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Absite Topic Review

Absite Topic Review. Nir Hus, MD, PhD. 10/13/08. Persistent Low Plt Post Splenectomy for ITP. Idiopathic (immune) thrombocytopenic purpura (ITP) is the most common indication for elective splenectomy.

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Absite Topic Review

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  1. Absite Topic Review Nir Hus, MD, PhD. 10/13/08

  2. Persistent Low Plt Post Splenectomy for ITP • Idiopathic (immune) thrombocytopenic purpura (ITP) is the most common indication for elective splenectomy. • It is an acquired disorder in which autoantibodies are produced against a platelet glycoprotein. • The spleen is the major site for the production of antiplatelet antibodies and also serves as the principal site of platelet destruction. Nir Hus

  3. Persistent Low Plt Post Splenectomy for ITP • Children • usually present with acute ITP, often associated with a recent viral syndrome. • In 90% of cases, the disease spontaneously remits within 6 to 12 months. • Only refractory cases require splenectomy. Nir Hus

  4. Persistent Low Plt Post Splenectomy for ITP • Adults • Typically present with a more chronic form of ITP that is much less likely to spontaneously remit. • Asymptomatic patients with platelet counts greater than 50,000/mm3 may simply be followed. • Symptomatic patients or those with counts less than 30,000/mm3 should be treated with oralglucocorticoids. • Greater than 50% of patients respond to glucocorticoids. • In refractory cases, or in patients with bleeding, intravenous immunoglobulin (IVIG) is used, although the effects are transient. • Indications for splenectomy are failure to respond to medical therapy and intolerable side effects from steroid administration. Nir Hus

  5. Persistent Low Plt Post Splenectomy for ITP • Patients who fail splenectomy or relapse after an initial response should be investigated for accessory splenic tissue. • A peripheral smear and magnetic resonance imaging (MRI) or nuclear medicine studies with technetium (Tc)-99m–labeled heat-damaged red cells are indicated. • If accessory splenic tissue is found, re-exploration should be considered (N Engl J Med 2002;346:995) Nir Hus

  6. Ventilatory Complications in Burns. • Thermal injury to the airway generally is limited to the oropharynx or glottis. • The glottis generally protects the subglottic airway from heat, unless the patient has been exposed to superheated steam. • Edema formation can compromise the patency of the upper airway, mandating early assessment and constant re-evaluation of the airway. • Gases containing substances that have undergone incomplete combustion (particularly aldehydes), toxic fumes (hydrogen cyanide), and carbon monoxide can cause tracheobronchitis, pneumonitis, and edema. • Mortality may be increased by as much as 20% in these patients. Nir Hus

  7. Ventilatory Complications in Burns. • Carbon monoxide exposure is suggested by a history of exposure in a confined space with symptoms of: • Nausea • Vomiting • Headache • Mental status changes • Cherry-red lips. • Carbon monoxide binds to hemoglobin with an affinity 249 times greater than that of oxygen. • Results in extremely slow dissociation (t1/2 250min) on R.A. Nir Hus

  8. Ventilatory Complications in Burns. • W/ 100% O2 the t1/2 drop to 40 min via N.R. • The arterial carboxyhemoglobin level is obtained as a baseline, and if it is elevated (>5% in nonsmokers or >10% in smokers), oxygen therapy should continue until normal levels are achieved. • The increased ventilation-perfusion gradient and the reduction in peak airway flow in distal airways and alveoli can be evaluated using a xenon-133 ventilation-perfusion lung scan. Nir Hus

  9. Ventilatory Complications in Burns. • Major injuries require endotracheal intubation with a large-bore tube (7.5 to 8 mm) to facilitate pulmonary toilet of viscous secretions and mechanical ventilation with positive pressure. • Decreased pulmonary compliance is often seen after inhalation injury and can lead to iatrogenic ventilator-associated lung injury. • A constricting truncal eschar can limit chest excursion. • Escharotomies can be used to relieve the constriction and allow adequate tidal volumes. • This need becomes evident in a patient maintained on a volume control ventilator whose peak airway pressures increase. Nir Hus

  10. Characteristics Lithogenic Bile • The primary bile salts are: • Cholate • Chenodeoxycholate • Synthesized in the liver by cholesterol. • They are conjugated in the liver with taurine and glycine. • 95% of the bile acid pool is reabsorbed and returned through the enterohepatic system to the liver. • The remaining 5% is excreted in the stool. Nir Hus

  11. Characteristics Lithogenic Bile • Cholesterol and phospholipids synthesized in the liver are the principal lipids found in bile. • Active NaCl transport by the gallbladder epithelium is the driving force for the concentration of bile. Water is passively absorbed. • The concentration of bile may affect the solubility of two important components of gallstones: calcium and cholesterol. • Concentrating bile results in an increased tendency for cholesterol nucleation. Nir Hus

  12. Characteristics Lithogenic Bile • The key to maintaining cholesterol in solution is the formation of micelles, a bile salt–phospholipid-cholesterol complex, and cholesterol-phospholipid vesicles. • In states of excess cholesterol production, these large vesicles may also exceed their capability to transport cholesterol, and crystal precipitation may occur. • but the cholesterol-phospholipid vesicles carry the majority of biliary cholesterol. Nir Hus

  13. Characteristics Lithogenic Bile • Pigment stones contain less than 20% cholesterol and are dark owing to the presence of calcium bilirubinate. • Black pigment stones (due to unconjugated bilirubin) are small and tarry, and are frequently associated with hemolytic conditions such as hereditary spherocytosis and sickle cell disease or cirrhosis. • Not associated with infected bile. • Located almost exclusively in the gallbladder Nir Hus

  14. Characteristics Lithogenic Bile • Brown pigment stones are soft and earthy in texture and are typically found in bile ducts, especially in Asian populations. • Contain more cholesterol and calcium palmitate and occur as primary common duct stones in Western patients with disorders of biliary motility and associated bacterial infection. • E. colisecrete β-glucuronidase that causes enzymatic hydrolysis of soluble conjugated bilirubin glucuronide to produce insoluble free bilirubin, which then precipitates with calcium. Nir Hus

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