A palliative patient with multiple myeloma is now exhibiting symptoms of confusion, lethargy, anorexia, and constipation. Which of the following is the BEST nursing action?

While increasing laxatives may address constipation, it does not address the underlying causes of the patient's confusion and lethargy. In patients with multiple myeloma, symptoms can be multifactorial, and without understanding the biochemical status, this action may not be appropriate.

Although dexamethasone can be beneficial in treating symptoms related to multiple myeloma, such as pain or inflammation, it does not provide immediate insight into the patient's current condition. The symptoms presented could stem from metabolic disturbances that require further evaluation before medication adjustments.

Pulse oximetry is useful for assessing oxygen saturation but does not provide information about the metabolic status or electrolyte levels, which are more pertinent to the patient's symptoms of confusion and lethargy. This action might overlook the more pressing need for a thorough evaluation of the patient's biochemical state.