Unit 4 - Edema Flashcards
what is edema defined as?
palpable swelling produced by expansion of interstitial fluid volume
-can be diffuse or localized
when does edema become clinically apparent?
not until interstitial volume has increased by at least 2.5 to 3 L
what is the pathophysiology of edema formation?
2 basic steps
- alteration in capillary hemodynamics favoring movement of fluid from vascular space into interstitium
- retention of dietary or intravenously-administered Na and water by kidneys
why doesn’t hemoconcentration and shock occur in edema?
some of the fluid stays in vascular space instead of going to interstitium, helping to return plasma volume toward normal
- change in capillary hemodynamics results in most of retained fluid to return to interstitium –> edema
- thus the net effect is appropriate expansion of total EC volume (as edema) with maintenance of plasma volume closer to normal levels, to restore tissue perfusion
what are the possible causes of edema?
- increased capillary hydraulic pressure
- decreased plasma oncotic pressure
- increased capillary permeability
- lymphatic obstruction (lymphedema)
- myxedema
what occurs in increased capillary hydraulic pressure?
increased venous pressure by blood volume expansion
- -heart failure (CHF)
- -renal disease
- -cirrhosis
- -pregnancy
- -constriction/restriction
- -venous obstruction
what occurs in decreased plasma oncotic pressure?
- hypoalbuminemia, malnutrition/malabsorption
- nephrotic syndrome
- decreased hepatic albumin synthesis (liver failure)
what occurs in increased capillary permeability?
- burns
- ARDS w/ sepsis-induced cytokine release increases pulmonary capillary permeability
- malnutrition
- angioedema
what occurs in myxedema?
hypothyroidism
- accumulation of interstitial albumin
- low lymphatic flow
what are compensatory factors to prevent edema?
- lymphatic flow and contractility increase with tissue edema and remove excess filtrate
- fluid entry into interstitium
- -raises interstitial hydraulic pressure, reducing pressure gradient that favors filtration
- -lowers interstitial oncotic pressure, by dilution and lymphatic mediated removal of interstitial proteins
what are the most common causes of generalized edema?
- heart failure
- cirrhosis
- nephrotic syndrome and other renal diseases
- premenstrual edema and pregnancy
- anemia
what is pertinent history if there is peripheral edema?
- right-sided heart failure
- pericardial disease
- renal disease (malaise, nausea, weight loss)
- local venous or lymphatic disease
what is pertinent history if there is ascites?
- cirrhosis
- weight gain
- increased abdominal girth
- gynecomastia
- spider angiomata/telangiectasia
what is intermittent edema commonly caused by?
premenstrual symptom
what history should you be aware of for all edema?
- any disorder (CAD, HTN, alcohol abuse)
- medications that can cause cardiac, hepatic, renal disease