MU PT 7890, Case Mgmt I
Arterial Blood Gas (ABG) Analysis; Acid-Base Balance
pH
Lungs – volatile acids (minutes)
Respiratory
Alkalosis
S&S:
Acidosis
S&S:
Kidneys: excrete or retain (12-24 hrs)
Metabolic
Alkalosis
S&S:
Acidosis
S&S:
PaCO2
HCO3 -
Treatment
Acidemia can occur from 2 different causes:
1. Respiratory cause: ↑PaCO2
[an INVERSE relationship to the pH]
The CO2 dissolved in blood is carbonic acid (H2CO3). CO2 remains a “volatile” gas that can be “blown off” during expiration.
High PaCO2 (hypercapnia) is caused by alveolar hypoventilation that is the result of either thickened, scarred alveolar wall, excessive
secretions, or destruction of the alveolar surface area that is available for diffusion of O2 and CO2. Therefore less CO2 can be blown off. It
makes the blood more acidic, lowering the pH.
S&S: dyspnea, anxiety, headache; if acute it can progress to confusion and coma
Rx: address the Ventilation : Perfusion mismatch (V:Q < 1) by airway clearance techniques; also by pursed lip breathing to provide
positive airway pressure (PAP) to splint open the bronchioles and alveolar ducts; stop exposure to environmental triggers / smoking
2. Metabolic cause: ↓ HCO3 (and ↓PaC02) [a DIRECT relationship to the pH]
The Bicarb ion is being used up to buffer the non-volatile acids circulating in the blood, i.e. lactic acid from anaerobic metabolism, ketones
from incomplete fat metabolism, or ketones from diabetic hyperglycemia / ketoacidosis.
S&S: Kussmaul breathing (secondary hyperventilation that is variously described as “deep, rapid, labored, sighing”), nausea; can progress
to coma
Rx: safe exercise and activity to minimize lactic acid production; proper nutrition to prevent ketoacidosis. Diabetics must manage blood
sugars more tightly.
Alkalemia can occur from 2 different causes:
1. Respiratory cause: ↓ PaCO2
[an INVERSE relationship to the pH]
Hyperventilation: over-ventilation that blows off too much CO2 due to anxiety, pain, or cerebral trauma
S&S: dizziness, syncope, N&T, early tetany
Rx: Treatment of respiratory alkalosis includes reassurance, assistance in slowing breathing and facilitating relaxation, sedation, pain control, CO2
administration, and use of a rebreathing device such as a rebreathing mask or paper bag. A rebreathing device allows the client to inhale and
“rebreathe” the exhaled CO2. Teach diaphragmatic breathing.
2. Metabolic cause: ↑ HCO3 (and ↓PaC02) [a DIRECT relationship to the pH]
Multiple causes: eating too many antacids, excessive vomiting loses stomach acid, other reasons.
S&S: weakness, mental dullness, early tetany
Rx: educate on antacid use