Acute Internal Medicine Pearls: MRCP PACES Bedside Guide

Acute Internal Medicine (AIM) is one of the highest-yield yet underprepared domains in MRCP PACES. Whether you encounter a deteriorating patient in Station 4, a complex acute case in Station 5, or a brief clinical encounter in Stations 1 and 3, your ability to think like a medical registrar at the bedside is exactly what the examiners are assessing. This guide distils the clinical pearls, frameworks, and examiner expectations that separate confident candidates from borderline ones.

Why Acute Medicine Dominates PACES23

The PACES23 format places heavy emphasis on managing real-world acute presentations. Examiners want to see that you can:

• Recognise acutely ill patients rapidly

• Resuscitate using structured ABCDE approach

• Reason through differential diagnoses at registrar level

• Respond with appropriate escalation and senior decision-making

• Communicate clearly with patients, families, and colleagues

The new format integrates these skills more deeply — your clinical examination findings must seamlessly feed into your management plan, and your consultation skills must demonstrate urgency awareness without panic.

The Acute Medicine Framework: A Structured Approach

Every Acute Encounter Should Follow This Structure

Examiner Pearl: Candidates who demonstrate a systematic escalation plan — including thresholds for ITU referral — consistently score higher than those who just list treatments.

High-Yield Acute Scenarios for PACES

1. Sepsis and Septic Shock

The Scenario: A 68-year-old patient with pyelonephritis, community-acquired pneumonia, or biliary sepsis who is tachycardic, hypotensive, and confused.

What Examiners Want to Hear:

• Sepsis Six within one hour — know all six by heart:

  • Give oxygen to target SpO₂ 94–96% (88–92% in COPD)

  • Take blood cultures before antibiotics

  • Give IV antibiotics (know your local empiric guidelines)

  • Give IV fluid bolus (500ml crystalloid over <15 min, reassess)

  • Measure serum lactate

  • Measure hourly urine output

• Understand lactate significance:

  • Lactate > 2 mmol/L = sepsis

  • Lactate > 4 mmol/L or MAP < 65 mmHg = septic shock

• Vasopressor escalation: If MAP remains < 65 mmHg despite adequate fluid resuscitation (typically 30 ml/kg crystalloid), start noradrenaline as first-line vasopressor.

Common Mistake: Listing treatments without demonstrating assessment of response. Always say: "I would reassess after each intervention using clinical examination, urine output, lactate trend, and MAP."

2. Acute Kidney Injury (AKI)

The Scenario: A post-operative patient, a patient on NSAIDs + ACE inhibitors, or someone with sepsis developing oliguria and rising creatinine.

Key Clinical Pearls:

• Classify the AKI using KDIGO criteria:

• Pre-renal vs intrinsic vs post-renal — always assess for urinary obstruction (bladder scan, consider catheterisation, ultrasound if suspected)

• Dangerous hyperkalaemia protocol: Know the full sequence:

  1. Stabilise myocardium: IV calcium gluconate 10% (10 ml over 5–10 min)

  2. Shift potassium intracellularly: Insulin/dextrose (10 units Actrapid in 25g dextrose), salbutamol nebuliser

  3. Remove potassium: Calcium resonium, consider dialysis if refractory

• Medication review: Stop nephrotoxic drugs — NSAIDs, ACE inhibitors, metformin (lactic acidosis risk), diuretics if hypovolaemic

Examiner Pearl: "What would make you refer to nephrology / consider renal replacement therapy?" — Know the absolute indications (REFRACTORY acronym): Refractory hyperkalaemia, Euvolaemic fluid overload, Fractory acidosis, Refractory drug toxicity, A – uraemia (pericarditis, encephalopathy), Complication (CKD), Temperature (severe), Overdose, Refractory Y – YES to dialysis.

3. Acute Respiratory Failure

The Scenario: Type 1 respiratory failure (pneumonia, pulmonary oedema, PE) or Type 2 respiratory failure (COPD exacerbation, opiate overdose, neuromuscular weakness).

Critical Decision Point — NIV vs Intubation:

NIV Setup Pearls for PACES:

• Start IPAP 10, EPAP 4–5

• Titrate IPAP up by 2–5 cmH₂O every 10 minutes towards target (usually 15–20)

• Target: SpO₂ 88–92% in COPD, reduction in PaCO₂, improvement in pH

• Check ABG at 1 hour

Common Mistake: Forgetting to mention ceiling of care discussions before starting NIV. Always say: "I would establish a ceiling of treatment early, discussing with the patient, family, and critical care team if appropriate."

4. Acute Upper GI Bleed

The Scenario: Haematemesis or melaena in a patient with known cirrhosis or on NSAIDs/anticoagulants.

Risk Stratification — Know Your Scores:

• Glasgow-Blatchford Score (GBS): Used at presentation — determines need for endoscopy and transfusion. GBS of 0 = consider outpatient management.

• Rockall Score: Used post-endosscopy — predicts mortality.

Management Priorities:

1. Resuscitate: Two large-bore cannulae, crossmatch 4 units, fluid resuscitation

2. Transfusion strategy: Restrictive transfusion strategy (Hb threshold 70 g/L; 80 g/L in cardiovascular disease). Over-transfusion increases mortality in variceal bleeds.

3. Variceal bleeding specific protocol:

   • Terlipressin 2 mg IV QDS (vasoactive agent)

   • IV antibiotics (ceftriaxone — reduces mortality significantly)

   • Endoscopic band ligation within 12 hours

   • Sengstaken-Blakemore tube as bridge if uncontrolled

   • TIPSS if refractory

4. Non-variceal bleeding:

   • IV proton pump inhibitor (pantoprazole 80mg bolus then 8mg/h infusion for 72h)

   • Endoscopic therapy: adrenaline injection + thermal coagulation/clips

   • Tranexamic acid — consider (current evidence suggests no mortality benefit in routine use, but may be used in massive haemorrhage)

Examiner Pearl: Always mention anticoagulation reversal as part of your plan. For DOAC-related bleeding, know about specific reversal agents (idarucizumab for dabigatran, andexanet alfa for factor Xa inhibitors, PCC as alternative).

5. Deteriorating Patient: Metabolic Disturbances

Diabetic Ketoacidosis (DKA)

Key Management Principles (JBDS Guidelines):

• Fluid resuscitation first: 0.9% NaCl

  • 1 L over 1 hour

  • 1 L over 2 hours

  • 1 L over 2 hours

  • Then 1 L every 4–6 hours (add 10% glucose when blood glucose < 14 mmol/L)

• Fixed-rate insulin infusion (FRII): 0.1 units/kg/hour

  • If ketones not falling by ≥ 0.5 mmol/L/hour or glucose not falling by ≥ 3 mmol/L/hour → increase FRII by 1 unit/hour

• Potassium replacement critical:

  • K⁺ > 5.5: no replacement

  • K⁺ 3.5–5.5: 40 mmol/L in each bag

  • K⁺ < 3.5: senior review, may need cardiology monitoring

• Monitoring: Hourly glucose and ketone checks, 2-hourly electrolytes

• Complications to anticipate:

  • Cerebral oedema (especially in young — headache, vomiting, decreased GCS)

  • Hypokalaemia

  • Hypoglycaemia

  • ARDS

Hypercalcaemic Crisis

• Calcium > 3.4 mmol/L with symptoms: Medical emergency

• Initial management: Aggressive IV fluid resuscitation (3–4 L/24h 0.9% NaCl)

• Bisphosphonates: IV zoledronate 4mg (after rehydration; maximum effect at 2–5 days)

• Avoid: Thiazides, calcium supplements, Vitamin D analogues

Examiner Expectations: Senior-Level Thinking

What Separates a "Clear Pass" from "Borderline"

Communication in Acute Scenarios

The SBARD Framework for Escalation

When asked to escalate a deteriorating patient, use SBARD:

• Situation: "This is Dr [name], I'm calling about Mr [name] on Ward X, a 72-year-old admitted with CAP who has deteriorated in the last hour."

• Background: "He was admitted 24 hours ago with CURB-65 score of 3. His past medical history includes COPD and heart failure."

• Assessment: "His NEWS2 score has risen from 4 to 9. RR 28, SpO₂ 90% on 15L NRM, BP 86/50, HR 122, temp 38.6°C, GCS 14. His lactate is 3.2. I've started the Sepsis Six."

• Recommendation: "I think he needs ICU assessment for possible vasopressor support and possible ventilatory support. Can you review him urgently?"

• Decision: Document the plan and time of review.

Examiner Pearl: In Station 4 communication scenarios, demonstrating concise, structured, and professional escalation is worth more marks than elaborate clinical reasoning. Don't waffle — be specific and timely.

Common Acute Medicine Traps in PACES

1. The "Oxygen in COPD" Trap

Many candidates lose marks by automatically stating 28% oxygen or Venturi masks for COPD patients. The correct answer: Target SpO₂ 88–92% using whatever delivery system achieves that. In acutely ill patients, never deny oxygen — titrate to target.

2. The "Fluids in Heart Failure" Trap

In septic patients with heart failure, do not withhold fluids entirely. Give cautious boluses (250ml aliquots) with careful reassessment. Use bedside ultrasound if available.

3. The "Antibiotic Allergy" Trap

Always ask about the nature of penicillin allergy. A rash is not the same as anaphylaxis. In true anaphylaxis, avoid all beta-lactams and cephalosporins. In mild rash, cephalosporins are often safe (cross-reactivity is <1% with modern generations).

4. The "NIV Ceiling" Trap

Starting NIV without a clear escalation plan is dangerous and scores poorly. Always state: "I would use NIV as a trial. If physiological parameters don't improve within 1–2 hours, I would escalate to invasive ventilation if that aligns with the patient's ceiling of care."

5. The "End-of-Life" Trap

In deteriorating patients with advanced frailty or terminal illness, recognising when treatment is futile is a registrar-level skill. Be prepared to say: "I would review the patient's resuscitation status and frailty score, and if appropriate, have an honest discussion about ceilings of care and consider a palliative approach."

Time-Sensitive Pathways You Must Know Cold

Proactive Practice Tips for PACES Candidates

1. Practise Verbalising the ABCDE Approach

In the exam, you will need to verbalise your assessment clearly. Practise saying:

"Starting with airway — is the airway patent? Assessing breathing — respiratory rate is [X], oxygen saturation is [X] on [X] delivery, chest expansion is symmetrical, breath sounds…"

This should flow naturally without thinking. The more you verbalise it, the more confident you'll sound.

2. Develop Condition-Specific Escalation Templates

For every high-yield acute condition, pre-rehearse your escalation criteria:

• "In sepsis, I would escalate to ICU if MAP < 65 on two vasopressors, lactate rising despite resuscitation, or new organ failure developing."

• "In AKI, I would refer to nephrology if stage 3 with complications, or if requiring RRT."

• "In DKA, I would call for senior help if ketones not falling after 6 hours, GCS dropping, or potassium becoming difficult to manage."

3. Use the "Plan A, B, C" Framework

Examiners love candidates who plan for treatment failure:

"My first-line approach would be [X]. If this doesn't work, I would [Y]. And if the patient continues to deteriorate, my escalation would be [Z]."

This demonstrates anticipatory thinking and safe clinical practice.

4. Integrate Frailty and Holistic Assessment

For elderly patients, mention Clinical Frailty Score (CFS) and how it influences your management decisions. This shows examiner-level maturity:

"Given this patient's Clinical Frailty Score of 6, I would adopt a more cautious approach to fluid resuscitation and have an early discussion about ceilings of care."

Summary: Your PACES Acute Medicine Checklist

Before finishing any acute scenario in PACES, ensure you have covered:

• [ ] ABCDE systematic assessment

• [ ] Sepsis screening if any signs of infection/SIRS

• [ ] Focused investigations starting bedside

• [ ] Condition-specific management with drug names and doses

• [ ] Escalation thresholds clearly stated

• [ ] Medication review (stop nephrotoxins, adjust doses)

• [ ] Patient-centred considerations (frailty, preferences, ceiling of care)

• [ ] Monitoring plan with specific parameters and timelines

• [ ] Follow-up and handover arrangements

Final Thought

Acute Internal Medicine in PACES is not about knowing rare zebras — it's about demonstrating safe, systematic, and senior-level management of common emergencies. The examiners are looking for the doctor they would feel safe having on their night shift rota. Practise verbalising your management plans out loud, rehearse your escalation criteria, and always think: "What would I do if this were my patient at 3 AM?"

That level of practical, grounded clinical reasoning is exactly what earns a confident pass.

For ongoing PACES preparation, practise these frameworks with timed scenarios. Every acute case is an opportunity to demonstrate the structured, safe, and patient-centred care that defines a competent medical registrar.