Oxygen respiratory metabolism development

The bacteria of the two genera Acetobacter and Gluconobacter are obligatory aerobic microorganisms with an exclusively respiratory metabolism. Their growth, at the expense of substrates that they oxidize, is therefore determined by the presence of dissolved oxygen in the environment. All of these species develop on the surface of liquid media and form a halo or haze, less often a cloudiness and a deposit. 

Paraquat, although restricted from use in Western countries, is a highly toxic herbicide that is still readily available in developing tropical countries. Upon intake, paraquat is rapidly metabolized in the liver and the lungs with the production of secondary oxygen radicals. It is these radicals that cause injury to tissues and especially do so to the lungs. Poisoned animals die acutely of respiratory failure. 

The muscle damage associated with the trauma of surgery wfll increase the serum activity of enzymes originating in skeletal muscle, and this increased activity may persist for several days. Typical alterations in activity of serum enzymes following surgery are illustrated in Table 17-13. Increased tissue catabolism requires increased oxygen consumption and also leads to the production of acid metabofites. Thus blood lactate may increase twofold to threefold. With tissue anoxia and impairment of renal and respiratory function, a metabolic acidosis develops. With tissue destruction, there is increased urinary excretion of the major biochemical components of skeletal muscle. 

Mixed respiratory and metabolic acidosis may develop in patients with cardiorespiratory arrest, in those with chronic lung disease who are in shock, and in metabolic acidosis patients who develop respiratory failure. This mixed disorder should be treated by responding to both the respiratory and metabolic acidosis. Improved oxygen delivery must be initiated to improve hypercarbia and hypoxia. Mechanical ventilation may be needed to reduce PaC02. During the initial stage of therapy, appropriate amounts of alkali should be given to reverse the metabolic acidosis (see section on treatment of metabolic acidosis earlier in this chapter). 

Frequent measurement of blood gases, that is, oxygen partial pressure (PO2), carbon dioxide partial pressure (PCO2), and pH, is essential to clinical diagnosis and management of respiratory and metabolic problems in the operating room and the ICU. Considerable effort has been devoted over the last two decades to developing disposable extracorporeal and in particular intravascular fiber optic sensors that can be used to provide continuous information on the acid-base status of a patient. 

The overall effect of these cellular and systemic actions is to stimulate respiratory and other enzyme synthesis, which results in increased oxygen consumption and resultant increased basal metabolic rate. This affects heart rate, respiratory rate, mobilization of carbohydrates, cholesterol metabolism, and a wide variety of other physiological activities. In addition, thyroid hormones stimulate growth and development and, as noted earlier, are critical for the normal proliferation, growth, and development of brain cells. Table 2 shows the estimated iodine concentration in selected organs. 

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