## Core Concept
The question tests the understanding of cardiovascular physiology, specifically the effects of changes in total peripheral resistance (TPR) on blood pressure and cardiac output. Total peripheral resistance is a critical determinant of blood pressure, and its sudden increase can have immediate effects on the cardiovascular system.

## Why the Correct Answer is Right
A sudden increase in total peripheral resistance leads to an increase in afterload, which is the resistance against which the heart must pump blood. This typically results in an increase in blood pressure because the same volume of blood is being pumped against a higher resistance. The heart must work harder to eject blood into the circulation. According to the Frank-Starling mechanism, an increase in afterload can initially decrease stroke volume and cardiac output if the heart cannot compensate for the increased resistance.

## Why Each Wrong Option is Incorrect
- **Option A:** An increase in TPR increases blood pressure due to the increased resistance against which the heart pumps. Therefore, this option is a correct effect of increased TPR, making it an incorrect choice for "Except."
- **Option B:** Reflex tachycardia often occurs in response to a sudden increase in blood pressure caused by increased TPR. The baroreceptors sense the increased blood pressure and trigger a reflex decrease in parasympathetic tone and increase in sympathetic tone, leading to an increase in heart rate. So, this option is also an effect of increased TPR.
- **Option C:** A decrease in renal blood flow can occur due to increased TPR. As blood pressure increases and cardiac output might decrease, renal perfusion can decrease. This is a plausible effect, making it incorrect for "Except."
- **Option D:** A decrease in cardiac output might not immediately occur if the heart can compensate for the increased afterload through mechanisms like the Frank-Starling law and increased contractility (e.g., via the Anrep effect). However, a more direct and immediate effect related to the question context would likely involve changes in blood pressure and heart rate.

## Clinical Pearl / High-Yield Fact
A key point to remember is that total peripheral resistance is influenced by the radius of arterioles, which are primarily controlled by the sympathetic nervous system. A sudden increase in TPR can be seen in conditions like hypertension or during intense sympathetic stimulation.

## Correct Answer: D.