What does the presence of nystagmus indicate in a patient given Ketamine?

The presence of nystagmus in a patient who has been administered Ketamine is an important clinical observation that indicates the patient may be experiencing an adverse reaction to the medication. Nystagmus refers to involuntary, rapid eye movements, which can suggest that the sedation level is potentially too deep or that the medication is affecting the central nervous system in an undesired manner.

When nystagmus is observed, it is best practice to stop giving Ketamine. Continuing with the administration could risk further worsening the patient's condition and lead to complications, as nystagmus may be a sign of impending respiratory compromise or other serious neurological effects.

The other options, such as increasing the dosage or switching to a different medication, do not address the immediate concern raised by the emergence of nystagmus and could exacerbate the situation. Therefore, stopping the administration of Ketamine is the appropriate and safest course of action in this scenario.