Excretion of bicarbonate

The answer is c. (Hardman, pp 6917 693 J Acetazolamide is a carbonic anhydrase inhibitor with its primary site of action at the proximal tubule of the nephron. Acetazolamide promotes a urinary excretion of Na, K, and bicarbonate There is a decrease in loss of Cl ions The increased excretion of bicarbonate makes the urine alkaline and may produce metabolic acidosis as a consequence of the loss of bicarbonate from the blood. None of the other diuretic drugs promote a reduction in the excretion of the Cl ion... 

The excessive amount of bicarbonate in the blood means that blood has a much greater capacity to neutralize acids. Many acids accumulate in the blood during strenuous activity, for example lactic acid. Excretion of bicarbonate through the kidneys and the removal of carbon dioxide through respiration also regulate the carbonic acid/ bicarbonate blood buffer. 

Metabolic acidosis follows, and an increased anion gap results from accumulation of lactate as well as excretion of bicarbonate by the kidney to compensate for respiratory alkalosis. Arterial blood gas testing often reveals this mixed respiratory alkalosis and metabolic acidosis. Body temperature may be elevated owing to uncoupling of oxidative phosphorylation. Severe hyperthermia may occur in serious cases. Vomiting and hyperpnea as well as hyperthermia contribute to fluid loss and dehydration. With very severe poisoning, profound metabolic acidosis, seizures, coma. 

The blood pH may return to normal in adults with mild overdoses. However, the blood pH can drop too far in children or more severely poisoned adults, resulting in metabolic acidosis. A lower buffering capacity or plasma protein-binding capacity may underlie the increased susceptibility to acidosis in children. Excretion of bicarbonate also means the bicarbonate in the blood is lower, and hence, there is an increased likelihood of metabolic acidosis. 

As well as the increased excretion of bicarbonate, Na+ and K+ excretions are also increased. Because of the solute load, water excretion also increases. This results in hypokalemia and dehydration. 

In patients with adequate renal function, urinary pH values are usually increased because of the decreased excretion of acid and increased excretion of bicarbonate. Urinary ammonia values are decreased because of decreased formation of ammonia in the tubules. In K depletion, is preferentially exchanged for Na and the pH of the urine may be low. This is called paradoxical aciduria. 

Metabolic acidosis can also result from loss of bicarbonate, such as in severe diarrhea, especially in infants or due to the depletion of bicarbonate when urine is delivered to the colon after transplantation of ureters into the colon. The administration of carbonic anhydrase inhibitors such as acetazolamide results in excretion of bicarbonate in urine and retention of hydrogen ions, leading to metabolic acidosis. Because of impaired hydrogen ion secretion potassium is... 

Mild hyperventilation occurs from early pregnancy, probably due to a centrally mediated effect of progesterone, and PCO. falls. However, blood hydrogen ion concentration is maintained within non-pregnant limits, since the plasma bicarbonate falls due to an increased renal excretion of bicarbonate. Oxygen consumption increa.scs by about 2091, but PO, is relatively unchanged. 

This drug is a weak diuretic. In addition, it is useful in the therapy of glaucoma, as it reduces the formation of water in the ocular fluid. It is also useful in the therapy of metabolic alkalosis. Additionally, carbonic anhydrase inhibitors may also be useful in the therapy of hypooxygena-tion ( mountain sickness ), because they decrease alkalinization of the blood by increased excretion of bicarbonate, and in some types of seizures. 

This drug is reabsorbed in an alkaline kidney. Thus, if the urine is basic, the half-life increases. Recall that acetazolamide administration results in the excretion of bicarbonate and alkaline urine. The plasma half-life of diethylcarbamazine is increased, as a result of the alkalinization of the urine and increased reabsorption. 

The bicarbonate ion (HCO3A is the second-largest anionic contributor to maintaining acid-base balance, and its secretion from the pancreas helps to neutralize the contents of the small intestine. Respiration controlling the carbon dioxide concentration of the blood (PaCOj) and renal excretion of bicarbonate are the two main homeostatic influences on plasma bicarbonate. Within the renal tubular lumen, carbonic anhydrase converts carbonic acid into carbon dioxide, which diffuses into the epithelial cells and forms carbonic acid, which later dissociates to bicarbonate. 

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-... 

Sulfamylon impairs the renal mechanism involved in the bnflfering of the blood, thereby increasing the excretion of bicarbonate in the urine. When this occurs, the pulmonary system effects a... 

Inhibition of sodium-hydrogen exchange in the proximal tubules resulting in the inhibition of hydrogen ion secretion and enhanced excretion of bicarbonate. 

The thiazide diuretics (and triamterene) can cause calcium retention by reducing its urinary excretion. This, added to the increased intake of calcium, resulted in excessive calcium levels. Alkalosis (the milk-alkali syndrome, associated with hypercalcaemia, alkalosis, and renal impairment) may also occur in some individuals because the thiazide limits the excretion of bicarbonate. 

In rats orally administered single doses of 50 or 100 mg/ kg of water or ethanol extracts of pill-bearing spurge daily, a time-dependent increase in urine output was observed. The water extract increased the urine excretion of sodium, potassium, and bicarbonate. In contrast, the ethanol extract increased the excretion of bicarbonate, decreased the loss of potassium, and had little effect on renal removal of sodium. The activity of pill-bearing spurge was noted as similar to the drug acetazolamide (Johnson et al. 1999). 

Alkalosis an increase in the pH of body fluids. It is corrected by excretion of bicarbonate and retention of acid. There 2 types ... 

The primary conditions that result in decreased renal excretion of acids and a buildup of metabolic acids are renal disease and renal failure. Additionally, renal disease can result in excessive excretion of bicarbonate. The loss of bicarbonate through diarrhea or overuse of laxative, decreased production of bicarbonate, or ingestion of excessive acid such as acidic poisons, iron, or aspirin could cause metabolic acidosis. 

Metabolic alkalosis occurs when there is an excess of bicarbonate in the blood owing to increased intake, retention of bicarbonate, or loss of metabolic acids. Bicarbonate is regulated by the kidneys, and any situations that decreases renal excretion of bicarbonate will result in an alkalotic state. 

Regulating acid-base balance through retention or excretion of bicarbonate... 

Not only is the concentration of carbon dioxide under physiological control, so also is the concentration of the other component of the buffer pair, the bicarbonate. This is controlled in the kidney, which may increase or decrease the excretion of bicarbonate as components of physiological control mechanisms. Since both components of the buffer pair are under physiological control, it is possible for the C02-bicarbonate system to act as a perfect buffer and completely to restore the pH of the internal environment to normal. Examples of such contributions will appear repeatedly as the subject of acid-base physiology unfolds. 

D. Compensation of respiratory acidosis involves increased renal excretion of bicarbonate ions. 

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