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NBME 27 Answers

nbme27/Block 2/Question#5 (reveal difficulty score)
A 45-year-old man is undergoing a surgical ...
Decreasing respiratory rate ๐Ÿ” / ๐Ÿ“บ / ๐ŸŒณ / ๐Ÿ“–

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submitted by โˆ—shak360(14)

Cerebral perfusion is primarily driven by PaCO2. Therapeutic hyperventilation (increased respiratory rate) will lead to decreased PaCO2 resulting in vasoconstriction, decreased cerebral blood flow, and reduced intracranial pressure. This is a common technique used in the treatment of acute cerebral edema.

Likewise, hypoventilation (decreased respiratory rate) will lead to an increased PaCO2 resulting in vasodilation, increased cerebral blood flow, and increased intracranial pressure (as seen in the question).

This also implies that cerebral perfusion pressure is directly related or proportional to PaCO2, but is inversely related to PaO2

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