Chap 9-Acids&Bases Flashcards
pH =
pH is the
potential hydrogen
concentration of hydrogen ions (H+)
The pH of blood indicates the net_______
result of normal acid-base regulation, any acid-base imbalance, and the body’s compensatory mechanisms
Human blood must maintain a_________ pH range
Blood =
very narrow; 7.35 – 7.45
less than _____or greater than ____death occurs
< 6.8 or > 8.0
One Proton (+) One Electron (-)
electrically balanced
An Acid is…
A molecule that can donate a H+ ion
An acid can be weak, moderate, or strong depending on its ________
Weaker acids are closer______
Stronger acids are closer to_____
pH
to 7
to 1
A Base or alkali is…
A molecule that can accept a H+ ion
A base can be weak, moderate, or strong depending on its pH
Weaker bases are closer to pH __
Stronger bases are closer to pH ____
pH
7
14
Bronsted Theory
An acid is _______
A base is_______
When an acid donates it proton, what remains is called what?
Defines an acid as a proton, or H+ ion donor.
A base is a proton acceptor.
When an acid donates its proton, what remains is called
the conjugate base.
When a base accepts a proton, it is converted into its
Ex:
conjugate acid.
NH3 + H+ = NH4+ (ammonia to ammonium)
HCO3- + H+ = H2CO3 (bicarb to carbonic acid)
pH Range is from________
If [H+] is high, the solution is________; pH < 7
↑ H+ ↓ pH (Acidic)
If [H+] is low, the solution is basic or alkaline ; pH > 7
↓ H+ ↑ pH (Alkaline)
Acids are H+ donors.
Bases are H+ acceptors, or give up OH- in solution.
0 - 14; acidic
not important Acids and bases can be: Strong –\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ ex: Weak –\_\_\_\_\_\_\_\_\_\_\_ ex:
dissociate completely in solution
HCl, NaOH
dissociate only partially in solution
Lactic acid, carbonic acid
pH scale = 1 to 14
The p-function operator means the negative logarithm of.
pH = -log [H+]
In this case, a range of 100 to
10-14 onto a range of 1 to 14.
Calculate [H+] for pH of 7.4?
0.00004mEq , 40nEq/L
Calculate nano equivalents shortcut
[H+] = 10 (9-pH)
Example: Calculate pH of a solution when the [H+] is 1.0 x
10^-3 M
pH= 3.00
ABG Analysis indicates
how well a patient is exchanging gases in the lungs and how well the body is maintaining normal pH.
pH_______
PaCO2_______
HCO3- _______
PaO2 ________
7.35 – 7.45
35 – 45 mmHg
22 – 26 mEq/L
80 – 100 mmHg
ABG Interpretation Step 1: Step 2: Step 3: Step 4:
- check PaO2 (80-100)
< 80 = hypoxic, > 100 = hyper-oxygenated (mask, ventilation, etc) - check pH (7.4)
7.35 – 7.45 = compensated acidosis or alkalosis
< 7.35 = uncompensated acidosis, > 7.45 = uncompensated alkalosis
3.check PaCO2 (35-45) alkalotic or acidotic range?
Correlate with pH – if both pH & CO2 match, cause = respiratory
- check HCO3 (22-26) acidotic or alkalotic range?
Correlate with pH – if both pH & HCO3 match, cause = metabolic
If all 3 (pH, CO2 & HCO3) match, cause = “combined”
what is the cut off for compensated vs uncompensated
pH ph 7.35 - 7.40 compensated acidosis
ph 7.40-7.45 compensated alkalosis
PaO2: 90
pH: 7.52
PaCO2: 43
HCO3: 30
uncompensated metabolic alkalosis
PaO2: 90
pH: 7.52
PaCO2: 29
HCO3: 30
“Combined Alkalosis Combined Alkalosis” because ” because both CO2 and HCO3 are CO2 and HCO3 are
contributing to the pH alkalosis
Compensated – pH in range w/ both #s off
Uncompensated –
Partially Compensated -
Combined –
pH out of range w/ one off & one normal
pH out of range w/ both #s off
pH out of range w/ both #s contributing
Buffer systems
Prevent major changes in pH by removing or releasing
hydrogen (H+) ions
Act chemically to change strong acids into weaker acids or to bind acids to neutralize their effects
Carbonic acid (H2CO3) –
Bicarbonate buffer system –
most important ECF buffer against non-carbonic acid
changes
Carbonic acid (H2CO3) –
Protein buffer system (includes Hgb) –
LARGEST buffer in the body; important ICF and ECF buffer
Protein buffer system (includes Hgb) –
LARGEST buffer in the body; important ICF and ECF buffer
Hemoglobin buffer system –primary buffer against carbonic acid changes (via arbaminohemoglobin)
List 3 buffers mechanisms
Bicarbonate buffer syterm
Protein Buffer system
PHOSPHATE Buffer system
Phosphate buffer system –
important intracellular and urinary buffer
Note about buffer
Buffer systems do not eliminate H+ from or add them to the body but only keep them tied up until balance can be reestablished by compensatory mechanisms
Kassirer-Bleich equation:
[H+] = 24 x PCO2/HCO3 ¯ (allows calculation of [H+] and
pH if PCO2 and HCO3 are known)
What does the Kassirer-Bleich equation do
Reflects how the acidity of blood is determined by the relative availability of acid and alkali (HCO3¯ & PaCO2)
Stresses how H+ ion concentration is determined by the ratio of PCO2/HCO3, rather than the absolute value of either value alone.
Metabolic Acidosis/Alkalosis =
Respiratory Acidosis/Alkalosis =
disturbances of bicarbonate
disturbances of PaCO2
A normal [H+] of 40 nEq/L corresponds to a pH of 7.40.
Because the pH is a negative logarithm of the [H+], changes in pH are inversely related changes in [H
+] (e.g., a decrease in pH is associated with an
increase in [H+]).
When a primary acid-base disturbance alters one
component of the PCO2/[HCO3- ] ratio,
the compensatory response alters the other component in the same directionto keep the PCO2/[HCO3- ] ratio constant.
Respiratory acidosis PCO2_____HCO3 _______
Respiratory alkalosis PCO2 ______ HCO3 _______
Metabolic acidosis HCO3 _____PCO2 ______
Metabolic alkalosis HCO3_____ PCO2_______
up ; up
down; down
down; Down
up; up
For acute respiratory disturbances (where renal
compensation does not have much time to occur)
each arterial PCO2 _________________while for chronic respiratory disturbances (where renal compensation
has time to occur) each PCO2 shift of
shift of 10 mm Hg is accompanied by a pH shift of about 0.1,
10 mm Hg is accompanied by a pH shift of about 0.03.
In our case an arterial PCO2 shift of 25 mm Hg (from 40 to 65 mm Hg) is accompanied by a pH shift of 0.10 units (from 7.40 to 7.30), or a 0.04 pH shift for each PCO2 shift of 10 mm.
Since 0.04 is reasonably close to the expected value of 0.03 for an chronic respiratory disturbance, it is reasonable to say that clinically the patient has chronic respiratory acidosis.
