Perfusion Index for Predicting Diabetic Ketoacidosis Severity in the Emergency Department

This prospective observational cohort study will evaluate whether the perfusion index measured at emergency department admission is associated with the severity of diabetic ketoacidosis in adults. The study will include 140 patients aged 18 years or older who are diagnosed with diabetic ketoacidosis in the emergency department. The perfusion index will be measured using pulse oximetry. Serum lactate measured as part of routine clinical care will also be recorded, and the lactate-to-perfusion index ratio will be calculated. The ability of the perfusion index, serum lactate, and the lactate-to-perfusion index ratio to predict diabetic ketoacidosis severity will be compared. Their associations with time to diabetic ketoacidosis resolution, intensive care unit admission, hospital and intensive care unit length of stay, mechanical ventilation, vasopressor use, and in-hospital mortality will also be evaluated. No treatment will be assigned by the investigators, and all patients will receive routine clinical care.

Inclusion Criteria: 1. Age 18 years or older. 2. Diagnosis of diabetic ketoacidosis in the emergency department. 3. Ability to obtain perfusion index and serum lactate measurements during the initial assessment after admission. 4. Provision of written informed consent by the patient or, when necessary, the patient's legally authorized representative. Exclusion Criteria: 1. Pregnancy. 2. Trauma, major bleeding, or hemorrhagic shock. 3. Cardiac arrest. 4. Conditions that may prevent reliable perfusion index measurement, including advanced hypothermia, severe peripheral arterial disease, or amputation, burns, severe edema, or deformity at the measurement site. 5. Advanced chronic liver failure. 6. End-stage renal disease or dialysis treatment. 7. Inability to obtain the essential study variables or presence of missing data. 8. Refusal to participate in the study. 9. Repeat emergency department presentation by the same participant; only the first presentation will be included.