My 8 day old baby is suddenly hungry all the time and waking up every hour for a feed where she drains my breasts out completely. Could this be a growth spurt?

I don't think is grow spurt. A newborn's stomach is v small and they don't drink a lot at one go. Hence, for many newborns, they tend to feed every hourly and if you are bf, which is more diluted than fm, it is easily digested. Newborns poo fast and get hungry all over again. As they grow older, their stomach grows bigger and able to hold their hunger better.