Chap 7 Flashcards
Normal arterial pH range is 7.35 to 7.45
Venous pH range is 7.30 to 7.40
alkalosis
ph greater than 7.45, blood has an excess amount of bicarbonate ions
acidosis
ph below 7.35, blood has an excess amount of hydrogen ions
Hydrogen ions originate from
- the breakdown of phosphorous containing proteins 2. the anaerobic metabolism of glucose 3. the metabolism of body fats 4. the transport of CO2 in the blood as HCO liberates H ions
ph regulated by the following what major systems
the chemical buffer system, the respiratory system, and the renal system
chemical buffer system
responds within a fraction of a second to resist pH changes and is called the first line of defense.
Chemical buffer composed of
- the carbonic acid-bicarbonate buffer system 2. the phosphate buffer system 3. the protein buffer system….the chemical buffer system inactivates hydrogen ions and liberates HCO ions in response to acidosis or generates more H ions and decreases the concentration of HCO ions in response to alkalosis
respiratory system acts within
1 to 3 minutes by increasing or decreasing the breathing depth and rate to offset acidosis or alkalosis, respectively.
in response to metabolic acidosis, the resp system causes
the depth and rate of breathing to increase, causing the bodys CO2 to decrease and the pH to increase.
in response to metabolic alkalosis, the respiratory system causes
the depth and rate of breathing to decrease, causing the bodys CO2 to increase and the pH to decrease.
bodys most effective acid-base balance monitor and regulator
Renal system
Renal system requires how long to correct abnormal pH concentrations
a day or more
when the extracellular fluids become acidic the renal system
retains HCO and excretes H ions into the urine causing th pH to increase
when the extracellular fluids become alkaline the renal system
the renal system retains H and excretes basic substances (HCO) into the urine causing the pH to decrease
Acids and bases
are electrolytes. thus, both are acids and bases can ionize and dissociate in water and conduct an electrical current
acids taste
sour
acids can react
with many metals, and can “burn” a hole through clothing.
Acids release
hydrogen ions in measurable amounts, defining acids as proton donors
Proton donors
when acids dissolve in a water solution, they release hydrogen ions (protons_ and anions
The acidity of a solution is directly related to
the concentration of protons. in other words, the acidity of a solution reflects only the free hydrogen ions, not those bound to anions
hydrochloric acid (HCI)
the acid found in the stomach that works to aid digestion
HCL-> H+ Cl-
hydrochloric acid
strong acids
which dissociate completely and irreversibly in water, dramatically change the pH of the solution.
Weak acids
do not dissociate completely in a solution and therefore have a much smaller effect on pH. However, even though they have a relatively small effect on changing pH levels, they have a very important role in resisting sudden pH changes
Examples of weak acids
carbonic acid and acetic acid
Proton acceptors
bases
bases taste/ feel
taste bitter and feel slippery
base is a substance that
takes up hydrogen ions in measurable amounts
Bicarbonate ion
is an important base in the body and is especially abundant in the blood
ammonia
a natural waste product of protein breakdown, is also a base. Has a pair of unshared electrons that strongly attract protons
Strong bases (hydroxides)
dissociates easily in water and quickly tie up H+
Weak bases (sodium bicarbonate or baking soda)
dissociate incompletely and reversibly and are slower to accept protons. since sodium bicarbonate accepts a relatively small amount of protons, its released bicarbonate ion is described as a weak base
as the concentration of H in a solution increases, the solution becomes
more acidic
as the level of hydroxide ions increase, the solution becomes more
basic, or alkaline
pH units
the concentration of hydrogen ions in the body measurement
pH scale
runs from 0-14 and is logarithmic, which means each successive unit change in pH represents a tenfold change in H ion concentration.
buffer action
the ability of an acid-base mixture to resist sudden changes in pH. Works against sudden and large changes in the pH of body fluids by releasing H ions
three major chemical buffer systems
carbonic acid-bicarbonate buffer system, phosphate buffer system, and the protein buffer system
Carbonic acid-bicarbonate buffer system
plays an extremely important role in maintaining pH homeostasis of the blood
under normal conditions, what is the ratio between HCO and H2CO in the blood
20:1
Henderson-Hasselbalch Equation
illustrates how the pH of a solution is influenced by the HCO to H2CO ratio (base to acid ratio)
Under normal conditions the 20:1 acid-base balance in the body is automatically regulated by the
chemical buffer systems, the respiratory system, and the renal system. however, these normal acid-base regulating systems have their limits
Common acid-base disturbance classifications
Respiratory Acid-Base Disturbance, Metabolic Acid-Base Disturbance
Acute Ventilatory falure
acute hypoventilation caused by an overdose of narcotics or barbiturates
common causes of Respiratory Acidosis/ acute ventilatory failure
Chronic obstructive pulmonary disorders, drug overdose, general anesthesia, head trauma, nerologic disorders
Acute ventilatory failure/ Respiratory Acidosis
also called acute respiratory acidosis is a medical emergency, needs immediate ventilatory assistance
In the pt who hypoventilates for a long period of time (chronic obstructive pulm disease)
the kidneys will work to correct the decreased pH by retaining HCO in the blood
Common causes of Respiratory Alkalosis/ acute alveolar hyperventilation
hypoxia, pain, anxiety, and fever, brain inflammation, stimulant drugs
Common causes of Metabolic Acidosis
lactic acidosis (fixed acids), Ketoacidosis (fixed acids), renal failure, Uncontrolled diarrhea
Metabolic acidosis is caused by either the loss of
HCO or the accumulation of fixed acids or metabolic acids are produced from sources other than carbon dioxide
Anaerobic Metabolism
an alternative biochemical reaction occurs that does not use oxygen . lactic is the by product of this process
Common causes of metabolic alkalosis
Hypokalemia, hypochoremia, gastric suction or vomiting, excessive administration of coricosteroids, excessive administration of sodium bicarbonate, diuretic therapy, hypovelemia
During acute alveolar hypoventilation, the blood 1.HCO increases 2.pH increases 3.HCO3 increases 4.PCO2 increases
1,2, and 3
the bulk of the CO2 produced in the cells is transported to the lungs as
HCO3
During acute alveolar hyperventilation, the blood
H2CO3 decreases
in chronic hypoventilation, renal compensation has likely occured when the
HCO3 is higher than expected for a particular PCO2, pH is higher than expected for a particular PCO2
when metabolic acidosis is present, the patients blood
pH is lower than expected for a particular PCO2 and HCO3 is lower than expected for a particular PCO2
Ketoacidosis can develop from
an inadequate serum insulin level, an inadequate serum glucose level
metabolic alkalosis can develop from
hypokalemia, hypochoremia
which of the following HCO3 to H2CO3 ratios represents an acidic pH? 1.) 18:1 2.) 28:1 3.) 12:1 4.) 22:1
1 and 3 only
if a patient has a level of 70 torr what is the H2CO3 concentration
1.7 mEq/L
The value of the pK in the Henderson-Hasselbalch equation is
6.1
Metabolic acidosis caused by a decreased HCO3 is often called
Hyperchloremic Metabolic Acidosis
Metabolic Acidosis caused by fixed acids is present when the anion gap is greater than
14 mEq/L
PaO2 levels
80-100 normal, 60-80 mild hypoxia, 40-60 moderate hypoxia, >40 severe hypoxia
Causes of respiratory alkalosis
Hyperventilation or anxiety and trauma or pain
PaCO2 levels
35-45, fast to compromise by blowing of CO2
HCO3
22-28 never compromises right away
strong bases
dissociate easily in H20 and quickly tie up H
Weak Bases
dissociate incompletely and reversibly and are slower to accept protons
proton acceptors
bases
weak acids examples
Carbonic acid (H2CO3) and acetic acid
RBC value
4.7-6.1 million
Hematocrit value
42-52%
HCO2 values
arterieal 22-28mEq/L, Venous 24-30mEq/L
Hgb values
12-16 g/100mL
Carbon Dioxide Transport
metabolizing tissue cells consume approximately 250 ml/min of oxygen and produce approx 200ml/min of CO2 at rest
Plasma Transport
Carbamino Compound (bound to protein)= 1%, Bicarbonate= 5%, Dissolved CO2= 5%
Hydrolysis
CO2 + H2O
Plasma Transport CO2 + H2O -> H2CO3->
H+ + HCO3 (reverse formula when blood reaches the alveoli)
Dissolved CO2 can be measured in
the venous blood to report the PvCO2
H2CO3 concentration can be determined by
multiplying the PCO2 x 0.003
RBC Transport %
Dissolved CO2= 5%, Carbamino-Hgb= 21%, bicarbonate= 63%
Haldane effect
decreased SaO2 promotes loading of CO2 and increased loading of O2 promotes CO2 release
Carbonic Anhydrase (CA)
acts as the catalyst to speed the reaction up, biggest carrier of CO2
RBC transport CO2 + H2O -> CA-> H2CO3 ->
H+ + HCO3
Concentration Equilibrium achieved by
HCO3 excess diffusing out of the RBC into the plasma
Plasma HCO3 combines with NaCL to form
NaCO3
Choride shift HCO3 + NaCL ->
NaHCO3 + free Cl-
CO2 Elimination at the lungs
all the chemical reactions at the tissue level reverse and unload the CO2 until the PCO2 is equal
Electrolytes
electrically charged ions (Na+, K+, Ca++, Mg++, Cl-)
Buffers
neutralize both acids and bases
two most important in buffer system
Carbonic acid (H2CO3) and sodium bicarbonate (NaHCO3)
Normal HCO3 to H2CO3 ratio is
20:1
A HCO3 of 24 mEq/L would have a H2Co3 of
1.2mEq/L
PaCO2-pH relationship
based on a norm PaCO2 of 40 mmHg (1.) for every 20mmHg increase (above 40), in the PaCO2, the pH will decrease by 0.10 (2.) for every 10mmHg decrease, in the PaCO2, the pH will increase by 0.10
PaCO2-HCO3 relationship
(1.) an acute PaCO2 increase of 10mmHg will increase the HCO3 by 1 mmol/L (2.) an acute PaCO2 decrease of 10mmHg will decrease the HCO3 by 2mmol/L
Shift in CO2 will affect pH IF
bicarbonate stays the same
Percent carried by RBC
98%
Predicting Respiratory pH ex. 76.. greater than 40
76-40=36 x 1/2 = 18 or .18, 7.40-.18= 7.22
Predicting Respiratory pH ex. 18… less than 40
40-18= 22 or .22, 7.40+ .22 = 7.62
Respiratory Acidosis=
Acute/ Chronic hypoventilation
Respiratory alkolosis
hyperventilation
