Andranik Ovassapian

practice Guidelines for Management of the Difficult airway An Updated Report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway

RACTICE Guidelines are systematically developed recommendations that assist the practitioner and patient in making decisions about health care. These recommendations may be adopted, modified, or rejected according to clinical needs and constraints and are not intended to replace local institutional policies. In addition, Practice Guidelines developed by the American Society of Anesthesiologists (ASA) are not intended as standards or absolute requirements, and their use cannot guarantee any specific outcome. Practice Guidelines are subject to revision as warranted by the evolution of medical knowledge, technology, and practice. They provide basic recommendations that are supported by a synthesis and analysis of the current literature, expert and practitioner opinion, open-forum commentary, and clinical feasibility data. This document updates the “Practice Guidelines for Management of the Difficult Airway: An Updated Report by

Fiberoptic nasotracheal intubation--incidence and causes of failure.

Although flexible fiberscopes have been used to facilitate difficult tracheal intubations (1-3), there is little information on the incidence and causes of failure with use of flexible fiberscopes for this purpose. All elective nasotracheal intubations in this institution, including those in patients with proven difficulty of intubation, are performed with fiberscopes. This paper reports the incidence of difficult fiberoptic nasotracheal intubation (FNI) and the failure rate in 423 consecutive carefully monitored such intubations.

Airway management in adult patients with deep neck infections: A case series and review of the literature

Patients with deep neck infections, especially those with Ludwig’s angina, may die as a result of airway management mishaps. Skillful airway management is critical, but a safe method of airway control in these patients is yet to be established. We subjected patients with deep neck infections to fiberoptic tracheal intubation by using topical anesthesia to provide general anesthesia for surgical interventions. Patient characteristics and techniques for intubations were recorded on a special data-collection form. Of the 26 patients, 17 had Ludwig’s angina, and 9 had other types of deep neck infections. Three patients were tracheally intubated while in the sitting position, 2 in Fowler’s position, and 21 in the supine position with the head up 10°–15°. Tracheal intubations were successful in 25 patients: 19 nasally and 6 orally. After surgery, seven patients were kept tracheally intubated, and five patients had tracheostomies. Complications were limited to three cases of mild epistaxis and four oversedations with transient hypoxemia. Twelve patients remembered part of the procedure, and two considered it unpleasant. Tracheal intubation with a flexible bronchoscope by using topical anesthesia is highly successful in adult patients with deep neck infections. Tracheostomy using local anesthesia is recommended if fiberoptic intubation is not feasible, if the clinician is not skillful in the use of awake fiberoptic intubation, or if intubation attempts have failed.

Blood pressure and heart rate changes during awake fiberoptic nasotracheal intubation

Hypertension and tachycardia associated with orotracheal intubation may result from direct laryngoscopy (1,2), placement of the endotracheal tube (1,2), and succinylcholine if used (3). With awake fiberoptic nasotracheal intubation (FNI) the stimulation of rigid laryngoscopy and succinylcholine are avoided. All elective nasotracheal intubations in our institution are performed with the patient sedated and using topical anesthesia and a flexible fiberscope. This report analyzes changes in mean arterial pressure (MAP) and heart rate (HR) during 200 such intubations to determine whether avoidance of rigid laryngoscopy and succinylcholine decreases the incidence and the severity of hypertension and tachycardia that are associated with tracheal intubation.

The effect of sevoflurane and desflurane on upper airway reactivity

Background Although bronchial reactivity can be assessed by changes in airway resistance, there is no well-accepted measure of upper airway reactivity during anesthesia. The authors used the stimulus of endotracheal tube cuff inflation and deflation to assess changes in airway reactivity in patients anesthetized with sevoflurane and desflurane. Methods Sixty-four patients classified as American Society of Anesthesiologists physical status I or II participated in this randomized, double-blind study. Patients were anesthetized with either sevoflurane or desflurane at 1.0 and 1.8 minimum alveolar concentration (MAC). The trachea was stimulated by inflating the endotracheal tube cuff. A blinded observer assessed the severity of patient response to the stimulus and changes in hemodynamic variables. The process was repeated at the second MAC treatment condition. Results At 1.0 MAC, patients anesthetized with desflurane had a more intense response and a greater likelihood of significant coughing and associated hemodynamic changes (both at P < 0.05). At 1.8 MAC, sevoflurane and desflurane both suppressed clinically significant responses to tracheal stimulation. Interrater reliability was excellent for this measure of upper airway reactivity (P < 0.001). Conclusions The assessment of the cough response to tracheal stimulation by endotracheal tube cuff inflation is a reliable and clinically meaningful measure of upper airway reactivity. At 1.0 MAC, sevoflurane is superior to desflurane for suppressing moderate and severe responses to this stimulus.

Sellick's maneuver: to do or not do.

M. Ramez Salem, MD† The introduction of cricoid pressure (CP) by Sellick in 1961 “to control regurgitation until intubation with a cuffed endotracheal tube was completed” was met with an enthusiastic reception worldwide and rapidly became an integral component of the rapid sequence induction/intubation technique (RSII). The maneuver consisted of “occlusion of the upper esophagus by backward pressure on the cricoid ring against the bodies of cervical vertebrae to prevent gastric contents from reaching the pharynx.” Sellick provided evidence that extension of the neck and application of CP obliterated the esophageal lumen at the level of the 5th cervical vertebra, as seen in a previously placed soft latex tube distended with contrast media to a pressure of 100 cm H2O. He also confirmed the value of CP in preventing saline (run into the esophagus from a height of 100 cm H2O) from reaching the pharynx in a patient undergoing gastroesophagectomy. Sellick emphasized that the lungs can be ventilated by intermittent positive pressure and that CP can prevent inflation of the stomach during positive pressure ventilation. References to CP were found in the literature more than 230 yr ago. In a letter from Dr. W. Cullen to Lord Cathcart dated August 8, 1774, concerning the recovery of persons “drowned and seemingly dead,” the use of CP by Dr. Monro was referred to as a means of preventing gastric distension during inflation of the lungs. Before Sellick described CP, several techniques were used in patients at risk of aspiration of gastric contents: awake intubation, induced hyperventilation with carbon dioxide during inhaled induction, and RSII performed with the patient in a 40° head-up tilt. The rationale behind the head-up tilt was that gastric contents could not reach the laryngeal level even if contents were moved up into the esophagus. The RSII with CP was extended not only to emergency surgical and obstetrical procedures and the critical care setting, but also to elective procedures in patients at risk of aspiration of gastric contents. The plethora of manuscripts, correspondence, and reviews on CP is a testimony to its relevance to anesthetic practice and continuing interest to clinicians. In the last 2 decades, clinicians have questioned the efficacy of CP and therefore the necessity of the maneuver. Some suggested abandoning it on the following grounds: (a) Its effectiveness has been demonstrated only in cadavers, and therefore its efficacy lacks scientific validation. (b) It induces relaxation of the lower esophageal sphincter. (c) There have been reports of regurgitation of gastric contents and aspiration despite CP. (d) The esophagus is not exactly posterior to the cricoid, and thus the maneuver is unreliable in producing midline esophageal compression. (e) It is associated with nausea/vomiting and also with esophageal rupture. (f) It makes tracheal intubation and mask ventilation difficult or impossible. Because of ethical considerations, a controlled study of the efficacy of CP is not feasible. Even if such a study were conducted, it would probably yield little information, given the low incidence of pulmonary aspiration. The compelling evidence supporting the effectiveness of CP comes from studies that unequivocally demonstrate its efficacy in preventing gastric inflation in anesthetized children and adults. It is inconceivable that a maneuver effective in preventing gastric inflation during manual ventilation would not be effective in preventing esophageal contents from reaching the pharynx. The study by Rice et al. in the current issue sheds new light on the efficacy of CP. In 24 awake volunteers, magnetic resonance imaging was From the *Department of Anesthesia and Critical Care, Airway Study and Training Center, University of Chicago; and †Department of Anesthesiology, Advocate Illinois Masonic Medical Center, Department of Anesthesiology, University of Illinois College of Medicine, Chicago, Illinois. Accepted for publication June 18, 2009. Address correspondence and reprint requests to Andranik Ovassapian, MD, Department of Anesthesia and Critical Care, Airway Study and Training Center, University of Chicago, 5841 South Maryland Ave., Chicago, IL 60637. Address e-mail to aovassap@dacc. uchicago.edu. Copyright

Hemodynamic responses associated with lithotripsy.

Because ESWL produces a painful stimulus, general or regional anesthesia is required to prevent not only pain but also movement by the patient that might alter the position of a stone targeted on the image intensifier screen (3). Extracorporeal shock wave lithotripsy requires that the anesthetized patient be immersed in water in a semisitting position while high energy shock waves are delivered to the kidney to crush the stone (4). Anesthesia, immersion in water, and ESWL itself may significantly affect the cardiovascular system and the kidney (3-7), but the cardiovascular responses have not been quantitated in detail. We therefore undertook the present study in ll patients of hemodynamic changes associated with general anesthesia and ESWL, as measured by a transesophageal Doppler ultrasonic cardiac output monitor, other methods for measuring hemodynamic function being difficult in patients almost totally immersed in water. cost (1,2).

Difficult mask ventilation: what needs improvement?

Andranik Ovassapian, MD‡ In their review, El-Orbany and Woehlck shed light on the problem of difficult mask ventilation (DMV). They raise concerns about definitions and highlight the pathophysiology, incidence, and prediction of this rather neglected aspect of airway management. Their review analyzes the relationship between DMV and difficult intubation and outlines corrective measures and management options. We concur with the authors that clear and meaningful definitions are needed for DMV as well as other aspects of airway management. There is no consensus on an exact definition of the sniffing, neutral, and simple extension positions. In general, the sniffing position implies extension at the atlantooccipital joint and flexion at the cervical spine, but it is not clear how high from horizontal the head should be elevated for the sniffing position. Should the head elevation be greater in tall-necked than in short-necked subjects? Because no strict definitions exist, research papers cannot be interpreted or compared fairly. In the algorithm proposed by El-Orbany and Woehlck (and in the American Society of Anesthesiologists difficult airway algorithm), reference to 2-person mask ventilation is emphasized. Benumof defined the optimal attempt at mask ventilation as a 2-person method with appropriately sized oroor nasopharyngeal airways. Unfortunately, when unanticipated DMV is encountered, a second anesthesiologist is not always available. Rather than relying on another colleague to compress the reservoir bag, the anesthesiologist can use both hands to obtain appropriate mask seal, while the ventilator can be used to deliver the desired tidal volume. The lone anesthesiologist then uses both hands to advance the mandible, and the head straps are used to further improve the mask seal. Neither the 1-person, 2-handed mask ventilation, nor the use of the ventilator to deliver tidal volume is new. In 1959, Safar et al. validated the usefulness of a 2-handed jaw thrust method for reversing pharyngeal obstruction. Ventilators have been utilized in studying the efficacy of mask ventilation in children and in the management of DMV in adults. Alternatives to the use of the ventilator include compressing the reservoir bag between the knees, under the axilla, or even under the foot, while using both hands to maintain an adequate airway. These maneuvers, however, require that the reservoir bag be connected to a long corrugated hose, instead of being mounted on the anesthesia machine. The upper airway can be obstructed by soft tissue at the pharyngeal or laryngeal level, and by laryngospasm induced by opioids and anesthetics, or occurring after tracheal extubation. In patients with obstructive sleep apnea (OSA), anatomical imbalance between the upper airway soft tissue volume and craniofacial size is partially corrected for by the contraction of the pharyngeal airway dilating muscles during wakefulness. When patients are unconscious, the neuromuscular control of the upper airway muscles becomes diminished or lost. The tongue and structures attached to the hyoid bone gravitate toward the posterior pharyngeal wall, causing various degrees of airway obstruction. Maximum mandibular advancement with mouth opening (with the use of oroor nasopharyngeal airways) and assumption of the sniffing position can be effective in opening the airway by stretching the genioglossus muscle and pulling From the *Department of Anesthesiology, Advocate Illinois Masonic Medical Center; †Department of Anesthesiology, University of Illinois College of Medicine; and ‡Department of Anesthesia and Critical Care, University of Chicago, Chicago, Illinois. Accepted for publication August 16, 2009. Address correspondence and reprint requests to M. Ramez Salem, MD, Department of Anesthesiology, Advocate Illinois Masonic Medical Center, 836 W. Wellington Ave., Chicago, IL 60657. Address e-mail to ramez. salem-md@advocatehealth.com. Copyright

The effects of methoxyflurane on ventilation in man.

Minute volume, tidal volume, respiratory frequency, end-tidal carbon dioxide, and ventilatory response to carbon dioxide inhalation were studied during anesthesia at three different concentrations of end-tidal methoxyflurane, 0.19, 0.37, and 0.82 per cent, in 12 unpremedicated patients prior to surgery. Minute volume rose during light anesthesia and fell with increasing concentrations. Tidal volume decreased progressively from 0.49 liters awake, to 0.22 liters at the highest concentration, while respiratory rate rose from 11 to 22 per minute. End-tidal carbon dioxide rose progressively from 38.6 torr while awake, to 43.4 torr during deep anesthesia. More striking was the change in slope of the carbon dioxide response curve, which decreased progressively with increasing depth of anesthesia from 56 per cent of the control response in light anesthesia, through 28 to 9 per cent during deep anesthesia. An estimate of MAC for methoxyflurane in this study was 0.17 per cent, which agrees with previous reports despite employment of different criteria.

Principles of Airway Management, Third Edition.

Effective airway management is essential for safe administration of anesthesia and successful resuscitation of cardiac arrest patients. A new interest in the safety of airway management has emerged in the past 15 yr, signified by the introduction of new airway devices, the emergence of guidelines for managing the difficult airway, the large number of publications on the subject, and the formation of the Society for Airway Management. These strides are unmatched in any other period of 15 yr since the birth of general anesthesia in 1846. The introduction of the LMA-ClassicTM in 1988, followed by the LMAFastrachTM and the LMA-ProSealTM (The Laryngeal Mask Company (UK) Limited, Bucks, United Kingdom), has generated more than 2000 publications alone. The third edition of Principles of Airway Management is a timely publication reflecting the changes and improvements in airway management. In this new edition, Drs. Finucane and Santora present 13 chapters of clinically useful, technically oriented information. With the exception of Chapter 1, “Airway Anatomy,” all of the chapters are extensively revised and expanded. The high quality of the drawings and pictures from the second edition is preserved, and many new ones are added. The third edition is expanded, with 160 more pages than the second edition. Several chapters are worthy of special mention. A well-deserved new chapter is devoted to laryngeal mask airways. The new chapter discusses the various applications of laryngeal mask airways in airway management, their role in management of a difficult airway, and their application in specific procedures such as fiberoptic bronchoscopy during general anesthesia. I was also impressed with the chapter discussing airway evaluation. Considering space limitations, there is thorough consideration of tests thought to predict difficult direct laryngoscopy, including the significant limitations of all these techniques. The chapter addressing the difficult airway benefits from the consideration of both difficult mask ventilation and difficult intubation. Appreciation of both is critical because each presents a different scenario and requires a different route in the difficult airway algorithm of the American Society of Anesthesiologists’ Practice Guidelines for Management of the Difficult Airway. Failure of both facemask ventilation and tracheal intubation presents an extremely dangerous situation, calling for good judgment, correct selection, and skillful application of the method to avoid brain damage or death. This chapter is also enhanced by a supplemental nine-page appendix that summarizes syndromes associated with a difficult airway. Another highlight includes the chapter dealing with fiberoptic intubation, specific techniques for intubation, and preparation of a patient for awake intubation. Several tables and drawings add to the value and clarity of this chapter. One criticism I have of this text is the arrangement of some of the materials. The chapter entitled “Fiberoptic Airway Management Techniques” would be better positioned after the chapter describing “The Difficult Airway.” The discussion of the complications of tracheal intubation would more logically follow the chapter describing techniques of tracheal intubation. The LMA-ClassicTM and LMA-ProSealTM should be presented early in the chapters describing basic airway management and basic airway management equipment, reflecting their fundamental importance in current practice. The LMA-FastrachTM and flexible bronchoscope should also be briefly mentioned in the intubation chapter, because their use is now routine in intubation techniques and must be mastered in nonemergency situations. The longest chapter, “Surgical Approach to Airway Management,” includes transtracheal jet ventilation and retrograde intubation, which do not seem to belong in this chapter. One of the unique strengths of this text is the emphasis on teaching of airway skills, especially that of rigid and fiberoptic intubation. Airway-related deaths, hypoxic brain damage, unnecessary tracheostomies, other major complications, and thousands of case cancellations after failed intubation each year are unacceptably high. We need better and more serious training of individuals engaged in airway management, and this text represents an important contribution to this effort. In summary, the authors should be commended for their contribution to the understanding of the basics and the importance of airway management. This text is well written and richly illustrated, with numerous excellent references. Reading this book is strongly recommended for all those engaged in airway management, from medical students to experienced practitioners. It offers practical clinical information that is critical for safe airway management and should be a readily available reference in all acute care settings.