A 28-year-old woman with type 1 diabetes presents to the emergency department with nausea, abdominal pain and polyuria. Her capillary glucose is 26 mmol/L, venous pH 7.15 and ketones are elevated. After initial fluid resuscitation, what is the recommended starting rate of intravenous insulin infusion for adult diabetic ketoacidosis (DKA) according to contemporary Australian protocols?