An ICU patient on atracurium infusion develops seizures after 2 days. The most probable cause is:

## **Core Concept**
Atracurium is a non-depolarizing neuromuscular blocking agent used in intensive care units (ICUs) to facilitate mechanical ventilation. One of its metabolites, **laudanosine**, is known to have central nervous system (CNS) stimulating effects and can accumulate with prolonged infusion, especially in patients with renal or hepatic impairment.

## **Why the Correct Answer is Right**
The development of seizures in an ICU patient on a prolonged infusion of atracurium is most likely due to the accumulation of **laudanosine**. Laudanosine can cross the blood-brain barrier and cause CNS excitation, leading to seizures. This is particularly concerning in patients with renal or hepatic dysfunction, as these conditions can impair the clearance of laudanosine. The time frame of 2 days aligns with the potential for significant accumulation and toxicity.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because, without specifying the content, it's impossible to assess its relevance to laudanosine toxicity or another mechanism.
- **Option B:** Similarly, this option lacks specificity and does not directly relate to known causes of seizures in the context of atracurium infusion.
- **Option C:** This option is incorrect as it does not provide enough information to consider it a plausible cause for seizures related to atracurium infusion.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **atracurium should be used cautiously in patients with renal or hepatic impairment** due to the risk of laudanosine accumulation and neurotoxicity. Monitoring for signs of CNS excitation, such as seizures, is crucial in patients on prolonged atracurium infusions.

## **Correct Answer:** D. Laudanosine toxicity.