Question: As a curious student, with great technical skills, you decide to sample the blood of one of your patients. He is a 68 year old man with metabolic syndrome. Platelet count is 110, albumin is 3.2, INR is 1.6 and serum sodium is 132. You decide to sample blood from the superior mesenteric artery as well as the hepatic sinusoid, and test levels of nitric oxide. Which combination of results are you most likely to see?
A. SMA low; sinusoid low
B. SMA high; sinusoid high
C. SMA high; sinusoid low
D. SMA low; sinusoid high
Answer: Nitric oxide is a key player in the hyperdynamic state of portal hypertension. To answer this question, you first had to realize that NASH is a component of the metabolic syndrome, and that this aged patient has probably developed NASH-induced cirrhosis. The thrombocytopenia, synthetic dysfunction and hyponatremia should have given that away.
In such patients, with advanced stage disease, nitric oxide levels are deranged. The splanchnic arterial system includes the superior and inferior mesenteric arteries as well as arteries from the celiac trunk; these all see elevated levels of nitric oxide and are thus vasodilated. In turn, there is a higher volume of blood flow that finds its way to the portal vasculature and will increase the hydrostatic pressure within the hepatic sinusoid.
Conversely, there is a paucity of nitric oxide within the liver (as well as increased catecholamines) leading to vasoconstriction; this also increases the hydrostatic forces within the liver. The end result…worsened portal hypertension. The correct answer choice is C.