An observational study in Reconstructive Surgery and Flap Monitoring, sponsored by Leiden University Medical Center. Not yet recruiting at 3 sites in Netherlands. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-21.
Sponsored by Leiden University Medical Center · Observational
After some operations in which tissue is removed, it is necessary to repair the defect with a piece of tissue from another location in the body. This is called a microsurgically transplanted tissue flap (or tissue flap, for short). It is important that, after an operation, enough blood flows to the relocated tissue. In this study, we want to investigate whether, after the operation, measuring oxygen in the tissue flap with the INVOS 7100c device helps detect blood flow problems earlier. In the future, this could help doctors intervene more quickly, thereby reducing the risk of complications.
Reconstruction of defects using free flaps has become increasingly popular. However, vascular compromise is a potential postoperative complication leading to ischemia of (parts of the) flap. Early detection of perfusion problems is pivotal and directly correlated with increased flap salvage. Currently, detection of flap ischemia relies on frequent postoperative clinical inspection of the flap and the assessment of doppler signal of the (perforator) artery of the flap. These inspections are labor intensive and potentially suboptimal as these inspections are done in one- to four-hour intervals. Near infrared tissue oximetry using INVOStm monitoring technique allows for continuous monitoring of the flap, which may improve detection of flap ischemia and reduce the work load for health care personnel. Previous studies using NIRS for free flap monitoring have reported promising results, but available evidence is limited by differences in NIRS devices, algorithms, flap types, monitoring protocols, sensor placement, definitions of vascular compromise and proposed alarm thresholds. In addition, practical aspects of prolonged postoperative monitoring on a recovery unit or ward, including sensor adherence, signal quality, missing or uninterpretable data, patient mobility and patient experience, have not been sufficiently studied.
Main objective: To assess the feasibility of postoperative INVOS tissue oximetry monitoring after free-flap reconstructive surgery.
Secondary objectives:
To descriptively evaluate clinical outcomes after free-flap reconstructive surgery, including flap-at-risk episodes, surgical re-exploration, flap failure, postoperative complications and patient-reported experience with INVOS™ monitoring.
Study design: Multi-center, observational cohort study Study population: adult patients scheduled for elective free flap reconstructive surgery Main study endpoints: Successful maintenance of continuous monitoring, proportion of missing or uninterpretable StO₂ data, and sensor displacement or detachment requiring inter-vention or replacement. Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Participants will receive perioperative surgical and anesthetic care as usual. At the end of surgery, INVOStm stickers will be placed at the free-flap by the surgeon. In addition, an INVOStm sticker will be placed at the femoral muscle which will serve as so-matic reference. Postoperative flap controls will follow routine protocol; no decisions will be made based on INVOStm readings.
Leiden University Medical Center is the lead sponsor of 333 studies on the registry; 109 are open to participants now.
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Patients scheduled for elective free flap reconstructive surgery
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Adult patients scheduled for elective free flap reconstructive surgery.
Procedure: Elective free flap surgery · Device: INVOS monitoring
Reconstruction using deep inferior epigastric perforator (DIEP) flap. Participants will receive standard surgical, anaesthetic and postoperative care according to local practice.
The INVOS system (In Vivo Optical Spectroscopy). INVOS™ sensors will be applied to the free flap and to a femoral reference site for postoperative tissue oximetry monitoring. The INVOS™ monitor readings will not be visible to caregivers, alarms will be muted, and INVOS™ measurements will not be used for clinical decision-making during this study. Clinical assessment and Doppler monitoring will remain leading for all decisions regarding flap viability.
Proportion successfully maintained monitor
The proportion of patients (%) in whom continuous tissue oximetry monitoring was successfully maintained for the entire postoperative period.
Time frame: From day of surgery (day 0) until day 3 postoperative
Surgical re-exploration
Surgical re-exploration performed because of suspected vascular compromise of the free flap. Yes/no.
Time frame: From day of surgery (day 0) until day 3 postoperative
Flap failure
Flap failure. Yes/no.
Time frame: From day of surgery (day 0) until day 3 postoperative
Flap risk score
0= no risk parameters present 6= all risk parameters present. Risk parameters are: color, consistency, capillary refill, temperature, doppler signal, clinical suspiscion. Parameters score 0 if the parameter is clinically judged to be normal/optimal and 1 if parameter is clinically judged to be suboptimal
Time frame: From day of surgery (day 0) until day 3 posteroperative
Postoperative complications
According to Clavien-Dindo scale Grade I Any deviation from the normal postoperative course without the need for pharmacological treatment or surgical, endoscopic and radiological interventions. Allowed therapeutic regimens are: drugs as antiemetics, antipyretics, analgetics, diuretics and electrolytes and physiotherapy. This grade also includes wound infections opened at the bedside. Grade II Requiring pharmacological treatment with drugs other than such allowed for grade I complications. Blood transfusionsand total parenteral nutritionare also included. Grade III Requiring surgical, endoscopic or radiological intervention * IIIa Intervention not under general anesthesia * IIIb Intervention under general anesthesia Grade IV Life-threatening complication (including CNS complications)\* requiring IC/ICU-management * IVa single organ dysfunction (including dialysis) * IVb multiorgandysfunction Grade V Death of a patient
Time frame: From day of surgery (day 0) until day 3 posteroperative
INVOS risk triggers: absolute drop of StO₂
Number of absolute drops of StO₂ \< 60%.
Time frame: From start of INVOS measurements (day 0) until day 3 postoperative
INVOS risk triggers: relative drop StO₂
Number of relative drops of StO₂ ≥20% decrease from baseline sustained ≥30 minutes.
Time frame: From start of INVOS measurements (day 0) until day 3 postoperative
INVOS risk triggers: flap-to-reference ratio
Flap-to-reference ratio of \<0.75. Yes/no
Time frame: From start of INVOS measurements (day 0) until day 3 postoperative
Incidence sensor displacement or detachment
The incidence of mechanical sensor displacement or complete detachment requiring clinical intervention or sensor replacement within the first 48 hours postoperatively.
Time frame: From day of surgery (day 0) until day 3 posteroperative
Cumulative duration missing StO2 data
The cumulative duration of missing or uninterpretable tissue oxygen saturation (StO₂) data due to sensor detachment, signal artifacts, or hardware failure, expressed as a percentage (%) of the total monitoring time.
Time frame: From start INVOS measurement (day 0) until day 3 postoperative
Reasons of device failure
Reasons of device failure. For each case, the reason why the device failed or did not function as intended (e.g. technical malfunction, battery issue, software error, or user error) is recorded as free text. This is a qualitative outcome measure with no unit. Responses will be described and categorised afterwards to identify the most frequent causes of failure.
Time frame: From day of surgery (day 0) until day 3 postoperative
Patient satisfaction
At the end of the monitoring period (72h) the patient will be asked to rate their experience with the INVOS monitoring by answering the following questions: * Express your satisfaction with INVOS monitoring (0-5; 0 very dissatisfied - 5 very satisfied) * Did INVOS interfere with mobility? (0-5; 0 not at all - 5 very much) * Did INVOS interfere with sleep? (0-5; 0 not at all - 5 very much) * Did INVOS monitoring make you feel more reassured? (0-5; 0 not at all - 5 very much): * Would you be willing to receive INVOS monitoring for potential future postoperative monitoring? (yes/maybe/no) * Would you recommend INVOS monitoring for postoperative monitoring to other patients? (yes/maybe/no)
Time frame: At day 3 postoperative
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Plan to share: Undecided
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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