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**Overloading in excessive fluid therapy
**Overloading in excessive fluid therapy
**As part of inflammatory process
**As part of inflammatory process
* In the normal state, pulmonary alveoli are kept dry by three mechanisms:
*# Normal "push-pull" mechanism at capillary level.
*# Efficient lymphatic drainage by rhythmic pumping action near airways.
*# Integrity of the alveolar epithelial basement membrane is relatively impermeable.
*#* Unlike the capillary basement membrane, which is relatively permeable.
=====Pathogenesis=====
# The pumping efficiency of the lymphatics is exceeded.
# Fluid accumulates in connective tissue adjacent to airways.
# The alveolar walls fill with fluid.
# The alveoli abruptly and severely fill with fluid.
#* Associated with the disintegration of alveolar epithelial junctional complexes.
=====Haemodynamic type=====
* Fluid leaks into alveoli via junctional complexes BUT the alveolar basement membrane remains intact.
** I.e. is due to elevated pulmonary venous pressure.
* Potentially reversible.
* Causes:
*# '''Cardiogenic'''
*#* Usually left ventricular failure.
*#* Also occurs with cardiac overload due to valvular disease.
*# '''Mechanical'''
*#* Large primary pulmonary tumours.
*#* Severe metastatic disease.
*#* Granulomatous infections may raise pulmonary venous pressure.
*# '''Neurogenic'''
*#* Seizures or CNS disorder.
*#* Rare in domestic species.
=====Permeability type=====
* Fluid fills the alveoli following damage to cells or junctional complexes, or permanent ionic alteration of the alveolar basement membrane.
* Irreversible.
* Causes:
*# '''Toxins'''
*#* Bacterial
*#** [[:Category:Pseudomonas and Burkholderia species|''Pseudomonas'']]
*#** [[:Category:Pasteurella and Mannheimia species|''Pasteurella'']]
*#** [[:Category:Staphylococcus species|''Staphylococcus'']]
*#* Chemical
*#** Paraquat.
*# '''Aspiration/inhalation'''
*#* Gastric contents (low pH)
*#* Smoke.
*#* Excess ozone.
*#* Oxygen.
* There may be a combination of haemodynamic and permeability types in electrocution syndromes and "shock" lung.
** E.g. in Adult Respiratory Distress Syndrome (ARDS).
[[Category:Circulatory Disorders - Pathology]]
[[Category:To Do - Respiratory]]
[[Category:To Do - Respiratory]]
[[Category:Respiratory Diseases - Horse]]
[[Category:Respiratory Diseases - Horse]]