Online Letters to the Editor

expected. Second, multivariate analysis of 7-day mortality was adjusted not only for host confounders (Acute Physiology and Chronic Health Evaluation II score) but also by other factors that were related to the source of infection such as Candida parapsilosis, often related to parenteral nutrition and catheter-related infection, and abdominal secondary origin of infection. Thus, although it might have been interesting to analyze the effect of CVC removal according to different sources of candidemia, we believe that our results could be a good initial approach to clinical practice where prompt CVC removal is usually performed before the origin of infection is confirmed. The authors have disclosed that they do not have any potential conflicts of interest. Benito Almirante, MD, Mireia Puig-Asensio, MD, Infectious Diseases Department, Hospital Universitari Vall d´Hebron, Medicine Department, Universitat Autònoma de Barcelona, Barcelona, Spain

REFERENCES

1. Hsu H-Y, Chao C-M: What Is the Impact of Catheter Removal on the Outcome of Non–Catheter-Related Candidemia? Crit Care Med 2014; 42:e629 2. Puig-Asensio M, Pemán J, Zaragoza R, et al; on behalf of the Prospective Population Study on Candidemia in Spain (CANDIPOP) Project, Hospital Infection Study Group (GEIH) and Medical Mycology Study Group (GEMICOMED) of the Spanish Society of Infectious Diseases and Clinical Microbiology (SEIMC), and Spanish Network for Research in Infectious Diseases: Impact of therapeutic strategies on the prognosis of candidemia in the ICU. Crit Care Med 2014; 42:1423–1432 3. Pappas PG, Kauffman CA, Andes D, et al; Infectious Diseases Society of America: Clinical practice guidelines for the management of candidiasis: 2009 update by the Infectious Diseases Society of America. Clin Infect Dis 2009; 48:503–535 4. Cornely OA, Bassetti M, Calandra T, et al; ESCMID Fungal Infection Study Group: ESCMID* guideline for the diagnosis and management of Candida diseases 2012: Non-neutropenic adult patients. Clin Microbiol Infect 2012; 18(Suppl 7):19–37 5. Garnacho-Montero J, Díaz-Martín A, García-Cabrera E, et al: Impact on hospital mortality of catheter removal and adequate antifungal therapy in Candida spp. bloodstream infections. J Antimicrob Chemother 2013; 68:206–213 DOI: 10.1097/CCM.0000000000000480

Conservative Oxygen Therapy in Mechanically Ventilated Patients To the Editor:

I

n a recent issue of Critical Care Medicine, we read with interest the article by Suzuki et al (1), which focuses on the effects of conservative oxygen therapy in ventilated ICU patients. However, we are concerned that it might be used to justify premature changes in practice. In particular, the use of a single-center before and after design that enrolled a small proportion of ventilated patients during the study period means that this study has a high risk of bias (2). The small sample size also means that it is likely that there is unmeasured baseline imbalance affecting the reported outcomes. The lessons of neonatal medicine (3, 4) suggest potential mortality risks with lower oxygen saturation e630

www.ccmjournal.org

targets. The benefits of a conservative approach to oxygen therapy remain theoretical, and the potential risks of exposure to inadvertent hypoxia through adoption of such an approach are of concern. The authors report decreased oxygen use, but oxygen is a very low-cost medication. Although no information was provided as to the monetary value of decreased oxygen use, we estimate the cumulative savings to be less than $300 in their study. This might be a small price to pay for the safety window that is provided by supplemental oxygenation against hypoxia. Higher oxygenation level may also extend the duration of safety in an acutely ill patient at times of unanticipated acute events such as pneumothorax or accidental extubation during transport or repositioning of the patient. Importantly, the authors’ discussion is framed around the paradigm that a conservative oxygen strategy is beneficial; although account of the fact that multiple outcomes have been reported is made, this study does not demonstrate any significant effects on outcomes. Rather, it demonstrates a number of positive and negative trends associated with the adoption of a conservative oxygen approach. In the multivariable analysis by Suzuki et al (1), which reports the adjusted odds ratio for key outcomes, no explanation is provided regarding what type of organ failure was mostly responsible for the decreased adjusted prevalence of organ failure seen with conservative oxygen therapy. Of greater concern, the odds ratio for the use of anti–delirium medications was 1.52, which raises the possibility that decreased oxygen administration and lower Pao2 levels may induce subclinical cerebral hypoxia and delirium. Despite this potential concern, the authors do not present information on the type of agents used and their cumulative dose. Finally, conservative oxygen therapy may increase the duration of mandatory mechanical ventilation because of fear of oxygen desaturation when the starting oxygenation level before possible extubation is already low. This possible delayed liberation from the ventilator effect may, in turn, increase the risk of ventilator-associated complications. The lack of information on mechanical ventilation and its complications is an important shortcoming of the study by Suzuki et al (1). Overall, we suggest great caution in accepting the safety of conservative oxygen therapy and/or seeking to apply conservative oxygen therapy to the care of critically ill mechanically ventilated patients outside of research protocols on the basis of current evidence. The authors have disclosed that they do not have any potential conflicts of interest. Rakshit Panwar, FCICM, MD, MBBS, Department of Anaesthesia, Intensive Care and Pain Medicine, John Hunter Hospital, Newcastle, Australia; Paul Young, FCICM, BHB, MBChB, BSc (Hons), Intensive Care Unit, Wellington Hospital, Wellington, New Zealand, and Medical Research Institute of New Zealand, Wellington, New Zealand; Gilles Capellier, MD, PhD, Critical Care Unit, University Hospital Besançon and University of Franche-Comté, Besançon, France

REFERENCES

1. Suzuki S, Eastwood GE, Glassford NJ, et al: Conservative Oxygen Therapy in Mechanically Ventilated Patients: A Pilot Before-and-After Trial. Crit Care Med 2014; 42:1414–1422 September 2014 • Volume 42 • Number 9

Online Letters to the Editor 2. Bellomo R, Warrillow SJ, Reade MC: Why we should be wary of single-center trials. Crit Care Med 2009; 37:3114–3119 3. BOOST II United Kingdom Collaborative Group; BOOST II Australia Collaborative Group; BOOST II New Zealand Collaborative Group, Stenson BJ, Tarnow-Mordi WO, Darlow BA, et al: Oxygen saturation and outcomes in preterm infants. N Engl J Med 2013; 368:2094–2104 4. SUPPORT Study Group of the Eunice Kennedy Shriver NICHD Neonatal Research Network; Carlo WA, Finer NN, Walsh MC, et al: Target ranges of oxygen saturation in extremely preterm infants. N Engl J Med 2010; 362:1959–1969 DOI: 10.1097/CCM.0000000000000439

The authors reply:

W

e thank Panwar et al (1) for their thoughtful comments concerning our study of conservative oxygen therapy in critically ill mechanically ventilated patients (2). We agree that our study focused on a specific group of patients and constitutes no more than a pilot feasibility and safety study. Such studies are prone to type I error and, when unblinded and with unconcealed allocation (as is the case for all before-and-after studies), may be affected by selection and allocation bias. We sought to minimize such bias by studying all consecutive patients who fulfilled the inclusion criteria. We are acutely aware of the neonatal lower oxygen targeting studies and the surrounding controversy and concerns. It was because of these concerns that we chose to perform a pilot feasibility and safety study first. Our preliminary findings provide a degree of reassurance. We also understand that there is continuing uncertainty regarding the putative dangers of hyperoxia (3, 4) and the choice of the optimal physiological target for oxygen therapy (5); thus, our study is simply the first step in a journey aimed at identifying the optimal oxygenation target in mechanically ventilated patients. We agree that the cost of oxygen is low (estimated at 3 cents per liter in our hospital). However, whether providing patients with higher Fio2 increases their safety remains controversial (6). In our assessment of organ failure, we did not specify that the biggest difference between the two groups was a decreased prevalence of cardiovascular failure (odds ratio, 0.15; 95% CI, 0.02–1.1; p = 0.26) in the conservative oxygen group. We preferred to provide a global assessment instead. We also noticed the possibility of an increased use of antidelirium medications. However, we did not collect information on specific agents. We are now extending our study to patients with cardiac surgery and planning to obtain such information. We think the comment regarding the effect of conservative oxygen therapy on the mode of mechanical ventilation used and on the time from intubation to spontaneous breathing is important. We apologize that we do not have the ability to provide the necessary information at short notice. In response to this comment, we plan to conduct an additional analysis of the mechanical ventilation data in our study patients and hope to report a detailed analysis of such findings in the near future.

Critical Care Medicine

The authors have disclosed that they do not have any potential conflicts of interest. Rinaldo Bellomo, MD, PhD, Satoshi Suzuki, MD, PhD, Glenn M. Eastwood, PhD, Department of Intensive Care, Austin Hospital, Melbourne, VIC, Australia

REFERENCES

1. Panwar R, Young P, Capellier G: Conservative Oxygen Therapy in Mechanically Ventilated Patients. Crit Care Med 2014; 42:e630–e631 2. Suzuki S, Eastwood G, Glassford NJ, et al: Conservative oxygen therapy in mechanically ventilated patients: A pilot before-and-after trial. Crit Care Med 2014; 42:1414–1422 3. Young P, Beasley R, Bailey M, et al; Study of Oxygen in Critical Care (SOCC) Group: The association between early arterial oxygenation and mortality in ventilated patients with acute ischaemic stroke. Crit Care Resusc 2012; 14:14–19 4. Ihle JF, Bernard S, Bailey MJ, et al: Hyperoxia in the intensive care unit and outcome after out-of-hospital ventricular fibrillation cardiac arrest. Crit Care Resusc 2013; 15:186–190 5. Webb SR, Young PY, Bellomo R: The “sweet spot” for physiological targets in critically ill patients. Crit Care Resusc 2012; 14:253–255 6. Downs JB: Has oxygen administration delayed appropriate respiratory care? Fallacies regarding oxygen therapy. Respir Care 2003; 48:611–620 DOI: 10.1097/CCM.0000000000000472

Is the Revised Cardiac Risk Index the Right Risk Index for Vascular Surgery Patients? To the Editor:

I

n a recent issue of Critical Care Medicine, we read with interest the results of Gillmann et al (1), where the authors conclude that the risk predictive power of high-sensitive cardiac troponin T in addition to the Revised Cardiac Risk Index (RCRI) could facilitate 1) the detection of vascular surgery patients at highest risk for perioperative myocardial ischemia and 2) the evaluation and development of cardioprotective therapeutic strategies. Indeed, perioperative cardiac troponin measurement has been proved to play a prognostic role in vascular surgery procedures for early and late cardiovascular complications, as well as for early and late mortality, even when compared with standard preoperative cardiac and surgical risks (2). Furthermore, the RCRI is also recommended by the latest American College of Cardiology/American Heart Association Guidelines for preoperative cardiac risk assessment in noncardiac surgery (3). But is this index really suitable for vascular surgery procedures as well? Regarding the utilization of RCRI as the indicated clinical risk index for vascular procedures as well, there are many studies leading to opposing results. Bertges et al (4) concluded that the RCRI substantially underestimates in-hospital cardiac events in patients undergoing elective or urgent vascular surgery, and according to the authors, the Vascular Study Group of New England–Cardiac Risk Index (VSG-CRI) more accurately predicts in-hospital cardiac events after vascular surgery and represents an important tool for clinical decision making. Additionally, Ford et al (5) concluded in their review that the RCRI www.ccmjournal.org

e631

Conservative oxygen therapy in mechanically ventilated patients.

Conservative oxygen therapy in mechanically ventilated patients. - PDF Download Free
316KB Sizes 0 Downloads 8 Views