Haem Flashcards
What are the causes of microcytic anemia (MCV<80)
TAILS
Thalassaemia (disproportionately low MCV for Hb, normal RDW, increased RCC)
Anemia of chronic disease (late)
Iron-deficiency (most common) - RDW raised early
Lead poinsoning
Sideroblastic anaemia
Multiple myeloma
What are the causes of normocytic anemia
Acute blood loss
Hemolysis
G6PD
Bone marrow failure (aplastic anemia, myeloid metaplasia, myelofibrosis)
Chronic disease (Renal failure, Hypothyroidism)
Pregnancy
Early stage of most anaemia
What are the causes of macrocytic anemia (MCV>100)
B12 or folate deficiency (esp if MCV > 115)
Chronic ETOH
Liver disease
Hypothyroidism
Myelodysplasia
Marrow infiltration/aplastic anaemia
Antifolaxe drugs (phenytoin)
Cytotoxic drugs (hydroxyurea)
What are the admission criteria for non-emergent anemia
Developing cardiac symptoms (chest pain SOB, altered LOC)
Initial unexplained Hb <80 or hematocrit <30%
Difficulty obtaining outpatient care when Hb significantly low or major comorbidity
What are the causes of Iron deficiency anemia
Blood loss
- GIT, GUT (menses), chronic haemolysis
Malabsorption
- drugs (tetracyclines)
- IBD, coeliac, post gastrectomy
Pregnancy (increased demand)
Dietary
- childhood, vegetarian, high phytate (cereal, nut, seed)
How do you interpret iron studies.
Anemia of chronic disease has an abnormality in the mobilization of iron from reticuloendothelial cells. This anemia can be differentiated from iron deficiency by total iron-binding capacity, serum ferritin level, bone marrow examination, and non responsiveness to a trial of iron therapy.
High ferritin and serum iron in thalassaemia due to increased RBC turnover
What are the management options of iron deficiency and when to use IV iron replacement?
Rx:
Ferrous sulphate 325mg Daily
IV iron polymaltose
IV ferric carboxylates - less reaction
- Poor adherence or gastrointestinal side effects of oral iron
- Prefer to replete iron stores in one or two visits rather than over the course of several months. (second and thrid trimester pregnancy)
- Ongoing blood loss that exceeds the capacity of oral iron to meet needs (heavy uterine bleeding, mucosal telangiectasias).
- Anatomic or physiologic condition that interferes with oral iron absorption. (Gastric bypass, celiac, whipples)
- Coexisting inflammatory state that interferes with iron homeostasis.
What is the pathophysiology of anemia of chronic disease and their findings of iron studies?
Increased hepcidin synthesis (inhibits iron transport across cell membranes)
Decreased EPO
Marrow inhibition
Increased uptake and retention of iron within RES
Decreased RBC life span
Decreased serum iron and transferrin saturation.
Normal or decreased transferrin
Normal or increased ferritin
What are the different types of thalassemia?
Homozygous beta-chain thalassemia (Thalassemia major) - Mediterranian, severe anemia, most common single gene disorder
Heterozygous beta-chain thalassemia - mild anemia, mostly asymptomatic
Alpha-thalassemia - wide spectrum of manifestation, viable forms in asian/afro-Americans
List some causes of sideroblastic anemia.
Primary: Rare sex-linked form and idiopathic in elderly with refractory anemia (may respond to pyridoxine)
Secondary: Hemolytic/megaloblastic anemia, infections, carcinoma, leukemia, SLE, rheumatoid arthritis, lead poisoning and alcohol abuse, isoniazid, chloramphenicol
What is the underlying pathophysiology of sideroblastic anemia
Defect in porphyrin synthesis causes impaired Hb production leading to excess iron deposited in mitochondria of RBC precursors, leading to poor erythropoiesis and anemia
What are some causes of B12 deficiency
Inadequate dietary intake (vegans not taking fortified B12 diets, chronic alcoholism)
Inadequate absorption (pernicious anemia, gastrectomy, bacterial overgrowth, abnormal ileum eg IBD)
Inadequate use (enzyme deficiency, abnormal B12 binding protein)
Nitrous oxide uses - destruction of endogenous cobalamin
What are the symptoms and management of B12 defiency
Lethargy
Anaemia
Glossitis
Dementia, psychosis, depression
Cardiomyopathy
Peripheral neuropathy and Subacute degeneration spinal cord (decreased proprioception or vibratory sense, weakness and spasticity of lower limbs with altered reflexes)
Gastric adenocarcinoma (5 fold increase in risk)
Rx:
Hydroxycobalamin 1mg IM weekly for 6 weeks then 3 monthly
- 1mg alternate days if neurological symptoms
What are the causes of folate deficiency?
Inadequate dietary intake (poor diet/overcooked food, usually ETOH related)
Inadequate absorption (Celiac, blind loop syndrome, phenytoin or barbiturates),
Increased requirement (pregnancy, psoriasis, increased RBC turnover like poor erythropoiesis, hemolytic anemia, chronic blood loss and malignant disease like lymphoproliferative diseases)
Inadequate use (Dihydrofolate reductase inhibitors like methotrexate and trimethoprim or enzymatic deficiency either congenital or acquired)
What is the management of folate deficiency?
5mg folic acid daily
Folinic acid 10-100mg/kg/m2 of body area 3-6hrly for 72 hours if DHF toxicity
Replace B12 before giving folate as can precipitate combined degeneration spinal cord
What are the causes of pancytopenia?
Marrow failure
- aplastic anaemia
- viral infection (HIV, EBV)
- toxins
Marrow infiltration
- leukaemia
- lymphoma
- myelofibrosis
- myeloma
- megaloblastic anaemia
Toxins/Drugs
- chemotherapy
- immunosuppressants
Describe aplastic anemia and some potential causes.
Rare but significant illness caused by destruction of immune stimulated lymphocytes or failure of marrow stem cells - can affect all cell lines
Should be suspected in patients with anemia and normal indices, low reticulocyte count and history of exposure to certain drugs/chemicals
Causes
idiopathic (50-65%)
Fanconi syndrome
Drugs (chloramphenicol, phenyltuazone, sulphur drugs, anticonvulsants)
Dose related (radiation, antimetabolites, alkylating agents)
viral infections
SLE
Pregnancy
GvH disease
Rx with supportive, transfusion, GCSF, immunosuppression or stem cell transplant
What are the causes intrinsic hemolytic anemia
Intrinsic
- Membrane defect: Spherocytosis, elliptocytosis, paroxysmal nocturnal hemoglobinuria)
- Enzyme defect: G6PD deficiency, pyruvate kinase deficiency
- Hemoglobin defect: Thalassemia, sickle cell
What are the extrinsic causes of hemolytic anemia
Autoimmune
- incompatible blood transfuions
- SLE, RA, UC, methyldopa (warm agglutinin)
- Penicillin
- hepatitis
- EBV, mycoplasma (cold agglutinin in children)
- Lymphoma, CLL (cold agglutinin in adults)
Mechanical:
- MAHA
- prosthetic valves
- Long distance runners
Abnormal sequestration: hypersplenism
What are the intra and extravascular causes of hemolytic anemia
Intravascular (less common)
- MAHA
- Transfusion reactions
- Chronic cold agglutinin disease
- Traumatic (ECMO, Valves, March hemoglobinuria)
- Paroxysmal nocturnal haemoglobinuria
- Sepsis (Malaria, leptospirosis, C. Perfringens)
Extravascular (Within RES, phagocytosis within spleen)
- Membrane and hemoglobin defects
- Toxins
- Hypersplenism
What are the investigations and results suggestive of hemolytic anemia (bedside, smear, investigations)
Bedside UA:
- increased urobilinogen (sensitive but not specific)
- Hemoglobinuria (Blood on dipstick but no microscopy suggests intravascular hemolysis)
Peripheral blood smear:
- Schistocytes (fragments from abnormal intravascular shearing forces eg MAHA)
- Hainz bodies or bite cells (G6PD)
- Spherocytes (seen in spherocytosis and autoimmune hemolysis)
- Can also see Malignant cells or sickle cells
Lab tests:
Increased LDH (non specific marker of cell turnover, released from RBCs in hemolysis)
Increased reticulocyte count (increased rec cell turnover)
Increased unconjugated bilirubin (Hb breakdown)
Anemia with normal or low MCV. (Raised MCV if significant reticulocytosis as they are larger cells)
Decreased haptoglobin (intravascular anemia as haptoglobin mops up free circulating Hb for liver)
Haemosiderinuria after several weeks of intravascular anemia when haptoglobin depleted and Hb now accumulating in renal tubules. Needs Prussian blue staining at least 1 week after onset.
Coombs or DAT: identifies red cells coated with antibody or complement compents
What is direct and indirect Coombs test
Direct (patient red cells)
- detects antibodies and complement on patients RBC
- washed RBC mixed with anti-IgG and anti-C3 Ab and check if clumping occurs
- for haemolytic anaemia
Indirect (patient serum)
- detects antibodies in patient’s serum
- Serum mixed with donor RBCs to allow for antibody binding, and then mix with anti-human Ab to check for clumping
- Can measure titres
- for compatibility testing
How are autoimmune hemolytic anemias classified
Warm-antibody type (70-80%)
- Primary (50%)
- Secondary (50%): lymphoproliferative, post infectious, autoimmune disease, medications
(quinidine, NSAIDs, penicillin, cephalosporins, methyldopa)
- Usually extravascular and steroid responsive. IVIG and Splenectomy can be considered
Cold-antibody type (28-31deg Celsius)
- Cold agglutinin disease (secondary causes include chronic malignant and lymphoproliferative disease or acute transient post infectious like mycoplasma and EBV/CMV/malaria).
- Precipitated by cold exposure and presents with painful finger and toes with purplish discoloration. (NOT Raynaud’s which is vasospasm)
- Paroxysmal cold hemoglobinuria (idiopathic, acute infections or chronic from syphilis)
- Unlikely to be steroid responsive and no rule of splenectomy
Mixed cold and warm antibody
- Lymphoproliferative disorders, autoimmune disorders
- Usually steroid responsive
What is paroxysmal nocturnal haemoglobinuria
- Primary or secondary from acute infections and chronic syphilis
- Genetic mutation leading to stem cells producing cells with abnormal surface proteins
- Allows complement deposition and chronic hemolysis
- Predisposing to thrombosis
- Managed with immunosuppression and bone marrow transplantation
- Eculizumab blocks action of complement
List some diseases that can cause autoimmune hemolytic anemia
Neoplasms (CLL, CML, lymphoma, myeloma, thyoma, ovrain teratoma)
Collagen vascular disease (SLE, RA, periarteritis nodosa)
Infections (Mycoplasma, syphilis, malaria, CMV, EBV, coxsackie, Bartonella)
Miscellaneous (thyroid, UC, drug immune reactions)
What are the causes of microangiopathic hemolytic anemia (MAHA)
DIC
TTP
HUS
Pre-eclampsia
Malignant hypertension
Prosthesthetic heart valves
Vasculitis (Wegners)
Malignancy
What is G6PD deficiency pathophysiology and some triggers
X-linked deficiency of glucose-6-phophate dehydrogenase
Needed in early steps of glycolysis and therefore unable to maintain glutathione
Leads to hemolysis from oxidative stress
Triggers
- Aspirin
- Sulpha drugs
- Methylene blue
- Vit K
- Antimalarials
- Fava beans
- Nitrofuratoin
What is the pathophysiology of sickle cell disease and some triggers of a sickle cell crisis
Abnormal allele at gene loci for Hb beta chain relates to single amino acid change within the beta chain and results in anbormal tertiary structure
What are the absolute contraindications of thrombolysis
- any prior intracranial hemorrhage
- known structural intracranial cerebrovascular disease (eg, arteriovenous malformation)
- known malignant intracranial neoplasm
- ischemic stroke within 3 months
- suspected aortic dissection
- active bleeding or bleeding diathesis
- recent surgery encroaching on the spinal canal or brain
- recent significant closed-head or facial trauma with radiographic evidence of bony fracture or brain injury
What are the relative contraindications of thrombolysis
- age >75 years
- current use of anticoagulation
- pregnancy
- noncompressible vascular punctures
- traumatic or prolonged cardiopulmonary resuscitation (>10 minutes)
- recent internal bleeding (within 2 to 4 weeks)
- history of chronic, severe, and poorly controlled hypertension
- severe uncontrolled hypertension on presentation (systolic blood pressure >180 mm Hg or diastolic blood pressure >110 mm Hg)
- dementia
- remote (>3 months) ischemic stroke
- major surgery within 3 weeks
How is thrombolysis dosed and administered
> 65kg 100mg alteplase
<65kg ~1.5mg/kg total dose alteplase
Regiment depends on cause (stroke, STEMI, PE) eg
Can consider half dose in high risk bleeding pts with PE
Tenecteplase
<60 kg: 30 mg (6000 units)
60 to 69 kg: 35 mg (7000 units)
70 to 79 kg: 40 mg (8000 units)
80 to 89 kg: 45 mg (9000 units)
90 kg or more: 50 mg (10 000 units)
How do you reverse thrombolysis if pt is starting to develop major bleeding
STOP IT ALL
Don’t forget to reverse any other agents given (antiplatelets, anticoagulants)
FBC, Coags, Fibrinogen level
10 units cyropercipitate. Aim Fibrinogen 150-200mg/dL
2 units FFP if bleeding ongoing
Tranexamic acid 10 milligrams/kg IV every 6–8 h
How does warfarin work and describe its reversal agents
Vit K inhibitor (Factor 2,7,9,10)
Protein C and S inhibition first - transient prothrombotic effect for first 24-36hrs
Metabolized by CYP450
Reversal depends on INR and bleeding
INR < 4.5 and no bleeding
- Lower or omit next dose of warfarin and recommence at lower dose
INR 4.5-10 and no bleeding
- Cease warfarin, Vitamin K 1-2mg orally if bleeding risk high, recheck INR and resume warfarin at lower dose
INR > 10 and no bleeding
- Cease warfarin, Vitamin K 3-5 mg IV/PO, daily INR and resume at lower dose
- If bleeding risk high, prothrombinex 15-30 units/kg
INR > 1.5 and major bleeding
- Cease warfarin, Vitamin K 50mg IV, prothrombinex 50units/kg IV, FFP 150-300ml
Any INR and minor bleeding
- Omit warfarin dose, consider Vitamin K 1-2mg PO
IV Vit K can cause anaphylactoid reaction when given quickly
Compare Prothrombinex to FFP
Prothrombinex preferred over FFP as
- Lower volumes
- Faster and more consistent reversal
- No need for it to be thawed or crossmatched
- No risk of immune reactions (TRALI, fever)
However significantly higher cost
Which drugs would decrease or increase INR with concurrent warfarin use
CYP inhibitors INCREASE warfarin levels (INR)
- Azoles: ketoconazole, fluconazole
- Antibiotics: sulfonamides, metronidazole, ciprofloxacin, chloramphenicol, macrolides, isoniazid
- Amiodarone
- Cimetidine
- Omeprazole
- Sodium valproate
- Grapefruit
CYP inducers DECREASE warfarin levels (INR)
- Anticonvulsants: phenytoin, carbamazepine, barbituates (NOT Valproate)
- Steroids: dexamethasone, prednisolone, glucocorticoids
- Antibiotics: rifampicin, griseofulvin
- Others: nicotine, alcohol, cigarette smoke, St John’s Wort
Describe the effect of Dabigatran and its reversal
Direct thrombin inhibitor (factor IIa)
Renally excreted
Short half like (12-14hrs) and peak effect in 2hrs
A normal thrombin time excludes a significant coagulopathy due to dabigatran while a diluted thrombin time is even more specific.
Reversal
- Oral activated charcoal if recent or excessive ingestion
- Maintain urine output
- Consider 50 units/kg IV (maximum dose 5000 units) Prothrombinex
- TxA 1g over 10minutes and then 1g over 8hrs
- For severe bleeding or urgent reversal, idarucizumab (PRAXBIND) 5 grams IV infusion given as two consecutive doses of 2.5 g over 5 to 10 minutes each.
- Consider hemodialysis for pts with kidney impairment, life-threatening bleeding or a high risk of life-threatening bleeding in the immediate future or idarucizumab administration has failed to reverse coagulopathy.
What is the effect of apixaban/rivaroxaban and its reversal
Direct Xa inhibitor
Reversal
- Oral activated charcoal if recent or excessive ingestion
- Consider 50 units/kg IV (maximum dose 5000 units) Prothrombinex
- TxA 1g over 10minutes and then 1g over 8hrs
- Very protein bound so can’t dialyse
- Andexanet is experimental drug that binds to Factor Xa inhibitors but may not be available
What is the effect of heparin/clexane and their reversal
Heparin - Binds and potentiates antithrombin (inactivates thrombin and Xa)
LMWH Inhibits factor Xa (less effective)
Therapeutic dosing of clexane is 1mg/kg BD or 1.5mg/kg daily
In obese pts use 1mg/kg BD (actual body weight) up to 150kg or BMI>40
HITS, alopecia and osteoporosis all potential side effects
Reversal with protamine (rapid administration may cause hypotension, bradycardia, and anaphylactoid reaction)
- 1mg/100units heparin or 1mg/1unit of clexane < 8 hours (half dose if between 8-12 hours sine last dose)
Protamine lasts for ~2 hours, so multiple doses may be required
Follow Xa level after giving protamine and then q2hr. aPTT at 10 minutes and then 2-8hrs for heparin
Protamine neutralizes at most ~60-75% of enoxaparin
What is MTP, when should it be activated and how is it administered?
Replacement of >1blood volume in 24hrs or >50% blood volume in 4hrs
Goals to the management MTP
- Early recognition of blood loss
- Maintenace of tissue perfusion and oxygenation by restoration of the blood volume and Hb
- Arrest of bleeding with early surgical or radiological intervention
- Appropriate use of blood component therapy to manage coagulopathy
A transfusion ratio of 1:1:1 would equate to 4 units of red blood cells, 4 units of FFP and 1 adult unit of platelets.
Need to remember Fibrinogen replacement: 3-4 g of fibrinogen (10 units of whole blood cryoprecipitate, or 4-5 units of apheresis
cryoprecipitate)
What is the definition of a critical bleed
1) Major hemorrhage that is life-threatening and is likely to result in the need for massive transfusion (greater than or equal to 5
units of red blood cells in 4 hours)
2) Hemorrhage of a smaller volume in a critical area or organ (e.g., intracranial, intraspinal or intraocular), resulting in patient
morbidity or mortality.
What are the therapeutic parameters that are needed to be monitored during MTP
Temp >35
pH>7.2
BE<-6
Lactate<4
Ca>1.1
Plt>50
PT/APTT<1.5 x ULN
INR<1.5
Fibrinogen>1
Check every 30 minutes or every 4 units of blood
