Ch. 14 Egan's
What drives the bicarbonate buffer system enormous ability to buffer acids?
ventilation continually removing CO2 from system
Based on the following ABG results, what is the most likely acid-base diagnosis? pH = 7.28, PCO2 = 53 mm Hg, HCO3- = 25.8 mEq/L
acute respiratory acidosis
Which buffer system has the greatest capacity?
bicarbonate
A patient with a measured plasma HCO3- concentration of 24 mmol/L has an episode of acute hypoventilation, with the PCO2 rising from 40 to 70 mm Hg. What do you predict will happen acutely to the plasma HC03- concentration?
HC03- will rise to approximately 27 to 28 mmol/L
What is the primary buffer system for fixed acids?
HCO3-
A patient has a pH of 7.49. How would you describe this?
alkalemia
What is the main compensatory mechanism for metabolic acidosis?
hyperventilation
What is the kidney's most important function?
sodium maintenance
Based on the following ABG results, what is the most likely acid-base diagnosis? pH = 6.89, PCO2 = 24 mm Hg, HCO3- = 4.7 mEq/L
partially compensated metabolic acidosis
Fixed acids are produced primarily from the catabolism of which of the following?
proteins
Which of the following mechanisms helps to eliminate excess H+ via the kidneys?
reabsorption of HC03-, phosphate buffering, and ammonia buffering
What is the most common cause of respiratory alkalosis?
hypoxemia
What is the primary chemical event in respiratory acidosis?
increase in blood CO2 levels
Compensation for respiratory acidosis occurs through which of the following?
increase in blood HCO3- levels
What is the primary chemical event in metabolic alkalosis?
increase in blood HCO3- levels
Acid-base balance refers to physiological mechanisms that keep the H+ ion concentration of body fluids in a range compatible with life
7.35-7.45
A patient has a bicarbonate concentration of 36 mEq and a PCO2 of 60 mm Hg. What is the approximate pH?
7.4
What is a normal anion gap range?
9 to 14 mEq/L
In acute respiratory acidosis, what would you expect the BE range to be?
+2 to -2 mEq/L
A patient has a PCO2 of 80 mm Hg. What is the concentration of dissolved CO2 (in mmol/L) in the blood?
2.4 mmol/L
According to the Henderson-Hasselbach equation, the pH of the blood will be normal as long as the ratio of HC03- to dissolved CO2 in which of the following?
20:1
Which of the following systems is primarily responsible for the buffering of fixed acids?
HCO3-
[H+] can be determined by the use of which factors?
HCO3- and H2C03
What is the treatment for severe metabolic acidosis?
NaHCO3- infusion
An ABG result shows pH of 7.35, PaCO2 of 30 mmHg, and HCO3- of 18 mEq/L. What compensatory measures has the body taken to at least partially compensate for the acid-base disorder?
blown off CO2
In regard to acid excretion by the body, which of the following statements are true?
if one system fails the other help compensate, the kidneys can only remove fixed acids, and the lungs can quickly remove acid
What is the sum of all blood buffers in 1 L of blood?
buffer base
A solution that resists large changes in pH upon addition of an acid or a base best describes which of the following?
buffer solution
How is acute respiratory acidosis accomplished?
by increasing alveolar ventilation
Based on the following ABG results, what is the most likely acid-base diagnosis? pH=7.43, PCO2=39mmHg, HCO3-=25.1 mEq/L
acid-base status within normal limits
Based on the following ABG results, what is the most likely acid-base diagnosis? pH=7.62, PCO2=41 mmHg, HCO3=40.9 mEq/L
acute (uncompensated) metabolic alkalosis
Based on the following ABG results, what is the most likely acid-base diagnosis? pH = 7.08, PCO2 = 39 mm Hg, HCO3- = 11.8 mEq/L
acute metabolic acidosis
Why is a buffer system such as phosphate considered a closed system?
all the components remain in the system
Metabolic acidosis may be caused by:
an increase in fixed (nonvolatile) acids and excessive loss of bicarbonate (HCO3-)
Which of the following are potential causes of respiratory alkalosis?
anxiety, hypoxemia, and pain
Which of the following acts as the "first-line" or immediate defense against the accumulation of H+ ions?
blood buffer system
A metabolic acidosis caused by HCO3- loss:
can be a result of ammonium chloride ingestion, may be referred to as hyperchloremic acidosis, accompanied by Cl- gain
Which of the following is a volatile acid of physiologic significance?
carbonic
Based on the following ABG results, what is most likely acid-base diagnosis? pH = 7.62, PCO2 = 32 mm Hg, HCO3- = 29 mEq/L
combined metabolic and respiratory alkalosis
Based on the following ABG results, what is the most likely acid-base diagnosis?pH = 7.01, PCO2 = 71 mm Hg, HCO3- = 16.3 mEq/L
combined respiratory and metabolic acidosis
What is a normal response of the body to a failure in one component of the acid-base regulatory mechanism?
compensation
Which of the following are signs and symptoms of acute respiratory alkalosis?
convulsions, dizziness, and paresthesia
What compensates for a metabolic alkalosis?
hypoventilation
Compensation for metabolic acidosis occurs through which of the following?
decrease in blood CO2- levels
In a patient with partially compensated respiratory alkalosis, which of the following blood gas abnormalities would you expect to encounter?
decreased HCO3-, decreased PCO2, and increased pH
In the face of uncompensated respiratory acidosis, which of the following blood gas abnormalities would you expect to encounter?
decreased pH, and increased PCO2
Which of the following is/are causes of metabolic alkalosis?
diuretics, hypochloremia, and vomiting
Which of the following clinical findings would you expect in a fully compensated respiratory acidosis?
elevated HCO3- and pH between 7.35-7.39
If the blood PCO2 is high, the kidneys will do which of the following?
excrete more H+ and reabsorb more HCO3-
Which of the following is/are true about the relationship between chloride (Cl-) and bicarbonate HCO3- in acid-base balance?
for each Cl- ion excreted into the urine, the blood gas gains an HCO3- ion, blood Cl- and HCO3- ion levels are reciprocally related, and people with chronically high CO2 tend to have low blood Cl-levels
What explains the lack of an increased anion gap seen in metabolic acidosis caused by HCO3- loss?
for each HCO3- ion lost, a Cl- ion is reabsorbed by the kidney
Based on the following ABG results, what is the most likely acid-base diagnosis? pH = 7.38, PCO2 = 21 mm Hg, HCO3- = 11.7 mEq/L
fully compensated metabolic acidosis
A patient who has fully compensated respiratory acidosis becomes severely hypoxic. If her lungs are not too severely compromised, what might her gases now appear to be?
fully compensated metabolic alkalosis
Based on the following ABG results, what is the most likely acid-base diagnosis? pH = 7.35, PCO2 = 68 mm Hg, HCO3- = 34.3 mEq/L
fully compensated respiratory acidosis
Based on the following ABG results, what is the most likely acid-base diagnosis? pH = 7.43, PCO2 = 20 mm Hg, HCO3- = 12.6 mEq/L
fully compensated respiratory alkalosis
Primary metabolic alkalosis is associated with which of the following?
gain of buffer base
What would be an example of an iatrogenic cause of metabolic alkalosis?
gastric suction
Of the non-bicarbonate buffer systems, which one is the most important?
hemoglobin
Which of the following are components of the body's non-bicarbonate buffer system?
hemoglobin, plasma proteins, organic phosphates, and inorganic phosphates
Which of the following is/are causes of hyperchloremic metabolic acidosis?
hyperalimentation and NH4Cl administration
What is the limiting factor for H+ excretion in the renal tubules?
insufficient buffers
What are the major mechanisms responsible for maintaining a stable pH despite massive CO2 production?
isohydric buffering and pulmonary ventilation
Of what use is the Henderson-Hasselbach equation for a clinician?
it allows validation of the reported values on a blood gas report
What effect does hyperventilation have on the closed buffer systems?
it causes them to release more H+
What is the role of carbonic anhydrase in the kidneys?
it drives the recovery of HCO3 and excretion of H+
A patient has a blood gas result of: pH 7.29, PaCO2 of 60 mmHg, and a HCO3- of 18 mEq/L. What is the blood gas indicating?
it is indicating a combined acidosis, patient has a primary respiratory and a primary metabolic disorder, and compensation is not possible
Why is the bicarbonate buffer system considered an open buffer system?
its acid (carbonic acid) is converted to CO2 and removed
What are some causes of metabolic acidosis with an increased anion gap?
ketoacidosis, lactic acidosis, and renal failure
Which organ system actually excreted H+ from the body?
kidneys
Which of the following organ systems assist in acid excretion?
kidneys and lungs
Which of the following accurately describes compensation for acid-base disorders?
kidneys take hours to days to compensate for respiratory disorders
What effect does hyperventilation have on HCO3- recovery in the kidneys?
less H+ excretion, greater HCO3- loss
By comparison, how much fixed acids is produced in any given period compared to the volatile acid CO2?
less fixed than volatile
What factor would limit the ability of the H2CO3/HCO3- buffer system to perform efficiently?
lungs failing to excrete adequate levels of CO2
What condition or treatment could cause iatrogenic respiratory alkalosis?
mechanical hyperventilation
An ABG result shows pH of 7.35, PaCO2 of 30 mm Hg, and HCO3- of 18 mEq/L. Which of the following is the patient's most likely primary disorder?
metabolic acidosis
In a patient with Kussmaul's respirations, what acid-base disturbance would you expect to see?
metabolic acidosis
A 31-year-old man suffering from food poisoning is having severe vomiting for the last 2 days. His blood gas and serum electrolyte analyses revealed the following: pH of 7.60, PaCO2 of 49 mm Hg, an HCO3- of 47 mEq/L, a base excess (BE) of +20 mEq/L, a serum K+ of 2.5 mEq/L, and a serum of Cl- of 92 mEq/L. How would the respiratory therapist assess his acid-base condition?
metabolic alkalosis and minimal hypoventilation
Causes of respiratory acidosis in patients with normal lungs include which of the following?
neuromuscular disorders, spinal cord trauma, anesthesia
The primary goal of acid-base homeostasis is to maintain which of the following?
normal pH
Which organ system maintains the normal level of HCO3- at 24 mEq/L?
renal
The numerator of the Henderson-Hasselbach (H-H) equation (HCO3-) related to which of the following?
renal buffering and excretion of fixed acids
Compensation for respiratory alkalosis occurs through which of the following?
renal excretion of HCO3-
An increase in the H+ ion concentration [H+] of the blood due only to an increase in the arterial PCO2 (hypercapnia) best describes which of the following?
respiratory acidosis
A decrease in the H+ ion concentration (H+) of the blood caused by a low PaCO2 best describes which of the following?
respiratory alkalosis
An ABG result shows the pH to be 7.56 and the HCO3- to be 23 mEq/L. Which of the following is the most likely disorder?
respiratory alkalosis
Correction of metabolic alkalosis may involve which of the following?
restoring normal fluid volume, administering acidifying agents, and restoring normal K+ and Cl- levels
A 21 year old woman in the emergency room is displaying rapid and deep, labored breathing. Her room ABG reveals a pH of 7.25, PaCO2 of 28, HCO3- of 14 mEq/L, and a base excess of -14 mEQ/L. How would the respiratory therapist assess her acid-base condition?
severe hyperventilation, partially compensated and metabolic acidosis, and compensatory response to the metabolic acidosis
Normally which of the following occur when the kidneys eliminate H+?
sodium ions (and water) are reabsorbed, HCO3- is reabsorbed in proportion to the H+ excreted, and bicarbonate buffer capacity is restored
In order to eliminate the influence of PCO2 changes on plasma HCO3- concentrations, what additional measures of the metabolic component of acid-base balance can be used?
standard bicarbonate
When does a state of alkalemia exist?
the HCO3-/CO2 ratio exceeds 20:1 and the blood pH exceeds 7.45
According to the Henderson-Hassebach equation, the blood pH will rise (alkalemia) under which of the following conditions?
the buffer capacity increases and the volatile acid (CO2) decreases
Which of the following statements about the equilibrium constant of an acid is true?
the equilibrium constant of a weak acid is small
A patient has an anion gap of 21 mEq/L. Based on this information, what can you conclude?
there is an abnormal excess of unmeasured anions in this plasma and the patient probably has metabolic acidosis
The majority of the acid the body produces in a day is excreted through the lungs as CO2. What happens to the H+ ions?
they bind to an OH-forming H2O
Using the Henderson-Hasselbalch equation, determine the accuracy of the gas below. To be considered accurate, it must be within 0.03 pH unit. pH = 7.22, PCO2 = 49 mm Hg, HCO3- = 20 mEq/L
this gas is accurate as the calculated pH is 7.23
Using the Henderson-Hasselbach equation, determine the accuracy of the gas below. To be considered accurate, it must be within 0.03 pH unit.pH = 7.35, PCO2 = 77 mm Hg, HCO3- = 41 mEq/L
this gas is completely accurate
When a strong acid is added to the bicarbonate buffer system, what is the result?
weak acid and neutral salt
Approximately how much CO2 is removed daily by the lungs?
~24,000 mmol/L of CO2
What is the normal range for BE?
±2 mEq/L
