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Clinical BioChemistry > export_acidsbases (1) > Flashcards

export_acidsbases (1) Flashcards

1
Q

What are the normal reference ranges for pH, PCO2, and PO2?

A

pH=7.35-7.45
PCO2=38-42 torr or mmhg

PO2=80-100 torr or mmhg

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2
Q

What are the major blood buffer systems in the body?

A

o Protein

o Phosphate buffer

o Hemoglobin

o Bicarbonate/Carbonic Acid

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3
Q

What are buffers? What are the best kind?

A

· Substance that minimizes changes in pH

· The best buffers are weak acids or bases because they do NOT dissociate readily

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4
Q

What is pKa? equation?

A

it is the logarithm of the acid dissociation constant.

pka= -logka

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5
Q

What is the Henderson–Hasselbalch equation?

A

pH=pKa+log[A-]/[HA]

It can be used for pH calculation of a solution containing pair of acid and conjugate base

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6
Q

A buffer has the best buffering capability when…

A

pH=pka
or

[A-]=[HA]

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7
Q

What is the pka of the carbonic acid/bicarbonate buffer?

A

6.1

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8
Q

If pH changes are due to primary PCO2 changes it is called…

A

Respiratory

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9
Q

If pH changes are due to primary HCO3- changes it is called….

A

metabolic

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10
Q

Total (ct) CO2 in body are:

A

HCO3-
CO2 (g)

CO2 (dissolved)(ca)

H2CO3(trace/constant)

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11
Q

What is the Boyles and Charles law?

A

PV=nRT

correlates the volume of an ideal gas to temperature and pressure

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12
Q

What is Daltons law?

A

total pressure of gas mixture equals the sum of the partial pressures of each gas in the mixture.

Total pressure=sum of partial pressures

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13
Q

How would you find the partial pressure of O2 (20.9%)

A

20.9/100X(760-47)

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14
Q

What is Henry’s law?

A

the concentration of a dissolved gas equals the partial pressure of that gas times its solubility constant (a)

CO2(d)~PCO2(a)

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15
Q

Equation for total CO2

A

Total CO2=HCO3- + PCO2(a)

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16
Q

What is hypercapnia? Ranges?

A

too much CO2 in the blood

>45 mmhg/torr

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17
Q

What is hypocapnia?

A

low levels of CO2 in the blood

<35 mmhg/torr

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18
Q

What is used to monitor O2 levels in the blood?

A

Pulse Oximetry

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19
Q

What is the Haldane effect?

A

O2 affects the affinity of Hb for CO2/H+

increased O2–>decreased CO2 affinity

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20
Q

What are the ranges for mild, moderate and severe hypoxemia?

A

Mild:60-80
Moderate:50-60

Severe: <40

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21
Q

Alkalosis is a decrease in..

A

PCO2

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22
Q

What is the Bohr effect?

A

Hb’s oxygen binding affinity is inversely related to acidity and CO2

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23
Q

Affinity of Hb for oxygen depends on:

A
  • Temp
  • pH
  • PCO2
  • 2-3DPG
  • other hb species that are non-functional
24
Q

A Shift to the left creates a _____ hb affinity for O2 and can be caused by:

A

Increased affinity.
Caused by:

  • Increased pH
  • Decreased-
  • PCO2
  • 2-3,DPG
  • Temp
25
Q

A Shift to the right _____ Hb affinity for O2 and caused by:

A

Decreased affinity for O2
Caused by:

  • Deceased pH
  • Increased-
  • PCO2
  • 2,3 DPG
  • Temp
26
Q

What is the normal ratio of HCO3-/PCO2?

A

20/1

27
Q

What is primary compensation?

A

One parameter causing pH alteration

28
Q

What is Partial compensation?

A

opposite parameter changing (outside reference range) but pH remains abnormal.

29
Q

what is full compensation?

A
  • pH is restored
  • but parameters may or may not be within normal range
  • Ratio is normal
30
Q

What is overcompensation?

A

opposite acid base disturbance develops

31
Q

What is “mixed” compensation?

A

Classification of an acid base disturbance when both metabolic and respiratory are contributing to the acid base disturbance and correction isn’t expected.

32
Q

Respiratory Acidosis is due to?

A

Increased PCO2

33
Q

Metabolic acidosis is due to

A

decrease in HCO3-

34
Q

Respiratory Acidosis is due to

A

increase in PCO2

35
Q

Metabolic Alkalosis is due to

A

increase in HCO3-

36
Q

Respiratory Alkalosis is due to

A

decrease in PCO2

37
Q

What is the primary protein buffer?

A

Albumin

38
Q

How do protein buffers work?

A

pick up CO2 or H+
Carbamino

imidazole group

39
Q

Describe the phosphate buffer system

A
  1. works in plasma and renal tubular cells
  2. Plasma-
  3. HPO4:H2PO4 (exchange H+ for H20) Renal-
  4. Renal tubular cells form Ammonia from AA degradation–Excrete H+ in the form of NH4+
  5. Conservation of Na and buffering H+
40
Q

Respiratory center (medulla) is sensitive to:

A
  • PCO2
  • PO2
  • pH
  • Chemoreceptors; in aortic arch and carotid sinuses and are receptive to : dec PO2, pH change, and PCO2 change
41
Q

Renal compensation responds by…

A
  1. Na+-H+ exchange
  2. ammonia formation
  3. phosphate buffer system (HPO4-H2PO4)
  4. Reabsorption/excretion of bicarbonate
42
Q

Causes of Respiratory Acidosis

A
  • Increase in PCO2
  • Hypoventilation
  • Respiratory Center depression (alcohol, barbiturates, CO2, morphine, anesthesia)
  • Asphyxia
  • Pulmonary disease
  • Decreased cardiac output
  • Apnea
43
Q

Causes of Respiratory Alkalosis

A
  • Decrease CO2
  • hyperventilation
  • Respiratory Center Stimulation (CNS disease, Drug toxicity, salicylate poisoning, quinine, sulfonamides)
  • hypoxia
  • hiccups
  • high room or ambient temperature
44
Q

PO2 of alveolar air is greater than or less than that of inspired air?

A

Less Than

45
Q

Diffusion rate of O2 in blood is _____ that of CO2.

A

1/20

46
Q

What is the PO2 of venous blood? Arterial?

A

Venous: 40
Arterial: 90

47
Q

causes of metabolic acidosis?

A
  • decrease in HCO3
  • Excess organic acids:
  • –Diabetes, ketoacidosis, impaired liver function, endocrine disorder, convulsions, hypoxia –>lactic acid, shock, late stage salicylate intoxication, MEOH ingestion, ethylene glycol ingestion Excess loss of bicarbonate:
  • –Diarrhea, Addisons dis, Renal tubular disease, GI/Pancreatic disease
48
Q

Causes of Metabolic Alkalosis

A
  • Excess loss of Acid (H+ + HCL)
  • Vomiting, diuretics, lavages
  • Body deficit of K+ (the less K+, more H+ exchanged for Na creating more acidic urine, alkaline plasma)
  • increased reabsorption of HCO3- (edema)
  • Hyperaldosteronism (loss of K)
49
Q

What is the effect of using a tourniquet for blood gas samples?

A
  • creates stasis
  • decreasing PO2 & pH
  • increasing PCO2
50
Q

What is ABE?

A

ABE stands for base excess and it is a clacluation reflecting the possible amount of actual base needed (lost) independent of the PCO2 in non-respiratory conditions

51
Q

Which component is always calculated in a blood gas determination?

A

HCO3 (Bicarbonate)

52
Q

What type of sample could be used for a blood gas analysis?

A

Heparinized, arterial, venous, capillary, and cord blood

53
Q

What would be the acid base disorder in a Unconscious patient- known drug overdose (oxycodone) with respiratory depression

A

—Mixed acid-base disorder
An unconscious patient is experiencing shock and buildup of lactic acid- (Resp alkalosis/Metabolic Acidosis?) in the case of the overdose patient, the drug was oxycodone a morphine derivative that can cause CNS depression- (Resp, Acidosis)

54
Q

What would be the acid-base disorder in a p atient experiencing pneumonia, anxious and hyperventilating?

A

Respiratory Alkalosis
Pt. would have a decreased PCO2 with possible decreased gas exchange due to the pneumonia

55
Q

Would would the acid base disorder be in a p atient with severe sleep apnea and decreased cardiac output (CHF).

A

—Respiratory Acidosis

reduced cardiac output can have a buildup of CO2 in the tissue and apnea can further cause the increase in CO2.

56
Q

What impact does an acidosis have on the compensatory mechanisms discussed?

A

Increase Na-H exchange (Na in and H out) HCO3 reabsorption,
ammonia formation, and phosphate buffer system

Clinical BioChemistry (2 decks)

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