Normal Arterial pH
7.35-7.45
pH greater than 7.45 indicates
Alkalosis. Excess HCO3.
pH below 7.35 indicates
Acidosis. Excess H+ ions.
Venous pH range
7.30-7.40
Most H+ ions in the body originate from
-Breakdown of phosphorous-containing proteins (phosphoric acid)
-anaerobic metabolism of glucose (lactic acid)
-metabolism of body fats (fatty and ketone acids)
-transport of CO2 in the blood as HCO3 liberates H+ ions.
Under normal conditions, H+ and HCO3 ion concentrations in the blood are regulated by:
Chemical buffer system, respiratory system, renal system.
Chemical Buffer System
1st line of defense. responds within a fraction of a second. Inactivates H+ ions and liberates HCO3 ions in response to acidosis, or generates more H+ ions and decreases HCO3 concentration in response to alkalosis.
The chemical buffer system is composed of
-Carbonic acid-bicarbonate vuffer system
-Phosphate buffer system
-Protein buffer system
Respiratory System
Acts within 1-3 minutes by increasing/decreasing rate and depth of breathing to offset acidosis or alkalosis, respectively.
Respiratory System response to metabolic Acidosis
increases the rate and depth of breathing, causing the CO2 to decrease and pH to increase.
Respiratory System response to metabolic alkalosis
Decreases rate and depth of breathing, increasing the CO2 and decreasing pH.
Renal System
Body's most effective acid-base balance monitor and regulator. Requires a day or more to correct pH.
Renal System response when extracellular fluids are acidic
Retains HCO3 and excretes H+ ions into urine, causing the blood pH to increase.
Renal System response when extracellular fluids are alkaline
Retains H+ and excretes basic substances (primarily HCO3) into the urine, causing the blood pH to decrease.
Acids release _____
H+ ions in measurable amounts.
Acids are defined as ____.
Proton donors. When they dissolve in water, they release H+ (protons) and anions.
The acidity of a solution is directly related to___
the concentration of H+ ions (protons).
The acidity of a solution reflects only the ______ hydrogen ions, not the ____ hydrogen ions.
Reflects only the free H+ ions, not those bound to anions.
Examples of acids in the body
HCl (hydrochloric acid), HC2H3O2 (acetic acid, often abbreviated as HAc), and H2CO3 (carbonic acid). The molecular formula for common acids is easy to identify because it begins with the hydrogen ion.
Strong acids
Dissociate completely in water and liberates all H+ ions. Has a great effect on pH. Are irreversible.
Weak acids
Do not dissociate completely in a solution. Small pH effect. Important role in resisting sudden pH changes.
Examples of weak acids
H2CO3 (carbonic acid) and HC2H3O2 (acetic acid).
Bases ____ H+ ions in measurable amounts.
take up. When dissolved in water, they dissociate into hydroxide (OH-) ions and cations. Liberated OH- ions then bond to the H+ ions present in the solution. This produces water and decreases the acidity of a solution.
Common inorganic bases
include the hydroxides, such as: magnesium hydroxide (milk of magnesia) and sodium hydroxide (lye). HCO3 (bicarbonate), NH3 (ammonia, which is a waste of protein breakdown).
Strong Bases
quickly dissociate and take up H+. EX, hydroxides.
Weak Bases
Dissociate incompletely and reversibly, and are slower to accept protons. Ex, sodium bicarbonate and baking soda.
As the H+ ion concentration of a solution increases, the solution becomes ______.
More acidic.
If the level of hydroxide ions increases in a solution, it becomes ____.
More basic, or alkaline.
Each unit change in pH represents
a tenfold change in H+ concentration.
When the pH is 7
it is neutral. the number of H+ ions equals the OH- ions. Pure water.
When the pH is below 7
it is acidic. There are more H+ ions than OH- ions.
When the pH is greater than 7
it is alkaline. OH- ions outnumber the H+ ions.
The ability of an acid-base mixture to resist sudden changes in pH is called _____.
its buffer action.
Buffers work against sudden and large pH changes by _____.
releasing H+ ions (acting as acids) when the pH increases and binding OH- ions (acting as bases) when the pH decreases.
Carbonic acid-bicarbonate buffer system
Carbonic acid dissociates reversibly and releases HCO3 and protons.
Under normal conditions, the ratio between HCO3 and H2CO3 (carbonic acid) in the body is
20:1
Henderson-Hasselbach equation
Mathematically illustrates how pH of solution is influenced by HCO3- to H2CO3 ratio (base to acid ratio).
Phosphate buffer system
function is almost identical to carbonic acid-bicarbonate buffer system. Primary components are sodium salts of dihydrogen phosphate (H2PO4) and monohydrogen phosphate (HPO4). When H+ ions are released by a strong acid, the phosphate BS works to inactivat
The phosphate buffer system is ___ as effective as the carbonic acid buffer system.
1/6th. It is not effective in plasma. It is effective in urine and intracellular fluid where there are greater phosphate levels.
Protein buffer system.
most abundant and influential. Its buffers are found in the proteins in the plasma and cells. 75% of buffering power. Organic acid groups (-COOH) dissociate and liberate H+ in response to rising pH. Other amino acids consist of exposed groups that can fun
Amphoteric Molecules
protein molecules with a reversible ability.
Respiratory System has ____ the buffering power of all the chemical systems combined.
up to 2x.
The respiratory system eliminates CO2 from the body and replenishes it with O2. The CO2 produced at the tissue cells enters the RBCs and is converted to _____
HCO3 ions. Bicarbonate ions, which are a base.
Severe head trauma can cause
An increase in rate and depth of breathing that is unrelated to CO2 concentration. The volume of CO2 expelled from the lungs is greater than the CO2 produced at the cells. Hyperventilation is present. This will cause the pH to increase and respiratory alk
The ingestion of barbiturates can cause
A decrease in the rate and depth of breathing. CO2 eliminated from the lungs is less than the amount produced at tissue cells. This causes the pH to fall and respiratory acidosis is said to exist.
Only the _____ system can rid the body of acids such as phosphoric acids, uric acids, lactic acids, and ketone acids (fixed acids).
Renal system
only the ____ system can regulate alkaline substances in the blood and restore chemical buffers that are used up in managing the H+ levels in extracellular fluids.
Renal
Two main acid-base disturbance classifications
Respiratory Acid-base disturbances and Metabolic Acid-Base disturbances.
Respiratory Acid-Base Disturbances
Acute ventilatory failure (respiratory Acidosis)
Acute ventilatory failure with partial renal compensation
Chronic ventilatory failure with complete renal compensation.
Acute Alveolar hyperventilation (respiratory Alkalosis)
Acute alveolar hyperventilatio
Metabolic Acid-Base disturbances
Metabolic acidosis
Metabolic acidosis with partial respiratory compen.
Metabolic acidosis with complete respiratory comp.
Combined metabolic and respiratory acidosis.
Metabolic alkalosis
Metabolic alkalosis with partial resp. comp.
Metabolic alkalosis wit
For a pH of 7.40, you would expect the PCO2 and the HCO3 to be approximately
PCO2 40 torr, HCO3 24 torr.
Define acute ventilatory failure
acute hypoventilation caused by an overdose of narcotics or barbiturates. PACO2 will progressively increase, so the blood PCO2, H2CO3, and HCO3 leels increase. AKA acute respiratory acidosis.
Acute changes in ____ levels are more significant than acute changes in ___ levels.
H2CO3 more significant than HCO3.
Common causes of acute ventilatory failure
COPDs- Chronic emphysema and chronic bronchitis.
Drug overdose
General Anesthesia
Head trauma
Neurologic Disorders- Guillan Barre and myasthenia gravis
Acute Ventilatory failure with partial renal compensation
(AKA partially compensated respiratory acidosis).
In the patient who hypoventilates for a long period of time, the ____ will work to correct the decreased pH by retaining HCO3- in the blood.
Kidneys. This can be seen in COPD pts.
What causes chronic ventilatory failure with complete renal compensation?
Present when the HCO3- increases enough to cause the acidic pH to move back into the normal range
Above 42 mEq/L
Acute alveolar hyperventilation
AKA respiratory alkalosis. Ex, hyperventilation due to pain/anxiety. PACO2 will decrease and more CO2 molecules will leave the pulmonary blood. This causes a decrease in blood PCO2, Bicarb, and carbonic acid levels. The pH increases and becomes more alkal
Common causes of acute alveolar hyperventilation (respiratory alkalosis)
-Hypoxia-Any cause of hypoxia (e.g., lung disorders, high altitudes, and heart disease) can cause acute alveolar hyperventilation.
-Pain, anxiety, and fever -Relative to the degree of pain, anxiety, and fever, hyperventilation may be seen.
-Brain inflamma
In the patient who hyperventilates for a long period of time, the ____ will work to correct the increased pH by excreting excess HCO3- in the urine.
Kidneys
Chronic alveolar hyperventilation with complete renal compensation is present when ____.
the HCO3- level decreases enough to return the alkalotic pH to normal, Which, in this, case would be below 14 mEq/L
If the patient's blood pH becomes acidic for a long period of time due to hypoventilation, the kidneys _____.
will not retain enough HCO3- for the pH to climb higher than 7.40. Exception, COPD/chronic bronchitis pts
Should the blood pH become alkalotic for a long period of time due to hyperventilation, the kidneys ____.
will not excrete enough HCO3- for the pH to fall below 7.40.
Metabolic acidosis
The presence of other acids, not related to an increased PCO2 level, that can be identified on the nomogram. Too much acid in the body fluids.
Anion gap
used to determine if pt's metabolic acidosis is caused by the accumulation of fixed acids (lactic acids, ketoacids, or salicylate intoxication), or by an excessive loss of HCO3. The calculated difference between the Na+ ions and the sum of the HCO3 and CL
Normal anion gap range
9-14 mEq/L.
An anion gap greater than 14 mEq/L represents
metabolic acidosis. (caused by buildup of fixed acids)
Common Causes of metabolic acidosis
- Lactic acidosis, keto acidosis, salicylate intoxication (fixed acids)
-Renal Failure: Causes the HCO3 concen to decrease and the H+ concen to increase.
-Uncontrolled diarrhea: loss of HCO3 and increase in H+.
Or, when a metabolic acidosis is seen with a normal anion gap, the most likely cause of the acidosis is ______.
an excessive lose of HCO3- Caused by renal disease or severe diarrhea
The immediate compensatory response to metabolic acidosis is _____.
an increased ventilatory rate. This action causes the PaCO2 to decline. As the PCO2 decreases, the H+ concentration decreases. This action works to offset the metabolic acidosis
Metabolic acidosis with complete respiratory compensation is present when ____.
the PaCO2 decreases enough to move the acidic pH back to the normal range
Combined Metabolic and Respiratory Acidosis
commonly seen in patients with acute ventilatory failure
Causes blood PCO2 to increase (respiratory acidosis), and PO2 to decrease (metabolic acidosis�caused by lactic acids)
Metabolic Alkalosis
Presence of other bases, not related to a decreased PCO2 level or renal activity, can also be identified on the nomogram. pH and HCO3- readings are both higher than expected for a normal PCO2 level.
Causes of metabolic alkalosis
-Hypokalemia: kidneys attempt to conserve potassium by excreting hydrogen ions. This causes blood base to increase.
-Hypochloremia: When Cl decreases, HCO3 increases in an attempt to maintain normal cation balance.
-Gastric suctioning or vomiting: causes
Normal Sodium level
140 mEq/L
Normal Chloride level
105 mEq/L
Normal HCO3 level
24 mEq/L
When acute hypoxemia is present, the presence of _____ should be suspected.
Lactic Acid
The immediate compensatory response to metabolic alkalosis is
A decreased ventilatory rate. This causes the PaCO2 to rise. As it rises, the H+ concentration increases and works to offset the metabolic alkalosis.
Metabolic alkalosis with complete respiratory compensation is present when
the PaCO2 increases enough to move the alkalotic pH back to the normal range
By knowing the base excess/deficit _____.
non-respiratory acid-base imbalances can be quantified. It is reported in mEq/L of base above or below the normal buffer base line of the nomogram.
Combined metabolic and respiratory alkalosis can develop when
an acute decrease in PaCO2 is accompanied by any condition that causes metabolic alkalosis.