1. Fluid Needs and Dehydration in Children

2. Fluid & Electrolytes: Regulation • Total body water (TBW)—50–75% of total body mass • Less TBW for obese people—can become dehydrated quickly • More TBW for infants—can become dehydrated quickly • ICF, ECF, Major electrolytes of plasma—Na+, Bicarbonate, protein (albumin) • Important on labs to note osmolality to diagnose imbalance • ADH secreted in water loss for renal conservation of water (triggered at 280 mOsm/kg) • Thirst not physiologically stimulated until osmolality reaches 290 mOsm/kg • Goal of fluid replacement: providing maintenance, replenish prior losses, replace persisting losses

3. Fluid and Electrolytes: Regulation • 1 ml of water is needed for each Kcal expended. Water: Kcals – 1:1 Water needs and Caloric needs per unit of body weight in 24 hours. (Hay et al., 2012, chapter 23)

4. Let’s Try It • 40KG child • According to our chart needs: 1500 + 20(20) = 1900 kcal and ml per day. A 24 hour drip rate would be about 80 ml per hour. Add in any previous losses or current continued losses.

5. Dehydration • Most common problem in clinical peds. • GI disease common culprit (Diarrhea!) • Infants and young children highest risk

6. Dehydration • Clinical History: fluid intake, frequency, amount of vomiting, diarrhea, urine output or number of wet diapers in 24 hours, duration or degree of fever, types of medications, any underlying disease • Need not only ill weight but last normal body weight (accuracy of office weights is critical) • Physical Exam: V/S, heart rate, cap refill, dryness of lips, mucous membranes, lack of tears, lack of external jugular venous filling when supine, sunken fontanelle, oliguria, and altered mental status. *These signs warrant immediate attention.

7. Dehydration • Alterations in disease or body that increase fluid requirements: • fever—12% for every degree C • Hyperventilation—10–60ml • Sweating—10-25ml/kg • Hyperthyroidism—25–50% • GI and renal disease • Clinical signs and degree of dehydration • Body weight—3–5% mild, 6–10% moderate, 11–15% severe • Turgor—normal (mild), decreased (moderate), markedly decreased (severe) • Pulse—normal (mild), sl. Increase (moderate), tachycardia (severe), • Cap refill—2–3s (mild), 3–4s (moderate), > 4 s(severe) • Tears—decreased (mild) ---- absent (severe) • Urinary output—mild oliguria (mild) --- anuria (Severe) (Hay et al., 2012)

8. Electrolyte Needs for Maintenance • 3-4 mEq Na+/100kcal • 30-40 mEq Na+/L • 2mEq K+/100kcal • 20 mEq K+/L • *No hypotonic fluids to prevent hyponatremia • Electrolyte compositions of body fluids • Diarrhea: 10–90 Na+ mEq/L, 10–80 K+ mEq/L, 40 HCO3- mEq/L • Gastric: 20–80 Na+ mEq/L, 5–20 K+ mEq/L, 0 HCO3- mEq/L • Small intestine –> Sodium concentration (otherwise similar potassium and bicarbonate)