CCRN Hematology and Immunology Review: Transfusion Reactions, DIC vs HIT vs ITP, Tumor Lysis and Neuromuscular Crises

Hematology problems rarely arrive labeled. A unit of blood is running when the patient becomes short of breath, a platelet count halves on the sixth day of heparin, a chemotherapy patient's potassium climbs overnight. CCRN items in this area test whether you recognize the pattern early and take the first nursing step. This review uses the MSD Manual chapters and the consensus paper named in each section, all opened on October 28, 2026. It gives no doses; those belong to your protocols and the prescriber's orders.

What CCRN Category C lists under hematology and immunology

Category C of the Adult CCRN test plan (exams on and after November 12, 2025) is Endocrine, Hematology/Immunology, GI, Renal/GU and Integumentary, at 21%. AACN publishes no item counts per subsystem. The hematology and immunology list:

• Anemia
• Autoimmune disorders: lupus, myasthenia gravis and Guillain-Barré syndrome are the examples
• Coagulopathies: ITP, DIC and HIT
• Myelosuppression: thrombocytopenia and neutropenia
• Oncologic complications: tumor lysis syndrome and neutropenia
• Transfusion reactions: TRALI and TACO

The matching testable nursing actions are managing patients with bleeding and clotting disorders, blood dyscrasias such as anemia, and transfusion of blood products, including exchange and massive transfusions. Two of these topics moved in 2025: TRALI used to sit under Respiratory, and myasthenia gravis and Guillain-Barré under Neurological, as the 2025 test plan changes guide shows. This guide doesn't cover lupus.

A suspected transfusion reaction: the first minutes

The MSD Manual's transfusion complications chapter (full review March 2026) lists the most common symptoms of a reaction as chills, rigor, fever, dyspnea, light-headedness, urticaria, itching and flank pain. If any of them appears, other than localized urticaria and itching, it says:

1. Stop the transfusion immediately and keep the IV line open with normal saline.
2. Send the rest of the product and patient blood samples to the blood bank for investigation.
3. Don't restart that unit, and don't start any unit already issued.
4. Hold further transfusion until the cause is known, unless the need is urgent, in which case MSD says type O Rh-negative red cells are used.

Three details change answers:

• Fever is never "just fever." MSD says febrile reactions must be investigated as for an acute hemolytic reaction, because fever and chills also herald hemolysis.
• Identification is the first check for hemolysis. MSD names mislabeled samples and failure to match the patient with the unit as the usual causes of an acute hemolytic reaction, and rechecking the labels on the sample and the patient as one of the first steps when it's suspected.
• Anesthesia hides the symptoms. Under general anesthesia, MSD says the only signs of an acute hemolytic reaction may be hypotension, uncontrollable bleeding from incisions and mucous membranes from associated DIC, or dark urine.

MSD also states a rule worth remembering for any bedside item: medications must never be mixed with the blood.

A fictional Passy vignette. A sedated, ventilated patient two hours after a liver resection is receiving her second unit of red cells. Her pressure drifts from 112/68 to 86/50 mm Hg, the IV sites start oozing, and the urine in the catheter bag turns dark. She can't report chills or back pain. The pattern fits MSD's description of a hemolytic reaction under anesthesia: stop the unit, keep the line open with saline, check the patient and unit identification, notify the provider and the blood bank, and send the unit and samples as your protocol directs. The free CCRN set has an awake patient's version of this decision, and once the steps are clear you can try the transfusion reaction scenario in the free CCRN set.

TRALI or TACO: two kinds of pulmonary edema after a transfusion

Both cause respiratory distress from pulmonary edema after a transfusion. The 2019 consensus redefinition of TRALI (Vlaar and colleagues, Transfusion) says both are characterized by pulmonary edema beginning within 6 hours of transfusion, and that the difference lies in the mechanism.

MSD adds that mild TRALI looks like TACO and is probably often missed, and that red cells should be infused slowly in patients at risk of overload. The consensus panel asks clinicians to report every case of pulmonary edema after a transfusion to the transfusion service, so it can be classified. For the nurse, the sequence is the same as for any reaction: stop the transfusion, support oxygenation, report, and let the pattern of blood pressure, fluid balance and response decide the treatment, rather than reaching for a diuretic by reflex.

Massive transfusion: what to watch besides the hemoglobin

MSD defines massive transfusion as at least one blood volume in 24 hours, for example 10 units in a 70-kg adult. Its risks are partly about what the blood lacks and partly about what it brings:

• Dilution. Large volumes of red cells and crystalloid dilute clotting factors and platelets, and MSD describes a lethal triad of acidosis, hypothermia and bleeding. Massive transfusion protocols give plasma and platelets early rather than trying to catch up.
• Cold. Rapid transfusion of cold blood can cause arrhythmias or cardiac arrest. MSD says to use an IV set with a heat-exchange warmer, and that other warming methods such as microwave ovens are contraindicated because they can damage the cells.
• Citrate and potassium. MSD says these toxicities generally aren't a concern even in massive transfusion, but can be amplified by hypothermia; patients with liver failure may struggle to metabolize citrate, and hypocalcemia can result but rarely needs treatment.

For ordinary anemia, MSD's blood products chapter says oxygen-carrying capacity may be adequate with hemoglobin as low as 7 g/dL in healthy patients, with transfusion sometimes indicated at higher levels in patients with reduced cardiopulmonary reserve or ongoing bleeding.

DIC, HIT or ITP: three ways to lose platelets

All three lower the platelet count. They differ in whether the patient bleeds or clots, and in what the nurse must stop.

MSD also notes that slowly evolving DIC, often from cancer, causes mainly venous thrombosis rather than bleeding, and that a fibrinogen falling on two consecutive measurements helps make the diagnosis, because many disorders raise fibrinogen as an acute-phase reactant. For HIT, MSD points to the 4-T score to estimate pretest probability. Coagulopathies are part of the 21% category, and the Category C question set planned for CCRN prep mixes them with endocrine, GI and renal items.

A fictional Passy HIT vignette. Day 6 after aortic valve surgery, a patient on subcutaneous heparin with heparin-flushed lines has a platelet count that has fallen from 230,000 to 98,000/mcL. This morning his left foot is cool and pale with a weaker pulse. MSD says heparin should be stopped immediately, pending antibody results, in a thrombocytopenic patient who develops a new thrombosis or whose count falls by more than 50%; this patient has both. The nursing step is to report both findings together, stop heparin from every source your protocol covers, flushes included, and expect a nonheparin anticoagulant rather than low-molecular-weight heparin.

Tumor lysis syndrome: the lab pattern to recognize

MSD's chapter on adverse effects of cancer therapy (full review July 2024) explains tumor lysis syndrome as the release of cell contents when large numbers of cancer cells die, mainly after treatment of leukemias and lymphomas and sometimes after immune therapies such as CAR-T cells. Its diagnostic criteria form a pattern:

The consequences follow from the labs: uric acid and calcium phosphate can precipitate in the renal tubules and cause acute kidney injury, hyperkalemia can cause arrhythmias, and low calcium can cause tetany; symptoms include lethargy, nausea, vomiting and seizures. MSD stresses prevention with vigorous IV hydration and uric acid-lowering drugs before therapy when the syndrome can be anticipated, such as in cancers with rapid cell turnover, close laboratory and cardiac monitoring, and one calcium caution: calcium shouldn't be given for asymptomatic hypocalcemia unless the hyperphosphatemia is corrected, because it can increase calcium phosphate precipitation, while symptomatic hypocalcemia, such as arrhythmias or tetany, is treated regardless. Patterns like this suit the 117 Category C flashcards planned for CCRN prep. The GI, renal and skin review covers the kidney side.

Neutropenic fever on a critical care unit

MSD grades neutropenia as mild (1,000 to 1,500/mcL), moderate (500 to 1,000) and severe (below 500), and notes that below about 200/mcL the usual signs of inflammation may be muted or absent, so fever may be the only clue. Its rule is short: if fever or hypotension is present in a neutropenic patient, serious infection is assumed and empiric, broad-spectrum IV antibiotics are given immediately. For the nurse, a new fever in a neutropenic patient is reported at once, not rechecked in an hour. The sepsis and shock guide covers the timing rules for antimicrobials.

Myasthenic crisis, cholinergic crisis and Guillain-Barré: watching the breathing

Both neuromuscular disorders sit on the CCRN list as autoimmune problems, and both can end in respiratory failure.

Myasthenia gravis. The MSD chapter (full review May 2026) says myasthenic crisis, severe generalized weakness or life-threatening respiratory muscle weakness, occurs in about 15 to 20% of patients at least once, often triggered by infection, and that once respiratory insufficiency begins, failure can come quickly. Bedside pulmonary function tests such as forced vital capacity help detect impending failure, and crisis is treated with IV immune globulin or plasma exchange; glucocorticoids have little immediate effect, and more than half of patients worsen acutely when high-dose glucocorticoids are started. MSD says a severe cholinergic crisis, weakness from too much anticholinesterase medication, can usually be told apart by fasciculations, increased tearing and salivation, tachycardia and diarrhea, and that a patient who responds and then deteriorates needs respiratory support and a pause in anticholinesterase drugs. Its list of medications that can worsen myasthenia includes aminoglycosides, quinine, magnesium sulfate, procainamide, calcium channel blockers and immune checkpoint inhibitors, which is worth checking against every new order.

Guillain-Barré syndrome. MSD (full review May 2026) describes relatively symmetric flaccid weakness that usually starts in the legs and ascends, with lost deep tendon reflexes, and calls it a medical emergency needing constant monitoring, typically in an ICU. About 20% of patients need intubation and mechanical ventilation. The chapter's monitoring rule: measure forced vital capacity every 6 to 8 hours, and intubate if vital capacity falls below 15 mL/kg. Inability to lift the head off the pillow is another danger sign, often appearing with diaphragm weakness. Autonomic dysfunction, which MSD calls infrequent but life-threatening, can cause blood pressure swings, arrhythmias, inappropriate ADH secretion, gastrointestinal stasis and urinary retention. Treatment is IV immune globulin or plasma exchange, and MSD says glucocorticoids shouldn't be given because they may worsen outcome.

Worked arithmetic (fictional; arithmetic is Passy's). A 70-kg man with Guillain-Barré has vital capacities of 2.1 L, then 1.4 L, then 1.1 L over 18 hours. MSD's threshold is 15 mL/kg, so 15 × 70 = 1,050 mL. He hasn't crossed it yet, but he has lost about half his capacity and is 50 mL away, and he can no longer lift his head: the trend, not the last number, is the reason to call the team now. A rule like 15 mL/kg sticks better with a memory trick from the planned AI Rescue feature.

Your next step for CCRN hematology and immunology

Make one page with three rows: the transfusion reaction steps, the DIC/HIT/ITP table, and the TLS lab pattern, and say each one aloud from memory before your next shift. Then use the Adult test plan guide to find the rest of Category C in your course materials, and the endocrine review for its largest clinical neighbor.