A 27-year-old woman with type 1 diabetes presents with abdominal pain, vomiting, polyuria and polydipsia. On examination she is tachypnoeic with Kussmaul respirations. Capillary glucose is 25 mmol/L, venous pH 7.12, bicarbonate 10 mmol/L, and serum ketones are elevated. According to standard diabetic ketoacidosis (DKA) management protocols used in Canada, what is the most appropriate initial fluid resuscitation?