Gastric losses (emesis or nasogastric suction) Pyloric stenosis Diuretics (loop or thiazide) Chloride-losing diarrhea Chloride-deficient formula Cystic fibrosis (sweat losses of chloride) Posthypercapnia (chloride loss during respiratory acidosis)
Measurement of the urinary chloride concentration is the most helpful test in differentiating among the causes of a metabolic alkalosis. The history usually suggests a diagnosis, although no obvious explanation may be present in the patient with bulimia, surreptitious diuretic use, or an undiagnosed genetic disorder, such as Bartter syndrome or Gitelman syndrome.
The approach to therapy of metabolic alkalosis depends on theseverity of the alkalosis and the underlying etiology. In childrenwith a mild metabolic alkalosis ([HCO3–] < 32 mEq/L), intervention is often unnecessary. Patients with chloride-responsivemetabolic alkalosis respond to correction of hypokalemia andvolume repletion with sodium and potassium chloride, butaggressive volume repletion may be contraindicated if mildvolume depletion is medically necessary in the child receiving diuretic therapy. In children with chloride-resistant causesof a metabolic alkalosis that are associated with hypertension,volume repletion is contraindicated because it exacerbatesthe hypertension and does not repair the metabolic alkalosis.Treatment focuses on eliminating or blocking the action of theexcess mineralocorticoid. In children with Bartter syndromeor Gitelman syndrome, therapy includes oral potassium supplementation and potassium-sparing diuretics.
During a respiratory acidosis, there is a decrease in the effectiveness of CO2 removal by the lungs. The causes of a respiratory acidosis are either pulmonary or nonpulmonary (Table 37-4). A respiratory alkalosis is an inappropriate reduction in the blood CO2 concentration. A variety of stimuli can increase the ventilatory drive and cause a respiratory alkalosis (Table 37-5). Treatment of respiratory acid-base disorders focuses on correction of the underlying disorder. Mechanical ventilation may be necessary in a child with a refractory respiratory acidosis.
overdose) Disorders of the spinal cord, peripheral nerves, or neuromuscular junction (botulism or Guillain-Barré syndrome)
Colletti JE, Brown KM, Sharieff GQ, et al: The management of children with gastroenteritis and dehydration in the emergency department, J Emerg
Med 38:686–698, 2010
Friedman A: Fluid and electrolyte therapy: a primer, Pediatr Nephrol 25:843–846, 2010
Gennari FJ: Pathophysiology of metabolic alkalosis: a new classification based on the centrality of stimulated collecting duct ion transport, Am J
Kidney Dis 58:626–636, 2011
Greenbaum LA: Pathophysiology of body fluids and fluid therapy. In
Kliegman RM, Stanton BF, St. Geme JW, et al, editors: Nelson textbook of pediatrics, ed 19, Philadelphia, 2011, Elsevier Science, pp 212–249
Kraut JA, Madias NE: Differential diagnosis of nongap metabolic acidosis: value of a systematic approach, Clin J Am Soc Nephrol 7:671–679, 2012
Pepin J, Shields C: Advances in diagnosis and management of hypokalemic and hyperkalemic emergencies, Emerg Med Pract 14:1–17, 2012
Simpson JN, Teach SJ: Pediatric rapid fluid resuscitation, Curr Opin Pediatr 23:286–292, 2011