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Pathophysiology > 5.1 Acid Base Balance and Disorders > Flashcards

5.1 Acid Base Balance and Disorders Flashcards

1
Q

pH

A
  • Level of acidity or alkalinity of fluids
  • If pH moves from 6 to 5 concentration of H+ has increased by 10 times
  • If H+ is high the fluid is acidic
  • If H+ is low the fluid is alkaline
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2
Q

Regulation of pH

A
  • Acid is the end product of protein, fat, and carbohydrate metabolism
    VOLATILE - Carbonic Acid (H2CO3) (Eliminated as CO2)
    NONVOLATILE - Sulfuric, Phosphoric, other Organic Acids
    Eliminated as Ammonium (NH4+) and regulation of Bicarbonate (HCO3-)
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3
Q

pH

A

Normal range 7.35 - 7.45

- Regulated mainly by lungs and kidneys

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4
Q

Buffers

A
  • They are weak acids and conjugate bases that bind to excessive H+ or OH- without causing change in pH
  • Lungs blow off CO2 to regulate Carbonic Acid
  • Kidneys excrete HCO3- by producing alkaline/acidic urine.
  • These are compensatory mechanisms
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5
Q

Buffering Action of Hemoglobin

A
  • CO2 is a waste product of cellular metabolism
  • O2 is exchanged for CO2
  • When CO2 enters the blood it is quickly dissolved and ionized
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6
Q

Hemoglobin in Acidosis

A
  • Potassium and H+ have inverse relationship in acidosis. Potassium leaves cells and H+ goes into cells. Because of this acidosis may cause hyperkalemia
  • The same is true vice-versa
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7
Q

Buffering Action of Kidneys

A

Kidneys excrete ammonia and phosphate to maintain the bodies pH levels.

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8
Q

Protein Buffer System

A
  • Largest buffer system in the body
  • Proteins can function as both acid or bases
    BONE BUFFER SYSTEM
  • Excess H+ can be exchanged for sodium and potassium on the bone surfaces.
  • Dissolution of bone minerals cause the release of sodium bicarbonate and calcium bicarbonate into ECF
  • These can be used to buffer acids
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9
Q

Acid-Base Imbalance

A

Acidosis - Increased H+
(pH < 7.35)
Alkalosis - Decreased H+
(pH > 7.45)

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10
Q

Acidosis/Alkalosis

A

Respiratory Acidosis - Elevation of CO2 (Less Respirations)
Respiratory Alkalosis - Decreased CO2 (Hyperventilation)
Metabolic Acidosis - Decrease in HCO3 or increase in non-carbonic acids
Metabolic Acidosis - Elevation in HCO3 usually due to excessive loss of metabolic acids

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11
Q

The Anion Gap

A

(Na+ + K+) - (Cl- + HCO3-) = Anion Gap
Normal Range 10 - 12 mEq/L
Abnormal > 14

Other Anions (lactate, pyruvate, other metabolic acids)

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12
Q

Respiratory Buffer

A
  • An increase in respiration rate or blowing off CO2 quickly compensates for acidosis
  • It is not a good system to compensate for metabolic alkalosis
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13
Q

Renal Buffer System

A
  • Conversion/Excretion of HCO3-
  • Takes a long time
  • Useful for chronic hypercapnia
  • Not very useful in acute respiratory acidosis
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14
Q

Normal ABG Ranges

A

pH (7.35 - 7.45) - Lower is acidosis, higher is alkalosis

PCO2 (Respiratory) 35-45 mmHg
Higher is acidosis, lower is alkalosis

HCO3 (Metabolic) 22-26 mEq/L
Lower in acidosis, higher in alkalosis

BE (Base Excess) +/- 2 mEq/L
Lower in acidosis, higher in alkalosis

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15
Q

How to Interpret ABG

A

Step 1 - Is it normal, acidosis or alkalosis
Step 2 - Is it Respiratory or Metabolic Acidosis
(ROME) - Respiratory Opposite, Metabolic Equal

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16
Q

Compensation

A
  • Patient has normal pH but abnormal CO2 or HCO3
17
Q

Primary Respiratory Acidosis

A
  • Increase in Carbonic Acid (H2CO3)

- Retention of CO2

18
Q

Etiology/Common Causes (Respiratory Acidosis)

A

Etiology - Hypoventilation (Increased CO2)

Common Causes

  • Over sedation and depression of respiratory system
  • Brain stem trauma with damage to respiratory center
  • COPD (CO2 Retention)
  • Sleep Apnea (retention of co2 due to obstructed airway)
19
Q

Compensation/Correction (Respiratory Acidosis)

A

Compensation - Stimulates kidneys to excrete H+ as ammonia or H2PO4 and retain Bicarbonate

Correction - Increase alveolar ventilation

20
Q

Clinical Manifestation (Respiratory Acidosis)

A 
Clinical Manifestations
- Notable decrease in rate/depth or respirations
- Sensorium 
CO2 crosses BBB (lipophilic) 
HCO3 Does not Cross (hydrophilic) 
- Headache, Restlessness, Apprehension (anxiety)
- Confusion, Lethargy, Tremors
- Seizures and Coma
21
Q

Diagnosis/Treatment Respiratory Acidosis

A

pH - Less than 7.5

  • Increased pCO2 (Hypercapnia) and decreased O2 (Hypoxia)
  • Increased HCO3- (Bicarbonate) which results in renal compensation
  • Lactic Acidosis, in presence of anaerobic metabolism

Treatment

  • Restore alveolar ventilation.
  • Oxygen, intubation, mechanical Ventilation
  • Narcotic reversal agent (if due to narcotic overdose)
22
Q

Primary Respiratory Alkalosis

A
  • Decrease in carbonic acid due to hyperventilation and excess loss of carbon dioxide.
23
Q

Common Causes (Respiratory Alkalosis)

A
  • Hypoxemia (low oxygen) pulmonary/circulatory disease
  • Hyperdynamic states (sepsis, fever, thyrotoxicosis too much thyroid hormone)
  • Improper ventilator settings
  • Brain stem lesions
  • Salicylate (OTC) poisoning (in combination with metabolic acidosis
24
Q

Etiology/Compensation (Respiratory Alkalosis)

A

Etiology - Hyperventilation (decreased co2)

Compensation

  • Begin exchanging H+ for K+ in RBC
  • Kidneys compensate by retaining H+ and excreting HCO3-
25
Q

Clinical Manifestation (Respiratory Alkalosis)

A
  • Increased rate/depth of respirations (blowing out co2)
  • Alkalization of plasma leading to decrease in ionized calcium
  • This causes tingling in extremities, circumoral numbness, neuromuscular weakness, changes in sensorium, dizziness, confusion, seizures.
26
Q

Diagnosis/Treatment (Respiratory Alkalosis)

A

Diagnosis

  • pH > 7.45
  • Decreased pCO2 < 35 mmHg (Hypocapnia)
  • Normal or slightly elevated HCO3

Treatment

  • Administer oxygen for hypoxic
  • Adjust mechanical ventilation
  • Assist with rebreathing CO2 (paper bag)
27
Q

Primary Metabolic Acidosis

A
  • Increase in non-carbonic acids or loss of bicarbonate
28
Q

Common Causes (Metabolic Acidosis)

A
  • Lactic Acidosis from reliance on Anaerobic Metabolism
  • Renal Failure (retention of metabolic acids)
  • Diabetic Ketoacidosis (reliance of protein and fat for energy resulting in production of acids)
  • Diarrhea (loss of alkaline duodenal secretions)
29
Q

Etiology (Metabolic Acidosis)

A
  • Decrease in Base (HCO3-) due to loss

- Increase in Metabolic Acid (H+) due to retention or increased production

30
Q

Compensation (Metabolic Acidosis)

A
  • Respiratory system blows off CO2

- Renal system increases excretion of ammonium and phosphate. This lowers H+ available to form carbonic acid.

31
Q

Clinical Manifestation (Metabolic Acidosis)

A
  • Headache, Lethargy
  • Anorexia, Nausea, Vomiting
  • Progression to Coma
  • Hyperventilation
  • Kussmaul (rapid, deep, heaving) respirations to compensate severe metabolic acidosis
  • Lethal Dysrhythmias
32
Q

Diagnosis/Treatment (Metabolic Acidosis)

A
  • pH < 7.35
  • Normal/Decreased pCO2 (Insufficient to offset acidosis)
  • Decreased HCO3
  • Serum Lactate/Ketones for lactic acidosis or diabetic ketoacidosis.

Treatment

  • Treat underlying cause
  • Judicious use of sodium bicarbonate (if used at all)
33
Q

Primary Metabolic Alkalosis

A
  • Decrease of non-carbonic acids or gain in bicarbonate via reabsorption or lack of consumption.
34
Q

Common Causes Diabetic Alkalosis

A
  • Loss of gastric acids from prolonged vomiting or GI suction
  • Renal Retention of Bicarbonate
  • Excess consumption of antacids such as magnesium hydroxide
  • Excessive bicarbonate intake
  • Diuretic Therapy
35
Q

Etiology of Diabetic Alkalosis

A
  • Increase in base (HCO3) due to retention or decreased consumption
  • Decrease in metabolic acids (H+) due to loss of production resulting in net gain of base bicarbonate
36
Q

Compensation (Diabetic Alkalosis)

A

Respiratory - Hypoventilation resulting in increase of PaCO2 and H2CO3

Renal - Kidneys retain H+ and excrete bicarbonate
(Not effective if patient is dehydrated or has electrolyte imbalance)

37
Q

Clinical Manifestation

A
  • Signs and symptoms of underlying cause (GI)
  • Paresthesia (pins and needles) and muscle weakness with decreased ionized calcium (alkaline environment)
  • Hypoventilation (retention of co2)
  • Confusion/seizures in severe cases
38
Q

Diagnosis/Treatment Metabolic Alkalosis

A
  • pH > 7.45
  • Normal or increased PCO2 (Insufficient to offset alkalosis)
  • Increased HCO3
    Hypochloremia (gastric suctioning)

Treatment
Treat underlying cause

39
Q

Complex Acid Base Balances

A
  • Primary imbalance is offset my a secondary imbalance that returns pH to normal ranges. (2 wrongs make a right)
  • Mixed imbalances of both respiratory and metabolic acidosis/alkalosis.
    (Diabetic Ketoacidosis and Lactic Acidosis)

Pathophysiology (18 decks)

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