What this area covers
Interns and residents in Australian hospitals manage ward calls, fluids, prescribing and deteriorating patients, often overnight. This page is for interns, residents and IMGs starting their first Australian hospital job, and focuses on safe, practical decisions.
High-yield topics
| Topic | What to know |
|---|---|
| Maintenance fluids | Water, sodium and potassium needs; reassess daily |
| Hyponatraemia | Assess volume; correct chronic cases slowly |
| Potassium | Replacement limits for peripheral lines |
| AKI | Stop nephrotoxics, assess volume |
| Transfusion | Restrictive thresholds |
Worked example
Worked question · Sodium
What is a safe maximum rise in sodium in 24 hours in chronic hyponatraemia?
- A 8 to 10 mmol/L
- B About 20 mmol/L
- C About 25 mmol/L
- D No limit if symptomatic
- E About 30 mmol/L
Show the reasoning
Answer A. Limit correction to about 8 to 10 mmol/L in 24 hours (lower in high-risk patients) to avoid osmotic demyelination.
A short study plan
| Week | Focus |
|---|---|
| 1 | Core principles |
| 2 | Common ward calls |
| 3 | Timed questions and review |
Do a short timed set most days and review every explanation, including the options you ruled out.
Common traps
- Acting without checking local protocols.
- Delaying escalation.
- Poor documentation.
Free sample fluids and electrolytes questions
Questions from our Junior Doctor bank. Choose your answer, then open the explanation.
Mr Silva, 70 kg, is nil by mouth for 24 hours before surgery. Kidney function and electrolytes are normal. Roughly how much water does he need for maintenance over 24 hours?
- AAbout 4.5 litres
- BAbout 500 mL
- CAbout 1 litre
- DAbout 3.5 litres
- EAbout 2 litres
Show answer and explanation
Answer E. Adult maintenance water is about 25 to 30 mL/kg per day, so about 1.75 to 2.1 litres for 70 kg, with about 1 mmol/kg/day of sodium and potassium and some glucose. Adjust for losses, kidney and heart function, and review daily. What to do next: Add about 1 mmol/kg/day each of sodium and potassium and 50–100 g of glucose; reduce volumes in frail, cardiac or renal patients and review fluids daily.
Learning point: Adult maintenance fluid: about 25 to 30 mL/kg/day of water, with about 1 mmol/kg/day sodium and potassium.
Mr Ito, 50, has potassium 3.2 mmol/L. He is eating and drinking normally and has no ECG changes. What is the best way to replace potassium?
- AIV potassium 40 mmol over 1 hour via the cannula
- BNo replacement is needed
- CIV potassium as a slow push
- DPotassium in a 5% glucose bolus
- EOral potassium chloride supplements
Show answer and explanation
Answer E. Mild hypokalaemia in a patient who can take oral medicines is best treated with oral potassium chloride, which is safer than IV. Check magnesium and look for the cause. What to do next: Check magnesium, recheck potassium in 24–48 hours, and treat the cause (diuretics, diarrhoea, vomiting).
Learning point: Mild hypokalaemia with a working gut: oral potassium, check magnesium.
Mr Fox, 82, with severe heart failure (EF 20%), is nil by mouth for a procedure. Kidney function is normal. How should his maintenance fluids be prescribed?
- AOnly 5% glucose at 200 mL/h
- BNo fluid at all for 48 hours
- CReduced volumes with close monitoring of balance
- DStandard 3 litres a day of 0.9% saline with potassium
- ERapid boluses to keep urine high
Show answer and explanation
Answer C. Patients with severe heart failure need smaller maintenance volumes and lower sodium, with daily weights, fluid balance and examination for overload, and early resumption of oral intake. What to do next: Weigh daily, review fluid balance and electrolytes, and restart oral intake and usual heart failure medicines as soon as possible.
Learning point: Heart failure: lower maintenance volumes, daily weight and balance checks.
Practise more fluids and electrolytes questions free
Every fluids and electrolytes subtopic in our bank
The bank holds 50 fluids and electrolytes questions across 50 subtopics. You can filter by any of them, build a custom block and track your accuracy subtopic by subtopic.
- Acute kidney injury1
- Albumin infusion1
- Assessing fluid status1
- Blood products1
- Bowel preparation and hyponatraemia1
- Burns fluids1
- Calculating sodium content1
- Contrast and kidneys1
- Corrected calcium1
- Correcting chronic hyponatraemia1
- Diabetes insipidus after pituitary surgery1
- Diabetic ketoacidosis1
- Diarrhoea and potassium1
- Fasting patient with type 1 diabetes1
- Fluid challenge1
- Fluid resuscitation1
- Fluids in heart failure1
- Fresh frozen plasma1
- Hartmann's solution1
- High-output stoma1
- Hypercalcaemia1
- Hyperchloraemic acidosis1
- Hyperkalaemia without ECG change1
- Hypernatraemia1
- Hyperosmolar hyperglycaemic state1
- Hyperphosphataemia in kidney disease1
- Hypocalcaemia1
- Hypokalaemia1
- Hypomagnesaemia1
- Hypophosphataemia1
- IV potassium1
- Magnesium and potassium1
- Maintenance fluids1
- Maintenance potassium requirement1
- Metformin-associated lactic acidosis1
- Platelet transfusion1
- Post-operative hyponatraemia1
- Pseudohyponatraemia with hyperglycaemia1
- Raised anion gap acidosis1
- Reading the fluid balance chart1
- Refeeding syndrome1
- Rhabdomyolysis1
- Severe hyponatraemia1
- SIADH1
- Stopping IV fluids1
- Thiazide-associated hyponatraemia1
- Transfusion threshold1
- Tumour lysis syndrome1
- Urine output targets1
- Vomiting and alkalosis1
Common questions
Is this relevant to IMGs?
Yes. Australian hospital systems, protocols and escalation pathways may differ from your previous experience.
Should I follow local protocols?
Always. This page explains principles; local policies apply.
Sources
Clinical content is summarised from current Australian guidance at the date above. Guidelines change, so always check the latest edition.