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- RBC infection
- Sickle Cell Disease (HbS)
SpherocytosisPrimary hereditary spherocytosis: abnormal cytoskeletal protein (spectrin) (AD) Secondary: autoimmune hemolysis Findings: splenomegaly / increase in MCHC / may have normal appearing peripheral smear Diagnosis: osmotic fragility test Treatment: splenectomy curative RBC infectionmalaria, Carrion’s disease, babesiosis, C. perfringens sepsis March hemoglobinuria massive intravascular hemolysis HemoglobinopathyHemoglobinopathy is abnormal structure of a globin chain Physiology Increased O2 affinity elevated erythropoietin, erythrocytosis Decreased O2 affinity blue Hb > 5 g/dL leads to cyanosis Methemoglobinemia Causes: oxidizing compounds (nitrites, dapsone, local anesthetics, some anti-malarials, various chemicals: anilines, nitrosohydrocarbons) Mechanism: O2 saturation curve shifted to left (too much Fe3+) or HbM / also caused by NADH-diaphorase deficiency (used to reduce circulating metheme) Labs: elevated blood levels of HbM, peripheral smear (Heinz bodies, bite cells) Presentation: cyanosis, gray-brown cyanosis or brownish discoloration of patient’s skin (at levels of 15-20%) and blood, hemolysis, tachycardia, tachypnea, lactic acidosis (levels > 45%) O2 sats or pulse oximetry will be in 80’s (or normal) in spite of normal PaO2 (because the oxygen is in the blood, just not delivering to tissues properly) Treatment: 100% O2, can give IV methylene blue for levels > 30% or symptomatic or evidence of ischemia, in severe cases consider exchange transfusion and/or hyperbaric O2 Unstable Hb (Heinz body anemia) RBC becomes rigid, lysed by RE system / Heinz bodies seen with supravital dye Sickle Cell Disease (HbS)Genetics: valine as 6th amino acid on B-chain / masked for 6 months by HbF (a2d2) / alpha thalassemia carriers have lower MCHC and less severe course / HPFH (hereditary persistence of HbF) also lessens severity / electrophoresis (not solubility) to distinguish trait Mechanism: deoxy-HbS forms tactoids causing sickling, dehydration at cellular level (as well as circulatory), activated platelets release thrombospondin which binds sickled RBCs Triggers: deoxygenation, acidosis, dehydration, venous stasis, variations in body temperature / physical, emotional stress also a trigger Presentation: anemia, jaundice, cholelithiasis, aplastic crisis, hemolytic crisis, dactylitis, leg ulcers, priapism, renal papillary necrosis, infarctive crisis, sequestration crisis (sudden pooling of RBC in RES, common COD in young patients / autosplenectomy usually complete before age 5, Sickle C and thalassemias may have splenic sequestration into adulthood Complications: Heme: hemolytic anemia, can have aplastic crisis, channel defects give target cells, congestive heart failure Renal: nephrotic syndrome, progressive renal failure (decreased erythropoietin), isosthenuria, mild nitrogen retention, inability to concentrate urine, painless hematuria (also sickle cell trait) GI: choledocholithiasis (mimic gall bladder pain), cholecystitis Infections/Immune compromise cellular immunity depressed, B-cell antibody production depressed, splenectomy (allows increased susceptibility to encapsulated organisms) increased UTI (commonly precipitates crises / UTI also increased with sickle trait) pneumonia (esp. mycoplasma) osteomyelitis (S. aureus, Salmonella) abscesses Infarcts/hemorrhages – more common in children / can involve large veins Bone: fish-mouth vertebrae (biconcave), expansion of bone marrow, aseptic necrosis (head of femur), chronic leg ulcers CNS: stroke (can necessitate blood transfusion to decrease viscosity), cognitive (silent infarcts), sub-arachnoid hemorrhage and seizures (breakdown product of Demerol also causes seizures) Eye: retinopathy, vitreous hemorrhages, retinal detachment (blindness) / risk increases with age (vascular) hepatic infarcts, icterus [pic] papillary necrosis priapism Labs: CBC: Hgb 7-10 (rarely higher than 10) / 5 or less suggests associated G6PD or folate deficiency / total WBC 15-20 / reticulocytosis (except in aplastic crisis) / macrocytosis (many young RBC’s) [pic] peripheral smear: splenic dysfunction sideroblasts, target cells, Howell jolly bodies [pic] LDH is useful to validate presence of hemolytic state Diagnostic studies: newborn screening / 99% of sickle cell patients present before age 1 anyway metabisulfite test: will show sickling in blood specimen of any patient with HbS or sickle cell trait or HbC monitor HBS levels (predict crisis frequency) monitor blood counts (based on clinical assessment) pulmonary function testing – reduce ACS # / determine need for IS and ß-agonists transcranial Doppler (predict stroke risk)
cellular hydration: Mg salts, Clotrimazole (small doses inhibit Gados channel) Other: bed rest, O2, ? steroids, IVIG
folate / L-arginine (under investigation) ACE inhibitors reduce proteinuria, slow progression of renal failure [ongoing studies] Induction of HgF hydroxyurea (3-4 wk onset, also increases cell volume, decreases granulocytes) [usually only used in severe cases] 10-15 mg/kg/day q am 6-8 wks / check blood counts, increase dose if necessary / consider reasons for failure of HgF induction – acceptable myelotoxicity plat > 80,000 WBC > 20,000 / 1/3 respond to hydroxyurea [6 months – 1yr onset] short chain fatty acids (may work faster) Transfusion: acute/chronic anemia / renal failure / many other needs / do NOT transfuse just to elevate Hg/Hct unless indicated (uncomplicated surgery, pregnancy, anemia-induced end-organ ischemia, anemia-induced pain, to decrease viscosity with ongoing thrombosis, stroke) Course: 60% at least one episode per year / 1-2% have constant pain ( > 6 episodes/yr) Prognosis: peak mortality: 6 months – 1 yr / late adolescent, young adults Acute chest syndrome Definition: new pulmonary infiltrate on CXR, fever, respiratory symptoms (can be due to pneumonia, PE, vaso-occlusion) Incidence: children and young adults (4 fold greater incidence), often occurs perioperatively Causes: bone marrow embolism, fat embolism, infection (14% bacteremic, chlamydia > mycoplasma > RSV) older patients w/ ACS more pain, more mortality Treatment: Oxygen (give oxygen even if sats okay because it reduces sickling of RBC’s) Bronchodilators Antibiotics (must cover typical and atypicals, use macrolides or quinolones) Transfusion for PaO2 drop of more than 10% or PaO2 < 70 / exchange transfusion if Hct already ≥ 30 (Careful) hydration (give fluid, but not so much to cause pulmonary edema) Long term – consider hydroxyurea aplastic crisis most often from parvovirus B19 / usually self-limiting but may require transfusion HbC (excellent prognosis) mutation on B chain (lysglu) / crystalloids (pathognomonic, rarely seen in smear) / many target cells (codocytes) / retinal vascular lesions worse in SC than SS patient / tend to have enlarged spleen rather than asplenia Download 3.95 Mb. Share with your friends:
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