| Abstrakt: |
During minimally invasive cardiac surgery (MICS), cardiopulmonary bypass (CPB) is performed with femoral cannulation, eliminating the need for sternotomy and the accompanying risks for infections and bleeding. The increased risk of ischemic injury to the lower extremity makes close monitoring of limb perfusion desirable. In current clinical practice, near-infrared spectroscopy (NIRS) is used to measure changes in tissue oxygenation (StO2) in the cannulated leg. In case of impaired perfusion, an additional distal cannula providing antegrade blood flow is inserted. However, interpatient variability and sensitivity to ambient light and skin colour make it hard to define general cut-off values for StO2. With a small dynamic light scattering (DLS) skin sensor microcirculatory perfusion can be monitored and from the obtained speckle pattern total blood flow (TBF) can be calculated. This study aimed to determine the ability of DLS to detect changes in limb perfusion by monitoring TBF during MICS. Adult patients (ASA 2-4) undergoing MICS, requiring CPB, were eligible for inclusion in this single-centre observational study. Both DLS (Elfi-Tech Ltd., Israel) and NIRS (ForeSight Elite, Edwards Lifesciences Crop., USA) sensors were placed at each lower leg to measure TBF and StO2 continuously during surgery. DLS parameters were blinded for operating room personnel and an additional distal antegrade cannula was inserted according to regular clinical practice in case of persistent StO2 depression (StO2 decline of 20% from the baseline or below 50%) after cannulation. TBF and StO2 were compared between the legs in 5-minute windows surrounding flow-alternating moments (before cannulation, after start and end of CPB, after cannula removal and, when applicable, after additional cannula insertion). 35 patients (24 (68.6 %) male, age 70.0 [58.5-74.5] years, weight 80 [72-91] kg) were included in the study. Five patients received an additional distal antegrade cannula because of low StO2 values. Before cannulation, StO2 and TBF baseline levels in all patients did not differ significantly between both legs. Five minutes after starting CPB, in all patients both StO2 and TBF were significantly lower in the cannulated leg (57 [49-65] % and 4124 [3142-4739] arbitrary units (AU)) when compared to the non-cannulated leg (63 [52-69] % and 4574 [4114-5502] AU, p=0.01 and p<0.01). In the patients needing additional antegrade cannulation, both StO2 and TBF decreased in the cannulated leg at the start of CPB (Figure 1). In the 5 minutes after additional cannula insertion, TBF recovered while StO2 decreased further, StO2 increased in the window 5 to 10 minutes after insertion. After cannula removal no significant differences between the legs were observed in all patients. During MICS procedures, DLS showed a significant decrease in TBF in the cannulated leg, which recovered after removal of the cannula. In patients needing additional antegrade cannulation, TBF recovered earlier than StO2 after the additional cannulation. DLS is a promising technology for monitoring intra-operative limb perfusion. [ABSTRACT FROM AUTHOR] |
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