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Patho > Acid-Base Disturbances > Flashcards

Acid-Base Disturbances Flashcards

1
Q

What is an acid?

A

a molecule that can release a H+

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2
Q

What is a base?

A

an ion or molecule that can accept or combine with a H+

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3
Q

Why are acids continuously generated?

A

as by-products of metabolism

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4
Q

What is a volatile acid?

A

-H2CO3 is in equilibrium with CO2 (H2CO3 ⇌ CO2 + H2O)
-Ability of the lungs to exhale CO2 determines levels of H2CO3

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5
Q

What is a non-volatile or fixed acid?

A

-Buffered by body proteins or extracellular buffers (HCO3-) then excreted by the kidneys

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6
Q

How is CO2 dissolved in blood plasma for transport?

A

-Quantity dissolved in plasma can be determined by its PCO2
-Dissolved CO2 is converted to H2CO3 which contributes to blood pH
-H2CO3 ⇌ CO2 + H2O

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7
Q

How is CO2 transported as bicarbonate?

A

-Within the RBC, carbonic anhydrase catalyzes its conversion into H2CO3
-H2CO3 then dissociates into H+ and HCO3-
-H+ combines with hemoglobin (HHb) and HCO3- diffuses into plasma
-HCO3- now participates in acid- base regulation

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8
Q

How is CO2 transported as carbaminohemoglobin?

A

-Remaining CO2 in RBCs binds to Hb to form HbCO2
-Loose bond - so CO2 can easily be released in capillaries and can exhaled

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9
Q

What are the 3 major mechanisms pH of body fluids is regulated by?

A

-Chemical buffer systems (combine with excess acids or bases to prevent large changes in pH)
-Respiratory system (control the elimination or retention of CO2)
-Renal system (eliminates H+ and both reabsorbs and generates new HCO3-)

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10
Q

What do buffer systems do to regulate pH?

A

-Control minute-to-minute pH changes
-Respond temporarily to larger changes (1st line of defense)

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11
Q

What does the respiratory system do to regulate pH?

A

-Responds quickly and with fast results (2nd line of defense)
-Does not return to homeostasis

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12
Q

What does the renal system do to regulate pH?

A

-Main responsibility for return to homeostasis
-Slow to respond, slow to work (3rd line of defense)

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13
Q

What is acidosis?

A

increased concentration of H+ ions (pH < 7.35)

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14
Q

What is alkalosis?

A

decreased concentration of H+ ions (pH > 7.45)

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15
Q

What is normal pH in humans?

A

7.35-7.45

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16
Q

What is Respiratory Acidosis/Alkalosis?

A

altered PCO2 (35- 45mmHg)

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17
Q

What is Metabolic Acidosis/Alkalosis?

A

altered HCO3- (22-26mEq/L)

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18
Q

What is metabolic acidosis?

A

-Involves a decreased concentration of plasma HCO3- levels and decreased pH
-The body compensates for the acidosis with an increased respiratory rate in an attempt to lower PCO2 and therefore H2CO3

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19
Q

What conditions can cause metabolic acidosis?

A

-Uncontrolled diabetes mellitus ( + ketoacids)
-Starvation or severe carbohydrate reduced diet (+ ketoacids)
-Severe exercise (increase in lactic acid)
-Severe diarrhea (GI loss of HCO3)
-Renal failure (failure to excrete H+)
-Cardiac failure or arrest (increase in lactic acid)
-Acute alcohol intoxication (increase in fixed acids)
-Salicylate overdose (increased fixed acids)
-Shock (increase lactic acid)

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20
Q

How does lactic acidosis cause metabolic acidosis?

A

-Caused by the increased production or decreased removal of lactic acid
-Lactic acid is a byproduct of anaerobic metabolism of glucose
-Can occur when the metabolic tissue demands exceed the aerobic production of ATP
-Often caused by inadequate oxygen delivery or severe hypoxia
-Anemia, shock, cardiac arrest, hypotension, decreased CO Causes

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21
Q

How does ketoacidosis cause metabolic acidosis?

A

-Ketoacids are a source of fuel for many body tissues
-An overproduction of ketoacids occurs when carbohydrate stores are inadequate or the body can’t use available carbs (lack of insulin)
-Common causes include: Poorly controlled diabetes, Fasting or food deprivation

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22
Q

How does salicylate toxicity cause metabolic acidosis?

A

-Acetylsalicylic acid (Aspirin - ASA) is absorbed in the stomach and small bowel and then converted to salicylate acid
-An OD of ASA can produce a mixed disorder
-Cross the blood brain barrier and stimulate the respiratory centre to produce hyperventilation (respiratory alkalosis)
-Kidneys respond by excreting HCO3-, Na+ and K+ (metabolic acidosis)

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23
Q

How does decreased renal function cause metabolic acidosis?

A

-CKD (chronic kidney disease) is the most common cause of chronic metabolic acidosis
-Results in a loss of glomerular filtration and tubular reabsorption/secretion - retention of wastes and metabolic acids

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24
Q

How does increased bicarbonate loss cause metabolic acidosis?

A

-Loss of HCO3- rich fluids or with impaired renal conservation of HCO3-
-Intestinal secretions have a high HCO3- concentration, severe diarrhea
-Hyperchloremic Acidosis:

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25
Q

What is hyperchloremic acidosis?

A

-Occurs when Cl- levels are increased out of proportion to Na+
-Cl- and HCO3- are interchangeable anions, therefore, when plasma Cl- increases, plasma HCO3- decreases
-Can occur due to impaired renal reabsorption or treatment with chloride containing medication

26
Q

What are the signs and symptoms of metabolic acidosis?

A

-Weakness, fatigue, general malaise, vomiting, and abdominal pain
-Depression of neuronal excitability leads to drowsiness, altered LOC, stupor and coma
-Sympathetic tone of blood vessels decreases (hypotension, warm, flushed skin)
-Decreased cardiac contractility and responsiveness to catecholamines cause hypotension, tissue hypoxia and lethal arrhythmias

27
Q

What are changes in function happen in the body systems due to metabolic acidosis?

A

GI:
anorexia, nausea, vomiting, abdominal pain
Neural Function:
weakness, lethargy, malaise, confusion, stupid, coma, depression of VS
Cardiovascular Function:
peripheral vasodilation (hypotension), bradycardia, cardiac arrhythmias
Skin:
Warm, flushed. Skeletal - bone disease (chronic acidosis)
Compensation:
hyperkalemia, acid urine, increased RR and depth

28
Q

What compensation occurs due to metabolic acidosis?

A

Primary Disturbance:
⬇pH
⬇HCO3-
Respiratory Compensation:
⬆RR
⬇PCO2
Renal Compensation:
⬆H+ excretion
⬆HCO3- reabsorption

29
Q

What is metabolic alkalosis?

A

-A systemic disorder caused by an increase in plasma pH due to a primary excess in HCO3-
-Can result from a variety of situations including: Ingestion of antacids, vomiting and renal loss of H+

30
Q

What are the causes of metabolic alkalosis?

A

Excess Base Loading, Loss of Fixed Acid, Post-Hypercapneic Metabolic Alkalosis,

31
Q

What conditions can cause metabolic alkalosis?

A

-Excess administration of sodium bicarbonate when treating cardiac arrest (increased HCO3-)
-Prolonged volume depletion (excessive diuretic use)
-Prolonged vomiting (gastric loss of H+)
-Gastric suctioning (gastric loss of H+)
-Hyperaldosteronism (i.e. Cushing’s disease, renal loss of H+)

32
Q

How does excess base loading cause metabolic alkalosis?

A

-Rarely a cause of metabolic alkalosis due to the efficiency of healthy kidneys
-Excessive ingestion of HCO3- containing antacids, or IV sodium bicarb (NaHCO3)
-Calcium carbonate, sodium bicarbonate
-Gaviscon, Alia-Seltzer, Rolaids, Zantac, Tums

33
Q

How does loss of fixed acids cause metabolic alkalosis?

A

-Occurs mainly through loss of stomach acid (excess vomiting) and loss of Cl- in the urine - can also occur due to excessive gastric suctioning
-Gastric secretions contain HCl (hydrochloric acid)
-When Cl- is secreted into the stomach (from the blood) it is replaced with HCO3-
-Resultant volume depletion, hypochloremia and hypokalemia further worsen the alkalosis
-Increased HCO3- reabsorption in the kidneys

34
Q

What is Post-Hypercapnic Metabolic Alkalosis?

A

-Patients with chronic respiratory acidosis tend to have compensatory HCO3- retention along with H+ and Cl- loss in the urine
-Mechanical ventilation in attempt to correct the respiratory acidosis (lower the high levels of CO2) can lead to metabolic alkalosis
-PCO2 drops rapidly, but HCO3- levels remain elevate

35
Q

What conditions that accompany metabolic alkalosis can further worsen the problem?

A

Volume depletion, hypochloremia, hypokalemia, increased HCO3- reabsorption in the kidneys

36
Q

What are the clinical manifestations of metabolic alkalosis?

A

-Often asymptomatic or has signs related to volume depletion or hypokalemia
-Neurological S&S occur less frequently than with other acid-base disorders
-Confusion, hyperactive reflexes, tetany, carpopedal spasm
-Compensatory hypoventilation can occur which can lead to hypoxemia and respiratory acidosis
-Severe rise in pH can lead to respiratory failure, arrhythmias, seizure, coma

37
Q

What compensation occurs due to metabolic alkalosis?

A

Primary Disturbance:
⬆pH
⬆HCO3-
Respiratory Compensation:
⬇RR
⬆PCO2
Renal Compensation:
⬇H+ excretion
⬇HCO3- reabsorption

38
Q

What is respiratory acidosis?

A

-Results from conditions that impair alveolar ventilation and cause an increase in plasma PCO2 (hypercapnea) and a decrease in pH
-Can be acute or chronic but is often due to decreased ventilation
-Decreased respiratory drive, lung disease, disorders of chest wall and respiratory muscles. Rarely can occur from excess CO2 production

39
Q

What is acute respiratory acidosis?

A

hypoventilation causes rapid rise in PCO2, minimal increase in plasma HCO3-, and a large decrease in pH

40
Q

What is chronic respiratory acidosis?

A

sustained increase in PCO2 resulting in renal compensation (increased plasma HCO3- and slight decrease in pH)

41
Q

What are the causes of respiratory acidosis?

A

Acute Disorders of Ventilation, Chronic Disorders of Ventilation, Increased CO2 Production,

42
Q

What conditions can cause respiratory acidosis?

A

-Lung disease (i.e. COPD and pneumonia, causes impaired gas exchange, retention of CO2)
-Barbiturate or narcotic overdose (depression of respiratory center, retention of CO2)
-Head injury (brain damage, depression of respiratory center, retention of CO2)
-Any condition causing hypoventilation

43
Q

How does increased CO2 production cause respiratory acidosis?

A

-CO2 is a product of the body’s metabolic process
-Increased CO2 production can occur during exercise, fever, sepsis and burns
-Increased CO2 production usually only causes acidosis in people lung disease (can’t eliminate the excess CO2

44
Q

What are the clinical manifestations of respiratory acidosis?

A

-pH < 7.35, PCO2 > 45mmHg
-mixed with symptoms of hypoxemia (which usually present first)
-CO2 readily crosses the BBB, changing the pH of brain fluids
-Altered LOC from lethargy to coma develop as PCO2 rises
-CO2 causes vasodilation of cerebral blood vessels
-Headache, blurred vision, irritability, muscle twitching, psychological disturbances
-Mild acidosis can cause warm flushed skin, weakness and tachycardia

45
Q

What are the system signs and symptoms of respiratory acidosis?

A

Neural Function:
-dilation of cerebral vessels and depression of neural function.
-Headache, weakness, behavior changes, confusion, depression, paranoia, hallucinations, tremors, paralysis, stupor, coma
Skin:
-warm and flushed
-Compensation - acidic urine

46
Q

What is the treatment for respiratory acidosis?

A

Directed at improving ventilation and lowering PCO2

47
Q

How does the body compensate for respiratory acidosis?

A

Primary Disturbance:
⬇pH
⬆PCO2
Respiratory Compensation:
None
Renal Compensation:
⬆H+ excretion
⬆HCO3- reabsorption

48
Q

What is respiratory alkalosis?

A

A systemic disorder characterized by a primary decrease in plasma PCO2 (hypocapnea), which elevates pH and subsequently decreases HCO3-

49
Q

What conditions can cause respiratory alkalosis?

A

-Salicylate overdose (stimulation of respiratory center, loss of CO2)
-High fever (stimulation of respiratory center, loss of CO2)
-Hysteria/voluntary over breathing (hyperventilation, loss of CO2)
-Central or peripheral stimulation of the medullary respiratory center: anxiety, pain, pregnancy, fever, sepsis, encephalitis, salicylate toxicity
-Any condition resulting in hyperventilation

50
Q

How does a pulmonary embolism cause respiratory alkalosis?

A

dead space ventilation causes initial rise in PCO2. This is quickly detected by chemoreceptors and the RR compensates and quickly lowers the PCO2
levels to an alkaline level

51
Q

What are the clinical manifestations of respiratory alkalosis?

A

-pH > 7.45, PCO2 < 35mmHg
-Hyperexcitability of the nervous system
-Transient hypocalcemia
-Decreased cerebral blood flow
-Decreased CO2 concentration causes cerebral vasoconstriction
-CO2 crosses the BBB quickly, so neuro symptoms are usually sudden
-Light-headedness, dizziness, tingling, numbness of the fingers and toes, sweating, palpitations, anxiety, dyspnea, carpopedal spasm

52
Q

What are the system signs and symptoms of respiratory alkalosis?

A

Neural Function:
-constriction of cerebral blood vessels and increased neural excitability.
-Dizziness, panic, light-headedness. Tetany, numbness of fingers and toes, seizures,
carpopedal spasm
-Carpopedal Spasm - frequent, and painful, involuntary muscle contractions of the hands
and feet (mostly hands)
Cardiovascular Function:
-cardiac arrhythmias

53
Q

How does the body compensate for respiratory alkalosis?

A

Primary Disturbance:
-⬆pH
-⬇PCO2
Respiratory Compensation:
-None
Renal Compensation:
-⬇H+ excretion
-⬇HCO3- reabsorption

54
Q

What different levels would be seen in someone experiencing metabolic acidosis?

A

pH < 7.35
CO2 —> 35-45mmHg
HCO3- < 22mEq/L

55
Q

What different levels would be seen in someone experiencing metabolic alkalosis?

A

pH > 7.45
CO2 —> 35-45mmHg
HCO3- > 26mEq/L

56
Q

What different levels would be seen in someone experiencing respiratory acidosis?

A

pH < 7.35
CO2 > 45mmHg
HCO3- –> 22-26mEq/L

57
Q

What different levels would be seen in someone experiencing respiratory alkalosis?

A

pH > 7.45
CO2 < 35mmHg
HCO3- –> 22-26mEq/L

58
Q

How does crush syndrome cause metabolic acidosis?

A

-Anaerobic metabolism occurs due to disrupted tissue perfusion, lactic acid production
-Muscle cell necrosis causes rhabdomyolysis, destruction of muscle cells releasing their electrolytes and proteins
-When the crushing force is released, these harmful agents are released back into
systemic circulation

59
Q

How does head/spine injury cause respiratory acidosis?

A

-Traumatic damage to the respiratory center in the medulla can cause respiratory depression and CO2 retention
-Spinal cord damage innervating the respiratory muscles can cause a decrease in their
function and impaired ventilation
-Decreased ventilatory efficiency leads to a buildup of CO2

60
Q

How does chest trauma causes respiratory acidosis?

A

results in a decrease in lung inflation or a decrease
in the surface are for gas exchange (decreased exhalation of CO2
Ex. Pneumothorax, Pulmonary Edema, Pulmonary Contusion

Patho (9 decks)

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