80. ACID- BASE IMBALANCE OF BLOOD: MAN (Concluded) 



Part IV: PATHWAYS 



Any point on this acid-base diagram [ ij gives simultaneously occurring values of four variables: (1) whole blood 

 buffer base (BB)[j, the metabolic factor in the disturbance; (2) CO^ pressure (pC02), the respiratory factor; 

 (3) plasma CO^ content; and (4) pH. The scale of (BB)(^ is strictly accurate only for oxygenated human blood at 37*^C 

 having a hematocrit value of 45% or hemoglobin concentration of 15 g/100 ml. The width of the buffer base bar 

 corresponds to the "normal" range of arterial pCO^ selected, namely, 35-45 mm Hg. Similarly, the width of the 

 pCO^ bar is the normal range for (BB)|,, from 4b- 52 mEq/L. The heavy arrows represent typical average path- 

 ways of the four principal types of acid-base disturbance (Part II). They are based on observations of the contribu- 

 tor and colleagues [ 1-4] , but are representative of similar clinical data in the literature. In metabolic acidosis, 

 respiratory compensation is almost alw-ays present [2] ; in metabolic alkalosis, respiratory compensation is fre- 

 quently absent, especially under clinical conditions [3, 4] . In acute, experimental, respiratory disturbances the 

 pathways are in the horizontal pC02 bar, with virtually no change in (BB)^^ [ 5] . The four mixed types of acid-base 

 disturbance are not shown on the diagram, but the possible areas may be located from the classification in Part III. 

 Examples of these disturbances are mixed acidosis in thoracic surgery under ether anesthesia [ 6] , mixed alkalosis 

 in many dyspneic patients with congestive heart failure [ 7] , mixed hypercapnia in some cases of cor pulmonale [ 4], 

 and mixed hypocapnia in severe salicylate intoxication [ 2] . 



BUFFER BASE EXCESS 



pH 



CO? DEFICIT 



15' 



Respiratory 



acidosis 



with 



renal 



compensation 



5ry compensation 



BUFFER BASE DEFICIT 



Contributor : Singer, R. B. 



References : ( I] Singer, R. B., Am. J. M. Sc. 2£I^:199, 1951. [2] Singer. R. B., Medicine, Bait. 33:1, 1954. 

 [3] Singer, R. B., Deering. R. C, and Clark, J. K., J. Clin. Invest. 35:245, 1956. [4] Singer, R. B., unpublished. 

 (5) Shock, N. W., and Hastings. A. B.. J^l_2:239, 1935. [6) Beecher, H. K., and Murphy, A. J.. J. Thorac. Surg. 

 19:50, 1950. [7] Squires. R. D.. Singer, R. B., Moffitt, G. R.. Jr.. and Elkinton, J. R. , Circulation, N. Y. 4:697, 

 1951. 



98 



