Apparatus and equipment
The Miller laryngoscope is the most widely used straight laryngoscopic blade for a throat examination. Robert A. Miller introduced the Miller blade in 1941 when endotracheal intubation was becoming commonplace. His design overcame the problems of the then-common laryngoscope blades. ” Miller Laryngoscopes are longer, rounded at the bottom and smaller at the back, and have an additional curvature starting two centimeters from the tip.
These blades are usually used in infants because the epiglottis is relatively larger than the palate, making it easier to see the palate. Miller knife laryngoscopy is performed by placing the blade behind the epiglottis to expose the palate and vocal folds.
Miller knives may be more useful than MacIntosh knives for those who have a short, thick neck, a higher position of the larynx in the neck, a large tongue or are obese. “Miller knives are available in sizes 0 to 5.
Preparation for laryngoscopy
Large animals should be fasted for 8-12 hours before anesthesia to reduce the risk of vomiting during induction of anesthesia or recovery after anesthesia. For smaller animals, this step is not necessary. However, guinea pigs may retain food in the pharynx. If this phenomenon is observed in a large number of guinea pigs, it may be sufficient not to eat for 3-4 hours before anesthesia. Before anesthesia, examinations should be performed to assess the health status and age of the subject.
Laryngoscopy can be performed on lightly anesthetized subjects, but it is recommended that this method be used only after acquiring the technical skills. Before intubation, the subject should be given oxygen for about 2 minutes to delay hypoxia, which can occur due to inadvertent laryngeal obstruction. Although laryngoscopy can be performed as an emergency diagnostic measure before surgical correction, it is most effective in stable subjects.
Performing laryngoscopy with the Miller knife
Have the subject lie on his or her back.
Hold the laryngoscope in the dominant hand.
Extend the subject’s tongue forward and to the left.
Slowly insert the blade into the right side of the subject’s mouth.
Push the blade inward and toward the midline, in the direction of the base of the tongue.
Place the tip of the blade under the epiglottis.
Push into the tail and upward, holding the handle at a 45-degree angle.
Lift the handle until you can see the vocal cords.
Perform intubation with the vocal cords directly visible.
Remove the blade while firmly holding the endotracheal tube.
Remove the blade from the handle and squeeze the bulb, then rinse the blade under cold running water to remove visible debris. Thoroughly clean the blades with a soft brush after soaking them in enzymatic cleaner. Rinse again under cold running water to remove any detergent residue. Dry the blades with a clean, lint-free cloth.
Skeletal and soft tissue factors in subjects may affect the visibility of the larynx. Improper blade use can cause soft tissue injury and anterior tooth damage. When choosing blade size, take the subject’s weight into account. Always check the blades and handles of laryngoscopes after cleaning, disinfection and sterilization and before use. Since the blade handles also act as counterweights, it is necessary to choose the right size handle for the size of blades used.