Ward cover

IV Fluids

Maintenance vs resuscitation — fluid type, rate & electrolytes

IV fluids are a drug — always know the indication. Maintenance replaces normal losses (~25–30ml/kg/day). Resuscitation restores circulating volume. The wrong fluid or rate causes as much harm as giving none.

What to do

1 · Establish indication

Maintenance / Resuscitation / Replacement — these require different fluids and rates. Never prescribe without knowing which you're giving.

2 · Assess clinically

Check HR, BP, CRT, mucous membranes, urine output. Is the patient actually volume-depleted? Don't give fluids by default.

3 · Choose fluid type

Resus: Hartmann's 500ml bolus.

Maintenance: Hartmann's or 0.9% NaCl + KCl at ~83ml/hr (70kg adult).

5% glucose for water replacement only — not resuscitation.

4 · Check U&E first

K+ <3.5: add 20mmol KCl/L.

K+ <3.0: add 40mmol KCl/L.

K+ >5.5: no potassium added.

5 · Reassess every 4–8 hours

Review: is it still needed? Can the patient drink? Any signs of fluid overload (oedema, bibasal crepitations)?

6 · Stop when no longer needed

Prescribe a stop date or clear reassessment trigger. Prolonged unnecessary IV fluids cause electrolyte derangement and fluid overload.

Drugs

Drug	Dose	Route	Notes
Hartmann's (balanced crystalloid)	250–500ml bolus	IV	Resuscitation. Reassess after each bolus. In suspected sepsis, up to 1000ml before senior review — the 30ml/kg figure is from US guidance, not UK.
Hartmann's + 20mmol KCl	1L over 8–12h	IV	Maintenance. Rate depends on weight. Check K+ before adding.
0.9% NaCl	1L over 8h	IV	Alternative maintenance. Risk of hyperchloraemic acidosis if prolonged.

Red flags

AKI worsening — stop/reduce IV fluids, reassess fluid balance
Bibasal crepitations or new breathlessness — fluid overload, slow rate or stop
K+ >5.5 on repeat U&E — stop potassium supplementation immediately
Cardiac failure or low albumin — very cautious with fluids (TACO risk)

Reference: NICE IV Fluids CG174 (2013) — Intravenous Fluid Therapy in Adults in Hospital