Definition of circulatory shock

Study 3
Blanche Devereaux is a 78-year-old widow who was brought to the emergency room one evening by her sister. Earlier in the day, she had seen bright red blood in her stool. She continued with her daily activities. However, the bleeding continued all day. By dinnertime, she could no longer ignore it. Blanche takes aspirin, as needed, for arthritis, sometimes up to 12 tablets daily. In the emergency room, she was light-headed and her skin was pale and cool to the touch. Her hematocrit was 26% (normal for women, 35%-45%). The ER doctor ordered orthostatic vital signs. Below are the results of the test:
Measurement Supine Standing
Blood Pressure 88/60 74/46
Heart Rate 106 bpm 130 bpm

12. What is the definition of circulatory shock? What are some causes of circulatory shock (Review pages 273 through the top of 276 in Guyton and Hall)?
13. After blood loss, what is the fundamental problem in shock? Why does shock occur due to loss of blood?
14. Calculate Mrs. Devereaux’s pulse pressure and mean arterial pressure while supine and standing.
15. What was the compensatory mechanism that leads to her heart rate being fast in both positions?

Study 4
Mr. Ortega returned to the hospital after a recent myocardial infarction. He has experienced a number of fainting spells. The cardiac rehabilitation nurse reports that his PR intervals were longer than normal. Although his QRS complexes had a normal configuration, there were occasional nonconductive P waves, P waves that are not followed by QRS complexes. His physicians believed that a recent myocardial infarction caused a block in his atrioventricular conducting system (Review pages 115 through 118 in Guyton and Hall).

16. What does the PR interval on the ECG represent? What is the normal value?
17. What does the QRS complex on the ECG represent? What is implicit in the information that the QRS complexes on Mr. Ortega’s ECG had a normal configuration?
18. How is it possible to have P waves that are not followed by QRS complexes?
19. Why did Mr. Ortega faint?
    Case 5
    Tim celebrated his dental school acceptance by completing the seven days trek to Machu Pichu (Day 7: Aguas Calientes elevation 2,430 m). Tim is in good physical condition. He runs 3-5 miles per day, weight trains, and plays midfield in the local soccer club. (Review pages 527-the top of 531 in Guyton and Hall).
20. Describe Tim’s normal O2 saturation curve and the curve at 2,430 m.