Height-based dosing algorithm of bupivacaine in spinal anaesthesia for decreasing maternal hypotension in caesarean section without prophylactic fluid preloading and vasopressors: study protocol for a randomised controlled non-inferiority trial.

Introduction Effectively preventing or treating spinal-induced maternal hypotension is considered to be the Holy Grail of obstetric anaesthesia. Prophylactic fluid preloading and vasopressors decrease hypotension but may aggravate heart load, induce fetal acidosis or maternal bradycardia. Using low-dose local anaesthetic decreases hypotension but may cause insufficient anaesthesia. Whether there is a height-based dosing algorithm of local anaesthetic in spinal anaesthesia for caesarean section that can provide sufficient anaesthesia with less hypotension without prophylactic fluid preloading and vasopressors is unclear. This study was designed to investigate a height-based dosing algorithm of bupivacaine in spinal anaesthesia for caesarean section. Methods and analysis This single-centre, doubleblinded, prospective, non-inferiority, randomised controlled trial will include 264 parturients (between 18 and 45 years of age) who are scheduled for caesarean section. All participants will not receive prophylactic fluid preloading. The participants will be randomly divided into two groups: the test group or conventional group. For parturients in the test group, 0.5% isobaric bupivacaine (1.15-1.70 mL) will be injected into the subarachnoid space without prophylactic vasopressors. The bupivacaine dose depends on the height of subjects. For parturients in the conventional group, 0.5% bupivacaine (1.8 mL) will be injected into the subarachnoid space along with prophylactic vasopressors. The primary outcome is the incidence of maternal hypotension. The secondary outcomes include the failure rate of spinal anaesthesia, level of sensory block, degree of motor block, other complications in parturients, time of operation, neonatal outcome and quality of anaesthesia. Ethics and dissemination This study was approved by the Ethics Committee of Shenzhen People's Hospital of Jinan University (Permit No. SZY-00251, chairperson Xiaofang Yu) on 8 February 2018The study results will be disseminated through peer-reviewed journals, professional societies and meetings.