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Hey guys,
Not really related to USMLE, but had a physiology question that might help reinforce some of the things you are learning right now.
One of the things my preceptor asked me today was why hypertension, but not RR or HR, often follow stroke. Intuitively, it makes sense because your brain is trying to increase its cerebral perfusion pressure (CPP = MAP - ICP).
However, my understanding of this is that the build up of CO2 due to lack of perfusion leads to CO2 diffusing into the CSF. CO2 then gets converted into HCO3- and H+ through the whole CA reaction. This H+ then stimulates central chemoreceptors in the medulla leading to sympathetic activation (Increased HR, RR, BP).
Why then, is there only an increase in BP seen after stroke? The only options I have come up with so far:
1) The hypertension was there before the stroke first since it is not only a risk factor but also a possible cause of stroke.
2) Patients are on medications such as B-blockers which prevent increase HR (RR shouldn't be affected through...)
Not really related to USMLE, but had a physiology question that might help reinforce some of the things you are learning right now.
One of the things my preceptor asked me today was why hypertension, but not RR or HR, often follow stroke. Intuitively, it makes sense because your brain is trying to increase its cerebral perfusion pressure (CPP = MAP - ICP).
However, my understanding of this is that the build up of CO2 due to lack of perfusion leads to CO2 diffusing into the CSF. CO2 then gets converted into HCO3- and H+ through the whole CA reaction. This H+ then stimulates central chemoreceptors in the medulla leading to sympathetic activation (Increased HR, RR, BP).
Why then, is there only an increase in BP seen after stroke? The only options I have come up with so far:
1) The hypertension was there before the stroke first since it is not only a risk factor but also a possible cause of stroke.
2) Patients are on medications such as B-blockers which prevent increase HR (RR shouldn't be affected through...)
