MDC II - Exam 2
Causes of respiratory acidosis (low ph/ high CO2)
-Hypoventilation
-Drug overdose
-Pulmonary edema
-Chest trauma/neuromuscular disease
-COPD
-Airway obstruction
Causes of Metabolic Acidosis (low pH/low HCO3)
-Diabetic ketoacidosis
-Salicylate OD
-Renal failure
-Severe diarrhea
-Sepsis
-Shock
How to evaluate that treatment is working for respiratory acidosis?
-Maintains adequate gas exchange
-Arterial pH above 7.2 and closer to 7.35
-PaO2 level above 90 mmHg or at least 10 mm Hg higher than their admission level
-PaCO2 levels below 45 mmHg or at least 15 mm Hg below their admission level
Alkalosis pathophysiology
Alkalosis is a decrease in the free hydrogen ion level of the blood and is reflected by an
arterial blood pH above 7.45.
Metabolic Alkalosis: Base excess in what?
Excessive intake bicarbonates, carbonates, acetates, citrates
Cause of acid deficit?
Prolonged vomiting, excess cortisol, hyperaldosteronism, thiazide diuretics, prolonged
NG suction, loss of gastric fluids.
Hallmark of base excess acidosis?
ABG result with ↑ pH and ↑ bicarbonate level with normal O2 and CO2 levels
What is citrate?
citrate is an anticoagulant used in blood products that is rapidly metabolized in the liver
What can happen when blood is rapidly administered?
rapid administration of large quantities of stored blood can cause hypocalcemia and
hypomagnesmia.
The nurse is evaluating the laboratory work of a patient who has uncontrolled
metabolic acidosis. Which outcome would result from this condition?
A.pH 7.40
B.Pao2 98 mm Hg
C.Bicarbonate 38 mEq/L
Serum potassium 5.7 mEq/L
ANS: D
Metabolic acidosis is reflected by several changes in ABG values. The pH is low
, (<7.35). The bicarbonate level is low (<21 mEq/L). The partial pressure of arterial
oxygen (Pao2) is normal because gas exchange is adequate. The serum potassium
level is often high in acidosis as the body attempts to maintain electroneutrality during
buffering.
The nurse is reviewing the standing orders for a patient who was admitted for
evaluation of chest pain. The patient has a history of chronic obstructive
pulmonary disease (COPD) and his laboratory results and assessment reveal that
he has mild respiratory acidosis. The nurse would question which order?
A.Encourage oral fluids
B.Keep head of bed elevated
C.Oxygen therapy at 4 L/min as needed
Bedrest with bathroom privileges only
ANS: C
The bedrest order will help the patient conserve energy. The upright position (mid-
Fowler's to high-Fowler's position) helps increase lung expansion. Increasing fluid
intake may reduce the thickness of lung secretions and assist in their removal. Oxygen
therapy helps promote gas exchange for patients with respiratory acidosis. However,
use caution when giving oxygen to patients with COPD and CO2 retention as evidenced
by a high Paco2 level. The only breathing trigger for these patients is a decreased
arterial oxygen level. Giving too much oxygen to these patients decreases their
respiratory drive and may lead to respiratory arrest.
What is the third line of defense against pH changes?
Kidneys
Acid-base Control Actions and Mechanisms: Kidney
-Stronger for regulation acid-base balance; takes longer than chemical and respiratory.
-Kidneys move bicarbonate.
-Formation of acids and ammonium
-Kidneys can correct/compensate for pH changes when respiratory system is
overwhelmed or unhealthy.
Compensation
Body attempts to correct blood pH chan
What pH is considered fatal?
<6.9
>7.8
What system is more sensitive to acid-base changes?
Respiratory system: can begin compensating in seconds to minutes.
Which system is more powerful when compensating?
Kidneys: can result in rapid changes in ECF composition. Fully triggered for imbalance
of several hours to days.
List the 5 possible acid-base imbalances
Metabolic acidosis
Respiratory acidosis
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