Blood Gases, pH, and Buffer Systems Flashcards
a substance that can yield a hydrogen ion (H+) or hydronium
ion when dissolved in water
Acid
a substance that can yield hydroxyl ions (OH-)
Base
substance that DONATES a proton in a reaction
Acid
substance that ACCEPTS a proton in a reaction
Base
the negative log of the ionization constant
pKa
pH in which the protonated and unprotonated forms are present in equal concentrations
pKa
Strong acids have pKa values of _____.
<3.0
Strong bases have pKa values ______.
> 9.0
For acids, raising the pH above the pKa will cause the acid to
_______ and yield ____.
dissociate, H+
For bases, lowering the pH below the pKa will cause the base to
release _____.
OH-
resists change in pH upon adding acid or base
Buffer
the combination of a weak acid or weak base and its salt
Buffer
Normal concentration for maintenance of H+ with pH
36 to 44 nmol/L, 7.34 to 7.44
Outside of the normal range for maintenance of H+ could mean?
Alterations in consciousness
Neuromuscular irritability
Tetany
Coma
Death
Arterial blood pH (nmol/L)
7.40 (40 nmol/L)
pH is _______ proportional to H+
inversely
the body’s first line defense against extreme changes in H+ concentration
Bicarbonate-carbonic acid system
Bicarbonate-carbonic acid system is consist of a weak acid such as?
carbonic acid (H2CO3), and its salt/conjugate base
bicarbonate (HCO3)
HCO3:H2CO3 ratio must be ____ to maintain normal pH
20:1
plays a role in plasma and red blood cells and is involved in
the exchange of sodium ion in the urine H+ filtrate
Phosphate buffer system
It is used for regulation of H+
Buffer systems
imidazole groups of histidine
Plasma proteins
most circulating proteins have a net ___________ and are
capable of __________.
negative charge, binding H+
Lungs is through ____________ or ____________.
gas exchange, respiration
Lungs has _____ and ______ term compensation.
rapid, short
Lungs controls?
carbon dioxide (CO2)
Kidneys is through ___________ or __________________.
reabsorption, excretion of bicarbonate
Kidneys has a _______ but _____ term compensation.
slow, long
Kidneys controls?
bicarbonate (HCO3)
Expresses the acid-base relationships in a mathematical formula.
Henderson-Hasselbalch Equation
formula for pH wherein kidneys is the numerator and lungs is the denominator.
pH = 6.1 + log salt/acid or
pH = 6.1 + log HCO3/H2CO3
formula for H2CO3?
H2CO3 = pCO2 x 0.0307
formula for HCO3
HCO3 = Total CO2 - H2CO3
pH is _______ proportional to bicarbonate.
directly
pH is ________ proportional to the partial pressure of carbon dioxide.
inversely
pH - arterial blood gas reference range
7.35 to 7.45
pCO2 (mmHg) - arterial blood gas reference range
35 to 45
HCO3 - arterial blood gas reference range
22 to 26
Total CO2 content (mmol/L) - arterial blood gas reference range.
23 to 27
pO2 (mmol/L) - arterial blood gas reference range
80 to 110
SO2 (%) - arterial blood gas reference range.
> 95
O2Hb (%) - arterial blood gas reference range.
> 95
pH is less than the reference range
Acidemia
pH is greater than the reference range
Alkalemia
a disorder caused by ventilatory dysfunction (a change in pCO2, the respiratory component)
Primary Respiratory Acidosis or Alkalosis
a disorder resulting from a change in the bicarbonate level (a renal or metabolic function)
Nonrespiratory disorder
the body accomplishes to restore acid-base homeostasis by
altering the factor not primarily affected by the pathologic process.
Compensation
implies that the pH is has returned to the normal range
Fully compensated
implies that the pH is approaching normal. while compensation may successfully return the ratio to the normal 20:1, the primary abnormality is not corrected.
Partially compensated
pH is abnormal, pCO2 or HCO3 is normal, but not both
Uncompensated
pH of respiratory acidosis (increase or decrease)
decrease
pH of respiratory alkalosis (increase or decrease)
increase
pH of metabolic acidosis (increase or decrease)
decrease
pH of metabolic alkalosis (increase or decrease)
increase
disturbance in respiratory acidosis
hypoventilation, increased pCO2
disturbance in respiratory alkalosis
hyperventilation, decrease pCO2
disturbance in metabolic acidosis
decrease reabsorption and HCO-3, increase excretion
disturbance in metabolic alkalosis
increase reabsorption and HCO-3, decrease excretion
Compensation in respiratory acidosis
increase reabsorption, increase HCO-3
Compensation in respiratory alkalosis
increase excretion, decrease HCO-3
Compensation in metabolic acidosis
hyperventilation, decrease PCO2
Compensation in metabolic alkalosis
hypoventilation, increase pCO2
The amount of O2 available in atmospheric air depends on the?
Barometric pressure (BP)
Partial pressure of O2 at sea level (in the body)
(760 mm Hg – 47 mm Hg) x 20.93%
149 mm Hg (at 37ºC)
Partial pressure of CO2 at sea level (in the body)
(760 mm Hg – 47 mm Hg) x 0.03%
2 mm Hg (at 37ºC)
1 Adult Hemoglobin (A1) can combine reversibly with up to __
molecules of O2.
4
Hemoglobin not bound to O2 but capable of forming a bond when O2 is available.
Deoxyhemoglobin (HHb; reduced hemoglobin)
Hemoglobin bound to CO. The bond between CO and Hb is reversible but is 200 times as strong as the bond between O2 and Hb.
Carboxyhemoglobin (COHb)
Hemoglobin unable to bind O2 because iron (Fe) is in an oxidized rather than reduced state.
Methemoglobin (MetHb)
The Fe3+ can be reduced by the enzyme __________________, which is found in the red blood cells.
methemoglobin reductase
Shift to the right ODC if there’s an increased in?
body temp
hydrogen
CO2
2,3-DPG concentration
shift to the left ODC if there’s _______ in body temp, hydrogen, pCO2, and 2,3-DPG concentration.
decrease
in shift to the left ODC, if there’s an increased pCO2 is due to?
cigarette smoking
fetal hemoglobin
Anticoagulant used in sample collection for arterial blood.
0.5 mL heparin/mL of blood (lyophilized)
if there’s an excess heparin, there’s false _______ in blood pH
decrease
Liquid form of heparin would cause erroneous results because?
excessive amount can dilute or possibly contaminate the sample if equilibrated with room air.
Arterial and venous blood differ in ___, ____, and _____.
pH
pCO2
pO2
Samples should be processed immediately within?
30 minutes
Placing the blood sample in ice water quickly after the draw
reduces ________________ and ______________________.
cellular metabolism, accumulation of acidic by-products
Glycolysis could result to _______ blood pH.
decreased
Excess heparin causes ________ shift of blood pH
downward
Low temperature can cause ________ oxygen solubility in blood and make a ________ in the oxyhemoglobin curve.
increased, left-shift
used as sensing devices to measure pO2, pCO2, and pH.
Electrodes
used in measuring pO2; the amount of current flow is an indication of the oxygen present
Amperometric
used in measuring pCO2 and pH; a change in voltage indicates the activity of each analyte
Potentiometric
negative electrode
cathode
site to which cations tend to travel
cathode
a site at which reduction occurs
cathode
the gain of electrons by a particle (atom, molecule, or ion)
Reduction
positive electrode
anode
site to which anions migrate
anode
site at which oxidation occurs
anode
the loss of electrons by a particle (atom, molecule, or ion)
Oxidation
formed when two opposite electrodes are immersed in a liquid
that will conduct a current.
Electrochemical cell
measure the amount of current flow in a circuit that is related to amount of O2 being reduced at the cathode.
Clarke electrodes
A ____________ placed in the circuit between the anode cathode
measures the movement of electrons (current).
microammeter
determines blood pH by the potential difference between a
measuring electrode and a reference electrode
Sanz glass electrode
reference electrodes:
Ag-AgCl electrode
Calomel (Hg2C12)
use to measure pCO2
Severinghaus Electrode
an outer semi-permeable membrane that allows CO2 to diffuse into a layer of electrolyte, usually a bicarbonate buffer, covers the glass pH electrode.
Severinghaus Electrode
the most important factor that influences the assay
Temperature
for each degree of fever in the patient, pO2 will fall___ and pCO2
will rise ___.
7%, 3%
Lactic acidosis is the excessive accumulation of lactic acid in plasma, either due to __________, ________________ by the renal and hepatic, or _______________.
overproduction
defective removal
underutilization
It is produced from pyruvic acid by the action of LDH and NAD.
Lactic acidosis
Lactic acidosis is usually seen in cases of ___________.
tissue hypoxia
Lactic acidosis is characterized by _______________ and ___ blood pH (____).
elevated anion gap, low (<7.35)
Common cause of Lactic acidosis:
L-lactate
Reference range: venous blood lactate
5 to 20 mg/dl
Reference range: arterial blood lactate
3 to 7 mg/dL
Interpretation:
indication of sepsis
> 18 mg/dL
What is the form of L-lactate?
levorotatory
What is the form of D-lactate?
dextrorotatory
Type of lactic acidosis that is related with decreased oxygenation with tissue hypoxia.
Type A-Hypoxic Lactic Acidosis
Type of lactic acidosis that is associated with diseases and high demand of cellular oxygen, no tissue hypoxia.
Type B-Metabolic Lactic Acidosis