C-MAC (Karl Storz) video laryngoscopy, especially when using the D-blade configuration, is a promising way to minimize head and neck movement during intubation, a recent study concluded.
In patients with cervical spine injuries in particular, the extra time and effort needed compared with conventional Macintosh laryngoscopy is clinically unimportant, the researchers said.
“Head and neck movement during conventional direct laryngoscopy may compound already existing spine injury,” said Singh Rohini, MD, of the University of New Delhi. Dr. Rohini presented her research at the 2016 annual meeting of the Society for Airway Management.
“Since there is no defined safe limit for these patients, we want to keep movement as close to zero as possible,” she said. “Many maneuvers and devices have been compared, but no study has compared the overall spine movement while using these three blades [tested in the study].”
The study randomized 105 patients into three groups of 35 each who underwent conventional laryngoscopy, C-MAC video laryngoscopy and D-blade laryngoscopy. The prospective randomized, crossover study included patients aged 18 to 60 years, without obvious airway difficulty.
The patients went without manual stabilization, cricoid pressure or immobilizing devices, and the operator made an effort to minimize movement in all cases. Dr. Rohini and her team measured global head and neck movement as well as the time to reach the interarytenoid fold and 50% of glottis opening with an angle finder attached to goggles.
“We saw significantly less movement with the C-MAC than the conventional MAC, which can be attributed to the steep 40-degree curve as compared to the 18-degree [curve] in the C-MAC,” she said. “It looks promising if we can keep the movement down.”
During the study, the average conventional Macintosh movement to reach the interarytenoid fold was 15 degrees, compared with 11 degrees with the C-MAC and six degrees with the D-blade. To reach 50% of glottis opening, conventional Macintosh movement was 20 degrees, and 15 degrees with the C-MAC and nine degrees with the D-blade.
The time to view did not vary significantly among the blades. For the interarytenoid fold, the conventional Macintosh required about 12 seconds, and 12 seconds for the C-MAC and 14.5 for the D-blade. For 50% of glottis opening, the conventional Macintosh took 17.5 seconds, and 18 seconds for the C-MAC and 22 seconds for the D-blade. For trauma patients, the suggested maximum time for intubation is 30 seconds, according to the 2008 International Trauma Life Support (ITLS) manual.
However, the D-blade was rated more difficult to use than the other two blades because of its higher angulation. “It was difficult in a few cases to pass the tube, and that’s the next area we plan to study,” Dr. Rohini said.
This study is clinically relevant and brings up several important points about head and neck movement during spinal procedures, said Matteo Parotto, MD, of the University of Toronto, who moderated poster presentations at the meeting. “Does it matter how hard it is to pass the tube?” he asked. “Do we need to worry about range of angulation?”
The study points to the importance of anesthesiologists knowing which blades are available at their particular institutions and how to use them. “If certain blades are not available, what should be available?” he said.
Besides head and neck movement, anesthesiologists should consider the additional damage that can be caused to trauma patients. For example, fluoroscopic studies show that even if the head is still, placing a blade can do harm, noted Arpan Mehta, MD, consultant anesthetist at University College London. “The key to remember with trauma patients is that they could have multiple other injuries,” he said. “In those moments, you have to do the best you can with what you have.”