Pediatric Nephrology in the ICU

pp 19-33

Disorders of the Acid-Base Status

  • E. Al-KhadraAffiliated withCincinnati Children's Hospital Medical Center Critical Care

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Core Messages

  • Essentially all pediatric disorders, if severe enough, can lead to acid-base disturbances directly, as a result of therapy, or both.

  • Acid-base disorders need to be anticipated in all critically ill patients. Proactive monitoring of the acid-base status will allow the early recognition of derangements and the prevention of what could become a life-threatening state.

  • Acidosis is the most common acid-base derangement in the intensive care unit (ICU), with metabolic acidosis potentially indicating a more severe course and worse outcome.

  • A pH of <7.2 merely indicates a primary acidosis- inducing disorder. Further assessment of the type of acidosis and the presence of a mixed acid-base disorder requires measurement of pCO2, serum bicarbonate, albumin, and calculation of the anion gap.

  • The most commonly encountered causes of metabolic acidoses in the ICU are renal insufficiency, sepsis, and DKA, while acute respiratory distress syndrome (ARDS) and severe status asthmaticus are the usual suspects in respiratory acidoses.

  • Alkalosis, on the other hand, is less common in the ICU. Fluid status derangements and, especially, gastric fluid depletion are the usual underlying causes of metabolic alkaloses, whereas rapid respiration secondary to lung diseases, excessive mechanical ventilation, pain, or central nervous system processes are the common causes of respiratory alkaloses.

  • In the ICU, identification of acid-base derangements is followed by timely stabilization of the patient irrespective of the underlying cause. Depending on the severity of the derangement and the patient’s response to the stabilizing interventions, the underlying cause might also need to be aggressively sought and emergently reversed.

  • Identification of the underlying cause(s) of the acid-base disorder at hand may be the final step in the management of these patients, but plays an important role both in the prevention of worsening of the derangement and other complications as well as in the determination of the patient’s overall prognosis.