Fig. 3From: Analgesic efficacy of postoperative bilateral, ultrasound-guided, posterior transversus abdominis plane block for laparoscopic colorectal cancer surgery: a randomized, prospective, controlled studyKaplan-Meier curve depicting time to first tramadol requirement during postoperative 24-h follow-up among two groups. Note: Group TAP = transversus abdominis plane block, P<0.001Back to article page