Stage 3 — Prioritize hypotheses. A 42-year-old client with type 1 diabetes has had nausea, vomiting, and abdominal pain for 2 days and has taken no basal or bolus insulin for 36 hours. She drinks wine socially, none in 2 weeks. BP is 100/64, HR 112, RR 26 with deep, regular breathing, temperature 37.2°C (99°F), and SpO2 98% on room air. She is alert and oriented, and her oral mucosa is dry. Results: glucose 478 mg/dL, beta-hydroxybutyrate 6.8 mmol/L, venous pH 7.18, bicarbonate 9 mmol/L, and serum potassium 5.8 mmol/L. Additional results: sodium 134 mmol/L, anion gap 24 mmol/L, effective osmolality 295 mOsm/kg, lactate 1.6 mmol/L, and blood alcohol undetectable. Complete the diagram by selecting the condition the client is most likely experiencing, 2 actions the nurse should take to address that condition, and 2 parameters the nurse should monitor to assess the client's progress.

Quick answer
Diabetic ketoacidosis; begin 0.9% sodium chloride at 1 L/h and start the prescribed IV regular insulin infusion; monitor serum potassium every 2 hours and the anion gap with serum bicarbonate.

Why this is correct
The client meets all three DKA criteria: hyperglycemia (478 mg/dL), ketonemia (beta-hydroxybutyrate 6.8 mmol/L), and a high anion gap metabolic acidosis (venous pH 7.18, bicarbonate 9 mmol/L), precipitated by 36 hours without insulin. Isotonic fluid corrects the volume deficit shown by HR 112, BP 100/64, and dry mucosa. Insulin is safe to start because potassium is above 3.5 mmol/L; it stops ketone production and closes the anion gap. Insulin drives potassium into cells, so potassium is rechecked frequently and replaced once it falls into the normal range.

Easy analogy or mental picture
Picture a car running on the wrong fuel (fat) because the key (insulin) is missing: refill the radiator (fluids), put the key back (insulin), and watch the battery gauge (potassium), because turning the key drains it fast.

Memory hook
"Fluid in, key in, watch K; the gap tells you when it's over."

NCLEX decision rule
In DKA, give isotonic fluid and start IV insulin only when potassium is at least 3.5 mmol/L; resolution is judged by acid-base values and the anion gap, while potassium is trended to prevent hypokalemia.

Why the other choices are wrong
Adding potassium to the first liter is right later, but not while potassium is 5.8 mmol/L. Bicarbonate is reserved for pH below 7.0. Restricting fluids ignores the volume deficit that drives the tachycardia and low-normal blood pressure. HHS is excluded by an effective osmolality of 295 mOsm/kg with severe acidosis; alcoholic ketoacidosis by no alcohol for 2 weeks, an undetectable blood alcohol, and marked hyperglycemia; and sepsis-related lactic acidosis by a temperature of 37.2°C and a lactate of 1.6 mmol/L. Osmolality, blood alcohol, and lactate track those differentials rather than DKA resolution.