Symptoms and signs of extracellular fluid volume deficit include all of the following EXCEPT:
High pulse pressure occurs with extracellular fluid volume excess, but the other symptoms and signs are characteristic of moderate extracellular volume deficit.
A low urinary [NH4+] with a hyperchloremic acidosis indicates what cause?
Metabolic acidosis with a normal AG results either from exogenous acid administration (HCl or NH/), from loss of bicarbonate due to GI disorders such as diarrhea and fistulas or ureterosigmoidostomy, or from renal losses. In these settings, the bicarbonate loss is accompanied by a gain of chloride; thus, the AG remains unchanged. To determine if the loss of bicarbonate has a renal cause, the urinary [NH/] can be measured. A low urinary [NH4 +] in the face ofhyperchloremic acidosis would indicate that the kidney is the site of loss, and evaluation for renal tubular acidosis should be undertaken. Proximal renal tubular acidosis results from decreased tubular reabsorption of HC03 -, whereas distal renal tubular acidosis results from decreased acid excretion. The carbonic anhydrase inhibitor acetazolamide also causes bicarbonate loss from the kidneys.
When lactic acid is produced in response to injury, the body minimizes pH change by:
Lactic acid reacts with base bicarbonate to produce carbonic acid. The carbonic acid is broken down into water and carbon dioxide that is excreted by the lungs. Any diminution in pulmonary function jeopardizes this reaction.
What is the best determinant of whether a patient has a metabolic acidosis versus alkalosis?
While bicarbonate, Pco2, and patient history often can suggest the most likely metabolic derangement, only the measurement of arterial pH confirms acidosis versus alkalosis.
If a patient's arterial Pco2 is found to be 25 mm Hg, the arterial pH will be approximately:
A low Paco2 indicates excess elimination of carbon dioxide by the lungs, and the body pH will fall. Within reasonable physiologic ranges a 15 mm Hg fall in Paco2 should produce a 0.12 change from the normal body pH of 7.4.
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