A question about ropivacaine for unilateral spinal anesthesia: hypobaric solution

Dear Editor,

I am a doctor from department of anesthesiology, Shanghai Sixth People's hospital, Shanghai Jiao Tong University, Shanghai, China. I have many interests in ropivacaine for unilateral spinal anesthesia: hypobaric solution. So I have read your literature titled "Ropivacaine for unilateral spinal anesthesia; hyperbaric or hypobaric?" ¹ In this article, it was mentioned that "group Hypo (n = 30) received 11.25 mg of ropivacaine (7.5 mg mL^-1) + 2 mL of distilled water (density at room temperature was 0.997)". Because ropivacaine (7.5 mg mL^-1) is isobaric solution and density of distilled water is 1, why the density of mixed solution was 0.997? I made these mixed solution to survey the density, and the density was 1.006. Please tell me the answer, and tell me your way to make the mixed solution and survey the density. Thank you very much.

Reference

• ¹
  Cantürk M, Kılcı O, Ornek D, et al. Ropivacaine for unilateral spinal anesthesia; hyperbaric or hypobaric?. Rev Bras Anestesiol. 2012;62:298-311.

Publication Dates

• Publication in this collection
  Aug 2015