Medical brain notes 7

  Airway management We have made remarkable advances in techniques to secure a patent airway, and have developed new equipment and methods to monitor breathing. Yet, respiratory complications remain the leading cause of anesthesia-related deaths, with the majority related to failure to obtain control of the airway. Here we will discuss: (i) how to evaluate the airway of a patient; (ii) the impact of the planned procedure designed to protect the airway; and (iii) how to manage the airway. First, let us explain why all this matters. Any time we anesthetize a patient, we must be prepared to take over his ven-tilation at a moment’s (or less) notice because anesthesia can interfere with the patient’s ventilation in so many ways. We may have weakened, with muscle relax-ants, the patient’s ability to breathe. We may have put him into a deep coma, anesthetizing his respiratory center and relaxing the muscles in his mouth and pharynx so that his air passage is obstructed. We might have supp...

  Examination of the airway Direct laryngoscopy (see below) requires neck flexibility, a mouth that can open widely, and no excessive pharyngeal tissue or a large tongue to get in the way. These features cannot be measured directly, but the following steps help us to assess problems that might arise during laryngoscopy: ·             Assess mouth opening: inter-incisor distance should exceed 4 cm in an adult. ·             Determine the mentum–hyoid ( > 4 cm) or thyromental ( > 7 cm) distance: shorter distances suggest an anterior or very cephalad larynx, which would be difficult to visualize by laryngoscopy. ·             Investigate the posterior pharynx (modified Mallampati Classification) by hav-ing the sitting patient fully extend his neck, maximally open his mouth, and stick out his tongue with or without ph...

Mask–ventilation Simple as it seems, the ability to mask–ventilate a patient is  the  essential airway management technique that needs to be practised and learned by every health-care provider. Most important is the patient’s head position: Do not let the patient’s neck flex and thus potentially occlude the airway, which makes mask–ventilation difficult to impossible. Proper mask technique includes the following: (i)         Select an appropriate size mask to fit over the patient’s nose and mouth and provide an airtight seal without pressure on the eyes.   (ii)      Place the head in sniffing position (occiput elevated, neck extended) or directly supine, with the neck neutral to slightly extended.   (iii)    Positioning yourself at the patient’s head, apply the mask to the face with a pincer grip by thumb and index finger of the left hand. Place the third finger on the mentum and pull the chin upward. T...

  Laryngeal mask airway Developed in the 1980s, the laryngeal mask airway (LMA; Fig.  2.3 ) has supplanted tracheal intubation for many general anesthetics. The device is basically the progeny of a facemask mated with an endotracheal tube, allowing positioning of the mask just above the glottic opening. While we have available a version intended to protect the airway from gastric aspiration (LMA Proseal®), none can guarantee it. The major advantages of the LMA over tracheal intubation are the lower level of skill required for placement, decreased airway trauma (especially of the vocal cords), and reduced stimulation such that lightly anesthetized, sponta-neously breathing patients can tolerate the device. Also, the properly positioned LMA places the laryngeal inlet in clear view for a fiberoptic scope, making tra-cheal intubation through the device a popular technique in the management of the difficult airway. To place the LMA, we induce anesthesia without paralysis, then 1. ...

  Endotracheal intubation Oral intubation by direct laryngoscopy We prefer to intubate the trachea when we need to have more control of the patient’s airway, ventilate his lungs, and protect against aspiration of gastric con-tents. The use of a cuffed tracheal tube (Fig.  2.4 ) reduces the risk of aspiration in the adult. 1  Our first step is to confirm all necessary equipment is at hand: ·             a properly checked anesthesia machine, or a self-inflating bag or Mapleson system with source of compressed oxygen, and a tight fitting mask; ·             endotracheal tubes (ETT) of appropriate sizes (see Table  2.2 ). Generally we like to have an extra tube  1 / 2  size smaller than that anticipated . . . just in case; ·             a stylet that fits in the ETT – sometimes required to stiffen ...

  Can’t intubate situations Here the hearts (of the caregivers) begin to pound . . . when the vocal cords cannot be visualized. If this problem arises after adequate pre-oxygenation, you will have won valuable time before serious hypoxemia ensues. The first thing we try is to change the patient’s position, the laryngoscope blade, and/or the laryngoscopist. If this does not help (and the patient is still apneic), then another technique must be attempted (Table  2.3 ). The selection of rescue technique depends on the situation, experience of the physician, availability of equipment, and whether mask–ventilation is possible. For example, “can’t intubate, can’t ventilate” scenarios necessitate rapid inter-vention, and thus, fiberoptic intubation would not be a likely choice for an inex-perienced physician; placement of an LMA is much more likely to be successful. Whereas in a “can’t intubate,  can  ventilate” scenario, we may be able to mask– ventilate the patient’s lung...

  Awake fiberoptic intubation Sometimes an indirect visualization technique becomes necessary, either dur-ing airway rescue, or when a pre-operative examination suggests a likelihood of  difficult intubation.   In such cases, perhaps the most definitive technique is to secure the airway while the patient is still awake and breathing spontaneously. Awake fiberoptic intubation requires topical anesthesia for the patient’s com-fort, as well as to blunt the gag reflex that would prevent successful intubation of the trachea. All too frequently, secretions will smear the optics of the scope: an anti-sialogogue can be helpful. Several nerves are involved in the sensation of the upper airway (Fig.  2.8 ). It is not much of a mnemonic, but try to remember a variant to TGIF (Thank God it’s Friday) namely  TGIR : “Thank God it’s recurrent.” It’s lame, but perhaps just lame enough to be memorable! All but the first of these make up the gag reflex. We anesthetize the posteri...

  Airway management plan For many operative procedures requiring general anesthesia, any of these tech-niques (mask, LMA, ETT) may be appropriate, but there are times to prefer one  over another.   We take into account the planned procedure and the patient’s status (Table  2.4 ). An emergency laparoscopic appendectomy should probably be performed with an ETT because of the high risk of aspiration (full stomach and increased intra-abdominal pressure from laparoscopy), while a professional singer undergoing a minor elective procedure might be better served with a mask or LMA. A word about the patient with a potentially unstable cervical spine. Many times, trauma patients arrive from the Emergency Department without a “cleared” cer-vical spine. Though radiographs can identify fractures and displacement, they fail to reveal torn or damaged ligaments, all pointing to instability of the cervical spine. If the patient is intoxicated or comatose and thus can give neither a u...