Electrolyte imbalance can certainly cause confusion, especially low sodium. If it's enough to cause confusion IV supplementation will probably be required, as GravelyGuy notes. However, bloodwork is required to confirm this.
Chemo can cause fatigue especially if hemoglobin is low. Why has he been anemic for so long?
D/H Dx 10/2019 RC age 61
Clinical T4bN2M1a (common iliac and para-aortic lymph nodes)
MSS KRAS G12D
CRT 11/19-1/20 FOLFOX 3/20-7/20
Pelvic exenteration w/LAR 8/20
ypT4bN0Mx G3 0/14 nodes LVI not seen PNI-
CEA 10/19:20, 1/20-11/20:1.6, 4.3, 3.4, 2.7, 2/21:9.0 3/21:18,40 4/21:28,19, 5/21:13.3,8.6
PET 3/21 recurrence in distal nodes, L5 vertebra, pelvis