Mechanisms of edema formation

Mechanisms of edema formation

Editorial Mechanisms balance of The of veniently fluids mechanisms years Formation the body and of the distribution of the EGULATION R of...

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Editorial Mechanisms

balance

of

The

of

veniently

fluids

mechanisms years

Formation

the body and of the distribution

of the

EGULATION

R

of Edema

within which

have

water

the

body

investigations

disclosed

involves

component ponents

complex

may be regarded

as divided

into

comprising

of the body weight,

of recent

to be more

body water

comprising

con-

an intracellular

about

45 per cent

and extracellular about

com-

25 per cent

of

than was previously supposed. The results of some of these studies have been summarized recently in two lucid and informative reviews. lr2

the body weight. Of the extracellular portion, about 80 per cent normally is found in the interstitial fluids and 20 per cent is contained within the walls of the vascular

Water normally constitutes about 70 per cent of the adult body weight and this proportion ordinarily is maintained with remarkable efficiency by a balance between total water intake and output. Of the aver-

bed. The interstitial and the intravascular fluids are in dynamic equilibrium, with a constant interchange of water, electrolytes and, non-electrolytes across the capillary membrane. In edema, the regulation of this

age

equilibrium

daily

total

intake

of 2,400

Gm.

of

is disturbed

and an excessive

water, about half is taken as water or other beverage, 900 Gm. as preformed water of

amount

food

Sunderman has divided the various causes of edema into the following categories:

and

300

Gm.

is water

cellular

of oxidation

formed in the body during the metabolism of foodstuffs. Of the average daily total . output, about 1,300 Gm. of water are excreted in the urine, 200 Gm. in the stools

able by ordinary

methods

(as in overadministration of salt, adrenal cortical and gonadal hormones) ; (C) reduction of colloid osmotic pressure (hypoproteinemia) due to inadequate protein intake, impaired synthesis of serum albumin or excessive loss of proteins through

and is not con-

bedside

practice

or other

of

tion

out the fallaciousness of such which so often give dis-

crepant results even if apparently twenty-four hour urine specimens

complete have been

OF

MEDICINE

general

the kidney or

local

to veins) ; (E)

blockage

of lymphatic

has resolved itself largely into analysis of the factors influencing the exchange of water, electrolytes and non-electrolytes across the capillary wall and of those regulating glomerular filtration and tubular reabsorption of water. The hydrostatic pressure

and dehydration. Am. j’. Clin. Path., 16: 353, 1946. 2 ABBOTT, W. E. A review of the present concepts of fluid balance. Am. 3. M. SC., 211: 232, 1946. JOURNAL

(D)

return of protein-containing tissue fluid. Investigation of the mechanisms of edema

collected. Daily measurement of the body weight usually gives a more satisfactory approximation of gross positive or negative fluctuations in water balance. 1SUNDERMAN, F. W. Approaches to the study of edema

AMERICAN

channels;

increases in capillary blood pressure (congestive cardiac failure or mechanical obstruc-

estimating water balance by comparison of urinary output with fluid intake. Sunderman points comparisons,

in the inter-

spaces.

(A) primary retention of water (water intoxication); (B) primary retention of salt

and 900 Gm. are lost through the skin and lungs (“insensible loss”). It will be noted that a large proportion both of the water taken in and excreted is not readily measursidered in the common

of fluid accumulates

within

the capillary

bility of the capillary 313

bed and the permeamembrane

are impor-

314

Editorial

tant factors

in the movement

vascular channels The

colloid

albumin

osmotic

and

of fluid from

into the interstitial

the

pressure

spaces.

of

tissue tension

serum

of subcu-

taneous elastic tissue are the most significant forces in maintaining fines of the capillary Starling’s

concept

between

hydrostatic

pressures

effecting

fluid within

the con-

bed. colloid

a filtration

osmotic

balance

in this relation.

at

In a study

of

famine edema, which reappeared on a large scale in World War II, Keys placed thirtyfour volunteers for six months on a semistarvation diet of whole cereals, potatoes, turnips,

etc.,

providing

an

average

of

49 Gm. of protein daily. The subjects developed typical famine edema resembling that

observed

in certain

war areas.

diminution

They

of heart

size,

and no rise in plasma

protein nitrogen

or chloride.

previous observations,

no

non-

In accord with

there was no indica-

tion that edema was due to renal or cardiac failure, the venous pressure, in fact, being Thiamine

out by analyses

the capillary wall has been borne out, in general, by clinical investigation and animal experiment. The recent work of Keys and his associates,3 however, has disclosed discrepancies

and

hepatomegaly

reduced.

of a simple equilibrium and

cardia

An unexpected ever,

was

deficiency

was

ruled

of food and excreta.

the

result of this study, howfinding

that,

contrary

to

earlier observations, the development of edema was accompanied by only a slight decline in the concentration of plasma proteins, averaging 0.73 Gm. per 100 cc., and by no marked hypoalbuminemia. The slight degree of hypoproteinemia or lowered colloid osmotic pressure in the plasma observed clearly could not account for the appearance

of marked

edema.

The

dis-

crepancy was all the more striking because it was noted consistently in the subjects of this carefully controlled experiment. Keys interpreted his data to indicate

lost an average of one-fourth of their body weight and became “waterlogged,” with a relative excess of sixteen pounds of extracellular water per man. Like the victims of

that the fluid balance between blood plasma and interstitial fluid does not reflect a simple equilibrium of the kind generally postulated.

starvation abroad, the experimental subjects also showed marked polyuria, brady3 KEYS, A., TAYLOR, H. L., NICKELSEN, 0. and HEN-

equilibrium

SCHEL, A. Famine edema and the mechanism formation. Science, 103: 669, 1946.

of its

He concludes implies

that there is a dynamic state of the capillary

transfer

endothelium

activities

of

non-

wall and the

lining

which have yet to be clarified. A. B. G.

AMERICAN

JOURNAL

OF

MEDICINE