A 29-year-old woman at 32 weeks gestation presents to the obstetric assessment unit with headache and right upper quadrant pain. She has no significant past medical history. Blood pressure is 168/112 mmHg. Blood tests show: haemoglobin 102 g/L, platelets 88 × 10^9/L, ALT 245 U/L, AST 312 U/L, bilirubin 34 μmol/L, creatinine 145 μmol/L (booking creatinine was 68 μmol/L), LDH 680 U/L. Urinalysis shows protein 3+. Peripheral blood film shows schistocytes. What is the most appropriate immediate management?

Commence IV labetalol, IV magnesium sulphate, and arrange immediate delivery

Commence IV magnesium sulphate and plan delivery within 24-48 hours

Commence plasma exchange for thrombotic thrombocytopenic purpura

Commence high-dose corticosteroids for HELLP syndrome

Transfuse platelets and arrange delivery once platelets >100 × 10^9/L

A 38-year-old man with chronic kidney disease stage 5 (eGFR 10 mL/min/1.73m²) secondary to focal segmental glomerulosclerosis is being prepared for renal replacement therapy. He has preserved urine output of approximately 1500 mL per day. He works full-time as a teacher and wishes to minimize time spent on dialysis. Blood tests show: haemoglobin 108 g/L, potassium 5.1 mmol/L, phosphate 1.72 mmol/L, albumin 36 g/L. He has good manual dexterity and lives with his partner. Which renal replacement modality would be most appropriate to offer first?

Automated peritoneal dialysis (APD)

Continuous ambulatory peritoneal dialysis (CAPD)

In-centre haemodialysis three times weekly

Pre-emptive renal transplantation

A 48-year-old woman with no significant past medical history presents to the emergency department with a 6-hour history of severe right loin pain. CT KUB confirms a 5 mm stone at the right pelviureteric junction with mild hydronephrosis. She is afebrile. Blood tests show: white cells 9.2 × 10^9/L, CRP 8 mg/L, creatinine 78 μmol/L. Urinalysis shows blood 3+, leucocytes 1+, nitrites negative. She has been given adequate analgesia with diclofenac and morphine. What is the most appropriate next step in her management?

Discharge with analgesia, alpha-blocker, and follow-up in stone clinic

Admit for IV antibiotics due to obstructive pyelonephritis

Arrange urgent ureteroscopy and stone extraction within 48 hours

Insert percutaneous nephrostomy for decompression

Arrange extracorporeal shock wave lithotripsy (ESWL) within one week

A 52-year-old woman presents to the emergency department with confusion and agitation. Her husband reports she has had watery diarrhoea for 5 days. She has a history of bipolar disorder treated with lithium for 15 years. Blood tests show: sodium 128 mmol/L, potassium 3.2 mmol/L, creatinine 245 μmol/L (baseline 85 μmol/L), lithium level 2.8 mmol/L (therapeutic range 0.6-1.0). ECG shows sinus tachycardia at 105 bpm. What is the most appropriate immediate management?

Stop lithium, give IV 0.9% saline, and arrange urgent haemodialysis

Stop lithium, give IV 0.9% saline, and recheck lithium level in 12 hours

Continue lithium, correct dehydration, and arrange gastroenterology review

Stop lithium, give hypertonic saline for hyponatraemia, then arrange dialysis

Stop lithium, give IV fluids, and start haemofiltration

A 67-year-old man with chronic kidney disease stage 3a (eGFR 52 mL/min/1.73m²) secondary to diabetic nephropathy attends for annual review. He takes metformin, gliclazide, ramipril, atorvastatin, and aspirin. Blood tests show: HbA1c 64 mmol/mol, creatinine 128 μmol/L (stable from previous), potassium 5.4 mmol/L, bicarbonate 19 mmol/L. Urine albumin:creatinine ratio is 45 mg/mmol. Blood pressure is 138/82 mmHg. What is the most appropriate modification to his management?

Add SGLT2 inhibitor for renoprotection

Increase ramipril dose to maximize renoprotection

Stop ramipril due to hyperkalaemia and worsening renal function

Add sodium bicarbonate supplementation for metabolic acidosis

Add spironolactone for additional proteinuria reduction

A 34-year-old previously healthy woman presents with oliguria and peripheral oedema. Blood tests show: creatinine 320 μmol/L (baseline 72 μmol/L two weeks ago), urea 22.4 mmol/L, albumin 28 g/L. Urinalysis shows protein 4+, blood 2+, and no leucocytes or nitrites. Urine protein:creatinine ratio is 520 mg/mmol. Renal biopsy shows crescentic glomerulonephritis. Serology shows: ANCA negative, anti-GBM negative, ANA 1:640 (speckled pattern), anti-dsDNA positive, C3 0.42 g/L (normal 0.75-1.65), C4 0.08 g/L (normal 0.14-0.54). What is the most likely diagnosis?

Anti-GBM disease (Goodpasture syndrome)

Post-streptococcal glomerulonephritis

A 56-year-old woman with chronic kidney disease stage 4 (eGFR 20 mL/min/1.73m²) secondary to IgA nephropathy presents for routine review. She reports increasing fatigue. Blood tests show: haemoglobin 95 g/L, ferritin 280 μg/L, transferrin saturation 28%, PTH 18.5 pmol/L (normal 1.6-6.9), corrected calcium 2.12 mmol/L, phosphate 1.85 mmol/L, 25-hydroxyvitamin D 32 nmol/L. What is the most appropriate initial management of her secondary hyperparathyroidism?

Start colecalciferol 20,000 units weekly

Start alfacalcidol 250 nanograms daily

Start calcium carbonate 1.25 g three times daily with meals

A 28-year-old man presents to the emergency department with sudden onset severe left-sided loin pain radiating to the groin. He has vomited twice and appears distressed. He has a history of inflammatory bowel disease (Crohn's disease) and has undergone two small bowel resections. CT KUB shows a 7 mm calculus at the left vesicoureteric junction with moderate hydronephrosis. Blood tests show: creatinine 88 μmol/L, calcium 2.35 mmol/L, uric acid 380 μmol/L. What is the most likely stone composition in this patient?

Struvite (magnesium ammonium phosphate)

Electrolyte disturbances - Free UK Medical PG Review

Quick Overview

Electrolyte disturbances are life-threatening emergencies requiring immediate recognition and precise management. Critical thresholds define when intervention is urgent, and correction rates must be carefully controlled to prevent devastating complications like central pontine myelinolysis (CPM) or cardiac arrest. NICE NG148 emphasizes systematic assessment and monitoring protocols.

Core Facts & Concepts

Critical Thresholds for Immediate Action:

Electrolyte	Severe Low	Severe High	Life-Threatening
Sodium	<120 mmol/L	>155 mmol/L	<110 or >160 mmol/L
Potassium	<2.5 mmol/L	>6.5 mmol/L	>7.0 mmol/L
Calcium (corrected)	<1.9 mmol/L	>3.5 mmol/L	<1.6 or >3.7 mmol/L
Magnesium	<0.4 mmol/L	>2.0 mmol/L	<0.3 mmol/L

📊 Correction Rate Limits (CPM Prevention):

Hyponatraemia: Max 10 mmol/L in first 24h, 8 mmol/L per 24h thereafter
Chronic hyponatraemia (>48h): Max 4-6 mmol/L in first 24h
Hypernatraemia: Max 10 mmol/L per 24h (0.5 mmol/L/hour)

Figure 1: ECG showing tall tented T waves and widened QRS complex in hyperkalaemia

Calculated Osmolality Formula:

2(Na⁺) + glucose + urea = 275-295 mOsm/kg
Osmolar gap >10 suggests toxin (methanol, ethylene glycol)

Corrected Calcium Calculation:

Add 0.02 mmol/L for every 1 g/L albumin below 40 g/L

Problem-Solving Approach

Severe Hyperkalaemia (>6.5 mmol/L) Management:

Immediate ECG - Look for peaked T waves, wide QRS, sine wave pattern
Cardiac protection (if ECG changes present):
- 10 mL 10% calcium gluconate IV over 2-5 min (repeat if needed)
- Onset: 1-3 minutes, duration: 30-60 minutes
Shift K⁺ intracellularly (within 15-30 min):
- 10 units insulin + 25g glucose (50 mL 50% dextrose) IV
- Salbutamol 10-20 mg nebulized (adjunct, not monotherapy)
Remove K⁺ (hours):
- Calcium resonium 15g TDS PO/PR
- Consider dialysis if refractory or K⁺ >7.5 mmol/L

Figure 2: ECG showing flattened T waves and prominent U waves in hypokalaemia

Acute Symptomatic Hyponatraemia Protocol:

Assess acuity: <48h = acute; >48h = chronic
Severe symptoms (seizures, coma, GCS <8):
- 150 mL 3% hypertonic saline over 20 min
- Recheck Na⁺ after each bolus (max 3 boluses)
- Target: 5 mmol/L rise in first hour
Monitor hourly Na⁺ for first 6h, then 6-hourly
If overcorrection occurs: Give desmopressin + 5% dextrose to lower Na⁺

⚠️ Warning: Never correct chronic hyponatraemia rapidly - CPM risk peaks at >10 mmol/L rise in 24h

Analysis Framework

Hyponatraemia Classification by Volume Status:

Type	Volume Status	Urine Osmolality	Urine Na⁺	Common Causes
Hypovolaemic	Dehydrated, ↓BP	>100 mOsm/kg	<30: GI losses >30: renal losses	Diarrhoea, vomiting, diuretics, Addison's
Euvolaemic	Clinically normal	>100 mOsm/kg	>30 mmol/L	SIADH, hypothyroidism, pain, drugs
Hypervolaemic	Oedema, ascites	>100 mOsm/kg	<30 mmol/L	Heart failure, cirrhosis, nephrotic syndrome

Hyperkalaemia Causes - 5 R's:

📌 Remember: RENAL - Renal failure, Endocrine (Addison's), Nutritional (excess intake), ACEi/ARBs, Low aldosterone

Hypokalaemia Red Flags (🚩):

K⁺ <2.5 mmol/L - risk of arrhythmias, rhabdomyolysis
Concurrent digoxin therapy - toxicity risk significantly increased
U waves on ECG + muscle weakness = urgent replacement needed

Visual Aid

Hypocalcaemia vs Hypercalcaemia Features:

Feature	Hypocalcaemia	Hypercalcaemia
Neuromuscular	Tetany, Chvostek's/Trousseau's signs, seizures	Weakness, fatigue, confusion
Cardiac	Prolonged QT interval	Shortened QT interval
GI	Cramping	Constipation, nausea, pancreatitis
Renal	-	Polyuria, nephrolithiasis
Acute Rx	10 mL 10% calcium gluconate IV over 10 min	IV fluids 4-6L/24h + bisphosphonates

Key Points Summary

✓ Hyperkalaemia >6.5 mmol/L: Calcium gluconate first if ECG changes, then insulin/glucose, then salbutamol - dialysis if >7.5 mmol/L or refractory

✓ Hyponatraemia correction: Maximum 10 mmol/L per 24h (chronic cases: 4-6 mmol/L per 24h) to prevent central pontine myelinolysis

✓ Acute symptomatic hyponatraemia: 3% hypertonic saline 150 mL boluses, target 5 mmol/L rise in first hour only

✓ ECG changes identify severity: Hyperkalaemia shows tall tented T waves → wide QRS → sine wave; hypokalaemia shows U waves + flat T waves

✓ Corrected calcium essential: Add 0.02 mmol/L per 1 g/L albumin below 40 - treat if corrected Ca²⁺ <1.9 or >3.5 mmol/L

✓ Volume status determines hyponatraemia cause: Check urine Na⁺ and osmolality - SIADH has concentrated urine (>100 mOsm/kg) with Na⁺ >30 mmol/L

✓ Magnesium depletion prevents K⁺ correction: Always check and replace Mg²⁺ in refractory hypokalaemia - target >0.5 mmol/L