Hypoxia caused toxicity

Cyanide toxicity, overshoot hypotension, and myocardial ischaemia. Hypoxia caused by increased ventilation-perfusion mismatch due to pulmonary vasodilatation and inhibition of hypoxic pulmonary vasoconstriction. Rebound hypertension after discontinuation of SNP infusion. 

Carbon dioxide is a simple asphyxiant that is, it causes toxicity by displacing oxygen from the breathing atmosphere primarily in enclosed spaces and results in hypoxia. It has been postulated that the cause of death in breathing high concentration of carbon dioxide is due to carbon dioxide poisoning and not hypoxia based on a study performed in dogs. 

The other major toxic effect of methanol is the ocular toxicity Although formaldehyde might be formed locally in the retina, this seems unlikely, whereas formate is known to cause experimental ocular toxicity. The mechanism suggested involves inhibition by formate of cytochrome oxidase in the optic nerve. As the optic nerve cells have few mitochondria they are very susceptible to this histotoxic hypoxia . The inhibition will result in a decrease in ATP and hence disruption of optic nerve function. Thus, stasis of axoplasmic flow, axonal swelling, optic disc oedema and loss of function occur. Studies have shown that formate alone will cause toxicity in the absence of acidosis, although this will... 

Finally, the heart has a high metahohc rate and is very susceptible to hypoxia which can be produced from asphyxiating causes given above. Severe hypoxia causes asystolic cardiac arrest secondary to respiratory failure and arrest. This underlines why the early management of respiratory insufficiency following toxic trauma is so important. 

A number of toxic conditions beside hypoosmotic stress and hypoxia/ischemia produce brain edema and the causes may be related to regulation of the aquaporins (see Ch. 34). AQP1 and AQP4 are intensely upregulated in reactive astrocytes in subarachnoid hemorrhage [69], in human glioma and astrocytoma [70] and AQP4 in endothelia and reactive astrocytes in metastatic carcinoma [71,72]. 

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