An 8-year-old boy, who weighs 30 kg, was found at the site of a motor vehicle accident (MVA). He has arrived in the OR for exploratory laparotomy. He has not received any sedation or pain medication because he appeared “confused and lethargic.” He has a normal blood pressure, is tachycardic with thready distal pulses, and has cold extremities. In spite of a 20 mL/kg fluid bolus, the patient has produced only 5 mL of urine.
The normal estimated blood volume (EBV) in children over 1 year of age is 70 to 75 mL/kg, and in this previously normal 8-year-old boy who weighs 30 kg, his normal blood volume would be 2100 to 2250 mL. Unlike adults, children maintain stable blood pressure until reaching a 25% to 35% loss of their circulating blood volume. This is related to their high sympathetic tone, which produces profound peripheral vasoconstriction in an effort to maintain blood pressure, making tachycardia an earlier sign of volume depletion than hypotension. Pediatric patients with < 20% blood loss are tachycardic with weak thready pulses, have only a slight decrease in urine output, and can be irritable with normal mentation. With 25% blood loss, they are also tachycardic with weak and thready pulses, but urine output is decreased, andthey are often confused and lethargic. With 40% blood loss, there is frank hypotension, usually tachycardia, urine output is zero (anuric), and the patient may be comatose. At times, patients with > 40% blood loss may be bradycardic due to the marked decrease in the amount of blood returning to the heart for pumping. This patient is most likely approximately 25% depleted and not in the < 20% range because his blood pressure is normal with tachycardia, oliguria, and confusion and lethargy