Fluids & Electrolytes Pediatric Emergency Medicine Boston Medical Center Boston University School of Medicine

Objectives  To discuss:  Maintenance Fluids and Electrolyte Requirements  Types of Dehydration  Management of Dehydration  Electrolyte Abnormalities

Composition of Body Compartments  Total Body Water (TBW)= 50-75% of Total Body Mass  TBW = Intracellular Fluid (ICF) + Extracellular Fluid (ECF)  ICF = 2/3 of TBW  ECF = 1/3 of TBW -- 25% of body weight  ECF = Plasma (intravascular) + Interstitial fluid

Body Water Compartments Related to Age

Regulation of Body Fluids and Electrolytes  Mechanism to Regulate ECF volume  Anti-Diuretic Hormone (ADH) Kidney = Increase water reabsorption ADH secretion is regulated by tonicity of body fluids  Thirst Not physiological stimulated until plasma osmolality is >290

Regulation of Body Fluids and Electrolytes  Aldosterone Released from the adrenal cortex –Decrease circulating volume –Stimulation by Renin-Angiotensin Aldosterone axis –Increase plasma K Enhanced renal reabsorption of Na in exchange for K (>Na = expansion of ECF)  Atrial Natriuretic Factor Secreated by the cardiac atrium in response to atrial dilatation (regulates blood volume) Inhibits Renin secretion Increase GFR and Na excretion

Daily Maintenance Requirements

4cc, 2cc, 1cc rule  4 cc for the first 10 kg  2 cc for the next 10 kg  1 cc for each kg after  Example: 27 kg child – 4 cc for the first 10 kg = 40cc – 2 cc for the next 10 kg = 20cc – 1 cc for each kg after = 7 cc 67 cc/hr

Maintenance Requirements  Maintenance Fluids: weight dependent & age dependent:  (NS =0.9% Saline =154 meq Na/liter)  age >2 -3 years: D5 0.5 NS + 20 meq KCl/liter  Up to age 2-3 years: D5 0.2 NS + 20 meq KCl/liter D5 = 50 gm/liter = 5 g/dl Newborns often require D10 = 100 gm/liter = 10 gm/dl

Dehydration  Epidemiology:  One of the most common medical problems  In the U.S. - 10% of all pediatric admissions  Worldwide, over 3 million children under 5 years die from dehydration

Estimation of Dehydration

Dehydration  Classification  Isotonic Serum Sodium mEq  Hypotonic Serum Sodium < 130 mEq  Hypertonic Serum Sodium >150 mEq

Management of Dehydration  General Principles:  Supply Maintenance Requirements  Correct volume and electrolyte deficit  Replace ongoing abnormal losses

Management of Dehydration  Oral Rehydration:  Effective for mild and some moderate dehydrations  Child may be able to tolerate PO intake  Small aliquots as tolerated Mild: 50 cc/kg over 4 hours Moderate: 100 cc/kg over 4 hours  2 types of oral solution Maintenance Rehydration

Commercial Oral Solutions

Management of Dehydration: IV  Replacement of Fluid Deficit Based on % Dehydration :  Example: 5 kg child who is 6% dehydrated: 5 x 60cc/kg fluid deficit (cc) = wt x % dehydration fluid deficit (cc) = wt in kg (1000cc/kg) x (1/100) estimate of dehydration fluid deficit (cc) = wt x 10 x estimate of dehydration fluid deficit (cc) = 5 x 10 x 6 fluid deficit (cc) = 300 cc

Management of Dehydration: IV  Initial: NS or LR 20 cc/kg Bolus in first hour  Then Remainder of Deficit In previous example: total fluid deficit = 300cc for 5 kg child who is 6% dehydrated = 60cc/kg Replacement: –first hour: 20 cc/kg = 20 x 5 = 100 cc –replace the rest: 40 cc/kg or = 200 cc –The type of fluid used and the rate of infusion depends on the age and Na status of the patient: »for isonatremic dehydration: correct deficits of next 7 hours »200cc over 7 hours = 28 cc/hr

Hyponatremia  Predisposing Factors  Diabetes mellitus (hyperglycemia)  Cystic fibrosis  CNS disorders ( SIADH)  Gastroenteritis  Excessive water intake (formula dilution)  Diuretics (thiazides and furosemide)  Renal disease

Hyponatremia  Hyponatremic Dehydration  Hypovolemic Hyponatremic Dehydration High urine output and Na excretion Increase in atrial natriuretic factor  Euvolemic Hyponatremic Dehydration ADH mediated water retention  Hypervolemic Hyponatremic Dehydration Edematous disorder (nephrotic syndrome, CHF, cirrhosis) Water intoxication

Hyponatremia  Acute Hyponatremia (<24 hours)  Early Onset (Serum Sodium <125 meq/L) Nausea Vomiting Headache  Later or Severe (Serum Sodium <120 meq/L) Seizure Coma Respiratory arrest

Hyponatremia  Chronic Hyponatremia (>48 hours)  Lethargy  Confusion  Muscle cramps  Neurologic Impairment

Hyponatremia  Management  Na Deficit: Na Deficit = (Na Desired - Na observed) x 0.6 x body weight(kg)  Replace half in first 8 hours and the rest in the following 16 hours  Rise in serum Na should not exceed 2 mEq/L/h to prevent Central Pontine Myelinolysis (? Existence in children)  In cases of severe hyponatremia (<120 mEq) with CNS symptoms: 3% NaCl 3-5 ml/kg IV push for hyponatremia induced seizures –6 ml/kg of NaCl will raise serum Na by 5 mEq/L

Hypernatremia  Hypernatremia leads to hypertonicity  Increase secretion of ADH  Increase thirst  Patients at risk  Inability to secrete or respond to ADH  No access to water

Hypernatremia  Etiology  Pure water depletion Diabetes insipidus (Central or Nephrogenic)  Sodium excess Salt poisoning (PO or IV)  Water depletion exceeding Na depletion Diarrhea, vomiting, decrease fluid intake  Pharmacologic agents Lithium, Cyclophosphamide, Cisplatin

Hypernatremia  Signs and symptoms  Disturbances of consciousness Lethargy or Confusion  Neuromuscular Irritability Muscle twitching, hyperreflexia  Convulsions  Hyperthermia Skin may feel thick or doughy

Hypernatremia  Management  Normal Saline or Ringer lactate to restore volume  Hypotonic solution (D5 1/4 NS) to correct calculated deficit over 48 hours Water Deficit – Normal body H20 - Current body H20 Current body water – 0.6 x body weight (kg) x Normal Na/Observed Na Normal Body water – 0.6 x body weight (kg)  Decrease Na concentration at a rate of 0.5 mEq/hr or ~ 10 mEq/day: Faster correction can result in Cerebral Edema

Potassium  Most abundant intracellular cation  Normal serum values mEq  Abnormalities of serum K are potentially life- threatening due to effect in cardiac function

Hypokalemia  Diagnosis  Symptoms Arrhythmias Neuromuscular excitability (hyporreflexia, paralysis) Gastrointestinal (decreased peristalsis or ileus)  Serum K < 3mEq/L  ECG: Flat T waves Short P-R interval and QRS U waves

Hypokalemia Nutritional GI Loss Renal Loss Endocrine Poor intake Diarrhea Renal tubular acidosis Insulin therapy IVF low in K Vomiting Chronic renal disease Glucose therapy Anorexia Malabsorbtion Fanconi's syndrome DKA Intestinal fistula Gentamicin, Hyperaldosteronism Laxatives Amphotericin Adrenal adenomas Enemas Diuretics Mineralocorticoids Bartter's syndrome Bartter’s syndrome: Hypereninemia and hyperaldosteronism

Hypokalemia  Management:  Cardiac Arrhythmias or Muscle Weakness KCl IV (cardiac monitor)  PO K - Depend of etiology Hypophoshatemia = KPO4 Metabolic acidosis = KCl Renal tubular acidosis = K citrate

Hyperkalemia  Differential Diagnosis  Pseudohyperkalemia - from blood hemolysis  Metabolic Acidosis  Chronic Renal Failure  Congenital Adrenal Hyperplasia Females = Usually Dx at birth - Ambiguous Genitalia Males = Dehydration, hyponatremia, hyperkalemia  Medications ACE inhibitors and NSAID’s

Hyperkalemia  Diagnosis:  Symptoms Cardiac Arrhythmias Paresthesias Muscle weakness or paralysis  ECG Peaked T waves Short QT interval (K>6 mEq) Depressed ST segment Wide QRS (K>8 mEq)

Hyperkalemia  Management  Close cardiac monitoring  Life -threatening hyperkalmia Intravenous Calcium - rapid onset, duration< 30 min NaHCO3 or glucose and insulin  Ion exchange resins Sodium polystyrene sulfonate (Kayexelate) – PO or Enema  Hemodyalisis