What is the SINGLE most appropriate immediate management for a known type 1 diabetic presenting with abdominal pain and fruity-smelling breath?

In a known type 1 diabetic presenting with abdominal pain and fruity-smelling breath, the symptoms suggest diabetic ketoacidosis (DKA), a serious complication that arises due to insulin deficiency. The fruity breath is characteristic of the ketones produced during DKA.

The immediate management for DKA typically begins with the administration of intravenous fluids, which is crucial for rehydrating the patient, correcting electrolyte imbalances, and diluting the high levels of glucose. Following fluid resuscitation, insulin should be administered to help decrease blood glucose levels and to halt the production of ketones, thereby addressing the root cause of the acidosis.

While intravenous dextrose may be considered in certain situations after initial treatment has stabilized a patient, it is not appropriate as an immediate response in this case since the patient is already hyperglycemic. Oral rehydration is not suitable for someone presenting with abdominal pain and signs of severe dehydration or DKA, and subcutaneous insulin administration is less efficient than intravenous insulin during an acute crisis, particularly when rapid effects are required.

Thus, the sequence of administering intravenous fluids followed by insulin is the most effective and appropriate immediate management for this presentation.