Final answer:
The initial fluid bolus for a patient presenting with dark, tarry stools and symptoms of pallor, coolness, and clamminess should be 20 mL/kg to quickly replenish fluids and increase blood volume.
Step-by-step explanation:
When a patient presents with dark, tarry stools and symptoms of pallor, coolness, and clamminess, it may indicate internal bleeding and fluid loss. In such cases, the initial fluid bolus is typically 20 mL/kg to quickly replenish fluids and increase blood volume. This helps maintain blood pressure and perfusion to vital organs.