Table 1.
Causes and types of cerebral hypoxia
| CBF | PtiO2 | LPR | OEF | Pathophysiology | |
|---|---|---|---|---|---|
| Ischemic | ↓ | ↓ | ↑ | ↑ | Inadequate CBF |
| Low extraction | ≅ | ↓ | ↑ | ≅ | Low arterial partial pressure of oxygen, PaO2 (hypoxemic hypoxia) |
| Low hemoglobin concentration (anemic hypoxia) | |||||
| Low half-saturation pressure P50 (high- affinity hypoxia) | |||||
| Shunt | ↑ | ≅ | ↑ | ↓ | Arteriovenous shunting (microvascular shunt) |
| Diffusion | ≅ | ≅ | ↑ | ↓ | Diffusion barrier (intracellular or interstitial edema) |
| Uncoupling | ≅ | ≅ | ↑ | ↓ | Mitochondrial dysfunction |
| Hypermetabolic | ↑ | ↓ | ↑ | ↑ | Increased demand |
CBF: cerebral blood flow; PtiO2: brain oxygen pressure; LPR: lactate/pyruvate ratio; OEF: oxygen extraction fraction