Page 568 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

388 PART 4: Pulmonary Disorders

(>6 mg/kg) of lidocaine for topical anesthesia, since lidocaine is readily some kind. At first glance, this appears to be conspicuous success, but
absorbed by the mucosa of the pharynx and symptoms of local anesthe- compared to airway management in the operating room, it is a very high
sia toxicity can develop above this dose. Some practitioners routinely rate of failure, and a very high rate of requirement for a surgical airway.
perform transtracheal or superior laryngeal nerve blocks to facilitate No doubt some of the need for surgical airways in these patients is a
awake intubation, but these procedures add little to topical anesthesia consequence of their pathology, their anatomy, and the circumstances
of the proximal airway, and can cause significant bleeding in coagulo- surrounding their airway management. Nevertheless, it seems plausible
pathic patients. In addition, topical/local anesthesia schemes that avoid if not certain that the requirement for a surgical airway in some of these
anesthetizing the trachea have several advantages in the ICU setting. patients is a consequence of the use of either intravenous anesthetics or
They allow the patient to retain some ability to protect from aspiration, muscle relaxants as part of their airway management.
and they also allow confirmation of tracheal intubation when the patient
coughs in response to introduction of the tube into the trachea. PROCEDURES FOR INTUBATION
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The use of intravenous agents to facilitate tracheal intubation in
the ICU can be hazardous. The degree of hypovolemia, myocardial Compared to the operating room environment, arterial oxygen desatu-
dysfunction, and shock that often exists in these patients is difficult to ration occurs quite rapidly in most patients undergoing intubation in
ascertain prior to manipulating the airway in an urgent situation. Doses the ICU, even if the patient has been preoxygenated with 100% oxygen.
of intravenous agents that are well tolerated or even subtherapeutic in Factors that contribute to desaturation include an increased alveolar-
healthy patients can precipitate respiratory arrest or circulatory collapse arterial gradient, decreased functional residual capacity (FRC), and
in critically ill patients, converting a serious situation into a desperate increased metabolic rate. Accordingly, all patients undergoing airway
one. Intravenous lidocaine in a dose of 100 mg is frequently sufficient to management in the ICU should be preoxygenated.
induce general anesthesia in patients with shock. The use of intravenous The presence and help of well-trained assistants increases safety and
agents such as midazolam, fentanyl, thiopental, etomidate, propofol, success of intubation. Assistants might include other physicians, ICU
and ketamine should be restricted to experienced practitioners. When nurses, respiratory therapists, and others trained in airway management
indicated, these agents may be used to either titrate up to an acceptable and routinely engaged in the bedside care of critically ill patients. Ideally,
level of sedation (which will be accompanied by a corresponding decline the person managing the airway in the ICU has several helpers, one to help
in both hemodynamics and minute ventilation, with associated worsen- position the patient and apply cricoid pressure, one to hand off equipment,
ing of hypoxia and hypercapnia), or to deliberately induce a brief period and one to monitor the patient and administer IV drugs as necessary.
of general anesthesia. Patients in cardiopulmonary arrest are relatively straightforward to
■ MUSCLE RELAXANTS AND AIRWAY MANAGEMENT intubate, as they are typically unconscious and flaccid. No drug therapy
is necessary to facilitate airway management in these patients. Direct
IN THE INTENSIVE CARE UNIT laryngoscopy should be attempted immediately, and the largest possible
The use of muscle relaxants to facilitate airway management in the ICU endotracheal tube (ETT) should be inserted into the trachea. Many
remains controversial. Although these agents are routinely administered patients will have aspirated oral secretions or gastric contents prior to or
to facilitate airway management in the operating room, their use in ICU after their cardiopulmonary arrest, and the necessity of suctioning using
patients is probably not essential. The use of intravenous induction agents a rigid catheter (Yankauer) to achieve adequate visualization should be
to initiate general anesthesia is motivated by the desire to produce intubat- anticipated. Patients receiving cardiopulmonary resuscitation (CPR)
ing conditions quickly and to minimize unpleasant recall. Most patients may not deliver much carbon dioxide to their lungs, and attempts to
undergoing elective surgery tolerate the hemodynamic consequences of confirm endotracheal intubation with CO monitors should anticipate
2
intravenous anesthetic agents well and can be readily oxygenated and this possibility. In these instances, the use of other techniques such as
ventilated with a bag and mask. When anesthesiologists are confronted the Ambu Tubechek Esophageal Intubation Detector bulb (Ambu Inc,
with patients who have abnormal airway anatomy or who may be impos- Denmark) to rule out esophageal intubation may be necessary. The
sible to oxygenate or ventilate with a bag and mask, they typically opt ability to detect carbon dioxide in the exhaled gases of such patients is
for awake intubation strategies, as outlined in this chapter. Muscle relax- an accepted sign of the recovery of a spontaneous circulation. Cervical
ants, including succinylcholine, vecuronium, mivacurium, rocuronium, instability is the only coexisting condition that requires serious con-
and cisatracurium should be used only by those who are experienced sideration during the intubation of a patient receiving CPR. All other
in managing the airway with an Ambu bag and mask, and who are medical and anatomic considerations are secondary in this situation.
thoroughly versed in techniques used to manage the difficult airway. The In the past few years, there have been several clinical studies that have
reason for this stipulation is that once these agents are administered, it is demonstrated an association between nasal intubation and the evolution
imperative that a definitive airway is obtained within minutes. Attempts of sinusitis, and between sinusitis and the development of ventilator-
at ventilating most patients in respiratory failure with an Ambu bag and associated pneumonia (VAP) (see Chap. 59). Given this, it is probably
mask are often difficult and frequently futile, since the decreased compli- the case that the oral route of intubation is preferable in most critically ill
ance of the lungs and/or increased airway resistance makes it difficult patients. Nasal intubation may still be desirable in a select population of
to maintain adequate minute ventilation. This is especially likely to be patients with normal immunity, normal coagulation status, and relative
an issue when a “rapid sequence” intubation is planned for a patient in contraindications to oral intubation.
is no effort to ensure that bag-mask ventilation will be possible prior to ■ OROTRACHEAL INTUBATION
whom there are concerns about aspiration since with this technique there
administering the muscle relaxant. Among muscle relaxants available Advantages of oral intubation include the requirement for less equipment
to facilitate airway management, succinylcholine remains the agent of (a laryngoscope), less trauma and bleeding, a lower incidence of sinus-
first choice in ICU and ER patients for whom it is not contraindicated. 8 itis and VAP, and a high success rate independent of patient respiratory
There is an established literature supporting the use of intravenous effort. 22,23 The disadvantages of oral intubation include the substantial stim-
anesthetic agents and muscle relaxants to facilitate airway management ulus associated with direct laryngoscopy, risk of dental and cervical trauma,
in both the field and the emergency department. 9-19 This literature difficulty securing the tube, difficulty of maintaining oral hygiene, and
suggests that the use of intravenous agents can both improve intubat- the occasional problem of a patient biting the tube. In addition, patients
ing conditions and cause hypotension, and that brain-injured trauma must generally be supine to undergo orotracheal intubation. Orotracheal
patients have worse outcomes. 20,21 Airway management utilizing muscle intubation is far more difficult to accomplish than it appears to the casual
relaxants in these reports is associated with a success rate in the range observer, especially in the less-than-ideal conditions that are typical of
of 94% to 99%, with 1% of patients requiring a surgical airway of airway management in the ICU.

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