An elderly man was admitted with an acute abdomen and free air visible under the diaphragm on CXR. He was fluid resuscitated before undergoing emergency laparotomy, where a perforated duodenal ulcer was oversewn. He was admitted to ICU postoperatively, extubated the next morning and deemed fit for discharge to the surgical ward later that day. Due to a lack of surgical beds, he was eventually discharged from ICU at 22:30. Eight hours post discharge, he was urgently re-referred to ICU after being found moribund on the ward. Before he could be seen and assessed he suffered an unrecoverable asystolic arrest. Review of his observation charts showed that there had been a clear deterioration in recorded observations, including hypotension for the two preceeding hours. However, the Early Warning Score had been calculated incorrectly, and no escalation had occurred.
What evidence is there that rapid response systems are effective in preventing patient deterioration and improving outcomes?