08-21-2009, 10:11 PM
15. A previously healthy 6-month-old boy is brought to the physician because of a 12-hour history of vomiting and diarrhea. He vomits after all feedings, the vomitus does not contain blood or bile. His mother says that he has had fewer wet diapers than usual during this period. He appears dehydrated and is crying without tears. He is at the 50th percentile for length and 30th percentile for weight. He appears lethargic. His temperature is 38°C (100.4°F), pulse is 180/min, and blood pressure is 60/40 mm Hg. Examination shows sunken eyes, dry mucous membranes, and a sunken anterior fontanel. Arterial blood gas analysis on room air shows:
pH 7.2
PCO2 38 mm Hg
PO2 90 mm Hg
Which of the following is the most likely explanation for this patient's arterial blood gas findings?
O A) Excessive metabolic acid formation
O B) Impaired ventilation
O C) Increased chloride loss (Ã increase HCO3 which is not the case here)
O D) Increased CO2 concentration in the extracellular fluid
0 E) Increased metabolic acid produced by the gastrointestinal tract