Fig. 3. Time course evolution of venous ropivacaine and α-1-acid glycoprotein concentrations. h = time in hours after application of first interscalene block. Arrow 1 shows the application of right interscalene block; arrow 2 shows the application of left interscalene block; arrow 3 shows the start of continuous perfusion of 0.2% ropivacaine with 7 ml/h right side, 7 ml/h left side (total 28 mg/h) via interscalene catheter.