Edema and the Clinical Assessment of Volume Status
  • Disorders of serum sodium are water handling problems
  • Disorders of ECF volume are sodium handling problems

Objectives

List the physical exam findings of Extracellular Fluid (ECF) volume expansion and ECF volume contraction

  • General clinical tests:
    • More invasive testing may be needed:
      • Swan-Ganz catheter (R/L/Pulm cardiac pressure, cardiac output)
      • Central venous pressure monitoring via catheter
    • Biochemical lab tests:
      • BNP
    • Imaging:
      • CXR
      • Echo
      • US of central veins, hepatic and portal veins

Volume expansion

Generalized edema is generally reflective of cardiac, hepatic, or renal diseases

  • General inspection:
    • Air hunger (d/t pulmonary edema): distressed, tachypneic, sitting upright, unable to speak full sentences
  • Vital signs:
    • Renal cause: Hypertension d/t fluid overload
    • Liver/Heart failure: BP normal
  • Respiratory:
    • Pleural effusion: Decreased fremitus, dullness to percussion
    • Interstitial edema: late inspiratory crackles/wheezes
  • CV
    • Valvular heart disease: bounding or other abnormal pulses, murmurs
    • CHF: Apex displaced, third heart sound d/t dilated LV
    • JVP>3-4cm: overload, LV, pulmonary, RV problem or pericardial disease
    • Pitting edema in dependent areas often cardiac, renal or liver disease

Volume contraction

  • General inspection:
    • Dizzy/unsteady, agitated, confused
    • More comfortable lying flat
    • Dry mucus membranes, decrease skin turgor with no edema (check over sternum for old people)
    • Anemia: pallor, pale conjunctiva
    • Look for obvious bleeding, including rectally!
  • Vital signs
    • Weak, thready pulse with cool/clammy extremities
    • Tachycardic (>100bpm)
    • Relative hypotension to baseline, or postural drop in SBP >20mmHg
    • In young people, postural tachycardia may be the only sign due to good compensatory mechanisms
    • JVP may be flat (lower to see)

Caveats

  • It is possible to be overloaded in one compartment, but contracted in another
  • E.g. in CHF, JVP is elevated due to Na retention and back pressure (overloaded), pulmonary circulation is congested leading to pulmonary edema (overloaded), interstitial compartment is expanded leading to pedal edema or ascites or pleural effusions (overloaded), BUT forward flow from LV is impaired so there is contraction of the intravascular compartments -- low BP, tachycardia, thready pulse etc (which provide stimulus for RAAS and ADH

Describe the concept of total body sodium as it relates to ECF volume status

  • When the ECF is contracted in all compartments, treat with isotonic saline
  • When the ECF is overloaded, treat to remove salt with diuretics/dialysis
  • But, when the interstitium is expanded, but intravascular compartment is contracted, it is a balancing act to make sure not to diurese too much to cause hypoperfusion!
  • When we diurese patients with large ECF (interstitium AND plasma) load, we only take out the plasma volume. But, we are hoping that the interstitial fluid will move into the plasma once diuresis occurs driven by Starling forces. However, it is possible that we take out too much plasma (intravascular) volume, leading to volume depletion for the patient

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