Count to 10 - Anaesthetic Primary Podcast EP28 – Applied Cardiac Physiology Part 2 | Anaesthetic Primary Topic | Cardiac Physiology | CT10
Oct 13, 2024
Dive into the physiological aftermath of arterial tourniquet release and the surprising mechanisms of hypotension and desaturation. Explore how oliguria emerges in hypovolemic shock, and compare cardiovascular responses to severe blood loss between alert patients and those under anesthesia. Discover the impacts of infusing Hartmann's solution and the nuances of intermittent positive pressure ventilation on cardiac output. Finally, learn about the cardiovascular effects of central neuraxial blocks, CO2 pneumoperitoneum, and how aging and obesity alter heart dynamics.
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How To Structure Tourniquet Release Answers
- Expect hypotension, desaturation and hypercarbia after a 2-hour arterial tourniquet is released and explain each mechanism clearly.
- Cover venous return/MSFP, mixed venous O2 dilution, and CO2 from buffering plus resumed aerobic metabolism.
Mixed Venous Return Explains Transient Desaturation
- Desaturation after tourniquet release is mainly due to low mixed venous O2 returning from the ischemic limb.
- Local metabolite-mediated right shift and increased extraction amplify arterial desaturation.
Why CO2 Rises After Tourniquet Release
- Hypercarbia post-release arises partly from buffering of accumulated H+ via the carbonic acid reaction, not anaerobic CO2 production.
- Resumption of aerobic metabolism in the limb then produces additional CO2 entering circulation.