The Actions of Buffer Systems
-Most buffer systems in the body consist of a weak acid and the salt of that
acid, which functions as a weak base.
-Buffers prevent rapid, drastic changes in the pH of body fluids by
converting strong acids and bases into weak acids and weak bases within
fractions of a second.
-Strong acids lower pH more than weak acids because strong acids release H
more readily and thus contribute more free hydrogen ions.
-Similarly, strong bases raise pH more than weak ones.
-The principal buffer systems of the body fluids are the protein buffer
system, the carbonic acid-bicarbonate buffer system, and the phosphate
buffer system.
Electrolyte Balance
-Electrolytes are in balance when the concentrations of individual
electrolytes in the body fluid compartments are normal and remain relatively
constant.
-This implies that the total electrolyte concentration is also normal and
constant.
-Because electrolytes are dissolved in the body fluids, electrolyte balance
and fluid balance are interrelated.
-When fluid volume changes, the concentrations of the electrolytes also
change.
-Sodium is the predominant cation (positive ion), and chloride is the
predominant anion (negative ion) in the extracellular fluid. Bicarbonate ions
are also extracellular ions. These three ions account for over 90% of the
extracellular electrolytes. In the intracellular fluid compartment, potassium
is the most abundant cation and phosphates are the major anions.
-The primary regulation of electrolyte balance is through active reabsorption
of positive ions. Because sodium and potassium are the predominant
cations, they are the most important ones to be regulated.
-Fluid balance and electrolyte balance are interdependent.
Acid-Base Balance
-Blood, the intravascular fluid, has a normal pH of 7.35 to 7.45.
-Deviations below this range are called acidosis.
-The physiologic effect of acidosis is depression of synaptic transmission in
the central nervous system. If untreated, the depression may become so
severe that the person becomes disoriented and lapses into a coma. Death
soon follows.
-Deviations of pH above 7.45 are called alkalosis.
-The principal effect of alkalosis is hyperexcitability in both the central
nervous system and the peripheral nerves. This leads to extreme
nervousness and muscle spasms. If untreated, alkalosis may lead to
convulsions and death.
-Cellular metabolism produces substances that tend to upset the pH balance.
-Lactic acid is produced in the anaerobic breakdown of glucose.
-When carbon dioxide from aerobic metabolism combines with water, it
produces carbonic acid.
-The metabolism of fatty acids produces acidic ketone bodies.
-All of these products tend to make the blood more acidic and to lower the
pH.
-The body has three mechanisms by which it attempts to maintain a normal
blood pH:
- Buffers
- Removal of carbon dioxide by the lungs
- Removal of hydrogen ions by the kidneys
-Buffers are substances that prevent significant changes in pH.
-If the hydrogen ion concentration is too high (acid), the buffer combines
with some of the hydrogen ions to bring the pH back to normal.
-If the hydrogen ion concentration is too low (alkaline), the buffer releases
hydrogen ions to lower the pH.
-Buffers are important for adjusting small changes in hydrogen ion
concentration.
-Acidosis and alkalosis can be classified according to cause as either
respiratory or metabolic.
-Respiratory acidosis or alkalosis represents an underlying problem with
respiratory mechanisms, and the most important indicator of these
conditions is the partial pressure of carbon dioxide.
-All other acid-base imbalances are grouped together as metabolic.
-The most important indicator of metabolic acid-base imbalances is the
concentration of bicarbonate ions in the blood.
-Changes in blood pH that lead to acidosis or alkalosis can be returned to
normal by physiologic responses called compensation.
-If a person has a pH imbalance caused by some problem in the respiratory
system, the kidneys attempt to compensate by changing the amount of
hydrogen and bicarbonate ions that are excreted.
-If the imbalance is caused by something other than the respiratory system
(metabolic imbalances), the respiratory system attempts to bring the pH back
to normal by changing the rate and depth of breathing to either conserve or
eliminate carbon dioxide, which increases or decreases acidity, respectively.
-Any condition that hinders the movement of carbon dioxide from the blood
to the alveoli and into the atmosphere may result in respiratory acidosis. --Such conditions include emphysema, airway obstruction, depression of the
medullary respiratory centre, weakness of the muscles used in breathing, and
pulmonary edema.
-The kidneys compensate by excreting hydrogen ions in the uring and by
reabsorbing bicarbonate ions.
-Respiratory alkalosis is caused by a loss of carbon dioxide from the lungs
through hyperventilation.
-Conditions that may lead to respiratory alkalosis are those that stimulate the
respiratory centre in the medulla, such as severe anxiety, hysterical hyperventilation, oxygen deficiency because of high altitude, and the early stages
of aspirin overdose.
-The kidneys compensate for this condition by conserving hydrogen ions
and increasing bicarbonate ion excretion.
-Metabolic acidosis may be due to a loss of bicarbonate ions through
conditions such as severe diarrhea or renal dysfunction, or to an
accumulation of metabolic acids such as occurs in diabetes mellitus. The
respiratory system attempts to compensate for metabolic acidosis by
hyperventilation.
-Metabolic alkalosis occurs when there is a non respiratory loss of acids
such as occurs by repeated vomiting of gastric contents, or by excessive
intake of alkaline substances such as sodium bicarbonate and other antacids.
-The respiratory system attempts to compensate for metabolic alkalosis by
hypoventilation, which retains carbon dioxide in the body and lowers the
pH.
The table below summarizes the four different types of acid-base
imbalances
Imbalance
pH
Causes
Compensation
Respiratory
<7.35
Emphysema,
Kidneys excrete
airway
hydrogen ions
obstruction,
and reabsorb
depression of
bicarbonate ions
acidosis
respiratory
centre,
respiratory
muscle weakness
Respiratory
>7.45
Hyperventilation, Kidneys
alkalosis
Metabolic
<7.35
acidosis
severe anxiety,
converse
high altitude,
hydrogen ions
early aspirin
and excrete
overdose
bicarbonate ions
Loss of
Increased
bicarbonate ions
respiratory rate
through severe
diarrhea or renal
dysfuntion,
increased
metabolic acids
(diabetes
mellitus)
Metabolic
alkalosis
>7.45
Loss of acids,
Decreased
such as by
respiratory rate
repeated
vomiting,
excessive intake
of alkaline
substances, such
as antacids
What is diabetes?
A disease that occurs when the body is not able to use blood glucose (sugar).
Blood sugar levels are controlled by insulin, a hormone in the body that
helps move glucose (sugar) from the blood to muscles and other tissues.
Diabetes occurs when the pancreas does not make enough insulin or the
body does not respond to the insulin that is made. There are two main types
of diabetes mellitus: type 1 diabetes and type 2 diabetes.

Type 1 diabetes or insulin-dependent diabetes. It is
usually seen in young people.

Type 2 diabetes - usually non insulin-dependent
diabetes. It tends to affect adults over 40 and
overweight people.
There are also other types of diabetes.

Pregnancy diabetes. This is known as gestational
diabetes. It's associated with pregnancy and symptoms
usually disappear after the birth. If you get gestational
diabetes, you have an increased risk of developing one
of the main types of diabetes later in life.

Secondary diabetes. This is when diabetes is caused as
the result of another condition, eg inflammation of the
pancreas, or by the use of certain medication such as
diuretics or steroids (the most common cause).
How common is diabetes?
In the UK around 1.6 million people have been diagnosed
with diabetes.
But Type 2 diabetes often has few symptoms in the early
stages - it's estimated that half of those with Type 2
diabetes have not yet been diagnosed.
The last 30 years has seen a threefold increase in the
number of cases of childhood diabetes.
Obesity levels have also risen - and this has led to Type 2
diabetes, which is linked to diet, being seen for the first time
in young people in Europe and America.
But obesity doesn't explain the increase in the numbers of
Type 1 diabetes in children - who make up the majority of
new cases.
What causes diabetes?
Insulin is a hormone produced by the
pancreas gland in the abdomen. It
controls the use of glucose within the
body.
The blood sugar level will rise if:
Term watch
Glucose is sugar.
Blood sugar
level is the same
as blood
glucose level.

the pancreas produces little or no
insulin (Type 1 diabetes)

the pancreas produces insulin, but it's inadequate for
the body’s needs and its effectiveness is reduced (Type
2 diabetes).
It's thought Type 2 diabetes is related to factors associated
with a Western lifestyle, since it's most common in people
who are overweight and who don't get enough exercise.
Gestational diabetes is brought about by the many hormone
changes and demands placed upon the body during
pregnancy.
Secondary diabetes is much like Type 2 diabetes. It's quite
variable, depending on the underlying cause.
Common symptoms of diabetes
Glucose is one of the body’s main fuels. If there isn't
enough, blood sugar levels rise and glucose is secreted into
urine. This causes:

increased thirst

frequent urination

tiredness

weight loss, although appetite often increases
(especially in Type 1 diabetes)

recurrent infections on the skin, eg boils.
People with Type 1 diabetes usually develop these
symptoms within days or weeks.
In Type 2 diabetes, these symptoms often don't show for
years. Many are diagnosed by chance through routine
medical check-ups.
Heredity plays a part in diabetes, but only 10 per cent of
people with Type 1 have a family history of diabetes. For
Type 2, this rises to 30 per cent.
How is a diagnosis made?
Type 2 traits
People with Type
2 diabetes often
Glucose levels are measured in blood
have:
samples. This is done using the following
 family history
tests:
of diabetes
 obesity
 random glucose test: glucose
levels are taken at a random time on  increased
blood pressure
two occasions. Any figure above
 premature
11.1mmol/l is a diagnosis of
vascular
diabetes.
problems such as
 fasting glucose test: the glucose
heart attacks and
level is measured after an overnight stroke
fast and on two different days. Above  raised level of
7.0mmol/l is a diagnosis of diabetes. triglyceride (a
type of fat) in
You may only need to give one blood
the blood.
sample if you have other symptoms of
diabetes.
Glucose tolerance test
If the diagnosis is still unclear from these tests, a
glucose tolerance test can be carried out.
A glucose drink is given containing a standard amount
of glucose (75g). Blood samples are taken before the
drink is given and two hours later. The test is done
after an overnight fast.

A two-hour blood glucose level above 11.1mmol/l
is a diagnosis of diabetes.

A level below 7.8mmol/l is normal.
If the level falls between these values, it suggests a
decreased tolerance for glucose.
This is known as impaired glucose tolerance (IGT).
Impaired glucose tolerance is more than just a prediabetic state.
People who have IGT are at increased risk of
developing some of the conditions associated with
diabetes, such as heart disease.
How is diabetes treated?
Diabetes is treated in two ways:
a combination of healthy diet and exercise
Diet and
medication with tablets or insulin.
diabetes
A special diet
Insulin injections increase the amount of
used to be
insulin in your body and bring down the
recommended for
blood sugar level. Insulin injections are
diabetes.
used in Type 1 diabetes and in some cases
It's now thought
of Type 2.
a normal wellbalanced diet is
There are different types of oral
best.
medication for treating Type 2 diabetes:
But calorie intake
is still important.
 some increase the amount of insulin
People with
secreted by the pancreas
diabetes who are
 some increase the action of insulin in overweight need
to think of weight
the body
loss as part of
 some delay the absorption of glucose their treatment.
from the digestive system.
Treatment for diabetes depends on the individual.
It starts the first time you give yourself an insulin injection
or take a diabetes tablet, and continues through eating a
well-balanced diet and starting an exercise programme.
To help you get the most out of treatment, consult your GP
or hospital healthcare team, which should include a diabetes
nurse specialist.
Blood sugar levels
Monitoring blood sugar levels is an important aspect of
treatment, especially in Type 1 diabetes where levels
can change markedly.
This can be done easily at home with a small blood
glucose meter.
Depending on the reading, you may need to adjust
your diet, the amount you exercise or your insulin
intake.
Managing diabetes
In the long-term, diabetes is monitored through routine
check-ups by your doctor and/or annual check-ups at the
hospital on an outpatient basis.
Their purpose is to determine if treatment is satisfactory and
to look out for any evidence of longer-term complications
such as eye or kidney disease.
Tests for these complications are usually done at the annual
check-up, while routine check-ups may be carried out every
three to six months.
Routine check-ups

Blood sample to check the amount of HbA1c
(long-term glucose) in the blood.

Evaluation of home glucose readings.

Discussion of diet.

Blood pressure.

Weight check.

Other tests and examinations as determined by
your doctor.
Annual check-ups

Blood sample to check the amount of HbA1c
(long-term glucose) in the blood.

Blood sample to determine the amount of fats in
the blood.

Blood sample to check kidney function and various
salts in the blood (mainly sodium and potassium).

Blood pressure.

Urine sample to determine the presence of protein
(albuminuria). The appearance of protein can
indicate that the filtering power of the kidneys is
beginning to be affected by the diabetes.

Foot examination, including a check of various
pulse points on the foot.

Weight check.

Measuring the waistline.

Discussion of exercise habits.

Discussion of smoking habits.
Long-term prospects
Both types of diabetes have the risk of complications.
Acute complications

Low glucose level, caused by treatment with
insulin or oral hypoglycaemic drugs.

Diabetic acidosis, a life-threatening condition
caused by the lack of insulin.
Late-stage diabetic complications

Retinopathy (eye disease) that can cause
blindness.

Diabetic kidney disease that can lead to kidney
failure.

Diabetic neuropathy (nerve disease) that can
cause foot ulcers and foot infections.

Atherosclerosis (hardening of the arteries),
particularly in smokers and those with high blood
pressure.
Late-stage complications do not usually develop for 1015 years with Type 1 diabetes.
In Type 2 diabetes, however, symptoms can appear
close to the time of actual diagnosis because the
disease may go undetected for longer.
Many studies now show that good glucose control can
significantly reduce or even stop complications. This means
keeping the blood sugar level as close to normal as possible.
Recent studies have also confirmed the need for people with
diabetes to reduce their risk of atherosclerosis (fatty
deposits in your arteries).
This is because if you have Type 2 diabetes, you have a four
to five times greater risk of developing serious problems
with your circulation that can lead to a heart attack or a
stroke.
The main factors that increase your risk are:

smoking

high blood pressure

raised levels of fats such as cholesterol in the blood.