MD Acumen · PLAB 2 OSCE / CPSA course · free practice resources

Practice case P2-28 · Face-to-face · relative or carer · results sheet

Unwell after a stomach bug — interpreting the bloods

A 78-year-old man has been brought to the emergency department by his daughter after three days of vomiting and diarrhoea. His triage bloods are back and the nurse has asked you to see him. His daughter is at the bedside.

Reviewed and kept current

Station family: Data interpretation and acute management · 8-minute station · 1 min 30 s reading · Last editorial review: 16 October 2026 · Next scheduled refresh: 11 April 2027.

Candidate instructions

Read this as you would outside the room

You have 1 minute 30 seconds to read, then 8 minutes. Candidates: everything below this section is folded away — leave it closed until you have finished the station.

	Information
Your role	Foundation Year 2 doctor in the emergency department. The ED registrar is available by phone; the medical registrar and the renal team can be called. A staff nurse is with you.
Patient	Mr Leslie Ashdown, 78, retired bus driver — on a trolley, drowsy but able to talk. His daughter Helen is with him.
Triage note	“Three days of vomiting and diarrhoea after a family meal; not keeping fluids down; daughter says he has hardly passed urine since yesterday and is ‘not himself’. Bloods, gas and dipstick done at triage.”
Records	Hypertension; heart failure with preserved ejection fraction (echo two years ago); type 2 diabetes (HbA1c 52 mmol/mol); osteoarthritis of the right knee. No known allergies. Lives with his wife, who has dementia; Helen lives nearby.

Results sheet — Mr Leslie Ashdown, 78 · emergency department · today

Blood results, venous gas and urine dipstick from triage, with his last practice results for comparison, and his medicines.

Blood test (venous, 09:40 today)	Today	Three months ago (practice)	Reference range
Sodium	134 mmol/L	139	133–146
Potassium	6.7 mmol/L	4.6	3.5–5.3
Urea	24.8 mmol/L	7.1	2.5–7.8
Creatinine	318 micromol/L	98	59–104
eGFR (CKD-EPI)	15 mL/min/1.73 m²	64	60 or more
Bicarbonate	17 mmol/L	25	22–29
Glucose (random)	6.4 mmol/L	7.9	—
C-reactive protein	18 mg/L	3	less than 5
Haemoglobin	141 g/L	138	130–180
White cells	11.2 × 10⁹/L	6.8	4–11
Platelets	246 × 10⁹/L	251	150–400

Venous blood gas (09:45)	Result	Reference range
pH	7.29	7.32–7.43
pCO₂	5.1 kPa	5.3–7.3
Bicarbonate	17.8 mmol/L	22–29
Base excess	−8.2 mmol/L	−2 to +2
Lactate	1.6 mmol/L	0.5–2.0
Potassium	6.6 mmol/L	3.5–5.3
Glucose	6.3 mmol/L	—

Urine dipstick (09:50, small volume passed)	Result
Blood	negative
Protein	trace
Leucocytes	negative
Nitrite	negative
Glucose	negative
Ketones	+
Specific gravity	1.030

Medicines (from his repeat slip)	Dose	Last taken
Ramipril	10 mg once a day	this morning
Furosemide	40 mg once a day	this morning
Metformin	1 g twice a day	last night
Atorvastatin	20 mg at night	last night

Observations at triage (09:30): pulse 96 regular, BP 98/58 (his practice readings are usually 138–146 systolic), respiratory rate 18, SpO₂ 96% on air, temperature 37.4 °C, capillary refill 3 seconds, alert (drowsy but answers appropriately), NEWS2 3. Weight 82 kg. 12-lead ECG: requested at triage — not yet done.

Your task

•

Interpret the results sheet — it stays in front of you during the station. You may ask the nurse for any further bedside test or observation.

•

Take a brief, focused history from Mr Ashdown and his daughter.

•

Tell the nurse, aloud, the orders you want carried out now, as you would on a real shift.

•

Explain to Mr Ashdown and Helen what the results show and what will happen next.

Folded away

For the actor and the examiner

1 · Actor script — role player only

Candidates: do not open until you have consulted.

How to run this station

Three people if possible: the role player is Helen and also voices Leslie (slow, drowsy, a few words at a time); the examiner is the staff nurse, reads the ECG and findings when asked, ‘gives’ what the candidate prescribes by repeating it back, and marks. With two people the role player does both.
Treatments are ‘given’ when the candidate states drug, dose, strength or volume, route and duration aloud. If the order is incomplete the nurse asks “How much, and how fast, doctor?” — once — then does as told.

Persona and manner — Helen Ashdown

Helen, 49, a primary-school teacher. Practical, tired and frightened; you have been up most of the night with your dad and are also worried about your mum, who has dementia and is at home with a neighbour.
You speak for your dad when he is slow, but you let him answer when the doctor talks to him directly. You trust doctors but want straight answers.

Opening line — say this verbatim

“He’s just not himself, doctor. He’s been sick for three days and he’s hardly been to the toilet since yesterday. Is it his kidneys? The nurse looked worried when the bloods came back.”

Volunteer freely if given the space

It started on Sunday night after a family meal — your nephew had the same thing and was better in a day. Dad has been vomiting several times a day and had watery diarrhoea, no blood.
He has kept down sips of water and a little tea; no proper meal since Sunday.
He passed a small amount of dark urine this morning — “a few dribbles”. Nothing you noticed yesterday evening.

Only if asked

Tablets: he has carried on taking everything — ramipril and the water tablet this morning, metformin last night. Nobody has ever told him to stop anything when he is unwell.
Ibuprofen — only if asked whether he takes anything else, or any painkillers, or anything bought over the counter: “He’s been taking ibuprofen from the supermarket for his knee — about ten days now, three times a day. Last night was the last one.” If asked only “is this list complete?” say “I think so.”
No chest pain, no breathlessness, no palpitations. Ankles not swollen — “they’re less swollen than usual, actually”. No fever that you measured; he felt hot on Monday.
No tummy pain apart from cramps with the diarrhoea; no blood in the vomit or the stool. No recent antibiotics, no foreign travel.
Sleepier and slower than usual since yesterday evening — he knew who you were and the day, but you had to repeat things. No fall, no headache.
Alcohol: a pint at the weekend. Never smoked.
Waterworks — only if asked directly about his stream, getting up at night or trouble passing urine: “For a year or so he’s been slow to get going and up three times a night — the GP mentioned his prostate.” Otherwise keep it for the ‘anything to add’ moment.
As Leslie, if spoken to directly: you feel “washed out”, sick, and your mouth is dry. You have no pain. You are frightened about your wife being on her own.

Impact on daily life — home and work (only if asked)

Dad is your mum’s main carer — he does her tablets and the cooking. While he is in hospital you are covering with a neighbour and you will have to take time off school.
He still drives — mostly to the shops and to your mum’s appointments. The knee has stopped him walking the dog, which is why he started the ibuprofen.
Money is not a worry; being apart from your mum is. “He’ll want to go home tonight.”

Ideas, concerns and expectations

Idea: it is “just a bad stomach bug” that has knocked him off his feet — but the nurse’s face has frightened you.
Concerns: that his kidneys have failed and he will need dialysis; that he will have to stay in and your mum cannot manage.
Expectation: a drip and to go home in a day or two; you want someone to tell you plainly what the numbers mean.

Cues to deliver, timed

Minute 2, if the doctor is reading the sheet in silence: “What do the blood tests show? Is it bad?”
Minute 4, if the medicines have not been discussed: “Should he still be taking all his tablets? He had them this morning.”
Minute 6, if nothing has been explained to you yet: “Nobody’s told us anything. Is he going to need dialysis?”

If the doctor summarises and asks whether you want to add anything

If the waterworks have not come out: “One thing — he’s been slow passing water for a year or so, and up three times a night. The GP said it was probably his prostate. Does that matter?”
If it has: “What about his tablets when he goes home — does he stop them for good?”

How to respond to the doctor

If the doctor says that he is dried out, that the potassium in his blood is high and that treatment is starting now to protect his heart: you are frightened but steadier — “So it’s not permanent?”
If the doctor says the potassium can affect the heart and that is why the monitor and the injection are needed: you accept it. If the heart is mentioned with no explanation (“his potassium’s critical”): “Is he having a heart attack?”
If the doctor names which tablets are being stopped and gives a reason for each: “So the water tablet and the blood-pressure tablet made it worse?” — you take it in and ask about the ibuprofen if it has not been mentioned.
If the doctor says he will need the renal team or a monitored bed: you ask whether that means dialysis. If answered honestly — not now; only if the treatment does not work, and the kidney doctors would decide: reassured.
If the doctor uses numbers and abbreviations without explanation (“his eGFR is 15 and he’s got an AKI 3 with hyperkalaemia”): “I don’t know what any of that means, doctor.”
If the doctor says he can go home with tablets, or does not mention his heart or his tablets: “Is that it? Is he safe?”
If asked to step out while the doctor speaks to Dad alone: you go without fuss.

Do not

Volunteer the ibuprofen or the prostate symptoms unless asked as scripted, or invited to add anything (apart from the timed cues).
Use the words “kidney injury”, “potassium” or “dialysis” before the doctor has — except “dialysis” in the minute-6 cue.
As Leslie, do not answer questions about his medicines — defer to Helen: “Ask Helen, she sorts my tablets.”

Findings to give the candidate — only if asked for

The staff nurse (examiner) gives each of these only when the candidate asks for it, and carries out the candidate’s instructions by repeating them back (“Calcium gluconate ten per cent, thirty mils, over ten minutes — going up now”). Do not offer findings or treatments the candidate has not asked for, apart from the minute-5 monitor cue. (Where a separate examiner is present, the examiner reads them.)

12-lead ECG (if asked for — “done now”): sinus rhythm 94/min, PR 180 ms, QRS 96 ms, tall peaked T waves in V2–V5; no loss of P waves, no QRS widening. Examination (if asked): dry mouth and tongue, reduced skin turgor, jugular venous pressure not visible, no ankle oedema, chest clear, abdomen soft with mild generalised tenderness and no masses; bladder not palpable. Bladder scan (if asked): 40 mL. Capillary glucose (if asked): 6.2 mmol/L. Repeat observations after a 500 mL fluid bolus (announce “twenty minutes have passed” if the candidate asks for them): pulse 90, BP 108/64. If no calcium has been given by minute 5 with the ECG changes known: the nurse says “The monitor’s showing some broad complexes, doctor.”

2 · Examiner mark sheet — generic scheme plus the key facts for this case

Domain marks — with the key facts that earn a 4 at this station

Domain (GMC wording) · key facts for this case	1	2	3	4	Score
1 · Data gathering, technical and assessment skills Interprets against baseline: creatinine 318 from 98 (3.2 ×) — KDIGO stage 3; potassium 6.7 — severe; pH 7.29 — acidosis; lactate normal; bland dip — pre-renal Asks for the ECG at once — peaked T waves, QRS normal; asks for fluid-status examination (dry, JVP down, bladder empty), capillary glucose and a bladder scan Finds all four drugs — including over-the-counter ibuprofen* — taken through the illness; red flags: oliguria, drowsiness, hypotension, chest pain, prostate symptoms* ICE (fears kidney failure and dialysis; wants plain answers) and impact — he is his wife’s carer; driving; the knee	☐	☐	☐	☐	/4
2 · Clinical management skills Orders aloud: calcium gluconate 10% 30 mL over 10 min* (ECG changes); insulin 10 units in 25 g glucose, then 10% glucose 50 mL/h × 5 h; salbutamol nebulised; monitor* Stops ramipril, furosemide, ibuprofen, metformin; 500 mL bolus and reassess; catheter and fluid balance; potassium at 1, 2, 4, 6, 24 h; glucose checks; zirconium binder — credit if offered Summary and check, then the working diagnosis: pre-renal AKI on ACE inhibitor, diuretic and NSAID with severe hyperkalaemia — why not obstruction, intrinsic, sepsis; registrar now; renal or critical-care opinion Safety-net: while in hospital — chest pain, palpitations, faintness, worsening drowsiness or no urine → tell the nurse at once; on discharge, sick-day guidance in writing · Follow-up: repeat U&E and potassium today; renal review if no improvement; practice bloods within a week of discharge and tablets reviewed before any restart	☐	☐	☐	☐	/4
3 · Interpersonal skills Treats first, explains as he goes — Helen is told in one sentence why the monitor and the injection are needed Numbers turned into plain words: “dried out”, “kidneys strained”, “potassium too high for the heart” Talks to Leslie as well as Helen; honest about dialysis — not now, and who decides Sick-day guidance explained as something to take home, not a telling-off about the ibuprofen	☐	☐	☐	☐	/4
Station total					/12

Domain score (educational construct):

Score	Descriptor
1	Unsatisfactory (did not achieve safe FY2 standard)
2	Borderline (just achieving minimum safe FY2 standard)
3	Satisfactory (competent and safe FY2 standard)
4	Good (exceeds FY2 standard)

This 1–4 domain score and its descriptors are an Acumen educational construct: the GMC publishes the three marking domains and the four-mark maximum, but not the descriptors its examiners use, and it does not publish station mark sheets. See Legal & Regulatory.

Marks are 1 to 4 in each domain; the generic descriptor for each mark is on the mark scheme page, and the structure of the eight minutes is on the 8-minute station page. The full standard for this case is in section 3 and the GMC feedback statements, with examples from this case, are in section 4. The examination findings that the role player gives — only if the candidate asks for them — are at the end of section 1.

3 · Expanded station-specific marking standard — what earns 4, 3, 2 and 1 here

The top row is the full picture of what a competent FY2 could do at this station, including the working diagnosis with its justified differentials, the safety-net and the follow-up; lower rows describe how performance falls away. It is a debriefing aid, not a checklist to recite: nobody says every line in eight minutes, and a 4 is a judgement that the essentials — the italic key facts on the mark sheet — were done well, in plain language and at the patient’s pace. Acumen training standard — the GMC does not publish station mark sheets.

Mark	Domain 1 · Data gathering, technical and assessment skills	Domain 2 · Clinical management skills	Domain 3 · Interpersonal skills
4	Works through the sheet comparing with the baseline: creatinine 318 against 98 — more than three times baseline, so KDIGO stage 3 (NICE: a 50% rise within 7 days, or 26 micromol/L within 48 hours, defines AKI); eGFR 15 is a snapshot, not a stage; potassium 6.7 — severe hyperkalaemia (≥ 6.5), confirmed on the gas (6.6, so not spurious); acidosis; bland dipstick in keeping with a pre-renal cause. Credit if offered, not required for a 4: the urea pattern, lactate 1.6 excluding metformin-associated lactic acidosis, CRP and white cells Asks for the ECG straight away — peaked T waves, QRS and PR normal — and a cardiac monitor; asks for a fluid-status examination and capillary glucose. Credit if offered, not required for a 4: a bladder scan (40 mL) Drug chart: identifies all four culprits — ACE inhibitor, diuretic, NSAID and metformin — and establishes when each was last taken; finds the over-the-counter ibuprofen by asking beyond the repeat slip Focused history from Leslie and Helen: onset, vomiting and diarrhoea, oral intake, urine output (“dribbles” today), confusion, chest pain; red flags: oliguria, hypotension, drowsiness, palpitations; asks about urinary symptoms — poor stream and nocturia for a year, so obstruction is checked ICE: Helen fears kidney failure and dialysis and wants plain answers; Leslie fears for his wife. Impact on daily living: he is his wife’s carer, drives, and the knee pain started the ibuprofen	Treats the potassium before finishing the history, stating each order in full to the nurse: protect the heart — calcium gluconate 10% 30 mL IV over 10 minutes (ECG changes present), with cardiac monitoring throughout; shift potassium into cells — soluble insulin 10 units in 25 g glucose by IV infusion (UKKA protocol). Credit if offered, not required for a 4: the 10% glucose infusion at 50 mL/hour for 5 hours afterwards (pre-treatment glucose below 7); nebulised salbutamol 10–20 mg as an adjunct (not alone); step 3, sodium zirconium cyclosilicate (NICE TA1148, 2026; UKKA: 10 g three times a day for up to 72 hours), with no calcium resonium and no routine bicarbonate; the UKKA repeat-potassium and glucose times; a catheter with hourly urine output Fluids: 500 mL crystalloid bolus over 15 minutes and reassess (NICE CG174), then maintenance and replacement guided by examination and urine output — not “two bags fast” in a man with heart failure, and not fluid restriction because of the heart failure Stops and crosses off ramipril, furosemide, ibuprofen and metformin, and says why for each; writes the reason so the drugs are not restarted by default Summarises to Leslie and Helen and checks whether they want to add anything — which releases the prostate history if it has not come out Working diagnosis with justified differentials: stage 3 acute kidney injury, pre-renal, from three days of gastroenteritis while taking an ACE inhibitor, a loop diuretic and an NSAID, with severe hyperkalaemia and a metabolic acidosis. Obstruction is less likely (bladder scan 40 mL) but is excluded by ultrasound within 24 hours if he does not improve with fluids; intrinsic disease is unlikely with a bland dipstick; sepsis is unlikely (normal lactate, modest CRP). Metformin-associated lactic acidosis is excluded by the lactate Escalates: tells the ED or medical registrar now; asks for a renal or critical-care opinion because the potassium is 6.5 or above and the AKI is stage 3 (NICE: discuss stage 3 with nephrology within 24 hours; UKKA: renal or critical care opinion for severe hyperkalaemia); a monitored bed; renal replacement therapy is the specialist’s decision if hyperkalaemia or acidosis do not respond. Explains the plan, the safety-net and sick-day guidance to Leslie and Helen Safety-net: in hospital — chest pain, palpitations, feeling faint, becoming more drowsy or confused, or passing no urine → the nurse at once, and the monitor stays on until the potassium is below 6.0 and falling; once home — any further vomiting, diarrhoea or fever → stop the blood-pressure tablet, the water tablet and metformin again and ring the practice or NHS 111 the same day; never take ibuprofen or any other anti-inflammatory again without asking; breathless, swollen ankles or very little urine → same-day assessment; chest pain or collapse → 999. Follow-up: potassium rechecked at 1, 2, 4, 6 and 24 hours after treatment and glucose every 30–60 minutes for 6 hours; a medical or renal review the same day with creatinine daily until it is falling; a urological ultrasound within 24 hours if the creatinine does not improve with fluids (prostate symptoms); the FY2 tells the supervising registrar and writes the drugs stopped — and the reason — on the chart and in the discharge letter; the practice repeats U&E within a week of discharge, restarts ramipril only when he has recovered and the potassium is below 5.5, restarts furosemide only if fluid overload returns, and reviews metformin against the recovered eGFR; written sick-day guidance given to Leslie and Helen; his prostate symptoms and the knee pain (paracetamol, topical NSAID or physiotherapy — not oral ibuprofen) back to the GP.	Acts and explains at the same time: tells Helen in one sentence why the monitor is going on and what the injection is for, then carries on Speaks to Leslie directly — slowly, one question at a time — and does not talk over him Turns the sheet into pictures: “the bug dried you out, your kidneys have been strained, and a salt in your blood has gone high enough to upset your heart — we can correct that” Answers the dialysis question honestly: not needed now; kidneys usually recover from this; the kidney doctors decide if the treatment does not work No blame about the ibuprofen — explains why anti-inflammatories and the kidney tablets do not mix when someone is dehydrated, and that nobody had told them Acknowledges the family situation — his wife at home — and that Helen is exhausted; checks what they have understood
3	AKI staged against baseline, severe hyperkalaemia recognised and the ECG requested promptly, the drugs identified; one of the bladder scan, the over-the-counter ibuprofen, the gas interpretation or ICE and impact missing.	Calcium and insulin-glucose ordered correctly and promptly, culprit drugs stopped, fluids and monitoring arranged, diagnosis stated with the main differentials; one of the glucose infusion, the salbutamol, the bladder scan or the senior and renal referral missing.	Clear and kind; explanation a little technical, or Leslie addressed only through Helen.
2	Reads the potassium and creatinine but does not stage or compare with baseline; ECG requested only after prompting; metformin or ibuprofen not noticed; little history.	Hyperkalaemia treated but slowly, or with an incomplete order (no dose, no duration); drugs stopped without saying why; fluids given without reassessment; no plan for repeat potassium.	Competent but silent at first — the sheet is read for two minutes with no word to the family; the explanation comes late and in jargon.
1	Reads the numbers aloud with no interpretation or comparison with the baseline; ECG requested only after prompting; no drug history. Or unsafe: treats potassium 6.7 as a routine result: no ECG, no monitor, no escalation, and says it can wait for a repeat.	Calcium and fluids only; no insulin-glucose, no repeat-potassium plan, some culprit drugs left running; no senior involved. Or unsafe: no calcium despite ECG changes; or fluids alone with the potassium “to be repeated later”; or potassium treated with a diuretic or calcium resonium alone; or insulin with no glucose at all; or ramipril, furosemide and ibuprofen all continued; or discharges him.	Brusque or alarming (“his potassium is critical, he could arrest”); Helen’s questions brushed aside; no explanation to Leslie. Or unsafe: blames Helen or Leslie for the ibuprofen, or for carrying on the tablets; or promises he will be home tomorrow.

4 · GMC feedback statements — where underperformance was identified — with case-specific examples

A feedback statement marks where underperformance was identified in the consultation. With PLAB 2 results the GMC may attach any combination of the ten statements to a station — none, one or several. The right-hand column shows what each one looks like at this station. Record the statements that applied in the practice log.

GMC feedback statement	Underperformance it signals (generic)	Case-specific examples
1 · Consultation	Disorganised or unstructured consultation	Reads the whole sheet aloud for three minutes before speaking to anyone; history, treatment and explanation come in no order; no summary before the plan.
2 · Issues	Key issues or priorities not recognised	Treats the station as “a dehydrated man who needs fluids” and never recognises that the potassium is the emergency and the drugs are the cause.
3 · Time	Poor time management	Five minutes on the history of the family meal; the calcium is ordered as the bell goes; no explanation and no safety-net.
4 · Findings	Abnormal findings or results, or their implications, not identified	Does not compare the creatinine with the baseline on the sheet; calls eGFR 15 “chronic kidney disease”; is told peaked T waves and does not act; never asks about medicines bought over the counter, so the ibuprofen is missed.
5 · Examination	Physical examination or use of instruments not competent	Does not ask for the ECG or a monitor; does not examine fluid status or ask for a bladder scan; is told BP 98/58 and does not reassess after the bolus.
6 · Diagnosis	Working diagnosis or differential diagnoses not correct	“His kidneys aren’t working very well” — no stage, no cause; cannot say why obstruction, nephritis or sepsis are less likely; the prostate symptoms heard and ignored.
7 · Management	Management plan not reflecting current best practice	Fluids only; “calcium” with no dose or duration; insulin without glucose, or no glucose infusion afterwards; the ramipril, furosemide or ibuprofen left on the chart; no repeat potassium time; no senior or renal call; nothing said about what to do if he is sick again at home.
8 · Rapport	Rapport and sensitivity to the patient’s feelings and concerns not shown	Talks to the nurse and the sheet and never to Leslie; “his potassium’s critical” said across the bed with no explanation; tells Helen off about the ibuprofen.
9 · Listening	Verbal and non-verbal cues not used; poor active listening	Misses “the nurse looked worried” and “should he still be taking all his tablets?”; never invites them to add anything, so the prostate history stays hidden.
10 · Language	Language or explanations not understandable; understanding not checked	“He’s got an AKI 3 with a K of 6.7 and a met acidosis; we’ll give calcium, insulin-dex and salb nebs, and SZC if the renal reg agrees.”

5 · Examiner points of fact and guidelines

Points of fact the examiner should have to hand

Detecting and staging AKI (NICE NG148, last updated 16 October 2024, rec 1.3.1): a rise in creatinine of 26 micromol/L or more within 48 hours, or a 50% or greater rise known or presumed within 7 days, or urine output below 0.5 mL/kg/hour for more than 6 hours. KDIGO stages by the ratio to baseline: stage 1 = 1.5–1.9 × (or a rise of ≥ 26 micromol/L), stage 2 = 2.0–2.9 ×, stage 3 = 3 × or more, or creatinine ≥ 354 micromol/L, or renal replacement therapy started (urine output criteria run alongside). Here 318 ÷ 98 = 3.2 — stage 3. NG148 asks for a dipstick in everyone with suspected AKI (rec 1.4.2), an ultrasound within 24 hours when there is no identified cause or a risk of obstruction (1.4.6), and discussion with nephrology within 24 hours for stage 3 AKI (1.5.15).
Risk factors NICE lists (NG148 rec 1.1.1) include age 65 or over, diabetes, heart failure, hypovolaemia, and use within the past week of NSAIDs, ACE inhibitors, ARBs or diuretics “especially if hypovolaemic”. Rec 1.2.14: consider temporarily stopping ACE inhibitors and ARBs in people with diarrhoea, vomiting or sepsis until their condition has improved and stabilised. The UKKA hyperkalaemia guideline (rec 2.6) goes further: withhold RAAS inhibitors during acute intercurrent illness at all severities of hyperkalaemia; its rationale (citing RA/BSH 2019) advises re-introduction after recovery when the potassium is below 5.5.
Sick-day guidance (UK Kidney Association / Think Kidneys; PrescQIPP bulletin 260): when vomiting or diarrhoea (unless minor) or fever, sweats and shaking, temporarily stop ACE inhibitors, ARBs, diuretics, metformin, SGLT2 inhibitors and NSAIDs (prescribed or bought, but not low-dose aspirin), and restart 24–48 hours after eating and drinking normally; seek advice if unwell beyond 48 hours. It is advice for people judged at high risk after individual assessment, with the drugs named for each person — not a blanket rule. Metformin is withheld because it accumulates in AKI and dehydration raises the risk of lactic acidosis; a normal lactate here excludes that today.
Hyperkalaemia severity and ECG (UKKA Clinical Practice Guideline — Management of Hyperkalaemia in Adults, updated July 2026; its stated review date is October 2026, so re-check for a newer version before use): mild 5.5–5.9, moderate 6.0–6.4, severe ≥ 6.5 mmol/L. A 12-lead ECG for every hospitalised patient with potassium ≥ 6.0 (rec 14.1); continuous 3-lead monitoring for everyone ≥ 6.5, for ECG changes at any level, and for 6.0–6.4 if unwell (14.2). A blood-gas potassium is used while the laboratory result is awaited (15.2). In the community, ≥ 6.5 means urgent hospital assessment (4.1); 6.0–6.4 is repeated within a day (1.2.2), and acutely unwell people with mild or moderate hyperkalaemia, particularly with AKI, are assessed in hospital (4.2).
The UKKA five-step treatment (recs 16.1–17.2): (1) protect the heart — in the presence of ECG changes, UKKA suggests (grade 2C, rec 16.2a) 6.8 mmol of calcium as 30 mL 10% calcium gluconate IV over 10 minutes (calcium chloride 10 mL 10% over 5 minutes is reserved for cardiac arrest or peri-arrest); the July 2026 update downgraded the grade of evidence for calcium after the 2025 ILCOR review but kept the recommendation. (2) shift potassium into cells — 10 units soluble insulin in 25 g glucose by IV infusion for severe (and suggested for moderate) hyperkalaemia, with a 10% glucose infusion at 50 mL/hour for 5 hours afterwards if the pre-treatment glucose is below 7.0 mmol/L; nebulised salbutamol 10–20 mg as an adjunct, never as monotherapy; bicarbonate is not routine. (3) remove potassium — sodium zirconium cyclosilicate is recommended for severe and considered for moderate hyperkalaemia (patiromer is an option); calcium resonium has no role in the acute setting. (4) monitor — potassium at 1, 2, 4, 6 and 24 hours, and glucose at 0, 30, 60, 90, 120, 180, 240, 300 and 360 minutes. (5) prevent recurrence — review every drug that raises potassium against the renal function (rec 21.1). The exact infusion time for the insulin-glucose is taken from the trust protocol: check before teaching it as a fixed number.
Escalation (UKKA recs 19.1–19.6): severe hyperkalaemia → urgent renal or critical-care opinion guided by the clinical picture and its persistence after initial treatment; airway, breathing, circulation or conscious-level problems → critical care first; a stable patient with severe hyperkalaemia belongs on a monitored bed (acute medical unit, renal, coronary care or enhanced care); the decision on renal replacement therapy for life-threatening hyperkalaemia resistant to medical therapy is a nephrologist’s or intensivist’s. NICE NG148 rec 1.5.8: refer immediately for renal replacement therapy when hyperkalaemia, acidosis, uraemic complications or fluid overload are not responding to medical management — and base the decision on the whole patient, not an isolated value (1.5.9).
Sodium zirconium cyclosilicate — NICE TA1148 (29 April 2026, replacing TA599) recommends it in emergency care for acute life-threatening hyperkalaemia alongside standard care, and for persistent hyperkalaemia (K⁺ ≥ 5.5) in CKD 3b–5 or heart failure when a RAAS inhibitor cannot be optimised and the person is not on dialysis. UKKA (rec 16.6.1a–b) gives 10 g three times a day for up to 72 hours for severe hyperkalaemia, and says to consider it for moderate.
Fluids (NICE CG174, intravenous fluid therapy in adults): for hypovolaemia give a 500 mL crystalloid bolus over less than 15 minutes, reassess using ABCDE, and repeat as needed; in a patient with heart failure the bolus is given but the reassessment after each one is what keeps it safe. Replace the deficit and ongoing losses as well as maintenance, and reassess at least daily. Loop diuretics are not a treatment for AKI (NG148 rec 1.5.3).
Metformin (BNF; MHRA): contraindicated in AKI and when the eGFR is below 30; review when the eGFR is below 45. Stop it during AKI, dehydration and acute illness, and restart only when renal function has recovered and is stable. Ibuprofen and other NSAIDs are avoided in AKI, in CKD with an eGFR below 30, in heart failure, and alongside an ACE inhibitor and a diuretic (the ‘triple whammy’); for his knee NICE recommends paracetamol, topical NSAIDs and exercise or physiotherapy before oral NSAIDs.
Restarting after recovery: ramipril when he has recovered and the potassium is below 5.5 (RA/BSH 2019, quoted in the UKKA guideline; one RAAS drug at a time if there are several), with U&E one to two weeks after restarting (UKKA rec 2.3); furosemide only if fluid overload returns, at the lowest dose; metformin against the recovered eGFR. NG148 rec 1.5.16: monitor creatinine after AKI and consider nephrology referral if the eGFR settles at 30 or below; rec 1.6.4: discuss the risk of AKI from dehydrating illness and from over-the-counter NSAIDs with people at risk — the discharge conversation this station rewards.

Where candidates lose marks at this station

Reading eGFR 15 as “chronic kidney disease” instead of comparing creatinine with the baseline on the sheet.
Not asking for the ECG — or being told “peaked T waves” and carrying on with the history.
“Give some calcium” — no strength, volume or time.
Insulin without glucose, or no glucose infusion afterwards.
Fluids written up but ramipril, furosemide and ibuprofen left on the chart.
Never asking about the waterworks in a 78-year-old man with AKI.

Guidelines for this station

6 · MLA content map tags for this case

MLA content map	This station
Domain 1 · Areas of clinical practice	Renal and urology · Acute and emergency
Domain 3 · Clinical and professional capabilities	Investigations: request, interpret, act · Safe prescribing · Emergency and acute management plans · Communication with patients, relatives and carers · Using guidelines and evidence
Domain 5 · Patient presentations	Acute kidney injury · Electrolyte abnormalities · Dehydration · Diarrhoea
Domain 6 · Conditions	Acute kidney injury · Hyperkalaemia/ hypokalaemia · Infectious diarrhoea (including infective gastroenteritis)
Station family	Practical procedures and prescribing — Data interpretation and acute management

7 · My marks and reflection — practice log form

Record your three domain marks, your station total, the GMC feedback statements that applied (where underperformance was identified), and what you will keep and change. The form is already labelled with this case and its web address; a copy of your entry is emailed to you, so your practice log builds up in your inbox and can be downloaded.

Record my marks and reflection for P2-28

Revision link for this case: mdacumen.com/plab-2-osce/case-28-unwell-after-gastroenteritis-results

← P2-27 All practice cases P2-29 →

Independence & scope. Independent, formative training material from MD Acumen Ltd. Not affiliated with, endorsed by, or delivered on behalf of the General Medical Council. The GMC does not publish its station mark sheets: every mark scheme and descriptor on these pages is an Acumen training tool calibrated to the GMC's published marking domains, feedback statements and the MLA content map. Practice scores are not a prediction of examination performance. Clinical content reflects UK guidance at the date of editorial review — always check the current guideline. All patients are fictional. This course never provides, and will never ask you to share, real GMC exam content — full regulatory statement: Legal & Regulatory.

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Unwell after a stomach bug — interpreting the bloods

Read this as you would outside the room

Your task

For the actor and the examiner

How to run this station

Persona and manner — Helen Ashdown

Opening line — say this verbatim

Volunteer freely if given the space

Only if asked

Impact on daily life — home and work (only if asked)

Ideas, concerns and expectations

Cues to deliver, timed

If the doctor summarises and asks whether you want to add anything

How to respond to the doctor

Do not

Findings to give the candidate — only if asked for

Domain marks — with the key facts that earn a 4 at this station

Points of fact the examiner should have to hand

Where candidates lose marks at this station

Guidelines for this station

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