No response IS a response.
Sometimes, "not doing anything", simply holding space for a child's feelings and refraining from talking and teaching (sensory input that can add to a child's overwhelm) is what's needed when a child is in a heightened state. Emotional security and safety is the priority. Everything else can come later. And by “doing nothing”, you’re not condoning inappropriate behaviour.
How do we signal emotional security and safety? It will look a little different for each child. Some children benefit from a hug, some would prefer you didn't touch them. Some benefit from eye contact, others find this threatening. Some benefit from you sitting close, others need space. Some benefit from a few reassuring words, others need complete silence. Talking and teaching can come later if necessary, with when exactly again depending on each child.
When a child is in a heightened state, often, LESS is MORE.