A simple technique to measure difficulty associated with endotracheal intubation

76

Abstracts

for nasotracheal intubation in a prospective, blinded, randomized clinical trial. This study was performed to test whether direct laryngoscopy is superior to the GVL for nasotracheal intubation, as judged by the time to intubation (TTI) and the ease of intubation. Methods: After written, informed consent, patients having elective dental surgery requiring nasotracheal intubation were randomized to either direct laryngoscopy or GlideScope videolaryngoscopy. All operators had experience using the GVL for orotracheal intubation, but not necessarily for nasotracheal intubation. Exclusion criteria included age less than 18 years, a known or suspected difficult airway, cervical spine instability, or patients requiring rapid sequence induction. The operator was blind until intubation began. Time to intubation was assessed by a blinded observer. Ease of intubation was recorded by the operator on a 100-mm visual analogue scale (0—easy, 100—difficult). Two minutes after intubation, oropharyngeal suctioning was performed, and the degree of blood present was qualitatively recorded. On postoperative day 1, the patient was asked about the presence and severity of a sore throat. Results: Time to intubation was significantly less in the GlideScope (GS) group than in the direct laryngoscopy (DL) group. Nasotracheal intubation was significantly easier in the GS group. The first-attempt success rate was 97% in the GS group. There was a trend to less sore throat in the GS group. Outcome

DL (n = 32)

GS (n = 31)

P

TTI (s), median (IQR) Ease of intubation VAS (mm), median (IQR) First-attempt success rate, n (%) Cormack-Lehane laryngoscopic grades, n Grade 1 Grade 2 and higher Moderate or severe sore throat, n (%) Moderate or copious bleeding, n (%) Unique operators, n

67.0 (54.7, 87.8) 45.3 (39.6, 68.5) 0.005 17.5 (9.5, 31.5) 10.0 (6.0, 18.0) 0.016

29 (90.6)

30 (96.8)

0.61

22 10 9 (28.1)

29 2 3 (9.7)

0.022

5 (15.6) 14

8 (25.8)

0.11 0.61

13

Conclusions: In a heterogeneous group of operators, the GVL results in a clinically important and statistically significant reduction in the TTI compared with direct laryngoscopy, results in improved glottic exposure, and is also slightly easier to use. The first-attempt success rate for nasotracheal intubation using the GVL is very high. doi:10.1016/j.jclinane.2007.12.004

References [1] Cooper RM, Pacey JA, Bishop MJ, McCluskey SA. Early clinical experience with a new videolaryngoscope (GlideScope) in 728 patients. Can J Anaesth 2005;52:191-8. [2] Hirabayashi Y. GlideScope videolaryngoscope facilitates nasotracheal intubation. Can J Anaesth 2006;53:1163-4.

[3] Xue F, Zhang G, Liu J, et al. A clinical assessment of the GlideScope videolaryngoscope in nasotracheal intubation with general anesthesia. J Clin Anesth 2006;18:611-5. A simple technique to measure difficulty associated with endotracheal intubation Philip Jones MD, Kevin Armstrong MD, Paidrig Armstrong MD, Richard Cherry MD, Jason Hoogstra MD, Christopher Harle MD, Timothy Turkstra MD Department of Anesthesia and Perioperative Medicine, University of Western Ontario, London, Ontario, Canada

Introduction: There is a need for a simple measure of difficulty associated with endotracheal intubation (ETI) to allow quantitative comparison [1,2]. This would also provide a threshold for the definition of difficult intubation (DI). Conventional indices of difficulty such as laryngeal view and number of attempts exhibit poor agreement. The Intubation Difficulty Scale (IDS) [3], introduced as a better technique, measures 7 variables and the arithmetic sum is a scale of difficulty, a value of 6 or more defining DI. However, the IDS, available for 11 years, has failed to establish itself in common clinical usage, probably because of its complexity. We present a simple measure of difficulty based on a combination of modified Cormack and Lehane [4,5] (C&L) grade of laryngeal view + number of attempts, called the Simplified Intubation Difficulty Score and compared its performance to that of the IDS. Materials and methods: With institutional review board approval for data collection, information was prospectively collected on 5,910 consecutive adult surgical patients undergoing ETI under general anesthesia for all surgical specialties. Endotracheal intubation was performed, and modified C&L grade, the number of attempts at laryngoscopy, the need for specialized intubation techniques, and all the variables required to calculate the IDS were documented. A degree of difficulty was assigned by an attending anesthesiologist as easy (D0), awkward (D1), significant difficulty (D2), extreme difficulty (D3), or impossible (D4). Multiple indices of difficulty were recorded for each patient, allowing comparison of the performance of one against any of the others. Because of poor agreement among the currently available indices of difficulty, we proposed a new approach to defining difficulty. It requires any two of the following four indices of difficulty being present: C&L grade 3 or 4 view, three or more attempts at intubation, need for specialized intubation techniques, or the attending anesthesiologist considers the patient a true DI. If any two of the four difficulty indices are abnormal it is a true DI. To construct a continuous measure of difficulty associated with ETI, we suggest the following approach: • SIDS = C&L grade + number of attempts. • As the value of SIDs increases the degree of difficulty of ETI increases. • If SIDS = 5, there is a very high probability (not certainty) that it is a true DI. There are several ways to accrue a score of 5 or more: Grade 4 laryngeal view patients require at least one attempt at ETI and accrue a SIDS score = 5;

Abstracts Table 1

77 Performance of IDS vs SIDS judged against a population of true DI patients IDS, n

Data available for analysis How many reached threshold to define DI How many easy ETI Incidence DI, %

5,835 229 5,606 229/5,838

Evaluation by a requirement of two or more abnormal indices of difficulty Number incorrectly identified as difficult (false positives) 85/229 Number incorrectly identified as easy (false negatives) 81/5,606

Incidence, %

SIDS, n

Incidence, %

5,910 250 3.92%

4.23%

37% 1.44%

44/250 20/5,660

17.6% 0.35%

χ2 testing for false-positive SIDS statistically significantly superior to IDS, P = .000, χ2 = 23.13 1 df χ2 testing for false-negative SIDS statistically significantly superior to IDS, P = .000, χ2 = 37.76 1 df

Grade 3 laryngeal view patients who require two or more attempts accrue a SIDS score = 5; Grade 2 laryngeal view patients who required three or more attempts accrue a SIDS score = 5; Grade 1 laryngeal view patients who required four or more attempts at ETI accrue a SIDS score = 5; Results: Having identified a population of patients who are true DI we investigated whether the conventional IDS or SIDs was superior in identifying these patients. The true incidence of DI in this database of 5,910 patients as measured by a requirement of two or more abnormal indices of difficulty is 3.82% (Tables 1 and 2). No simple technique such as the SIDS will exhibit perfect performance but neither does the more complex IDS. However, SIDS is simple and can get us very close: • • • •

If SIDS If SIDS If SIDS If SIDS

= 5, = 6, = 7, b 5,

there is there is there is there is

an 82% probability that it is a true DI. a 97% probability that it is a true DI. a 100% probability that it is a true DI. a 0.35% incidence that it is a true DI.

Discussion: The conventional IDS is not widely used because it is unwieldy to calculate. The SIDS is easy to calculate with significantly fewer false positives and negatives. The SIDS gives a continuous measure of difficulty and the user may adjust the threshold at which they want to define difficulty if they prefer. Conclusions: The IDS is a reasonable continuous measure of the difficulty associated with ETI, and the threshold of 6 to identify clinically relevant DI is appropriate. However, it is complicated to calculate and after 11 years has failed to be adopted into widespread clinical or research use. Table 2 Evaluating the success rate of SIDS for each of the possible ways to reach a SIDS score = 5 Grade of C&L view

No. of attempts at ETI

Numbers difficult by SIDS

% difficult by SIDS

4 3 2 1

1 2 3 4

5/5 97/109 99/130 5/6

100% 89% 76% 83.3%

The SIDS gives an incidence of DI which is very close to the true incidence of DI, with far fewer false positives and false negatives than the IDS. The appeal of this method is the extreme simplicity to measure degree of difficulty and it can provide a threshold at which to define DI. doi:10.1016/j.jclinane.2007.12.005

References [1] Yentis SM. Predicting difficult intubation—worthwhile exercise or pointless ritual? Anaesthesia 2002;57:105-9. [2] Benumof JL. The intubation difficulty scale. Anesthesiology 1997;87: 1273-4. [3] Adnet F, Borron SW, Racine SX, et al. The intubation difficulty scale (IDS). Anesthesiology 1997;87:1290-7. [4] Cormack RS, Lehane J. Difficult intubation in obstetrics. Anaesthesia 1984;39:1105-11. [5] Samsoon GL, Young JR. Difficult tracheal intubation: a prospective study. Anaesthesia 1987;42:487-90. A randomized, double-blind comparison of dexmedetomidine and remifentanil for sedation during awake fiberoptic intubations Carin A. Hagberg MD, Nicholas C. Lam MD, Steven I. Abramson MD Department of Anesthesiology, University of Texas Medical School, Houston, TX

Introduction: Awake nasal or oral flexible fiberoptic intubation is often used for airway management of the expected difficult airway. The success of this technique depends upon whether the patient is cooperative and able to maintain spontaneous ventilation. Remifentanil (R) has been successfully used to achieve sedation for this procedure, yet as an opioid may cause respiratory depression. The purpose of this double-blind prospective study was to determine whether dexmedetomidine (D), a centrally acting, selective α-2 agonist, is more effective and safer to use for sedation during awake fiberoptic intubation, as compared to R. Methods: After obtaining approval by the institutional review board; written and informed consent; and randomization, either R or D was administered to sedate 30 patients with expected difficult airways during awake flexible fiberoptic intubation. Preoperatively, all patients received 2 mg midazolam and 0.2 mg glycopyrrolate intravenously and their airways were topicalized with 4% lidocaine. Patients in the R group received a bolus of 0.75 μg/kg over 10 minutes