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Pulmonary Thromboembolism

Pulmonary Thromboembolism. Emily S. Southward DVM University of Missouri – Columbia Veterinary Medical Teaching Hospital. Definition. Pulmonary thromboembolism One clot or many clots that form at distant sites and lodge in the pulmonary vasculature. Pulmonary artery thrombus

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Pulmonary Thromboembolism

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  1. Pulmonary Thromboembolism Emily S. Southward DVM University of Missouri – Columbia Veterinary Medical Teaching Hospital

  2. Definition • Pulmonary thromboembolism • One clot or many clots that form at distant sites and lodge in the pulmonary vasculature. • Pulmonary artery thrombus • Clots that form in the pulmonary vasculature. • Clots can partially or fully occlude pulmonary vessels.

  3. Virchow’s Triad • Venous stasis. • Injury or abnormalities to the vessel wall. • Alterations in coagulation properties.

  4. Venous Stasis • Accumlation of activated procoagulants. • Immobilization • Inadequate cardiac pump. • Promotes thrombus formation.

  5. Vessel Wall Injury • Acute or chronic injury to vessel endothelium. • Leads to activation of platelets and clotting cascade. • Promotes thrombus formation.

  6. Vessel Injury

  7. Platelet Adhesion

  8. Aggregation

  9. Alternations in Coagulation • Increase in procoagulant factors. • By trauma to vascular wall or extravascular tissues. • Releases tissue thromboplastin and phospholipid. • Leads to formation of prothrombin activator. • Prothrombin  Thrombin

  10. Alterations in Coagulation • Decrease in anticoagulant factors. • Thrombomodulin • Antithrombin III • Heparin • Alpha2-Marcoglobulin • Plasmin • Leads to hypercoagulable state by formation of thrombin.

  11. Thrombosis Formation • Platelet nidus at site of injury. • Growth by aggregation of platelets and fibrin. • Activation of clotting cascade. • Larger growth to a red fibrin thrombus. • Thrombus fractures and embolizes to other areas of the body.

  12. Predisposing Factors or Diseases for Development of PTE • Hypercoagulable state • Nephrotic syndrome • Immobilization • Amyloidosis • Early DIC • Hyperadrenocorticism • Capillary fragility • Activation of clotting cascade.

  13. Predisposing Factors or Diseases for Development of PTE • Hypercoagulable state • Capillary fragility • Diabetes Mellitus • Immune–mediated hemolyitc anemia • Sepsis • Hyperadrenocorticism • Activation of clotting cascade.

  14. Predisposing Factors or Diseases for Development of PTE • Hypercoagulable state • Capillary fragility • Activation of clotting cascade. • Sepsis • Pneumonia/pyothorax • Heartworm disease • Surgery • Bacterial endocarditis • Neoplasia

  15. Consequences of PTE • Respiratory. • Increased alveolar dead space. • Hyperventilation. • Hypoxemia. • Ventilation/perfusion inequality. • Intrapulmonary shunts.

  16. Normal Alveolus

  17. Increased Alveolar Dead Space

  18. Hypoxemia • Results from ventilation-perfusion inequality, physiologic shunting and increased dead space.

  19. Intrapulmonary Shunts • Blood that has not been to areas of ventilated lung and enters systemic circulation without gas exchange taking place. • Poorly oxygenated blood enters the arterial system lowering the PaO2. • Not responsive to oxygen therapy.

  20. Ventilation/Perfusion Inequality • V/Q inequality occurs when distribution of blood is altered to the alveoli. • O2 increase in the alveoli and CO2 decreases.

  21. Hemodynamic Changes • Increase in pulmonary vascular resistance. • Increased afterload to the right heart. • Can lead to circulatory collapse and shock.

  22. Clinical Signs • Not pathognomonic. • Dyspnea. • Tachypnea. • Hemoptysis. • Tachycardia. • Hypoxemia. • Sudden death.

  23. Diagnosis • CBC/Biochemistry results reflect primary disease process. • Hypoxemia common but 10% of patients are normal. • Thoracic radiographs can be normal and inconclusive.

  24. LaRue MJ and Murtaugh RJ. Pulmonary Thromboembolism in Dogs:47 cases (1986-87). J Amer Vet Med Assoc. 1990 Nov. 15;197(1):1368-1372. • Johnson LR et al. Pulmonary Thromboembolism in 29 dogs:1985-1995 J Vet Intern Med. 1999 Jul;13(4):338-345. • Flükiger MA and Gomez JA. Radiographic Findings in Dogs with Spontaneous Pulmonary Thrombosis or Embolism. Veterinary Radiology, Vol.25,No.3 124-131.

  25. Advanced Diagnostics • Pulmonary scintigraphy • Pulmonary angiography.

  26. Pulmonary Scintigraphy • Noninvasive • Aids in diagnosis of PTE but not definitive. • Two types- ventilation and perfusion scans.

  27. Performed first. Normal study rules out PTE. Radionuclide-labelled, macroaggregated albumin in peripheral vein. Perfusion Scan

  28. Inhaled radioactive inert gas-senon-133 or technetium-99m. Patient under general anesthesia. Normal in PTE. Ventilation Scan

  29. With PTE the ventilation scan would be normal and the perfusion scan abnormal. Suggestive of PTE.F Picture from WWW.bschsys.org/DiagnositcImaging/nucmd/htm Ventilation/Perfusion Combo

  30. Normal Human Perfusion Scan

  31. Abnormal Human Perfusion Scan

  32. Pulmonary Angiography • Performed if definitive diagnosis or exclusion of PTE is required. • Requires sedation or general anesthesia. • Greater risks. • Intraluminal filling defect and sharp cutoff are diagnostic for PTE.

  33. Human lung. Arrow indicates abrupt termination of a pulmonary artery. Www.brighamrad.Harvard.edu/cases/bwh/images. Pulmonary Embolus

  34. Treatment • Oxygen therapy. • Heparinization 200-300 units/kg subcutaneously every 8 hours. • Streptokinase or TPA. • Mechanical ventilation. • Long term- warfarin therapy.

  35. Monitoring • Clotting times- want to maintain PTT at 1.5-2.5 times normal or and ACT at 1.2-1.4 times normal. • Serial arterial blood gas analysis. • Respiratory rate. • Central venous pressure. • All other basic monitoring.

  36. Complications Of Therapy • Hemorrhage most common. • Not predictable. • Protamine therapy indicated with hemorrhage due to heparin. • Vitamin K or fresh-frozen plasma in warfarin therapy.

  37. Prognosis • Guarded. • Improves with early detection and treatment. • Improves each day the patient survives. • At risk for more emboli.

  38. UMC VMTH Cases • Three in data base. • Sadie • Magnum • Koko

  39. Sadie Bailey • 8-year-old FS mixed breed dog. • Presented for weight loss, anemia, and anorexia. • Weak and lethargic on presentation • Hemoabdomen, thrombocytopenia, and neutrophilia with left shift. • Developed severe dyspnea and ventricular tachycardia.

  40. Sadie’s Thoracic Films

  41. Sadie’s Thoracic Films

  42. Sadie’s Necropsy • Hepatocellular carcinoma • Adrenocortical hyperplasia • Pulmonary thrombois – most lobar branches effected. • Renal infarction.

  43. Magnum Meeks • 8-year-old MC doberman pinscher • Presented for dyspnea of two days duration. • Protein losing nephropathy.

  44. Magnum’s Thoracic Films

  45. Magnum’s Thoracic Films

  46. Koko Westerhoff • 12-year-old FS dachshund. • Presented for lethargy, anorexia, tachypnea, and possible CHF. • History includes diabetes mellitus, IVDD and cataracts. • PE- Increased BV lung sounds, mild crackles, tachycardia, and left systolic murmur.

  47. Koko’s Thoracic Films

  48. Koko’s Thoracic Films

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