The primary objective of this study is to determine the effect on complication severity of using a clinical monitoring system with automatic vital sign alerts in addition to routine monitoring versus routine monitoring alone in high-risk postoperative cancer patients within 30 days after surgery.

Other objectives include documentation of the severity of complications within seven days of surgery, frequency of serious adverse events, mortality, length of stay and delay of planned chemotherapy.

The primary objective of this study is to determine the effect on complication severity of using the WARD-CSS with automatic alerts in addition to routine monitoring versus routine monitoring alone in high-risk postoperative cancer patients within 30 days after surgery.

This study is a multicenter randomized controlled trial (RCT). Patients are randomly assigned to one of two parallel monitoring groups: (1)Intervention group - Monitoring by the WARD-CSS including vital signs and active alerts relayed to the nurses' smartphones during hospitalization. (2)Control group - Blinded data collection by the WARD-CSS without vital signs and active alerts displayed to the ward staff.

Both groups will receive routine vital signs monitoring (i.e. manual spot-checks) using the regional EWS/TOKS system according to current standards of care at the participating hospitals in the Capital Region or the Central Denmark Region.

The study is a collaboration between Rigshospitalet, Bispebjerg and Frederiksberg Hospital, and Hvidovre Hospital.

Patients will be recruited from abdominal (gastrointestinal, gynecological, or urological) surgery wards at the study sites.

Patients will be randomized post-surgery at the postoperative units/ post-anesthesia-care unit or after arrival at the ward. Continuous wireless monitoring (i.e., unblinded with alerts or blinded) will commence immediately after randomization in the study.

Only randomized patients will be included in the study population. Drop-outs prior to randomization will not be part of the study population.

The first 14 days of active enrollment at each new study site that has not previously used WARD-CSS will be used to align study procedures, verify system connectivity, etc. During this period, up to ten patients at each study site will be enrolled to be monitored similar to the intervention group. These run-in patients will not be randomized and will not be considered part of the study population.

Inclusion Criteria:

• Admission for elective major abdominal (gastrointestinal, gynecological, or urological) surgery with the primary aim of radical surgery/removing suspected cancer tissue.
• At least two expected postoperative admission days
• Laparotomy or laparoscopy procedure estimated to last more than 2 hours.
• Co-enrolment of patients in other studies is acceptable but in studies involving interventions which potentially will affect the continuous monitoring of vital signs and/or the primary or secondary outcomes, an assessment of whether these patients can be co-enrolled in the WARD-RCT should be conferred with the WARD RCT steering committee.

Exclusion Criteria:

• Patient expected not to cooperate with study procedures
• Allergy to study materials (silicone, plaster)
• Impaired cognitive function (in uncertain cases assessed by a Mini Mental State Examination score < 24). (Protocol Appendix E)
• Patients with a pacemaker or Implantable Cardioverter Defibrillator (ICD) device
• Inability to give informed consent
• Patients with planned hyperthermic intraperitoneal chemotherapy (HIPEC) procedure or two-stage resections (two-stage hepatectomy, two-stage resection of malignant colorectal obstructions, etc.)

No plan to share IPD

Participants will not be given information on group allocation. Care-providers will not be blinded, due to having to carry out the intervention.

Investigator will not be blinded to carrie out roles such as safety surveillance, error-solving and quality assurance.

Outcome assessor will be blinded to study allocation.