Rui P. Li

Assessing biomarker of acute kidney injury and its association with worse outcomes after cardiac surgery

Stephan Segerer, Yuya Sugano, Maja T. Lindenmeyer, Ines Auberger, Urs Ziegler, Clemens D. Cohen, Stephan C.F. Neuhauss and Johannes Loffing Institute of Physiology, University Hospital, Zurich, Switzerland; Division of Nephrology, University Hospital, Zurich, Switzerland; Zurich Center for Integrative Human Physiology, Zurich, Switzerland; Institute of Anatomy, University of Zurich, Zurich, Switzerland; Institute of Molecular Life Sciences, University of Zurich, Zurich, Switzerland; Center for Microscopy and Image Analysis, University of Zurich, Zurich, Switzerland; and Division of Nephrology, Klinikum Harlaching, Munich, Germany Correspondence: J. Loffing, Institute of Anatomy, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland. E-mail: johannes.loffing@anatom.uzh.ch

Assessing acute kidney injury in bariatric surgery patients admitted to the intensive care unit.

To the Editor, With great interest, we read the recent article by Morgan and Ho [1] assessing incidence and risk factors for acute kidney injury (AKI) after bariatric surgery in an observational, multicenter study with 590 patients admitted to the intensive care unit (ICU). They found that the incidence of postoperative AKI was 17.5%. Furthermore, the multivariate analysis showed that male sex, premorbid hypertension, higher Acute Physiology and Chronic Health Evaluation II scores at admission, and blood transfusions were associated with postoperative AKI. Strengths of this study are its use of a large sample of patients from 8 specialist-run ICU admissions databases. Most importantly, the authors used appropriate statistical methods to identify the risk factors of postoperative AKI. We congratulate the authors for conducting this clinically useful research, but we would like to ask several questions about their methodology. First, AKI was determined by a comparison between baseline and peak postoperative serum creatinine (sCr) concentrations, using the modified Acute Kidney Injury Network (AKIN) criteria. However, the authors did not provide the observational duration of postoperative sCr. It must be emphasized that the AKIN criteria need to use a 48hour time window [2]. Furthermore, we would like to know whether postoperative sCr levels used for diagnosis of AKI had been corrected for fluid balance. It has been shown that dilution of sCr by fluid accumulation in critically ill patients admitted to the ICU may lead to underestimation of the severity of AKI; therefore, correction of sCr for fluid balance can improve recognition and staging of AKI [3]. In addition, the AKIN urinary output criteria were not used in this study due to the inconsistency in reliable recording across smaller participating ICUs during the study period. Wlodzimirow et al. [4] demonstrated that only use of the sCr criteria without the urine output criteria can significantly underscore the incidence and grade of AKI and significantly delay the diagnosis of AKI in adult critically ill

Head elevation and improved laryngoscopic view

We read with interest the article by El-Orbany et al [1] assessing effects of different head positions on the laryngoscopic view obtained by a Macintosh blade in the same subject. They concluded that sniffing position was associated with a better view when the laryngoscopic view grade was more than 1a in the head extension position. Furthermore, the elevated sniffing position further improved the laryngoscopic view grade in some patients. Many things of this study were well done. The strengths of this study design include an adequate number of study subjects and assessment of the laryngoscopic view in a randomized head position. The authors had also tried to control most of the known factors affecting the laryngoscopic view, such as the upper airway anatomy, atlanto-occipital range of motion, body mass index, blade size, lifting force, use of external laryngeal manipulation (ELM) and muscle relaxation [2]. In addition, El-Orbany et al openly discussed the limitations of their study. In our view, however, there are still several aspects of this study that deserve to be discussed and clarified. First, according to findings of Hochman et al [3], El-Orbany et al [1] considered that the mechanism of the laryngoscopic view improved by head elevation was that neck flexion moved the glottis posteriorly, bringing it into view and obtaining a better view. However, an issue ignored by them is the angular change in the laryngoscopist’s line of vision to the larynx during head elevation. Namely, when the patient’s head is elevated, the laryngoscopist’s eyes move downward and the line of vision moves upward, touching the lowest point on the underside of the curved flange of a Macintosh blade; and laryngoscopic view gradually becomes better [4] (Fig. 1). Other than posterior displacement of the glottis by the neck flexion, thus, angular change in the laryngoscopist’s line of vision to the larynx should also contribute to the laryngoscopic view improvement produced by head elevation. Second, the authors did not provide the height of the operating table surface and experience of the anesthesiologists. It has been shown that the height of the operating table during laryngoscopy can significantly affect the quality of laryngoscopic view when patients are placed in the supine

Assessment of difficult laryngoscopy in pediatric patients receiving general anesthesia.

routinely admit term infants following anesthesia, one respondent reported that his/her institution does not routinely observe newborns prior to discharge, while the remainder have varying policies regarding observation following anesthesia (Figure 2). The most common duration of observation is 4 hours (5 respondents, 36%); 3 respondents (21.4%) observe for 6 hours and 2 respondents (14.3%) observe for 2 hours following anesthesia.