Final answer:
For a critically distressed 1-year-old child showing signs of shock after intubation and securing an IV line, the next step is to administer a rapid bolus of 20 mL/kg of isotonic crystalloid to improve circulation.
Step-by-step explanation:
The intervention that should be next for a 1-year-old child presenting with a history of irregular breathing, faint central pulse, and other signs of critical distress, after intubation and ventilation with 100% O2 and establishment of IV access in the emergency department (ED), with a heart rate (HR) of 150/min and a systolic blood pressure (SBP) of 74 mmHg, is C. Rapid bolus of 20 mL/kg of isotonic crystalloid. This is because the patient's clinical signs suggest significant circulatory compromise or shock, potentially from internal injury indicated by the abdominal findings. The immediate goal is to improve circulation and perfusion, which is achieved by expanding the intravascular volume with a crystalloid fluid bolus.