PT - JOURNAL ARTICLE AU - Zhu, Change AU - Zhang, Saiji TI - Response to the letter from Dr Yifeng Ren <em>et al</em> AID - 10.1136/rapm-2019-101021 DP - 2019 Dec 04 TA - Regional Anesthesia &amp; Pain Medicine PG - rapm-2019-101021 4099 - http://rapm.bmj.com/content/early/2019/12/04/rapm-2019-101021.short 4100 - http://rapm.bmj.com/content/early/2019/12/04/rapm-2019-101021.full