Acid-Base Balance pages 9-12.txt
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- What is an acid??
- Is it a proton donor or acceptor??
- A compound that contains hydrogen and reacts with water to form a hydrogen ions.
What is a base?
Is it a donor or acceptor of H??
A compound that produces hydroxide ions in water
Nearly all chemical reactions in the body depend on the maintenance of the concentration of what ion??
Changes in which ion concentration produces widespread organ dysfunction??
At 37 degrees C what is the normal H+ concentration in arterial blood ??
Hydrogen ion concentration is more commonly expressed as pH. What is the normal pH??
What is the normal HCO3?
What are the 3 main systems that regulate the amount of Hydrogen ions??
- Buffer systems
- ventilator response
- and renal response
What is the purpose of buffer systems??
to maintain a constant pH by buffering out excess hydrogen ions
What is the most important buffer system??
bicarbonate buffer system
What are the 5 components of the bicarbonate buffer system??
you are not required to write the equation but you should be able to recognize it*
CO2, H2O carbonic anhydrase, Cabronic acid (H2CO3), HCO3
In the bicarbonate buffer system, the formation of carbonic acid is catalyzed by the enzyme ___ ____.
How does the hgb buffer system work??
Erythrocytes contain hgb
CO2 difusses into erythrocytes
CO2 then combines with H20 to for carbonic acid which rapid gets rid of H that are bond to hgb
how does the ventilator response work to regulate H ions?
chemoreceptors respond within mins to changes in CO2 or pH, they work to increase or decrease ventilation to change the PaCO2.
There is an inverse relationship between PaCO2 and ____.
How do the renal response work to maintain the concentration of H ions?
Bicarbonate is reabsorbed in proximal tubules into the bloodstream forcing H to be excreted in the urine. H ions become trapped by phosphate and ammonia in the urine.
If a patient's pH is <7.35, they are ____.
If a patient's pH is >7.35, they are ____.
What is the definition of Respiratory Acidosis??
a mismatch between Co2 production and ventilator elimination
What would an ABG look like for someone with Resp. Acidosis??
decreased pH and increased PaCO2
How do the kidneys compensate for Resp. Acidosis??
they increase H+ secretion (Should this say excretion??) and HCO2 reabsorption
What are some causes of Resp. Acidosis??
it is due to either decreased Co2 elimination (hypoventilation) or increase Co2 production/reabsorption
such as airway obstruction, central nervous system depression, lung or chest wall restriction, decreased skeletal muscle strength, pulmonary disease
increase production of CO2, rebreathing of exhaled gases, CO2 absorption from pnemoperitonem
What is Resp. Alkalosis??
increased ventilation relative to Co2 production
What would an ABG look like for someone with Resp. Alkalosis??
- increase pH
- and decrease PaCO2
How would the kidneys compensate for someone in Resp. Alkalosis??
decreased bicarb reabsorption
therefore bicarb would be decreased on an ABG
How would you treat Resp. Alkalosis??
decrease the total minute ventilation (in anesthetized patient)
have patient breath into a bag so they can rebreathe Co2
what are some causes of Resp. Alkalosis??
increased CO2 elimination (hyperventilation) or decrease CO2 production
drugs, pregnancy, pain or anxiety, decrease barometric pressure, CNS injury, Arterial hypoxemia, pulmonary disease (such as PE), cirrhosis of the liver, sepsis, hyperthermia induced hyperventilation
hypothermia, hypothyroidism, skeletal muscle paralysis
pH will decrease 0.08 unit for every acute ___mmHg increase in PaCO2
The pH will return to normal if PaCO2 remains elevated...why is this??
bicarb will increase 1meq/L for every acute 10mmHg increase in PaCO2
Bicarb will increase __meq/L for every CHRONIC 10mmHg increase in PaCO2.
What is metabolic acidosis??
an accumulation of any acid in the body other than CO2
What would metabolic acidosis look like on an ABG?
decreased pH and decreased HCO3
how would the lungs compensate for metabolic acidosis??
the lungs will increase the ventilatory elimination of CO2
there will be a decreased CO2 on ABG
what is an anion gap?
it is the measured concentration difference between sodium cations and the sum of chloride and bicarb anions and represents the concentration of anions unaccounted for
What is the normal anion gap?
Metabolic acidosis can be caused by what two main reasons?
an increased anion gap (drugs, ketoacidosis, lactic acidosis, renal failure, liver failure, cirrhosis)
or a normal anion gap (administration of NS or hyperalimentation, GI bicarbonate losses, renal bicarbonate losses, drugs)
How would you treat metabolic acidosis??
- treat the underlying cause
- increase the MV to compensate
- administer sodium bicarb in the presence of extreme acidosis (ph<7.1)
What is metabolic alkalosis??
it is the gain of bicarbonate ions or loss of hydrogen ions
What would an ABG look like for someone with metabolic alkalosis??
increase pH and increased HCO3
How does the resp center compensate for metabolic alkalosis??
will see increase CO2 on ABG
What are some causes of metabolic alkalosis??
- excessive loss of H ions (vomiting, diarrhea)
- chloride and/or potassium loss (diuretics)
- excessive production of bicarbonate ions
- permissive hypercapnia
What is the purpose of a base excess or deficit??
it is the amount of acid or base that must be added for pH to return to 7.40 and PaCO2 to 40mmHg at full oxygen saturation
if the number is + indicates metabolic alkalosis
if the number is - indicates metabolic acidosis
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