84 INTENSIVE CARE

# 85 INTENSIVE CARE

Intensive Care===

Critical care is the branch of medicine concerned with supporting failing organ systems while the underlying disease process is treated. For MRCS Part A, you are not expected to run an ICU — but you ARE expected to understand the levels of care, the principles of ventilation, the lines and monitors used, the major drugs, and the medico-legal framework around brain death and end-of-life decisions. Surgical patients populate ICU after major operations, sepsis, trauma and multi-organ failure, so this material is heavily tested.

Levels of care

The intercollegiate classification divides hospital care into four levels based on the intensity of monitoring and organ support delivered. Knowing the boundaries is a recurring SBA theme.

Level	Where	What it provides
Level 0	Normal ward	Patient's needs met by routine ward care
Level 1	Ward with input from critical care team	"At risk" patients; recently stepped down from HDU; needs increased observation
Level 2	HDU	Single organ support (e.g. non-invasive ventilation, vasoactive drugs, renal replacement) or detailed post-op observation
Level 3	ICU	Advanced respiratory support (invasive ventilation) OR support of ≥2 organ systems

👩‍⚕️ The defining feature of Level 3 is either invasive ventilation OR support of two or more organs. A patient on a ventilator alone is Level 3. A patient on noradrenaline alone is Level 2. Add the noradrenaline to the ventilator and the patient is still Level 3 — but now meets it on both criteria.

Indications for ICU admission

ICU admission is a clinical decision balancing the severity of physiological derangement against the chance of meaningful recovery. Classic indications:

➡ Respiratory failure needing intubation and invasive ventilation

➡ Haemodynamic instability requiring vasopressors or inotropes that cannot be safely run on the ward

➡ Neurological deterioration — GCS ≤ 8 mandates a definitive airway (intubation), because protective reflexes are lost

➡ Multi-organ failure — e.g. septic shock with acute kidney injury and ARDS

➡ Post-cardiac arrest care, including targeted temperature management

➡ Major surgery in high-risk patients (planned Level 2/3 admission)

👩‍⚕️ "GCS 8, intubate" is one of the most reliable exam aphorisms. Below 8, the patient cannot protect their airway from aspiration.

Ventilation

Invasive ventilation

Delivered through an endotracheal tube (short-term, oral or nasal) or a tracheostomy (long-term, > 7–14 days of expected ventilation, or for airway protection). Key modes:

- Volume-controlled (VC) — you set the tidal volume; airway pressure is the variable. Risk of barotrauma if compliance falls.

- Pressure-controlled (PC) — you set the peak airway pressure; tidal volume is the variable. Safer pressure profile, less reliable minute ventilation.

- SIMV (synchronised intermittent mandatory ventilation) — machine delivers a set number of mandatory breaths, synchronised with the patient's effort; patient can breathe spontaneously in between. Used for weaning.

- Pressure support (PS) — every breath is patient-triggered; the ventilator augments it with a set pressure. Almost a spontaneous mode, used in late weaning.

- CPAP — continuous positive airway pressure throughout the cycle; the patient does all the work of breathing. Often the final step before extubation.

PEEP

Positive end-expiratory pressure is the pressure remaining in the airway at the end of expiration. It splints alveoli open, prevents cyclical collapse and improves oxygenation by increasing the surface area available for gas exchange. The trade-off: high PEEP raises intrathoracic pressure, which reduces venous return and therefore cardiac output, and increases the risk of barotrauma.

Lung-protective ventilation

The ARDSnet trial established that ventilating injured lungs with low tidal volumes (6 ml/kg ideal body weight) and limiting plateau pressures to < 30 cmH₂O reduces mortality in ARDS. The principle now applies broadly to any ventilated patient — large tidal volumes cause volutrauma.

Non-invasive ventilation

Delivered through a tight-fitting mask, avoiding intubation. Two flavours:

	CPAP	BiPAP
Levels of pressure	Single (continuous)	Two (IPAP inspiratory, EPAP expiratory)
Mechanism	Recruits alveoli, ↑FRC, ↑oxygenation	Pressure support augments tidal volume → blows off CO₂
Classic indication	Cardiogenic pulmonary oedema	Type 2 respiratory failure (e.g. COPD exacerbation)

👩‍⚕️ Easy exam mark: pulmonary oedema → CPAP; COPD with CO₂ retention → BiPAP. CPAP fixes oxygenation; BiPAP fixes ventilation (CO₂).

ARDS

Acute respiratory distress syndrome is non-cardiogenic pulmonary oedema caused by diffuse alveolar damage. Triggered by sepsis, pancreatitis, trauma, aspiration, transfusion (TRALI) and burns.

Berlin definition — all four required:

1. Acute onset (within 1 week of insult)

2. Bilateral infiltrates on imaging

3. Not fully explained by cardiac failure or fluid overload

4. PaO₂/FiO₂ ratio impaired on PEEP ≥ 5 cmH₂O:

- Mild: 201–300

- Moderate: 101–200

- Severe: ≤ 100

Management: treat the underlying cause, lung-protective ventilation (6 ml/kg IBW), conservative fluid strategy, and prone positioning for ≥ 16 hours/day in moderate-to-severe ARDS — proning recruits dorsal lung and improves V/Q matching, with proven mortality benefit (PROSEVA trial).

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Sedation and analgesia

Ventilated patients need sedation to tolerate the tube and analgesia for procedural and disease pain. Common agents:

Sedation

- Propofol — workhorse infusion, often target-controlled. Rapid on/off, anti-emetic. Causes hypotension and, rarely, propofol infusion syndrome (metabolic acidosis, rhabdomyolysis, cardiac failure on high doses > 48 h).

- Midazolam — benzodiazepine infusion; useful in haemodynamic instability but accumulates, prolonging weaning.

- Dexmedetomidine — α2-agonist; produces "rousable" sedation with minimal respiratory depression. Good for delirium and weaning.

Analgesia

- Morphine and fentanyl infusions — fentanyl preferred in renal impairment (no active metabolites).

- Remifentanil — ultra-short-acting opioid metabolised by plasma esterases; offset is independent of organ function, ideal for neuro-ICU.

👩‍⚕️ Daily sedation hold ("wake and wean") reduces ventilator days and ICU stay. Pause the sedative each morning, assess neurology, then restart at the lowest effective dose.

Routine ICU prophylaxis

➡ VTE prophylaxis — LMWH unless contraindicated; mechanical (IPCs/TEDs) if bleeding risk

➡ Stress ulcer prophylaxis — PPI (or H2 blocker); risk highest in ventilated and coagulopathic patients

➡ Glycaemic control, head-up positioning, oral chlorhexidine and subglottic suction tubes form the VAP bundle to prevent ventilator-associated pneumonia

➡ Refeeding syndrome — when starved patients are fed, insulin drives K⁺, Mg²⁺ and PO₄³⁻ into cells; hypophosphataemia is the hallmark. Re-introduce nutrition slowly, replace electrolytes, give thiamine.

Invasive lines

Arterial line ("a-line")

A cannula in a peripheral artery transducing a continuous beat-to-beat blood pressure waveform and allowing repeated ABG sampling without re-puncture.

- Sites: radial (commonest; confirm collateral flow with Allen's test), femoral, brachial, dorsalis pedis

- Indications: vasopressor use, frequent ABGs, beat-to-beat haemodynamic monitoring

- Complications: thrombosis, infection, distal ischaemia, accidental drug injection

Central venous catheter (CVC)

Multi-lumen catheter sited in a large central vein. Allows infusion of vasopressors, irritant drugs (TPN, amiodarone), reliable IV access and central venous pressure monitoring.

- Sites, in order of preference for infection risk: internal jugular > subclavian > femoral

- Subclavian has the lowest infection rate but the highest pneumothorax risk; femoral has the highest infection and DVT rates but the lowest mechanical risk

- Complications:

- Mechanical: pneumothorax, arterial puncture, haemothorax, air embolism, arrhythmia from guidewire

- Infective: CLABSI (catheter-related bloodstream infection) — minimised by full barrier precautions, chlorhexidine prep and removal as soon as no longer needed

- Thrombotic: central vein thrombosis

👩‍⚕️ Ultrasound guidance is now standard of care for IJ insertion and significantly reduces complications. Subclavians are still often inserted by landmark.

Pulmonary artery catheter (Swan-Ganz)

Floated through the right heart to the pulmonary artery; measures cardiac output, pulmonary capillary wedge pressure and mixed venous oxygen saturation. Largely superseded by less invasive techniques (oesophageal Doppler, pulse contour analysis, echocardiography) — useful to recognise the name but rarely used in modern practice.

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Brain death (brainstem death) testing

In the UK brain death is a clinical diagnosis confirmed by two doctors (one a consultant, both registered ≥ 5 years, at least one not part of the transplant team), each performing two sets of tests.

Preconditions — all must be met BEFORE testing:

- Irreversible structural brain injury of known cause

- GCS 3 / deeply unconscious, ventilator-dependent

- No reversible confounders:

- Sedatives, opioids, neuromuscular blockers cleared

- Core temperature > 34 °C

- No severe electrolyte, metabolic or endocrine derangement

- Mean arterial pressure adequate

Brainstem reflex tests (all must be absent):

- Pupillary light reflex (CN II → III)

- Corneal reflex (CN V → VII)

- Oculo-vestibular (cold caloric: ice water in the ear → no eye deviation; CN VIII → III, VI)

- Oculocephalic ("doll's eyes")

- Gag reflex (CN IX, X)

- Cough reflex on bronchial stimulation

Apnoea test: patient pre-oxygenated, then disconnected from the ventilator. Brain death is confirmed if no respiratory effort occurs while PaCO₂ rises above 6.0 kPa (and ≥ 0.5 kPa above baseline) with pH < 7.40.

👩‍⚕️ Common SBA trap: a sedated, hypothermic or hyponatraemic patient cannot be brain death tested. Reverse the confounder first.

ECMO

Extracorporeal membrane oxygenation pumps blood through an external oxygenator, providing temporary cardiopulmonary support.

	VV ECMO	VA ECMO
Cannulation	Vein → vein	Vein → artery
Supports	Lungs only (gas exchange)	Heart and lungs (gas exchange + circulation)
Typical indication	Severe reversible respiratory failure (severe ARDS, H1N1)	Cardiogenic shock, post-cardiotomy failure, refractory cardiac arrest

ECMO is a bridge — to recovery, to transplant or to a decision. It does not treat the underlying disease.

End-of-life decisions in ICU

Not every ICU admission survives. A core ICU skill is recognising when ongoing treatment is no longer in the patient's interest and transitioning to comfort care.

- Withholding treatment = not starting a therapy (e.g. not escalating to CPR or RRT)

- Withdrawing treatment = stopping a therapy already in progress (e.g. extubating to comfort care)

- Ethically and legally, withholding and withdrawing are equivalent — both are appropriate when treatment is no longer in the patient's best interest. Many clinicians find withdrawing emotionally harder, but there is no ethical hierarchy.

Organ donation

- DBD (donation after brain death) — donor is brain dead but circulation is maintained until retrieval; organs are well perfused, allows multi-organ retrieval (heart, lungs, liver, kidneys, pancreas).

- DCD (donation after circulatory death) — donor does not meet brain death criteria; treatment is withdrawn and donation proceeds after asystole and a stand-off period. Warm ischaemia limits organs that can be used (mostly kidneys, liver).

In the UK, organ donation now operates on an opt-out (deemed consent) basis for adults.

Breaking bad news — SPIKES

A structured framework, frequently tested in non-technical-skills SBAs:

- Setting — private, quiet, sit down, no bleeps

- Perception — what does the family already understand?

- Invitation — how much do they want to know?

- Knowledge — give the information clearly, in small chunks, no jargon

- Emotions — acknowledge and respond with empathy

- Summary and strategy — agree the next steps


Test yourself

Which of the following are criteria of the qSOFA score?

• ((Respiratory rate less than 20::qSOFA threshold is RR ≥ 22, not less than 20.))
• ((Systolic BP less than 90::qSOFA threshold is SBP ≤ 100, not 90 (that's the shock cut-off).))
• ((Altered mental status::☑️ GCS < 15 scores 1 point on qSOFA; ≥ 2 points = high mortality risk.))
• ((Heart rate greater than 100::Tachycardia is a SIRS criterion, not part of qSOFA.))
• ((Temperature greater than 38::Fever is a SIRS criterion, not part of qSOFA.))

👩‍⚕️ qSOFA = RR ≥ 22, SBP ≤ 100, GCS < 15. One point each; ≥ 2 flags sepsis-related mortality risk.

A ventilated patient on noradrenaline alone is which level of care?

• ((Level 0::Level 0 = normal ward care, no organ support.))
• ((Level 1::Level 1 = ward patient with critical care team input, no active organ support.))
• ((Level 2::Single organ support only; this patient has both respiratory and cardiovascular support.))
• ((Level 3::☑️ Invasive ventilation OR ≥ 2 organs supported — both criteria are met here.))

👩‍⚕️ Invasive ventilation alone is enough for Level 3, regardless of vasopressors.

Which mode of non-invasive ventilation is most appropriate for a COPD exacerbation with type 2 respiratory failure?

• ((CPAP::Single-level pressure; recruits alveoli for oxygenation but does not augment tidal volume to blow off CO₂.))
• ((BiPAP::☑️ Two-level pressure support augments tidal volume → clears CO₂ in type 2 failure.))
• ((High-flow nasal oxygen::Improves oxygenation and washes out dead space but does not reliably reverse hypercapnia.))
• ((Venturi mask 28%::Controlled oxygen, but no ventilatory support for CO₂ retention.))

👩‍⚕️ CPAP for pulmonary oedema (oxygenation), BiPAP for COPD (ventilation).

What is the recommended tidal volume in lung-protective ventilation for ARDS?

• ((10 ml/kg actual body weight::Outdated; large tidal volumes cause volutrauma and increase mortality in ARDS.))
• ((8 ml/kg actual body weight::Still too high; weight should be ideal, not actual.))
• ((6 ml/kg ideal body weight::☑️ ARDSnet trial: 6 ml/kg IBW with plateau pressure < 30 cmH₂O reduces mortality.))
• ((4 ml/kg ideal body weight::Too low; insufficient minute ventilation.))

👩‍⚕️ Always ideal body weight — lungs scale with height, not waistline.

A patient has bilateral infiltrates, PaO₂/FiO₂ of 150 on PEEP 8, and pulmonary oedema not explained by heart failure. The severity of ARDS is:

• ((Not ARDS::All Berlin criteria are met.))
• ((Mild::Mild ARDS is P/F 201–300.))
• ((Moderate::☑️ P/F 101–200 = moderate ARDS.))
• ((Severe::Severe is P/F ≤ 100.))

👩‍⚕️ Berlin cut-offs: 300 / 200 / 100. Below 100 is severe — consider proning and ECMO referral.

Which central venous access site has the lowest infection rate?

• ((Femoral::Highest infection AND highest DVT rates.))
• ((Internal jugular::Intermediate infection risk; preferred for ultrasound-guided insertion.))
• ((Subclavian::☑️ Lowest infection rate, but highest pneumothorax risk.))
• ((Peripheral long line (PICC)::Higher infection rate than subclavian over prolonged use.))

👩‍⚕️ Subclavian — lowest CLABSI, highest pneumothorax. Femoral — opposite.

Which is NOT a precondition for brainstem death testing?

• ((Known irreversible structural cause::Required — must have a diagnosis.))
• ((Core temperature above 34 °C::Required — hypothermia abolishes brainstem reflexes reversibly.))
• ((Absence of sedative drugs::Required — sedation mimics brain death.))
• ((Absent EEG activity::☑️ EEG is not part of UK brainstem death testing — diagnosis is clinical.))
• ((Normal electrolytes::Required — severe derangement is a reversible confounder.))

👩‍⚕️ UK brain death is a CLINICAL diagnosis. EEG and angiography are used in some countries, not the UK.

Which cranial nerves are tested by the corneal reflex?

• ((II and III::Pupillary light reflex.))
• ((V and VII::☑️ Afferent CN V (ophthalmic division), efferent CN VII (orbicularis oculi).))
• ((VIII and III::Vestibulo-ocular reflex.))
• ((IX and X::Gag reflex.))

👩‍⚕️ Cornea = V in, VII out. A frequent neuroanatomy crossover question.

A 25-year-old with severe H1N1 pneumonia has refractory hypoxaemia despite maximal ventilation and proning. Which is the most appropriate next step?

• ((Add inhaled nitric oxide::Improves oxygenation transiently but no mortality benefit; not the definitive answer.))
• ((VA ECMO::VA supports heart + lungs; this patient has isolated respiratory failure.))
• ((VV ECMO::☑️ Provides oxygenation and CO₂ clearance for reversible respiratory failure — H1N1 is the textbook indication.))
• ((Tracheostomy::Does not address the failure of gas exchange.))

👩‍⚕️ VV = lungs only (vein-to-vein). VA = heart + lungs (vein-to-artery). H1N1 is the classic VV exam vignette.

A starved alcoholic patient is started on TPN. Forty-eight hours later he develops confusion, weakness and arrhythmia. The most likely electrolyte abnormality is:

• ((Hyperkalaemia::Refeeding drives K⁺ into cells — expect hypo, not hyper.))
• ((Hypernatraemia::Not characteristic of refeeding.))
• ((Hypophosphataemia::☑️ Hallmark of refeeding; insulin drives PO₄³⁻ intracellularly.))
• ((Hypercalcaemia::Not part of refeeding.))

👩‍⚕️ Refeeding triad: ↓PO₄, ↓K⁺, ↓Mg²⁺. Give thiamine, replace electrolytes, feed slowly.

Which statement about withdrawing and withholding life-sustaining treatment is correct?

• ((Withdrawing is ethically worse than withholding::Common misconception; they are equivalent.))
• ((Only withholding is legal in the UK::Both are legal where treatment is not in the patient's best interest.))
• ((Both are ethically and legally equivalent when treatment is no longer in the patient's best interest::☑️ Core medical ethics principle.))
• ((Withdrawal requires court approval in every case::Court input is only needed in disputed or specific cases (e.g. PVS historically).))

👩‍⚕️ The decision is about whether treatment benefits the patient — not about whether it has already started.

Revision summary

➡ Levels of care: 0 ward; 1 at-risk on ward; 2 HDU (1 organ); 3 ICU (≥ 2 organs OR ventilation)

➡ GCS ≤ 8 → intubate

➡ CPAP = pulmonary oedema (oxygenation); BiPAP = COPD / type 2 failure (ventilation)

➡ PEEP opens alveoli, ↑ oxygenation, ↓ venous return / cardiac output

➡ ARDSnet: 6 ml/kg IBW, plateau < 30 cmH₂O

➡ ARDS Berlin: bilateral infiltrates + P/F 300/200/100 (mild/moderate/severe), not cardiogenic; treat cause, lung-protective, prone ≥ 16 h if moderate–severe

➡ CVC sites: subclavian (↓ infection, ↑ pneumothorax); IJ (US-guided default); femoral (↑ infection + DVT)

➡ Brain death: 2 doctors, GCS 3, irreversible cause, no confounders (sedation, T < 34 °C, electrolytes); absent brainstem reflexes + apnoea test (PaCO₂ > 6 kPa)

➡ Corneal reflex = CN V in, CN VII out

➡ VV ECMO = lungs (H1N1); VA ECMO = heart + lungs

➡ Refeeding: ↓ PO₄³⁻ (hallmark), ↓ K⁺, ↓ Mg²⁺ — give thiamine, feed slowly

➡ Withdrawing = withholding ethically and legally

➡ DBD beats DCD for organ yield; UK is opt-out

➡ SPIKES: Setting, Perception, Invitation, Knowledge, Emotions, Summary