HYPOXIA AND ASPHYXIA DUE TO POISONING

v  HYPOXIA IS A CONDITION IN WHICH THE BODY OR A REGION OF THE BODY IS              DEPRIVED OF ADEQUATE OXYGEN SUPPLY AT THE TISSUE LEVEL.

  v  ASPHYXIA IS A CONDITION ARISING WHEN THE BODY IS DEPRIVED OF OXYGEN, CAUSING UNCONSCIOUSNESS OR DEATH.

Poisoning is an act of causing disturbances to organisms when subjected to a sufficient amount of poison as lead, mercury, carbon monoxide, cyanide, and so on. When inhaled, poisoning effects are catastrophic due to their disruption the physiologic function of heme proteins which are essential for oxidative metabolism with their role of maintaining a supply of oxygen.

DAILY LIFE EXAMPLE

·         Carbon Monoxide (CO) poisoning

·         Cyanide (CN-) poisoning

CARBON MONOXIDE (CO) POISONING

Carbon monoxide (CO) is a colorless, odorless, toxic gas that is a product of incomplete combustion. Motor vehicles, heaters, appliances that use carbon-based fuels, and household fires are the main sources of this poison. Carbon monoxide (CO) intoxication is one of the leading causes of death due to poisoning. CO poisoning is also the most common cause of death in combustion-related inhalation injury, especially for poor families burning coal in stoves or using natural gas heaters, but closing their fresh air ventilation windows due to energy-saving purpose.

Possible mechanisms of toxicity include a decrease in the oxygen-carrying capacity of blood due to CO binding to heme proteins. CO combines preferentially with hemoglobin to produce carboxyhemoglobin (COHb), displacing oxygen, and reducing systemic arterial oxygen (O2) content. CO binds reversibly to hemoglobin with an affinity 200–230 times that of oxygen. Consequently, relatively minute concentrations of the gas in the environment can result in toxic concentrations in human blood. The net result is a hemoglobin molecule that is poorly equipped to release oxygen at the tissue level. The decreased oxygen delivery is then sensed centrally, stimulating ventilatory efforts and increasing minute ventilation. The latter will increase uptake of CO and raise COHb levels and will result in respiratory alkalosis and hypoxia and asphyxia eventually.

CYANIDE (CN-) POISONING

Cyanide has been widely used as an essential raw material in several industries including textile, plastics, paints, photography, electroplating, agriculture, food, medicine, and mining/metallurgy. Because of its high affinity for gold and silver, cyanide is able to selectively leach these metals from ores. Especially, in gold mining processes, cyanide use has potentially poisonous consequences due to its high volatility at low pH values. At an optimal gold extraction pH of 10.5 or greater, most of the free cyanide in the solution is in the form of the cyanide anion (CN-), where cyanide loss by volatilization is limited. In natural aqueous systems that have pH values between 5 and 8.5, the majority of free cyanide can be found in the form of HCN and can be lost by volatilization. When cyanide vapor is inhaled up to critical levels, it causes intracellular hypoxia by reversibly binding to heme proteins with the same mechanism CO does.