You posted your question 3 days ago and have yet to get an answer. This probably indicates that no one, including me, is sure what to advise you.
Let's take the issues one at a time:
*Nausea: This reminds me of my experience years ago in boot camp when the sergeants said, "Run, kid." Running can cause distress, such as side stitches (affects my wife) and nausea (affected me in basic training in the Army, but I was a relatively strong runner by advanced training). These symptoms may disappear with more marathon experience.
*Tunnel vision: Welcome aboard. If you had been able to focus on your fellow runners in the finish chute, you might have noticed that they were not focused on you. Race directors never ask runners to do anything in the chutes except keep walking, because the directors' experience is that all runners are like you--slightly oblivious to their surroundings and completely unable to follow instructions.
*Hot: This is dangerous. Heat can kill. You need to determine the cause of this problem and correct it. Perhaps you are overdressed. Perhaps you don't have sufficient salt (the Army said, "Take two salt tablets and drive on.") Perhaps you need a hat or Coolmax fabrics. Perhaps there is a medical problem. Whatever, this is a serious issue that requires caution on your part.
*Drinks: You drink water. Do you drink sports drinks, as you should? See Rich's posting somewhere here on his excellent advice on how to hydrate prior to, during, and after, a marathon.
*Post-race behavior: Walk directly to the refreshment table. Eat the carbohydrates and drink whatever they offer (often, ug, hot bottled water but sometimes cold beer!). Don't sit until you lose the tunnel vision.
I hope you get a better answer from a health professional. Keep us posted on any non-MarathonGuide advice you receive.
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