Case Vignettes in Acid-Base Balance Essay

Choose three of the four vignettes and BRIEFLY answer the questions that follow. Normal Levels of Substances in the Arterial Blood: pH 7.40 + 0.05 pCO2 (partial pressure of carbon dioxide) 40 mm Hg pO2 (partial pressure of oxygen) 90 – 100 mm Hg Hemoglobin – O2 saturation 94 – 100 % [HCO3-] 24 meq / liter Vignette #1: 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 Questions: 1. How would you classify this girl’s acid-base status? 2. How does cystic fibrosis cause this acid-base imbalance? 3. How would the kidneys try to compensate for the girl’s acid-base imbalance? 4. List some other causes of this type of acid-base disturbance. Vignette #2:  A 76-year-old man complained to his wife of severe sub-sternal chest pains 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 85 mm Hg / 50 mm pressure Hg Heart rate 175 beats / minute Respiratory rate 32 breaths / minute Temperature 99.2o F His breathing was labored, his pulses were rapid and weak everywhere, and his skin was cold and clammy. An ECG was done, revealing significant â€Å"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 Questions: 5. What is the diagnosis? What evidence supports your diagnosis? 6. How would you classify his acid-base status? What specifically caused this acidbase disturbance? 7. How has his body started to compensate for this acid-base disturbance? 8. List some other causes of this type of acid-base disturbance. Vignette #3: 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 Questions: 9. How would you classify this patient’s acid-base status? 10. How does this patient’s hyperventilation pattern raise the pH of the blood? 11. How might the kidneys respond to this acid-base disturbance? 12. List some other causes of this type of acid-base disturbance.