Acid-base balance respiratory

For Further Reading J. A. Kraut and N. E. Madias, Approach to patients with acid—base disorders, Respiratory Care, vol. 46, no. 4, April 2001, pp. 392—403. J. Squires, Artificial blood, Science, vol. 295, Feb. 8, 2002, pp. 1002-1005. Lynn Taylor and Norman P. Curthoys, Glutamine metabolism Role in Acid-Base Balance, Biochemistry and Molecular Biology Education, vol. 32, no. 5, 2004, pp. 291-304. 

Like ketoacidosis, respiratory acidosis can also upset the acid-base balance in the body. Respiratory acidosis occurs when the lungs cannot remove enough carbon dioxide from the body. This may be due to severe lung diseases such as chronic asthma, emphysema, or bronchitis, or it could be caused by mechanical restrictions to the emptying of the lung due to scoliosis (curvature of the spine) or severe obesity. 

Along with the respiratory system, the renal system maintains acid-base balance by altering the excretion of hydrogen and bicarbonate ions in the urine. When the extracellular fluid becomes acidic and pH decreases, the... 

Metabolic or respiratory acidosis Cautiously institute amiloride in severely ill patients in whom respiratory or metabolic acidosis may occur, such as patients with cardiopulmonary disease or poorly controlled diabetes. Monitor acid-base balance frequently. Shifts in acid-base balance alter the ratio of extracellular/intracellular potassium the development of acidosis may be associated with rapid increases in serum potassium. 

It is not yet clear which estimates of the ratio between the levels of protein and of carbohydrate metabolism during hypoxia should be regarded as reliable. It seems likely that the increase in respiratory quotient in freshwater fish to values of 2.5-2.8, as found by Mohamed and Kutty (1983a, 1986), indicates a predominance of protein expenditure over that of carbohydrate. A hypoxic environment shifts the acid-base balance of the fish towards acidosis (Kotsar, 1976), thereby inducing the redistribution of electrolytes, alteration of ion exchange and the activity of Na+-K+-Mg2+-ATPases and alkaline phosphatases. It also leads to an increased level of C02 in the blood, which enhances the bicarbonate buffer system (Kotsar, 1976). In section 2.1, we... 

In the majority of cases, a UCD can be distinguished from other inborn errors of metabolism by routinely available clinical chemistry tests such as blood gases, acid/base balance, plasma glucose, ammonium, or lactate. Urea production, and hence serum urea nitrogen, is decreased in UCDs. Respiratory alkalosis has few causes and is an important diagnostic clue of hyperammonemia that should trigger measurement of plasma ammonium. 

Factors that regulate distal tubular secretion of are intalce of Na" and K, plasma concentration of mineralocor-ticoids, and acid-base balance. Because renal conservation mechanisms are slow to respond, depletion can be an early consequence of restricted intake or losses of K by extrarenal routes. Diminished glomerular filtration rate is typical of renal failure, and the consequent decrease in distal tubular flow rate is an important factor in the retention of K seen in chronic renal failure. Renal tubular acidosis and metaboUc and respiratory acidoses and alkaloses also affect renal regulation of excretion. These topics are discussed in much greater detail in Chapters 45 and 46. 

Respiratory Mechanism in the Regulation of Acid-Base Balance... 

These disorders are classified according to their cause and the direction of the pH change into respiratory acidosis, metabolic acidosis, respiratory alkalosis, or metabolic alkalosis. Any derangement of acid-base balance elicits... 

Cellular metabolism results in the production of large quantities of hydrogen that need to be excreted in order to maintain acid-base balance. In addition, small amounts of acid and alkali are also presented to the body through the diet. The bulk of acid production is in the form of CO2, from the metabolism of carbohydrates, proteins, and lipids. When respiratory function is normal, the amount of CO2 produced metabolically is equal to the amount lost by respiration, and the blood CO2 concentration remains constant. The average adult produces approximately 15,000 mmol of CO2 each day from the catabolism of carbohydrate, protein, and fat. ... 

The low carbon dioxide level and the high pH while on the respirator were unexpected. These levels led the physician to check the settings on the respirator. The volume adjustment on the respirator had slipped. The patient was receiving twice the recommended quantity of air. This caused respiratory alkalosis, a condition of decreased acidity of the blood and tissues. When the respirator was adjusted, the blood levels returned to normal as the acid-base balance was reestablished, and the patient began to recover. 

The study of the acid-base balance showed slight decrease of pC02, which presents an alveoli hyper-ventilation and decrease of HC03 - indicator of respiratory alkalosis. However, the pH stays the same throughout the experiment. As a whole after the application of HI-6 there are no statistically considerable deviations in the researched parameters [9,10],... 

Respiratory alkalosis is much less common than acidosis but can occur when respiration is stimulated or is no longer subjcci to feedback control (Fig. 4). Usually these are acute conditions, and there is no renal compensation. The treatment is to inhibit or remove the cause of the hyperventilation, and the acid-base balance should return to normal. Examples are ... 

The basic function of the respiratory system is to maintain the respiratory gases, oxygen and carbon dioxide at levels which meet the demands of the metabolic processes and maintain the body acid-base balance. This is achieved through the regulation of ventilation in the lungs and the cardiac output and distribution of blood throughout the body. The levels of ventilation and blood flow, as well as the blood distribution, result from integration of many sensory inputs which may be chemical, mechanical, thermal, and neural in nature. 

Mechanisms of Respiratory Control. To meet the metabolic demands of the body and to maintain the acid-base balance, ventilation is regulated by various stimuli acting at several locations in the body. Although the mechanism by which each stimulus acts in amplifying or diminishing ventilation is not well known, these stimuli clearly inhibit and excite the central respiratory centers in the medulla, either directly or indirectly. The electrical impulses generated in these centers are responsible for the motor activities which produce the ventilatory response. 

Therapeutic doses of salicylate produce definite changes in the acid—base balance and electrolyte pattern. Compensation for the initial event, respiratory alkalosis, is achieved by increased renal excretion of bicarbonate, which is accompanied by increased Na and excretion plasma bicar-... 

The respiratory effects of salicylates contribute to the serious acid—base balance disturbances that characterize poisoning. Salicylates stimulate respiration directly and indirectly. Uncoupling of oxidative phosphorylation leads to increased peripheral CO2 production and a compensatory increase in minute ventilation, usually with no overall change in PCO2. Uncoupling of oxidative phosphorylation also leads to excessive heat production, and salicylate toxicity is associated with hyperthermia, particularly in children. 

Large amounts of acids and smaller amounts of bases normally enter the blood. Some mechanisms must neutralize or eliminate these substances if the blood pH is to remain constant. In practice, a constant pH is maintained by the interactive operation of three systems buffer, respiratory, and urinary. Only when all three parts of this complex mechanism function properly can the acid-base balance be maintained. 

Inadequate respiratory function can result in altered acid-base balance and multiple electrolyte imbalances owing to hypoxemia. 

In spite of the variety and efficiency of the body s mechanisms for maintaining a constant pH, disturbances of acid-base balance can and do occur. They may result from gross dietary imbalance, and also from respiratory, metabolic or renal disorders in which there is either too great a production or a failure of elimination of acid or base. 

Metabolic disorder of acid-base physiology A disorder of acid-base balance not caused by a respiratory disorder. An example is the excess of acid which occurs in uncontrolled diabetes mellitus. 

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