ABG's Flashcards
What is carbonic anhydrase reaction
CO2 + H2O ←CA→ H2CO3 ↔ H+ + HCO3- CO2 combines with H2O and using carbonic anhydrase makes carbonic acid Carbonic acid then dissociates into H+ and bicarbonate Occurs in the Red blood cells This equation occurs in the tissues/capillaries the reverse occurs in thelungs
What happens to the charge when HCO3- leaves the red blood cell
a Cl- ion enters to balance the charge
Known as chloride shift
What is chloride shift
when a HCO3 leaves a red blood cell and a cl- enters in order to balance the charge
where does this equation occur?
CO2 + H2O ←CA→ H2CO3 ↔ H+ + HCO3-
in the tissue/capillaries
Forward in lungs,
backwards in tissues
the reverse equation occurs in the lungs
Where does this equation occur?
H+ + HCO3- ↔ H2CO3 ←CA→ H2O + CO2
In the lungs
Forward in lungs,
backwards in tissues
the reverse occurs in the tissus/capillaries
What is reverse chloride shift
the HCO3 enters the red blood cell while a cl ion leaves
describe neural reflexes in the control of breathing
as CO2 goes up, minute vetilation goes up
(linear relationship, straight line)
CO2 is powerful stimulus for ventilation
O2 is not the same, it needs to drop a really long ways to have any changes in ventilation
(to around 40mmhg)
Central and peripheral chemoreceptors detect the changes
they respond to changes in arterial blood gases
and
H+ ion concentrations
Talk about the blood brain barriers role in ventilation
The BBB is impermeable to H+ and HCO3
It is permeable to CO2
this can cause rapid changes in acid base status
The more CO2, the more ventilation
CO2 in relation to ventilation
the more CO2 the more ventilation
A 9-ycar-old boy decided to find out for how long he could continue to breathe
into and out of a paper bag. After approximately 2 minutes, his friends noticed
that he was breathing very rapidly so they forced him to stop the experbnent.
What change in arterial blood gas composition was the most potent stimulus
for this boy’s hyperventilation?
A. Dcacased Pco2 B. Decreased Po2 C. Decreased pH D. Increased Pco2 E. Increased Po2 F. lncrcaacd pH
D. Increased Pco2
A 22-year-old man was involved in a fight in which he received a severe blow
to the head. On arrival at the emergency department. he was unconscious and
initially received assisted ventilation via a manual bag-valve device. An analysis
of his arterial blood gases shows:
Po2 =45mmHg
Pco2 = 80 mm Hg
pH=7.05
HC0,-=27 mM
In what form was most col being transported in his arterial blood?
A. Bicarbonate ions
B. Carbaminohemoglobin comp
A. Bicarbonate ions
A 3-month-old infant presented with persistent vomiting and was lethargic.
Arterial blood gas analysis shomd the following results:
Pao2 = 88 mm Hg
Pacoi = 44 mm Hg
pH = 7.60
[HCO,-J = 36 mEq/L
Base excess = + 12 mEq/L
Which of the following primary acid-base disturbances is present?
A. Respiratory alkalosis
B. Respiratory acidosis
C. Metabolic alkalosis
D. Metabolic acidosill
C. Metabolic alkalosis
The results of an arterial blood gas analysis of a 56-year-old man with a history of heavy smoking are as follows: Pao2 = 60 mm Hg Paco2 = 60 mm Hg pH = 7.33 [HCO,-J = 32mEq/L Base excess = + 8 mEq/L The patient has a partially compensated
A. mpiratory alkalosis
B. respiratory acidosis
C. metabolic alkalosis
D. metabolic acidosis
B. respiratory acidosis
What is an acid
any chemical that gives up a H+
What is a base
Any chemical that accepts a H+
What happens at ph of 6.8 and below
CNS depression
coma
death
What happens at ph of 8.0 or above
excitation of the nercous system muscle tetany convulsions respiratory arresst death
what are 2 sources of acid
Respiratory Acid
CO2
H2co3
Nonvolatile acid / nonrespiratory acid
Lacric acid
ketones
What are 2 major buffering systems
Chemical buffering system
Bicarbonate (CO2) most importatn
phosphate
protein
Physiological buffering system
Respiratory CO2 excretion (quick)
Renal hydrgogen ion excretion (slow)
How do chemical buffers maintain the normal blood ph
respiratory
disposes of CO2
if we start to get acidic, we blow off CO2
Kidneys elimniates H+ ions if we start to get acidic we excrete H+ ions form bicarb put bicab bak into blood
Diet can effect ph
What do the kidneys excrete to help maintain acid base balance
acid
H+ ions
What are alpha intercalated cells for
they secrete H+ to the blood
a for acid
What are Beta intercalated cells for
they secret bicarb
b for bicarb
How do the kidneys play a general role in maintaining acid base homeostasis
the kidneys excrete excess acid
the kidneys regulate blood ph by reabsorbing filtered bicarbonate
What does NH4+ do
gets rid of H+ ions in the urine
describe ammonium ions
they get rid of H+ ions in the urine
they are formed rom glutamate
they ae secreted into the tubular urine
What are factors that can lead to increased H+ secretion by the kidney tubule epithilium
Decreased intracellular pH increased arterila blood pco2 CA activity sodium reabsorption K+ decrease increased aldosterone
What is compensation mechanism for respiratory acidosis
kidneys increase H+ excretion
What is compensation mechanism for respiratory alkalosis
kidneys increase HCO3- excretion
What is compensation mechanism for metabolic acidosis
alveolar hyperventilation
kidneys increase H+ excretion
What is compensation mechanism for metabolic alkalosis
Alveolar hypoventilation
kidneys increase HCO3- excretion
Describe things that lead to metabolic acidosis
Kidney failure, cant excrete acid excess keytones, diabetes accumulation of non respiratory acid prolonged diahrrea prolonged vomiting
Describe things that lead to metabolic alkalosis
gastric drainage
vomiting
loss of acids
What is metabolic acidosis
a condition in which the tissue and blood ph is abnormally low due to an increase in non volatile acids
In the defense of acid-base balance, which of the following processes takes the longest time for completion?
A. Buffering by bone
B. Distribution and buffering in the extracellular fluid
C. Renal excretion of acid
D. Respiratory compensation
C. Renal excretion of acid
Mixed venous blood has a lower pH than arterial blood (e.g., 7.35 vs. 7.40). The main reason for the lower pH of venous blood is its
A. higher bicarbonate concentration.
B. higher carbonic acid concentration.
C. higher oxygen content.
D. lower oxygen content.
B. higher carbonic acid concentration.
You get your final exam result back and are over the moon with how well you did. To celebrate you gorge on lots of pizza and have a few too many alcoholic beverages. That night you throw up your stomach contents. As a result, you may be in a state of:
A. Respiratory acidosis
B. Respiratory alkalosis
C. Metabolic acidosis
D. Metabolic alkalosis
D. Metabolic alkalosis
How is intracellular ph regulated
cellular ph is maintained by extruding H+ ions
must take in HCO3- at the same rate as H+ going out
Same as at systemic level
What are respiratory acidosis and alkalosis caused by
altered levels of PaCO2
things that can cause respiratory acidosis
begin to accumulate CO2
decreased rate of breathing
aiway obstruction
decreased gas exchange
things that can cause respiratory alkalosis
Decrease in acids
decrease in CO2 anxiety fever poisoning high altitude hyperventilation
decrease in H2co3
Decrease in H+
pH PCO2 HCO3-
Metabolic Acidosis ↓ ↓ ↓↓
Metabolic Alkalosis ↑ ↑ ↑↑
Respiratory Acidosis ↓ ↑↑ ↑
Respiratory Alkalosis ↑ ↓↓ ↓
pH PCO2 HCO3-
Metabolic Acidosis ↓ ↓ ↓↓
Metabolic Alkalosis ↑ ↑ ↑↑
Respiratory Acidosis ↓ ↑↑ ↑
Respiratory Alkalosis ↑ ↓↓ ↓
What is the key physiological buffer
Bicarbonate carbon dioxide system
onley works in an open system
can remove CO2 through hyperventilation
kindeys excrete H+ ions
Kidneys put bicarb back into blood
What is the bicarbonate system based on
the strong buffering capacity of the respiratory system
Does the respiratory or chemical system neutralize more acid
Respiratory system neutralizes 2-3 times as much acid as chemical buffers can
What are 3 methods of compensation
metabolic - immediate
quick acid relase
pulmonary - minutes to hours
CO2 expelled or retained
renal - hours to days
H+ increased to form acids
H+ excreted trhough ammonium
Time period for respiratory compensation to a metabolic disorder
begins within 30 mintues
complete within 12 - 24 hours
PCO2 should move in same direction as bicarb
metabolic compensation for respiratory disorders
immediate small change in HCO3
if porblem persists
much larger change in HCO3
takes 3-5 days
What is delta ratio
Change in anion gap divided by change in bicarb
less than 1 normal metabolic acidosis
1 to 1 = uncompensated metabolic acidosis
1 to 2 or over 2 = metabolic alkalosis with metabolic acidosis
what is the acid that doesnt effect anion gap
HCL
What are causes of high anion gap over 30
lactic acidosis ketoacidosis uremia toxic alcohol ingestion slicylate lactic acid acetaminophen pyroglutamic acid fromic acid oaxlic acid ethlene glycol
4 conditions that adversely effect anion gap
hypoalbuminemia
hypyerkalemia
hypermagneseia
hypercalcimeia
which acid base disorder is anion gap typically asociated with
metabolic acidosis
what is unmeasured but typically responsible for anion gap
albumin
use corrected anion gap whenalbumin is not normal
normal albumin is 4.5
