Topic: Fluid Dynamics
Next Unit: Hypovolemic Response Via ADH
5 minute read
EDEMA: a palpable swelling produced by expansion of the interstitial fluid volume. Edema is abnormal. It is not found in normal subjects, because fluid collecting in the tissues of the body is caused by an alteration in capillary dynamics that favors not only an increase in net filtration, but also inadequate removal of the additional filtered fluid by lymphatic drainage.
In edema, the abnormal condition of excess fluid accumulates in the interstitium due to
- increased capillary hydrostatic pressure (blood pressure) due to venous obstruction (like inflammation, hepatic obstruction,
- tight clothing around the extremity or prolonged standing),
- salt and water retention (from CHF, renal failure, or liver cirrhosis), and/or
- lymphatic obstruction by inflammation or tumors.
GENERALIZED EDEMA: is the distribution of fluid in interstitial spaces, like dependent edema (feet, legs, buttocks) and pitting pedal edema (ability to create a finger-crater by pushing, found in CHF patients).
CLINICAL MANISFESTATIONS are either
- local or
Local manifestations include sites of trauma, organ systems (e.g., cerebral, pulmonary, or laryngeal edema). Edema in the brain, lungs, or larynx is life-threatening.
When fluid accumulates during edema, nutrients and waste product movement slow down, blood flow is impaired, and wounds heal more slowly. Dehydration is also a primary concern, and there can be infection and pressure sores over any bony areas.
PITTING EDEMA: Graded 1-4, the number corresponding to the time the edema stays pitted after pressure is removed. (2 would be about 15 seconds.)
LYMPHEDEMA: an accumulation of excess fluid in the lymphatic spaces, usually due to surgical interruption of the lymphatic vessels (lymph node excision in cancer surgery) or blockage of lymphatics by the tumors themselves. Radiation can also destroy the continuity of the lymphatics, causing lymphedema. It is usually localized in a single limb.
Treatment for generalized edema (pitting/dependent edema) includes
- elevating edematous limbs,
- compression stockings,
- reduction of salt intake,
- diuretics, and
- IV albumin for severe cases.