Uncompensated metabolic acidosis

Lactic acidosis, respiratory dysfunction, uncompensated metabolic alkalosis, hypocalcemia, hypokalemia, hypercapnia... 

In such a case, the first stage is uncompensated metabolic acidosis, in which excess H is largely taken up by the blood buffers. The chemical reactions are shown in Table 3.5. Both types of buffer base, bicarbonate and non-bicarbonate, combine with hydrogen ions. For the bicarbonate system, the CO2 yielded (reaction 2) is lost via the lungs. As a result of reaction 2 in Table 3.5, bicarbonate is removed from the blood to be excreted as COj and the blood bicarbonate concentration falls. 

D. Blood from a patient with an uncompensated metabolic acidosis would yield a point lying on the normal blood line . 

Case 3, onset low pH, PCO2 normal, negative B.E., uncompensated metabolic acidosis. Later PCO2 now low (hyperventilation) negative B.E. but less negative than before metabolic acidosis with respiratory and renal compensation. 

Case 4, onset high pH, PCO2 normal, positive B.E., uncompensated metabolic alkalosis. Later PCO2 now high (hypoventilation), B.E. unaltered metabolic acidosis with respiratory compensation, no renal compensation. 

Figure 3.4 Identification of various acid-base disturbances. Acute disorders are synonymous with uncompensated disturbances, whereas chronic conditions are synonymous with partially compensated or compensated disturbances. If a specific case falls outside the shaded areas, a compound acid-base disturbance may be suspected, such as the coexistence of respiratory acidosis (partially compensated) and metabolic alkalosis. Unshaded areas may also indicate a transient state between an acute (uncompensated) state and a chronic (partially compensated) condition. (From Cogan MG, Rector FC Jr., Seldin DW. In Brenner BM, and Rector FC Jr, eds. The Kidney, 2nd ed., Vol. 1, Philadelphia WB Saunders, 1986, p. 860.)...

The phase of primary respiratory alkalosis rarely is recognized in children with salicylate toxicity. They usually present in a state of mixed respiratory and renal acidosis, characterized by a decrease in blood pH, a low plasma bicarbonate concentration, and normal or nearly normal plasma PCO2. Direct salicylate-induced depression of respiration prevents adequate respiratory hyperventilation to match the increased peripheral production of CO2- Consequently, plasma PCO2 increases and blood pH decreases. Because the concentration of bicarbonate in plasma already is low due to increased renal bicarbonate excretion, the acid-base status at this stage essentially is an uncompensated respiratory acidosis. Superimposed, however, is a true metabolic acidosis caused by accumulation of acids as a result of three processes. First, toxic concentrations of salicylates displace 2-3 mEq/L of plasma bicarbonate. Second, vasomotor depression caused by toxic doses of salicylates impairs renal function, with consequent accumulation of sulfuric and phosphoric acids. Third, salicylates in toxic doses may decrease aerobic metabolism as a result of inhibition of various enzymes. This derangement of carbohydrate metabolism leads to the accumulation of organic acids, especially pyruvic, lactic, and acetoacetic acids. 

Comparison. The points for compensated respiratory acidosis and compensated metabolic alkalosis are (much closer together than, further apart than) the points representing the uncompensated disorders. Consequently, it is (easy, difficult) from the biochemistry of the blood alone to discriminate between the compensated disorders. 

Explain that the acid-base status can be deduced from the blood biochemistry in cases of uncompensated respiratory or metabolic disorder. Demonstrate examples of compensated disorders (e.g. compensated respiratory acidosis and compensated metabolic alkalosis) in which the same abnormality of blood biochemistry may be reached by different routes. Hence explain the need, in such cases, to seek each cause and evaluate its effect. 

A condition in which there is loss of base or accumulation of acid capable of causing a fall in pH to below nornial limits (an uncompensated acidosis). If this has been corrected by compensatory mechanisms (see below) it is known as a compensated acidosis. Acidosis can be classified into either a primary metabolic or respiratory disorder, although occasionally mixed types may occur. 

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