Incidence, predictors and vascular sequelae of distal limb ischemia in minimally invasive cardiac surgery with femoral artery cannulation: an observational cohort study

Fig. 1. Representative image of a regional Oxygen Saturation (rSO2) measurement in time (minutes) with Near-Infrared Spectroscopy (NIRS). During the NIRS-measurement, five main events were captured: baseline (B) measurement 5 min before the occurrence of event 1; Event 1 (E1) = insertion of the femoral artery cannula; Event 2 (E2) = onset of the cardiopulmonary bypass; Event 3 (E3) = offset of the cardiopulmonary bypass; Event 4 (E4) = removal of the femoral artery cannula. These events are captured simultaneously for both limbs, whereby the red line corresponds to the NIRS-measurement of the cannulated limb, and the green line corresponds to the NIRS-measurement of the non-cannulated limb

Fig. 2. Consort flowchart. A total of 497 patients were screened for eligibility, whereof 149 were not eligible and 68 were excluded due to various reasons described above. After the removal of non-eligible and excluded patients, the estimated sample size of 280 was reached. Of all 280 patients, 44 patients could not be contacted for telephone follow-up after six months, rendering 236 patients for the follow-up statistical analysis. Of all 236 patients, 63 patients developed distal limb ischemia in the cannulated limb (defined as s a ≥ 15% difference in regional Oxygen Saturation (rSO2) lasting ≥ four consecutive minutes between the cannulated and non-cannulated limb) and 173 patients who did not develop distal limb ischemia in the cannulated limb. Among those 173 patients, three patients required additional peripheral vascular surgery within the six-month follow-up period

Fig. 3. Comparison of the mean rSO2-values in all 75 patients who experienced a rSO2-drop ≥ 15% lasting ≥ four consecutive minutes in the cannulated limb compared to the non-cannulated limb during MICS. A parametric independent samples T-test was used for the comparison of baseline and all four events between the cannulated and non-cannulated limb (E1 = insertion of the femoral arterial cannula; E2 = onset of the CPB; E3 = offset of the CPB; 4 = removal of the femoral arterial cannula. Statistically significant differences are indicated with (*)

Fig. 4. Comparison of the mean rSO2-values in all 205 patients who did not experienced a rSO2-drop ≥ 15% lasting ≥ four consecutive minutes in the cannulated limb compared to the non-cannulated limb during MICS. A parametric independent samples T-test was used for the comparison of baseline and all four events (E1 = insertion of the femoral arterial cannula; E2 = onset of the CPB; E3 = offset of the CPB; 4 = removal of the femoral arterial cannula. Statistically significant differences are indicated with (*)