Page 48 - Critical Care Nursing Demystified

Chapter 2 CARE OF THE PATIENT WITH CRITICAL RESPIRATORY NEEDS 33

nature, then the kidneys will work to correct it. If the problem is renal in origin,
the lungs will attempt to correct it. To determine levels of compensation, exam-
ine pH, carbon dioxide (pCO ), and bicarbonate (HCO ).
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Uncompensated, Partially Compensated, or Combined

ABG Problems
There are two types of compensation to look for in an ABG. If compensation
occurs, it is full or partial. If there is no compensation, the ABG is called uncom-
pensated. If there are both respiratory and metabolic primary problems, the
ABG is known as mixed or combined (see Table 2–3).
Uncompensated – Here the pH is abnormal; it will be either an acidosis or
an alkalosis. The pH will always point to the primary problems (acidosis/
alkalosis). The nurse then needs to look at the pCO or HCO . In an uncom-
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pensated problem, there will be a respiratory acidosis or alkalosis or a meta-
bolic acidosis or alkalosis, but the value that would correct for this, the opposite
organ value, will not change as there is no compensation for the problem.

Example: Uncompensated respiratory acidosis
pH = 7.33, pCO = 55, HCO = 24 Downloaded by [ Faculty of Nursing, Chiangmai University 5.62.158.117] at [07/18/16]. Copyright © McGraw-Hill Global Education Holdings, LLC. Not to be redistributed or modified in any way without permission.
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Reason: The pH indicates an acidosis, which is caused by the pulmonary
system as the pCO is elevated. The kidney would compensate, but since the
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HCO is normal, compensation has not occurred.
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Example: Uncompensated metabolic alkalosis

pH = 7.52, pCO = 40, HCO = 30
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Reason: The pH will always tell you where the primary problem is. In this case,
a pH greater than 7.45 shows an alkalosis and the HCO indicates it is meta-
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bolic. There is no compensation when the pCO is normal.
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TABLE 2–3 ABG Interpretation Chart
Compensation
pH pCO HCO pCO HCO
2 3 2 3
Respiratory acidosis ↑ ↓ ↓
Respiratory alkalosis ↓ ↑ ↑
Metabolic acidosis ↑ ↑ ↑
Metabolic alkalosis ↓ ↓ ↓