Page 570 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

390 PART 4: Pulmonary Disorders

is more properly used as a rescue device than an approach of first choice
in any ICU patient who may have a full stomach. In the settings of upper
airway bleeding or copious secretions and failed rigid laryngoscopy, it is
reasonable to attempt to use an intubating LMA.
■ THE DIFFICULT AIRWAY

The difficult airway is far more commonly encountered in the ICU and
emergency room than in the operating room. Under these emergent
conditions of airway management, multiple attempts at laryngoscopy are
common (25%-35%), and between 0.5% and 2% of patients require a sur-
gical airway. Copious secretions and inadequate positioning are common
obstacles encountered in the ICU, but not in the operating room. The
American Society of Anesthesiologists’ Difficult Airway Algorithm
outlines the options available to practitioners faced with a difficult
airway (Fig. 45-3). Choices for proceeding include ventilate with the
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bag and mask, summon help in the form of another operator, reposition,
FIGURE 45-1. Ovassapian fiberoptic intubating airway. It keeps the tongue forward and attempt laryngoscopy with a different blade, and apply other techniques
the fiberscope midline, provides open air space in the hypopharynx, protects the fiberscope as appropriate. Ideally, a competent assistant will ventilate the patient
from the patient’s bite, and is removed from the mouth without disconnecting the endotra- with an Ambu bag as the operator prepares for their next attempt to
cheal tube adapter. secure the airway. If the patient can be adequately oxygenated with mask
ventilation, then the operator has a variety of options for how to proceed.
as it is withdrawn from the trachea. The distance from the carina to the Changing the operator or laryngoscope blade will sometimes permit
tip of the tube is determined by measuring how far the bronchoscope successful intubation where previous attempts have failed. Straight
must be withdrawn from the carina before the tip of the tube becomes blades, such as the Miller blade, are especially useful in patients with
visible. Difficulty advancing the tube is usually from the tube catching on prominent maxillary teeth, a small mandible, an anterior larynx, a floppy
laryngeal structures, and can be corrected by pulling the tube back and epiglottis, or trismus.
advancing with a gentle twisting motion. Rarely, the tube may be too large LMAs are useful as a bridge to oxygenate patients who cannot be intu-
for the glottic opening, requiring the bronchoscope to be withdrawn and a bated, but cannot be counted on to do so in the presence of abnormal
smaller tube to be placed instead. Of note, cricoid pressure may decrease lung mechanics or very abnormal anatomy. 36
the time and difficulty of fiberoptic intubation. 31 Care must be taken when using classic LMAs in such situations; a
The technique for nasal fiberoptic intubation is similar in most malpositioned LMA can insufflate the esophagus and increase the risk of
regards. Most operators will introduce the ETT through the nose and into aspiration. Even when properly inserted, ventilation pressures over 20 cm
the nasopharynx, thus proving patency of the nare and allowing the tube H O can cause both leaks and esophageal and gastric insufflation. The
2
to be used as a guide through the nose for the bronchoscope. Viewing LMA-ProSeal™ is a better option than a classic LMA under these conditions.
conditions for the nasal approach are also improved by either the jaw The LMA-ProSeal™ is an advanced form of the classic LMA and has
thrust or the tongue-tug, especially in unconscious or sedated patients. four components: cuff, inflation line with pilot balloon, airway tube,
■ INTUBATING WITH A LARYNGEAL MASK AIRWAY and drain tube (see Fig. 45-2). The drain tube communicates with the
esophageal inlet and permits blind insertion of gastric tubes for venting
LMAs in their various forms have become a critical component of airway of the stomach. The LMA-ProSeal introducer is provided to aid inser-
management, especially in difficult-to-mask ventilate and difficult-to- tion of the LMA-ProSeal without the need to place fingers in the mouth.
intubate patients (Fig. 45-2). A variety of LMAs (eg, the classic, Fastrach™, The technique of LMA-ProSeal placement with the introducer is similar
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Supreme™, and ProSeal™) have been designed to facilitate ventilation and to LMA-Fastrach placement.
intubation under the most difficult conditions. As with most airway man- The features of the LMA-ProSeal provide more patient manage-
agement skills, the use of such devices appears to be deceptively easy and ment options. While the classic LMA may be used with low-pressure
unskilled practitioners will have a high rate of failure. 33,34 PPV, the LMA-ProSeal has been designed for use with PPV at higher
The intubating LMA is designed to facilitate tracheal intubation with airway pressures. The drain tube will direct any regurgitated fluid to
a large size ETT. It has a rigid anatomically curved tube made of stainless the outside, avoiding aspiration of gastric contents; however, it is not as
steel with a standard 15-mm connector, and an epiglottic elevating bar effective as an ETT in preventing aspiration.
(EEB). The caudal end of the EEB is not fixed, allowing it to elevate the Another alternative for management of the difficult airway that has
epiglottis when an ETT is passed through the aperture. The tube is large become increasingly popular over the past 5 years involves the use of vide-
enough to accept a cuffed 8-mm ETT, and is short enough to ensure pas- olaryngoscopes. These devices (eg, the GlideScope™, Airtraq™, and Pentax
sage of the ETT cuff beyond the vocal cords. The Fastrach is fitted with a AWS™) are generally similar in overall shape to classic rigid laryngoscopes,
rigid handle to facilitate one-handed insertion, removal, and adjustment but have a video camera near the blade tip. The camera transmits images of
of the device’s position. the glottic structures to a screen on the handle of the device or to a remote
The device permits single-handed insertion from any position without monitor. Compared to conventional rigid laryngoscopy, this allows the air-
moving the head and neck from a neutral position and without placing way manager to “see around corners” using a relatively rigid device. This is
fingers in the mouth. Ventilation and oxygenation may be continued advantageous when a straight line from the upper incisors to the vocal cords
during intubation attempts, lessening the likelihood of desaturation. cannot be achieved with standard laryngoscopy. These devices can thus be
Prior to insertion of the LMA-Fastrach, the cuff should be tightly successfully used in situations where classic rigid laryngoscopy fails. They
deflated using a syringe so that it forms a smooth spoon shape without can also be successfully employed in clinical situations where copious blood
any wrinkles on the distal edge. Lubricant is applied to the posterior or secretions would make classic fiber optic approaches difficult or impos-
surface of the LMA before insertion. The cuff is inflated with 20, 30, or sible. Some of these devices are less rigid and less bulky than others, making
40 mL of air for size 3, 4, or 5 LMAs, respectively. them more useful in some settings (eg, awake airway management, trismus)
The application of cricoid pressure reduces the chances of successfully than others. Videolaryngoscopes also permit visualization without requir-
positioning the LMA and intubating the trachea by 30%. For this reason, ing extension of the neck, which is advantageous in patients with cervical
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and because LMAs do not protect against aspiration, the intubating LMA trauma or other contraindications to extension of the atlantooccipital joint.

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