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NORMAL
ELECTROLYTE VALUES IN AN ADULT NIGERIAN POPULATION
ABSTRACT
Serum levels
of sodium, potassium and chloride were determined in fifty Nigerian adults
(thirty males and twenty females). Sodium and potassium was determined by flame
photometry while chloride was determined by modified scales and scales method.
The mean values were as follows: Sodium = 137.0 MEq/L, Potassium
= 3.9 MEq/L, Chloride =
105.0 MEq/L. There were
no significant (
)
differences on the values obtained with sex, nor was there any significant
difference between values obtained for the different age groups. The results
obtained in the present study compares favorably with result from similar
studies carried out on Africans. Compared to non-Africans, the results from the
present study are somewhat lower, and the possible causes are explained.
TABLE OF CONTENTS
Title
Page - - - - - - - - - - i
Declaration - - - - - - - - - ii
Dedication - - - - - - - - - iii
Acknowledgement - - - - - - - - iv
Abstract - - - - - - - - - - v
Table
of Contents - - - - - - - - vi
List of Tables - - - - - - - - - vii
List of
Figures - - - - - - - - - viii
CHAAPTER ONE: INTRODUCTION
AND LITERATURE REVIEW
1.1
Introduction
1.2
Regulation
of E.C.F. Electrolyte
1.3
Law
Concentrations
1.4
The
Concept of Electrolyte Balance
1.5
The
Concept of Determining the “Normal” Value
1.6
Literature
Review
CHAPTER TWO: MATERIALS
AND METHODS
2.1 Study Area and Criteria
2.2 Collection of Blood Samples
2.3 Estimation of Electrolyte Concentration
CHAPTER THREE:
RESULTS
3.1 Results
3.2 Determination of the Range for “Normal”
Values
3.3 Effect of Sex on Electrolyte Distribution
3.4 Effect of Age on Electrolyte Distribution
3.5 Comparison of Results of Present Study with
Result of Similar Studies
CHAPTER FOUR: DISCUSSION
AND REFERENCES
4.1 Discussion
References
Appendices
i.
Analysis
of Electrolyte Values in a Nigerian Adult Population University of Port
Harcourt, Choba and its Vicinity with Age, Sex, Mean Values and Standard
Deviations.
ii.
Student’s
t – Distribution Table
LIST
OF TABLES
Table I: Age and Sex Distribution of
Subjects
Table
II: Mean Values, Range and
Standard Deviation of the Electrolytes
Table
III: Normal Values for Serum
Electrolytes at 95% Confidence Limit.
Table
IV: Mean Serum Sodium Levels for
Different Age-Groups in Males and Females
Table
V: Mean Serum Potassium Levels
for Different Age-Groups in Males and Females
Table
VI: Mean Serum Chloride Levels
for Different Age-Groups in Males and Females
Table
VII: Mean Electrolyte Distribution
According to Age Groups
Table
VIII: Mean Sodium Levels for Age
Groups and for the Present Study
Table
IX: Mean Potassium Levels for Age
Groups and for the Present Study
Table
X: Mean Chloride Levels for Age
Groups and for the Present Study
Table
XI: Serum Electrolytes in Present
Study Compared with Similar Studies of African Populations
Table
XII: Serum Electrolytes in Present
Study Compared with Similar Studies of Non-African Populations.
LIST OF TABLES
Figure
1: Effect of Blocking the Adh-Thirst
Feedback System on Plasma Sodium Concentration
Figure
2: Effect of Blocking the
Aldosterone System on Plasma Sodium Concentration
Figure
3: Effect of Blocking the
Aldosterone System on Plasma Potassium Concentration
Figure
4: Simple Bar Chart Representation
of Mean Serum Sodium Level for the Different Age Group
Figure
5: Simple Bar Chart Representation
of Mean Potassium Level for the Different Age Group
Figure
6: Simple Bar Chart Representation
of Mean Chloride Level for the Different Age Group
Figure
7: Multiple Bar Chart Representation
of the Mean Serum Levels of Sodium, Potassium and Chloride for the Different
Age Groups.
CHAPTER ONE
INTRODUCTION AND LITERATURE
REVIEW
1.1 INTRODUCTION
The
determination of serum/plasma levels of the various electrolytes in the body
now constitutes a major and routine procedure in clinical chemistry
laboratories, as well as being subject of increasing research interest. Clinical
requests for electrolyte determination are based on the fact that a constant
biochemical environment must be maintained by the body of healthy individuals
to maintain a state of electrolyte equilibrium. Should the levels of plasma
electrolytes be markedly altered from the normal, this condition indicates that
there will be disturbance of certain physiological processes in the body, as
well as shifts of electrolytes between compartments of body fluids. Thus in the
ideal state, the total amount of electrolyte lost each day should be equal to
the total amount gained; a state of electrolyte derangement arises if this
equation does not occur.
The
metabolism of body electrolytes, especially in developing countries, constitute
an important aspect of physiological and clinical studies, but most of the data
available to show the “normal” biochemical values of such electrolytes in these
countries often to differ significantly from the values obtained is other
developed countries.
This
disparity has led to great interest in investigating what should be regarded as
the normal values for these electrolytes in these developing and tropical
countries, and comparing these values with what is accepted as normal in
temperate countries.
The electrolytes of the body are distributable
into both the extracellular and the intracellular fluid compartments. In the
cells, the most important electrolytes are potassium, mapnesium, phosphate,
sulphate, bicarbonate and small quantities of sodium, chloride and calcium. These
electrolytes are dissolved in the water of the protoplasm, providing inorganic
chemicals for cellular reactions, as well as being essential in the operation
of some the cellular control mechanisms including the determination of
different enzymatically catalyzed reactions necessary for cellular metabolism
and also facilitating the electrochemical transmission of impulses in nerve and
muscle fibres.
In
the extracellular compartment, however, the major electrolytes are sodium
chloride, calcium and small quantities of potassium, magnesium phosphate etc.
It is not easy to measure the concentration of intracellular electrolytes; this
being possible only by indirect determination, but the composition of the ECF
may be studied using the blood plasma obtained from subjects.
Some
of the electrolytes are excreted in urine, and often this body fluid is used in
assessing the quantity of the electrolytes in the body, but obviously it is an
imperfect method because since the amount secreted will vary widely within
individuals and even within the same subject. The reason is that there are many
variables controlling the amount of electrolytes excreted at any particular
time.
1.2 REGULATION OF ECF ELECTROLYTE
CONCS.
The
extracellular fluid sodium concentration determines the osmolality of the ECF
as well as ICF (both being in Osmotic equilibrium) since sodium is by far the
most abundant cation in the ECF. Also the acid-base control mechanism adjusts
the anion concentrations of the body fluids to equal those of the cation.
Sodium exerts this Osmolar effect through two control systems:
i.
Osmo-sodium receptor (osmo-receptors)
– Anticliuretic Hormone Feedback Control Mechanism.
In
this mechanism, increased osmolality excites the osmo-receptor located in the
supraoptic nucleus causing release of antidiuretic hormone. This hormone
increases the permeability of the collecting waters reabsorption, which leads
to increased water retention without concomitant increased sodium retention.
This corrects the initial high osmolality of the ECF. Conversely, if the ECF is
hypo-osmotic, less ADH is produced leading to increased loss of water thus
concentrating the body fluid back to normal.
ii.
Thirst
This
is based on the balanced intake and output of water each day. Conscious desire
for water is generated in a small area in the lateral periotic area of the
hypothalamus called the thirst center is intracellular dehydration, caused by
high osmolar ECF drawing water from the thirst center which causes sensation of
thirst, leading to increased water drinking thus tending to read just the
osmolality towards normal. It would appear that the combined role of ADH-Thirst
mechanisms regulates sodium concentration in the body.
|
40 80
120 160 200
|
|
Plasma Sodium Concentration MEq/L
|
|
152
148
144
140
136
|
|
Normal
|
|
0
|
|
Sodium Intake (MEq/Day)
|
ADH-Thirst System
Blocked
In addition, aldosterone and other
mineralocorticoids are known to play a small role in the control of
extracellular sodium concentration. By far the most import effect is to
increase the rate of tubular reabsorption of sodium. By micro-puncture
techniques, it has shown that aldosterone has an especially potent effect in
increasing sodium reabsorption all along the renal tubule. Thus an increased
aldosterone level in the body tends to decrease the daily loss of sodium in the
urine.
Although the effect of increased
aldosterone is to increase the quantity of sodium in the extracellular fluids,
significant hypernatremia does not usually occur because the subject become
extremely thirsty and keep adding more water to his body fluid thus diluting
the sodium concentration appreciably and thereby maintaining almost normal.
Thus aldosterone is regarded as only playing but a minor role in controlling
extracellular fluid sodium concentration. It is thus paradoxically that
aldosterone should cause sodium retention and at the same time maintain the
sodium concentration.
|
40 80
120 160 200
|
|
Plasma Sodium Concentration MEq/L
|
|
150
140
130
120
110
100
|
|
Normal
|
|
0
|
|
Sodium Intake (MEq/Day)
|
|
Aldosterone
System
Blocked
|
This increased reabsorption of sodium
also causes hydrogen ions to be secreted into the tubules and lost in urine,
leading to alkalosis. This change in body pH is not excessive however, and
ordinarily can be adequately compensated by the normal acid-base regulatory
mechanisms.
Aldosterone mechanism plays a very
powerful role in the control of extracellular potassium by enhancing its
secretion into the distal tubeless and collecting tubules of the kidney. This
is caused mainly by the extreme electronegativity created in the tubules by the
exit of sodium ions. Thus large amounts of potassium are excreted from the body
fluid through urine.
|
40 80
120 160 200
|
|
Plasma Potassium Concentration MEq/L
|
|
4.8
4.6
4.4
4.2
4.0
|
|
Normal
|
|
Potassium Intake (MEq/Day)
|
Aldosterone
System
Blocked
In
primary aldosteronism, caused by tunour of the glomerulosa of one of the
adrenal glands, the excessive aldosterone secreted results in severe decrease
in the extracellular fluid potassium concentration that the patient experiences
paralysis caused by failure of nerve transmission of impulses, resulting from
hyperpolarization of the nerve membranes. Conversely in addition disease the
potassium level is so high that it can frequently cause cardiac death resulting
from cardiac arrhythmias that can lead to cardiac fibrillation.
Aldosterone
also causes a greatly enhanced reabsorption of anions especially chloride ions.
The reason is exactly the opposite to the effects on potassium and hydrogen
ions. The chloride ions are repelled from the electronegative tubular fluid and
are attracted towards the extracellular fluid. In this way, the total quantity
of sodium chloride in the body fluid increase under the stimulus of
aldosterone.
Loss
of adrenocortical secretion usually causes death within two weeks unless the
patient receives adequate salt or mineralocorticoid therapy. Without this, the
potassium and hydrogen ion concentration in the extracellular fluid becomes
markedly high, the sodium and chloride concentration decrease and the total
extracellular fluid volume and blood volume also become greatly reduced.
1.3 LAW OF ELECTRO-NEUTRALITY
An
important law of electrolyte solutions is the “Law of Electro-neutrality” which
requires that the sum of positive charges on the cations in any solution must
be equal to the som of the negative charges on the anions. One consequence of
this principle is that methods for determining the total concentrations of the
metallic cations (Na+,
K+,
Ca++
and Mg++)
in the plasma, do in fact measure the total concentration of base, only they do
so indirectly by estimating the cations whose total concentrations must be the
same. Moreso, as Barker and Elkinton (1958) pointed out the concept of “buffer
base” which Singer and Hastings (1948) proposed to describe the acid-base
status of the blood becomes even more valuable if the “buffer base” is regarded
as the total concentration of buffer anions, rather than as the concentration
of the unspecified cations which balance their negative charges.
In
human, the major electrolytes in the plasma are Sodium (Na+),
Potassium (K+),
Chloride (Cl-),
Bicarbonate (HC03) and Protein
(Pr-).
If the concentrations of these ions are measured, the principle of Ionic
Equality requires that the concentration of the cations should match that of
the anions. Any deviation from this state of ionic equality results in a chain
of events aimed at returning the state of this body to electro-neutrality but
this may result in widespread loss of electrolytes. By selectively excreting
excess ingested inorganic ions which are surplus to the body and maximally
retaining deficient ions, the kidney maintains the body in electrolyte balance.
Sodium
is the principal cation of the Extracellular Fluid (ECF) compartment whereas
potassium predominates in the Intracellular Fluid (I.C.F.). Conversely, in the
ECF, potassium is only little, just as is sodium in I.C.F. while chloride is an
important anion in ECF, phosphate and sulphate are found mainly in the cells.
These
differences between ECF and ICF are extremely important to the life of the
cell. The differences by ionic composition between I.C.F and E.C.F depend on
two main mechanisms: the inability of large molecules to pass freely across the
cell membranes and the Active Transport of substances across the cell
membranes. These various transport mechanism e.g. the sodium – potassium pump,
require the expenditure of energy. Thus the integrity of the cell membrane and
a sufficient supply of energy determine the differences and changes in
composition between the two compartments is Osmosis of water, resulting from
differing osmolality of the two compartments. In this, fluid mainly water, move
from one compartment of low osmolality to the other of higher osmolality in a
bid to bring the two compartments to the same osmolality.
The
total amount of sodium and potassium in the body may be estimated by chemical
analysis of cadavers. It may also be estimated by dilution techniques with
radioactive isotopes
and
. Since the latter isotope occurs
naturally as a constant proportion of the total potassium, the body potassium
may be estimated by total body scanning of the isotope. The estimation of total
body sodium by dilution technique gives a figure 17% lower than that obtained
by chemical analysis because only one third of the total amount of sodium is
immediately exchangeable. The other is fixed in bones and has a long turnover
time.
The
determination of Na and K levels in plasma has nowadays been made simple and a
routine clinical procedure with the advent of flame emission spectrophotometry.
Plasma is separated from the blood cells as soon as possible after collection
of the blood sample. The plasma is diluted with lithium nitrate and the
solution is sprayed into a flame. The resultant increases in the yellow colour
due to Na and violet colour due to potassium are compared with the constant
emission in the red part of the spectrum given by the lithium. All electrolytes
are obtained from diet, principally food, though drinking water may supply
small amounts of some ions. Losses of electrolytes in a temperate climate are
in faces, sweat and in urine.
Water
can be removed from the body by evaporation from the skin, evaporation from the
lungs, excretion of vey dilute urine or, in cases of severe water loss and
electrolyte derangement which follow diarrhea and vomiting. In all these
conditions, water leaves the extracellular fluid compartment, but on doing so
some of the intracellular water pass immediately into the extracellular
compartment by osmosis in an attempt to keep the osmolality’s of both
compartments equal. The overall effect is called dehydration, an intravenous
infusion of the appropriate solutions is normally required, and for effective
rehydration, an accurate knowledge of normal electrolyte volumes is of extreme
importance.
If
an isotonic solution is added to the extracellular fluid compartment, the
osmolality of the extracellular fluid does not change, on osmosis occurs and
the only effect is an increased extracellular fluid volume. However if a
hypertonic solution is added, the osmolality of the internal environment
(extracellular fluid) increases and causes osmosis of water out of the
intracellular fluid compartment to the extracellular compartment. If, on the
other hand, a hypotonic solution is added, the osmolality of the extracellular
fluid decreases and fluid pass into the cells.
On
this principle, very concentrated glucose, manitol or a sucrose solution are
often administered into patients to cause immediate decrease in intracellular
fluid volume. This principle is used, for example, in severe cerebral oedema,
where the patient could die of too much pressure in cranial vault, which
obstructs the flow of blood to the brain. This procedure is of temporary
benefit because the substances are either soon excreted or metabolized, but
within the two to four hours of its osmotic activity, the lift of a dying
patient could be saved.
1.4 THE CONCEPT ELECTROLYTE (CATI0N-ANION) BALANCE
Combined
functions of the buffer system of blood, respiratory system and renal mechanism
are of great importance in maintaining the normal composition cations and
anions of the body to maintain electrical neutrality. This electrical
neutrality is maintained at all times – increase in one anion is accompanied by
a corresponding decrease in some other anion or by an increase in cation, so
that the neutrality is hardly altered.
Plasma
has a volume of 1300 – 1800 ml/sq.m of body surface and constitutes 5% of the
body weight. Until now, it was not possible to explain the unequal distribution
of most electrolytes between ICF and ECF in terms of physic – chemical theories
of diffusion. The Gibbs – Donnan Equilibrium has successfully explained the
unequal distribution of chloride and bicarbonate between red cells and the
plasma. Van Slyke et al (1923) has shown that higher chloride and bicarbonate
content of plasma is due to the presence of the negatively charged
non-diffusible hemoglobin inside the red cell, in accordance with the Gibbs –
Dannan Equilibrium.
The bicarbonate buffer system regulates
the pH of the body. If the body level of hydrogen ions (
) is high, more bicarbonate
converts to hydrogen bicarbonate
:-
+
HH
If
the add base
H H
+
+
0
In
this way the pH of the body is adequately buffered. Of clinical interest in
connection with regulation of body pH are the pH of plasma and erythrocytes.
i.
Sodium
Balance
Sodium
is the major cation of E.C.F and occupies central role in maintenance of normal
hydration and osmotic pressure. Normal daily diet has about 130 – 250 m Eq(8
-15 gm) of sodium chloride (NaCl) most of which is completely reabsorbed in the
gastrointestinal tract. Excess of these is secreted by the kidney which is the
ultimate regulator of sodium content in the body. Sodium is a threshold
substance with a normal threshold of 110 – 130 mEq/L. Below this threshold, all
sodium present in the glomerular filtrate is reabsorbed in the renal tubule.
The reabsorption is greatly affected by adrenal cortical hormones, mainly
aldosterone which enhances the tubular reabsorption of sodium as well as
chloride but decreases that of potassium. The exchange of Na+
for H+
is an important mechanism of the acidification of urine.
Hypernatremia
is found is found in a variety of conditions including the following:
i.
Extreme urine loss, as in diabetes
insipidus
ii.
Metabolic acidosis e.g. diabetic
acidosis in which the ions are excreted along with the urine.
iii.
Addison’s disease, in which there may
be a decrease secretion of corticosteroids, mainly aldosterone, causes
decreased reabsorption of sodium by renal tubules and thus loss of serum
sodium.
iv.
Diarrhea, in which an excessive amount
of sodium is lost through the stool.
v.
Renal tubular disease, in which there
may be a defect in either the reabsorption of sodium or the Na+
- H+ exchange.
Hypernatremia is found in the following conditions:
i.
Hyperadrenalism (Cushing’s syndrome)
in which increase production of corticosteroids causes increased sodium
reabsorption and retention.
ii.
Severe dehydration due to primary
water loss.
iii.
Certain types of brain injury.
iv.
Diabetic coma after insulin therapy,
believed to be due to a retransfer of cellular sodium into the extracellular
fluid in order to maintain equal osmotic pressure in both compartments
v.
Excessive treatment with or ingestion
of sodium salts and drugs.
Normal
values
Range
of normal values for serum sodium is 135 – 148 MEq/L urinary sodium excretion
vary considerably and show diurnal variations.
ii Body Potassium
Potassium
is the major intracellular cation. The level in tissue cells is about 150m Eq/L
and about 105mEq/L in red blood cells – about 23 times more than that in the
extracellular fluid. This concentration difference is maintained by active
transport mechanisms and relatively low permeability of K+
through the cells.
However there are some movements of K+
across the cells and this may occur if the serum is not separated from the
cells shortly after collection.
Unlike sodium and chloride, there is no
threshold level for K+,
thus it is effectively re-excreted by the distal tubules. Any K+ reabsorption
in the gastrointestinal tract causes only a slight and temporary rise in serum
level; a fraction of these moves into the I.C.F and the remainder is rapidly
excreted by the kidney.
This mechanism protects the body against
high serum
levels which could cause serious (inhibitory)
disturbances in muscle irritability, respiration and myocardial function as
well as characteristic E.C.G. changes. Such symptoms appear with
levels of above 7.5mEq/L; a 10mEq/L level
may be fatal
Low
levels cause excitatory changes in muscle
irritability and myocardial function, which are also accompanied by
characteristic E.C.G. changes. For these reasons, serum
determination has become a most important
diagnostic tool.
The mechanism of
excretion and absence of threshold level has
the disadvantage that the body has no effective mechanism to prevent excessive
loss, because even in deficiency, kidney continues to excrete potassium. Thus
regular intake of
in
diet or in drug us essential.
Hypokalemia may result from inadequate
intake,
loss via prolonged diarrhea or through
vomitus. Also increased corticosteroids result in reduced potassium level by
causing increased loss. Alkalosis causes movement of
into the cells in exchange of
, and the reverse is the case in
acidosis. Thus alkalosis can result in reduced serum potassium level. In fact
low intracellular
can lead to alkalosis.
Hyperkalemia is generally observed in
cases of oliguria, anuria or urinary obstruction. In renal failure one of the
important purposes of renal dialysis is the removal of accumulated potassium
from the plasma.
Specimen for use for potassium level
determination should be free from hemolysis. Blood serum should be separated
shortly after collection. The shift of
is
greater at refrigerator temperatures.
Normal
Values:
Serum value is 3.5 – 5.3mEq/L but higher
in newborns (4.0 – 5.9). This may be due to error in collection and banding or
it may be due to the accumulated store of potassium existing prepartum. Urine
level is variable depending on diet and state of the body physiology.
iii Body
Chloride
This
is the major extracellular anion. It is significantly involved in maintaining
proper hydration. Osmotic pressure and normal cation – anion balance in this
compartment.
Chloride ions are completely absorbed by
gastrointestinal tract and are removed from the blood by glomerular filtration,
then reabsorbed passively by the tubules. It may be lost through excessive
sweating during hot periods. Low serum chloride values are observed in
salt-losing chromic pyelonephritis. This loss is due to a lack of tubular
reabsorption despite body deficit of chloride. In addisionian crisis, chloride
(and sodium) levels may drop significantly. Low chloride levels may also occur
in those types of metabolic acidosis (e.g. diabetic acidosis and renal failure)
caused by excessive production or diminished excretion of acids. Prolonged
vomiting may also result in significant loss of chloride.
High serum
values
are obtained in dehydration and in conditions causing decreased renal blood
flow e.g. congestive heart failure. Hypercloremic acidosis may be a sign of
severe renal tubular pathology.
1.5 THE
CONCEPT OF DETERMINING THE “NORMAL” VALUE
The
question of normal electrolyte values constituting electrolyte balance is still
on heated debate as to the proper definition of “Normalcy” or “Normalness” of
the values obtained or used.
It is now the contention that ‘normal’
is used not necessarily for person without any physical ailment, because this would
rule out virtually all persons of 20 years of age and above (Pryce, 1970, 1964).
‘Normal’ is used to connote the person who is not suffering from any disease or
disability likely to directly or indirectly affect the results of the
parameters under investigation.
A normal value for a given constituent
or clinical interest is considered to be that of the constituent of interest
which is found in the body fluid or excretion of a group of clinically normal
(apparently healthy) persons. These normal values are arbitrarily defined as
the range of values that would encompass 95% of a population of these
clinically normal persons. These normal data may be different from the ideal or
physiologically desirably value.
When establishing normal values for
chemical constituents of body fluids and excretions, physiologic variations are
taken into consideration, which may include diurnal variations, true day-to-day
variation and the environment. Also differences due to race, age, sex, weight,
nutritional and absorptive states, degree of physical activity, position of
body during blood sampling, stage of menstrual cycle, ovarian status, emotional
state, flexographic location and time of day at which sample was taken.
Establishment
of Normal Values:
This is necessary when a new method has
been developed or if the laboratory wishes to compare its range of normal
values with that found in literature.
In practice it is necessary to analyze
the blood of a group of apparently healthy individuals. Values thus obtained
have to be treated in a way that will result in a meaningful normal range. The
procedure to be selected will depend on the number of data available on the
type of data obtained and their relative distribution.
In practice, it is usual to consider
about 100 data, but frequently such number is not available and consequently,
the type of statistical method applied have to be selected accordingly. Data
distributed according to a symmetrical bell-shaped pattern is treated
differently from that skewed to one direction.
For most constituents, there may be an
overlap of values for normal and abnormal populations if the normal range is
set in such a way that it would include the entire normal population. Some of
the abnormal values would be in the normal range and go undetected. On the
other hand, a narrower normal range is used; a number of normal subjects may
have an ‘abnormal’ laboratory result. In the first case, a disease state may be
over looked and considered as a normal value just because it falls within the
normal range. In the second case where the range is too narrow, a normal
subject may be adjudged erroneously to show an abnormal value because the value
falls outside the fixed range. Thus a compromise has to be achieved to ensure
that the error made either way is minimal.
1.7 LITERATURE REVIEW
It
has been reported that Africans have smaller adrenal cortices with cortical
hypo-function as compared to Europeans Barnicot et al 1952; Monnet et al, 1952;
Politzer et al, 1958; Trowel 1960 and Edozien, 1960. However, only very little
work has been done to assess the implication of this hypo-function on their
plasma cation composition, and the results are conflicting.
Leschi
(1952) in Dakar in a comparative study of plasma cation content of Africans and
Europeans reported that the mean level of Na was about 5% lower in Africans.
This view was supported by Politzer (1954) in South Africa who reported the
South African Bantu Miner workers as having mean Plasma sodium of 137meq/l
(range 132-142) which would be regarded as low.
But
Owor (1965) in Uganda reported plasma Na values in Africans quire similar to
the European text-book values (mean 141 meq/1; range = 134 to 147 meq/1); and
so did Edozien (1958) in Nigeria. However, Adedavoh (1970) (personal
communication – quoted by Ezeilo, 1972) later reported from the same laboratory
as Edozien, a lower range for Nigerians (120 – 140meq/liters).
Also
more recently, Ezeilo 1972 reports that there are no significant differences between
the plasma or cellular values of sodium and potassium in normal adults of the
two races.
Not
much work has aslo been done on the plasma cation composition of pregnant
Africans women. The fact that African women fail to gain weight as much as
European women (Watts, 1970) could point to a failure to accumulate sodium
during pregnancy in Africans. In fact, Ezeilo (1972) found that in pregnant
African women, there was a hyponatremia relative to normal adults, which might
be contributory for their failure of gaining weight as much as their European
counterparts.
Reports
in Nigerian adults (Edozien 1958) and in Nigerian adults and children combined
(McFarlane et al 1970) are conflicting. The latter report concerned a large
population of blood donors, student nurses, pregnant women and random selection
of patients with unspecified diagnoses, including children. It is probable that
most of the subjects used, excepting maybe the student nurses and blood donors,
were not normal subjects. Pregnancy state is known to be associated with
hypervolaenia, and many hospital patients suffer from diarrhea and some degree
of dehydration. These differences in the subjects studied may be the cause of
conflict in the reports in Nigerian adults (Edozien 1958) and combined Nigerian
adults and children (McFarlane et al. 1970).
Whereas
Edozien reports a plasma Na level similar to that of Europeans (136-150 range),
McFarlane et al reports a range of 119-140 a lower range.
Effiong
et al (1974) also did a study of serum electrolyte and urea in healthy Nigerian
children. They report that “generally, serum electrolytes levels were
significantly higher than the levels reported in Nigerians and lower than those
for North American children”. The range for serum sodium (130-148 Eq/1) in
their study compares favorably with the British range of 136-145 mEq/1
(Birmingham children Hospital Vade-vecum 1970). They also failed to confirm the
finding of McFarlane et al (1970) who reported higher mean serum sodium levels
in males than in females. Effiong et al. 1974 also found that the chloride
values were significantly lower than the values reported from North America but
smilar, however, to that for British children, McFarlane et al 1970 and Stone
1936 have reported a low chloride level in Nigerians and South Rhodesian
Africans respectively. Politzer, Barry and King (1954) also reported higher
values in South African Bantus, whereas Edozien (1958) reports the value of
chloride in Nigerians as similar to that of the Caucasians.
Also
Effiong et al (1974) concludes that the bicarbonate level are significantly
lower than that reported by Gottfried et al (1954).
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