## **Core Concept**
The patient's symptoms of anxiety, sweating, and tachycardia after discontinuing Total Parenteral Nutrition (TPN) and starting a balanced salt solution (Ringer's lactate) suggest a reaction related to the abrupt change in his management, particularly concerning for a metabolic or electrolyte imbalance.

## **Why the Correct Answer is Right**
The symptoms described are classic for hypoglycemia, which can occur when glucose-containing TPN is abruptly stopped without adequate replacement. TPN solutions contain glucose, which provides a continuous source of glucose to the body. When TPN is discontinued, especially in a fasting state or without adequate glucose replacement, blood glucose levels can drop. This drop triggers a stress response, leading to symptoms such as anxiety, sweating, and tachycardia due to the release of stress hormones like adrenaline and cortisol.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is not provided, but typically, causes not directly related to metabolic or electrolyte imbalances due to TPN cessation would be less likely given the context.
- **Option B:** Similarly, without the specific content of Option B, we can infer that any choice not directly addressing hypoglycemia or related metabolic disturbances would be incorrect based on the symptoms described.
- **Option C:** Again, without specifics, any option not aligning with the pathophysiology of hypoglycemia or its symptoms would not be correct.
- **Option D:** Assuming this is not the correct answer, it would likely represent an alternative cause not supported by the clinical scenario provided.

## **Clinical Pearl / High-Yield Fact**
A crucial point to remember is that when discontinuing TPN, especially in patients who have been receiving it for an extended period, it is essential to either continue the TPN at a reduced rate or provide an alternative source of glucose to prevent hypoglycemia. This can be achieved by administering a dextrose solution (e.g., D10W or D5W) concurrently with or immediately after stopping TPN.

## **Correct Answer:** D. Hypoglycemia.