What if Napoleon had been defeated at the battle of Marengo?

Napoleon only managed to win the battle of Marengo, in 1800, out of incredible luck. He had been outgeneraled, outfought, outstrategized and basically ambushed, and was on the verge of total defeat. Then, a close general friend of his got himself killed rushing in reinforcements, and, almost simultaneously, the Austrian forces were thrown into confusion by the explosion of their ammunition wagons in the middle of their forces. This combination of events was sufficient to turn the tide of the battle. What if Napoleon had, really, lost the battle of Marengo? Would he have been captured, or perhaps killed? Would that have been the end of Napoleon's career? How would that have affected the future course of European, and of world history?