Is it possible to prevent hemolysis?

Depends. Are you talking about hemolysis in vivo or in a specimen? There are many caused of hemolysis and each needs a different approach. See this site for info on hemolytic anemia.
Depends. There are scores of different hemolytic anemias, each with its own cause and characteristic behavior. These qualities determine how we treat them, and some causes of hemolysis are more treatable than others. That's the best i can do without more information. Sorry.