Anesthesiology APPLIED Exam › Critical care, resuscitation and trauma

Transfusion decisions: thresholds, type and screen, emergency release, preoperative anemia

Critical care, resuscitation and trauma·~5 min read· Physician-reviewed✓ Sourced · 5

Stem

A 74-year-old man, 82 kg, is on postoperative day 1 after total hip arthroplasty. He had a coronary stent 4 years ago and has no angina. Preoperative hemoglobin was 11.8 g/dL with a ferritin of 22 ng/mL that was never treated. This morning his hemoglobin is 7.4 g/dL; heart rate 92, blood pressure 118/70, no chest pain, the wound is dry. The surgical resident asks whether to give two units.

Question

Would you transfuse him, and how much?

Ideal answer

HeadlineYes, one unit and then reassess: he is stable, but with orthopedic surgery and coronary disease AABB allows a threshold of 8 g/dL.

Confirm he is stable and not bleeding, because the thresholds apply only to hemodynamically stable patients; ECG and troponin if he has symptoms.¹
One unit, then a repeat hemoglobin, because transfusing a unit at a time avoids needless second units.²
Intravenous iron for his iron deficiency, because postoperative hemoglobin under 10 g/dL with ferritin under 100 mcg/L responds and spares transfusion.²
Not a liberal target of 10, because liberal transfusion after major vascular or general surgery did not reduce death or major ischemic events.³

Watch for: chest pain, ST change, rising tachycardia, hypotension or a swelling thigh, which make this a bleeding or ischemia decision instead.

Breaking down the answer

AABB 2023 numbers — stable adults under 7 g/dL; clinicians may choose 7.5 for cardiac surgery and 8 for orthopedic surgery or pre-existing cardiovascular disease; stable children under 7; congenital heart disease 7 after biventricular repair, 9 for single-ventricle palliation.¹
TOP trial — 1428 high-cardiac-risk veterans, triggers under 10 versus under 7: 90-day death or ischemic events 9.1% versus 10.1%, not different; cardiac complications other than MI were lower with liberal transfusion.³
Acute MI is the exception — MINT randomized under 10 versus 7–8: 30-day death or MI 14.5% versus 16.9%, not significant, and harm from restriction was not excluded.⁴ Changes if: troponin rises with symptoms, so I aim higher.
Type and screen versus crossmatch — the screen gives ABO, RhD and unexpected antibodies but reserves no units; with a negative screen, an electronic or immediate-spin crossmatch takes minutes, while a positive screen means a full IgG crossmatch taking hours.⁵
Preoperative anemia — WHO defines anemia as under 13 g/dL in men and 12 in nonpregnant women;² his untreated iron deficiency was the missed patient-blood-management step.
When a screen expires — after transfusion or pregnancy in the previous 3 months, a sample is valid for 3 days;⁵ he needs a fresh one before more units.

Follow-up question

That evening his thigh swells, hemoglobin is 5.9 g/dL, pressure 78/40, and he is going back to the OR. The blood bank calls: his new antibody screen is positive and compatible units will take two hours. What do you do?

Follow-up answer

HeadlineHe is exsanguinating, so transfusion cannot wait; I take emergency-release uncrossmatched group O red cells and accept a small hemolysis risk.

I tell the blood bank the clinical urgency and ask them to identify the antibody and find antigen-negative units in parallel. Group O RhD-positive is acceptable in a man unless he is RhD-negative with anti-D;⁵ I start the massive transfusion protocol if bleeding is ongoing. Because an alloantibody can cause a delayed or acute hemolytic reaction, I watch urine color, temperature and pressure and send hemolysis labs.⁵ Then surgical control, and I document the decision.

Pitfalls that cost points

Quoting 7 g/dL to a bleeding, hypotensive patient; thresholds are for stable patients only.
Ordering a crossmatch for every case "just in case"; a type and screen suffices when transfusion is possible but unlikely.
Giving O-positive cells to a woman of childbearing potential when O-negative is available.

Rapid-fire

Q: Why draw a sample before the first emergency unit? A: So the patient's true type can be determined and type-specific blood started, whatever the number of O units already given.⁵

Q: How little ABO-incompatible blood causes acute hemolysis? A: As little as 10 mL.⁵

Q: Single-ventricle child, stable, hemoglobin 8.5? A: AABB suggests a threshold of 9 g/dL after single-ventricle palliation, so I transfuse.¹

Q: When is O-negative reserved? A: For RhD-negative females of childbearing potential and patients of unknown type when supply allows; O-positive suits others who lack anti-D.⁵

Q: Postoperative IV iron dose in trials? A: High-dose regimens around 1000 mg raised hemoglobin and reduced transfusion.²

Numbers to know

Item	Value
Stable adult threshold	< 7 g/dL¹
Cardiac surgery / orthopedic or CVD	7.5 / 8 g/dL¹
Congenital heart disease, children	7 biventricular; 9 single ventricle¹
TOP primary outcome, liberal vs restrictive	9.1% vs 10.1%³
WHO anemia	< 13 g/dL men, < 12 g/dL women²
Type and screen validity, recent transfusion or pregnancy	3 days⁵

Sources

1.Red Blood Cell Transfusion: 2023 AABB International Guidelines · AABB / JAMA (abstract), 2023 · europepmc.orgAbstract states all four recommendations and thresholds cited here.
2.An international consensus statement on the management of postoperative anaemia after major surgical procedures · Anaesthesia (PMC6686161), 2018 · europepmc.org
3.Liberal or Restrictive Postoperative Transfusion in Patients at High Cardiac Risk: The TOP Randomized Clinical Trial · JAMA (PMC12596742), 2025 · pmc.ncbi.nlm.nih.gov
4.Restrictive or Liberal Transfusion Strategy in Myocardial Infarction and Anemia (MINT) · N Engl J Med (abstract), 2023 · europepmc.org
5.ABCs of Blood Transfusions · OpenAnesthesia (IARS) · openanesthesia.orgType and screen, crossmatch methods, emergency-release uncrossmatched RBCs.

Facts on this page were checked against these sources on Nov 2, 2026. Guidelines change; confirm doses against current institutional protocols.