43. Arterial oxygen content:
CaO2 = (1.34 x Hb x SaO2) + (0.0031 x PaO2)
Mixed venous oxygen content:
CvO2 = (1.34 x Hb x SvO2) + (0.0031 x PvO2)
Oxygen delivery: DO2 (mL/min) = Q x
CaO2
Normal: 500 mL/min/m2
Oxygen consumption:
VO2 = Q x (CaO2 - CvO2)
Oxygen extraction:
O2 Extraction Ratio = (CaO2 - CvO2)/CaO2
Normal: 25 - 30%
44. Tissue hypoxia: How to
detect
Clinical Assessment:
no specific clinical signs of tissue
hypoxia,
a number of well-known signs (mental
obtundation, decreased urine output,
abnormal vital signs, etc) often indicate
specific organ dysfunction, a common
late sequela of tissue hypoxia
45. Tissue hypoxia: How to detect
pH and lactate
hypoxic
nonhypoxic causes (eg, delayed clearance of
lactate, accelerated aerobic glycolysis, and
dysfunction of pyruvate dehydrogenase)
Plasma lactate:
- good prognostic indicator.
- Plasma lactate: easy to measure and can be followed
sequentially to assess prognosis or the patient's response
to therapy
46. Treatment of tissue hypoxia
increased DO2 in patients with evidence of
tissue hypoxia.
the first step:
maximize arterial oxygen content by
increasing Hb & SaO2
SaO2 ≥ 97%
the next step is to augment the cardiac
output.