Lars Hyldborg Lundstrøm

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.

Avoidance of neuromuscular blocking agents may increase the risk of difficult tracheal intubation: a cohort study of 103 812 consecutive adult patients recorded in the Danish Anaesthesia Database

BACKGROUND Previous studies indicate that avoiding neuromuscular blocking agents (NMBAs) may be a risk factor for difficult tracheal intubation (DTI). We investigated whether avoiding NMBA was associated with DTI. METHODS A cohort of 103,812 consecutive patients planned for tracheal intubation by direct laryngoscopy was retrieved from the Danish Anaesthesia Database. We used an intubation score based upon the number of attempts, change from direct laryngoscopy to a more advanced technique, or intubation by a different operator. We retrieved data on age, sex, ASA physical status classification, priority of surgery, time of surgery, previous DTI, modified Mallampati score, BMI, and the use of NMBA. Using logistic regression, we assessed whether avoiding NMBA was associated with DTI. RESULTS The frequency of DTI was 5.1 [95% confidence interval (CI): 5.0-5.3]%. In a univariate analysis, avoiding NMBA was associated with DTI, odds ratio (OR) 1.52 (95% CI: 1.43-1.61)%, P<0.0001. Using multivariate analysis, avoiding NMBA was associated with DTI, OR 1.48 (95% CI: 1.39-1.58), P<0.0001. Among patients intubated using NMBA, a multivariate analysis identified patients anaesthetized with only non-depolarizing NMBA to be more at risk for DTI than those anaesthetized with depolarizing NMBA alone. CONCLUSIONS Avoiding NMBA may increase the risk of DTI. However, confounding by indication may be a problem in this observational study and systematic reviews with meta-analysis or more randomized clinical trials are needed.

Diagnostic accuracy of anaesthesiologists’ prediction of difficult airway management in daily clinical practice: a cohort study of 188 064 patients registered in the Danish Anaesthesia Database

Both the American Society of Anesthesiologists and the UK NAP4 project recommend that an unspecified pre‐operative airway assessment be made. However, the choice of assessment is ultimately at the discretion of the individual anaesthesiologist. We retrieved a cohort of 188 064 cases from the Danish Anaesthesia Database, and investigated the diagnostic accuracy of the anaesthesiologists’ predictions of difficult tracheal intubation and difficult mask ventilation. Of 3391 difficult intubations, 3154 (93%) were unanticipated. When difficult intubation was anticipated, 229 of 929 (25%) had an actual difficult intubation. Likewise, difficult mask ventilation was unanticipated in 808 of 857 (94%) cases, and when anticipated (218 cases), difficult mask ventilation actually occurred in 49 (22%) cases. We present a previously unpublished estimate of the accuracy of anaesthesiologists’ prediction of airway management difficulties in daily routine practice. Prediction of airway difficulties remains a challenging task, and our results underline the importance of being constantly prepared for unexpected difficulties.

Poor prognostic value of the modified Mallampati score: a meta-analysis involving 177 088 patients

The modified Mallampati score is used to predict difficult tracheal intubation. We have conducted a meta-analysis of published studies to evaluate the Mallampati score as a prognostic test. A total of 55 studies involving 177 088 patients were included after comprehensive electronic and manual searches. The pooled estimates from the meta-analyses were calculated based on a random-effects model and a summary receiver operating curve. Meta-regression analyses were performed to explore sources of possible heterogeneity between the studies. The summary receiver operating curve demonstrated an area under the curve of 0.75. The pooled odds ratio for a difficult intubation with a modified Mallampati score of III or IV was 5.89 [95% confidence interval (CI), 4.74-7.32]. The pooled estimates of the specificity and sensitivity were 0.91 (CI, 0.91-0.91) and 0.35 (CI, 0.34-0.36), respectively. The pooled positive and negative likelihood ratios were 4.13 (CI, 3.60-4.66) and 0.70 (CI, 0.65-0.75), respectively. The meta-analyses had statistical and clinical heterogeneity ranging from 87.2% to 99.4%. Meta-regression analyses did not identify any significant explanation of the heterogeneity. We conclude that the prognostic value of the modified Mallampati score was worse than that estimated by previous meta-analyses. Our assessment shows that the modified Mallampati score is inadequate as a stand-alone test of a difficult laryngoscopy or tracheal intubation, but it may well be a part of a multivariate model for the prediction of a difficult tracheal intubation.

A documented previous difficult tracheal intubation as a prognostic test for a subsequent difficult tracheal intubation in adults.

We investigated the diagnostic accuracy of a documented previous difficult tracheal intubation as a stand‐alone test for predicting a subsequent difficult intubation. Our assessment included patients from the Danish Anaesthesia Database who were scheduled for tracheal intubation by direct laryngoscopy. We used a four‐point scale to grade the tracheal intubation. A previous difficult intubation was defined according to the presence of a record documenting a difficult penultimate tracheal intubation‐score for the 15 499 patients anaesthetised more than once. Our assessment demonstrates that a documented history of previous difficult or failed intubation using direct laryngoscopy are strong predictors of a subsequent difficult or failed intubation and may identify 30% of these patients. Although previous investigators have reported predictive values that exceed our findings markedly, a documented previous difficult or failed tracheal intubation appears in everyday anaesthetic practice to be a strong predictor of a subsequent difficult tracheal intubation.

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.

Prediction of difficult mask ventilation using a systematic assessment of risk factors vs. existing practice - a cluster randomised clinical trial in 94,006 patients.

We compared implementation of systematic airway assessment with existing practice of airway assessment on prediction of difficult mask ventilation. Twenty‐six departments were cluster‐randomised to assess eleven risk factors for difficult airway management (intervention) or to continue with their existing airway assessment (control). In both groups, patients predicted as a difficult mask ventilation and/or difficult intubation were registered in the Danish Anaesthesia Database, with a notational summary of airway management. The trials primary outcome was the respective incidence of unpredicted difficult and easy mask ventilation in the two groups. Among 94,006 patients undergoing mask ventilation, the incidence of unpredicted difficult mask ventilation in the intervention group was 0.91% and 0.88% in the control group; (OR) 0.98 (95% CI 0.66–1.44), p = 0.90. The incidence of patients predicted difficult to mask ventilate, but in fact found to be easy (‘falsely predicted difficult’) was 0.64% vs. 0.35% (intervention vs. control); OR 1.56 (1.01–2.42), p = 0.045. In the intervention group, 86.3% of all difficult mask ventilations were not predicted, compared with a higher proportion 91.2% in the control group, OR 0.61 (0.41–0.91), p = 0.016. The systematic intervention did not alter the overall incidence of unpredicted difficult mask ventilations, but of the patients who were found to be difficult to mask ventilate, the proportion predicted was higher in the intervention group than in the control group. However, this was at a ‘cost’ of increasing the number of mask ventilations falsely predicted to be difficult.

Organizational factors and long-term mortality after hip fracture surgery. A cohort study of 6143 consecutive patients undergoing hip fracture surgery.

Objective In hospital and health care organizational factors may be changed to reduce postoperative mortality. The aim of this study is to evaluate a possible association between mortality and ‘length of hospital stay’, ‘priority of surgery’, ‘time of surgery’, or ‘surgical delay’ in hip fracture surgery. Design Observational cohort study. Setting Prospectively and consecutively reported data from the Danish Anaesthesia Database were linked to The Danish National Registry of Patients and The Civil Registration System. Records on vital status, admittance, discharges, codes of diagnosis, anaesthetic and surgical procedures were retrieved. Participants 6143 patients aged more than 65 years undergoing hip fracture surgery. Main Outcome Measures All-cause mortality. Results The one year mortality was 30% (28–31%, 95% Confidence interval (CI)). In a multivariate model ‘length of hospital stay’ less than 10 days and more than 20 days are associated with mortality with hazard ratios of 1.34 (1.20–1.53 CI, p<0.001) and 1.27 (1.06–1.51 CI, p<0.001), respectively. ‘Priority of surgery’ categorized as ‘non-scheduled’ is associated with mortality with a hazard ratio of 1.31 (1.13–1.50 CI, p<0.001). Surgical delay and time of surgery are not significantly associated with mortality. Conclusion Non-scheduled surgery and length of hospital stay were associated with increased mortality. Confounding by indication may bias observational studies evaluating early and late discharge as well as priority; therefore cluster randomized clinical trials comparing different clinical set ups may be warranted evaluating health care organizational factors.

Ultrasound-guided lateral infraclavicular block evaluated by infrared thermography and distal skin temperature

Brachial plexus blocks cause changes in hand and digit skin temperature. We investigated thermographic patterns after the lateral infraclavicular brachial plexus block. We hypothesised that a successful lateral infraclavicular block could be predicted by increased skin temperature of the 2nd and 5th digits.

Use versus avoidance of neuromuscular blocking agent for improving conditions during tracheal intubation or direct laryngoscopy in adults and adolescents

This is the protocol for a review and there is no abstract. The objectives are as follows: We will evaluate the effect of using neuromuscular blocking agents versus no use of neuromuscular blocking agents on the difficulties of tracheal intubation (DTI) for adults and adolescents allocated tor tracheal intubation with direct laryngoscopy. We will look at various outcomes, conduct subgroup and sensitivity analyses, examine the role of bias, and apply trial sequential analysis (TSA) (Brok 2008; Brok 2009; Thorlund 2009; Wetterslev 2008) to examine the level of evidence for this intervention.