Neurogenic shock

[Sonia usmle]

Whats the mechanism of neurogenic shock causing decrease in CO ?

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[iscream4icecream]

Whats the mechanism of neurogenic shock causing decrease in CO ?

no more sympathetic control of vascular tone --> decrease in total peripheral resistance that can't be compensated for with autonomics

 

[Sonia usmle]

Autonomic compensation cant be done to increase CO thus CO remains decreased
This uncompensated decreased SVR could lead to reduced pul vascular resistance and reduced venous return --> reduced preload ???
Is this concept correct?
If so, decrease in preload and CO are all due to failure of compensation on reduced TPR. . .

 

[ukmedstudent1]

Autonomic compensation cant be done to increase CO thus CO remains decreased
This uncompensated decreased SVR could lead to reduced pul vascular resistance and reduced venous return --> reduced preload ???
Is this concept correct?
If so, decrease in preload and CO are all due to failure of compensation on reduced TPR. . .

I do not think that the fall in CO is all due to failure to compensate for reduced TPR.

CO: HR X SV.
in neurogenic shock, there is a loss of sympathetic outflow (if the lesion is above L1). As a result:
HR decreases (bradycardia) because of a reduced sympathetic drive and an unopposed parasympathetic outflow (via intact vagal nerves) to SA nodes
SV decreases; as you have correctly pointed out, there is a reduction in venous return because of peripheral vasodilation and blood pooling away from the heart

 

[Sonia usmle]

I do not think that the fall in CO is all due to failure to compensate for reduced TPR.

CO: HR X SV.
in neurogenic shock, there is a loss of sympathetic outflow (if the lesion is above L1). As a result:
HR decreases (bradycardia) because of a reduced sympathetic drive and an unopposed parasympathetic outflow (via intact vagal nerves) to SA nodes
SV decreases; as you have correctly pointed out, there is a reduction in venous return because of peripheral vasodilation and blood pooling away from the heart

Thank you. I missed to think about the reduced HR due to loss of sympathetic control in neurogenic shock
I got it.