Sizes of IV cannula: How to Remember? December 31, 2018 PRITHWIRAJ MAITI Leave a comment 4.8 (40) MCQs: IV cannula of choice in trauma: 18G (Green) – According to latest ATLS Blue cannula: 22G (AIIMS question) Maximum flow rate: Orange. How useful was this post? Click on a star to rate it! Submit Rating Average rating 4.8 / 5. Vote count: 40 No votes so far! Be the first to rate this post.