ICU · Resuscitation & shock
Fluid Resuscitation — Crystalloid vs Colloid, Balanced vs Saline, SOSD/ROSE & Fluid Overload
Also known as Intravenous fluids · Crystalloid vs colloid · Balanced vs saline · SMART trial · SAFE trial · Lactated Ringer's · Hartmann's solution · Hyperchloraemic metabolic acidosis · Fluid compartments · ROSE model · SOSD · Permissive hypotension · Fluid overload · De-resuscitation · Strong ion difference
Fluid resuscitation turns on four evidence-based questions. (1) Crystalloid vs colloid — crystalloid is first-line; albumin shows no mortality benefit per SAFE (RR 0.99); hydroxyethyl starch is harmful per CHEST and 6S; CRISTAL showed no colloid advantage. (2) Balanced vs saline — balanced reduced the MAKE30 composite per SMART (14.3 vs 15.4 per cent; mortality and RRT individually non-significant); FLUID found no significant hospital-wide difference and BaSICS was neutral; SPLIT was the neutral precursor. Saline (chloride 154 mmol/L vs Plasma-Lyte 98) caused sustained hypercholaemia, a greater fall in strong ion difference, and reduced renal blood flow velocity and cortical perfusion in a volunteer crossover study. (3) How much — up to 30 mL/kg crystalloid initially with frequent reassessment (ESICM 2025), titrated to a mean arterial pressure of at least 65 mmHg (SEPSISPAM) and to fluid responsiveness (PLR, SVV/PPV, fluid challenge), not to a formula; roughly 56 per cent of patients are responders (Marik). (4) When to stop — the four-phase ROSE/SOSD fluid-stewardship model (Malbrain): fluid is actively given, then maintained, then actively removed (de-resuscitation). Restrictive strategies are safe (CLASSIC, FACTT, CLOVERS).
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Red flags
- Balanced crystalloid is first-line for the general ICU population (SMART, NEJM 2018) — saline's high chloride (154 mmol/L) causes hyperchloraemic metabolic acidosis → renal afferent vasoconstriction → AKI.
- Hydroxyethyl starch is HARMFUL — CHEST (AKI, RRT) and 6S (mortality in sepsis). It has been withdrawn or restricted. Do not use.
- Only about 50 per cent of ICU patients are fluid responsive — never give a fluid bolus blindly; test first (PLR, SVV/PPV, fluid challenge).
- Cumulative positive fluid balance is an independent predictor of mortality — restrictive strategies are safe (CLASSIC, FACTT, CLOVERS). Plan de-resuscitation.
- Permissive hypotension (no crystalloid until haemorrhage control) is appropriate in penetrating torso trauma (Bickell) but NOT in TBI — a low MAP worsens secondary brain injury.
- Lactated Ringer's is slightly hypotonic (Na 131) — caution in TBI (cerebral-oedema risk, controversial); saline is preferred where the intracranial pressure matters.
Meet the patient
A 66-year-old woman with urosepsis has received 3 L of 0.9 per cent saline in the emergency department. Her chloride is 114, pH 7.28, bicarbonate 17, MAP 59, lactate 3.6, with marked peripheral oedema. The registrar wants to give another litre of saline.[1]
Three things are wrong with the last three litres. The fluid is saline (high chloride, driving her acidosis), the volume was given without testing responsiveness, and the cumulative balance is already positive. The fix is not more saline — it is balanced crystalloid, a passive leg raise, and an early vasopressor.[1]
References27ShowHide
- [1]Semler MW, Self WH, Rice TW Balanced Crystalloids versus Saline in Critically Ill Adults N Engl J Med, 2018.PMID 29768150
- [2]Self WH, Evans M, Semler MW, et al. Clinical Effects of Balanced Crystalloids vs Saline in Adults With Diabetic Ketoacidosis: A Subgroup Analysis of Cluster Randomized Clinical Trials JAMA Netw Open, 2020.PMID 33196806
- [3]Finfer S, Bellomo R, Boyce N, French J, Myburgh J, Norton R; SAFE Study Investigators. A comparison of albumin and saline for fluid resuscitation in the intensive care unit N Engl J Med, 2004.PMID 15163774
- [4]Myburgh JA, Finfer S, Bellomo R, et al. Hydroxyethyl starch or saline for fluid resuscitation in intensive care N Engl J Med, 2012.PMID 23075127
- [5]Perner A, Haase N, Guttormsen AB, et al. Hydroxyethyl starch 130/0.42 versus Ringer's acetate in severe sepsis N Engl J Med, 2012.PMID 22738085
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- [12]Bickell WH, Wall MJ Jr, Pepe PE, et al. Immediate versus delayed fluid resuscitation for hypotensive patients with penetrating torso injuries N Engl J Med, 1994.PMID 7935634
- [13]Bulger EM, May S, Brasel KJ, et al. Out-of-hospital hypertonic resuscitation following severe traumatic brain injury: a randomized controlled trial JAMA, 2010.PMID 20924011
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