826
UNIT FIVE
vomiting in which only the stomach contents are lost, or
the use of certain diuretic drugs. Gastric juice is acidic, so
its loss leaves the body fl uids with a net increase of basic
substances and a pH shift toward alkaline values. Metabolic
alkalosis may also develop as a result of ingesting too much
antacid, such as sodium bicarbonate, to relieve the symp-
toms of indigestion. The symptoms of metabolic alkalosis
include a decrease in the breathing rate and depth, which, in
turn, results in an increased concentration of carbon dioxide
in the blood.
PRACTICE
28
What is the dif
erence between a respiratory acid-base
disturbance and a metabolic disturbance?
29
How do the symptoms oF alkalosis compare with those oF acidosis?
The symptoms of respiratory alkalosis include light-
headedness, agitation, dizziness, and tingling sensations. In
severe cases, impulses may be triggered spontaneously on
peripheral nerves, and muscles may respond with tetanic
contractions (see chapter 9, p. 297).
Metabolic alkalosis results from a great loss of hydrogen
ions or from a gain in bases, both accompanied by a rise in
the pH of the blood (alkalemia)
(f g. 21.18)
. This condition
may occur following gastric drainage (lavage), prolonged
Excessive loss of CO
2
Hyperventilation
• High altitude
• Poisoning
• Fever
• Anxiety
Decrease in concentration of H
2
CO
3
Decrease in concentration of H
+
Respiratory alkalosis
FIGURE 21.17
Some oF the Factors that lead to respiratory alkalosis.
FIGURE 21.18
Some oF the Factors that lead to metabolic alkalosis.
Gastric
drainage
Vomiting with loss
of gastric secretions
Loss of acids
Net increase in alkaline substances
Metabolic alkalosis
2. Body fl
uid composition
a. Extracellular fl
uids have high concentrations
of sodium, chloride, calcium, and bicarbonate
ions, with less potassium, calcium, magnesium,
phosphate, and sulfate ions. Plasma contains more
protein than does either interstitial fl
uid or lymph.
b. Intracellular fl uid contains relatively high
concentrations of potassium, magnesium,
and phosphate ions; it also contains a greater
concentration of sulfate ions and lesser
concentrations of sodium, chloride, calcium, and
bicarbonate ions than does extracellular fl
uid.
3. Movement of fl
uid between compartments
a. Hydrostatic and osmotic pressure regulate fl uid
movements.
(1) Fluid leaves plasma because of hydrostatic
pressure and returns to plasma because of
osmotic pressure.
(2) Hydrostatic pressure drives fl
uid into lymph
vessels.
CHAPTER SUMMARY
21.1
INTRODUCTION (PAGE 811)
The maintenance of water and electrolyte balance
requires that the quantities of these substances entering
the body equal the quantities leaving it. Altering
the water balance necessarily affects the electrolyte
balance.
21.2
DISTRIBUTION OF BODY FLUIDS
(PAGE 811)
1. Fluid compartments
a. The intracellular fl
uid compartment includes the
uids and electrolytes cell membranes enclose.
b. The extracellular fl
uid compartment includes all
uids and electrolytes outside cell membranes.
(1) Interstitial fl
uid is within tissue spaces.
(2) Plasma is part of the blood.
(3) Lymph is within lymphatic vessels.
(4) Transcellular fl
uid is within body cavities.
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