- Email: [email protected]
Anatomic landmark versus ultrasound approach to crycothyroidotomy: The author responds
1696
Correspondence / American Journal of Emergency Medicine 34 (2016) 1673–1730
When ultrasound approach is worse, something is suspicious…
Anatomic landmark versus ultrasound approach to crycothyroidotomy: The author responds
To the Editor,
To the Editor,
Yildiz et al reported the comparison of ultrasound (US) vs anatomic landmark to locate cricothyroid membrane (CTM). Despite the quality of the study, we think that no definitive conclusion should be done. Crucial precisions on methods are missing, and potential biases are challenging results. First, the way investigators adjudicated the accuracy is not described. As shown on the figure, the CTM is not a point but an area of several millimeters. Was it defined as a line or a surface? What was the accepted location of selected point? Apart from the fact that “lateral approach” of CTM is not commonly described, investigators were not blinded to the procedure. The number of operators was dramatically low. Consequently, interoperator reproducibility of the procedure has not been tested. According to described methods, the operator performed US first and palpation second, without randomization. The accuracy should be better in the second case. If junior physicians are experimented in patient palpation, they are naive in US. Therefore, a crucial result is missing: the evolution of the accuracy with the number of examinations performed. In other words, as the procedure was repeated more than 20 times, a “learning curve” should be presented. The mean time for detecting CTM with US in the last 5 procedures (ie, after 19 procedures of training) should be reported. It should also be underlined that authors have described methods using a Sonosite device, whereas the figure shown seems to have been obtained with a Mindray one. As concluded by Yildiz et al, the lack of practice is detrimental to performance. This is independent of the technique used. US certainly requires a preliminary apprenticeship. It might then offer, as consideration, a greater sensitivity for achieving an act sometimes made difficult by unfavorable anatomy conditions that avoid proper identification of usual landmarks. Most of the studies published in the last decades reported improvement of care through US use. Such a negative result as reported is very uncommon. It could be a rare defeat of US. It might also be the more frequent defeat of a methodology.
We would like to thank Dr Pes et al for their contribution to our study [1]. As the authors of this study, we would like to respond to the points that they raised regarding our manuscript [2]. As we have mentioned in the study protocol section of our manuscript, researchers other than the participants (operators) identified the borders of cricothyroid membrane (CTM), and the borders of the CTM were marked with an invisible pen. The CTM was defined as a surface, but the operators used a point estimate with a board marker; the details of this are mentioned in the ‘Methods’ section of the manuscript [2]. Dr Pes et al stated that the “lateral approach” of CTM is not commonly described [3–5]. However, numerous previous studies had described the ‘lateral approach’ as the method of identifying the point estimate for cricothyroidotomy procedure. This approach is especially helpful in elderly patients with thin prevertebral soft tissue and in patients with a prominent ‘Adam apple’. In addition, the authors stated that “operators were not blind to the procedure”; we believe that the authors will appreciate that it is not possible to be blind to the procedure in this and in similar study designs. Nevertheless, in our study the borders of CTM were identified by researchers other than the participants (operators). In this manner, the risk of bias was reduced in our study, but in certain similar previous studies trying to identify the CTM with ultrasound (US), some of the participants were both operators and models [4], whereas in others, the operators directly decided the proper position of the CTM without a control mechanism [3]. The authors stated that the number of operators was dramatically low, although the number of operators in the study of Curtis et al [5] was 2, while in the study of Nicholls et al [3] it was also 2, and in the study of Mallin et al [4] this number was 23, including both operators and models. We prefer to include those operators who had received formal US training by the Emergency Medicine Association of Turkey. Airway US, other than proper identification of endotracheal tube position, is a new procedure for the operators. We do not believe that the operators in this study are “naïve”, as the success rate of routine daily practice of US, such as FAST examination, cardiac or pulmonary US, or DVT examination is not different from the documented percentages in the literature. However, the need for surgical airway is extremely rare and it is not possible to have a US fellow in the EDs 24 hours a day. We believe that the selection of participants is more realistic for emergency medicine perspective. In this respect, Dr Pes et al are right; we should have randomized the sequence of US and palpation. Methodology is the most important part of a study design. Whatever researchers try to do, the circumstances related to the study can make bias inevitable. This notwithstanding, we believe that we tried to minimize the risk of bias. If you look at the title of the letter, “When ultrasound approach is worse, something is suspicious…” it also expresses the bias of the authors. During the preparation phase of our manuscript we decided to put the photos in the manuscript, but the Sonosite US machine was out of order and we were using the Mindray one.
Ph. Pes, MD* I. Arnaudet, MD SAMU 44, Pôle Urgences et Soins Critiques, 1 Quai Moncousu 44 093, Nantes Cedex *Corresponding author. E-mail address: [email protected] T. Petrovic, MD SAMU 93, UF Recherche-Enseignement-Qualité, Université Paris 13 Sorbonne Cité, EA 3509, Hôpital Avicenne, 125, rue de Stalingrad 93009 Bobigny, France J. Jenvrin, MD SAMU 44, Pôle Urgences et Soins Critiques, 1 Quai Moncousu 44 093, Nantes Cedex C. Perrier, MD Pôle Urgences, SAMU-SMUR, CHU Clermont Ferrand 63000, Clermont-Ferrand P.G. Reuter, MD F. Lapostolle, MD, PhD SAMU 93, UF Recherche-Enseignement-Qualité, Université Paris 13 Sorbonne Cité, EA 3509, Hôpital Avicenne, 125, rue de Stalingrad 93009 Bobigny, France http://dx.doi.org/10.1016/j.ajem.2016.05.018
E. Goksu, M.D. Akdeniz University School of Medicine, Department of Emergency Medicine Antalya, Turkey Corresponding author at: Akdeniz University School of Medicine Department of Emergency Medicine, 07059, Antalya, Turkey Tel.: +90 505 4691764 E-mail address: [email protected]
Correspondence / American Journal of Emergency Medicine 34 (2016) 1673–1730
G. Yildiz, MD Kilis State Hospital, Kilis, Turkey
http://dx.doi.org/10.1016/j.ajem.2016.06.048
References [1] Pes P, Arnaudet I, Petrovic T, Jenvrin J, Perrier C, Reuter PG, et al. When ultrasound approach is worse, something is suspicious…. Am J Emerg Med 2016;34(8):1696. http://dx.doi.org/10.1016/j.ajem.2016.05.018. [2] Yıldız G, Göksu E, Şenfer A, Kaplan A. Comparison of ultrasonography and surface landmarks in detecting the localization for cricothyroidotomy. Am J Emerg Med 2016;34(2):254–6. [3] Nicholls SE, Sweeney TW, Ferre RM, Strout TD. Bedside sonography by emergency physicians for the rapid identification of landmarks relevant to cricothyrotomy. Am J Emerg Med 2008;26(8):852–6. [4] Mallin M, Curtis K, Dawson M, Ockerse P, Ahern M. Accuracy of ultrasound-guided marking of the cricothyroid membrane before simulated failed intubation. Am J Emerg Med 2014;32(1):61–3. [5] Curtis K, Ahern M, Dawson M, Mallin M. Ultrasound-guided, Bougie-assisted cricothyroidotomy: a description of a novel technique in cadaveric models. Acad Emerg Med 2012;19(7):876–9.
Application of LMA Classic for anesthetized, paralyzed children weighing 20 kg: comparison between size 2 and size 2.5☆,☆☆
To the Editor, Laryngeal mask airway (LMA) Classic can provide many advantages especially in pediatric patients undergoing short-term surgery, for example, eye surgery [1,2]. As recommended by manufacturers' instruction, children weighing exactly 20 kg can receive either size 2 or size 2.5 LMA; unfortunately, it remains confusing to select appropriate size of LMA in children weighing exactly 20 kg. An initial inappropriate size choice might increase the wastage; most importantly, it will increase the risk of hypoxemia due to reduced apnea tolerance in children [3]. Thus, it is necessary to look at the suitability of these sizes in the population of 20-kg children. After receiving approval from the Ethics Committee of Zhongshan Ophthalmic Center of Sun Yat-sen University (Guangzhou, China), written consent was obtained from the parents. Eighty-eight children weighing 20 kg aged from 3 to 8 years and with American Society of Anesthesiologists physical status 1 or 2 undergoing eye surgical procedures were initially enrolled in this study, and 80 patients were found eligible and randomized into 2 groups (group size 2 and 2.5) by using a computer-generated randomization program. Patients in the size 2 and size 2.5 groups were inserted size 2 and size 2.5 LMA, respectively. Anesthesia induction was achieved with intravenous 2.5 mg/kg propofol and 2 μg/kg fentanyl and 0.1 mg/kg of cisatracurium for neuromuscular blockade. LMA was inserted 3 minutes after cisatracurium administration, and anesthesia was maintained by inhaling 3% of sevoflurane in 80% oxygen with air through LMA.
☆ The authors declare that there are no conflicts of interest related to the subject matter or materials discussed in this article. ☆☆ Institutional Review Board: Name: Zhongshan Ophthalmic Center, Tel.: +86 20 87,332,702; fax: +86 20 87,334,825. Address: Xianlie South Rd 54#, Guangzhou, Guangdong, 510,060, China. Email: [email protected].
1697
Table 1 Patient characteristics and demographic data
Age (y) Height (cm) ASA physical status (1/2) Male-female Thyromental distance (cm) Sternomental distance (cm) Mallampati score (1/2) Mouth opening (mm) Duration of anesthesia (min) Duration of surgery (min)
Size 2 group (n = 40)
Size 2.5 group (n = 40)
P value
5.3 ± 1.2 114.0 ± 6.2 38/2 25/15 5.7 ± 0.5 9.7 ± 0.9 29/11 32.9 ± 3.6 59.6 ± 22.8 39.1 ± 20.3
5.7 ± 1.6 113.5 ± 8.2 37/3 22/18 6.0 ± 0.6 10.1 ± 1.2 27/13 33.4 ± 4.7 60.4 ± 22.9 43.7 ± 21.2
.219 .759 1.000 .563 .057 .106 .807 .594 .868 .323
Data were expressed as means (SD). ASA: American Society of Anesthesiologists.
Before insertion, all of the LMAs were with resting volume, and all insertions were performed by the same experienced anesthesiologist in rotational method [4] without lubricant. The cuff was inflated with air to a pressure of 60 cm H2O by a cuff inflator pressure manometer. The primary outcome was oropharyngeal leak pressure (OLP). OLP was measured by closing the expiratory valve of the circle system at a fixed gas flow of 3 L/min and noting the airway pressure (maximum allowed, 30 cm H2O) at which equilibrium was reached. The secondary outcomes included insertion time, ease of insertion [5], and incidences of 2 and more insertion attempts, as well as peak airway pressure during ventilation and mucosa injury after removal of LMA. After the OLP measurement, the image from a flexible fiber-optic bronchoscope (Olympus Optical Co, Tokyo, Japan) through the airline channel was evaluated for the inserted positions of LMA [6]. When these measurements were completed, the patients were ventilated, and the peak airway pressure was recorded during controlled ventilation. Mucosa injury was defined as the detection of visible blood stain in LMA. Patients were also questioned about the presence/absence of sore throat 18-24 hours postoperatively by an investigator who was blinded to the LMA insertion. Statistical analysis was performed with SPSS 13.0 (IBM, Armonk, NY). Continuous data were expressed as the means ± SD and compared with independent t tests. Categorical data were expressed as frequencies or percentages and compared with Fisher exact test. A P value of less than .05 was considered statistically significant. In the present study, there were no significant differences in age, height, body mass index, thyromental distance, sternomental distance, and mouth opening as well as Mallampati score between 2 groups (Table 1). Furthermore, the anesthesia time and surgery time did not differ statistically (Table 1). The OLP in the size 2.5 group was slightly but significantly increased as compared with that in the size 2 group (P = .038, Table 2); however, the insertion time, incidence of 2 and more insertion attempts, and ease of insertion were not significantly different (Table 2). Furthermore, none of patients suffered insertion failure in the size 2.5 group, and in only 1 patient with height of 135 cm in the size 2 group, adequate ventilation was not provided even on the third attempt. Device placement was considered unsuccessful, and the patient was successfully ventilated when inserted with size 2.5 LMA. And there were no significant differences in the incidences of insertion failure. Notably, fiber-optic grading and peak airway pressure during controlled ventilation were comparable between both groups (P N .05, Table 2). The incidences of blood staining observed on the LMA at removal were displayed to be comparable between the size 2 group and the size 2.5 group (P N .05, Table 2). The incidences
Correspondence / American Journal of Emergency Medicine 34 (2016) 1673–1730
When ultrasound approach is worse, something is suspicious…
Anatomic landmark versus ultrasound approach to crycothyroidotomy: The author responds
To the Editor,
To the Editor,
Yildiz et al reported the comparison of ultrasound (US) vs anatomic landmark to locate cricothyroid membrane (CTM). Despite the quality of the study, we think that no definitive conclusion should be done. Crucial precisions on methods are missing, and potential biases are challenging results. First, the way investigators adjudicated the accuracy is not described. As shown on the figure, the CTM is not a point but an area of several millimeters. Was it defined as a line or a surface? What was the accepted location of selected point? Apart from the fact that “lateral approach” of CTM is not commonly described, investigators were not blinded to the procedure. The number of operators was dramatically low. Consequently, interoperator reproducibility of the procedure has not been tested. According to described methods, the operator performed US first and palpation second, without randomization. The accuracy should be better in the second case. If junior physicians are experimented in patient palpation, they are naive in US. Therefore, a crucial result is missing: the evolution of the accuracy with the number of examinations performed. In other words, as the procedure was repeated more than 20 times, a “learning curve” should be presented. The mean time for detecting CTM with US in the last 5 procedures (ie, after 19 procedures of training) should be reported. It should also be underlined that authors have described methods using a Sonosite device, whereas the figure shown seems to have been obtained with a Mindray one. As concluded by Yildiz et al, the lack of practice is detrimental to performance. This is independent of the technique used. US certainly requires a preliminary apprenticeship. It might then offer, as consideration, a greater sensitivity for achieving an act sometimes made difficult by unfavorable anatomy conditions that avoid proper identification of usual landmarks. Most of the studies published in the last decades reported improvement of care through US use. Such a negative result as reported is very uncommon. It could be a rare defeat of US. It might also be the more frequent defeat of a methodology.
We would like to thank Dr Pes et al for their contribution to our study [1]. As the authors of this study, we would like to respond to the points that they raised regarding our manuscript [2]. As we have mentioned in the study protocol section of our manuscript, researchers other than the participants (operators) identified the borders of cricothyroid membrane (CTM), and the borders of the CTM were marked with an invisible pen. The CTM was defined as a surface, but the operators used a point estimate with a board marker; the details of this are mentioned in the ‘Methods’ section of the manuscript [2]. Dr Pes et al stated that the “lateral approach” of CTM is not commonly described [3–5]. However, numerous previous studies had described the ‘lateral approach’ as the method of identifying the point estimate for cricothyroidotomy procedure. This approach is especially helpful in elderly patients with thin prevertebral soft tissue and in patients with a prominent ‘Adam apple’. In addition, the authors stated that “operators were not blind to the procedure”; we believe that the authors will appreciate that it is not possible to be blind to the procedure in this and in similar study designs. Nevertheless, in our study the borders of CTM were identified by researchers other than the participants (operators). In this manner, the risk of bias was reduced in our study, but in certain similar previous studies trying to identify the CTM with ultrasound (US), some of the participants were both operators and models [4], whereas in others, the operators directly decided the proper position of the CTM without a control mechanism [3]. The authors stated that the number of operators was dramatically low, although the number of operators in the study of Curtis et al [5] was 2, while in the study of Nicholls et al [3] it was also 2, and in the study of Mallin et al [4] this number was 23, including both operators and models. We prefer to include those operators who had received formal US training by the Emergency Medicine Association of Turkey. Airway US, other than proper identification of endotracheal tube position, is a new procedure for the operators. We do not believe that the operators in this study are “naïve”, as the success rate of routine daily practice of US, such as FAST examination, cardiac or pulmonary US, or DVT examination is not different from the documented percentages in the literature. However, the need for surgical airway is extremely rare and it is not possible to have a US fellow in the EDs 24 hours a day. We believe that the selection of participants is more realistic for emergency medicine perspective. In this respect, Dr Pes et al are right; we should have randomized the sequence of US and palpation. Methodology is the most important part of a study design. Whatever researchers try to do, the circumstances related to the study can make bias inevitable. This notwithstanding, we believe that we tried to minimize the risk of bias. If you look at the title of the letter, “When ultrasound approach is worse, something is suspicious…” it also expresses the bias of the authors. During the preparation phase of our manuscript we decided to put the photos in the manuscript, but the Sonosite US machine was out of order and we were using the Mindray one.
Ph. Pes, MD* I. Arnaudet, MD SAMU 44, Pôle Urgences et Soins Critiques, 1 Quai Moncousu 44 093, Nantes Cedex *Corresponding author. E-mail address: [email protected] T. Petrovic, MD SAMU 93, UF Recherche-Enseignement-Qualité, Université Paris 13 Sorbonne Cité, EA 3509, Hôpital Avicenne, 125, rue de Stalingrad 93009 Bobigny, France J. Jenvrin, MD SAMU 44, Pôle Urgences et Soins Critiques, 1 Quai Moncousu 44 093, Nantes Cedex C. Perrier, MD Pôle Urgences, SAMU-SMUR, CHU Clermont Ferrand 63000, Clermont-Ferrand P.G. Reuter, MD F. Lapostolle, MD, PhD SAMU 93, UF Recherche-Enseignement-Qualité, Université Paris 13 Sorbonne Cité, EA 3509, Hôpital Avicenne, 125, rue de Stalingrad 93009 Bobigny, France http://dx.doi.org/10.1016/j.ajem.2016.05.018
E. Goksu, M.D. Akdeniz University School of Medicine, Department of Emergency Medicine Antalya, Turkey Corresponding author at: Akdeniz University School of Medicine Department of Emergency Medicine, 07059, Antalya, Turkey Tel.: +90 505 4691764 E-mail address: [email protected]
Correspondence / American Journal of Emergency Medicine 34 (2016) 1673–1730
G. Yildiz, MD Kilis State Hospital, Kilis, Turkey
http://dx.doi.org/10.1016/j.ajem.2016.06.048
References [1] Pes P, Arnaudet I, Petrovic T, Jenvrin J, Perrier C, Reuter PG, et al. When ultrasound approach is worse, something is suspicious…. Am J Emerg Med 2016;34(8):1696. http://dx.doi.org/10.1016/j.ajem.2016.05.018. [2] Yıldız G, Göksu E, Şenfer A, Kaplan A. Comparison of ultrasonography and surface landmarks in detecting the localization for cricothyroidotomy. Am J Emerg Med 2016;34(2):254–6. [3] Nicholls SE, Sweeney TW, Ferre RM, Strout TD. Bedside sonography by emergency physicians for the rapid identification of landmarks relevant to cricothyrotomy. Am J Emerg Med 2008;26(8):852–6. [4] Mallin M, Curtis K, Dawson M, Ockerse P, Ahern M. Accuracy of ultrasound-guided marking of the cricothyroid membrane before simulated failed intubation. Am J Emerg Med 2014;32(1):61–3. [5] Curtis K, Ahern M, Dawson M, Mallin M. Ultrasound-guided, Bougie-assisted cricothyroidotomy: a description of a novel technique in cadaveric models. Acad Emerg Med 2012;19(7):876–9.
Application of LMA Classic for anesthetized, paralyzed children weighing 20 kg: comparison between size 2 and size 2.5☆,☆☆
To the Editor, Laryngeal mask airway (LMA) Classic can provide many advantages especially in pediatric patients undergoing short-term surgery, for example, eye surgery [1,2]. As recommended by manufacturers' instruction, children weighing exactly 20 kg can receive either size 2 or size 2.5 LMA; unfortunately, it remains confusing to select appropriate size of LMA in children weighing exactly 20 kg. An initial inappropriate size choice might increase the wastage; most importantly, it will increase the risk of hypoxemia due to reduced apnea tolerance in children [3]. Thus, it is necessary to look at the suitability of these sizes in the population of 20-kg children. After receiving approval from the Ethics Committee of Zhongshan Ophthalmic Center of Sun Yat-sen University (Guangzhou, China), written consent was obtained from the parents. Eighty-eight children weighing 20 kg aged from 3 to 8 years and with American Society of Anesthesiologists physical status 1 or 2 undergoing eye surgical procedures were initially enrolled in this study, and 80 patients were found eligible and randomized into 2 groups (group size 2 and 2.5) by using a computer-generated randomization program. Patients in the size 2 and size 2.5 groups were inserted size 2 and size 2.5 LMA, respectively. Anesthesia induction was achieved with intravenous 2.5 mg/kg propofol and 2 μg/kg fentanyl and 0.1 mg/kg of cisatracurium for neuromuscular blockade. LMA was inserted 3 minutes after cisatracurium administration, and anesthesia was maintained by inhaling 3% of sevoflurane in 80% oxygen with air through LMA.
☆ The authors declare that there are no conflicts of interest related to the subject matter or materials discussed in this article. ☆☆ Institutional Review Board: Name: Zhongshan Ophthalmic Center, Tel.: +86 20 87,332,702; fax: +86 20 87,334,825. Address: Xianlie South Rd 54#, Guangzhou, Guangdong, 510,060, China. Email: [email protected].
1697
Table 1 Patient characteristics and demographic data
Age (y) Height (cm) ASA physical status (1/2) Male-female Thyromental distance (cm) Sternomental distance (cm) Mallampati score (1/2) Mouth opening (mm) Duration of anesthesia (min) Duration of surgery (min)
Size 2 group (n = 40)
Size 2.5 group (n = 40)
P value
5.3 ± 1.2 114.0 ± 6.2 38/2 25/15 5.7 ± 0.5 9.7 ± 0.9 29/11 32.9 ± 3.6 59.6 ± 22.8 39.1 ± 20.3
5.7 ± 1.6 113.5 ± 8.2 37/3 22/18 6.0 ± 0.6 10.1 ± 1.2 27/13 33.4 ± 4.7 60.4 ± 22.9 43.7 ± 21.2
.219 .759 1.000 .563 .057 .106 .807 .594 .868 .323
Data were expressed as means (SD). ASA: American Society of Anesthesiologists.
Before insertion, all of the LMAs were with resting volume, and all insertions were performed by the same experienced anesthesiologist in rotational method [4] without lubricant. The cuff was inflated with air to a pressure of 60 cm H2O by a cuff inflator pressure manometer. The primary outcome was oropharyngeal leak pressure (OLP). OLP was measured by closing the expiratory valve of the circle system at a fixed gas flow of 3 L/min and noting the airway pressure (maximum allowed, 30 cm H2O) at which equilibrium was reached. The secondary outcomes included insertion time, ease of insertion [5], and incidences of 2 and more insertion attempts, as well as peak airway pressure during ventilation and mucosa injury after removal of LMA. After the OLP measurement, the image from a flexible fiber-optic bronchoscope (Olympus Optical Co, Tokyo, Japan) through the airline channel was evaluated for the inserted positions of LMA [6]. When these measurements were completed, the patients were ventilated, and the peak airway pressure was recorded during controlled ventilation. Mucosa injury was defined as the detection of visible blood stain in LMA. Patients were also questioned about the presence/absence of sore throat 18-24 hours postoperatively by an investigator who was blinded to the LMA insertion. Statistical analysis was performed with SPSS 13.0 (IBM, Armonk, NY). Continuous data were expressed as the means ± SD and compared with independent t tests. Categorical data were expressed as frequencies or percentages and compared with Fisher exact test. A P value of less than .05 was considered statistically significant. In the present study, there were no significant differences in age, height, body mass index, thyromental distance, sternomental distance, and mouth opening as well as Mallampati score between 2 groups (Table 1). Furthermore, the anesthesia time and surgery time did not differ statistically (Table 1). The OLP in the size 2.5 group was slightly but significantly increased as compared with that in the size 2 group (P = .038, Table 2); however, the insertion time, incidence of 2 and more insertion attempts, and ease of insertion were not significantly different (Table 2). Furthermore, none of patients suffered insertion failure in the size 2.5 group, and in only 1 patient with height of 135 cm in the size 2 group, adequate ventilation was not provided even on the third attempt. Device placement was considered unsuccessful, and the patient was successfully ventilated when inserted with size 2.5 LMA. And there were no significant differences in the incidences of insertion failure. Notably, fiber-optic grading and peak airway pressure during controlled ventilation were comparable between both groups (P N .05, Table 2). The incidences of blood staining observed on the LMA at removal were displayed to be comparable between the size 2 group and the size 2.5 group (P N .05, Table 2). The incidences