Acid-Base-Electro

Question 1

Arterial [H+] is normally

Answer 1

40 nEq/L

Question 2

Normal arterial pH is

Answer 2

7.40

Question 3

is defined as an arterial pH below 7.35.

Answer 3

Acidaemia

Question 4

Alkalaemia is defined as an arterial pH above

Answer 4

7.45

Question 5

The value of pK, is 6.1, and the normal HCO; and PCO) are 24 mmol/L and 40 mmHg, respectively.

Answer 5

Henderson—Hasselbalch equation

Question 6

Physiological responses to changes in [H+] are characterized by three phases:

Answer 6

(1) immediate chemical buffering,
(2) respiratory compensation (whenever possible)
(3) a slower but more effective renal compensatory response that may nearly normalize arterial pH even if the pathological process remains present.

Question 7

Physiologically important buffers in humans include:

Answer 7

• bicarbonate (H2CO3/HCO3-),
• hemoglobin (HbH/ Hb-),
• other intracellular proteins (PrH/Pr—),
• phosphates (H2PO04-/HPO42-),
• ammonia (NH3/NH4+).

Question 8

is the most important buffer in the extracellular fluid compartment (effective against metabolic but not respiratory acid—base disturbances.)

Answer 8

Bicarbonate

Question 9

• though restricted inside red blood cells, also functions as an important buffer in blood.
• are important urinary buffers.

Answer 9

• Hemoglobin
• Phosphate and ammonium ions

Question 10

Has an important role in buffering the pH of the ICF of urine

Answer 10

Phosphate buffer system

Question 11

Contribute to the regulation of pH in the ECF and ICF; interact extensively with the other two buffer systems

Answer 11

Protein Buffer System

Question 12

Is most important in the ECF

Answer 12

Carbonic Acid-Bicarbonate Buffer System

Question 13

The major factors involved in the maintenance of acid-base balance

Answer 13

• Active tissues continuously generate carbon dioxide, which in solution forms carbonic acid. Additional acids, such as lactic acid, are produced inthe course of. normal metabolic operations.
• Buffer systems can temporarily store H+ and thereby provide short-term pH stability.
• The respiratory system plays a key role by eliminating carbon dioxide.
• The kidneys play a major role by secreting hydrogen ions into the urine and generating buffers that enter the bloodstream. The rate of excretion rises and falls as needed to maintain normal plasma pH. As a result, the normal pH of urine varies widely but averages 6.0—slightly acidic.

Question 14

Classes of acids

• Do not leave solution
• Remain in body fluids until kidney excretion
• Generated during catabolism of amino acids, phospholipids, and nucleic acids
• Examples: sulfuric and phosphoric acid

Answer 14

Fixed acids

Question 15

Classes of acids

• Part of cellular metabolism
• Examples: lactic acid and ketones
• Most metabolized rapidly so no accumulation

Answer 15

Organic acids

Question 16

Classes of acids

• Can leave body by external respiration
• Example: carbonic acid (H,CO3)

Answer 16

Volatile acids

Question 17

• Changes in alveolar ventilation responsible for it which Paco2 are mediated by chemoreceptors within the brainstem.
• These receptors respond to changes in cerebrospinal spinal fluid pH.
• Minute ventilation increases 1—4 L/min for every (acute) 1 mm Hg increase in Paco2.
• responses are also important in defending against marked changes in pH during

Answer 17

respiratory compensation

Question 18

Renal Compensation During Acidosis (12-24hr): maximal 5 days

Answer 18

(1) increased reabsorption of the filtered HCO3-
(2) increased excretion of titratable acids
(3) increased production of ammonia.

Question 19

Renal Compensation During Alkalosis

Answer 19

• Tremendous amount of HCO3 - normally filtered and subsequently reabsorbed allows the kidneys to rapidly excrete large amounts of bicarbonate, if necessary.
• Metabolic alkalosis is commonly associated with increased mineralo-corticoid activity

Question 20

• defined as a primary increase in Paco2.
  T- his increase drives the reaction: H20+CO2 —H2CO3 H+ +HCO3-
• leading to an increase in [H+] and a decrease in arterial pH.
• [HCO3-] is minimally affected.

Answer 20

RESPIRATORY ACIDOSIS

Question 21

The compensatory response to acute (6—12 h) elevations in Paco2 is limited. Buffering is primarily provided by hemoglobin and the exchange of extracellular H+ for Na+ and K+ from bone and the intracellular fluid compartment The renal response to retain more bicarbonate is acutely
very limited. As a result, plasma [HCO3-] increases only about 1 mEq/L for each 10 mm Hg increase in Paco2 above 40 mm Hg.

Answer 21

Acute Respiratory Acidosis

Question 22

“Full” renal compensation characteristics
- Renal compensation is appreciable only after 12-24 hr and may not peak until 3-5 days.
- plasma [HCO3-] increases approximately 4 mEq/L for each 10 mm Hg increase in Paco2 above 40 mm Hg.

Answer 22

Chronic Respiratory Acidosis

Question 23

defined as a primary decrease in [HCO3-]

Answer 23

Metabolic acidosis

Question 24

Pathological processes can initiate metabolic acidosis by one of three mechanisms:

Answer 24

(1) consumption of HCO3- by a strong nonvolatile acid
(2) renal or gastrointestinal wasting of bicarbonate
(3) rapid dilution of the extracellular fluid compartment with a bicarbonate-free fluid.

Question 25

Pulmonary compensatory response in a simple metabolic acidosis characteristically does not reduce Paco2 to a level that completely normalizes pH but can produce marked hyperventilation

Answer 25

Kussmaul’s respiration

Question 26

major plasma cations — major plasma anions

Answer 26

Anion gap

Question 27

The anion gap decreases by ___ mEq/L for every 1 g/dL reduction in plasma albumin concentration.

Answer 27

2.5

Question 28

Metabolic acidosis with an increased anion gap is characterized by an increase in relatively strong

Answer 28

nonvolatile acids

Question 29

Endogenously produced organic acids are normally eliminated by the kidneys in urine. Glomerular filtration rates below 20 mL/min (renal failure) typically result inprogressive metabolic acidosis from the accumulation of these acids.

Answer 29

Failure to Excrete Endogenous Nonvolatile Acids

Question 30

Severe tissue hypoxia following hypoxemia, hypoperfusion (ischemia), or an inability to utilize oxygen (cyanide poisoning) can result in lactic acidosis. Decreased utilization of lactate by the liver, and, to a lesser extent by the kidneys, is less commonly responsible for lactic acidosis; causes include hypoperfusion, alcoholism, and liver disease.

Answer 30

Increased Endogenous Nonvolatile Acid Production

Question 31

An absolute or relative lack of insulin can result in hyperglycemia and progressive ____ from the accumulation of B-hydroxybutyric and aceto- acetic acids. - may also be seen following starvation and alcoholic binges.

Answer 31

Ketoacidosis

Question 32

Ingestion of large amounts of salicylates frequently results in

Answer 32

metabolic acidosis

Question 33

rapidly accumulate and produce a high anion gap acidosis.

Answer 33

Salicylic acid and other acid intermediates

Question 34

Metabolic acidosis associated with a normal anion gap is typically characterized by

Answer 34

hyperchloremia

Question 35

increases to take the place of the HCO3- ions that are lost.

Answer 35

Plasma [Cl-]

Question 36

most commonly results from abnormal gastrointestinal or renal losses of HCO3-, or from excessive intravenous administration of 0.9% NaCl solution.

Answer 36

Hyperchloremic metabolic acidosis

Question 37

can potentiate the depressant effects of most sedatives and anesthetic agents on the central nervous and circulatory systems.

Answer 37

Acidemia

Question 38

Because most opioids are ___, acidosis can increase the fraction of the drug in the nonionized form and facilitate penetration of the opioid into the brain.

Answer 38

weak bases

Question 39

is defined as a primary decrease in Paco2. Mechanism is usually an inappropriate increase in alveolar ventilation relative to CO2 production.

Answer 39

Respiratory alkalosis

Question 40

Defined as a primary increase in plasma [HCO3-].

Answer 40

Metabolic alkalosis

Question 41

Most cases of metabolic alkalosis can be divided into:

Answer 41

(1) those associated with NaCl deficiency and extracellular fluid depletion (often described as chloride sensitive) (2) those associated with enhanced mineralocorticoid activity, commonly referred to as chloride-resistant

Question 42

DX OF ACID-BASE DISORDERS

Answer 42

1. Examine arterial pH: Is acidemia or alkalemia present? 2. Examine Paco2: Is the change in Paco2 consistent with a respiratory component? 3. If the change in Paco2 does not explain the change in arterial pH, does the change in [HCO3-] indicate a metabolic component? 4. Make a tentative diagnosis. 5. Compare the change in [HCO3-] with the change in Paco2. Does a compensatory response exist?

Question 43

Disorder: Primary Change: high PaCO2 Compensatory Response: high HCO3-

Answer 43

Respiratory Acidosis

Question 44

Disorder: Primary Change: low PaCO2 Compensatory Response: low HCO3-

Answer 44

Respiratory Alkalosis

Question 45

Disorder: Primary Change: low HCO3- Compensatory Response: low PaCP2

Answer 45

Metabolic Acidosis

Question 46

Disorder: Primary Change: high HCO3- Compensatory Response: high PaCO2

Answer 46

Metabolic Alkalosis