21.1 ICU Admission, Severity Scoring, Nutrition and Routine Prophylaxis
Key Takeaways
APACHE II scores acute physiology from the worst values in the first 24 hours of ICU admission, plus age and chronic health points, and is used to estimate group mortality rather than to make decisions about individual patients.
The SOFA score grades six organ systems (respiratory, coagulation, liver, cardiovascular, central nervous system and renal) from 0 to 4 each, and an acute increase of 2 or more points defines sepsis-related organ dysfunction.
Enteral nutrition is preferred over parenteral nutrition in critically ill patients who can be fed through the gut, and should usually start within 24-48 hours at a low rate, increasing gradually over the first week (ESPEN guidance).
Refeeding syndrome causes hypophosphataemia, hypokalaemia and hypomagnesaemia when feeding resumes after starvation; at-risk patients start at low calorie intake with thiamine and electrolyte monitoring and replacement.
Stress ulcer prophylaxis is indicated for patients with risk factors such as coagulopathy, shock or prolonged mechanical ventilation, and pharmacological venous thromboembolism prophylaxis with low molecular weight heparin is standard unless contraindicated.
21.1 ICU Admission, Severity Scoring, Nutrition and Routine Prophylaxis
Admission to Intensive Care
Intensive care is appropriate for patients who need, or are likely to need, organ support or monitoring that cannot be provided safely on a ward, and who are likely to benefit. Decisions consider:
- Reversibility of the acute illness.
- Chronic health and frailty (for example the Clinical Frailty Scale) and the patient's previously expressed wishes.
- The burden of intensive treatment relative to the likely benefit.
Levels of care (UK terminology) are used to describe needs: level 0-1 ward care, level 2 (high dependency: single organ support or step-down), level 3 (advanced respiratory support or support of two or more organ systems).
Early warning scores (for example NEWS2, which scores respiratory rate, oxygen saturation, supplemental oxygen, temperature, systolic blood pressure, heart rate and consciousness) help identify deterioration on the ward and trigger review by critical care outreach teams.
Severity of Illness Scores
Severity scores describe the case mix of a unit, compare observed and expected mortality (the standardised mortality ratio) and stratify patients in research. They are not designed to decide treatment for individuals.
| Score | Components | Timing | Main use |
|---|---|---|---|
| APACHE II | 12 physiological variables (worst values), Glasgow Coma Scale, age points, chronic health points | First 24 hours | Hospital mortality prediction for groups (0-71 points) |
| APACHE III and IV | More variables, diagnostic categories | First 24 hours | Refined prediction |
| SAPS II and SAPS 3 | Physiology, age, type of admission, chronic disease (SAPS 3 at admission) | First 24 hours or 1 hour (SAPS 3) | Mortality prediction, widely used in Europe |
| SOFA | Six organ systems scored 0-4 | Daily | Organ dysfunction trends; Sepsis-3 definition |
| ICNARC model | UK national risk model | First 24 hours | Benchmarking in UK units |
The SOFA Score
| System | Measure |
|---|---|
| Respiratory | with respiratory support |
| Coagulation | Platelet count |
| Liver | Bilirubin |
| Cardiovascular | Mean arterial pressure and vasopressor dose |
| Central nervous system | Glasgow Coma Scale |
| Renal | Creatinine or daily urine output |
An acute increase of at least 2 points in a patient with suspected infection defines sepsis (Sepsis-3) and is associated with about 10% hospital mortality.
Limitations
Scores depend on accurate data collection, can be affected by treatment before admission (lead-time bias), perform less well in populations different from those used to develop them, and drift over time as outcomes improve (recalibration is needed).
Nutrition in Critical Illness
Metabolic Response
Critical illness causes catabolism, insulin resistance and loss of muscle mass (up to about 1-2% per day in the first week). Early in critical illness, endogenous glucose production continues, so full feeding in the first days can lead to overfeeding.
Assessment
Risk can be assessed with tools such as the NUTRIC score or the Subjective Global Assessment; low body mass index, recent weight loss, reduced intake and prolonged ICU stay identify patients at high risk.
Enteral versus Parenteral Nutrition
- Enteral nutrition (EN) maintains gut integrity and is preferred when the gut can be used. ESPEN guidance recommends starting early EN within 24-48 hours in patients who cannot eat, at a low rate, increasing over 3-7 days.
- Parenteral nutrition (PN) is reserved for patients in whom EN is contraindicated or insufficient; ESPEN suggests considering supplemental PN after about 3-7 days when targets are not met. Trials such as CALORIES and NUTRIREA-2 showed that early PN was not superior to EN and that early full enteral feeding in shock increased gastrointestinal complications.
- Contraindications to EN: uncontrolled shock, uncontrolled hypoxaemia and acidosis, active upper gastrointestinal bleeding, bowel ischaemia or obstruction, high-output fistula, and abdominal compartment syndrome.
Targets
| Component | Typical target |
|---|---|
| Energy | Measured by indirect calorimetry when available; otherwise about 20-25 kcal/kg/day, reached gradually |
| Protein | About 1.3 g/kg/day, reached progressively (ESPEN) |
| Glucose | Keep blood glucose about 6-10 mmol/L; avoid both hyperglycaemia and tight control (NICE-SUGAR showed higher mortality with targets of 4.5-6.0 mmol/L) |
Practical Points
- Gastric residual volumes: feeding is usually continued unless the residual is above about 500 mL in 6 hours; prokinetics (metoclopramide, erythromycin) or post-pyloric feeding help intolerance.
- Aspiration prevention: head of the bed elevated 30-45°.
- Diarrhoea: consider antibiotics, Clostridioides difficile, hyperosmolar drugs and feed composition.
Refeeding Syndrome
When feeding restarts after starvation, insulin release drives phosphate, potassium and magnesium into cells and increases thiamine use, causing hypophosphataemia, hypokalaemia, hypomagnesaemia, fluid retention, arrhythmias, respiratory muscle weakness and Wernicke's encephalopathy.
- High-risk patients: BMI below 16 kg/m², unintentional weight loss above 15% in 3-6 months, little or no intake for more than 10 days, low electrolyte levels before feeding, or a history of alcohol misuse.
- Prevention: give thiamine before and during feeding, start at about 10 kcal/kg/day (5 kcal/kg/day in extreme cases), increase slowly, and monitor and replace phosphate, potassium and magnesium.
Routine Prophylaxis: The Daily Bundle
| Element | Approach |
|---|---|
| Venous thromboembolism | Low molecular weight heparin unless contraindicated; mechanical compression (intermittent pneumatic compression) if bleeding risk is high |
| Stress ulcer prophylaxis | Proton pump inhibitor or H2 antagonist in patients with risk factors (coagulopathy, shock, mechanical ventilation for more than about 48 hours, high-dose steroids); SUP-ICU (2018) found no mortality benefit, and REVISE (2024) found that pantoprazole reduced clinically important bleeding in ventilated patients without changing mortality |
| Ventilator-associated pneumonia | Head-up position, daily sedation interruption and spontaneous breathing trials, oral care, subglottic secretion drainage, avoidance of unnecessary re-intubation |
| Catheter-related infection | Aseptic insertion bundles, daily review and prompt removal of unnecessary lines |
| Glycaemic control | Target about 6-10 mmol/L |
| Sedation and delirium | Light sedation targets, regular delirium screening |
| Mobilisation and rehabilitation | Early mobilisation reduces ICU-acquired weakness |
| Pressure areas and eyes | Regular repositioning, eye care in sedated patients |
The mnemonic FAST HUGS BID (Feeding, Analgesia, Sedation, Thromboprophylaxis, Head-up, Ulcer prophylaxis, Glucose control, Spontaneous breathing trial, Bowel care, Indwelling catheter removal, De-escalation of antibiotics) is often used on ward rounds.
Outcomes After Critical Illness
Survivors may develop post-intensive care syndrome: physical weakness, cognitive impairment, anxiety, depression and post-traumatic stress disorder. ICU follow-up clinics, rehabilitation and patient diaries can help recovery.
Which statement about the APACHE II score is correct?
It is calculated daily throughout the ICU stay to guide treatment withdrawal in individual patients
It uses the best physiological values in the first 24 hours and excludes age
It combines the worst first-day physiology with age and chronic health points to predict group mortality
It scores six organ systems from 0 to 4 and is the basis of the Sepsis-3 definition
A patient with alcohol dependence and almost no oral intake for 2 weeks is started on enteral feeding in ICU. Which complication is most likely in the first days, and how should it be prevented?
Hyperphosphataemia; avoid phosphate supplements and give full calorie targets immediately to reverse catabolism
Hypernatraemia; give free water only and delay feeding for 1 week
Hyperkalaemia; give potassium-free feed and calcium resonium
Refeeding syndrome; give thiamine, start at about 10 kcal/kg/day and replace electrolytes
A ventilated patient in septic shock on increasing noradrenaline has a functioning gut. According to ESPEN guidance, what is the best nutritional plan?
Start full-target parenteral nutrition on day 1 because enteral feeding is unsafe in sepsis
Start low-rate enteral nutrition once shock is controlled, increasing gradually
Provide no nutrition for the first 14 days to reduce metabolic stress
Give full-target enteral feeding immediately regardless of vasopressor requirements, to limit muscle loss
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