The Poskim debate the question of whether one may use very hot water for Netilat Yadayim before eating bread, and the Shulhan Aruch ruled that such water may be used. There is a general principle that in situations of uncertainty in regard to Netilat Yadayim, the lenient possibility may be followed, and one may even recite a Beracha. Therefore, one who uses very hot water for Netilat Yadayim before eating bread recites the Beracha of "Al Netilat Yadayim" as usual.
Surprisingly, however, the Yalkut Yosef comments that this rule does not apply regarding the morning Netilat Yadayim which one performs after waking up. Hence, one should not wash his hands with hot water in the morning, and if he does, he does not recite a Beracha.
Rav Yisrael Bitan suggests a possible explanation for the distinction between Netilat Yadayim for bread and the morning Netilat Yadayim. He draws a comparison to the laws of Erub Tehumin – the mechanism by which one may extend the distance he is permitted to walk on Shabbat. Normally, one may walk only two thousand Amot beyond his city, but if he places before Shabbat some food outside the city – at any point within two thousand Amot beyond the city limits – he can establish that location as his boundary line. He may then walk on Shabbat two thousand Amot beyond that location. For the Tehum Shabbat to be effective, it must be prepared before the onset of Shabbat. If one arranged it during Ben Ha'shemashot – the period between sundown and nightfall, whose status as night or day is uncertain – the Erub may be used on Shabbat, as he may rely upon the possibility that Ben Ha'shemashot is considered daytime, and the Erub was prepared before Shabbat. In this case, the individual recites a Beracha over the Erub – despite the Halachic uncertainty surrounding the Erub, as we are unsure whether it was prepared before Shabbat or after the onset of Shabbat. Normally, the rule of "Safek Berachot Le'hakel" establishes that a Beracha may not be recited in situations of doubt. In this case, however, a Beracha is recited. Rav Bitan explained that since Halacha allows the individual to act upon this Erub, as he may walk two thousand Amot beyond that location, a Beracha may be recited. As there is practical expression to the Erub's validity, this situation is not treated as one of Halachic uncertainty, and therefore a Beracha is warranted.
Rav Bitan applies this line of reasoning to Netilat Yadayim before bread. In a situation where Halacha accepts the validity of one's washing after the fact, despite the uncertainty involved, and permits the individual to eat bread, then necessarily, he may recite the Beracha. Since Halacha allow acting upon the washing, the Beracha may be recited. In the morning, however, the obligation of Netilat Yadayim stands alone, and is not a precondition for a subsequent act. Therefore, as there is no practical Halachic expression to the validity of the washing, a Beracha may not be recited if there is some uncertainty regarding its legitimacy.
Therefore, one who, for whatever reason, washes with scalding hot water in the morning, does not recite the Beracha.
Needless to say, it is best to avoid this situation and to use lukewarm or cold water for the morning Netilat Yadayim. If one has access only to very hot water, then he should wait a few minutes for the water to cool before washing Netilat Yadayim.
Summary: One should wash the morning Netilat Yadayim with lukewarm or cold water. If one has access only to very hot water, then he should wait a few minutes for the water to cool before washing Netilat Yadayim. If he cannot wait, then he may use the hot water, but should not recite the Beracha.