Antenatal care, fetal wellbeing and medical disorders in pregnancy practice

A 24-year-old woman at 10 weeks of pregnancy has vomited repeatedly for three weeks and has lost 7 kg. She is alert, with a pulse of 104 beats/minute and blood pressure of 105/68 mmHg; urine contains 4+ ketones, serum potassium is 2.8 mmol/L (3.5–5.2) and serum sodium is 136 mmol/L (135–145). She has eaten very little during the past fortnight and has not received intravenous treatment. Which one of the following should be given before intravenous dextrose, if dextrose is required?