A 68-year-old man on ICU with acute liver failure develops grade 4 hepatic encephalopathy (coma, unresponsive) and bilateral fixed dilated pupils. ICP monitoring shows an ICP of 45 mmHg. CT head shows severe cerebral oedema. He was listed for emergency liver transplantation but has now developed uncontrollable intracranial hypertension. According to King's College Hospital criteria, what is the significance of uncontrollable intracranial hypertension in the context of liver transplantation?