mostly women and children, have fled ukraine since the russian assault began last week. but amid shelling around kyiv some of the most vulnerable residents can t leave. as cnn s clarissa ward reports, they re the children being treated at ukraine s largest children s hospital. reporter: outside the akhmadid hospital the sound of heavy fighting pierces the night air. the shelling has started, this nurse says. we re in the surgical department for newborn babies. it s so loud. exhausted staff hover nervously in the hallway. this is ukraine s largest children s hospital. shutting down is not an option. we decided to open our surgical department here. reporter: neurosurgeon dimitri yashenko shows the impact of just one week of war. so the children who are too sick