That website gave me one of the answers I was looking for about septic shock and the sympathetic nervous system so thank you!
Ok... so here are my thoughts. We are just covering Cardiogenic, hypovolemic, septic, and obstructive shock right now, so I will give you my thoughts on these and please let me know if I'm on the right track or not. This may be kinda long, so please stay with me :-)
In Cardiogenic Shock, the heart is not pumping effectively. This will result in decreased Cardiac Output (CO) and decreased BP. In response, the HR increases and the sympathetic nervous system (SNS) is activated, causing vasoconstriction in an effort to maintain perfusion. Blood is shunted away from kidneys, GI tract, skin, and lungs, and sent to the heart and brain. This vasoconstriction leads to increased Systemic Vascular Resistance (SVR) and increased Pumonary Vascular Resistance (PVR).
The left ventricle (LV)will not be pumping out enough blood, so it will back up into the pulmonary veins. This will cause an increase in Pulmonary Artery Wedge Pressure (PAWP). If it's backing up in the pulmonary arteries, it will back up into the pulmonary vasculature and then the pulmonary arteries. This is similar to heart failure - left sided heart failure can lead to right sided heart failure. Then, increased pressure on the right side of the heart will lead to increased pressure in the vena cava (increased Central Venous Pressure [CVP]), which will lead to hepatomegaly and splenomegaly.
There is decreased blood volume, either from things like hemorrhage or GI losses (absolute hypovolemia) or from third spacing as seen in burns (relative hypovolemia). The decreased blood volume will lead to decreased BP, increased HR, and increased SVR due to SNS activation in attempt to maintain perfusion to tissues. Pulmonary vasculature is also constricted in order to shunt blood to brain and heart, causing an increase in PVR.
There will be a decrease in venous return, so CVP is decreased and thus PAWP is decreased. (Does the PAWP always follow the CVP? I'm having a hard time wrapping my mind around how putting a catheter into the pulmonary arteries on the right side of the heart gives you info about the Left atrium... Is PWAP affected by CVP, SVR, or both? How can PVR be increased, but PAWP be decreased?) Do you know of a good resource I could look at to understand this better?) B/c there is less blood returning to the heart, less blood is being pumped out the left side of the heart so CO is decreased.
Microorganisms release toxins which cause damage to cells. The inflammatory response is activated, which leads to vasodilation, increased capillary permeability, and activation of the clotting cascade. Nitric oxide concentrations also rise in septic shock (thank you again for the awesome website reference! This is the info I was looking for!) and it plays a role in organ resistance to catecholamines, such as epinephrine and NE. There is also a deficiency of vasopressin. Therefore, the body will not respond to the SNS and hypotension results from the massive vasodilation that occurs.
Vasodilation leads to decreased BP and decreased SVP. HR increases to try to circulate more blood to the tissues.
Fluid leaks out of the vasculature into interstitial spaces. Because the body is not responding to the SNS, the pulmonary vessels are not affected (???) and thus the PVR remains unchanged.
Because fluid is leaking out, there is decreased blood volume, decreased venous return, and decreased CVP. Less blood is being pumped through the heart so PWAP decreases and CO decreases. (SVR is decreased and PVR remains unchanged, so there is less pressure in the pulmonary arteries.)
Last one! Obstructive shock:
something is blocking blood flow, which causes decreased CO and decreased BP. In response HR increases. My book is saying that SVR would be decreased, but I thought it would be increased in response to the SNS. Am I missing something here? I'm also thinking PVR would be increased due to action of the SNS.
Like if you have a pulmonary embolism, blood flow is blocked in the pulmonary circulation so less blood reaches the left side of the heart. (What happens with the PAWP? - I'm thinking because PVR is increased, PAWP should be increased also)
The PE reduces blood flow to the left side of the heart. Blood backs up into the pulmonary arteries, then the R ventricle and atrium, and eventually the vena cava, causing increased CVP.
If something happens to prevent the right side of the heart from filling, as in abdominal compartment syndrome, venous return will be decreased. There will be decreased CO, decreased BP, increased HR, and increased SVR (in response to the SNS). I'm thinking CVP would be decreased, PAWP would be decreased, and PVR would be increased (as result of SNS).
Phew...I'm tired of typing! Your opinion on my thought process would be greatly appreciated!