218 km of racing, 80 of which uphill, for a total of 5500 m of climbing: an estimate energy expenditure of 5000-7000 kcal, depending on the weight of the athlete.
Nutrition and hydration during the race (today it was quite hot too) become the most determining factors.

Ivan Basso was therefore very good at hiding his stomach problem and to mask his real condition until the final ascent, thus limiting his delay on the finish line (just over 1 minute from new pink jersey Savoldelli).  

Will he be able to recover in less than 20 hours?
He did not seem to be completely empty at the end of the stage, so if the cause for the problem was occasional and temporary he should be able to regenerate his glycogen stores and to rehydrate his organism properly.

Would be interesting to ask WADA if in his case the use of drip is to be considered a doping practice...