Box 1 ( EVERYDAY) Flashcards
a substance that can yield a hydrogen ion
(H+) or hydronium ion (H30+)when dissolved in water
Acid
a substance that can yield hydroxyl ions (OH-)
Base
defined as the negative log of the ionization constant, is also the pH in which the protonated and unprotonated forms are present in equal concentrations.
measures the strength of an acid in solution. Also known as the “acid dissociation constant”.
pKa
Pk values < 3
Strong acids
Pk values >9
Strong bases
For acids, raising the pH
above the pK will cause _____.
will cause the acid to dissociate and yield
an H+.
For bases, lowering the pH below the pK will cause_____.
will cause the base to release OH+.
the combination of a weak acid or weak
base and its salt, is a system that resists changes in pH.
Buffer
effectiveness of a buffer depends on the _____ and the in ___________.
.
on the pK of the
buffering system , pH of the environment which it is placed
has pK of 6.1, and is one of the principal
buffers in the plasma
bicarbonate–carbonic
A scale used to measure the acidity or basicity of an aqueous solution.
pH
pH < 7
acid
pH > 7
base
reference value for blood plasma pH is _____
7.40
an increase in H+ concentration
____ the pH
decreases
decrease in H+
concentration _____ the pH
increases
normal pH of H+ in the extracellular body fluid ranges from ______.
pH 7.34–7.44 (36–44 nmol/L)
reference value for arterial blood pH is
7.40
below the reference
range (<7.34) is referred to as ____ , whereas a
pH above the reference range (>7.44) is referred to as
______.
acidosis , alkalosis
Three reasons why bicarbonate-carbonic acid system is still an important buffer in the system.
(1) H2CO3 dissociates into CO2 and H2O,
allowing CO2 to be eliminated by the lungs and H as
water; (2) changes in CO2 modify the ventilation (respiratory)
rate; and (3) HCO3-concentration can be altered
by the kidneys.
Partial pressure of oxygen
pO2
Reference value pO2
81 - 100 mmHg
Mild hypoxemia
61 - 80 mmHg
Moderate hypoxemia:
41 – 60 mmHg
Severe hypoxemia:
<41 mmHg
Partial pressure of carbon dioxide.
pCO2
Reference value pCO2:
35 – 45 mmHg
Respiratory alkalosis:
<35 mmHg
Respiratory acidosis: pCO2
> 45 mmHg
its salt or conjugate base for the bicarbonate–carbonic acid buffer system
bicarbonate
HCO3-
weak acid of bicarbonate–carbonic acid buffer system
carbonic acid (H2CO3)
When an acid is added to the bicarbonate–carbonic acid system, the HCO3- will combine with the H+ from the acid to form _____.
H2CO3
When a base is added, H2CO3 will combine with the OH group to form____.
H2O and HCO3
Conjugate base of bicarbonate-carbonic acid. 20:1 ratio with H2CO3
HCO3–
Reference value of HCO3-:
21 – 28 mEq/L
Metabolic alkalosis:
> 28 mEq/L
Metabolic acidosis:
<21 mEq/L
1:20 ratio with HCO3
Bicarbonate
reference value of H2CO3
1.05 - 1.4 mEq/L
CO2 excess.
RESPIRATORY ACIDOSIS
Compensated by the kidneys (↑ HCO3– against ↑ pCO2 and pH < 7.35)
RESPIRATORY ACIDOSIS
CO2 deficit.
RESPIRATORY ALKALOSIS
Compensated by the kidneys (↓ HCO3– against ↓ pCO2 and pH > 7.45)
RESPIRATORY ALKALOSIS
HCO3– deficit.
METABOLIC ACIDOSIS
Observed in COPD, myasthenia gravis, CNS diseases, drug overdose, botulism, stroke, myxedema, and pneumonia.
RESPIRATORY ACIDOSIS
Observed during anxiety, severe pain, aspirin/salicylate overdose, hepatic cirrhosis, Gram (-) sepsis, progesterone drugs intake.
RESPIRATORY ALKALOSIS
Observed in diabetic ketoacidosis, lactic acidosis, renal failure, and diarrhea.
METABOLIC ACIDOSIS
Compensated by the lungs (↓ pCO2 against ↓ HCO3– and pH < 7.35)
METABOLIC ACIDOSIS
HCO3– excess.
METABOLIC ALKALOSIS
Observed in vomiting (chloride loss).
METABOLIC ALKALOSIS
Compensated by the lungs (↑ pCO2 against ↑ HCO3– and pH > 7.45)
METABOLIC ALKALOSIS
Most severe. Inappropriate compensation. The blood pH determines the dominant disorder.
MIXED ACID-BASE DISORDER
an important factor in maintaining the normal biological processes of an organism
Blood pH
Anticoagulant to use is_____ grams of _____ per ml of blood.
0.05 , dry heparin
Use syringe and needle and must be _____ prior to blood collection.
pre-heparinized
Upon completion of the draw, ______.
remove the trapped air .
Arterial blood has _____,_____ , and slightly basic than venous blood (-0.03).
> pO2 ,
Common pre-analytical errors
form and concentration of heparin, speed of syringe filling, air exposure, mixing of samples, collection device, pre-analytical storage/transport time. Specimen exposed to air loses pCO2
Common analytical errors
temperature and protein coating of electrodes.
Gasometers for BGA
Van Slyke manometer Natelson gasometer
measures pCO2 and pO2
Van Slyke manometer
Natelson gasometer utilizes ____??
- mercury - produces vacuum
- caprylic alcohol – anti-foam agent
- lactic acid – counteracts presence of pyruvate/lactate
- NaOH and NaHSO3 – buffer system
Electrodes
pH (potentiometry)
pO2 – Clark electrode (polarography-amperometry)
pCO2 – Severinghaus electrode (potentiometer)
measure the
amount of current flow in a circuit that is related to the
amount of O2 being reduced at the cathode.
Clarke electrodes
Formula for acid base balance
pH = pKa + log ([A-]/[HA])
pKa = ____
6.1, dissociation constant for CO2
A- = ____
concentration of HCO3–
HA = ______
concentration of H2CO3
AG = (Na+ + K+) - (Cl- + HCO3-)
Indicator if acidosis is due to increased acid accumulation or bicarbonate loss. May also indicate presence of mixed acid-base disorder.Reference value: 3 – 11 mEq/L
Correction by changes in temperature: Normal temperature is 37°C, each exceeding degree, decrease _____ and _______.
pO2 by 7%, increase pCO2 by 3%
Normal arterial blood pH =
7.35 – 7.45
Increase in pCO2= ____ in pH
Decrease
Decrease in pCO2=____ in pH
Increase
The relation of pCO2 and pH is _____
Indirectly proportional
The relation of pO2 and pH is _____
Directly proportional
20:1 ratio to Bicarbonate
Carbonic acid
