RESPIRATION AND ACIDOSIS 325 



mineral bases was determined, Fitz and Van Slyke concluded that 

 no other equation including excretion rate and concentration was so 

 satisfactory as the above simplification of that used by Ambard 

 for urea and chloride. 1 



The value 80 5-v/w indicates, with an error which is usually 



less than 10 volumes per cent, the level of the plasma carbon dioxide 

 capacity. Diabetics receiving bicarbonate administrations are excep- 

 tions, the blood bicarbonate in such cases being, as a rule, much higher 

 than indicated by the urine. 



Of the two indirect measures of alkali reserve the alveolar carbon 

 dioxide determination appears the more accurate in measuring the 

 more severe stages of diabetic acidosis, such as are encountered in 

 threatened coma, while the index of acid excretion is the more accurate 

 in measuring the more common intermediate stages. 2 



In nephritis, acidosis (lowered blood bicarbonate) may occur with- 

 out increase in acid excretion or even with decrease of the latter. 

 Consequently the excretion cannot be used as an indicator of acidosis 

 when nephritis is present. 



For values of the acid index under different conditions see table, 

 page 317. 



5. Alkali Tolerance. 3 This method is quite reliable for proving 

 the absence of acidosis, but is not particularly dependable for show- 

 ing either the presence or the degree of acidosis when it exists. This 

 seems to be due in part at least to the fact that in conditions asso- 

 ciated with acidosis the power of the kidney for excretion of alkalies 

 may be markedly impaired. 



Principle. Sodium bicarbonate is administered in small amounts, 

 either by mouth or intravenously until the reaction of the urine changes 

 from acid to alkaline. The amount of bicarbonate is then noted. 



Procedure. Give (by mouth) 5 grams of sodium bicarbonate in 100 c.c. 

 of water to the subject under examination. Repeat every half hour until the 

 total bicarbonate administration is equivalent to 0.5 gram per kilogram of body 

 weight unless the urine becomes alkaline before that time. In case the urine 

 does not become alkaline with the above bicarbonate ingestion, continue the 

 administration of the alkali until the urine shows an alkaline reaction. 4 The 

 urine should be voided by the subject before each administration of bicarbonate. 

 Test each specimen of urine with litmus, boiling those samples which are only 



1 Ambard: Physiologic normale et pathologique des reins, Paris, 1914. 



2 Stillman, Van Slyke, Cullen, and Fitz: Jour. Biol. Chem., 30, 405, 1917. 

 'Sellards: Bull. Johns Hopkins Hosp., 23, 289, 1912; Palmer and Henderson: Arch. 



Int. Med., 12, 153, 1913; Palmer and Van Slyke: Jour. Biol. Chem., 32, 499, 1917. 



4 Because of the likelihood of producing a condition of alkalosis it is advisable not to 

 continue the administration of bicarbonate without evidence from blood analysis showing 

 an alkali deficit. 



