A 2-year-old, previously healthy boy is brought to the emergency department due to a 4-day history of poor feeding, diarrhea, and abdominal pain. The patient has had 5-7 bowel movements every day for the past 4 days. Temperature is 36.8 C (98.2 F) and blood pressure is 65/42 mm Hg. On physical examination, the patient is lethargic. Mucous membranes are dry, and the eyes are sunken. The lungs are clear to auscultation. No murmurs are heard. Abdominal examination shows distension and tenderness; bowel sounds are hyperactive throughout. Which of the following changes is most likely present in this patient?

Question

A 2-year-old, previously healthy boy is brought to the emergency department due to a 4-day history of poor feeding, diarrhea, and abdominal pain.  The patient has had 5-7 bowel movements every day for the past 4 days.  Temperature is 36.8 C (98.2 F) and blood pressure is 65/42 mm Hg.  On physical examination, the patient is lethargic.  Mucous membranes are dry, and the eyes are sunken.  The lungs are clear to auscultation.  No murmurs are heard.  Abdominal examination shows distension and tenderness; bowel sounds are hyperactive throughout.  Which of the following changes is most likely present in this patient?

Quizplus · Accepted Answer

11ec160b_3c99_3ec2_9249_83dcd258b3ea_MD0001_00 This patient has had several days of poor oral intake and diarrhea and now has signs of hypovolemia (eg, dry mucous membranes, sunken eyes) and shock (eg, lethargy, severe hypotension). With shock, there is poor organ and tissue perfusion that leads to tissue hypoxia with increased anaerobic metabolism and consequent lactic acidosis. In response to the reduction in pH caused by metabolic acidosis there is increased ventilation to increase CO₂ exhalation (ie, compensatory respiratory alkalosis). Severe diarrhea causes loss of bicarbonate in the stool, further contributing to metabolic acidosis and a compensatory increase in ventilation in this patient. (Choices A, B, and E) The reduced cardiac output in hypovolemic shock stimulates arteriolar vasoconstriction to increase systemic vascular resistance and help increase blood pressure. This reduces arteriolar capacitance. There is also contraction of venous smooth muscle to cause venular constriction and help increase venous return to the heart. The constricted vasculature reduces extravasation of intravascular fluid. In contrast, septic shock involves peripheral vasodilation with relaxation of vascular smooth muscle, increased vascular capacitance, and extravasation of intravascular fluid. (Choice C) Blood volume is markedly decreased in hypovolemic shock, leading to decreased central venous pressure. Central venous pressure is increased in cardiogenic shock and obstructive shock. Educational objective: Hypovolemic shock results from markedly decreased blood volume, which reduces central venous pressure and cardiac output and leads to increased systemic vascular resistance (peripheral vasoconstriction). Shock causes reduced organ and tissue perfusion, which leads to lactic acidosis (metabolic acidosis) and a compensatory increase in ventilation (ie, compensatory respiratory alkalosis).

A 2-Year-Old, Previously Healthy Boy Is Brought to the Emergency