TME 77: What To Do Before You Need a Transfusion: The Truth Nobody Tells You About Blood Loss

Blood transfusion is not always the first answer.

And in many cases, it shouldn’t be.

There are clear thresholds, guidelines, and alternatives that can stabilise a patient long before we reach for that blood bag.

IV Fluids

When Should We Actually Transfuse Blood? (And Why People Get This Wrong)

Let’s start with the question everyone asks:

“At what Hb should we transfuse?”

There are different guidelines on Patient Blood Management and Transfusion threshold.

Most guidelines revolve around numbers:

• Hb < 7 g/dL → Consider transfusion for most stable adults.

• Hb < 8 g/dL → If the patient has cardiac disease, undergoing major surgery, or symptomatic.

  
  

But here’s the real key: We don’t transfuse to fix a number. We transfuse to fix a problem.

Ask:

• Is the patient in shock?

• Are they losing blood faster than we can replace?

• Is the oxygen delivery failing?

• Is there organ dysfunction?

• Is the cause reversible without blood?

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Most mild-to-moderate blood loss doesn’t need immediate transfusion.

What we need is time—time to assess, time to find the cause, time for blood to arrive.

That’s where crystalloids, colloids, and other substitutes enter the picture.

But unfortunately, this is where most confusion also begins.

Understanding Physiology: Why Numbers Aren’t the Whole Story

Most people focus on haemoglobin, but the body cares about something bigger: oxygen delivery. This depends on three things—how fast the heart pumps, how much haemoglobin is present, and how well that haemoglobin carries oxygen.

A low Hb doesn’t automatically mean danger if the heart can compensate for a while. Blood pressure can also trick you; it may look normal after fluids even when tissues are still starving for oxygen. Better clues come from the patient’s thinking, breathing, skin warmth, urine output, and lactate levels.

This is why transfusion decisions should never be based on numbers alone.

The real question is: Are the tissues getting enough oxygen? Once you start looking at the whole picture—rather than just one lab value—you make steadier, safer decisions for your patient.

Alternatives to Blood: When They Work, When They Don’t

There are options besides blood, but none of them replace what blood actually does. Iron therapy helps rebuild red cells, but it works slowly—days to weeks—and isn’t useful in sudden blood loss.

Erythropoietin boosts red cell production in select chronic conditions, not emergencies. Tranexamic acid reduces ongoing bleeding by strengthening clots, yet it cannot replace the blood already lost.

Vitamin K helps when bleeding is caused by certain deficiencies, but it won’t fix low volume or low haemoglobin.

In the operating room, techniques like cell salvage can return the patient’s own blood, but they need equipment and trained teams.

Even oxygen support only works if there is enough haemoglobin to carry it. These tools are valuable, but they are supportive measures.

They buy time, reduce unnecessary transfusions, and guide recovery—but they cannot perform the core job of blood during significant bleeding.

Blood

If Blood Isn’t Needed Yet, What Then? The Hidden World of Fluid Resuscitation

Imagine your body as a complex hydraulic system.

Blood doesn’t just carry oxygen; it maintains pressure, volume, warmth, and clotting. Remove too much of it, and everything collapses.

When the loss is mild or moderate, and oxygen delivery is still okay, we don’t replace the blood right away—we replace the volume.

The goal is simple:

Keep the pump (heart) working and maintain circulation until real blood arrives or the body recovers.

This is where crystalloids and colloids step in.

Crystalloids: The Quick Fix (But Don’t Expect Them to Do Everything)

Crystalloids are the simplest fluids we have—think Normal Saline or Ringer Lactate.

What They Do Well

• Quickly increase blood volume

• Useful in emergencies

• Cheap and widely available

• Help maintain circulation until help arrives

• Buy you the crucial minutes necessary for blood to reach

Their Big Limitations

• Cleared very fast

• Poor osmotic pressure → they leak out of vessels into tissues

• They dilute clotting factors and haemoglobin if overused

• No oxygen-carrying capacity

• No clotting support

You may feel better temporarily because the blood pressure stabilises, but crystalloids do not solve the underlying issue of low haemoglobin or loss of clotting power. They are simply a bridge.

Crystalloids will never replace the function of RBCs, plasma, or platelets.

Common Examples

• Normal Saline (0.9% NaCl)

• Ringer Lactate

• Plasmalyte

Colloids: A Slightly Better Bridge, but Still Not the Destination

Colloids are thicker fluids containing larger molecules—think Albumin, Dextran, Gelatins, HES (hydroxyethyl starch).

Where They Help

• Higher osmotic pressure → stay longer in the bloodstream

• Better volume expansion than crystalloids

• Useful when you need intravascular volume maintained more effectively

Where They Fail

• Still no oxygen-carrying capacity

• Still no clotting factors

• Some types interfere with coagulation

• More expensive

• Not proven to improve survival over crystalloids

• Can cause kidney injury (HES)

So yes, they hold volume better. But they’re still only a temporary measure.

Common Examples

• 5% or 25% Albumin

• Gelofusine

• Dextran

• Hydroxyethyl starch (use restricted in many countries)

The Real Difference: Crystalloids vs. Colloids vs. Blood

This is the part most people misunderstand. Let's simplify.

Feature / Function	Crystalloids	Colloids	Blood
Volume expansion	Rapid but short-lived	Longer-lasting	Sustained
Oxygen carrying	None	None	Strong (via RBCs)
Clotting factors	None	None	Present in plasma
Platelets	None	None	Present if platelet units used
Cost	Low	Higher	Variable
Best used for	Initial resuscitation	Temporary volume support	Correcting life-threatening losses

Crystalloids = speed

Colloids = staying power

Blood = survival

You cannot hydrate your way out of anaemia.

You cannot “volume expand” your way out of coagulopathy.

You need blood when the body needs oxygen, clotting, and long-term support.

Why Too Much Fluid Can Be Dangerous

Most people assume more fluid = better.

Not true.

Excessive crystalloids or colloids can cause:

• Dilution of clotting factors

• Tissue swelling

• Lung oedema

• Higher mortality in trauma and sepsis

• Worsening acidosis (Normal Saline)

This is why modern resuscitation focuses on balanced transfusion strategies, not drowning the patient in fluids.

Use fluids to stabilise.

Use blood to save.

Representative image of Artificial Blood

What About Artificial Blood? Is It Real or Just Hype?

Every few years a headline pops up:

“Artificial blood could replace transfusions.”

The reality:

• Several haemoglobin-based oxygen carriers (HBOCs) and perfluorocarbon emulsions are in trial stages.

• Some show promising oxygen delivery capability.

• None mimic the full complexity of human blood.

• Safety concerns (vasoconstriction, oxidative stress) still exist.

• They are not widely available and won’t be for some years.

So while artificial blood has promise, it is not a practical alternative today.

So What Should You Do in Minor Blood Loss or Borderline Cases?

If the blood loss is small or moderate:

• Assess vitals, perfusion, and oxygenation

• Check haemoglobin trend

• Start crystalloids only if needed for perfusion

• Avoid unnecessary fluid overload

• Identify the source of bleeding

• Correct reversible causes (iron deficiency, dehydration, sepsis)

• Monitor closely

If the blood loss is significant but not life-threatening:

• Crystalloids first

• Switch to colloids if intravascular volume needs support

• Prepare for transfusion

• Keep warm (hypothermia worsens clotting)

• Repeat labs

• Assess clinical response, not just numbers

If the patient is actively bleeding or unstable:

• Activate transfusion protocol

• Give RBCs + plasma + platelets in balanced ratios

• Use fluids sparingly

• Avoid haemodilution

If Hb is low but the patient is stable:

• Investigate cause

• Treat the root problem

• Avoid reflex transfusion

You want to intervene early but with clarity, not panic.