Detecting Tissue Ischemia in Reconstruction Flaps by a Novel CO2 Biosensor (DIMENSION-study); An Open, Prospective, Intervention Study

This is an open, prospective, interventional, single-center clinical investigation designed to examine the feasibility and safety of the IscAlert™ device in patients scheduled for reconstructive flap surgery. 56 will be enrolled to undergo the procedures using a total of 350 devices depending on the injuries. IscAlert is 0.8 mm in diameter and in vitro testing, shows stable and accurate measurements of pCO2. More than 200 animal experiments have been done with the sensor. The experiments have shown that the sensor detects ischemia (Increased CO2-measurements) in real time in the following organs and tissues: Brain, heart, liver, kidneys, pancreas, intestines, musculature and subcutaneous tissue. Sensitivity and specificity are close to 100%. The sensors are inserted into tissue by a split needle technique. The split needle is the size of a 3-gauge peripheral venous catheter. In animal studies, no complications have been detected when using the sensor. The IscAlert sensors are connected to an electronics unit that is fixed to the skin with an adhesive plaster or glue outside the sterile area. The electrical signals are redirected to a PC approved for clinical use which continuously records tissue pressures of CO2. IscAlert is inserted into normal muscle and/or subcutaneous tissue distal on the reconstructed flap to be operated at the end of surgery. The insertion is far away from the operating field. The insertion is done under sterile conditions in accordance with standard sterility criteria at the hospital. No pain during insertion will occur because of insertion is performed during general anesthesia. Also, the insertion can be compared to an intramuscular injection. Postoperatively, the IscAlert sensor will continuously monitoring tissue CO2 and temperature. If ischemia occur, for examples caused by a thrombus, an increase in tissue CO2 and a lower temperature will evolve. This will be detected by the sensor which will alarm the investigators. This will lead to assessment of the reconstructed flap and if restricted blood flow is diagnosed, a reoperation or other intervention will be performed. The IscAlert will be removed from the patient before the patient is discharged from the hospital or a maximum of 10 days (the event that occurs first). Approximately 360 devices are planned to be used in this clinical study. One of the sensors will be used as a control inserted into neighboring tissue.

The primary objective is to compare CO2-levels in the reconstructed flap in individuals who has undergone reconstructed flap surgery and investigate if CO2-level is different in patient diagnosed with obstructed blood flow vs. patients with sufficient blood flow in the reconstructed flap.

Our hypotheses are:

1. The IscAlert™ device will be able to detect the presence of ischemia in the reconstructed flap by increased pCO2 levels and decrease in tissue temperature, measured by IscAlert™.
2. By using the IscAlert™ device monitoring ischemic events, an early treatment for ischemia could lead to higher incidence of reconstructed flap survival rates, and less revision surgery caused by thrombosis.
3. No clinically significant bleeding or infection will occur using IscAlert™ in this clinical study.