Lower Limb Tissue Oxygenation Using Near-infrared Spectroscopy During Hallux Valgus Operation

In acute lower limb ischemia the main goal of the treatment is to restore the blood before irreversible damage to the soft tissues of the limb. Delays in identifying acute lower limb ischemia may lead to limb loss or lead to the loss of the patient. Situations in which the patient is unable to express symptoms of the acute lower limb ischemia, such as during general anesthesia, in intensive care, or immediately after vascular surgery, are challenging for medical staff to identify. A reliable, easy-to-use and non-invasive monitoring method is not yet in every day use. The aim of this study is to demonstrate that Near InfraRed Spectroscopy (NIRS) monitoring is such a monitoring method. Tourniquet induced ischemia is often used in hallux valgus surgery because it offers a bloodless view of the anatomical structures. In our study we will measure the soft tissue perfusion (rSO2) of the lower limbs during the whole operation. The sensors based on near-infrared spectroscopy will be located to the tibial surface and will record the normal state before the start of the tourniquet, during the tourniquet and also in the recovery phase. The hypothesis is that rSO2 decreases linearly as a function of time from the beginning of the tourniquet induced ischemia and the recovery time depends on the duration of the tourniquet. In our study the patients will be operated under a spinal anesthesia. We also hypothesise that rSO2 increases due to the induction of the spinal anesthesia. Our goal is to define the percentual decline of rSO2 that is significant for lower limb ischemia and also its time response to induction of ischemia.