Background and Rationale: Size of spinal needle may be a factor which influences the success rate of spinal anesthesia.
Objectives: To compare learning curves of using 25G and 27G quincke spinal needle for spinal anesthesia.
Setting: Department of Anesthesiology, Faculty of Medicine, Chulalongkorn University and King Chulalongkorn Memorial Hospital.
Design: Prospective randomized control trial.
Material and Method: Ten new first year anesthesia residents were randomized to 2 groups: Group I (n = 5) used 25G Quincke spinal needle, Group II (n = 5) used 27G Quincke spinal needle to perform 200 consecutive cases of spinal anesthesia. Number of success and failure was recorded by each individual resident anonymously. The learning curves of plotted by cumulative sum of success rate revealed an initial rapid improvement of success during the first 20 cases in both groups. The overall success rate of group I was 84% (95CI, 66.5- 100) and group II was 87% (95%CI, 61.5-100); p = 0.89. The widest difference between the 2 learning curves at 20 attempts intervals was at the twentieth attempts with a success rate of 76.0% VS 65.0% in group I and group II respectively; p = 0.54.
Conclusion: The learning curves of spinal anesthesia using 25G and 27G Quincke spinal needle showed rapid improvement of success rate at the first 20 spinal block and high overall success rate with no significant difference between the groups.

Keywords: Anesthesia, Spinal anesthesia, Learning curve, Training, Needle size