Perioperative Fluids & Transfusion

📘 1 · Miller's Anesthesia — Fluid Management

Fluid Physiology & the Three Questions

"Fluid is a drug, with a dose, a therapeutic window and toxicity. Too little leaves the patient hypovolaemic and hypoperfused; too much causes tissue oedema, impaired wound and anastomotic healing, ileus and respiratory failure. The evidence has moved away from both the old 'liberal' regimens and extreme restriction, toward a zero-balance, individualised approach guided by the patient's actual physiology."

Synthesised from Miller's Anesthesia, 9th Ed — Perioperative Fluid & Electrolyte Therapy.

💧 Ask three questions about every fluid

Maintenance — replacing normal ongoing losses in a fasting patient (water, Na⁺, K⁺, glucose). The "4-2-1 rule" gives an hourly rate (4 mL/kg for first 10 kg + 2 for next 10 + 1 for each kg thereafter).
Replacement — correcting existing deficits (fasting, vomiting, bleeding, third-space/evaporative surgical losses).
Resuscitation — restoring circulating volume in shock: small, repeated boluses guided by response, not a fixed large volume.

⚖️ The distribution rule

Isotonic crystalloid distributes across the whole extracellular space, so only ~⅓ (or less) stays intravascular — you need roughly 3–4 mL of crystalloid per 1 mL of blood loss if using crystalloid alone. 5% dextrose distributes across total body water and is useless for resuscitation. Match the fluid to the compartment you are trying to fill.

📗 2 · Barash / Morgan-Mikhail — Choosing the Fluid

Crystalloids vs Colloids & "Balanced" Solutions

"For most surgical patients a balanced crystalloid is the resuscitation fluid of choice. Large volumes of 0.9% saline produce a hyperchloraemic metabolic acidosis and are associated with more renal dysfunction than balanced solutions. Synthetic colloids — the hydroxyethyl starches in particular — have fallen out of favour after trials linked them to renal injury and increased mortality in the critically ill; albumin retains a limited role."

Synthesised from Barash — Clinical Anesthesia; Morgan & Mikhail's Clinical Anesthesiology.

Fluid	Type	Key features	Caveats
Balanced crystalloid (Ringer's lactate / Plasma-Lyte / Hartmann's)	Crystalloid	Physiological Cl⁻, buffer (lactate/acetate) — first choice for resuscitation & replacement	Lactate/K⁺ content — caution in severe hyperkalaemia; avoid Hartmann's in the same line as blood (calcium)
0.9% saline	Crystalloid	Cl⁻ 154 — useful in hypochloraemic alkalosis, TBI (Na⁺), hyponatraemia	Hyperchloraemic metabolic acidosis & AKI in large volumes
5% dextrose	Crystalloid (free water)	Provides water & some glucose	Distributes to total body water — not a resuscitation fluid
Human albumin (4–5% / 20%)	Colloid	Role in some settings (e.g. large-volume paracentesis, selected sepsis)	Cost; avoid as routine; harmful in traumatic brain injury (SAFE)
Hydroxyethyl starch (HES)	Synthetic colloid	Volume expansion	Avoid in critically ill/sepsis — AKI & mortality (6S, CHEST); restricted by regulators

🧪 The crystalloid-vs-colloid verdict

Colloids do not improve survival over crystalloids and cost more (SAFE trial: albumin ≈ saline overall, and worse in TBI). Balanced crystalloids are the default; reserve albumin for specific indications; avoid starches. In major surgery the aim is euvolaemia (zero fluid balance), not supranormal loading.

📙 3 · Blood Components & Transfusion Triggers

Component Therapy & When to Transfuse

🩸 The components

Packed red cells — raise oxygen-carrying capacity; ~1 unit raises Hb by ~10 g/L in an adult.
Fresh frozen plasma (FFP) — clotting factors; ~12–15 mL/kg for coagulopathic bleeding.
Platelets — for thrombocytopenia/dysfunction with bleeding; keep >50 ×10⁹/L for surgery, >100 for neuro/eye/major.
Cryoprecipitate / fibrinogen concentrate — for hypofibrinogenaemia (keep fibrinogen >1.5–2 g/L in obstetric/major haemorrhage).

Restrictive transfusion triggers NICE / TRICC / PBM

A restrictive strategy is at least as safe as a liberal one for most patients:
• Transfuse at Hb <70 g/L, target 70–90 g/L, for most patients.
• Hb <80 g/L threshold for symptomatic patients / acute coronary syndrome / chronic cardiovascular disease.
• Transfuse a single unit and reassess (don't transfuse by a "two-unit" reflex).
Treat the cause of anaemia, and remember the trigger is a guide, not a substitute for assessing bleeding, symptoms and physiology.

🇮🇳 Indian Context

Balanced crystalloids (Ringer's lactate) are the ubiquitous, economical default for perioperative fluid therapy. Pre-operative iron-deficiency anaemia is very common — optimise with iron (oral/IV) in the PAC clinic rather than transfusing on the table (a core Patient Blood Management principle). Blood-component availability varies by centre, so plan cross-match/group-and-save early, activate the local massive transfusion protocol promptly in haemorrhage, and use tranexamic acid (cheap, effective) early in trauma and obstetric bleeding.

📋 4 · Guidelines — Goal-Directed Therapy & PBM

How Much, and Guided by What

Goal-directed fluid therapy (GDT)

In major surgery, titrate fluid (± inotrope) to dynamic measures of fluid responsiveness — stroke-volume optimisation by oesophageal Doppler or arterial-waveform analysis, or pulse-pressure/stroke-volume variation — rather than to fixed formulae or static CVP. The goal is to give fluid only while it increases stroke volume, avoiding both hypovolaemia and overload. See the critical-care haemodynamic monitoring page for the physiology.

Patient Blood Management — the three pillars

1. Optimise red-cell mass — detect & treat anaemia and iron deficiency before elective surgery.
2. Minimise blood loss — surgical haemostasis, tranexamic acid, cell salvage, point-of-care coagulation testing (TEG/ROTEM), maintain normothermia & normal calcium/pH.
3. Optimise tolerance of anaemia — restrictive triggers, single-unit transfusions, physiological support. The best transfusion is often the one you prevent.

Tranexamic acid CRASH-2 / WOMAN

Give early (within 3 h) in traumatic haemorrhage (CRASH-2) and postpartum haemorrhage (WOMAN) — it reduces death from bleeding and is cheap and widely available. Typical dose 1 g IV over 10 min, then 1 g over 8 h (trauma), or 1 g IV in PPH (repeat once if needed).

🚨 5 · Massive Transfusion & Transfusion Reactions

Major Haemorrhage & Its Hazards

🩹 Massive transfusion protocol (MTP)

Definition: ~10 units RBC in 24 h, or replacement of one blood volume, or major ongoing haemorrhage.
Empirical ratio ~1:1:1 (RBC : FFP : platelets) until laboratory/viscoelastic results guide targeted therapy; give tranexamic acid early.
Maintain the "lethal triad" defences: prevent hypothermia (warm fluids/patient), acidosis, and coagulopathy; give calcium (citrate in stored blood chelates it → ionised hypocalcaemia).
Targets: fibrinogen >1.5–2 g/L, platelets >50 (>100 if CNS injury), normal ionised calcium, temperature >36 °C.

⚠️ Transfusion reactions — recognise fast

Acute haemolytic (ABO incompatibility) — fever, loin/chest pain, hypotension, haemoglobinuria, DIC; stop immediately, resuscitate, check the unit/identity. Usually a clerical/identification error.
Febrile non-haemolytic — common, benign; slow/stop, antipyretic, exclude haemolysis.
Allergic / anaphylaxis — urticaria → airway/circulatory collapse (esp. IgA deficiency); stop, treat as anaphylaxis.
TACO (circulatory overload) — hypertension, raised JVP, pulmonary oedema → diuretics, slow rate. TRALI — non-cardiogenic pulmonary oedema within 6 h, normal filling pressures → supportive/ventilatory care.
Delayed: delayed haemolysis, infection, iron overload, TA-GvHD (irradiated components for at-risk patients).

🗺 6 · Perioperative Fluid Plan

A Practical Flowchart

Assess the starting point

Fasting deficit, ongoing losses, comorbidity (cardiac/renal), expected blood loss
Optimise anaemia pre-operatively; group & save / cross-match appropriately

Maintenance & replacement

Balanced crystalloid for maintenance (4-2-1) and to replace evaporative/third-space losses
Avoid large-volume 0.9% saline; 5% dextrose is not for volume

Resuscitate to physiology

Small boluses guided by fluid responsiveness (SVV/PPV, stroke-volume optimisation), not fixed volumes
Aim for euvolaemia / zero balance in major surgery

Bleeding → components + TXA

Restrictive RBC trigger (Hb <70, or <80 if cardiac/symptomatic); single-unit & reassess
Major haemorrhage → activate MTP (~1:1:1), give TXA early, correct Ca²⁺/temperature/pH

Reassess & de-escalate

Guide ongoing therapy with lab/viscoelastic tests; stop fluids once perfused
Watch for overload (TACO), electrolyte & acid–base disturbance

⚠️ 7 · Common Mistakes

Common Mistakes in Fluids & Transfusion

❌ Mistake 1 — Large-volume 0.9% saline

It causes hyperchloraemic metabolic acidosis and more renal dysfunction than balanced solutions. Use a balanced crystalloid (Ringer's/Plasma-Lyte) as the default for resuscitation and replacement.

❌ Mistake 2 — Using synthetic starch colloids

Hydroxyethyl starches increase AKI and mortality in the critically ill (6S, CHEST) and are regulator-restricted. Colloids don't improve survival over crystalloids — avoid HES.

❌ Mistake 3 — Over-resuscitation ("more is better")

Fluid overload causes oedema, anastomotic breakdown, ileus and respiratory failure. Target euvolaemia/zero balance and stop fluids once the patient is perfused.

❌ Mistake 4 — Reflex two-unit transfusion / liberal triggers

Restrictive triggers (Hb <70, or <80 with cardiac disease) are as safe or safer. Transfuse a single unit and reassess; treat the cause of anaemia.

❌ Mistake 5 — Forgetting the lethal triad in massive haemorrhage

Hypothermia, acidosis and coagulopathy (plus ionised hypocalcaemia from citrate) perpetuate bleeding. Warm everything, give calcium, and correct pH — not just more red cells.

❌ Mistake 6 — Delaying or omitting tranexamic acid

TXA saves lives in trauma and PPH but only when given early (<3 h). Give it promptly — it is cheap and widely available.

❌ Mistake 7 — Identity/clerical errors in transfusion

Acute haemolytic reactions are almost always ABO mismatches from mis-identification. Rigorous patient/sample/unit checking at the bedside prevents the most lethal transfusion hazard.

🎓 8 · Exam Pearls — DrNB / MD / EDAIC

Exam Pearls

Q: State the 4-2-1 maintenance rule.
4 mL/kg/h for the first 10 kg + 2 mL/kg/h for the next 10 kg + 1 mL/kg/h for each kg above 20 (e.g. 70 kg → 110 mL/h).

Q: How much crystalloid replaces 1 mL of blood loss?
~3–4 mL of isotonic crystalloid (it distributes across the extracellular space, so only ~⅓ stays intravascular). Blood or colloid replaces roughly 1:1.

Q: Balanced crystalloid vs 0.9% saline — why prefer balanced?
Large-volume saline causes hyperchloraemic metabolic acidosis and more AKI; balanced solutions (Ringer's/Plasma-Lyte) are more physiological and are the default.

Q: What did SAFE and the starch trials show?
SAFE: albumin ≈ saline overall but worse in TBI. 6S/CHEST: hydroxyethyl starch causes more AKI and death in the critically ill — avoid synthetic colloids.

Q: Restrictive transfusion trigger?
Transfuse at Hb <70 g/L (target 70–90); use <80 g/L for symptomatic patients or cardiovascular disease/ACS. Single-unit transfusions with reassessment.

Q: Outline a massive transfusion protocol.
Empirical ~1:1:1 RBC:FFP:platelets, early tranexamic acid, correct hypothermia/acidosis/hypocalcaemia (citrate), targets: fibrinogen >1.5–2 g/L, platelets >50 (>100 CNS), then switch to lab/viscoelastic-guided therapy.

Q: TACO vs TRALI?
TACO = circulatory overload — hypertension, raised JVP, cardiogenic pulmonary oedema → diuresis/slow rate. TRALI = immune non-cardiogenic pulmonary oedema within 6 h with normal filling pressures → supportive/ventilatory care.

Q: Most lethal transfusion reaction and its cause?
Acute haemolytic reaction from ABO incompatibility — almost always a bedside identification/clerical error. Stop immediately, resuscitate, and recheck identity and the unit.

📚 9 · References

References

Gropper MA, et al. (eds). Miller's Anesthesia, 9th Edition. Perioperative Fluid & Electrolyte Therapy; Patient Blood Management. Elsevier; 2020.
National Institute for Health and Care Excellence. Intravenous fluid therapy in adults in hospital (CG174); Blood transfusion (NG24). NICE.
Finfer S, Bellomo R, Boyce N, et al. (SAFE Study). A comparison of albumin and saline for fluid resuscitation in the ICU. N Engl J Med. 2004;350:2247–2256.
Myburgh JA, Finfer S, Bellomo R, et al. (CHEST). Hydroxyethyl starch or saline for fluid resuscitation in intensive care. N Engl J Med. 2012;367:1901–1911.
Hébert PC, Wells G, Blajchman MA, et al. (TRICC). A multicentre, randomised, controlled clinical trial of transfusion requirements in critical care. N Engl J Med. 1999;340:409–417.
CRASH-2 Collaborators. Effects of tranexamic acid on death, vascular events and transfusion in trauma patients. Lancet. 2010;376:23–32.
WOMAN Trial Collaborators. Effect of early tranexamic acid in women with post-partum haemorrhage. Lancet. 2017;389:2105–2116.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail's Clinical Anesthesiology, 6th Edition. Fluid Management & Transfusion. McGraw-Hill; 2018.