**Core Concept**
Increased intracranial tension (ICT) requires careful management during anesthesia to avoid further complications. Anesthetics with cerebral vasodilatory properties can worsen ICT, whereas those that cause cerebral vasoconstriction may be beneficial in this context.

**Why the Correct Answer is Right**
Isoflurane is a halogenated ether that causes cerebral vasoconstriction, which is desirable in patients with increased ICT. This property helps to decrease intracranial pressure (ICP) by reducing blood flow to the brain. Isoflurane's ability to cause cerebral vasoconstriction makes it a suitable choice for anesthesia in patients with increased ICT.

**Why Each Wrong Option is Incorrect**
**Option A:** Nitrous oxide (N2O) is a potent cerebral vasodilator, which can worsen increased ICT by increasing cerebral blood flow and ICP.
**Option B:** Trilene, also known as trichloroethylene, is not typically used for anesthesia due to its potential for hepatotoxicity and nephrotoxicity. It also has vasodilatory properties, making it unsuitable for patients with increased ICT.
**Option C:** Ether is an older anesthetic agent that has been largely replaced by newer agents due to its flammability and potential for irritation to the respiratory tract. While it may have some vasodilatory effects, it is not the best choice for anesthesia in patients with increased ICT.

**Clinical Pearl / High-Yield Fact**
When managing patients with increased ICT, it's essential to choose an anesthetic agent that causes cerebral vasoconstriction, such as isoflurane or desflurane, to help decrease ICP and prevent further complications.

**✓ Correct Answer: D. Isoflurane**