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Frequently asked questions – Acid base balance and imbalance
Q.1- Explain clearly how hyperventilation and hypoventilation affect blood p H ? Give suitable examples in support of your answer.
Q.2- Explain the role of hemoglobin as a buffer in the maintenance of acid-base balance in the body.
Q.3-The maintenance of intracellular pH within narrow limits is essential for life processes. Briefly discuss why this is so and describe the mechanism by which the human body maintains a relatively constant pH despite continuous acid production from cellular metabolism.
Q.4- Name 3 physiological buffer systems, and explain the mode of action of any one of them.
Q.5-A person was brought to the hospital after ingesting a large amount of ammonium chloride. His arterial blood pH was found to be 7.29. Calculate the ratio of [HC03] to [dissolved CO2] in the blood.
Dissolved CO2 + H20 « H2CO3 « H+ + HCO3– (pKa = 6.1) How might changes in the pulmonary ventilation help to minimize the fall in pH?
Q.6- Discuss the role of kidneys in the maintenance of the acid-base balance of the body. Support your answer with flow charts showing the details of the mechanisms.
Q.7- What is the anion gap? State all the conditions of variations of anion gap in the body?
Q.8- Calculate the anion gap for a patient who has reported to the emergency in a state of shock with following blood reports
p H- 7.2
PCO2- 45 mm Hg
HCO3—12 meq/L
Serum Na- + 135 meq/L
Cl – -85 meq/L
Q.9- A 14-year-old girl with cystic fibrosis has complained of an increased cough productive of green sputum over the last week. She also complained of being increasingly short of breath, and she is noticeably wheezing on physical examination. Arterial blood was drawn and sampled, revealing the following values:
| pH | 7.30 |
| pCO2 | 50 mm Hg |
| pO2 | 55 mm Hg |
| Hemoglobin – O2 saturation | 45 % |
| [HCO3-] | 24 meq/liter |
What is the acid-base status of the girl? Discuss in detail about the imbalance
How would the kidneys try to compensate for the girl’s acid-base imbalance?
Q.10- A 76-year-old man complained to his wife of severe substernal chest pain that radiated down the inside of his left arm. Shortly afterward, he collapsed on the living room floor. Paramedics arriving at his house just minutes later found him unresponsive, not breathing, and without a pulse. CPR and electroconvulsive shock were required to start his heart beating again. Upon arrival at the Emergency Room, the man started to regain consciousness, complaining of severe shortness of breath (dyspnea) and continued chest pain. On physical examination, his vital signs were as follows:
| Systemic blood pressure | 85 mm Hg / 50 mm Hg |
| Heart rate | 175 beats/minute |
| Respiratory rate | 32 breaths/ minute |
| Temperature | 99.2oF |
His breathing was labored, his pulses were rapid and weak everywhere, and his skin was cold and clammy. An ECG was done, revealing significant “Q” waves in most of the leads. Blood testing revealed markedly elevated creatine phosphokinase (CPK) levels of cardiac muscle origin. Arterial blood was sampled and revealed the following:
| pH | 7.22 |
| pCO2 | 30 mm Hg |
| pO2 | 70 mm Hg |
| Hemoglobin – O2 saturation | 88 % |
| [HCO3-] | 2 meq/ liter |
a) What is the diagnosis? What evidence supports your diagnosis?
b) How would you classify his acid-base status? What specifically caused this acid-base disturbance?
c) How has his body started to compensate for this acid-base disturbance?
d) What would his blood pH be if his body had not started compensating for the acid-base disturbance? Show your work.
e) List some other causes of this type of acid-base disturbance.
Q.11- An elderly gentleman is in a coma after suffering a severe stroke. He is in the intensive care unit and has been placed on a ventilator. Arterial blood gas measurements from the patient reveal the following:
| pH | 7.50 |
| pCO2 | 30 mm Hg |
| pO2 | 100 mm Hg |
| Hemoglobin – O2 saturation | 98% |
| [HCO3-] | 24 meq/liter |
a) How would you classify this patient’s acid-base status?
b) How does this patient’s hyperventilation pattern raise the pH of the blood?
c) How might the kidneys respond to this acid-base disturbance?
d) List some other causes of this type of acid-base disturbance.
Q.12-A 28-year-old woman has been sick with the flu for the past week, vomiting several times every day. She is having a difficult time keeping solids and liquids down and has become severely dehydrated. After fainting at work, she was taken to a walk-in clinic, where an IV was placed to help rehydrate her. Arterial blood was drawn first, revealing the following:
| pH | 7.50 |
| pCO2 | 40 mm Hg |
| pO2 | 95 mm Hg |
| Hemoglobin – O2 saturation | 97% |
| [HCO3-] | 32 meq /liter |
a) How would you classify her acid-base disturbance?
b) Why might excessive vomiting cause her particular acid-base disturbance?
c) How would the kidneys compensate for this acid-base disturbance?
d) List some other causes of this type of acid-base disturbance.