Assessment and management of patient based on microdialysis results

All patients in the intervention group with microdialysis glycerol > 400 μmol/ L during the first 48 h in three consecutive samples in the microdialysate will have an abdominal CT scan on POD 2. This examination will be reviewed by two senior radiologists allocated to this study and assessed according to the preexisting definitions of an abscess or radiologically visible anastomotic disruption. In the case of positive radiological findings, a subsequent CT scan will be performed according to algorithm (Fig. 1) and is described below. In the case where there is a clinical suspicion of an anastomotic leakage regardless of microdialysate values, an abdominal CT scan may be performed at the discretion of the surgeon at any time during the hospital stay, independent of microdialysate values. The CT scan will initially be assessed by the surgeon and the radiologist on call, but will also later be assessed independently by the two radiologists assigned to this study.

Algorithm for assessment of patients with microdialysis. Postoperative treatment algorithm - Assessment and management of patient based on microdialysis results. CT, computer tomography; ICU, intensive care unit; L, liter; POD, postoperative day

Assessment of glycerol, lactate, and pyruvate concentration is done by the surgeon.

If the glycerol level is ≥ 400 μmol/l in 3 consecutive samples at POD1, the abdominal drain is kept to POD 2, and a CT scan is performed. If a leakage is confirmed, treatment is initiated in the following manner:

Consider

Optimizing the location of the abdominal drain and/or

Insertion of a second abdominal drain and/or

Relaparotomy

IV antibiotics

Other therapeutic actions

Transferring the patient to a higher level of care

The patient will be further assessed with clinical signs, measurement of abdominal drain output, and microdialysis values. A repeat CT (or ultrasound/ MRI) scan later in the course will be performed if the microdialysate lactate-to-pyruvate ratio is ≥ 50 combined with a lactate ≥ 4 mmol/L in 3 consecutive samples (irrespective of the time since end of surgery. If a leakage is diagnosed, the treatment described above is initiated. A repeat CT scan in a patient diagnosed with a leakage is performed on the basis of new microdialysis values (both absolute levels, and the trends thereof), the clinical condition of the patient, amylase activities, and bilirubin measured in abdominal drains.

The decision to perform a new scan and how often this will be appropriate is an interdisciplinary assessment between the surgeons and the anesthesiologist. Abdominal drains are removed later in the course if microdialysate lactate-to-pyruvate ratio is < 50, combined with a lactate < 4 mmol/L in three consecutive samples and there is no other reason to postpone their cessation (no signs of bile, chylous or enteric stained fluid and/or at the surgeon’s discretion).

If glycerol is persistently < 400 μmol/l within the first 24 h the abdominal drains are removed at POD 1 (prerequisite: if no signs of bile, chylous or enteric stained fluid or at the surgeon’s discretion). After this, the patients are assessed and microdialysate results are reviewed. If microdialysate glycerol is persistently < 400 μmol/l over several PODs and the lactate-to-pyruvate ratio is < 50 combined with a lactate < 4 mmol/L, the patient is further mobilized and subsequently discharged. If the glycerol increases ≥ 400 μmol/l in 3 consecutive samples at a later stage, the patient is examined, and CT scan (or ultrasound/MRI) is performed (at the discretion of the surgeon). Further intervention undertaken will be as described above.

To improve adherence to the intervention protocols, the researchers arranged an introductory- and regular follow-up meetings with the surgical team during the ongoing trial. An allocated researcher was assigned for the daily contact with the surgical team. Study newsletters and bedside training for the ward nurses were regular events during the ongoing trial. To ensure participant adherence, the patients received daily follow-up by the research team during the hospital stay, and subsequently by telephone interview at 30 and 90 days after surgery.