Fluid Therapy in Adults: MRCP Part 2 Notes

The NICE "5 Rs"

Prescribing intravenous fluids should follow a structured approach — the 5 Rs:

1. Resuscitation — restore circulating volume in shock
2. Routine maintenance — meet daily needs when a patient cannot drink
3. Replacement — correct existing deficits and ongoing abnormal losses
4. Redistribution — account for oedema, sepsis and organ dysfunction
5. Reassessment — review clinically and biochemically, at least daily

Resuscitation

• Identify shock (hypotension, tachycardia, poor perfusion, raised lactate)
• Give a 500 mL crystalloid bolus over <15 minutes, then reassess; repeat as needed
• After ~2000 mL without response, escalate for expert help
• Use a balanced crystalloid (e.g. Hartmann's/Plasma-Lyte) or 0.9% saline

Routine maintenance

For a patient who is euvolaemic but nil-by-mouth:

• Water: 25–30 mL/kg/day
• Sodium, potassium, chloride: ~1 mmol/kg/day each
• Glucose: 50–100 g/day (to limit starvation ketosis)

Choice of fluid

• Balanced crystalloids are increasingly preferred; large volumes of 0.9% saline can cause a hyperchloraemic metabolic acidosis
• Avoid excess sodium/chloride and fluid overload, especially in the elderly and in cardiac/renal disease

MRCP-specific traps

• Over-resuscitation with 0.9% saline causes a hyperchloraemic (normal anion gap) acidosis.
• Reassess after every bolus — do not prescribe a fixed large volume blindly.
• Maintenance potassium should not be added without a recent U&E in renal impairment (hyperkalaemia risk).

Summary

Prescribe IV fluids using the 5 Rs. Resuscitate with 500 mL crystalloid boluses over <15 minutes and reassess. Provide routine maintenance at ~25–30 mL/kg/day water with ~1 mmol/kg/day sodium, potassium and chloride. Prefer balanced crystalloids and avoid saline-induced hyperchloraemic acidosis.