree of fluid loss (Table 34-1).



Table 34-1 Clinical Findings of Dehydration

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2 What are the most reliable clinical examination findings that help you predict how dry a child has become?


An abnormal capillary refill time is probably the most reliable sign for predicting 5% dehydration in children. However, a combination of examination signs is better than any individual sign. The presence of two or more of the following four clinical measures seems most reliable in predicting dehydration:



image “Ill” general appearance


image Lack of tears


image Capillary refill time at the fingertip > 2 seconds


image Dry mucous membranes


Gorelick MH, Shaw KN, Murphy KO: Validity and reliability of clinical signs in the diagnosis of dehydration in children. Pediatrics 99:e6, 1997.


Steiner MJ, DeWalt DA, Byerley JS: Is this child dehydrated? JAMA 291:2746–2754, 2004.



3 How does the extent of dehydration translate into fluid lost?


For each kilogram of weight loss, 1 L of fluid was lost. Using weight obtained in the ED and your estimate of the percentage dehydration, you can calculate the “well” or rehydrated weight. The difference between the estimated well weight and current weight is converted into liters or cubic centimeters. For example, a 9-kg, ill-appearing baby presents with dry mucous membranes, crying with no tears, and a capillary refill time of > 2 seconds. She is estimated to have lost 10% of her body weight (severe dehydration).




image




4 How much fluid and what type do you use for a “bolus” to begin IV hydration?


The first objective in treating a child with dehydration is to restore intravascular volume and treat shock. Isotonic fluid, such as normal saline or Ringer’s lactate, should be used. Give boluses of 20 mL/kg, and reassess the child. The goal is to restore blood pressure, reduce heart rate, restore perfusion to the tissues (return of capillary refill < 2 seconds), improve mental status or general appearance, and produce urine. If initial fluid boluses > 60 mL/kg are needed, reconsider the diagnosis and management plan.



5 Should 5% dextrose in water be used as a fluid bolus for dehydration?


No, 5% dextrose in water (D5W) should not be used to treat dehydration. Only isotonic crystalloid fluid should be used for treatment of dehydration in pediatrics. Giving dextrose along with a large fluid bolus can lead to hyperglycemia.



6 Are there any children who should not receive a rapid fluid bolus?


Children with diabetic ketoacidosis or hypernatremic dehydration (serum sodium level > 150 mEq/dL) who are in a hyperosmolar state require slower and more cautious fluid resuscitation. Clearly, uncompensated shock (hypotension) must be treated rapidly, but 10-mL/kg boluses of normal saline should be used and the child reassessed after each bolus. Also administer fluids more cautiously to children in cardiogenic shock (heart failure).



7 What stock should be used after the initial IV bolus or if the child is not dehydrated?


Generally, D5¼ normal saline (NS) or D5½ NS, with 10 mEq potassium chloride/L added if the child has urinated. Use D5½ NS in children who have had < 20 mL/kg NS boluses or who have hyponatremic dehydration (serum sodium level < 130 mEq/dL). Children with burns, pyloric stenosis with hypochloremia, and diabetic ketoacidosis are usually kept on a normal saline infusion in the ED.



8 At what rate should fluids run on a child who has orders to receive nothing by mouth? How is this maintenance rate adjusted for the dehydrated child?


All children who are unable to drink should receive maintenance fluids, and if they are dehydrated, the rate is higher to replace some of the remaining fluid deficit. Calculate all rates by using the child’s well or rehydrated weight. Increase rates above maintenance if the child is febrile or has increased insensible or gastrointestinal losses.




image



Example: Maintenance rate for a 16-kg child: 40 mL/h (first 10 kg) + 6 kg × 2 mL = 12 mL/h (next 6 kg) or 52 mL/h (if the child is febrile, add 10% more, or 55–60 mL/h). To determine the rate for the dehydrated child, half of the total fluid deficit (minus the fluid boluses already given) is added to the maintenance rate for the first 8 hours. The other half of the deficit is added to the maintenance rate over the next 16 hours (hopefully outside of the ED!). For children with hypertonic dehydration, the remaining fluid deficit after initial boluses is replaced evenly over the next 48 hours.


Example: A 9-kg dehydrated baby was given 400 mL of NS (40 mL/kg) as an initial fluid bolus. The fluid deficit was 1000 mL. Half of the deficit is 500 ML. Since 400 mL was already given, 100 mL of the deficit should be added to the maintenance rate over the next 8 hours. Thus, 100 mL/8 h = 12.5 mL/hr should be added to the maintenance rate of 40 mL/hr (based on 10-kg “well” weight), or 52 mL/hr of D5¼ NS should be ordered.


Shaw KN, Spandorfer P: Dehydration. In Fleisher GR, Ludwig S, Henretig FM (eds): Textbook of Pediatric Emergency Medicine, 5th ed. Philadelphia, Lippincott Williams & Wilkins, 2006, pp 233–238.



KEY POINTS: DEHYDRATION




1 The first objective in treating a child with severe dehydration is to restore intravascular volume and treat shock, regardless of etiology.


2 In all children receiving IV fluids, the serial electrolytes and urine output should be monitored and fluid rates adjusted on the basis of the child’s hydration status, urine output, and presence or absence of increased ADH.


3 Compared with IV therapy, oral rehydration therapy is effective in treating dehydration in most children, has fewer complications, and may be faster.

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Sep 1, 2016 | Posted by in EMERGENCY MEDICINE | Comments Off on Fluids and Electrolytes

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