Charlotte V. Rosenstock

High body mass index is a weak predictor for difficult and failed tracheal intubation: a cohort study of 91,332 consecutive patients scheduled for direct laryngoscopy registered in the Danish Anesthesia Database.

Background:Previous studies have failed to detect high body mass index (BMI) as a risk factor for difficult tracheal intubation (DTI). BMI was investigated as a risk factor for DTI in patients planned for direct laryngoscopy. Methods:A cohort of 91,332 consecutive patients planned for intubation by direct laryngoscopy was retrieved from the Danish Anesthesia Database. A four-point scale to grade the tracheal intubation was used. Age, sex, American Society of Anesthesiologists physical status classification, priority of surgery, history of previous DTI, modified Mallampati-score, use of neuromuscular blocker, and BMI were retrived. Logistic regression to assess whether BMI was associated with DTI was performed. Results:The frequency of DTI was 5.2% (95% confidence interval [CI] 5.0–5.3). In multivariate analyses adjusted for other significant covariates, BMI of 35 or more was a risk for DTI with an odds ratio of 1.34 (95% CI 1.19–1.51, P < 0.0001). As a stand alone test, BMI of 35 or more predicted DTI with a sensitivity of 7.5% (95% CI 7.3–7.7%) and with a predictive value of a positive test of 6.4% (95% CI 6.3–6.6%). BMI as a continuous covariate was a risk for failed intubation with an odds ratio of 1.031 (95% CI 1.002–1.061, P < 0.04). Conclusions:High BMI is a weak but statistically significant predictor of difficult and failed intubation and may be more appropriate than weight in multivariate models of prediction of DTI.

Complaints related to respiratory events in anaesthesia and intensive care medicine from 1994 to 1998 in Denmark

Background: In Denmark, a National Board of Patients’ Complaints (NBPC) was founded in 1988. This study analyses anaesthetic complaints related to adverse respiratory events filed at the NBPC from 1994 to 1998 to point out directions for possible preventive measures.

Inter-observer agreement of tests used for prediction of difficult laryngoscopy/tracheal intubation.

Background:  Guidelines recommend pre‐operative airway evaluation for the prediction of airway management difficulties. Combining tests for evaluation increases the accuracy of the assessment. One model including seven parameters transformed into a simplified airway risk index (SARI) has been proven to be valid. We determined the inter‐observer agreement of the specific test combinations included in SARI as well as of the total score.

Cutaneous Sensory Block Area, Muscle-Relaxing Effect, and Block Duration of the Transversus Abdominis Plane Block: A Randomized, Blinded, and Placebo-Controlled Study in Healthy Volunteers.

Background and Objectives The transversus abdominis plane (TAP) block is a widely used nerve block. However, basic block characteristics are poorly described. The purpose of this study was to assess the cutaneous sensory block area, muscle-relaxing effect, and block duration. Methods Sixteen healthy volunteers were randomized to receive an ultrasound-guided unilateral TAP block with 20 mL 7.5 mg/mL ropivacaine and placebo on the contralateral side. Measurements were performed at baseline and 90 minutes after performing the block. Cutaneous sensory block area was mapped and separated into a medial and lateral part by a vertical line through the anterior superior iliac spine. We measured muscle thickness of the 3 lateral abdominal muscle layers with ultrasound in the relaxed state and during maximal voluntary muscle contraction. The volunteers reported the duration of the sensory block and the abdominal muscle–relaxing effect. Results The lateral part of the cutaneous sensory block area was a median of 266 cm2 (interquartile range, 191–310 cm2) and the medial part 76 cm2 (interquartile range, 54–127 cm2). In all the volunteers, lateral wall muscle thickness decreased significantly by 9.2 mm (6.9–15.7 mm) during a maximal contraction. Sensory block and muscle-relaxing effect duration were 570 minutes (512–716 minutes) and 609 minutes (490–724 minutes), respectively. Conclusions Cutaneous sensory block area of the TAP block is predominantly located lateral to a vertical line through the anterior superior iliac spine. The distribution is nondermatomal and does not cross the midline. The muscle-relaxing effect is significant and consistent. The block duration is approximately 10 hours with large variation.

Tracheal intubation with a flexible fibreoptic scope or the McGrath videolaryngoscope in simulated difficult airway scenarios: a randomised controlled manikin study.

BACKGROUND Flexible fibreoptic endoscopic (FFE) intubation is considered the ‘gold-standard’ when difficult airway management is anticipated. Several videolaryngoscopes have been developed to facilitate intubation by laryngoscopy. OBJECTIVE The aim of the study was to compare the performance of the McGrath series 5 videolaryngoscope (McGrath videolaryngoscope) and the FFE for tracheal intubation in manikins with a simulated difficult airway, hypothesizing that the McGrath videolaryngoscope intubation would prove faster than FFE intubation. DESIGN A randomised controlled study. SETTING The Danish Institute for medical simulation between December 2009 and June 2010. PARTICIPANTS Twenty-eight anaesthesia residents participating in the Danish mandatory 3-day airway management course. INTERVENTIONS All participants received instructions and training in the use of the McGrath videolaryngoscope and FFE. The participants then performed tracheal intubation on a SimMan manikin once with the McGrath videolaryngoscope and once with the FFE in three difficult airway scenarios: (1) pharyngeal obstruction; (2) pharyngeal obstruction and cervical rigidity; (3) tongue oedema. MAIN OUTCOME MEASURES We measured successful intubations, defined as intubation within 120 s, and time to tracheal intubation. RESULTS The trachea was intubated within 120 s with the McGrath videolaryngoscope in 25 out of 27 (93%), 25 out of 28 (89%) and 18 out of 28 (64%) occasions compared with 11 out of 28 (40%), 11 out of 28 (40%) and 16 out of 28 (57%) with the FFE in scenarios (1), (2) and (3), respectively. Time to tracheal intubation was shorter with the McGrath videolaryngoscope in scenarios (1) and (2) than with the FFE (Wilcoxon signed rank sum test, P < 0.0001). CONCLUSION The McGrath videolaryngoscope is a valuable device with higher success rate and a quicker performance in simulated difficult airways. In patients, videolaryngoscopy may have a role in difficult airway algorithms, but the optimal device has yet to be found.

Incidence of unanticipated difficult airway using an objective airway score versus a standard clinical airway assessment: the DIFFICAIR trial - trial protocol for a cluster randomized clinical trial

BackgroundPre-operative airway assessment in Denmark is based on a non-specific clinical assessment. Systematic, evidence-based and consistent airway assessment may reduce the incidence of unanticipated difficult airway management. By assessing multiple predictors for difficult airway management, the predictive value of the assessment increases. The Simplified Airway Risk Index (SARI) is a multivariate risk score for predicting difficult intubation.This study aims to compare the use of the SARI with a non-specified clinical airway assessment on predicting difficult intubation. Further, to compare the examination and registration of predictors for difficult mask ventilation with a non-specified clinical airway assessment on prediction of difficult mask ventilation.Method/DesignWe cluster-randomized 28 Danish departments of anaesthesia to airway assessment either by the SARI or by usual non-specific assessment. Data from patients’ pre-operative airway assessment are registered in the Danish Anaesthesia Database. Objective scores for intubation and mask ventilation grade the severity of airway managements. The accuracy of predicting difficult intubation and mask ventilation is measured for each group. The primary outcome measure is the fraction of unanticipated difficult and easy intubation.The fraction of unanticipated difficult intubation in Denmark is 1.87%. With a stratified randomization, type 1 error risk of 5% and a power of 80%, 30 departments are required to detect or reject a 30% relative risk reduction equalling a number needed to treat of 180. Sample size estimation is adjusted for the study design and based on standards for randomization on cluster-level. With an average cluster size of 2,500 patients, 70,000 patients will be enrolled over a 1-year trial period. The database is programmed so that registration of the SARI and predictors for difficult mask ventilation are mandatory for the intervention group but invisible to controls.DiscussionIt is innovative to use a national clinical database as the basis for a randomized clinical trial. The method can serve as a precedent for implementation of evidence-based recommendations and database registration.The trial will forward understanding of how to predict and reduce unanticipated difficult airways and how to produce evidence-based recommendations for airway assessment and clinical database development.Trial registration(NCT01718561)

Risk Factors for and Prediction of a Difficult Neuraxial Block: A Cohort Study of 73,579 Patients from the Danish Anaesthesia Database.

Background A difficult neuraxial block (DNB) may be associated with complications. The aims of this study were to estimate the prevalence of DNB, assess patient-related and organizational factors associated with DNB, and evaluate the diagnostic accuracy of an accumulated risk score for predicting DNB. Methods A consecutive cohort of 73,579 patients was retrieved. A predefined DNB score and information on patient-related and organizational factors were included in the analyses. Logistic regression analysis was performed. We evaluated the diagnostic accuracy of an accumulated weighted point score of the patient-related risk factors of DNB. Results The prevalence of DNB and abandoned neuraxial block was 3.9 (95% confidence interval [95% CI], 3.7–4.0) and 0.2 (95% CI, 0.16–0.22), respectively. Body mass index of 35 or higher and previous DNB were associated with DNB, with 3.23 (95% CI, 2.87–3.65) and 2.00 (95% CI, 1.33–3.00), respectively. However, the remaining patient-related covariates were associated with DNB with substantial lower odds ratios. The diagnostic accuracy of an accumulated sum score demonstrated an area under the curve of 0.62 (95% CI, 0.61–0.64), a positive predictive value of 5%, and a positive likelihood ratio of 1.4. Conclusions Despite of strong statistical association between DNB and the tested risk factors, the low odds ratios and estimates of the diagnostic test indicate that the clinical impact using an accumulated risk sum score is limited.

“Eyeball test” of thermographic patterns for predicting a successful lateral infraclavicular block

PurposeIncreased distal skin temperature can be used to predict the success of lateral infraclavicular (LIC) block. We hypothesized that an “eyeball test” of specific infrared thermographic patterns after LIC block could be used to determine block success.MethodsIn this observational study, five observers trained in four distinct thermographic patterns independently evaluated thermographic images of the hands of 40 patients at baseline and at one-minute intervals for 30 min after a LIC block. Sensitivity, specificity, and predictive values of a positive and a negative test were estimated to evaluate the validity of specific thermographic patterns for predicting a successful block. Sensory and motor block of the musculocutaneous, radial, ulnar, and median nerves defined block success. Fleiss’ kappa statistics of multiple interobserver agreements were used to evaluate reliability.ResultsAs a diagnostic test, the defined specific thermographic patterns of the hand predicted a successful block with increasing accuracy over the 30-min observation period. Block success was predicted with a sensitivity of 92.4% (95% confidence interval [CI], 86.8 to 96.2) and with a specificity of 84.0% (95% CI, 70.3 to 92.4) at min 30. The Fleiss’ kappa for the five observers was 0.87 (95% CI, 0.77 to 0.96).ConclusionWe conclude that visual evaluation by an eyeball test of specific thermographic patterns of the blocked hands may be useful as a valid and reliable diagnostic test for predicting a successful LIC block.RésuméObjectifUne température accrue de la peau distale peut être utilisée pour prédire la réussite d’un bloc infraclaviculaire latéral (ICL). Nous avons émis l’hypothèse qu’un ‘test à coup d’œil’, c’est-à-dire l’observation subjective, de motifs thermographiques infrarouge spécifiques apparaissant après un bloc ICL pourrait être utilisé pour prédire la réussite du bloc.MéthodeDans cette étude observationnelle, cinq observateurs formés pour quatre relevés thermographiques distincts ont évalué de manière indépendante les images thermographiques des mains de 40 patients avant l’intervention, puis à des intervalles d’une minute pendant 30 minutes après l’installation d’un bloc ICL. La sensibilité, la spécificité et les valeurs prédictives d’un test positif et négatif ont été estimées afin d’évaluer la validité de motifs thermographiques spécifiques pour prédire la réussite d’un bloc. Le bloc était considéré comme réussi s’il y avait bloc sensitif et moteur des nerfs musculocutané, radial, cubital et médian. La mesure statistique du Kappa de Fleiss mesurant les concordances multiples inter-observateur a été utilisée afin d’évaluer la fiabilité.RésultatsEn tant que test diagnostique, les relevés thermographiques spécifiques définis de la main ont prédit la réussite du bloc avec une précision croissante au cours de la période d’observation de 30 minutes. La réussite du bloc a été prédite avec une sensibilité de 92,4 % (intervalle de confiance [IC] 95 %, 86,8 à 96,2) et une spécificité de 84,0 % (IC 95 %, 70,3 à 92,4) à la minute 30. Le Kappa de Fleiss était de 0,87 (IC 95 %, 0,77 à 0,96) pour les cinq observateurs.ConclusionNous concluons que l’évaluation subjective ‘à coup d’œil’ de motifs thermographiques spécifiques des mains sous un bloc peut être utile comme test diagnostic valide et fiable pour prédire la réussite d’un bloc ILC.

Reply to: performance of videolaryngoscope and flexible fibreoptic endoscope in simulating difficult airways.

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