NATHAN W. SHOCK Foundation Chicago, · and interpretation of shifts in the acid-base balance. By the use of these methods the details of variations in the acid- base balance in the

STUDIES OF THE ACID-BASE BALANCE OF THE BLOOD*

IV. CHARACTERIZATION AND INTERPRETATION OF DIS- PLACEMENT OF THE ACID-BASE BALANCE

BY NATHAN W. SHOCK AND A. BAIRD HASTINGS

(From the Lasker Foundation for Medical Research and the Department of Medicine of the University of Chicago, Chicago)

(Received for publication, August 26, 1935)

It is now well recognized that the conditions in the blood during the respiratory cycle, and in experimental or clinical acidosis or alkalosis, can be expressed in terms of three variables, viz. CO% tension, bicarbonate concentration, and pH, and that simultaneous determinations of any two of these variables fixes the third, in conformity with the Henderson-Hasselbalch equation. The relationships between these variables define what is now commonly known as the “acid-base balance” of the blood. Obviously, the determination of only one of the three variables is insufficient. It is now also well known that the acid-base balance may be displaced in different directions under various experimental and pathological conditions, and that the direction and extent of displacement are in themselves of physiological and clinical significance. The importance of these considerations was first pointed out in the classic paper of Van Slyke (23). Our knowledge of the subject has been made more exact by experiments upon blood in vitro, by experiments upon intact animals, and by observations upon the blood in pathological conditions. Since the subject has received thorough treatment by Peters and Van Slyke ((18) p. 868), an extensive review is unnecessary here.

With the methods previously available which have imposed limitations upon the number and frequency of observations, certain phases of the problem of the acid-base balance-more particu- larly, those having to do with the changes occurring with time

* This work was supported by a financial grant from the Julius Rosen- wald Fund.

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240 Acid-Base Balance of Blood. IV

following a disturbance of the normal relationships-have re- mained obscure. In an effort to make these phenomena accessible to study, the authors (21) have introduced a microtechnique, by which all of the data necessary for characterization of the acid-base balance may be obtained from analysis of minute samples of blood taken from the finger tips at intervals as short as 30 seconds. In addition, the authors (22) have devised a graphic method, depending upon the use of triaxial coordinate paper, for the representation and interpretation of shifts in the acid-base balance.

By the use of these methods the details of variations in the acid- base balance in the blood of normal individuals have been studied, which has resulted in a more complete understanding of the significance of shifts of the acid-base balance. In addition, studies of the rate of elimination of fixed alkali and fixed acid, by the normal individual, have been made. These comprise the contributions of the present paper.

Theoretical

Starting from normal conditions, acidosis may result from an excess of COZ in the blood, alkalosis from a CO:, deficit. With no change in fixed acid or fixed base concentrations, the acid-base balance is a function of the CO2 tension and the bicarbonate concentration. When whole blood is titrated in vitro with COZ the well known carbon dioxide absorption curve is obtained. From these considerations it would appear that, unless the organism responds to changes in CO2 tension with the entrance into or with- drawal from the blood stream of fixed acid or fixed base, any displacement of the acid-base balance of the blood in vivo as a result of CO2 excess or deficit should follow the path of the carbon dioxide absorption curve, and that any deviation from this path would indicate a change in fixed acid or base.

Acidosis may also result from excess of fixed acid or deficit in fixed base. Conversely, alkalosis may result from excess of fixed base or deficit of fixed acid. Under any of these conditions the CO2 tension or the bicarbonate concentration or both are altered by physiological processes in such a way that the acid-base balance is displaced, but may still be accurately characterized by the COZ tension, bicarbonate concentration, and pH. The effects of adding fixed acid or fixed base to whole blood in vitro are known,

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N. W. Shock and A. B. Hastings 241

but much less is known as to the details of the response of the intact organism to the administration of these substances. The question of whether displacement of the acid-base balance as a result of the administration of fixed acid or fixed alkali occurs with or without change in CO2 tension is still an open one. It seems probable, however, from the results of previous work, that the typical physiological response to fixed acid excess is such that the CO2 tension and pH both decrease and, conversely, that the

FIQ. 1. Acid-base chart showing four primary acid-base paths

response to fixed alkali excess is such that the CO2 tension and pH both increase.

On the basis of these considerations a diagram has been constructed, representing, on triaxial coordinates, four hypothetical major pathways of displacement of the acid-base balance in the intact organism (Fig. 1). The line labeled “CO2 excess” and “CO2 deficit” represents an average CO2 absorption curve for oxygenated true plasma, as determined from in vitro experiments by Henderson and his coworkers (10). It is slightly curved to represent accurately the experimental data. The line labeled

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“Acid excess” and “Alkali excess” has been drawn at right angles to the CO2 absorption curve. Drawn thus, it is consistent with known clinical and experimental observations that fixed acid excess results in decreased CO2 tension and pH as well as bicarbonate, and that fixed base excess results in increases of the three variables. The extent to which this hypothetical path is correct is one oi the questions to be answered by the experiments of this paper.

As a further illustration of how a combination of changes of CO1 tension and of factors referable to the fixed acid of the blood may affect the acid-base path, the respiratory cycle of blood has been used as an example. The respiratory cycle of normal blood, plotted on the triaxial acid-base chart, takes the form indicated by the lines connecting the points A and V in Fig. 1. The point A represents the acid-base balance of Bock’s arterial blood, and the point V his mixed venous blood (10). It is apparent that the path from A to V not only indicates titration of the blood with CO2 but also the operation of a factor indicating an increase in fixed base. The latter is attributable to the reduction of the hemoglobin in the passage of the blood through the tissues, and the consequent lessening of its acidic strength. In passing from mixed venous to arterial blood, the same factors are effective but operate in the opposite direction. The small inner hexagon represents the normal area within which points denoting the acid-base balance of the blood of normal individuals may be expected to lie (22).

The present paper has a two-fold purpose: (1) the presentation of experimental data on the rate of change of various factors involved in the definition of the acid-base balance with particular attention to individual differences in the rate of return to normal after displacement; (2) the interpretation of the direction and extent of acid-base displacement and recovery in terms of the hypothetical pathways illustrated in Fig. 1.

Methods’

Blood samples were drawn and determinations of volume of cells, pH,, and total COz were made (in triplicate) by the micro-

1 Tables of the original data, of which only illustrative examples can be published here, may be obtained by applying to the authors.

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technique previously described (21). The CO2 tension of the blood, pCOs, and the bicarbonate concentration of the plasma, (BHCO*),, were calculated from the results of these determinations by use of a nomogram constructed for this purpose (8).1

The use of triaxial coordinates, above referred to, in studying the paths of displacement and of recovery, has been fully described in Paper III (22).

Rate of Change of Acid-Base Balance

Efects of Ammonium Chloride and of Sodium Bicarbonate

Experiments upon the effects of fixed acid and fixed alkali on the acid-base balance were confined to the use of ammonium chloride and sodium bicarbonate, administered orally.

The effect of ammonium chloride ingestion on the acid-base balance of the blood of normal individuals has been studied by Gamble, Blackfan, and Hamilton (4), Haldane (7), and Koehler (13). Comparable experiments on the effect of sodium bicarbonate ingestion have been made by Davies, Haldane, and Kenna- way (3), Koehler (13), Palmer, Salvesen, and Jackson (14), and Palmer and Van Slyke (15).

Previous investigators have adequately demonstrated that an acidosis with lowered pH, and (BHCO,), follows the ingestion of ammonium chloride, and an alkalosis with increased pH, and (BHCO&. follows the ingestion of sodium bicarbonate. Since their observations were made only at infrequent intervals after the ingestion of a single dose of the salt, their data are inadequate for the purpose of determining with accuracy the pathways followed, and the rates of change during displacement of the acid-base balance from, and recovery to, normal.

Experimental Procedure-Seven normal males served as subjects for thirty-eight experiments. The subject came to the laboratory, without breakfast, at 8.00 or 8.30 a.m. for each experiment, which was carried out as follows : (1) Samples of finger blood were drawn at 8.30 and 9.00 to serve as normal controls. (2) After drawing the blood sample at 9.00 a.m. the subject was usually given 5 or 10

f Although the method used in odr work yields the pH and (BHCO,) of plasma, it has been decided to use pH, and (BHCO& throughout, in order to avoid multiplication of symbols. For the purposes of the paper, serum and plasma may we regarded as identical.

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gm. of NH&l in 300 to 500 cc. of HzO, or 10 or 20 gm. of NaHCOs in 300 cc. of HzO. (3) Blood samples were drawn at half hour intervals beginning at 9.30 a.m. and continuing until 12.30 p.m. (4) The subject ate lunch after the 12.30 blood sample was drawn. (5) Blood samples were drawn at 1 hour intervals beginning at 1.30 and concluding at 6.30 p.m. A total of eighteen ammonium chloride experiments and twenty sodium bicarbonate experiments was completed.

2 46.0

2 420

3 4 5 6

FIG. 2. Effect of NH&l on the acid-base balance of the blood

In three additional experiments three 5 gm.. doses of ammonium chloride were given at 1 hour intervals in order to investigate the effect of successive doses. In six experiments a second dose of 20 gm. of NaHC03 in 300 cc. of Hz0 was given at 1.30 p.m., and blood samples were drawn at half hour intervals during the afternoon as well as the forenoon. The final blood sample was drawn at 7.30 p.m. In cases where the results were not yet normal, another blood sample was obtained at 8.30 the following morning.

Efects bf Administration of Ammonium Chloride-The data of each experiment-V,, pH,, (BHCOI),, and pCOz--were first

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plotted against time. While the general type of response following 10 gm. of ammonium chloride was the same in all individuals, as illustrated by a representative experiment (Fig. Z), certain variations were found in extent of displacement, time of maximum effect, and rate of recovery. Examination of the curves of the eighteen experiments with ammonium chloride indicated the following: (1) A progressive decrease in (BHCO,), occurred, usually reaching a minimum between 26 to 3 hours after the ingestion of the NH&l. (2) The maximum decrease in pH, was 0.12 to 0.16 pH, for a dose of 10 gm. Dosages of 5 gm. produced their maximum effect in somewhat less time. (3) The rate of recovery was appreciably less than the rate of displacement, as shown by the rate of change of both pH, and (BHCOJ,. (4) There was often a rise in pCOz during the period of displacement. When the point of maximum change in pH, and (BHCOI), was reached, however, the pCO% usually decreased from 2 to 4 mm. of Hg. During the recovery period there was usually an additional decrease in pCOz of from 3 to 5 mm. of Hg. These pCOz changes will be brought out more clearly in the acid-base paths to be presented later.

The cumulative effect of small dosages of ammonium chloride was studied. When a single 15 gm. dose of ammonium chloride was given, the maximum displacement was not as great as when the same amount was given in three 5 gm. doses, the minimal (BHCOS)~ being 18.7 and 14.8 mM per liter respectively. This observation is of importance in the use of ammonium chloride for therapeutic purposes.

E$ects of Administration of Sodium Bicarbonate-The data were first plotted against time. Examination of the curves of the twenty experiments with sodium bicarbonate, one example of which is shown in Fig. 3, indicated the following: (1) The (BHCOJ, increased rapidly and reached a maximum within 1 to 13 hours following sodium bicarbonate ingestion. It may be noted that the rate of change was more rapid and the maximum displacement was reached sooner than after ingestion of ammonium chloride. (2) The (BHCOS), recovery curve was of a characteristic type, showing, in most instances, a rapid elimination from the blood for about 13 hours following the peak response. During this period there was a decrease in (BHCOI), of about 50 per cent from the

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peak. The remainder of the bicarbonate was eliminated quite slowly, complete recovery sometimes not occurring until the following day. (3) The maximum increase in pH, of about 0.10 to 0.16 pH for the given dosage of ‘20 gm. was reached between 1 and 13 hours after ingestion. (4) In most individuals recovery of pH, to normal values was complete within 2 to 3 hours. (5) In some of the experiments there was a slight increase in pC!Oz, amounting to 4 to 10 mm. of Hg, at the point of maximum increase in pH, and (BHCO,),. (6) During the recovery period there was

1 I I/. .A II\ I I I I I I I I I I If I I I’ll

9A.M. IO N /z/x /pa 2 3 4 5 6

FIG. 3. Effect of NaHC03 on the acid-base balance of the blood

sometimes a further increase in pCOz of from 5 to 8 mm. of Hg, although this was not an invariable result.

Experiments were performed in which two doses of sodium bicarbonate were given on the same day. In addition to the fea- tures already pointed out, the following was observed: (1) The response to the second dose was usually greater than that to the first dose with respect to increase in both pH and bicarbonate. (2) The increase in $0, during the recovery period was particu- larly accentuated.

Rate of Elimination of Excess Fixed Acid and Fixed Base--Since our data permit the plotting of acid-base displacement and recov-

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ery against time, it seemed desirable to find a means of char- acterizing, in quantitative terms, the rate at which the acid-base balance of the blood returns to its initial condition after displacement. It was felt that if such characterization were possible, individual differences in the ability of normal and pathological subjects to deal with abnormal amounts of fixed acids and alkalies might be revealed which were not shown by single acid-base determinations.

To plot simply the change of bicarbonate against time is insufficient, however, because, with increasing pH,, more base is bound by the proteins of the blood, and the increase in bicarbonate observed is less than the actual addition of fixed base (or loss of fixed acid) which occurred. By utilizing the buffer value of whole blood, however, and correcting all observed values of (BHCOJb to pH 7.4, the change in the amount of fixed acid or fixed base in the blood could be estimated. These calculations have been made, assuming the relation dB/dpH = 25, where dB/dpH represents the change in millimoles of base per liter of blood bound by blood buffers per unit change in pH, between the pH limits 7.2 and 7.6. Since changes in percentage of cells were slight in each experiment, no attempt was made to correct for changes in the buffer value of t,he blood during the course of an individual experiment. The BHC03 of the total circulating blood was then estimated by multiplying the (BHCOs)a at pH, 7.4 by the estimated blood volume, which was assumed to be 0.077 times the body weight of the subject. The apparent amount of additional fixed alkali or acid in the blood was estimated as the change in the total bicarbonate, compared with the initial value before the ingestion of the alkalinizing or acidifying salts. The percentage of t,he ingested acid or alkali present in the blood at definite times was then calculated by dividing the change in total bicarbonate by the millimoles of salt ingested, and multiplying by 100. These percentages were plotted against time elapsed since administration of the salt. An example is given in Fig. 4.

These curves showed the approximate percentage of ingested fixed alkali or fixed acid present in the blood. They were characterized by two phases: an ascending portion in which the salt was being absorbed faster than it was being eliminated, and a descending portion in which the process of elimination from the

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blood stream was predominant. The form of the curves during recovery suggested a relation to chemical reactions of the first order, de/c = kdt, or log c = kt + constant. By plotting the logarithm of the percentage change in bicarbonate against time, a linear relationship was obtained in which the slope, k, is ten- tatively called the constant of elimination (Fig. 5). The significance of k is that it denotes the rate at which the logarithm of the percentage of circulating excess acid or alkali changes. Similar plots were made for all experiments, and the slope, or elimination constant k, was estimated for each.3

.k?JECl COt

2 3 4 5 6 7 8 ,9 IO HOURS FOL LOWhV6 MESTION

FIQ. 4. Rate of disappearance of excess NaHC03 from the blood

The individual values of k obtained in twenty-seven experiments on six individuals are listed in Table I. It may be seen (1) that reproducible elimination constants were obtained in dupli- cate experiments on the same individual when the same dosages of the same salt were used, (2) that varying the dosage did not

3 It may be pointed out that plotting the logarithm of the change in (BHC03),, corrected to constant pH,, against time will yield the same value for the elimination constant as the calculation just described. However, since our subjects were of different weights and were given different amounts of alkalinizing and acidifying salts, it was necessary, in studying the influence of these factors, to estimate the per cent of ingested salt which was circulating in each instance.

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LOG#R/Tfff’9 OF PERCENT \ OF &VOIJNT iNGCSTED 41 FOUND IN BLOOD

I 2 3 4 5 6 7 a 9 IO HOUR.5 FOLLOW/NG /NCESTlON

Fm. 5. Examples of determination of elimination constants, For NH&l, k = -0.04; for NaHCOz, k = -0.14.

TABLE I

Elimination Constants

Sub- ject

-

JB

JE

LM

AM ss

CT

k, NH&l

Dosage

5 gm. 10 gm. 15 gm. ~-

-0.10 -0.08 -0.05 -0.08 -0.06 -0.06

-0.11 -0.08 -0.07

-0.03 -0.04 -0.06 -0.07

-0.04

20 gm.

-0.04

k, NsKCOz

Dosage MeaIl Ml-%ll

10 gm. 20 gm. 25 gm.

-0.08 -0.08 -0.07 -0.07 -0.05

-0.06 -0.07 -0.05 -0.06

-0.08 -0.11 -0.11 -0.11

-0.04 -0.11 -0.12 -0.11 -0.06 -0.05 -0.04

-0.03 -0.04 -0.14 -0.14

materially influence the value of k, and (3) that in two of the six subjects studied, the elimination constant following ingestion of NaHC03 was strikingly greater than that following NH&l.

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Although the series is too small to permit statistical treatment, it would appear that the individual subjects varied with respect to the mean value of k obtained. These differences in elimination constants were more marked with NaHCOs than with NH&l. It is probable that such differences with respect to the excretion of acid and alkali in pathological conditions may be of clinical significance.

The smaller the dose of ammonium chloride, the greater was the per cent of circulating excess acid at the time of maximum acid- base displacement. This is shown by the experiments on JB and AM in Table II. Whether or not this is also true for sodium bicarbonate awaits further experimentation. It was also usually

TABLE II

Percentage of Acid or Alkali Ingested Found in Blood at Time of Maximum Acid-Base Displacement

Subject DIXW

-~ gm.

*JR 5 ‘I 10 ‘I 15

AM 5 ‘I 10 I‘ 15

rnY

94 187 281

94 187 374

-

-

N&Cl Maximum dis-

placement

hrs.

0.5 2.0 3.0 2.0 2.0 2.5

PR. cent

29.5 20.9 13.9 39.0 14.5 11.8

- -

f subject

- NaHCOa

Maximum dia- placement

JR ‘I

LM ‘I

ss AM

am. 7nY per cent

20 238 17.2 20 238 19.3 10 119 32.6 20 238 22.0 20 238 19.0 20 238 13.6

-

hts .

1.0 1.0 1.0 1.5 1.5 1.0

observed that the point of maximum acid-base displacement occurred after a longer time had elapsed following the ingestion of ammonium chloride than following an equivalent dose of sodium bicarbonate.

Ej’ects of Rebreathing and Overbreathing

CO, Excess-The changes in the acid-base balance of the blood produced by increasing the COz tension of the inspired air have been described by several investigators (3, 11, 20). However, the question of whether the changes are simply those to be expected if blood is titrated with carbon dioxide, or whether changes in fixed acid or base are involved, remains an open one (18). The purpose of the experiments to be described in this section was to

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titrate the blood in Go with CO2 and study both the nature of the changes produced in the acid-base balance of the blood and the t,emporal relationships involved in these changes.

Experimental Procedure-A series of twenty-four experiments was carried out, with six normal males as subjects. The subject rebreathed through a closed system of about 35 liters of oxygen for 15 to 18 minutes, during which time the per cent of CO2 gradually rose to approximately 9 per cent. Samples of blood were drawn at 2 minute intervals and analyzed as previously described. Samples of the air in the tank were analyzed at 2 minute intervals for the per cent of COZ by the Haldane apparatus for gas analysis.

Physiological E$ectsIn all subjects the respiration increased gradually in rate and amplitude, as has been reported in numerous experiments (3, 16, 19). Toward the end of the rebreathing period, the respiration rate and amplitude reached uncomfortable proportions, finally making continuation of the experiment impossible.

Blood Cltanges-The data from all experiments were plotted against time, as illustrated by a representative experiment in Fig. 6. The pH, showed a decided decrease during rebreathing. In most experiments the drop began after 2 minutes of rebreathing, although in the first experiments with some subjects the pH, slightly increased during the first 2 minutes of rebreathing. This increase in pH, may have been produced by overbreathing on the part of the subject. The pH,, continued to fall throughout the rebreathing period at a rate of 0.02 to 0.04 pH, per minute, reaching values of 7.18 to 7.20 in all experiments. When rebreathing was stopped, the pH, rapidly returned to normal. In fact, in some experiments the pH, was higher 2 minutes after the cessation of rebreathing than 4 minutes later.

The pCOz of the blood increased during rebreathing at a posi- tively accelerated rate, rising from normal values of 40 to 45 mm. of Hg t.o a maximum of 70 to 77 mm. In some experiments there was a slight decrease in pCOz during the first 2 minutes of rebreathing.

Not much change occurred in (BHCOS). for the first 4 to 8 minutes of rebreathing. Subsequently the (BHCOI), increased at the rate of 0.5 to 1.0 mM per liter per minute until the end of the rebreathing period.

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COZ De$ci&-It has been well established that with overventilation the following changes take place. As the pCOz of the alveolar air-and, consequently, of the blood-decreases, the pH, increases and the (RHCOJ, decreases. Whether or not a decrease in the level of the CO2 absorption curve also occurs appears to depend

7.26

Z/8

OM/N.~ OM/N.~ 8 8 12 I6 20 12 I6 20 24 28 32

FIG. 6. Effect of rebreathing on the acid-base balance of the blood

to a large extent upon the length of time the hyperpnea is main- tained (5,12,17). The evidence on these points has been thoroughly reviewed by Peters and Van Slyke ((18) p. 954), and will not be repeated here. Since doubt exists as to the direction, rate, and extent of the changes produced both during the period of displacement and the period of recovery, the acid-base microtechnique

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was employed to st,udy these questions (21). In addition, acid- base paths were determined in experiments where overbreathing was combined with fixed alkali and fixed acid excess.

Experimental Procedure-A series of twenty-four experiments was carried out on six normal males. The subjects came to the laboratory at 8.30 a.m. without breakfast. First, a normal control sample of blood was drawn; then the overbreathing. was begun with the subject lying on his back. The breathing was carried on as forcibly as possible, with emphasis on expiration. The overbreathing period varied in extent from 6 to 20 minutes. Blood samples were drawn from the finger-tips at 2 minute intervals during the overbreathing period, and for the first 10 minutes of the recovery period. Subsequent samples were drawn at intervals of 3 to 8 minutes for the succeeding 20 minutes.

Physiological E$ects-The physiological effects of hyperventilation have been repeatedly described (1, 2, 6, 16). The extent of the changes induced in these experiments may be judged from the fact that in all subjects, except one, definite signs of tetany, includ- ing carpopedal spasm, were observed.

Blood Changes-Results from all experiments were plotted as in Fig. 7. The changes in pH,, pCOz, and (BHCOI), occurring during overbreathing and during recovery may be summarized briefly.

The pH, increased rapidly-in many experiments as much as 0.04 to 0.06 pH, per minute-during the first 3 or 4 minutes of overbreathing. In . experiments where the overbreathing was continued for a longer time, this initial period was followed by one in which the rate of increase was not so rapid. Perhaps the most striking observation of this series of experiments was the rapidity with which the pH, returned to normal following the cessation of overbreathing. While individuals differed in their speed of recovery, the pH, dropped 0.10 to 0.24 pH, units during the first 2 minutes after cessation of hyperventilation, depending on the extent of displacement. In most experiments the pH, had returned practically to normal within the first 4 minutes after overbreathing was stopped. The remaining decrease in pH, took place at a diminishing rate, complete recovery being attained in 15 to 20 minutes.

The inverse relationship between the pCOz and pH, was strikingly illustrated. Overbreathing produced a rapid fall in pCOz,

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amounting to 4 to 6 mm. of Hg per minute in most experiments. In all the experiments the rate of decrease in pCOz showed a nega- tive acceleration-the first 2 minutes of overbreathing producing the greatest change per minute. Values of pCOz as low as 15 to 20 mm. of Hg were reached in most of the experiments. After

MIN.4 8 0. FIG. 7. Effect of overbreathing on the acid-base balance of the blood

I I - I I I I I I ! -, ,j.‘

20 24 28 32 36

overbreathing, the pCO2 of the blood rose as much as 25 mm. of Hg in 2 minutes. The subsequent rise was at a decreasing rate, complete recovery requiring 15 to-25 minutes.

In all experiments, the (BHCOJ, decreased slowly. In most cases this decrease progressed at a practically constant rate of from 0.2 to 0.7 mM per liter per minute. The actual decrease amounted

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to from 4 to 7 mM, depending upon the length of time the overbreathing was continued. The bicarbonate content of the serum increased as soon as the pCOz started to rise following the cessation of overbreathing, and returned to a value about 1 to 2 mM per liter below the initial value within 15 to 20 minutes.

Acid-Base Paths of Displacement and Recovery

Administration of Ammonium Chloride-The data obtained from the time curves were plotted on triaxial coordinates, in order t.o investigate the paths of acid-base displacement. Each point on such a chart represents the acid-base condition of the blood at a given time. As stated before, the time interval between the first ten points is 3 hour, while that between subsequent points is 1 hour.

Fig. 8 illustrates the types of paths encountered in four subjects. The large open circles represent experimental observations following the administration of NH&l. These diagrams show that after the ingestion of ammonium chloride the change in the blood during the period of displacement was in the direction of decreased pH, and (BHC03),, without much change in pCOz. In some instances, however, there was an immediate increase in pCOz during the first half hour following the ammonium chloride ingestion.

After t,he point of maximum displacement was reached, there was a period of decreasing pCOz which resulted in an increase in pH,. The subsequent return to normal varied somewhat in the direction taken, but in general may be said to have followed a course of increasing pH,, (BHCOI),, and pCOz. These events may be described as indicating that there was a period of displacement without “compensation” of pH. followed by a period of recovery with compensation (23).

Administration of Sodium Bicarbonate-In Fig. 8 the triangular points represent data on four individuals following the administration of NaHC03. From an examination of the acid-base paths of all the experiments with sodium bicarbonate the following state- ments may be made. (1) The path of displacement of the acid- base equilibrium by the ingestion of sodium bicarbonate was linear when plotted as shown here. This line of displacement tended to remain practically parallel to the constant pCOz lines. (2) In all twenty experiments there was an increase in pCOz after the

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maximum pH, and (BHC03), were attained. There was then a period of increased pCOz which caused a swing in the path toward the initial pH, value. The subsequent return to the normal condition took place with decreasing (BHCOa),, pCOz, and pHa.

Thus it may be said that. during the period of displacement of

FIGS. 8, a TO 8, d. Four primary acid-base paths of displacement and recovery determined on four normal human subjects. For explanation of symbols, see the text.

the acid-base balance with fixed base excess, there was apparently no compensation of pH,, but that during the recovery period compensation occurred (23).

CO2 Excess-In Fig. 8 the acid-base paths during rebreathing and recovery are indicated as circled crosses. In these graphs each

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point represents a blood determination at the constant interval of 2 minutes. The dotted line in the charts is the CO2 titration curve of normal human blood, plotted from the data of the in vitro experiments of Henderson and his collaborators. The graphs show that the slopes of the displacement paths of normal individuals were quite constant, and closely paralleled the CO2 titration curve of normal human blood. The slopes of the recovery curves were not sufficiently different from those of the displacement curves to indicate that t,here had been any significant change in fixed acid or fixed base as a result of CO* excess.

CO2 DeJicil-In Fig. 8 the solid black points represent data obtained at 2 minute intervals during overbreathing experiments. The linearity of the displacement path and t.he constancy of its slope, not only with respect to different experiment,s on the same subject but also for different subjects, were striking. These experiments showed that while the displacement path proceeded along the COz titration curve during the early stages, after continued overbreathing t,here was an appreciable increase in fixed acid of the blood which persisted for a much longer period than the COz effects. The recovery paths followed a line parallel to but lower t,han the paths of displacement.

Experiments were also performed in which the period of overbreathing was preceded by a single dose of either sodium bicarbonate (25 gm.) or ammonium chloride (10 gm.), producing changes in the fixed acid-base condition of the individual as previously reported, in order to determine t.he effect of such displacement on the path produced by overbreathing. The character of the changes resulting from overventilation was unaffected by fixed acid and fixed base displacement, although t,heir positions on the acid-base chart were of course altered. In Fig. 9 the solid trian- gles indicate the results of blood analyses made at half hour intervals following the ingestion of 25 gm. of NaHC03 in 500 cc. of HzO; the open circles, the results following the ingestion of NH&l. The solid circles are determinations made at 2 minute intervals during overbreathing and recovery. These results show strikingly the differentiation between metabolic and respiratory factors involved in the regulation of the acid-base balance of the blood.

Furthermore, from Fig. 9 it can be seen that the recovery path

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swings toward the direction of increased fixed acid in all the experiments. This may be taken as evidence for the presence of increased amounts of acid in the blood, amounting to about 1 to 2 mM per liter, probably formed as a result of the increased muscular work and the reduced oxygenation of the tissues following the diminished blood flow resulting from the overbreathing.

In view of the fact that tetany occurred in all overbreathing experiments on all subjects save one (AHM), regardless of whether they were normal or in a condition of fixed acid or alkali excess, it is believed that the excessive decrease in pCOz is to be viewed as the contributing cause, rather than the increase in pH,. Subjects

FIQS. 9, a AND 9, b. Complex acid-base paths. Respiratory alkalosis Juperimposed upon metabolic acidosis and alkalosis. For explanation of symbols, see the text.

with alkalosis produced by the ingestion of sodium bicarbonate often had a pH, higher than 7.50 without exhibiting tetany;whereas subjects with acidosis produced by the ingestion of ammonium chloride and then subjected to overbreathing developed tetany with pH, of 7.50 to 7.55. On the other hand, when the pCOz of the blood was diminished to approximately 20 mm., tetany ensued irrespective of the pH,.

It may also be pointed out that in these experiments instances were encountered in which the pH, was normal, but the (BHCOJ, and pCOz were markedly decreased. (See Fig. 9. pH = 7.40; (BHCOa)s = 18 mM per liter; pCOz = 30 mm. of Hg.) Such an

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observation might be regarded as a condition of compensated acidosis. As a matter of fact, in this instance it represents a combination of two abnormal conditions, which may be desig- nated as metabolic acidosis and respiratory alkalosis.

Major Acid-Base Paths-The outstanding points of similarity in the paths illustrated in Fig. 8 are: (1) The paths following COn excess and deficit correspond closely with the COZ absorption curve of blood, represented by the broken line on the charts. (2) The paths of recovery following COZ excess are, within the limits of observation, identical with the paths of displacement. (3) The paths of recovery following CO2 deficit are slightly displaced to the left, indicating the acquisition of some fixed acid by the blood. (4) The paths of displacement and recovery following fixed acid and base excess are approximately at right angles to the COZ absorption curves. (5) The fixed acid excess recovery curve is always displaced to the right of the displacement curve to a greater or less extent, indicating a respiratory adjustment leading to a lower pCOZ and higher pH,. (6) The fixed base excess recovery curve is always displaced to the left, indicating a respiratory adjustment leading to a higher $0, and lower pH,.

The points of dissimilarity are that the direction of displacement produced by fixed acid and base excess varies in different experiments, although it is usually approximately along a constant pCOZ line. The paths of recovery also vary in different individuals, from one approximating a constant $0, line to one making a right angle with the path produced by changes in CO2 tension.

Interpretation of Abnormal Acid-Base Condilions-Four major paths of displacement and recovery of the acid-base balance have been found experimentally, corresponding approximately to the hypothetical paths illustrated at the beginning of this paper (Fig. 1). It has been seen that the effects of the four major influences upon the acid-base balance, when acid-base data are plotted on triaxial coordinates, are, in typical instances, sufficiently separated from one another to permit the characterization of deviations from the normal condition. Pathological conditions affecting the acid-base balance may, on the basis of the considerations just cited, be classified under the following four main divisions.

Metabolic Acidosis-By this is meant a condition of fixed acid

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excess or fixed alkali deficit without respiratory complications. It is indicated in Fig. 1 by the line labeled “Acid excess.” This type of acidosis may be the result of excessive production of fixed acid, as in diabetes, or inadequate excretion of fixed acid, as in nephritis. It may be pointed out that anoxia leading to lactic acid accumulation causes an acid-base displacement in the direction of metabolic acidosis.

Metabolic Alkalosis-By this is meant a condition of fixed alkali excess or fixed acid deficit without respiratory complications. It is indicated in Fig. 1 by the line labeled “Alkali excess.” This type of alkalosis may be the result of loss of fixed acid, as in pyloric obstruction, or excessive absorpt.ion of fixed base, as in the treatment of gastrointestinal disorders with basic salts.

Respiratory Acidosis-By this is meant a condition of CO2 retention resulting from inadequate removal of CO2 from the lungs. It is indicated in Fig. 1 by the line labeled “CO2 excess.” This -type of acidosis may be the result of obstruction in the respiratory system, inadequate movement of the respiratory muscles, inadequate lung surface available for aerat.ion, or a decreased coefficient of diffusion through the pulmonary epithe- lium. In the presence of inadequate oxygenation of the blood in the lungs and any factor leading to metabolic acidosis, the displacement follows closely the CO2 absorption curve of the blood in vitro, and is equivalent to titrating the blood with COZ.

Respiratory Alkalosis-By this is meant a condition of excessive loss of CO* resulting from overventilation. It is indicated in Fig. 1 by the line labeled “CO2 deficit.” This type of alkalosis may be t.he result of excessive activity of the respiratory mechanism originating in the central nervous system. It is also observed in hyperthermia and in exercise accompanied by an increase in temperature. The direction of acid-base displacement follows closely the CO2 absorption curve of blood in vitro. Recovery to normal may be accompanied by slight displacement toward the direction of metabolic acidosis, owing probably to the entrance into the blood stream of lact,ic acid.

Combinations of Two Factors-Sometimes two or more factors tending to displace the acid-base condition from normal may operate simultaneously. For example, if one finds a decreased (BHCO,), and pCOn, but normal pH,, a condition of metabolic

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acidosis and respiratory alkalosis is indicated. On the other hand, the acid-base displacement may be in a direction of increased pCO2, decreased pH,, and decreased (BHCOa),. This would indicate a condition of metabolic acidosis and respiratory acidosis. Both of these conditions have been observed in dogs by Hastings and Steinhaus (9); the first, when the animals swam in water at a temperature of 40” and the second when the water was at a temperature of 15”.

It is hoped that the accumulation of further observations on the acid-base balance and the simultaneous study of clinical symptoms associated with the activity of the respiratory and cardiovascular systems will lead to a better understanding of the etiology of acid- base disturbances.

SUMMARY

The acid-base balance of the blood of normal individuals has been studied at frequent intervals under a variety of experimentally produced abnormal acid-base conditions. From the results it has been concluded: (1) that individuals may be characterized in terms of the rate at which the acid-base balance of the blood is restored to normal after experimental displacement; (2) that abnormal acid-base conditions may be characterized in terms of the physiological factors involved.

The significance of these conclusions for the interpretation of pathological acid-base conditions has been pointed out,.

BIBLIOGRAPHY

1. Collip, J. B., and Backus, P. L., Am. J. Physiol., 61, 568 (1920). 2. Davies, H. W., Brow, G. R., and Binger, C. A. L., J. Exp. Med., 41,

37 (1925). 3. Davies, H. W., Haldane, J. B. S., and Kennaway, E., J. Physiol., 64,

32 (1920). 4. Gamble, J. L., Blackfan, K. D., and Hamilton, B., J. Clin. Znu., 1,

359 (1925). 5. Gollwitzer-Meier, K., and Meier, E. C., 2. ges. exp. Med., 40, 70 (1924). 6. Grant, S. B., and Goldman, A., Am. J. Physiol., 62, 209 (1920). 7. Haldane, J. B. S., J. Physiol., 66, 265 (1921). 8. Hastings, A. B., and Shock, N. W., J. BioZ. Chem., 104, 575 (1934). 9. Hastings, A. F., and Steinhaus, A. H., Am. J. Physiol., 96, 538 (1931).

10. Henderson, L. J., Blood, A study in general physiology, New Haven (1928).

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11. Henderson, Y., and Haggard, I-I. W., J. Biol. Chem., 33, 333 (1918). 12. Henderson, Y., and Haggard, H. W., J. Biol. Chem., 33, 355 (1918). 13. Koehler, A. E., J. Biol. Chem., 73, 99 (1927). 14. Palmer, W. W., Salvesen, H., and Jackson, H., Jr., J. Biol. Chem., 46,

101 (1920-21). 15. Palmer, W. W., and Van Slyke, D. D., J. Biol. Chem., 32, 499 (1917). 16. Peabody, F. W., Arch. Int. Med., 16, 846 (1915). 17. Peters, J. P., Bulger, H. A., Eisenman, A. J., and Lee, C., J. Biol.

Chem., 67, 175 (1926). 18. Peters, J. P., and Van Slyke, D. D., Quantitative clinical chemistry,

Interpretations, Baltimore (1932). 19. Schneider, E. C., and Truesdell, D., Am. J. Physiol., 63, 155 (1922). 20. Scott, R. W., Arch. Int. Med., 26, 544 (1920). 21. Shock, N. W., and Hastings, A. B., J. Biol. Chem., 194, 565 (1934). 22. Shock, N. W., and Hastings, A. B., J. Biol. Chem., 194, 585 (1934). 23. Van Slyke, D. D., J. Biol. Chem., 46, 153 (1921).

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Nathan W. Shock and A. Baird HastingsBALANCE

DISPLACEMENT OF THE ACID-BASEINTERPRETATION OF

CHARACTERIZATION ANDBALANCE OF THE BLOOD: IV. STUDIES OF THE ACID-BASE

1935, 112:239-262.J. Biol. Chem.

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