Perfusion Index for Predicting Diabetic Ketoacidosis Severity in the Emergency Department

This is a prospective, single-center observational cohort study of adults diagnosed with diabetic ketoacidosis in the emergency department. The primary objective is to evaluate the association between the perfusion index measured at admission and diabetic ketoacidosis severity.

Diabetic ketoacidosis severity will be classified as mild, moderate, or severe according to admission pH and serum bicarbonate levels. The admission perfusion index will be measured, when possible, after the patient has rested for at least five minutes, under conditions without movement or marked external light interference. Three consecutive perfusion index measurements will be obtained at each measurement time, and their median will be used in the analyses. The admission perfusion index measurement and serum lactate sampling will be performed within the same time period and, whenever possible, before intravenous fluid and insulin treatment is initiated. A further perfusion index measurement will be recorded at the fourth hour of treatment.

Serum lactate values obtained as part of routine clinical care will be recorded. The lactate-to-perfusion index ratio will be calculated as serum lactate in mmol/L divided by the perfusion index percentage. The predictive performances of the perfusion index, serum lactate, and the lactate-to-perfusion index ratio for diabetic ketoacidosis severity will be evaluated and compared.

Secondary outcomes will include time to diabetic ketoacidosis resolution, intensive care unit admission, hospital length of stay, intensive care unit length of stay, mechanical ventilation within the first 24 hours, vasopressor use within the first 24 hours, and in-hospital mortality. The investigators will not assign any diagnostic or therapeutic intervention, and patient management will follow routine clinical practice.

Inclusion criteria

• Age 18 years or older.
• Diagnosis of diabetic ketoacidosis in the emergency department.
• Ability to obtain perfusion index and serum lactate measurements during the initial assessment after admission.
• Provision of written informed consent by the patient or, when necessary, the patient's legally authorized representative.

Exclusion criteria

• Pregnancy.
• Trauma, major bleeding, or hemorrhagic shock.
• Cardiac arrest.
• 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.
• Advanced chronic liver failure.
• End-stage renal disease or dialysis treatment.
• Inability to obtain the essential study variables or presence of missing data.
• Refusal to participate in the study.
• Repeat emergency department presentation by the same participant; only the first presentation will be included.