Gao Pu Liu

Acupuncture for Pain Relief After Total Knee Arthroplasty: A Call for Clarification.

delivery system is measured over time and compared with 2 dosing strategies of OTMF. Whereas purchasing the bolus device represents a 1-time fixed cost, the cumulative cost of OTMF compounds over time. With once-daily, lowest-dose OTMF (squares), cost equivalence occurs after 2.75 months of continuous use, and after only 12 days when using 7 daily doses of OTMF (circles), a strategy most similar to the study population. Letters to the Editor Regional Anesthesia and Pain Medicine • Volume 40, Number 5, September-October 2015

Comparing intubation performance of Bonfils fiberscope and fiberoptic bronchoscope in difficult pediatric airways.

SIR—The recent article by Kaufmann et al. (1) comparing performance of the Bonfils fiberscope (Bonfils) and the fiberoptic bronchoscope (FOB) for tracheal intubation in difficult pediatric airways was of great interest to us. Their findings have potential implications for selection of fiberoptic intubation tools in managing the difficult pediatric airway. In our view, however, there are several aspects of this study that need to be clarified. First, in their study design, Kaufmann et al. stated that the intubation procedure using the Bonfils or the FOB was started following confirmation of a difficult intubation by repeated direct laryngoscopy in anesthetized, paralyzed children. According to definitions of difficult pediatric airways (2), all airway problems included in this study should be classified into unexpected difficult airway. However, in their Table 1, most of the studied patients were classified as expected difficult airway. We are very interested in knowing the inclusion criterion of expected difficult airway used in this study and how the author differentiated the expected and unexpected difficult airways in their study design. Did difficult intubation with direct laryngoscopy occur in all 21 children with preoperatively suspected difficult airways? Second, in the intubation technique, Kaufmann et al. described: ‘After oral suctioning, if required and visualization of the larynx, the Bonfils was placed under continuous visualization into the middle of the trachea. While an assistant then fixed the tube, the Bonfils was removed’. Due to the narrow pediatric trachea and a 40-degree curved tip of the Bonfils, it is impossible to advance the Bonfils into the middle of the trachea. With the blade of the direct laryngoscope in position, the anesthesiologist often introduces the Bonfils with the right hand in the midline and advances it until its tip reaches the glottis. Then, the tracheal tube is advanced into the trachea along with the stylet of the Bonfils under direct vision (3). We caution against the technique of advancing the tip of the Bonfils through the glottis, because the risk of the laryngeal and tracheal injuries may increase. Furthermore, the time required to obtain the best laryngeal view was not significantly different between the two groups. However, the time required for advancement and correct placement of the tracheal tube into the trachea in the FOB group was more two times of that in the Bonfils group. Apart from the one case where the tracheal tube was accidentally lodged against an arytenoid cartilage while advancing through the glottis, we would like to know what other factors resulted in this prolonged intubation time with the FOB. We believe that such information would be helpful for others who would like to try tracheal intubation using the FOB in pediatric patients with difficult airways. Lastly, this study included pediatric patients with a great age range (0–16 years) and difficult airways due to different factors. As the authors had pointed out in their study limitations, early termination of the study had lowered the power of the study. For example, this study was not powered to show possible differences between the two groups in some of demographic data and difficult airway characteristics, such as age, weight, underlying causes of difficult airways, incidence of restricted mouth opening, average mouth opening, etc. Thus, we cannot exclude the possibility that any imbalance in the above factors would have confounded interpretation of their results.

Assessing risk factors for in-hospital acute myocardial infarction after total joint arthroplasty

To the Editor, With great interest we read the recent article by Menendez et al. [1] assessing risk factors for in-hospital acute myocardial infarction (AMI) after total joint arthroplasty in a retrospective cohort study. They showed that advanced age, male gender, Elixhauser comorbidity score, total joint arthroplasty, low household income, history of cardiac disease, valvular disease, diabetes, pulmonary circulation disorders, cerebrovascular disease, peripheral vascular disorders, coagulopathy, AIDS/HIV infection, deficiency anaemia, fluid and electrolyte disorders and the occurrence of concomitant post-operative complications were the independent risk factors for the development of AMI. The strength of this retrospective nationwide study is its use of the Nationwide Inpatient Sample database that includes both a large number of patients with total joint arthroplasty and most of the known factors affecting inhospital morbidity and mortality of such surgical patients. Furthermore, the authors used appropriate statistical methods to identify the independent risk factors for in-hospital AMI. However, one limitation of this study is only the inclusion of pre-operative factors and post-operative complications in multivariate logistic regression analysis for peri-operative factors associated with the development of in-hospital AMI. Some important surgical and intra-operative factors for the development of in-hospital AMI are evidently missed. In patients with total knee or hip arthroplasty, both revision surgery, bilateral surgery and urgent surgery have been identified as independent predictors of post-operative cardiac complications includingAMI [2]. As the weighted mean volume of blood loss is more than 1,000 ml, total joint arthroplasty is one of the leading indications for surgical transfusions, especially for patients with severe comorbidities. In patients undergoing noncardiac surgery, major surgical haemorrhage has been associated independently with an increased risk of post-operative AMI [3]. Furthermore, it has been shown that intra-operative hypotension, tachycardia and hypertension are also associated independently with adverse cardiac events and mortality following noncardiac surgery [4, 5]. Actually, even short durations of an intra-operative mean artery pressure <55 mmHg can result in post-operative myocardial injury, and there is an independent graded relationship between duration of intraoperative hypotension and post-operative myocardial injury and cardiac morbidity [5]. In comparison with pre-operative risk stratification indices alone, the inclusion of intra-operative elements can improve the ability to predict peri-operative mortality and adverse cardiac events [6]. Thus, we believe that their results would have been more informative if the surgical and intra-operative factors were taken into account.

Is Remote Ischemic Preconditioning Really a Novel Renoprotective Option for Cardiac Surgery

e590 www.ccmjournal.org July 2016 • Volume 44 • Number 7 The authors reply: We thank Xue et al (1) for their interest in our article (2) and their comments. Remote ischemic preconditioning (RIPC), defined as brief and transient episodes of ischemia at a remote site before a subsequent injury of the target organ, is believed to induce an adaptive response that protects against organ injury elicited by the new insult. In the past few years, studies investigating the effects of RIPC have been published with mixed results. In contrast to studies showing a positive effect of RIPC on the heart and kidney, some trials have demonstrated that RIPC does not affect organ function, complication rates, or mortality. We have not mentioned the two recently published multicenter trials on RIPC mentioned group) who were scheduled for elective on-pump coronary artery bypass grafting surgery (with or without valve surgery) at 30 cardiac surgery centers in the United Kingdom. RIPC procedure was same as the method described by Meybohm et al (2). Similarly, this trial did not show any significant betweengroup difference in the prevalence and severity of postoperative AKI (prevalences of grades 1, 2, and 3 AKI were 29.3%, 5.7%, and 3.0% in the control group, respectively, 30.7%, 5.1%, and 2.5% in the RIPC group). In addition, the two trials also showed that RIPC did not improve other clinical outcomes after cardiac surgery, such as death, myocardial infarction, and stroke. Thus, conclusions from both trials are definitive: RIPC is ineffective in improving clinical outcomes of patients undergoing cardiac surgery (4). Given that the two studies by Meybohm et al (2) and Hausenloy et al (3) include number of patients, which are much larger than the total sample size of nine studies included in the study by Zarbock and Kellum (1), we suggest that they perform a meta-analysis based on the available 11 clinical trials to reevaluate protective effect of RIPC on kidney function after cardiac surgery. Perhaps, this would provide more robust evidence about whether RIPC is really a novel renoprotective option for cardiac surgery. The authors have disclosed that they do not have any potential conflicts of interest.

Comparing Postoperative Outcomes for Epidural Versus Intravenous Patient-Controlled Analgesia.

To the Editor: With great interest, we read the recent article by Winer et al comparing influences of epidural versus intravenous patient-controlled analgesia on outcomes after radical cystectomy in a retrospective cohort study. They showed that, despite significant improvements in initial postoperative pain control and less opioid requirement with patient-controlled epidural analgesia, there was no association between 2 analgesic methods in the length of stay, return of bowel function, or postoperative complications. In our view, certain issues in addition to the limitations described may have confounded interpretation of the study’s findings. First, the age of patients in this study ranged from 59 to 74 years. We would like to know whether comorbidities in addition to diabetes were comparable between the 2 groups, particularly cardiovascular and pulmonary comorbidities. It has been shown that baseline comorbidity status is associated with increased postoperative complications, prolonged length of stay, and perioperative mortality in patients undergoing radical cystectomy. Furthermore, in elderly patients with radical cystectomy, impaired preoperative cardiopulmonary reserve is closely related to postoperative major morbidity, prolonged length of hospital stay, and increased use of critical care resource. Second, preoperative hemoglobin and albumin levels were not included in the demographic data of patients. Actually, preoperative anemia caused by hematuria that results from bladder cancer is highly prevalent in patients undergoing radical cystectomy, with an incidence of 75%. In patients with noncardiac surgery, even mild degrees of preoperative anemia have been associated with an increased risk of postoperative mortality and morbidity. Furthermore, hypoalbuminemia is another common problem in patients with cancer. In patients undergoing radical cystectomy, preoperative hypoalbuminemia (<3.5 g/dL) has been identified as an independent predictor of postoperative complications and mortality when controlling for sex, race, ageadjusted Charlson score, body mass index,

Association Between Anesthesia Techniques and Postoperative Complications in Older Adults with Dementia Undergoing Hip Fracture Surgery.

(hazard assessment and modification) or assistive technology (e.g., walking aids, hearing and vision assessment and modification) interventions. Excluding those three studies, a sensitivity analysis of the trials revealed that the lower fall rate (RR = 0.61, 95% CI = 0.52–0.72; I = 6%, P = .37; 5 RCTs) and the number of fallers (RR = 0.82, 95% CI = 0.70–0.96; I = 66%, P = .02; 5 RCTs) were larger and became statistically significant. Moreover, the heterogeneity declined from 83% to 6% for fall rate and from 83% to 66% for number of fallers. These results suggest that, in addition to the participants and the setting in which fall prevention measures are implemented, exercise, physical environment, and assistive technology are fundamental elements of multifactorial interventions to reduce falls in older adults who are residents of care facilities.

Assessing Efficacy of Preoxygenation Techniques in ICU Patients.

e266 www.ccmjournal.org July 2015 • Volume 43 • Number 7 REFERENCE 1. Xue FS, Liu GP, Sun C: Comparing Performance of Video and Direct Laryngoscopes for Urgent Endotracheal Intubation. Crit Care Med 2015; 43:e265 2. Silverberg MJ, Li N, Acquah SO, et al: Comparison of video laryngoscopy versus direct laryngoscopy during urgent endotracheal intubation: A randomized controlled trial. Crit Care Med 2015; 43:636–641 Finally, according to their routine practice in the ICU, a 6 L/ min oxygen was administered through a nasopharyngeal catheter during apnea in the preoxygenated patients with an NRM. However, a 60 L/min oxygen was given during apnea in the preoxygenated patients with an HFNC. Because oxygen flow is a crucial determinant of efficacy of nasopharyngeal oxygen insufflation, this unbalance in the study design would be another cause of their results (5). Furthermore, we believe that a more persuasive result would have been presented, if an additional group in which nasopharyngeal oxygen insufflation with a 60 L/min flow was performed after preoxygenation using an NRM was included in the design of this study. The authors have disclosed that they do not have any potential conflicts of interest.

Comparing Performance of Video and Direct Laryngoscopes for Urgent Endotracheal Intubation.

Critical Care Medicine www.ccmjournal.org e265 The author replies: We appreciate the interest and comments made by Xue et al (1) on our study (2) and agree with several points. We emphasize that the importance of and techniques in establishing an optimal laryngeal axis (including use of external laryngeal manipulation and placement of patients in “sniff ” position) were included as part of the extensive multicomponent curriculum in airway training described in the Materials and Methods section in (2). The manipulations often needed in direct laryngoscopy stand in contrast to the oftentimes simpler approach of placing a patient’s head flat on the bed when initial video laryngoscopic view is suboptimal. We believe that the lower first-pass success rate of direct laryngoscopy was due less to a failure in the instruction of proper head and laryngeal manipulations and more to the fact that the perceived difficulty in and time required to perform these maneuvers during intubation of critically ill patients led to an early switch to the video laryngoscope, a device less reliant on such manipulations to achieve improved views. Although we agree that the use of neuromuscular blockade may have facilitated intubation with direct laryngoscopy, we emphasize the importance of the finding that physicians with limited intubation experience can achieve high first-pass success rates using video laryngoscopy without neuromuscular blockade. Finally, we agree with the comment that stylets should be used with endotracheal intubation as they facilitate the highest intubation success rates. We would like to clarify that “rigid” stylets were used only with the video laryngoscope and were those provided by the device manufacturer. The Portex singleuse stylet was used with all direct laryngoscopic intubations. The author has disclosed that he does not have any potential conflicts of interest.

Assessing risk factors of acute kidney injury after liver transplantation

We read with interest the recent article by Barreto, et al.1 evaluating the risk factors for acute kidney injury (AKI) and 30-day mortality after liver transplantation (LT) in a single-center retrospective cohort study. They showed that viral hepatitis, longer warm ischemia time and high levels of serum lactate were risk factors for AKI. Given AKI is associated with significantly increased shortand long-term morbidity and mortality after LT, their findings have potentially clinical implications. In our view, however, a limitation of this study design is that some important perioperative factors affecting postoperative AKI are not included in multivariable regression analyses evaluating variables that are independently associated with development of postoperative AKI after LT. First, preoperative albumin levels, body mass index and race were not provided. It has been shown that preoperative hypoalbuminemia is highly common among patients undergoing LT and is independently associated with postoperative AKI.2 Furthermore, increased body mass index and nonCaucasian race have been shown as independent risk factors of AKI following LT.3 Second, this study only provided incidences of intraoperative bleeding and blood transfusion, but not volumes of intraoperative blood loss and blood transfusion. Actually, both vast blood loss (for example, > 60 mL/kg) and more than five blood transfusions in the intraoperative period has been shown as the independent risk factors of postoperative AKI in the patients undergoing LT.2,4 Furthermore, intraoperative hemodynamic instability, use of vasopressor and urine output were not included in the adjusted confounders for postoperative AKI. The available evidence suggests that intraoperative hypotension, use of noradrenaline and low urine output (for example, < 60 mL/h) are independently associated with increased risk of AKI following LT.4,5 In addition, it was also unclear whether hydroxyethyl starch was used for intravascular volume resuscitation in the perioperative period. It has been shown that compared with patients receiving 5% albumin, patients receiving hydroxyethyl starch have an increased risk of AKI following liver transplantation.6 Third, we were not provided with postoperative complications. It has been shown that hypotension, hypoalbuminemia, postreperfusion syndrome, hepatic allograft dysfunction, reoperation, sepsis and surgical complications in the early postoperative period are significantly associated with occurrence of AKI after LT.2,4,7-9 Thus, we argue that not taking the above perioperative factors into account would have tampered with the inferences of the multivariable regression analyses for the risk factors of AKI following LT in this study. Finally, in this study, AKI was defined according to the Acute Kidney Injury Network criteria as an increase more than two times in serum creatinine (stage 2 or 3 AKI) in the first 72 h after surgery. Furthermore, AKI was diagnosed only based on serum creatinine component of the Acute Kidney Injury Network criteria since data on urinary output was not available for all patients. However, the Acute Kidney Injury Network criteria require to use a 48 h time window, and a 24-h urine output collection is a better alternative to estimate glomerular