The number of needle puncture to PV during the procedure 16 The number of needle puncture n% 1 pass 15 31.3 2 passes 22 45.8 3 - 5 passes 11 22.9 Average 2.0 ± 0.9 Comment: The average passes of PV puncture was 2.0 ± 0.9, the lowest was 1 pass and the highest was 5 passes.