Chapter 25: Acid Base Homeostasis and imbalances

Question 1

The four primary acid base disorders

Answer 1

• Metabolic and respiratory acidosis ( pH 7.45)

Question 2

Acidosis

Answer 2

the presence of a condition that tends to decrease pH of the blood making it more acidic

Question 3

Alkalosis

Answer 3

the presence of a factor that increases the pH of blood above normal, making it more alkaline

Question 4

Metabolic Acidosis

Answer 4

• a relative excess of any acid except carbonic acid (renal failure, decrease in bicarbonate)
• may be caused by an increase in acid, an excess removal or decrease in base, or a combination of the both
• Results in the decrease of the normal 20:1 ratio of HCO3(carbonic acid) to H2CO3(bicarbonate)

Question 5

Metabolic Acidosis (Increase in Acid)

Answer 5

• decrease in the normal ratio of bicarbonate to carbonic acid because bicarbonate ions are used up in buffering the excess acid
• Examples include Starvation Ketoacidosis (caloric and glucose intake is insufficient), any ketoacidosis (breath will smell fruity and also have coolsmal), severe hyperthyroidism, burns, circulatory shock, tissue anoxia, oliguric renal failure, and intake of acid precursors

Question 6

Metabolic Acidosis (Removal or Decrease in Base)

Answer 6

• anything that causes a removal/decrease in bicarbonate
• examples include diarrhea, gastrointestinal fistula, renal tubular acidosis

Question 7

Clinical Manifestations of Metabolic Acidosis

Answer 7

• Headache
• abdominal pain
• central nervous system depression
• Severe metabolic acidosis shows tachycardia, ventricular dysrhythmias, decreased cardiac contractility, and death from brain failure if pH falls below 6.9
• Uncompensated ABG (below normal bicarbonate concentration, pH below normal, normal PaCO2)
• causes lungs to try and compensate to correct pH, results in very fast breathing which causes Kussmaul’s respirations (breathing very deep and fast)

Question 8

Compensatory Responses of Metabolic Acidosis

Answer 8

• Hyperventilation due to low pH
• non removal of metabolic acids from the body (trying to equalize acidity of blood)
• change in the ratio of bicarbonate ions to carbonic acid - compensatory increase in pH
• shows decreased bicarbonate concentration, decreased PaCO2, and decreased or even normal pH

Question 9

Normal Levels of HCO3 and PaCO2

Answer 9

• PaCO2 = 35-45 mmHg - HCO3 = 22-28 mmHg

Question 10

Respiratory Acidosis

Answer 10

• brain stem condition
• any condition that causes an excess of carbonic acid
• caused by impaired removal of carbonic acid by the lungs (impaired gas exchange, inadequate nuromuscular function, impairment of respiratory control in brainstem)
• Decrease in the normal 20:1 ratio of biarbonate ion to carbonic acid

Question 11

Respiratory Acidosis (Impaired Gas Exchange)

Answer 11

• Chronic obstructive pulmonary disease (COPD)
• Pneumonia
• severe asthma
• pulmonary edema
• acute respiratory distress syndrome

Question 12

Respiratory Acidosis (Inadequate Neuromuscular Function)

Answer 12

• guillian-Barre Syndrome
• chest injury or surgery
• Hypokalemic respiratory muscle weakness
• Severe kyphoscoliosis (at top of spine and bottom, which causes decreased lung movement)
• Respiratory Muscle Fatigue

Question 13

Respiratory Acidosis (impaired respiratory control)

Answer 13

• respiratory depressants drugs (opiods, barbiturates)

Question 14

Clinical Manifestations of Respiratory Acidosis

Answer 14

• headache
• tacchycardia
• cardiac dysrhythmias
• Neurologic Abnormalities (blurred vision, tremors, vertigo, disorientation, lethargy, somnolence)
• Severe respiratory acidosis causes peripheral vasodialtion with hypotension
• Uncompensated ABG (PaCO2 above normal, pH below normal, Bicarbonate normal)

Question 15

Compensatory Response of Respiratory Acidosis

Answer 15

• increased renal excretion of metabolic acid which results in an increase of bicarbonate ion movement of pH towards normal
• compensated respiratory acidosis will show increased PaCO2 (primary imbalance) , increased bicarbonate concentration (compensation), and decreased or normal pH

Question 16

Metabolic Alkalosis

Answer 16

• Any condition that tends to cause a relative deficit of any acid (except for carbonic acid) - causes include and increase in base, decrease in acid, or a combination of the two

Question 17

Metabolic Alkalosis (increase in base)

Answer 17

• intake of bicarbonate or bicarbonate precursors (acetate, lactate, citrate) - massive transfusion with citrated blood - mild or moderate extracellular fluid volume deficit

Question 18

Metabolic Alkalosis (decrease in acid)

Answer 18

• emesis (vomiting) - gastric suction - mild or moderate extracellular volume deficit (contraction alkalosis) - hyperaldosteronism - Hypokalemia

Question 19

Clinical Manifestations of Metabolic Alkalosis

Answer 19

• Postural Hypotension
• hypokalemia may coexist
• Increased neuromuscular excitability (tingly fingers and toes, signs of tetany(sustained muscle contraction), ionized hypokalemia)
• increased excitablity of nerve cell membranes
• beligerence
• Severe metabolic alkalosis causes central nervous system depression, confusion, lethargy, and coma. Death occurs at pH 7.8
• Uncompensated ABG shows elevated bicarbonate concentration, normal PaCO2, above normal pH

Question 20

Compensatory Response of Metabolic Alkalosis

Answer 20

• hypoventilation
• usually incomplete (need for oxygen drives ventilation and prevents complete compensation)
• compensated Metabolic Alkalosis shows increased bicarbonate concentration (primary imbalance), increased PaCO2 (compensation), slightly increased pH

Question 21

Respiratory Alkalosis

Answer 21

• any condition that tends to cause a carbonic acid deficit
• caused by hyperventilation

Question 22

Respiratory Alkalosis (hyperventialtion)

Answer 22

• hypoxemia
• acute pain
• anxiety, psycholigical stress
• prolonged sobbing
• alcohol withdrawls
• stimulations of the brainstem

Question 23

Clinical Manifestations of Respiratory Alkalosis

Answer 23

• Increased neuromuscular excitability
• increased central and peripheral membrane excitability
• increased pH of cerebrospinal and cerebral interstitial fluid alters brain cell function
• cerebral vasoconstriction
• uncompensated ABGs show abnormally low PaCO2, abnormally high pH, and a normal bicarbonate level

Question 24

Compensatory Response of Respiratory Alkalosis

Answer 24

• decreased renal excretion of metabolic acid
• decrease in bicarbonate ion concentration
• renal compenstation tends to return the ratio of bicarbonate ions to carbonic acid, moving pH towards normal
• Compensated respiratory ABGs show decreased PaCO2 (primary imbalance), decreased bicarbonate concentration (compensation), increased somewhat high pH

Question 25

Mixed Acid Base Imbalances

Answer 25

• 2 primary imbalances occur simutaneously
• 2 types of primary acidosis or alkalosis may impair effectiveness of usual compensatory mechanisms
• pH will reflect primary mechanism
• may also occur with a nearly normal pH if a primary acidosis and a primary alkalosis are involved
• if bicarbonate is the main problem it is acidosis, if PaCO2 is the main problem it is alkalosis