To help identify the specific cause, health care providers and the
laboratory calculate the anion gap, a reflection of unmeasured anions in
plasma. You calculate anion gap by subtracting the sum of plasma
concentrations of the anions Cl− and image from the plasma concentration
of the cation Na+. When reviewing laboratory reports, check the reference
values from the laboratory that measured the electrolyte concentrations
(Table 42-8).
o
Metabolic Alkalosis
Metabolic alkalosis occurs from a direct increase of base (image) or a
decrease of metabolic acid, which increases blood image by releasing it
from its buffering function. Common causes include vomiting and gastric
suction (see Table 42-7). The respiratory compensation for metabolic
alkalosis is hypoventilation. The decreased rate and depth of respiration
allow carbonic acid to increase in the blood, as seen by an increased
PaCO2.
The need for oxygen may limit the degree of respiratory compensation for
metabolic alkalosis. Because image crosses the blood-brain barrier with
difficulty, neurological signs and symptoms are less severe or even absent
with metabolic alkalosis.
o
Respiratory Acidosis
Respiratory acidosis arises from alveolar hypoventilation; the lungs are
unable to excrete enough CO2. The PaCO2 rises, creating an excess of
carbonic acid in the blood, which decreases pH (Table 42-7). The kidneys
compensate by increasing excretion of metabolic acids in the urine, which
increases blood bicarbonate.
This compensatory process is slow, often taking 24 hours to show clinical
effect and 3 to 5 days to reach steady state. Decreased cerebrospinal fluid
(CSF) pH and intracellular pH of brain cells cause decreased level of
consciousness.
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Respiratory Alkalosis
Respiratory alkalosis arises from alveolar hyperventilation; the lungs
excrete too much carbonic acid (CO2 and water). The PaCO2 falls,
creating a deficit of carbonic acid in the blood, which increases pH (see
Table 42-7). Respiratory alkalosis usually is short lived; thus the kidneys
do not have time to compensate.
When the pH of blood, CSF, and ICF increases acutely, cell membrane
excitability also increases, which can cause neurological symptoms such
as excitement, confusion, and paresthesias. If the pH rises high enough,
central nervous system (CNS) depression can occur.
IV therapy
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Insertion
After you collect the equipment at the patient's bedside, prepare to insert
the IV line by assessing the patient for a venipuncture site. The most
common IV sites are on the inner arm. Do not use hand veins on older
adults or ambulatory patients. IV insertion in a foot vein is common with
children, but avoid these sites in adults because of the increased risk of
thrombophlebitis.
As you assess a patient for potential venipuncture sites, consider
conditions that exclude certain sites. Venipuncture is contraindicated in a
site that has signs of infection, infiltration, or thrombosis. An infected site
is red, tender, swollen, and possibly warm to the touch. Exudate may be
present. Do not use an infected site because of the danger of introducing
bacteria from the skin surface into the bloodstream. Avoid using an
