Fig. 2.

The ED₅₀ of intrathecal 0.5% hypobaric ropivacaine USpA in geriatric patients undergoing hip replacement surgery, as determined using the Dixon and the Massey up-down sequential method was 6.43 mg (95% CI: 6.47–6.39 mg). In this group 12 patients needed an epidural supplement of 2% lidocaine to maintain a T10 sensory level, and 4 patients exhibited nausea and vomiting after the administration of 2% lidocaine into the epidural space. Individual responses to intrathecal hypobaric ropivacaine at specific doses. The red squares represent an ineffective response to the corresponding dose of intrathecal hypobaric ropivacaine for spinal anesthesia. The blue diamonds represent an effective response to the corresponding dose of intrathecal hypobaric ropivacaine for spinal anesthesia