Your father has had an episode of hyponatremia.
Sodium helps maintain nerve and muscle function, and also helps to maintain blood pressure.
As the brain is very sensitive to sodium levels, low sodium causes confusion and lethargy. The patient may feel nauseated, and experience muscle twitching, which can progress to seizures. Eventually, severe hyponatremia can lead to coma and death.
Symptoms of moderate hyponatremia include tiredness, disorientation, headache, muscle cramps, and nausea. Severe hyponatremia can lead to seizures and coma. These neurological symptoms are thought to result from the movement of water into brain cells, causing them to swell and disrupt their functioning.
What about Adrenals, Low cortisol. I had that happen to me and it took 5 months for it to get figured out.