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OR Playbook
Step 6 · Lines & Fluids

IV Lines, De-airing, Fluid Warmer & Pressure Bags

Spiking and priming a bag, getting every bubble out, hanging blood, and running fluids under pressure.

8 min read

The TL;DR

  • Prime the line SLOWLY — fast flow whips air into bubbles that are hard to clear.
  • De-air at the drip chamber (fill to ½), then chase remaining bubbles up toward the bag and bleed every stopcock/port.
  • A pressure bag inflated to ~300 mmHg drives rapid fluid or blood; it is NOT for routine maintenance.
  • Run all rapid, large-volume, or cold fluids — and ALL blood — through a fluid warmer.
  • Blood gets its own filtered tubing and is given with normal saline (or a compatible isotonic), never LR through the same line per many protocols.

01Spike, prime, and de-air

Air in a line is both an annoyance (alarms, sluggish flow) and, in volume, a real embolism risk. Get it right once at setup.

PRESSURE BAGinflate to ~300 mmHg for rapid flow / bloodLR /Blooddrip chamberfill to ½ — squeeze & releaseroller clampGET THE AIR OUT• Prime slowly — fast flow makes bubbles• Invert injection ports as fluid passes• Flick/tap bubbles up toward the chamber• Open stopcocks & bleed each onetap bubbles toward the bagFLUID WARMERwarm all rapid / large-volume fluids & bloodIV in patientconfirm flush & free flow before induction
swipe diagram horizontally →
Bag in a pressure bag → drip chamber half-filled → de-air the tubing → through the warmer → to the patient.

02Priming the line without bubbles

  1. Close the roller clamp. Spike the bag (twist firmly, don't contaminate the spike).
  2. Squeeze the drip chamber until it's about half full — too full and you can't see drips; too empty and you draw air into the line.
  3. Open the roller clamp slowly and let fluid walk down the tubing by gravity. Slow is key — a fast flush froths the fluid into a column of small bubbles.
  4. Hold the line straight and let the fluid front push the air out the end into a trash/cup.
  5. Invert and tap any injection ports and the stopcocks as the fluid passes so air doesn't hide in them.
  6. Close the clamp when primed, cap the end sterilely.
Pearls
  • Tap and flick stubborn bubbles UP toward the drip chamber — they rise, so work with gravity.
  • Invert needleless ports and Y-sites while priming; that's where air loves to hide.
Common mistakes
  • Flushing fast to "save time" — you'll spend longer chasing the bubbles you just made.
  • Forgetting to bleed the stopcocks — air trapped there enters when you give a drug.

03Pressure bags — rapid flow & blood

A pressure bag is a sleeve with a bladder and a hand pump that squeezes the fluid bag to drive flow faster than gravity.

  • Slide the fluid bag in, hang from the same hook, inflate to ~300 mmHg (stay in the green zone on the gauge).
  • Used for rapid resuscitation, blood products, and arterial-line flush systems (a-line flush bags run continuously at 300 mmHg, ~3 mL/h).
  • De-air the bag first. Under pressure, any residual air is pushed into the patient — a real air embolism risk. Squeeze air out of the bag before pressurizing.
  • It empties fast — watch it, and de-pressurize before it runs dry so you don't pump the residual air in.
Common mistakes
  • Pressurizing a bag that still has an air pocket — that air goes straight to the patient.
  • Walking away from a pressure bag — it empties in minutes and then pushes air.

04Fluid warmer

Cold fluids cause hypothermia, which worsens coagulation, drug metabolism, and wound healing. A fluid warmer heats fluid inline on its way to the patient.

  • Run all blood products, all rapid/large-volume fluids, and cold fluids through the warmer.
  • Prime the warmer per its design (it has its own tubing/cassette) and de-air it like any other segment.
  • Confirm it's actually powered on and at temperature — an unplugged warmer is just extra tubing.
Pearls
  • For long cases or big resuscitations, warm everything — the patient cools faster than you'd think under drapes.

05Hanging blood

Blood has extra rules:

  1. Two-person check of the unit against the patient's ID and the blood bank tag — name, MRN, unit number, blood type, expiration. This is a hard stop.
  2. Use blood tubing with an inline filter (170–260 micron).
  3. Prime with / co-administer normal saline (or a compatible isotonic). Avoid LR in the same line in many protocols (calcium + citrate clotting concern).
  4. Run it through the fluid warmer; pressure bag if rapid transfusion is needed.
  5. Watch for a reaction — fever, hypotension, hemoglobinuria — especially in the first minutes.
Common mistakes
  • Skipping or shortcutting the two-person identity check — wrong-unit transfusion is catastrophic.
In this guide
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Transferring the Patient (Bed → OR Table)
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Induction — Putting the Patient to Sleep