What is the most likely cause of Keenan's increased confusion after missing dialysis?

Keenan's increased confusion after missing dialysis is most likely caused by the accumulation of toxins. In patients with renal failure, the kidneys are unable to effectively filter and eliminate waste products from the bloodstream, leading to a buildup of urea, creatinine, and other metabolic toxins. When dialysis is missed, these substances can reach toxic levels, particularly affecting the central nervous system and resulting in symptoms such as confusion, lethargy, or even seizures.

The other options, while they may contribute to confusion under different circumstances, are less likely to be the primary cause in the context described. Medications can indeed cause cognitive changes, but without specific information indicating recent changes to his medication regime, this is less likely the sole contributor in this scenario. Hypoglycemia could cause confusion as well, but dialysis patients typically have regulated blood glucose levels, especially if they are on dialysis regularly. Electrolyte imbalances, while possible, often arise from the inability to excrete waste, and confusion primarily due to electrolyte issues often presents with more pronounced physical symptoms. Therefore, the buildup of toxins due to missed dialysis is the most direct and likely explanation for Keenan's increased confusion.