ICU · Resuscitation

Fluid therapy and resuscitation fluids in ICU

Also known as Crystalloid vs colloid · Balanced vs saline · SMART trial · SALT-ED trial · SPLIT trial · SAFE trial · Hyperchloraemic metabolic acidosis · Stewart strong ion difference · Albumin indications · Hydroxyethyl starch · CHEST trial · 6S trial · Damage control resuscitation · ROSE fluid model · Fluid overload · De-resuscitation · CLASSIC trial · CLOVERS trial

Fluid therapy is the commonest ICU intervention and one of the few that is genuinely a drug — with a pharmacokinetic volume of distribution, a narrow therapeutic window, and a measurable toxicity profile. Two questions dominate: WHICH fluid and HOW MUCH. WHICH: balanced crystalloids (Hartmann, Plasma-Lyte 148, Ringer acetate) are preferred first-line — the SMART (NEJM 2018) and SALT-ED (NEJM 2018) trials showed fewer major adverse kidney events with balanced solutions than 0.9% saline, and SSC 2021 suggests balanced over saline in sepsis; saline causes hyperchloraemic metabolic acidosis via a fall in the strong ion difference (Stewart), reduces renal cortical perfusion, and is reserved for hypochloraemia, hyponatraemia, TBI and drug compatibilities. Colloids: albumin is equivalent to saline (SAFE, NEJM 2004) and is suggested by SSC 2021 after large crystalloid volumes in sepsis; hydroxyethyl starch (HES) is harmful — more RRT (CHEST) and more death in sepsis (6S) — and is now restricted. HOW MUCH: fluid responsiveness is assessed dynamically (passive leg raise, PPV/SVV, IVC variability, end-expiratory occlusion) — only about half of ICU patients respond to a bolus. The four-phase ROSE model (Rescue, Optimisation, Stabilisation, Evacuation) frames therapy; cumulative positive fluid balance is an independent predictor of death. The CLASSIC (NEJM 2022), CLOVERS (NEJM 2023) and FACTT (NEJM 2006) trials support a restrictive strategy once shock resolves. Damage control resuscitation in trauma uses permissive hypotension, haemostatic (1:1:1) transfusion and early haemorrhage control.

high34 referencesUpdated 26 July 202620 min readSource-verified · Sept 2026

Checked against its sources on 2 Sept 2026

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Do NOT use hydroxyethyl starch (HES) — CHEST and 6S trials (NEJM 2012): more renal replacement therapy, and in severe sepsis higher mortality; restricted by medicines regulators for critically ill patients
Balanced crystalloids preferred over 0.9% saline — SMART (ICU) and SALT-ED (ward) trials: fewer major adverse kidney events; SSC 2021 suggests balanced crystalloids for sepsis resuscitation
Fluid overload is independently associated with AKI, ARDS, prolonged ventilation and mortality — monitor cumulative fluid balance daily and de-resuscitate
Normal saline (0.9% NaCl) causes hyperchloraemic metabolic acidosis (reduced strong ion difference), renal afferent vasoconstriction, coagulopathy — reserve for hypochloraemia, hyponatraemia, head injury and specific drug compatibilities
Only ~50% of ICU patients are fluid responsive — never give a fluid bolus blindly; use a dynamic test (passive leg raise, PPV/SPV, EEOT, IVC variability) first
Albumin is NOT superior to saline for resuscitation (SAFE trial); avoid in traumatic brain injury (subgroup harm). Use selectively for severe sepsis, large-volume paracentesis, hepatorenal syndrome prophylaxis

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Practise this topic8 MCQs with explanations

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CICMFFICMEDIC

Red flags

Do NOT use hydroxyethyl starch (HES) — CHEST and 6S trials (NEJM 2012): more renal replacement therapy, and in severe sepsis higher mortality; restricted by medicines regulators for critically ill patients
Balanced crystalloids preferred over 0.9% saline — SMART (ICU) and SALT-ED (ward) trials: fewer major adverse kidney events; SSC 2021 suggests balanced crystalloids for sepsis resuscitation
Fluid overload is independently associated with AKI, ARDS, prolonged ventilation and mortality — monitor cumulative fluid balance daily and de-resuscitate
Normal saline (0.9% NaCl) causes hyperchloraemic metabolic acidosis (reduced strong ion difference), renal afferent vasoconstriction, coagulopathy — reserve for hypochloraemia, hyponatraemia, head injury and specific drug compatibilities
Only ~50% of ICU patients are fluid responsive — never give a fluid bolus blindly; use a dynamic test (passive leg raise, PPV/SPV, EEOT, IVC variability) first
Albumin is NOT superior to saline for resuscitation (SAFE trial); avoid in traumatic brain injury (subgroup harm). Use selectively for severe sepsis, large-volume paracentesis, hepatorenal syndrome prophylaxis

In one line

Fluid therapy: balanced crystalloids preferred (Hartmann, Plasma-Lyte 148 — SMART/SALT-ED: fewer major adverse kidney events vs saline). 0.9% saline causes hyperchloraemic metabolic acidosis (reduced strong ion difference, reduced renal cortical perfusion) — reserve for hypochloraemia, hyponatraemia, TBI and specific drug compatibilities. Hydroxyethyl starch (HES): do NOT use (CHEST, 6S: more renal-replacement therapy, and in sepsis more death). Albumin = saline for resuscitation (SAFE); use selectively after large crystalloid volumes in sepsis (SSC 2021), after large-volume paracentesis, in spontaneous bacterial peritonitis; AVOID in TBI (SAFE-TBI). Assess responsiveness dynamically (passive leg raise, PPV/SVV, EEOT, IVC variability) — only about half of patients respond to a bolus. Four-phase ROSE model (Rescue → Optimisation → Stabilisation → Evacuation): boluses early, zero balance once shock resolves, de-resuscitate late. Fluid overload is the commonest iatrogenic harm in intensive care.

^[1] ^[13] ^[15] ^[21]

Meet the patient

A 72-year-old woman arrives in septic shock from urosepsis. She has received 30 mL/kg of 0.9% saline in the ED — 1.8 L. She remains hypotensive (MAP 59), lactate 3.8, warm peripheries. Her chloride is 112, pH 7.28, base excess minus 6. The registrar wants to give another litre of saline.^[14]

Two questions frame every fluid decision in the ICU: which fluid? (balanced crystalloid first-line; saline causes hyperchloraemic acidosis and AKI) and how much? (only about half of ICU patients are fluid responsive — test before every bolus). Get those two right and you avoid the commonest iatrogenic harm in intensive care.^[14]^[15]

References34Show

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