Does Cricoid Pressure Make Intubation More Difficutl?

Dr. Wasson

Cricoid Pressure Does Not Increase the Rate of Failed Intubation by Direct Laryngoscopy in Adults

Anesthesiology 2005; 102:315-19

Turgeon, et al apply a double blind, randomized study conducted at the Centre Hospitalier Affilie Universitaire de Quebec, involving 830 patients > 18 years old to evaluate the effect of applying cricoid pressure (CP) during direct laryngoscopy and oral endotracheal tube placement.  Over a 7 month period, 700 patients were randomized into either a CP group and a sham CP group.  There was no difference in gender, age, ASA physical status, anthropometric characteristics, or risk factors for difficult intubation.    Additionally, the distribution of the anesthesiologists and anesthesia assistants was comparable .  The primary endpoint was the rate of failed intubation at 30 seconds; secondary endpoints included intubation time, grade of laryngoscopic views, and Intubation Difficulty Scale score.  Outcomes show similar rates of failed intubation at 30 seconds, grades of laryngoscopic view and the Intubation Difficulty Scale; while median intubation time was slightly longer in those who received CP.  Turgeon, et al conclude that CP, whether provided by trained personnel or a sham technique does not increase the rate of failed intubation.  Therefore, if CP use is indicated, one should not withhold the technique for fear of increasing the difficulty of intubation.  

New Predictor of Difficult Intubation???

Dr. C. Chon

Neck circumference to thyromental distance ratio: a new predictor of difficult intubation in obese patients

Kim, W.H., et al. British Journal of Anaesthesia. 2011 Feb 24;doi:10.1093/bja/aer024

Anesthesiologists from an academic medical center in Seoul, South Korea enrolled 260 ASA I or II patients undergoing general anesthesia with tracheal intubation. 123 patients were assigned to the obese group (BMI ³ 27.5, as per the WHO’s Asian obesity criteria) and 125 patients were assigned to the non-obese group (BMI < 27.5). 12 patients were excluded because of incomplete data.

Using the intubation difficulty scale (IDS), difficult intubation -- defined by an IDS ³ 5 -- was more frequent in the obese group than the non-obese group (13.8% vs 4.8%; P=0.016). Multivariate analysis revealed the Mallampati score, the Wilson score, and neck circumference-to-thyromental distance ratio (NC/TM) were independently associated with difficult intubation. Among these, NC/TM showed a higher sensitivity and negative predictive value than the other airway measures.

Numerous studies looking at preoperative airway measures have suggested that single tests have limited value in predicting difficult intubations. However, combining numerous measures and risk factors, as is done to when calculating the El-Ganzouri or Wilson scores, can be cumbersome and time-consuming. This study combines two valuable risk factors (neck circumference and thyromental distance), which the researchers say “may increase the diagnostic value while not increasing the burden of [testing].”

Awake Fiberoptic vs Video Laryngoscopy

Dr. Halonen

Awake fiberoptic or awake video laryngoscopy tracheal intubation in patients with anticipated difficult airy management

Charlotte V Rosenstock et al, Anesthesiology, June 2012- Vol 116- Number 6, p 1210-1216

Summary

The gold standard for intubation in patients with anticipated difficult airways is the use of awake flexible fiberoptic intubation (FFI). The randomized clinical trial was performed to test their hypothesis that McGrath video larynscope (MVL) would be faster than FFI in these patients.

Besides time for intubation, they also compared the success of intubation in the first attempt, the ease of intubation and the patient discomfort between the two techniques. What they found is that there was no difference any of the categories that were tested between the two techniques. Because of this, maybe further studies should be performed to determine if the MVL technique should take over as the gold standard for suspected difficult intubations. Obviously, one technique should not be used if their are contraindications to that technique or if the anesthesiologists is not comfortable in performing that technique. 

Predictors of LMA Failure

Chang-Ho Chon, DO

Article:
Predictors and Clinical Outcomes from Failed Laryngeal Mask Airway Unique^TM

Ramachandran, Satya K., et al. Anesthesiology. June 2012 – Vol 116 – No. 6, pp 1217-26

Summary:

The reported rate of failure with use of supraglottic airway devices is 0.2-8%. However, little is known about the risk-adjusted prediction of LMA failure requiring rescue tracheal intubation and its impact on patient outcomes.

This prospective study included 15,795 adult (³18 yr) undergoing general anesthesia at a University of Michigan affiliated quaternary care facility with the use of the LMA Unique^TM (uLMA) in both ambulatory and nonambulatory settings. 170 patients (1.1%) experienced the primary outcome of uLMA^TM failure, defined as an airway event requiring uLMA^TM removal and tracheal intubation. More than 60% of patients with uLMA^TM failure experienced significant hypoxia, hypercapnia, or airway obstruction; 42% were unable to be adequately ventilated due to significant leak.

Four risk factors contributing to LMA failure were identified:  surgical table rotation, male sex, poor dentition, thick neck, and increased body mass index. Patients in which the uLMA^TM failed were 3 times more difficult to mask ventilate. Among outpatients with uLMA^TM failure, 13.7% required unplanned admission to the hospital, of whom 5.6% required intensive care for persistent hypoxemia.

The results of this study support the use of the LMA as a safe supraglottic airway device with relatively low failure rate (1.1%). However, there are clear consequences to LMA failure, including unplanned or prolonged hospitalization. Furthermore, the researchers remind us that certain risk factors increase the rate of failure.

Accuracy in Identifying the Cricothyroid Membrane, Dr. P. Lee

Paul Lee, DO

Article review

Accuracy of Identification of the Cricothyroid Membrane in Female Subjects Using Palpation: An Observational Study

The cricothyroid membrane (CTM) is the recommended site of access to the airway during cricothyroidotomy to provide emergency oxygenation. Despite the apparent simplicity of the technique, this rescue maneuver frequently fails to achieve its goals and complications are numerous. The reasons for this failure are unclear. We sought to determine the ability of physicians to correctly identify the CTM in female patients. Using fluorescent “invisible” ink, the physician was asked to mark the CTM with the patient in the supine neutral position and then with the head extended. The actual level was identified using ultrasound and the distance between the actual and estimated margin of the CTM was measured. A correct estimation was defined as a mark made between the upper and lower limits of the membrane and within 5 mm of midline. Participants were also asked to assess the ease of CTM palpation using a 10-cm visual analog scoring (VAS) scale. Fifty-six patients participated of whom 15 were obese. In the supine neutral neck position, the CTM was identified in 10/41 vs 0/15 (P = 0.048) in nonobese versus obese, respectively. Of the 46 incorrectly identified CTMs in this position, 24 were above (maximum 3 cm) and 22 below (maximum 3 cm) the actual level. Similar results were observed when the patients were placed with the neck in the extended position; the CTM was identified correctly in 12/41 vs 1/15 nonobese and obese patients, respectively. The range of values was also extensive; the estimation of the position of the membrane was as high as 2.5 cm above and 4 cm below the actual level, and up to 1.6 cm laterally. Participating doctors found palpation of the CTM subjectively more difficult in the obese than nonobese groups; VAS score for palpation difficulty was 5.25 ± 2.5 vs 3.3 ± 2.5, respectively, P = 0.005. Using multiple linear regression, VAS scores for palpation correlated negatively with increased patient height (P < 0.001) and greater thyromental distance (P = 0.006), and correlated positively with increased sternomental distance (P = 0.011) and neck circumference (P = 0.001). Misidentification of the CTM in female patients is common and its localization is less precise in those who are obese. This has implications for the likely success of invasive airway access via the CTM. Emergency cricothyroidotomy is a life-saving maneuver that may prevent death or permanent neurological injury in the event of difficult or failed airway management and is thus a core skill for anesthesiologists. Despite its crucial importance, it is a rare requirement in clinical practice. Consequently, individual clinical experience, even for experienced anesthesiologists, is infrequent and may in fact be a once-in-a-career event. Clearly, accurate anatomic localization of the cricothyroid membrane (CTM) is of critical importance before emergency cricothyroidotomy. Should the CTM be misidentified and the invasive airway device be misplaced, the consequences include continued hypoxia, airway trauma, esophageal penetration/perforation, and vascular and neural injury. The ability of clinicians to accurately identify the CTM has not been studied extensively. The purpose of this study was to determine the accuracy of clinical identification of the CTM using the traditional palpation technique. We hypothesized that the CTM would be more likely to be misidentified in obese patients than in normal weight patients on the basis that anatomical landmarks might be obscured

OSA predicts adverse outcomes, Dr. Halonen

Jeff Halonen, DO

Article

Obstructive Sleep Apnea Predicts Adverse Perioperative Outcome

Bateman, Brian MD and Eikermann, Matthias MD, PhD, Anesthesiology, April 2012- Vol 116- Number 4, p 753-755.

Summary

OSA is an important risk factor for cardiovascular disease, myocardial infarction, stroke and perhaps has an association with postoperative delirium (POD). The definition for this review of delirium is an acute, fluctuating impairment in attention and cognition. OSA, independent of obesity, has been shown by most studies to be an independent risk of Perioperative complications. These complications may be from drug side effects, inflammation and hypercoaguability.

While this study can not link OSA and PoD directly, they do make some interesting speculations. Frequent episodes of airway collapse in OSA lead to hypoxia, disrupted sleep, sleep inertia, daytime sleepiness and increased arousal threshold from sleep, all of which may be consider as potential precipitating and/or augmenting factors of delirium. These are all associated with inflammation and OSA is also, in part, an inflammatory disease.  From this, the associated observed between OSA and POd should be considered "hypothesis-generating" rather than "proven."