INTUBATION STUDIES OF THE HUMANSMALL INTESTINE. IV.CHEMICALCHARACTERISTICS OF THE INTESTINAL CON-

TENTS IN THE FASTING STATE ANDAS INFLUENCEDBY THE ADMINISTRATION OF ACIDS, OF ALKA-

LIES ANDOF WATER1

By W. G. KARRAND W. OSLERABBOTT

WITH THE TECHNICAL ASSISTANCE OF

ALBERT B. SAMPLE(From the Gastro-Intestinal Section of the Medical Clinic, Hospital of the University of

Pennsylvania, Philadelphia)

(Received for publication July 22, 1935)

The development of a practical technique byMiller and Abbott (1) for the prompt collectionof jejunal and ileal contents from the normal hu-man subject, using a double-lumened apparatus soarranged as to obstruct passage beyond the pointof aspiration, has rendered possible for the firsttime a direct investigation of the chemical natureof these intestinal fluids comparable to the studiespreviously made on gastric and duodenal juicos.The method permits, in addition, a more completecollection of duodenal contents than can be ob-tained with a single-lumened tube. Thus an op-portunity is now available to make observationson material obtained in a satisfactory mannerfrom any part of the small intestine of man.

In this presentation we report the results ofchemical determinations made on contents fromthe duodenum, the jejunum and the ileum of in-dividuals with apparently normal digestive tracts.They show the range in reaction, bicarbonate con-centration and osmotic pressure, under fastingconditions and after the oral administration ofhydrochloric acid, of sodium bicarbonate and ofwater. Some data on the chloride, calcium, phos-phorous and total nitrogen concentrations are in-cluded. An attempt has been made to correlatethe various observations. The results will beused as a basis of comparison for work now inprogress in this Clinic on problems of intestinalsecretion and absorption.

METHODS

1. Subjects. The observations are based on fifty-oneintestinal intubations carried out on thirty individuals,

1Aided by a donation from Mr. Samuel S. Fels andby grants from the Faculty Research Committee andfrom Smith, Kline and French Laboratories.

some of whom were patients whose gastro-intestinaltracts were considered to be normal and some, paidhealthy subjects. Each subject took the tube in themorning after a 14 to 16 hour fast. The specimens in-cluded samples obtained consecutively at one intubationas well as samples from repeated intubations of thesame individual.

2. Intubation. The method (1, 2) involved the use ofa double-lumened tube with a thin rubber balloon at-tached over the distal end of one lumen. This balloon,when distended in the duodenum by the injection of air,stimulates peristalsis sufficiently to sweep the apparatusrapidly along the intestine, and then, when in the de-sired position and somewhat less tense, serves as a damto facilitate aspiration of the contents above it throughfenestrations in the second lumen. The efficiency ofthe balloon in checking the flow of contents was clearlyestablished by roentgen examination after the oral intro-duction of barium sulphate suspensions. The specimenswere aspirated by a negative pressure of 70 cm. of wa-ter, which is sufficient to conduct through a single lumenof a nine foot tube 150 cc. of intestinal juice per minute.As the end of the tube frequently reached the terminalileum in the course of three hours after traversing thepylorus, the entire length of the small intestine wasavailable for study.

Although both measurement of the length of the tubebeyond the pylorus and fluoroscopy were employed, theexact point in the small intestine from which materialwas being aspirated was difficult to determine, exceptwhen near the cecum. Even when the tube was checkedat the mouth and no more of it allowed to enter weobserved that nevertheless more and more of the in-testine tended slowly to assume a position above theballoon, thus causing the tube from time to time to reachan actually deeper level in the bowel. On one occasion,for instance, a balloon on a tube extending only four anda half feet beyond the pylorus lay in the upper ileumwithin three hours after it was swallowed, but after sixhours, without any more tube being allowed to enter, itwas found to be in the cecum. For this reason, and be-cause we have found no abrupt change in the characterof the contents or in the roentgen picture in different

893

W. G. KARR AND W. OSLER ABBOTT

parts of the bowel, we have designated the regions stud-ied as those reached by a tube extending 30, 60, 90, 120and 150 cm. below the pylorus. These distances, whenreached in such a time interval as we are accustomed toallow, may, we believe be interpreted as indicating re-spectively upper jejunum, lower jejunum and upper, mid-dle and lower ileum. Flouroscopic observation indicatesthat when with our technique the tube stands at 150 cm.after three hours, the balloon is usually at a point justabove the ileocecal valve.

3. Chemistry. The specimens were collected in all in-stances under oil. Chlorides were determined by a slightmodification of the method of Wilson and Ball (3) usingsaturated KMnO, as an aid in oxidation. The carbondioxide content was determined by the method of VanSlyke and Stadie (4). The pH determinations weremade immediately after collection by the balanced quin-hydrone method of Meeker and Oser (5). For thedetermination of calcium the material was dried and

RATE OF FLOW ACIDITY

DUODENU14 V 1

UPPER 7_ ]JEJUNUM5

CI0 CM)

LOWER LiJEJNUM S

ashed with a small amount of nitrate and sodium car-bonate. The melt was taken up with a slight excess ofacetic acid and after neutralizing to the proper pH thedetermination was continued by the micro method ofClark and Collip (6). The total phosphorus was deter-mined on 2 cc. by wet ashing with concentrated sulphuricacid and 30 per cent hydrogen peroxide and completingthe analysis by the method of Fiske and Subbarrow (7).Inorganic phosphorus was determined by the samemethod after precipitation with trichloracetic acid. Thisprecipitation often does not give a clear filtrate, and onlya few determinations were made. Total nitrogen wasdetermined by the micro-Kjeldahl method on dilutedspecimens.

Our analyses indicate that the only significant, osmoti-cally active solutes in the fasting intestinal contents arethe chloride and bicarbonate salts. In Table I are pre-sented data showing the close approximation between thesum of the chloride and bicarbonate anions and the total

BICARBONATE

LI

~I1

PRESISURE

. no

.0

.o3

.. x

: .... f

o arn

. 11o

_.isi

m L

LOWERILEUM 1

(150 cm) l

P24 ~ mEq.t unOSM/L

FIG. 1. DISTRIBUTION OF RESULTS IN THE TOTAL GROUPOF FASTING SUBJECTSDotted lines indicate normal values for blood plasma.

894

INTUBATION OF SMALL INTESTINE. IV

TABLE I

Comparison of the sum of the concentrations of thechloride and the bicarbonate anions with the

total fixed base of intestinal contentsCl + HCOsanions Total fixed base

m.eq. per liter m.eq. per liter150 ......... ...... 153145 .. .... 149150 ...... 153148 ...... 150147 ...... 150147 ...... 151151 ...... 155150 ...... 154153 ...... 154150 ...... 152147 ......... ...... 145

base. Gamble and McIver (8) showed a similar agree-ment in pure pancreatic juice. Gilman and Cowgill (9),in a study of relatively pure gastric juice, in which thechloride is the only anion, found that the osmotic pres-sure, as measur~ed by Hill's (10) vapor pressure methodand expressed as milliequivalents, was the same as the

300 we have assumed the fluid to be of approximately thesame osmotic pressure as the blood serum.

RESULTS

1. After fastingThe data on rate of flow, reaction, bicarbonate

concentration and osmotic pressure are repre-sented in a distribution chart (Figure 1). TableII gives results from repeated intubations of asingle individual.

(a) Rate of flow. As indicated in Figure 1the rate of flow for 45 out of a total of 65 fastingspecimens was 2 cc. or less per minute, and inhalf of these it was 0.5 cc. or less. It conformedto the description given by Miller and Abbott(2), being usually slow but extremely irregular.In the same individual on different occasions itwas often more constant. Without exception it

TABLE II

Results from ekven intubations on the same subject (D. M.) in the fasting state

Level Date Intubation Rate of flow pH Chlorides HCOa- Osmotic pressure

1934 number cc. per minute m.eq. per liter m.eq. per liter mOsM. per literDuodenum April 23 III A 2.5 5.74 50.8

April 23 III B .88 5.52 75.4 5.8 162April 23 III C .76 5.93 85.6 21.1 214May 3 IV 1.42 4.70 93.4 4.3 196July 18 VIII A 62.4 6.3 138September 6 IX .37 6.50 132.6 5.1 276September 13 X .48 6.04 102.4 4.0 213

Jejunum (60 cm.) June 1 VI 1.00 7.03 116.4 5.8 244

Upper ileum (90 cm.) March 19 II A 6.10 128.6 2.3 262

Middle ileum (120 cm.) March 19 II B .40 7.05 132.6 6.5 278March 19 II C 1.05 7.21 126.0 20.1 292March 13 I .58 6.77 123.1 15.0 276May 22 V .72 7.15 101.0 17.8 238July 9 VII A .68 114.0 35.6 299July 9 VII B .18 104.6 39.8 289July 18 VIII B .28 127.0 3.9 262

Lower ileum (160 cm.) September 20 XI A .28 7.16 123.9 10.4 269September 20 XI B 5.8 7.21 128.2 16.5 289September 20 XI C .47 7.31 127.6 17.0 289

chloride concentration found by analysis. Darrow andHartmann (11) have determined that the calculated os-motic pressure of blood serum agrees very well withthat determined by freezing point lowering, and that itapproaches 300 milliosmoles per liter.

We have, therefore, as a sufficient approximation ofthe osmotic pressure of fasting intestinal contents, multi-plied the sum of the chloride and bicarbonate anions, ex-pressed as milliequivalents per liter, by two, and desig-nated this figure as milliosmoles. When it approaches

was intermittent, being sometimes rapid for awhile then followed by complete cessation for anunpredictable interval. The few continuing highrates of flow, mostly from the ileum, since theywere obtained on individuals who complained ofmild abdominal distress, were due undoubtedlyto an increased gastro-intestinal motility. Irre-spective of the location from which aspiration was

895

W. G. KARR AND W. OSLER ABBOTT

taking place, collections of gas appeared inter-spersed between columns of fluid. The materialin its gross appearance conformed, with slightvariation, to the description of Miller and Abbott(2), being a somewhat viscid fluid, of amber togreenish color, and it usually contained fine flecksof mucus and other debris which settled onstanding.

(b) Reaction. The pH was very variable,ranging from 2.64 to 7.80. There was a tendencyfor the contents to become more alkaline lowerin the intestine, though distinctly acid specimens(pH 4.8) were occasionally recovered even fromthe ileum.

(c) As would be anticipated from the widerange of pH, the bicarbonate concentration wasvariable, our extremes being 1.3 and 45.5 m.eq.per liter.

(d) Osmotic pressure. The contents, espe-cially from the upper intestinal tract, were often

TABLE III

Concenitrations of calcium, nitrogen and phosphorus inthe intestinal contents of fasting subjects at

various levels

Distance beyond Calium Total Totalthe pylorus phosphorus nitrogen

cm. mgm. per 100 cc. mgm. per 100 cc. mgm. per 100 cc.

Duodenum... 12.4Duodenum ... 5.5 61Duodenum ... 4.7 33

30 6330 ......... 8.030 ......... 5.2 10.0 5630 ......... 5.6 13.230 ......... 11.6 7.130 4560 ......... 12.8 7.2 4560 ......... 5.4 7.3 7360 ......... 8.060 5560 ......... 5.8 7.1 5090 109*90 ......... 5.490 ......... 5.2 5.9 5490 4090 7.190 4.5

120 ......... 12.8 200*120 ......... 5.0 6.3 53120 ......... 5.8 7.3120 4.5120 4.7 86150 ......... 5.0 6.3 53150 ......... 9.8 34150 45

Average .. 7.7 6.8 53

* Not averaged.

hypotonic as compared with blood plasma. Intheir passage down the tract, however, isotonicitywas usually attained, but never exceeded. Thechloride concentration was in reciprocal relation-ship with the bicarbonate content, thus maintain-ing the osmotic pressure. The chloride rangedfrom 50.6 to 150.6 m.eq. per liter (296 to 880mgm. NaCl per 100 cc.).

(e) Calcium, phosphorus and nitrogen. Thecalcium concentration was usually below the nor-mal blood level. A few analyses indicated thatpractically all of the phosphorus was in the in-organic form, its concentration was usually abovethat of blood plasma. Both calcium and phos-phorus tended to be more concentrated in theupper. intestine. As the few analyses indicatedthat about one-half of the total nitrogen was pre-cipitable by zinc hydroxide, the fasting proteincontent was very low.

2. After hydrochloric acid and sodium bicar-bonate administration

When hydrochloric acid solution (0.16 N),isotonic with blood plasma, was introduced intothe stomach by tube in 50 cc. quantities the re-sultant influence on the chemistry of the intestinalcontents at various levels is shown in Figure 2.Hydrochloric acid of this concentration is appar-ently held in the stomach, and released into theintestine in small quantities so that neutralizationis rapidly attained. No immediate inc'rease inrate of flow was observed, but in two cases anincrease occurred about one hour after giving theacid. No decrease in the pH but rather a tend-ency to an increase was noted, showing that thealkaline intestinal fluids are present in excess.Isotonicity with the blood plasma was maintained.

The response to isotonic sodium bicarbonate so-lution was in marked contrast to that which fol-lowed the administration of isotonic hydrochloricacid (Figure 3). The bicarbonate left the stom-ach very rapidly as is shown by the immediate in-crease in the rate of flow, in the bicarbonate con-tent and in the alkalinity of the intestinal contents.Sodium bicarbonate in 5 per cent solution also leftthe stomach relatively rapidly. That it was notheld until isotonicity was established is indicatedby the osmolar concentration of the intestinal fluidrising appreciably above 300 milliosmoles. When

896

DUODENUM 120 CM. 150 CM.

_____ ,50CC. 50C 50CC. socc. 0oCC CC

15.RATEOF FLOW

I0CC./MIN.

HCO3 s030

7.0 d

pH 6.0

5.0

OSMOTIC 400PRESSURE30-

mOML./L no.

I ~ ~~ ~|31 H6UAS'I0

|O*FIG. 2. CURVESTO SHOWTHE EFFECTS OF THE ORAL ADMINISTRATION OF ISOTONIC HYDROCHLORIC

ACID SOLUTION (0.16 N) ON THE CONTENTSOF THE DUODENUMANDOF THE ILEUM (120 AND 150 CM.BELOWTHE PYLORUS).

Dotted lines indicate normal values for blood plasma. Arrows indicate time of administration.

FIG. 3. CURVESTO SHOWTHE EFFECTS OF THE ORAL ADMINISTRATION OF ISOTONIC AND HYPERTONICSOLUTIONS OF SODIUM BICARBONATEON THE CONTENTSOF THE INTESTINAL TRACT

Dotted lines indicate normal values for blood plasma. Solutions were administered at zero time.

W. G. KARR AND W. OSLER ABBOTT

in a single experiment a stronger solution of so-dium bicarbonate (10 per cent) was given it wasretained by the stomach until diluted. This isdefinitely indicated by the absence of an appreci-able increase in the bicarbonate ion of the duodenalfluid. In the latter instance, furthermore, bicar-bonate was present in the stomach three and one-half hours after its administration, in contrast tosome experiments with isotonic bicarbonate solu-tion in which the gastric juice again became acidwithin thirty minutes.

3. After waterThe data obtained on specimens from three dif-

ferent levels in the intestine after the subject haddrunk 400 cc. of water are plotted in Figure 4.

25C 60 120 CM400 CC. 400CC. 400CC.

30mECFFLOWzo.CC. /MIN. /0

HCO3 J4I30

mEq. /L.

&pH

44

OSMOTIC - ;---PRESSUREII

FIG. 4. CURVESTO SHOWTHE EFFECTS OF THE ORALADMINISTRATION OF WATERON THE CONTENTSFROMFIVEFASTING SUBJECTS.

Each subject is represented by a different type of line.The water was administered at zero time.

In four out of five cases, as shown by the promptincrease in the rate of flow, the water left thestomach rapidly. With this sweeping out of thebasal acid secretions of the stomach the pH of theintestinal fluid decreased. The osmotic pressure

of the fluid also was lowered until approximateequilibrium was established after a variable in-terval. In one case in which only a slightly in-creased rate of flow occurred within the first halfhour, the influence of the alkaline intestinal fluidpredominated as indicated by the increase in bi-carbonate, the higher pH and the maintenance ofisotonicity.

DISCUSSION

The data covered in this report are based en-tirely on a chemical study of intestinal contentsas they normally occur and not of pure intestinalsecretion. Chemical analyses of intestinal juicesper se, without an admixture of substances fromabove, secured by the use of a three-lumeneddouble-ballooned apparatus (12) that allows thefluid to be collected from an isolated segment ofbowel, will be reported separately by Abbott andKarr (13).

Since the contents at any one point are a mix-ture of saliva, gastric juice, bile, pancreatic secre-tion and succus entericus originating above thepoint of collection, the composition depends pri-marily upon the ingredients of these separate se-cretions and secondarily upon the chemical reac-tions that occur among them. Gastric juice ishypotonic with respect to blood plasma. The acidgastric juice enters the duodenum and there comesin contact with secretions of alkaline reaction andof isotonic composition (8). The fasting con-tents of the small intestine beyond the duodenumare essentially a mixture of two fluids, gastricand duodenal, and they have a tendency to assumethe characteristics of whichever may predominateat the time.

The great variation in the pH of the fasting in-testinal contents is associated with a marked varia-tion in the motility of the stomach and the intes-tine and, to a less extent, with a variation in theacidity of the fasting stomach contents and inthe amount of pancreatic secretion. If the acidgastric juice while fasting leaves the stomach rap-idly and is carried down the intestine by activeperistalsis, the pH at any level tends to be low.If the progress of the contents is slower, completeneutralization occurs and sometimes, when intes-tinal secretions are in excess, an alkaline reactionresults. Roentgenological examination supports

898

INTUBATION OF SMALL INTESTINE. IV

this relationship to motility. Such observations asapply to the duodenum are in keeping with theresults of many similar studies previously madeon man. With regard to the jejunum and ileum,only McClendon and his associates (14) have re-corded the reaction in intact subjects, none ofwhomwas in the fasting state. The most nearlycomparable studies on animals are those of Mannand Bollman (15), who have showed in fistuladogs that the reaction of the intestinal contentvaries approximately in the same manner as thatreported in this paper.

The studies of osmotic pressure of the intes-tinal contents show a wide variation from hypo-tonicity to practical isotonicity with the bloodplasma. Two factors tend to produce a low os-motic pressure in the duodenum: the presence ofhypotonic solutions from the stomach and neutral-ization. The following equation shows the neu-tralization of isotonic hydrochloric acid by isotonicsodium bicarbonate:

carbonate greatly in excess of its concentrationin the blood plasma.

The chief function of the chloride ion in itsreciprocal relationship to the bicarbonate ionwould seem to be that of maintaining osmoticpressure. That it is present in the intestinal fluidin greater concentration than in blood plasma maynot indicate a specific secretory action of the in-testinal wall but rather an equilibrium of the onlyanion available to maintain osmotic pressure.

It is fully realized that the presence in the in-testinal tract of the tube and the inflated balloonmay disturb to some extent its normal chemicalphysiology. The variations in the chemical dataon an individual intubated on different occasions,however, would seem to be due to functionalvariations beyond control and occurring in spiteof the fact that the apparatus always, in our work,has been introduced and maintained under con-stant conditions.

SUMMARY

HC1 NaHCO. NaC (1) A technique of intubation which makes1 L + L _ 2 L + CO2 practical the recovery of contents from approxi-

160 m.eq. 160 m.eq. - 80 m.eq. (absorbed) mately any desired portion of the intact humanper liter per liter per liter

small intestine has been employed in a study ofThe carbon dioxide is very readily absorbed (16) the chemical characteristics of the normal boweland the resultant state of hypotonicity persists under varying conditions.until equilibrium is established by the absorption (2) Under fasting conditions it has been dem-of water or the diffusion of salt into the fluid. onstrated (a) that the flow of contents into anyIn any event osmotic equilibrium is usually at- part of the small intestine is usually less than 1tained, although if motility is very rapid, fluids cc. per minute; (b) that the acidity of the con-with an acid pH and a low osmotic pressure may tents is greatest in the duodenum, diminishingbe found in the lower small intestine. When the gradually toward a neutral or even a slightly alka-motility is slow the fluids are neutral or alkaline line reaction in the lower ileum; (c) that the bi-and isotonic with blood plasma. carbonate concentration is related to the reaction

The bicarbonate content obviously varies with of the contents, and (d) that the duodenal con-the hydrogen ion concentration. When the in- tents if acid and in the process of neutralizationtestinal pH is in the neighborhood of 7.4 the bi- are uniformly hypotonic, but that if neutral orcarbonate content often approximates that of alkaline they approach closely the osmotic stateblood plasma. Variations are probably due to of the ileal contents which are essentially ingreater variations in the carbon dioxide tension. equilibrium with the blood plasma.How much of the bicarbonate for neutralization (3) After the oral administration of a solutioncomes from the pancreatic juice and how much of hydrochloric acid isotonic with the body fluids,through the intestinal wall is unknown. In the the contents of the stomach usually pass slowlyduodenum the pancreatic bicarbonate is probably into the duodenum, where they are completelythe more important factor. In intestinal seg- neutralized by the bicarbonate content of the lat-ments which have been blocked off, however, as ter and attain osmotic equilibrium with the body.will be shown in a subsequent presentation (13), (4) After the administration of an isotoniccertain stimuli may provoke a secretion of bi- solution of sodium bicarbonate, a very rapid evac-

899

W. G. KARR AND W. OSLER ABBOTT

uation of the stomach occurs; but after a 5 per

cent solution, the discharge is less rapid thoughstill sufficient to produce distinctly alkaline andhypertonic duodenal and intestinal contents. Af-ter a 10 per cent solution, however, gastric reten-tion occurs to such an extent that within twohours no increase in the bicarbonate content or

alkalinity of the duodenal contents can be demon-strated.

(5) After the administration of 400 cc. of wa-

ter, the gastric contents pass into the duodenumwith sufficient rapidity to render the intestinalfluids acid, and to lower their osmotic pressure.

BIBLIOGRAPHY

1. Miller, T. G., and Abbott, W. O., Intestinal intuba-tion: A practical technique. Am. J. M. Sc., 1934,187, 595.

2. Miller, T. G., and Abbott, W. O., Small intestinalintubation: Experiences with a double lumenedtube. Ann. Int. Med., 1934, 8, 85.

3. Wilson, D. W., and Ball' E. G., A study of the esti-mation of chloride in blood and serum. J. Biol.Chem., 1928, 79, 221.

4. Van Slyke, D. D., and Stadie, W. C., The determina-tion of the gases of the blood. J. Biol. Chem.,1921, 49, 1.

5. Meeker, G. H., and Oser, B. L., Titrametric doublehydrogen or quinhydrone electrode systems forhydrion determination; applications to urine andblood. J. Biol. Chem., 1926, 67, 307.

6. Clark, E. P., and Collip, J. B., A study of the Tisdallmethod for the determination of blood serum cal-

cium with a suggested modification. J. Biol.Chem., 1925, 63, 461.

7. Fiske, C. H., and Subbarrow, Y., The colorimetricdetermination of phosphorus. J. Biol. Chem., 1925,66, 375.

8. Gamble, J. L., and McIver, M. A., Acid-base com-position of pancreatic juice and bile. J. Exper.Med., 1928, 48, 849.

9. Gilman, A., and Cowgill, G. R., Osmotic relationsbetween blood and body fluids. II. The osmoticrelation of blood and gastric juice. Am. J. Phys-iol., 1933, 103, 143.

10. Hill, A. V., A thermal method of measuring thevapour pressure of an aqueous solution. Proc.Roy. Soc. London, 1930, A127, 9.

11. Darrow, D. C., and Hartmann, A. F., A comparisonof the calculated and determined osmolar con-centration of normal serum. Am. J. Dis. Child.,1929, 37, 51.

12. Abbott, W. O., and Miller, T. G., Intubation studiesof the human small intestine. III. A technique forthe collection of pure intestinal secretion and forthe study of intestinal absorption. J. A. M. A.(In press.)

13. Abbott, W. O., and Karr, W. G., Unpublished results.14. McClendon, J. F., Bissel, F. S., Lowe, E. R., and

Meyer, P. F., Hydrogen ion concentration of thecontents of the small bowel. J. A. M. A., 1920,75, 1638.

15. Mann, F. C., and Bollman, J. L., The reaction of thecontent of the gastro-intestinal tract. J. A. M. A.,1930, 95, 1722.

16. McIver, M. A., Redfield, A. C., and Benedict, E. B.,Gaseous exchange between the blood and the lu-men of the stomach and intestines. Am. J. Phys-iol., 1926, 76, 92.

900