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Tracheal intubation by trainees does not alter the incidence or duration of postoperative sore throat and hoarseness: a teaching hospital-based propensity score analysis†
BJA Advance Access published August 4, 2015 British Journal of Anaesthesia, 2015, 1–7 doi: 10.1093/bja/aev234 Respiration and the Airway
R E S P I R A T I O N A N D T H E A I R WA Y
propensity score analysis† S. Inoue1, *, R. Abe2, Y. Tanaka2 and M. Kawaguchi2 1
Division of Intensive Care, and 2Department of Anesthesiology, Nara Medical University, 840 Shijo-cho Kashihara, Nara 634-8522, Japan *Corresponding author. E-mail: [email protected]
Abstract Background: Postoperative throat complications, such as sore throat and hoarseness, are frequent complications of tracheal intubation. To assess whether severity of throat complications is related to the experience of physicians performing tracheal intubation, we compared the incidence and duration of postoperative sore throat and hoarseness and patient satisfaction between tracheal intubation performed by trainees and experienced consultant anaesthetists. Methods: This is a retrospective review of an institutional registry containing records of 21 606 patients undergoing general anaesthesia and was conducted with ethics board approval. All tracheal intubations by trainees were performed under the supervision of consultant anaesthetists. To avoid channel bias, the propensity score analysis was used to generate a set of matched cases (intubations by trainees) and controls (intubations by anaesthetists), yielding 3465 (sore throat) and 3267 (hoarseness) matched patient pairs. The incidence and sustained rate of symptoms were compared as primary outcomes. We also compared patient satisfaction with perioperative care. Results: After propensity score matching, there was no difference between tracheal intubation by trainees and tracheal intubation by consultant anaesthetists in the incidences of sore throat (32.9 vs 32.6%, P=0.84) or hoarseness (35.8 vs 35.2%, P=0.60). Odds ratios and 95% confidence intervals for tracheal intubation by trainees were 1.01 (0.91−1.12) for sore throat and 1.03 (0.93−1.14) for hoarseness. The rates of sustained sore throat and hoarseness over the course were low (P=0.85 and P=0.67, respectively). Hazard ratios and 95% confidence intervals for tracheal intubation by trainees were 0.99 (0.94−1.05) for sustained sore throat and 0.99 (0.93−1.05) for sustained hoarseness. Patient satisfaction did not differ between matched groups (P=0.66 and P=0.83). Conclusions: Tracheal intubation by trainees under the supervision of consultant anaesthetists did not worsen the postoperative airway outcomes, such as sore throat and hoarseness. Key words: airway, complications; complications, tracheal intubation; education, untrained personnel
†
The department and institution to which the work should be attributed: Department of Anesthesiology, Nara Medical University. Accepted: June 7, 2015 © The Author 2015. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: [email protected]
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Tracheal intubation by trainees does not alter the incidence or duration of postoperative sore throat and hoarseness: a teaching hospital-based
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Editor’s key points • It is not clear whether or not physicians’ expertise in tracheal intubation affects the incidence of postoperative throat complications, such as sore throat and hoarseness. • In a retrospective study, in which propensity score matching was made to minimize selection bias on outcomes, there was no difference in the incidences of postoperative throat complications between trainees and anaesthetists. • Regardless of the expertise of the intubator, postoperative throat complications frequently occur after tracheal intubation.
Methods Approval for review of patient clinical charts, access to data of the institutional registry of anaesthesia, and reporting the results was obtained from the Nara Medical University Institutional Review Board (no. 942, approved on October 21, 2014).
Perioperative patient treatment No standardization was made for the methods of induction and maintenance of anaesthesia. General anaesthesia was usually induced with i.v. propofol (1–2.5 mg kg−1) plus either fentanyl (0.1–0.2 μg kg−1) or remifentanil (0.2–0.3 μg kg−1 min−1), and neuromuscular block was achieved with rocuronium (0.6–0.9 mg kg−1). Tracheal intubation was performed using a Macintosh-type laryngoscope (Heine™ Classic+Macintosh Fiber Optic blade; Heine USA Ltd, Dover, NH, USA), and the size of the blade (size 3 or 4) was chosen based on the intubator’s preference and the size of the patient. The polyvinyl chloride tracheal tube
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Postoperative throat complications, such as sore throat and hoarseness, are frequent complications of general anaesthesia with tracheal intubation, with reported incidences of sore throat between 11 and 48% and those of hoarseness between 18 and 53%.1–6 The aetiology of throat complications is believed to involve mucosal erosion caused by the cuff of a tracheal tube,7 trauma from tracheal intubation, and mucosal dehydration.8 Modern anaesthesia practices and improved airway devices have reduced these complications. It is not clear whether or not physicians’ experience affects the incidence of postoperative throat complications A prospectively observational study of 809 adult surgical patients reported that the professional assignment and length of professional experience had no influence on the occurrence or intensity of throat complaints.9 In addition, another study including 266 surgical patients found that the experience of the anaesthetist did not significantly alter the incidence of sore throat.10 On the contrary, a prospective observational study including 495 patients reported that the experience of anaesthesia personnel was independently associated with the incidence of sore throat and hoarseness in male patients.11 It is necessary to conduct a definitive study to resolve these contradictory results. To determine whether throat complications after tracheal intubation are related to the physician’s experience, we retrospectively investigated the incidence and duration of postoperative sore throat and hoarseness. We examined whether tracheal intubation by trainees in anaesthesia altered the incidence or duration of postoperative sore throat and hoarseness.
(Mallinckrodt™ Hi−Lo Oral/Nasal Tracheal Tube Cuffed Murphy Eye; Covidien Japan, Tokyo, Japan) with a silicon-coated stylet (Intubating stylet 14F; Japan Medicalnext Co., Ltd, Osaka, Japan) was lubricated at the site of the cuff using an adequate amount of lubrication gel (KY Jelly™; Johnson & Johnson, Tokyo, Japan). Tracheal tubes with low-pressure–high-volume cuffs of 8.0 mm internal diameter were mainly used for males and tubes and cuffs of 7.0 mm internal diameter for females. Immediately after tracheal intubation, the cuff of the tracheal tube was inflated with the minimal amount of air to prevent an audible leak at the airway pressure of 20 cm H2O. If air leak around the cuff could not be prevented with 10 ml of air, the tube was replaced by a tube one size larger. Intracuff pressure was not monitored. Heat and moisture exchangers (DAR™ Adult-Pediatric Electrostatic Filter HME Small; Covidien Japan) were used for all patients. Lidocaine i.v. or lidocaine gel on the tracheal tube was not used. Tracheal intubations were performed by trainees under the guidance of the registered (consultant) anaesthetist or by the consultant anaesthetist. A trainee was defined as a medical school graduate, who had a medical qualification, in a 2yr mandatory clinical training programme currently on rotation in the anaesthesia department (for a couple of months) or a trainee anaesthetist in a 2yr training programme after the mandatory training. In Japan, anaesthetists can apply for registered anaesthetist status to the Ministry of Health, Labour, and Welfare after 2yr of training as a member of the Japanese Society of Anaesthesiologists. All these trainees have completed a simulation-based training course in airway management and passed the practical examination about airway management. Anaesthesia was maintained with sevoflurane (1.5–2%) in a 40% oxygen and air mixture or with propofol (6–10 mg kg−1 h−1). Nitrous oxide was not used. Fentanyl (0.1–0.2 μg kg−1 h−1) or remifentanil (0.1–0.2 μg kg−1 min−1) was used for analgesia. Rocuronium (0.2–0.3 mg kg−1 h−1) was used for neuromuscular block and sugammadex (2–4 mg kg−1) or neostigmine (40 μg kg−1) plus atropine (20 μg kg–1) for reversal of neuromuscular block. Occasionally, postoperative analgesia was provided by i.v. fentanyl or epidural ropivacaine combined with fentanyl using a patient-controlled analgesia device. After completion of anaesthesia, the attendant in charge filled out the form for the institutional registry of anaesthesia, which includes the attendant’s name, the name of the person who performed tracheal intubation, the patient’s characteristics, information on final diagnosis and surgical procedures (later categorized into three classes based on the modified surgical risk stratification),12 background illnesses (hypertension, diabetes mellitus, coronary artery disease, history of heart failure, and lung disease), duration of anaesthesia and surgery, ASA physical status, urgency of surgery (emergency or elective), anaesthesia technique (inhalation or i.v. with or without regional analgesia), intraoperative patient positioning, final airway assessment, requirement for transfusion, implementation of postoperative analgesia, requirement for postoperative intensive care, and adverse intraoperative events (cardiac events, hypotension, arrhythmia, hypoxia, etc.). The attendant in charge of the patient also followed up the patient and recorded any throat symptoms during several postoperative days. At our institute, surgical patients managed by the anaesthesia department undergo a postoperative structured interview with consultant anaesthestists at the postoperative anaesthesia consultation clinic, where the occurrence of perioperative adverse events is assessed, and the patients can critique perioperative management using a self-report form. Until the
Tracheal intubation by trainees and throat complications
10th postoperative day, patients completed a questionnaire including items on incidence and duration of postoperative sore throat and hoarseness and were requested to rate our perioperative care using a simplified patient satisfaction scale (very satisfactory, satisfactory, even, or dissatisfactory). The incidence and duration of postoperative sore throat were determined by referring to both the patient’s report and the postanaesthetic round record.
Data handling
Statistical analysis Continuous variables are presented as the mean and if normally distributed or the median and interquartile range (IQR) if
All anaesthesia patients n=21 606 Patients missing answers for a postoperative questionnaire n=6391 Remaining patients n=15 215 Use of supraglottic devices n=468 Remaining patients n=14 747 Post-tracheostomy or intubation, or tracheostomy n=597 Remaining patients n=14 150 Patients <15 yr old n=1312 Remaining patients n=12 838 Procedures at the sites including larynx, pharynx, and anterior cervical lesion n=717 Remaining patients n=12 121 Patients missing data sets n=1251 for sore throat n=1861 for hoarseness Remaining patients n=10 870 for sore throat n=10 260 for hoarseness
Fig 1 Flow diagram for patient inclusion and exclusion.
non-parametric. Categorical variables are presented as the number of patients and frequency ( percentage). There is a growing interest in the use of propensity scorebased methods in observational studies to estimate treatment effects. The propensity score is defined as the conditional probability of assigning a subject to a particular treatment protocol given a vector of measured covariates.13 14 To minimize the effect of selection bias on outcomes, we used propensity score matching for clinical characteristics to reduce distortion by confounding factors. Using propensity score analysis, we generated a set of matched cases (tracheal intubations by trainees) and controls (tracheal intubations by consultant anaesthetists). As a result of the propensity score matching, 3940 and 3726 patients were excluded from postoperative sore throat analysis and hoarseness analysis, respectively. A propensity score was generated for each patient from a multivariable logistic regression model based on the covariates using data from the institutional registry as independent variables, with treatment type (tracheal intubation by trainees vs tracheal intubation by consultant anaesthetists) as a binary dependent variable. Factors reported to influence the incidence of postoperative throat symptoms include adequate anaesthesia or relaxation of the patient, tracheal intubation technique, (softer) suction catheters, tracheal tube diameter, cuff tracheal contact area, monitoring and adjustment of intracuff pressure, local anaesthetic or steroid lubricants, preoperative physical condition, sex, age, gynaecological surgery, duration of anaesthesia, and intraoperative patient position.1–6 Tracheal intubation techniques, devices, and conditions were based on institutional protocols and were not monitored. However, other factors may have varied and were included as potential confounders. As suggested by a review of statistical research on propensity score development, we used a structured iterative approach to refine this model, with the goal of achieving covariate balance between the matched pairs.14 Covariate balance was measured using the standardized difference, where an absolute difference of ≥0.1 was accepted as a meaningful covariate imbalance.15 We matched patients using a greedy-matching algorithm with a calliper width of 0.001 of the estimated propensity score. A matching ratio of 1:1 was used. This procedure yielded 3465 patients with sore throat and 3267 patients with hoarseness whose tracheas were intubated by trainees propensity matched to 3465 and 3267 patients whose tracheas were intubated by consultant anaesthetists. For statistical inference, methods that account for the matched nature of the samples were used. For overall incident rate, the Cochran–Mantel–Haenszel test, stratified on the matched pair, was used to estimate the odds ratio and 95% confidence interval (CI) of incidence (tracheal intubation by trainees vs tracheal intubation by consultant anaesthetists). Throat symptoms that had lasted for more than a day were defined as sustained symptoms. Plots of the estimated proportion of patients with sustained sore throat or hoarseness over time were constructed by the Kaplan–Meier method separately for the two groups. Patients with sustained throat symptoms when visiting the postoperative anaesthesia clinic were treated as censored cases. The stratified (by matched pair) log-rank test was used to assess the statistical significance of treatment effects, and the stratified (by matched pair) Cox proportional hazard model was used to estimate the hazard ratio and 95% CI for tracheal intubation by trainees vs tracheal intubation by consultant anaesthetists. In addition, the Wilcoxon signed-rank test was used for the matched pair comparison of the simplified patient satisfaction scale.
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Data were collected between January 2009 and December 2013, during which there were 21 606 patients who underwent general anaesthesia. The exclusion criteria for the present study (and reasons for consequent reductions in eligible patients) were as follows: (i) patients missing answers on the postoperative questionnaire (n=6391); (ii) use of supraglottic devices (n=468); (iii) tracheostomy or postsurgical tracheal intubation (n=597); (iv) patient <15 yr old (n=1312); (v) procedures at the evaluation sites including larynx, pharynx, and anterior cervical lesions (n=717); and (vi) patients missing data sets (n=1251 for sore throat and n=1861 for hoarseness). The final numbers for assessment of sore throat and hoarseness were 10 870 and 10 260 patients, respectively (Fig. 1).
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Sample size calculation For the purpose of sample size calculation, we assumed a 40% incidence of postoperative sore throat or hoarseness based on previous reports (11–53%).1–5 We estimated that 2474 patients in each group were required to provide 95% power to detect a 5% difference in the incidence of sore throat or hoarseness (with an overall incidence of 40%) between tracheal intubation by trainees and tracheal intubation by consultant anaesthetists, with a type I error probability of 0.05. Thus, our sample size was sufficient to
detect a difference in outcome. Analyses were computed using R (version 3.0.3; R Foundation for Statistical Computing, Vienna, Austria). A value of P<0.05 was considered statistically significant.
Results The results, based on 10 870 patients with sore throat and 10 260 with hoarseness, are presented in Supplementary materials. The median (IQR) number of years of experience was 1.8 (1−2.7) for
Table 1 Clinical characteristics of the two study groups after propensity score matching (sore throat). ICU, intensive care unit; IQR, interquartile range Trainee intubation (n=3267)
Anaesthetist intubation (n=3267)
Standardized difference
Age [median (IQR); yr] Height [mean (); cm] Weight [mean (); kg] BMI [mean (); kg m−2] Duration of anaesthesia [mean (); min] Duration of surgery [mean (); min] ASA physical status [median (IQR); I–V] Surgical risk stratification [median (IQR); I–III] Sex (female/male) Inhalation anaesthetics (no/yes) With regional analgesia (no/yes) Supine position (no/yes) Coexisting disease (no/yes) Gynaecology (no/yes) Difficult airway (no/yes) Emergency (no/yes) ICU admission (no/yes) Postoperative analgesia (no/yes) Intraoperative incident (no/yes) Transfusion (no/yes)
64 (49–72) 160.11 (9.17) 58.82 (12.03) 22.87 (3.85) 274.47 (153.24) 208.02 (143.58) II (II–II) II (II–II) 1620/1647 635/2632 2292/975 887/2380 960/2307 2878/389 3117/150 2907/360 2498/769 1692/1575 3253/14 2724/543
64 (49–72) 160.30 (9.06) 59.08 (12.19) 22.90 (3.86) 272.60 (144.86) 207.28 (134.86) II (II–II) II (II–II) 1601/1666 638/2629 2285/982 890/2377 985/2282 2858/409 3113/154 2921/346 2490/777 1714/1553 3257/10 2707/560
0.026 0.021 0.009 0.009 0.013 0.005 0.014 0.005 0.012 0.002 0.005 0.002 0.017 0.019 0.006 0.014 0.006 0.014 0.02 0.014
Table 2 Clinical characteristics of the two study groups after propensity score matching (hoarseness). ICU, intensive care unit; IQR, interquartile range Characteristic
Trainee intubation (n=3267)
Anaesthetist intubation (n=3267)
Standardized difference
Age [median (IQR); yr] Height [mean (); cm] Weight [mean (); kg] BMI [mean (); kg m−2] Duration of anaesthesia [mean (); min] Duration of surgery [mean (); min] ASA physical status [median (IQR); I–V] Surgical risk stratification [median (IQR); I–III] Sex (female/male) Inhalation anaesthetics (no/yes) With regional analgesia (no/yes) Supine position (no/yes) Coexisting disease (no/yes) Gynaecology (no/yes) Difficult airway (no/yes) Emergency (no/yes) ICU admission (no/yes) Postoperative analgesia (no/yes) Intraoperative incident (no/yes) Transfusion (no/yes)
64 (49–73) 160.11 (9.17) 58.82 (12.03) 22.87 (3.85) 274.47 (153.24) 208.02 (143.58) II (I–II) II (II–II) 1620/1647 635/2632 2292/975 887/2380 960/2307 2878/389 3117/150 2907/360 2498/769 1692/1575 3253/14 2724/543
63 (49–72) 160.30 (9.06) 59.08 (12.19) 22.90 (3.86) 272.60 (144.86) 207.28 (134.86) II (II–II) II (II–II) 16 016/1666 638/2629 2285/982 890/2377 985/2282 2858/409 3113/154 2921/346 2490/777 1714/1553 3257/10 2707/560
0.026 0.021 0.009 0.009 0.013 0.005 0.014 0.005 0.012 0.002 0.005 0.002 0.017 0.019 0.006 0.014 0.006 0.014 0.02 0.014
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Characteristic
Tracheal intubation by trainees and throat complications
also confirmed that patient satisfaction with perioperative care was not affected by who performed intubation.
Discussion The incidence and duration of postoperative sore throat and hoarseness did not differ between patients who underwent general anaesthesia whose tracheas were intubated by trainees and those whose tracheas were intubated by consultant anaesthetists. Additionally, patient satisfaction did not differ between those whose tracheas were intubated by trainees and those whose tracheas were intubated by consultant anaesthetists. This study suggests that patients receive equal medical care regarding airway management in teaching hospitals because trainees are appropriately trained before participating in airway management, including manikin training, and are closely supervised by a consultant anaesthetist throughout the tracheal intubation process. The incidence of airway complications is thought to depend on the experience of the attending physician. It has been reported that the incidence of multiple tracheal intubation
Table 3 Patient outcome after propensity matching. CI, confidence interval; IQR, interquartile range; NA, not applicable Outcome
Trainee intubation
Anaesthetist intubation
Odds ratio (95% CI)
Effect size
P-value
Incidence of sore throat (yes/no) Satisfaction scale in population for sore throat [median (IQR)] Incidence of hoarseness (yes/no) Satisfaction scale in population for hoarseness [median (IQR)]
1139/2326 4 (3–4) (n=3465)
1130/2335 4 (3–4) (n=3465)
1.01 (0.91–1.12) NA
0.01 0.02
0.84 0.66
1171/2096 4 (3–4) (n=3267)
1150/2117 4 (3–4) (n=3267)
1.03 (0.93–1.14) NA
0.01 0.01
0.60 0.83
Sore throat after adjustment
Rate of sustained sore throat
1.0 Consultant anaesthetist intubation 0.8
Trainee intubation
0.6
0.4 Hazard ratio 0.99
0.2
95% Cl 0.94–1.05
P-value 0.85
0.5% Trainee 0.7% Anaesthetist
0.0 0
2
4
6
8
10
75 68
30 22
24 18
Days Number at risk Anaesthetist 3465 Trainee 3465
803 840
196 197
Fig 2 Curves for the rate of sustained sore throat after adjustment. Blue line shows tracheal intubation by consultant anaesthetists. Green line shows tracheal intubation by trainees. Tick marks indicate censored cases. CI, confidence interval.
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trainees and 13 (9−18) for consultant anaesthetists. The clinical characteristics of the two matched groups ( patients whose tracheas were intubated by trainees and patients whose tracheas were intubated by consultant anaesthetists) extracted by propensity analysis are presented in Tables 1 and 2. According to the standardized difference, covariate balance between the matched pairs was confirmed. Patient outcomes are summarized in Table 3 and Figs 2 and 3. The incidence of sore throat did not differ between tracheal intubation by trainees and tracheal intubation by consultant anaesthetists after propensity matching (32.9 vs 32.6%, respectively). Likewise, there was no difference in the incidence of hoarseness (35.8 vs 35.2%, respectively). In addition, tracheal intubation by trainees did not increase the rates of sustained sore throat and hoarseness, and Kaplan–Meier curves for sustained rate of sore throat were similar. The number of censored cases was 41 (0.6%) for sore throat and 356 (5.4%) for hoarseness. The rates of sustained sore throat and hoarseness on the 10th postoperative day were very low (0.5 vs 0.7 and 3.9 vs 3.3%, respectively). Hazard ratios for tracheal intubation by trainees for sore throat and hoarseness were both almost one. Finally, it was
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Hoarseness after adjustment
Rate of sustained hoarseness
1.0
Consultant anaesthetist intubation Trainee intubation
0.8 0.6 P-value 0.67
Hazard ratio 95% Cl 0.99 0.93–1.05
0.4 0.2
0
2
4
6
8
10
124 145
72 85
64 70
Days Number at risk Anaesthetist Trainee
3267 3267
782 796
239 255
Fig 3 Curves for the rate of sustained hoarseness after adjustment. Blue line shows tracheal intubation by consultant anaesthetists. Green line shows tracheal intubation by trainees. Tick marks indicate censored cases. CI, confidence interval.
attempts, which increases the risk of complications, depends on the years of training and type of residency, and that airway complications decrease significantly when supervised by experienced consultant anaesthetists in a critical care setting.16 17 Therefore, postoperative throat complications are generally believed to be more frequent in patients whose tracheas are intubated by less experienced physicians because of lack of careful technique.1 It is still a matter of debate whether the experience of the anaesthetist can alter the postoperative incidence of throat complications.9–11 It has been suggested that training on a manikin during the early phase of employment may improve the technique and thereby reduce the risk of such airway complications.11 It is therefore reasonable to suppose that completion of our simulation-based training programme before commencement of clinical activity and tracheal intubation by trainees under supervision by consultant anaesthetists favourably affected throat outcomes. Patients who are dissatisfied are known to experience more adverse events attributable to medical practice.18 19 It is therefore reasonable to suppose that postoperative sore throat and hoarseness could significantly impact the overall patient experience of anaesthesia management, during which patients are almost unconscious, if patients consider these minor adverse events as partial outcomes of anaesthesia management. Thus, it may be logical that tracheal intubation by trainees did not reduce patient satisfaction in the present study. This study has a number of limitations. Some data known to influence postoperative outcomes, such as the number of attempts at tracheal intubation, measurement of intracuff pressure, tracheal tube diameter, presence of upper respiratory infection, and multiple attempts at suctioning, were not available. We did not distinguish between the various aetiologies of sore throat. We also did not set a precise follow-up period, so patients who still complained of throat symptoms were censored when they visited the postoperative anaesthesia consultation
clinic. This study relied on patient self-reports to determine the duration of symptoms, which were based on memory, and may have influenced the results. This study was retrospective in nature; thus, unmeasured variables could still confound the results. Finally, a considerable number of patients were excluded from the study. In conclusion, trainee tracheal intubation under the supervision of consultant anaesthetists did not worsen postoperative throat symptoms compared with tracheal intubation by consultant anaesthetists. Patient satisfaction with perioperative care also did not differ, regardless of who performed tracheal intubation.
Authors’ contributions Study design and writing of the first draft of the paper: S.I. Data collection: S.I., R.A. Data analysis: S.I., Y.T. Reviewing the first draft of the paper and rewriting: M.K.
Supplementary material Supplementary material is available at British Journal of Anaesthesia online.
Acknowledgements The authors would like to thank Enago (www.enago.jp) for English language review.
Declaration of interest None declared.
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3.9% Trainee 3.3% Anaesthetist
0.0
Tracheal intubation by trainees and throat complications
Funding Departmental resources.
References
12. Eagle KA, Berger PB, Calkins H, et al. ACC/AHA guideline update for perioperative cardiovascular evaluation for noncardiac surgery—executive summary. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery). Circulation 2002; 105: 1257–67 13. D’Agostino RB Jr. Propensity score methods for bias reduction in the comparison of a treatment to a non-randomised control group. Stat Med 1998; 17: 2265–81 14. Austin PC. Propensity-score matching in the cardiovascular surgery literature from 2004 to 2006: a systematic review and suggestions for improvement. J Thorac Cardiovasc Surg 2007; 134: 1128–35 15. Austin PC, Grootendorst P, Anderson GM. A comparison of the ability of different propensity score models to balance measured variables between treated and untreated subjects: a Monte Carlo study. Stat Med 2007; 26: 734–53 16. Hirsch-Allen AJ, Ayas N, Mountain S, Dodek P, Peets A, Griesdale DE. Influence of residency training on multiple attempts at endotracheal intubation. Can J Anaesth 2010; 57: 823–9 17. Schmidt UH, Kumwilaisak K, Bittner E, George E, Hess D. Effects of supervision by attending anesthesiologists on complications of emergency tracheal intubation. Anesthesiology 2008; 109: 973–7 18. Taylor BB, Marcantonio ER, Pagovich O, et al. Do medical inpatients who report poor service quality experience more adverse events and medical errors? Med Care 2008; 46: 224–8 19. Weingart SN, Pagovich O, Sands DZ, et al. What can hospitalised patients tell us about adverse events? Learning from patient-reported incidents. J Gen Intern Med 2005; 20: 830–6
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1. McHardy FE, Chung F. Postoperative sore throat: cause, prevention, and treatment. Anaesthesia 1999; 54: 444–53 2. Christensen AM, Willemoes-Larsen H, Lundby L, Jakobsen KB. Postoperative throat complaints after tracheal intubation. Br J Anaesth 1994; 73: 786–7 3. Higgins PP, Chung F, Mezei G. Postoperative sore throat after ambulatory surgery. Br J Anaesth 2002; 88: 582–4 4. Hara K, Maruyama K. Effect of additives in lidocaine spray on postoperative sore throat, hoarseness and dysphagia after total intravenous anesthesia. Acta Anaesthesiol Scand 2005; 49: 463–7 5. Tazeh-Kand NF, Eslami B, Mohammadian K. Inhaled fluticasone propionate reduces postoperative sore throat, cough, and hoarseness. Anesth Analg 2010; 111: 895–8 6. Orandi A, Orandi A, Najafi A, Hajimohammadi F, Soleimani S, Zahabi S. Post-intubation sore throat and menstruation cycles. Anesth Pain Med 2013; 3: 243–9 7. Combes X, Schauvliege F, Peyrouset O, et al. Intracuff pressure and tracheal morbidity: influence of filling with saline during nitrous oxide anesthesia. Anesthesiology 2001; 95: 1120–4 8. Navarro RM, Baughman VL. Lidocaine in the endotracheal tube cuff reduces postoperative sore throat. J Clin Anesth 1997; 9: 394–7 9. Biro P, Seifert B, Pasch T. Complaints of sore throat after tracheal intubation: a prospective evaluation. Eur J Anaesthesiol 2005; 22: 307–11 10. Kloub R. Sore throat following tracheal intubation. Middle East J Anaesthesiol 2001; 16: 29–40 11. Jaensson M, Gupta A, Nilsson UG. Gender differences in risk factors for airway symptoms following tracheal intubation. Acta Anaesthesiol Scand 2012; 56: 1306–13
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R E S P I R A T I O N A N D T H E A I R WA Y
propensity score analysis† S. Inoue1, *, R. Abe2, Y. Tanaka2 and M. Kawaguchi2 1
Division of Intensive Care, and 2Department of Anesthesiology, Nara Medical University, 840 Shijo-cho Kashihara, Nara 634-8522, Japan *Corresponding author. E-mail: [email protected]
Abstract Background: Postoperative throat complications, such as sore throat and hoarseness, are frequent complications of tracheal intubation. To assess whether severity of throat complications is related to the experience of physicians performing tracheal intubation, we compared the incidence and duration of postoperative sore throat and hoarseness and patient satisfaction between tracheal intubation performed by trainees and experienced consultant anaesthetists. Methods: This is a retrospective review of an institutional registry containing records of 21 606 patients undergoing general anaesthesia and was conducted with ethics board approval. All tracheal intubations by trainees were performed under the supervision of consultant anaesthetists. To avoid channel bias, the propensity score analysis was used to generate a set of matched cases (intubations by trainees) and controls (intubations by anaesthetists), yielding 3465 (sore throat) and 3267 (hoarseness) matched patient pairs. The incidence and sustained rate of symptoms were compared as primary outcomes. We also compared patient satisfaction with perioperative care. Results: After propensity score matching, there was no difference between tracheal intubation by trainees and tracheal intubation by consultant anaesthetists in the incidences of sore throat (32.9 vs 32.6%, P=0.84) or hoarseness (35.8 vs 35.2%, P=0.60). Odds ratios and 95% confidence intervals for tracheal intubation by trainees were 1.01 (0.91−1.12) for sore throat and 1.03 (0.93−1.14) for hoarseness. The rates of sustained sore throat and hoarseness over the course were low (P=0.85 and P=0.67, respectively). Hazard ratios and 95% confidence intervals for tracheal intubation by trainees were 0.99 (0.94−1.05) for sustained sore throat and 0.99 (0.93−1.05) for sustained hoarseness. Patient satisfaction did not differ between matched groups (P=0.66 and P=0.83). Conclusions: Tracheal intubation by trainees under the supervision of consultant anaesthetists did not worsen the postoperative airway outcomes, such as sore throat and hoarseness. Key words: airway, complications; complications, tracheal intubation; education, untrained personnel
†
The department and institution to which the work should be attributed: Department of Anesthesiology, Nara Medical University. Accepted: June 7, 2015 © The Author 2015. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: [email protected]
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Tracheal intubation by trainees does not alter the incidence or duration of postoperative sore throat and hoarseness: a teaching hospital-based
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Editor’s key points • It is not clear whether or not physicians’ expertise in tracheal intubation affects the incidence of postoperative throat complications, such as sore throat and hoarseness. • In a retrospective study, in which propensity score matching was made to minimize selection bias on outcomes, there was no difference in the incidences of postoperative throat complications between trainees and anaesthetists. • Regardless of the expertise of the intubator, postoperative throat complications frequently occur after tracheal intubation.
Methods Approval for review of patient clinical charts, access to data of the institutional registry of anaesthesia, and reporting the results was obtained from the Nara Medical University Institutional Review Board (no. 942, approved on October 21, 2014).
Perioperative patient treatment No standardization was made for the methods of induction and maintenance of anaesthesia. General anaesthesia was usually induced with i.v. propofol (1–2.5 mg kg−1) plus either fentanyl (0.1–0.2 μg kg−1) or remifentanil (0.2–0.3 μg kg−1 min−1), and neuromuscular block was achieved with rocuronium (0.6–0.9 mg kg−1). Tracheal intubation was performed using a Macintosh-type laryngoscope (Heine™ Classic+Macintosh Fiber Optic blade; Heine USA Ltd, Dover, NH, USA), and the size of the blade (size 3 or 4) was chosen based on the intubator’s preference and the size of the patient. The polyvinyl chloride tracheal tube
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Postoperative throat complications, such as sore throat and hoarseness, are frequent complications of general anaesthesia with tracheal intubation, with reported incidences of sore throat between 11 and 48% and those of hoarseness between 18 and 53%.1–6 The aetiology of throat complications is believed to involve mucosal erosion caused by the cuff of a tracheal tube,7 trauma from tracheal intubation, and mucosal dehydration.8 Modern anaesthesia practices and improved airway devices have reduced these complications. It is not clear whether or not physicians’ experience affects the incidence of postoperative throat complications A prospectively observational study of 809 adult surgical patients reported that the professional assignment and length of professional experience had no influence on the occurrence or intensity of throat complaints.9 In addition, another study including 266 surgical patients found that the experience of the anaesthetist did not significantly alter the incidence of sore throat.10 On the contrary, a prospective observational study including 495 patients reported that the experience of anaesthesia personnel was independently associated with the incidence of sore throat and hoarseness in male patients.11 It is necessary to conduct a definitive study to resolve these contradictory results. To determine whether throat complications after tracheal intubation are related to the physician’s experience, we retrospectively investigated the incidence and duration of postoperative sore throat and hoarseness. We examined whether tracheal intubation by trainees in anaesthesia altered the incidence or duration of postoperative sore throat and hoarseness.
(Mallinckrodt™ Hi−Lo Oral/Nasal Tracheal Tube Cuffed Murphy Eye; Covidien Japan, Tokyo, Japan) with a silicon-coated stylet (Intubating stylet 14F; Japan Medicalnext Co., Ltd, Osaka, Japan) was lubricated at the site of the cuff using an adequate amount of lubrication gel (KY Jelly™; Johnson & Johnson, Tokyo, Japan). Tracheal tubes with low-pressure–high-volume cuffs of 8.0 mm internal diameter were mainly used for males and tubes and cuffs of 7.0 mm internal diameter for females. Immediately after tracheal intubation, the cuff of the tracheal tube was inflated with the minimal amount of air to prevent an audible leak at the airway pressure of 20 cm H2O. If air leak around the cuff could not be prevented with 10 ml of air, the tube was replaced by a tube one size larger. Intracuff pressure was not monitored. Heat and moisture exchangers (DAR™ Adult-Pediatric Electrostatic Filter HME Small; Covidien Japan) were used for all patients. Lidocaine i.v. or lidocaine gel on the tracheal tube was not used. Tracheal intubations were performed by trainees under the guidance of the registered (consultant) anaesthetist or by the consultant anaesthetist. A trainee was defined as a medical school graduate, who had a medical qualification, in a 2yr mandatory clinical training programme currently on rotation in the anaesthesia department (for a couple of months) or a trainee anaesthetist in a 2yr training programme after the mandatory training. In Japan, anaesthetists can apply for registered anaesthetist status to the Ministry of Health, Labour, and Welfare after 2yr of training as a member of the Japanese Society of Anaesthesiologists. All these trainees have completed a simulation-based training course in airway management and passed the practical examination about airway management. Anaesthesia was maintained with sevoflurane (1.5–2%) in a 40% oxygen and air mixture or with propofol (6–10 mg kg−1 h−1). Nitrous oxide was not used. Fentanyl (0.1–0.2 μg kg−1 h−1) or remifentanil (0.1–0.2 μg kg−1 min−1) was used for analgesia. Rocuronium (0.2–0.3 mg kg−1 h−1) was used for neuromuscular block and sugammadex (2–4 mg kg−1) or neostigmine (40 μg kg−1) plus atropine (20 μg kg–1) for reversal of neuromuscular block. Occasionally, postoperative analgesia was provided by i.v. fentanyl or epidural ropivacaine combined with fentanyl using a patient-controlled analgesia device. After completion of anaesthesia, the attendant in charge filled out the form for the institutional registry of anaesthesia, which includes the attendant’s name, the name of the person who performed tracheal intubation, the patient’s characteristics, information on final diagnosis and surgical procedures (later categorized into three classes based on the modified surgical risk stratification),12 background illnesses (hypertension, diabetes mellitus, coronary artery disease, history of heart failure, and lung disease), duration of anaesthesia and surgery, ASA physical status, urgency of surgery (emergency or elective), anaesthesia technique (inhalation or i.v. with or without regional analgesia), intraoperative patient positioning, final airway assessment, requirement for transfusion, implementation of postoperative analgesia, requirement for postoperative intensive care, and adverse intraoperative events (cardiac events, hypotension, arrhythmia, hypoxia, etc.). The attendant in charge of the patient also followed up the patient and recorded any throat symptoms during several postoperative days. At our institute, surgical patients managed by the anaesthesia department undergo a postoperative structured interview with consultant anaesthestists at the postoperative anaesthesia consultation clinic, where the occurrence of perioperative adverse events is assessed, and the patients can critique perioperative management using a self-report form. Until the
Tracheal intubation by trainees and throat complications
10th postoperative day, patients completed a questionnaire including items on incidence and duration of postoperative sore throat and hoarseness and were requested to rate our perioperative care using a simplified patient satisfaction scale (very satisfactory, satisfactory, even, or dissatisfactory). The incidence and duration of postoperative sore throat were determined by referring to both the patient’s report and the postanaesthetic round record.
Data handling
Statistical analysis Continuous variables are presented as the mean and if normally distributed or the median and interquartile range (IQR) if
All anaesthesia patients n=21 606 Patients missing answers for a postoperative questionnaire n=6391 Remaining patients n=15 215 Use of supraglottic devices n=468 Remaining patients n=14 747 Post-tracheostomy or intubation, or tracheostomy n=597 Remaining patients n=14 150 Patients <15 yr old n=1312 Remaining patients n=12 838 Procedures at the sites including larynx, pharynx, and anterior cervical lesion n=717 Remaining patients n=12 121 Patients missing data sets n=1251 for sore throat n=1861 for hoarseness Remaining patients n=10 870 for sore throat n=10 260 for hoarseness
Fig 1 Flow diagram for patient inclusion and exclusion.
non-parametric. Categorical variables are presented as the number of patients and frequency ( percentage). There is a growing interest in the use of propensity scorebased methods in observational studies to estimate treatment effects. The propensity score is defined as the conditional probability of assigning a subject to a particular treatment protocol given a vector of measured covariates.13 14 To minimize the effect of selection bias on outcomes, we used propensity score matching for clinical characteristics to reduce distortion by confounding factors. Using propensity score analysis, we generated a set of matched cases (tracheal intubations by trainees) and controls (tracheal intubations by consultant anaesthetists). As a result of the propensity score matching, 3940 and 3726 patients were excluded from postoperative sore throat analysis and hoarseness analysis, respectively. A propensity score was generated for each patient from a multivariable logistic regression model based on the covariates using data from the institutional registry as independent variables, with treatment type (tracheal intubation by trainees vs tracheal intubation by consultant anaesthetists) as a binary dependent variable. Factors reported to influence the incidence of postoperative throat symptoms include adequate anaesthesia or relaxation of the patient, tracheal intubation technique, (softer) suction catheters, tracheal tube diameter, cuff tracheal contact area, monitoring and adjustment of intracuff pressure, local anaesthetic or steroid lubricants, preoperative physical condition, sex, age, gynaecological surgery, duration of anaesthesia, and intraoperative patient position.1–6 Tracheal intubation techniques, devices, and conditions were based on institutional protocols and were not monitored. However, other factors may have varied and were included as potential confounders. As suggested by a review of statistical research on propensity score development, we used a structured iterative approach to refine this model, with the goal of achieving covariate balance between the matched pairs.14 Covariate balance was measured using the standardized difference, where an absolute difference of ≥0.1 was accepted as a meaningful covariate imbalance.15 We matched patients using a greedy-matching algorithm with a calliper width of 0.001 of the estimated propensity score. A matching ratio of 1:1 was used. This procedure yielded 3465 patients with sore throat and 3267 patients with hoarseness whose tracheas were intubated by trainees propensity matched to 3465 and 3267 patients whose tracheas were intubated by consultant anaesthetists. For statistical inference, methods that account for the matched nature of the samples were used. For overall incident rate, the Cochran–Mantel–Haenszel test, stratified on the matched pair, was used to estimate the odds ratio and 95% confidence interval (CI) of incidence (tracheal intubation by trainees vs tracheal intubation by consultant anaesthetists). Throat symptoms that had lasted for more than a day were defined as sustained symptoms. Plots of the estimated proportion of patients with sustained sore throat or hoarseness over time were constructed by the Kaplan–Meier method separately for the two groups. Patients with sustained throat symptoms when visiting the postoperative anaesthesia clinic were treated as censored cases. The stratified (by matched pair) log-rank test was used to assess the statistical significance of treatment effects, and the stratified (by matched pair) Cox proportional hazard model was used to estimate the hazard ratio and 95% CI for tracheal intubation by trainees vs tracheal intubation by consultant anaesthetists. In addition, the Wilcoxon signed-rank test was used for the matched pair comparison of the simplified patient satisfaction scale.
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Data were collected between January 2009 and December 2013, during which there were 21 606 patients who underwent general anaesthesia. The exclusion criteria for the present study (and reasons for consequent reductions in eligible patients) were as follows: (i) patients missing answers on the postoperative questionnaire (n=6391); (ii) use of supraglottic devices (n=468); (iii) tracheostomy or postsurgical tracheal intubation (n=597); (iv) patient <15 yr old (n=1312); (v) procedures at the evaluation sites including larynx, pharynx, and anterior cervical lesions (n=717); and (vi) patients missing data sets (n=1251 for sore throat and n=1861 for hoarseness). The final numbers for assessment of sore throat and hoarseness were 10 870 and 10 260 patients, respectively (Fig. 1).
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Sample size calculation For the purpose of sample size calculation, we assumed a 40% incidence of postoperative sore throat or hoarseness based on previous reports (11–53%).1–5 We estimated that 2474 patients in each group were required to provide 95% power to detect a 5% difference in the incidence of sore throat or hoarseness (with an overall incidence of 40%) between tracheal intubation by trainees and tracheal intubation by consultant anaesthetists, with a type I error probability of 0.05. Thus, our sample size was sufficient to
detect a difference in outcome. Analyses were computed using R (version 3.0.3; R Foundation for Statistical Computing, Vienna, Austria). A value of P<0.05 was considered statistically significant.
Results The results, based on 10 870 patients with sore throat and 10 260 with hoarseness, are presented in Supplementary materials. The median (IQR) number of years of experience was 1.8 (1−2.7) for
Table 1 Clinical characteristics of the two study groups after propensity score matching (sore throat). ICU, intensive care unit; IQR, interquartile range Trainee intubation (n=3267)
Anaesthetist intubation (n=3267)
Standardized difference
Age [median (IQR); yr] Height [mean (); cm] Weight [mean (); kg] BMI [mean (); kg m−2] Duration of anaesthesia [mean (); min] Duration of surgery [mean (); min] ASA physical status [median (IQR); I–V] Surgical risk stratification [median (IQR); I–III] Sex (female/male) Inhalation anaesthetics (no/yes) With regional analgesia (no/yes) Supine position (no/yes) Coexisting disease (no/yes) Gynaecology (no/yes) Difficult airway (no/yes) Emergency (no/yes) ICU admission (no/yes) Postoperative analgesia (no/yes) Intraoperative incident (no/yes) Transfusion (no/yes)
64 (49–72) 160.11 (9.17) 58.82 (12.03) 22.87 (3.85) 274.47 (153.24) 208.02 (143.58) II (II–II) II (II–II) 1620/1647 635/2632 2292/975 887/2380 960/2307 2878/389 3117/150 2907/360 2498/769 1692/1575 3253/14 2724/543
64 (49–72) 160.30 (9.06) 59.08 (12.19) 22.90 (3.86) 272.60 (144.86) 207.28 (134.86) II (II–II) II (II–II) 1601/1666 638/2629 2285/982 890/2377 985/2282 2858/409 3113/154 2921/346 2490/777 1714/1553 3257/10 2707/560
0.026 0.021 0.009 0.009 0.013 0.005 0.014 0.005 0.012 0.002 0.005 0.002 0.017 0.019 0.006 0.014 0.006 0.014 0.02 0.014
Table 2 Clinical characteristics of the two study groups after propensity score matching (hoarseness). ICU, intensive care unit; IQR, interquartile range Characteristic
Trainee intubation (n=3267)
Anaesthetist intubation (n=3267)
Standardized difference
Age [median (IQR); yr] Height [mean (); cm] Weight [mean (); kg] BMI [mean (); kg m−2] Duration of anaesthesia [mean (); min] Duration of surgery [mean (); min] ASA physical status [median (IQR); I–V] Surgical risk stratification [median (IQR); I–III] Sex (female/male) Inhalation anaesthetics (no/yes) With regional analgesia (no/yes) Supine position (no/yes) Coexisting disease (no/yes) Gynaecology (no/yes) Difficult airway (no/yes) Emergency (no/yes) ICU admission (no/yes) Postoperative analgesia (no/yes) Intraoperative incident (no/yes) Transfusion (no/yes)
64 (49–73) 160.11 (9.17) 58.82 (12.03) 22.87 (3.85) 274.47 (153.24) 208.02 (143.58) II (I–II) II (II–II) 1620/1647 635/2632 2292/975 887/2380 960/2307 2878/389 3117/150 2907/360 2498/769 1692/1575 3253/14 2724/543
63 (49–72) 160.30 (9.06) 59.08 (12.19) 22.90 (3.86) 272.60 (144.86) 207.28 (134.86) II (II–II) II (II–II) 16 016/1666 638/2629 2285/982 890/2377 985/2282 2858/409 3113/154 2921/346 2490/777 1714/1553 3257/10 2707/560
0.026 0.021 0.009 0.009 0.013 0.005 0.014 0.005 0.012 0.002 0.005 0.002 0.017 0.019 0.006 0.014 0.006 0.014 0.02 0.014
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Characteristic
Tracheal intubation by trainees and throat complications
also confirmed that patient satisfaction with perioperative care was not affected by who performed intubation.
Discussion The incidence and duration of postoperative sore throat and hoarseness did not differ between patients who underwent general anaesthesia whose tracheas were intubated by trainees and those whose tracheas were intubated by consultant anaesthetists. Additionally, patient satisfaction did not differ between those whose tracheas were intubated by trainees and those whose tracheas were intubated by consultant anaesthetists. This study suggests that patients receive equal medical care regarding airway management in teaching hospitals because trainees are appropriately trained before participating in airway management, including manikin training, and are closely supervised by a consultant anaesthetist throughout the tracheal intubation process. The incidence of airway complications is thought to depend on the experience of the attending physician. It has been reported that the incidence of multiple tracheal intubation
Table 3 Patient outcome after propensity matching. CI, confidence interval; IQR, interquartile range; NA, not applicable Outcome
Trainee intubation
Anaesthetist intubation
Odds ratio (95% CI)
Effect size
P-value
Incidence of sore throat (yes/no) Satisfaction scale in population for sore throat [median (IQR)] Incidence of hoarseness (yes/no) Satisfaction scale in population for hoarseness [median (IQR)]
1139/2326 4 (3–4) (n=3465)
1130/2335 4 (3–4) (n=3465)
1.01 (0.91–1.12) NA
0.01 0.02
0.84 0.66
1171/2096 4 (3–4) (n=3267)
1150/2117 4 (3–4) (n=3267)
1.03 (0.93–1.14) NA
0.01 0.01
0.60 0.83
Sore throat after adjustment
Rate of sustained sore throat
1.0 Consultant anaesthetist intubation 0.8
Trainee intubation
0.6
0.4 Hazard ratio 0.99
0.2
95% Cl 0.94–1.05
P-value 0.85
0.5% Trainee 0.7% Anaesthetist
0.0 0
2
4
6
8
10
75 68
30 22
24 18
Days Number at risk Anaesthetist 3465 Trainee 3465
803 840
196 197
Fig 2 Curves for the rate of sustained sore throat after adjustment. Blue line shows tracheal intubation by consultant anaesthetists. Green line shows tracheal intubation by trainees. Tick marks indicate censored cases. CI, confidence interval.
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trainees and 13 (9−18) for consultant anaesthetists. The clinical characteristics of the two matched groups ( patients whose tracheas were intubated by trainees and patients whose tracheas were intubated by consultant anaesthetists) extracted by propensity analysis are presented in Tables 1 and 2. According to the standardized difference, covariate balance between the matched pairs was confirmed. Patient outcomes are summarized in Table 3 and Figs 2 and 3. The incidence of sore throat did not differ between tracheal intubation by trainees and tracheal intubation by consultant anaesthetists after propensity matching (32.9 vs 32.6%, respectively). Likewise, there was no difference in the incidence of hoarseness (35.8 vs 35.2%, respectively). In addition, tracheal intubation by trainees did not increase the rates of sustained sore throat and hoarseness, and Kaplan–Meier curves for sustained rate of sore throat were similar. The number of censored cases was 41 (0.6%) for sore throat and 356 (5.4%) for hoarseness. The rates of sustained sore throat and hoarseness on the 10th postoperative day were very low (0.5 vs 0.7 and 3.9 vs 3.3%, respectively). Hazard ratios for tracheal intubation by trainees for sore throat and hoarseness were both almost one. Finally, it was
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Hoarseness after adjustment
Rate of sustained hoarseness
1.0
Consultant anaesthetist intubation Trainee intubation
0.8 0.6 P-value 0.67
Hazard ratio 95% Cl 0.99 0.93–1.05
0.4 0.2
0
2
4
6
8
10
124 145
72 85
64 70
Days Number at risk Anaesthetist Trainee
3267 3267
782 796
239 255
Fig 3 Curves for the rate of sustained hoarseness after adjustment. Blue line shows tracheal intubation by consultant anaesthetists. Green line shows tracheal intubation by trainees. Tick marks indicate censored cases. CI, confidence interval.
attempts, which increases the risk of complications, depends on the years of training and type of residency, and that airway complications decrease significantly when supervised by experienced consultant anaesthetists in a critical care setting.16 17 Therefore, postoperative throat complications are generally believed to be more frequent in patients whose tracheas are intubated by less experienced physicians because of lack of careful technique.1 It is still a matter of debate whether the experience of the anaesthetist can alter the postoperative incidence of throat complications.9–11 It has been suggested that training on a manikin during the early phase of employment may improve the technique and thereby reduce the risk of such airway complications.11 It is therefore reasonable to suppose that completion of our simulation-based training programme before commencement of clinical activity and tracheal intubation by trainees under supervision by consultant anaesthetists favourably affected throat outcomes. Patients who are dissatisfied are known to experience more adverse events attributable to medical practice.18 19 It is therefore reasonable to suppose that postoperative sore throat and hoarseness could significantly impact the overall patient experience of anaesthesia management, during which patients are almost unconscious, if patients consider these minor adverse events as partial outcomes of anaesthesia management. Thus, it may be logical that tracheal intubation by trainees did not reduce patient satisfaction in the present study. This study has a number of limitations. Some data known to influence postoperative outcomes, such as the number of attempts at tracheal intubation, measurement of intracuff pressure, tracheal tube diameter, presence of upper respiratory infection, and multiple attempts at suctioning, were not available. We did not distinguish between the various aetiologies of sore throat. We also did not set a precise follow-up period, so patients who still complained of throat symptoms were censored when they visited the postoperative anaesthesia consultation
clinic. This study relied on patient self-reports to determine the duration of symptoms, which were based on memory, and may have influenced the results. This study was retrospective in nature; thus, unmeasured variables could still confound the results. Finally, a considerable number of patients were excluded from the study. In conclusion, trainee tracheal intubation under the supervision of consultant anaesthetists did not worsen postoperative throat symptoms compared with tracheal intubation by consultant anaesthetists. Patient satisfaction with perioperative care also did not differ, regardless of who performed tracheal intubation.
Authors’ contributions Study design and writing of the first draft of the paper: S.I. Data collection: S.I., R.A. Data analysis: S.I., Y.T. Reviewing the first draft of the paper and rewriting: M.K.
Supplementary material Supplementary material is available at British Journal of Anaesthesia online.
Acknowledgements The authors would like to thank Enago (www.enago.jp) for English language review.
Declaration of interest None declared.
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3.9% Trainee 3.3% Anaesthetist
0.0
Tracheal intubation by trainees and throat complications
Funding Departmental resources.
References
12. Eagle KA, Berger PB, Calkins H, et al. ACC/AHA guideline update for perioperative cardiovascular evaluation for noncardiac surgery—executive summary. A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1996 Guidelines on Perioperative Cardiovascular Evaluation for Noncardiac Surgery). Circulation 2002; 105: 1257–67 13. D’Agostino RB Jr. Propensity score methods for bias reduction in the comparison of a treatment to a non-randomised control group. Stat Med 1998; 17: 2265–81 14. Austin PC. Propensity-score matching in the cardiovascular surgery literature from 2004 to 2006: a systematic review and suggestions for improvement. J Thorac Cardiovasc Surg 2007; 134: 1128–35 15. Austin PC, Grootendorst P, Anderson GM. A comparison of the ability of different propensity score models to balance measured variables between treated and untreated subjects: a Monte Carlo study. Stat Med 2007; 26: 734–53 16. Hirsch-Allen AJ, Ayas N, Mountain S, Dodek P, Peets A, Griesdale DE. Influence of residency training on multiple attempts at endotracheal intubation. Can J Anaesth 2010; 57: 823–9 17. Schmidt UH, Kumwilaisak K, Bittner E, George E, Hess D. Effects of supervision by attending anesthesiologists on complications of emergency tracheal intubation. Anesthesiology 2008; 109: 973–7 18. Taylor BB, Marcantonio ER, Pagovich O, et al. Do medical inpatients who report poor service quality experience more adverse events and medical errors? Med Care 2008; 46: 224–8 19. Weingart SN, Pagovich O, Sands DZ, et al. What can hospitalised patients tell us about adverse events? Learning from patient-reported incidents. J Gen Intern Med 2005; 20: 830–6
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