Remember in the heat and pressure of a pediatric intubation (if you don't have your Pediatic Qwic Card handy) you can estimate what size blade to use very quickly and successfully by using facial landmarks!!

• Distance from the upper incisor teeth to the angle of the jaw seems to be an excellent clinical landmark for laryngoscope blade length selection for pediatric intubations under 8 years of age 
• Take the blade (excluding the handle insertion block) and place at the upper midline incisor teeth and if the tip is located within 1 cm proximal or distal to the angle of the mandible, oral tracheal intubations are more consistently accomplished on the first attempt!!!     90% on first attempt with correct size blade v. 57% on first attempt if blade too short

And remember to start with a straight blade (Miller, Wisconsin, Guedel, Wis-Hipple etc.) for your patients under 2 years of age because:

• these blades make controlling the tounge and epiglottis easier than curved blades at this age
• and they have a smaller flange profile in the oropharynx so visualization of the vocal cords is clearer

References

Pediatric Emergency Care. 22(4):226-229, April 2006.
Mellick, Larry B. MS, MD, FAAP, FACEP ; Edholm, Thomas MD, FACEP ; Corbett, Stephen W. MD, PhD, FACEP