Hypoxia Classifications Flashcards

Hypoxic Hypoxia

• Caused by reduced oxygen (O2) in inspired air or decreased partial pressure of O2 in alveoli; may also include issues with O2 transfer to the bloodstream.
• Common causes include high altitude, hypoventilation, diffusion abnormalities, pulmonary shunting, and ventilation/perfusion (V/Q) mismatch.
• Blood gas values show decreased PaO2, SaO2, CaO2, and PvO2; correctable by increasing FiO2 and PEEP.

Anemic Hypoxia

• Characterized by abnormally low O2 content due to reduced hemoglobin (Hgb) or Hgb's inability to carry O2 effectively.
• Causes include carbon monoxide poisoning, anemia or blood loss, and methemoglobinemia.
• Blood gas values present normal PaO2 but decreased CaO2, PvO2, and SvO2; treatment includes increased FiO2 and packed red blood cells if Hgb is critically low.

Stagnant or Circulatory Hypoxia

• Results from decreased cardiac output or reduced circulation of oxygenated blood to tissues; elevated metabolic needs drive greater O2 extraction from the limited blood supply.
• Causes involve shock, hypovolemia, cardiac failure, and anatomical shunting; treatment may necessitate fluids, vasopressors, cardiac drugs, surgical repairs, and supplemental oxygen.
• Blood gas values reflect normal PaO2 and CaO2 but decreased DO2, PvO2, SvO2, and CvO2, coupled with increased arteriovenous oxygen difference (a-vDO2).

Histotoxic Hypoxia

• The inability of tissues to metabolize O2 adequately despite normal partial pressure and delivery; tied to cellular or mitochondrial dysfunction.
• Associated with sepsis (leading to mitochondrial damage) and cyanide poisoning (direct destruction of mitochondria).
• Initially normal arterial blood gas (ABG) readings; characterized by decreased O2 consumption, increased PvO2, SvO2, and CvO2 with diminished a-vDO2.
• Treatment focuses on maximizing oxygen delivery, managing sepsis with antibiotics, and stabilizing hemodynamic function.

Cyanosis

• Visual indication of low oxygen saturation characterized by blue-gray or purplish discoloration, particularly in mucus membranes and extremities.
• Occurs when blood contains more than 5g% hemoglobin that is disassociated from oxygen; calculated by example (Hb = 15g%, Sat% = 60; results in a cyanotic state).

Polycythemia

• Increased red blood cell (RBC) levels arise from chronic hypoxemia due to erythropoietin stimulation of bone marrow.
• Enhances oxygen-carrying capacity; however, hematocrit levels reaching 55-60% increase blood viscosity, posing work strain on the heart and resulting in left and right ventricle hypertrophy.