When inducing general anesthesia, patients can no longer protect their airway, provide effective respiratory effort, or protect themselves from injury. For these reason, ideal positioning for general anesthesia is extremely important and can help prevent potential injuries and devastating consequences.
Positioning for induction of general anesthesia
• When inducing general anesthesia, the patient is no longer able to protect their airway or provide an effective respiratory effort. The goal of care is to provide adequate ventilation and oxygenation during general anesthesia. Patients are evaluated in the preoperative period for the signs of difficult mask ventilation and/or intubation. Positioning is especially important in morbidly obese patients. The body habitus of these patients can make them difficult to ventilate and intubate.
• Ideal masking and intubating position is called the "sniffing" position. This is obtained by lifting the patients chin upward (when supine) so as to look, from a profile view, that the patient is sniffing the air. Doing this in addition with lifting the mandible forward (to remove the tongue from the oropharynx) facilitates easiest mask ventilation.
• In obese patients, it is often difficult to mask ventilate and intubate owing to their body habitus. When mask ventilating, even with perfect technique, there is often excess tissue on the chest wall, which will make it difficult to properly ventilate at low pressures, so as not to inflate the stomach with air during attempted ventilation. Often, obese patients are ramped at a 30° angle to help improve the mask ventilation and intubation.
• When attempting intubation, the goal of positioning is to align the tragus of the ear with the level of the sternum. This improves intubating conditions and creates direct visualization of the vocal cords when performing direct laryngoscopy.
Positioning during general anesthesia
• When a patient is under general anesthesia, he or she has lost all protective reflexes, so providers must be very careful to position the patient. The primary concerns of positioning are ocular injuries, peripheral nerve injuries, musculoskeletal injuries, and skin injuries.
• Initially after induction of anesthesia, eyelids should be gently taped down in a closed position. This helps prevent corneal injury by accidental scratching of the cornea. Another ocular injury that can be made less likely during surgical positioning is to prevent ocular venous congestion, which can cause perioperative vision loss. This is often seen in prone patient who develops increased ocular pressure either through mechanical force on the eye or increased venous congestion.
Another concern during general anesthesia is peripheral nerve injuries. The most common peripheral nerve injuries are ulnar nerve, common peroneal nerve, and brachial plexus injuries. These can be prevented with appropriate positioning, padding, and vigilance during general anesthesia. The arms should be at less than 90° in relation to the body. Gel/foam padding should be used for superficial nerves (eg, ulnar nerve in the ulnar groove-lateral epicondyle of elbow). Prevent positioning up against hard objects (eg, metal, plastic). Prevent hyperextension/flexion of the spine or neck. Exercise vigilance by checking positioning every 15 minutes during general anesthesia.