A 50-year-old man on ICU has bilateral lower limb compartment syndrome following aortic surgery with prolonged cross-clamp time (4 hours). Bilateral fasciotomies are performed. Post-operatively, he develops a massive rise in CK (180,000 U/L), hyperkalaemia (K+ 7.0 mmol/L), metabolic acidosis, and myoglobinuria. What syndrome is this?