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Clinical Case Study
The Car Accident: A Case Study in Acid-Base Balance

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Mr. Henderson, a 52-year-old male, was on his way to work during a heavy rainstorm when he lost control of his car and crossed into oncoming traffic where he collided head-on with a small delivery truck. Witnesses accessed the 911 emergency medical response system, and paramedics arrived quickly. The driver of the truck suffered only minor cuts and scrapes, but Mr. Henderson was having difficulty breathing and complaining of severe chest pain. Transport time to the nearest trauma center was less than two minutes, so the emergency personnel elected to "scoop and haul." A large bruise on his chest indicated that Mr. Henderson had experienced blunt trauma from the impact of the steering wheel after the airbag failed to deploy.

Mr. Henderson presented in the ER with blurred vision, dizziness, headache, nausea, muscle weakness, hypoventilation, and a feeling of mental confusion. A chest X ray revealed bilateral fractures in the fourth, fifth, and six ribs along with a suspected hemothorax. An ECG revealed signs of ventricular arrhythmias. The values following values were taken from the results of an arterial blood gas (ABG) and urinalysis (UA).

Arterial Blood Gas (ABG) High or Low
pH:7.0 Low
bicarbonate:29 mEq/LHigh
Urinalysis (UA)

Short Answer Questions

  1. Define the following terms contained in this case:
    1. Bilateral
    2. Hypoventilation
    3. Hemothorax
    4. Arrhythmias
  2. What are the normal ranges for the measurements listed in the blood and urine tests?
  3. Explain how Mr. Henderson's rib fractures are related to the suspected hemothorax.
  4. Mr. Henderson's PCO2 is elevated. Under normal conditions, what would be the PRIMARY mechanism that his body would use to reduce the amount of PCO2 in the blood? Why is this mechanism not working in this case?
  5. Describe how the high PCO2 and low pH in Mr. Henderson's blood are related in this case.
  6. Describe how the high bicarbonate in Mr. Henderson's blood is related to the low pH in his urine.
  7. What type of intervention might the doctors and nurses initiate in order to address the hemothorax? Explain how this intervention will lead to changes in PCO2 and blood pH.

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