Infusions, Dilutions and Fluids
Calculate volumes, final concentrations, infusion rates and treatment durations while checking high-risk fluid administration.
How to prepare for the PSA
Combine patient-centred prescribing judgement with fast BNF navigation, reliable calculations, complete prescriptions and explicit monitoring and communication.
Core concepts
Concept 1
Infusion calculations relate the total dose or volume to concentration and administration time.
Exam cue: Draw a simple chain from prescribed amount to prepared volume to rate over time.
Concept 2
Dilution problems require a clear distinction between the amount of active medicine, stock concentration and final volume.
Exam cue: Label stock volume and final volume separately in a dilution.
Concept 3
Infusion fluids are one of the five high-risk groups guaranteed coverage in every PSA and require an explicit safety and monitoring check.
Exam cue: Recalculate independently when an intravenous result appears extreme or the units are unfamiliar.
Risk pitfalls and guardrails
Using the stock concentration as though it were the final diluted concentration.
Guardrail: Do not let a familiar medicine, reference search or calculator output replace patient-specific safety checks and escalation.
Confusing a rate per minute with a rate per hour.
Guardrail: Do not let a familiar medicine, reference search or calculator output replace patient-specific safety checks and escalation.
Accepting a calculator output without checking the volume, duration and patient context.
Guardrail: Do not let a familiar medicine, reference search or calculator output replace patient-specific safety checks and escalation.
Memory anchors
Dose–Volume–Time
Link the prescribed dose to preparation volume and administration time.
Stock Versus Final
Keep the stock concentration separate from the final diluted concentration.
Rate Unit
State whether the administration rate is per minute, per hour or another interval.
Fluid Safety
Check fluid type, volume, additives, duration and monitoring together.
Independent Check
Recheck high-risk intravenous calculations before administration.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
A 500-mL infusion must run over 4 hours. What rate is required?
A 1,000-mL bag must run over 8 hours. What rate is required?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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