**Core Concept**
Gastric lavage, also known as stomach pumping, is a procedure to remove harmful substances from the stomach. However, its use is limited due to several contraindications and potential complications. This question tests the understanding of situations where gastric lavage is not recommended.

**Why the Correct Answer is Right**
The correct answer is related to the timing of gastric lavage. Gastric lavage is generally contraindicated in patients with altered mental status or decreased level of consciousness, as they are unable to protect their airway during the procedure. Additionally, gastric lavage should not be performed more than an hour after ingestion, as the absorption of toxins may have already occurred. This is why the correct answer is related to the timing of gastric lavage.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because aspiration of gastric contents is a well-known complication of gastric lavage, especially in patients with altered mental status or decreased level of consciousness. Aspiration can lead to pneumonia, aspiration pneumonitis, or even death.

**Option B:** This option is incorrect because gastric lavage is contraindicated in patients with esophageal or gastric perforation. Performing gastric lavage in such cases can exacerbate the injury and lead to further complications.

**Option C:** This option is incorrect because gastric lavage is contraindicated in patients with severe hematemesis or active bleeding. Performing gastric lavage in such cases can lead to further bleeding, hypovolemic shock, or even death.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that gastric lavage should only be performed by trained healthcare professionals in a controlled environment, and only in cases where the benefits outweigh the risks. The American Academy of Clinical Toxicology (AACT) recommends against the routine use of gastric lavage in the treatment of poisoning.

**Correct Answer:** D.