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Renal and urology > Acid-Base balance > Flashcards

Acid-Base balance Flashcards

1
Q

What is the normal range for [H+] in nmol/L?

A

35 – 45 nmol/L

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2
Q

What is the normal pH range for acid-base balance?

A

7.35 – 7.45

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3
Q

What is the formula for calculating pH from [H+]?

A

pH = -log10[H+]

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4
Q

What are the primary sources of acid production in the body?

A
  • Cellular respiration (producing CO2)
  • Metabolic processes (producing non-volatile acids like ketones and lactate)
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5
Q

What is the daily production of CO2 in mol?

A

~12 mol CO2 per day

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6
Q

What is the typical daily production of non-volatile acids in mmol?

A

~60 mmol non-volatile acids per day

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7
Q

What are the three main mechanisms of acid-base homeostasis in the body?

A
  • Buffers (rapid)
  • Lungs (fast)
  • Kidneys (slow)
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8
Q

What is the role of buffers in acid-base homeostasis?

A

They rapidly stabilize pH by neutralizing excess acids or bases.

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9
Q

How do the lungs contribute to acid-base balance?

A

They remove CO2, which helps to regulate pH.

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10
Q

What is the Henderson-Hasselbalch equation?

A

pH = 6.1 + log10([HCO3-] / (pCO2 x 0.23))

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11
Q

What is acidaemia?

A

[H+] > 45 nmol/L and pH < 7.35

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12
Q

What is alkalaemia?

A

[H+] < 35 nmol/L and pH > 7.45

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13
Q

What is respiratory acidosis?

A

A condition characterized by elevated pCO2 due to hypo-ventilation.

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14
Q

What is metabolic acidosis?

A

A condition characterized by overproduction of acids or impaired excretion.

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15
Q

What causes metabolic alkalosis?

A

Unusual losses of H+ or excessive ingestion of HCO3-.

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16
Q

What is the significance of base excess in blood gas analysis?

A

It indicates the amount of H+ needed to return to normal pH at a standard pCO2.

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17
Q

What is the standard reference range for HCO3-?

A

21 – 29 mmol/L

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18
Q

What does a negative base excess indicate?

A

It suggests metabolic acidosis.

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19
Q

What does a positive base excess indicate?

A

It suggests metabolic alkalosis.

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20
Q

What are the key components required for interpreting arterial blood gases (ABGs)?

A
  • pH or [H+]
  • pO2
  • pCO2
  • [HCO3-]
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21
Q

What is the role of the kidneys in acid-base homeostasis?

A

They excrete H+ and regenerate HCO3-.

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22
Q

True or False: Venous blood gas samples can sometimes be used instead of arterial samples.

A

True

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23
Q

What are some common causes of unusual losses that lead to metabolic alkalosis?

A
  • Vomiting
  • Diuretic therapy
  • Dehydration
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24
Q

What is the typical method for measuring HCO3- in blood gas analysis?

A

HCO3- is calculated based on the measured pCO2 and pH.

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25
Q

Fill in the blank: The kidneys have a _______ response in acid-base homeostasis.

A

slow

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26
Q

What is respiratory alkalosis?

A

A condition characterized by decreased pCO2 due to hyper-ventilation.

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27
Q

What are the typical investigations for assessing acid-base disorders?

A
  • Arterial blood gas (ABG)
  • Venous gas
  • Clinical history and examination
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28
Q

What is the significance of the anion gap in acid-base disorders?

A

It helps to differentiate between causes of metabolic acidosis.

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29
Q

What does the term ‘mixed disorders’ refer to in acid-base balance?

A

Simultaneous presence of multiple acid-base disturbances.

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30
Q

What are mixed acid-base disorders?

A

Disorders where one or more pathologies simultaneously drive acid-base disorders.

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31
Q

What do shaded areas in acid-base disorder charts define?

A

Usual behavior of acid-base disorders, such as degree of attempted respiratory compensation.

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32
Q

What is metabolic acidosis with partial respiratory compensation?

A

A condition where metabolic acidosis is present alongside respiratory compensation.

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33
Q

What is the primary disorder in Case 1?

A

Metabolic acidosis.

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34
Q

Fill in the blank: The primary acid-base disturbance in Case 1 is _______.

A

metabolic acidosis.

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35
Q

What is the anion gap?

A

The difference between the most abundant cations and anions in the blood.

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36
Q

What does an elevated anion gap indicate?

A

It indicates certain types of metabolic acidosis.

37
Q

What are common causes of metabolic acidosis?

A
  • Increased acid formation
  • Reduced excretion
  • Loss of HCO3-
38
Q

What is the normal reference range for anion gap?

A

6 – 18 mmol/L.

39
Q

What is the compensatory mechanism for respiratory acidosis?

A

Metabolic alkalosis.

40
Q

What is the primary disorder in Case 2?

A

Respiratory acidosis.

41
Q

What is the effect of acute metabolic acidosis on oxygen delivery?

A

Initially facilitates O2 delivery, but after several hours it impairs O2 delivery.

42
Q

What is the consequence of chronic acidosis on bone?

A

Buffering by bone leads to decalcification.

43
Q

What are the pH levels of H+ in Case 1?

A

78 nmol/l.

44
Q

What would indicate a respiratory alkalosis condition?

A

Hyperventilation.

45
Q

True or False: Metabolic alkalosis can occur with respiratory compensation.

46
Q

What condition is indicated by HCO3- levels of 38 mmol/L?

A

Metabolic alkalosis.

47
Q

What is the typical compensation for metabolic acidosis?

A

Respiratory compensation through hyperventilation.

48
Q

What might cause confusion and restlessness in patients?

49
Q

What does renal tubular acidosis lead to?

A

Reduced excretion of HCO3-.

50
Q

What are the normal ranges for pCO2?

A

35 – 45 mmHg.

51
Q

What is the effect of H+ on the oxyhemoglobin dissociation curve?

A

Causes a right shift, facilitating O2 delivery.

52
Q

Fill in the blank: In metabolic acidosis, H+ levels can lead to impaired _____ delivery after several hours.

53
Q

What happens to potassium homeostasis during metabolic acidosis?

A

Leakage from cells causes high plasma K+.

54
Q

What is a potential cause of lactic acidosis?

A

Tissue hypoxia.

55
Q

What are typical symptoms of respiratory acidosis?

A
  • Cough
  • Wheeze
  • Breathlessness
56
Q

What is the primary compensation for respiratory acidosis?

A

Metabolic alkalosis.

57
Q

What does the term ‘decompensation’ refer to?

A

The failure of compensatory mechanisms in acid-base disorders.

58
Q

What is the impact of renal failure on acid-base balance?

A

It can lead to reduced excretion of acids and metabolic acidosis.

59
Q

What is respiratory acidosis?

A

A condition characterized by increased CO2 levels leading to decreased blood pH

Causes include airway obstruction, respiratory arrest, and chronic lung diseases.

60
Q

What are the causes of respiratory acidosis?

A
  • Acute airway obstruction
  • Cardio-respiratory arrest
  • Infective exacerbation (e.g., COPD, pneumonia)
  • Neurological causes (e.g., opiate toxicity, Guillain-Barre syndrome, myasthenia gravis)
  • Chronic COPD
  • Obesity (obstructive)
  • Pulmonary fibrosis (restrictive)
  • Neuromuscular diseases (e.g., MND, myopathy)

Differentiate between acute and chronic causes.

61
Q

What are the effects of hypercapnia in respiratory acidosis?

A
  • Shortness of breath (SOB)
  • Neurological effects (anxiety, coma, headache, myoclonus)
  • Cardiovascular effects (systemic vasodilatation)

Symptoms may vary based on underlying pathology.

62
Q

What is the primary disorder in case 3?

A

Acute respiratory alkalosis with no compensation

This is indicated by low CO2 levels and normal HCO3.

63
Q

What are the causes of respiratory alkalosis?

A
  • Acute conditions (e.g., asthma, COPD exacerbation, pulmonary embolism)
  • Pain or panic attacks
  • Iatrogenic causes (over-ventilation)
  • Altitude sickness
  • Inappropriate stimulation of the respiratory center (e.g., head injury, raised ICP)
  • Metabolic causes (e.g., hepatic encephalopathy, salicylate poisoning)
  • Pregnancy (physiological)

Distinguish between acute and chronic causes.

64
Q

What are the effects of respiratory alkalosis?

A
  • Acute hypocapnia
  • Cerebral vasoconstriction (lightheadedness, confusion, syncope)
  • Fall in ionized calcium (perioral and peripheral paraesthesia)
  • Increased heart rate and vasoconstriction

Symptoms may include chest tightness in patients with coronary artery disease.

65
Q

What is the primary disorder in case 4?

A

Metabolic alkalosis with partial respiratory compensation

Indicated by high HCO3 levels and elevated pCO2.

66
Q

What leads to metabolic alkalosis in case 4?

A

Severe vomiting

Vomiting causes loss of acid and leads to alkalosis.

67
Q

What are the potential causes of metabolic alkalosis?

A
  • Vomiting
  • Diuretics
  • Hyperaldosteronism
  • Cushing’s syndrome
  • Excessive intake of alkali
  • Hypokalemia

Each of these factors can contribute to an increase in blood pH.

68
Q

What is the significance of clinical context in diagnosing acid-base disorders?

A

Clinical context is crucial for interpreting lab results correctly

Results may appear normal without considering the patient’s symptoms and history.

69
Q

Fill in the blank: Respiratory acidosis is characterized by increased _____ levels.

70
Q

Fill in the blank: The primary compensatory mechanism for metabolic alkalosis is _____ respiration.

A

respiratory

71
Q

What is the equilibrium reaction for bicarbonate?

A

HCO3- + CO2 + H2O ⇔ H2CO3 ⇔ H+ + HCO3-

72
Q

What is respiratory acidosis caused by?

A

Hypoventilation, over-production of CO2, impaired excretion of H+

73
Q

What are the causes of metabolic acidosis?

A

Unusual losses of H+, overproduction of H+, impaired renal excretion

74
Q

What causes metabolic alkalosis?

A

Loss of H+ ions, gain of HCO3-, unusual ingestion of bicarbonate

75
Q

What is a common effect of metabolic alkalosis?

A

May cause a shift of K+ into cells

76
Q

What is the significance of IV sodium bicarbonate in CKD?

A

Can exacerbate metabolic acidosis

77
Q

What should be considered when interpreting blood gas results?

A

Adequate oxygenation, pH or [H+], pCO2 disturbance, [HCO3-] disturbance

78
Q

What is the primary disturbance in acid-base disorders usually matched with?

A

Underlying cause and direction of [H+] change

79
Q

How does renal compensation for respiratory acidosis occur?

A

Slowly and usually only in chronic respiratory acidosis

80
Q

What are the primary acid-base disturbances?

A

Respiratory acidosis, respiratory alkalosis, metabolic acidosis, metabolic alkalosis

81
Q

In what condition is compensation for alkalosis usually limited?

A

Metabolic alkalosis

82
Q

What should be checked if blood gas interpretation does not make sense?

A

Error in blood sampling, transport, or measurement

83
Q

What categories do causes of acid-base disorders fall into?

A

Abnormal acid production, respiratory and renal pathologies, fluid loss

84
Q

What is crucial for acid-base homeostasis?

A

Maintaining a balance against acidity

85
Q

What is the H-H equation used for?

A

Describing extracellular fluid acidity

86
Q

What is a key skill for managing patients with acid-base disorders?

A

Basic interpretation of blood gases

87
Q

What percentage of blood gases are typically easy to interpret?

88
Q

What should be sought out for practice in blood gas interpretation?

A

Examples from online resources, textbooks, and clinical placements

Renal and urology (13 decks)

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