Four causes of syncope (dizziness) come to mind when I was on Folfirinox treatment.:

Orthostatic hypotension (postural hypotension) is one common cause. It happens after lying or sitting down. It happened to me several times with the worst episode of passing out and hitting the ground. A cardiovascular exam found no issues with cardiac output, BP or occlusions in the arteries.

A second cause is dehydration and this was my most frequent cause, especially when I was on Folfirinox. Post infusion hydration therapy was helpful in stopping it.

Vertigo (Benign Paroxsimal Positional Vertigo-BPPV) also happened when on Folfirinox. It results from crystals of calcium carbonate in a semi-circular canal of the inner ear that break off and float into a different semi-circular canal affecting balance. If diagnosed, there is a procedure done by an occupational therapist making head positional movements to get the crystals back into the middle loop. There are YouTube videos for self-treatment if diagnosed, but I found it just as easy seeing an occupational therapist that resolved the symptoms within minutes.

The fourth cause was occurring from a maintenance drug I take that causes anemia. With a significant decrease in RBC’s, Hgb and HCT parameters, there is less oxygen carrying capacity of RBC’s.I would notice the symptoms doing strenuous activities, getting up suddenly from a lying position or after squatting. That was the clue I needed to take a short break from the medication to give the bone marrow a rest so more RBC’s got produced. When caused by suppression by medication impacting the bone marrow, it took about three weeks to recover. I am aware of onset of symptoms and don’t try to push it to the point I would need a transfusion. Taking pauses every six months of the drug has been effective.