Key Papers from the Most Recent Literature Relevant to Anesthesiologists
The ASA’s statement on P-values: Context, process, and purpose. The American Statistician. DOI: 10.1080/00031305.2016.1154108. See also Evolution of reporting P values in the biomedical literature, 1990–2015. JAMA 2016; 315:1141–8.
The American Statistical Association Board of Directors issued a statement on P values and statistical significance which draws renewed and vigorous attention to changing research practices that have contributed to a reproducibility crisis in science. “Widespread use of ‘statistical significance’ (generally interpreted as ‘P < 0.05’) as a license for making a claim of a scientific finding (or implied truth) leads to considerable distortion of the scientific process,” says the American Statistical Association statement. In this “post P < 0.05 era,” the full power of statistical argumentation in all its nuance will be brought to bear to advance science, rather than making decisions simply by reducing complex models and methods to a single number and its relationship to an arbitrary threshold. This new era would be marked by radical change in how editorial decisions are made regarding what is publishable, removing the temptation to inappropriately hunt for statistical significance as a justification for publication.
Take home message: Widespread use of “statistical significance” (generally interpreted as “P < 0.05”) as a license for making a claim of a scientific finding (or implied truth) leads to considerable distortion of the scientific process. The “post P < 0.05 era” opening now should prevent from inappropriately hunting for statistical significance as a justification for publication.
Long-term results of stenting versus endarterectomy for carotid-artery stenosis. N Engl J Med 2016; 374:1021–31. Randomized trial of stent versus surgery for asymptomatic carotid stenosis. N Engl J Med 2016; 374:1011–20. Association between age and risk of stroke or death from carotid endarterectomy and carotid stenting: A meta-analysis of pooled patient data from four randomised trials. Lancet 2016; 387:1305–11.
This series of three major papers (two randomized controlled trials and a meta-analysis of four randomized controlled trials) on carotid stenting versus endarterectomy appears simultaneously in the literature. In the Carotid Revascularization Endarterectomy versus Stenting Trial, no significant difference was found between the stenting group and the endarterectomy group with respect to the primary composite end point of stroke, myocardial infarction, or death during the periprocedural period or any subsequent ipsilateral stroke during 4 yr of follow-up. The authors update their data with an extension of the follow-up period up to 10 yr. Two thousand five hundred and two symptomatic or asymptomatic patients were included. The conclusions were similar to those obtained after 4 yr postprocedure with respect to the primary end point.
In the Stent versus Surgery for Asymptomatic Carotid Stenosis trial, the authors compared carotid-artery stenting with embolic protection and carotid endarterectomy in patients 79 yr of age or younger who had severe carotid stenosis and were asymptomatic (i.e., had not had a stroke, transient ischemic attack, or amaurosis fugax in the 180 days before enrollment) and were not considered to be at high risk for surgical complications. One thousand four hundred fifty-three patients were randomized. The primary end point was a composite of death, stroke, or primary infarction and was tested at 1 yr postprocedure. It was found that stenting with embolic protection was noninferior to endarterectomy with regard to the rate of the primary composite end point at 1 yr.
Age was reported to be an effect modifier in four randomized controlled trials comparing carotid artery stenting (CAS) and carotid endarterectomy (CEA), with better outcomes with CEA than CAS noted in the more elderly patients. In the meta-analysis, the authors included only trials that randomly assigned patients to CAS or CEA and only patients with symptomatic stenosis. They assessed rates of stroke or death in 5-yr age groups in the periprocedural period (between randomization and 120 days) and ipsilateral stroke during long-term follow-up for patients assigned to CAS or CEA. Differences between CAS and CEA were also measured. Almost 5,000 patients were included. CEA was clearly superior to CAS in patients aged 70 to 74 yr and older. Age had little effect on CEA periprocedural risk or on postprocedural risk after either procedure.
Take home message: While carotid artery stenting was noninferior to carotid endarterectomy in symptomatic and asymptomatic patients of younger age, carotid endarterectomy was clearly superior to carotid artery stenting in patients aged 70 yr or older.
Effect of noninvasive ventilation on tracheal reintubation among patients with hypoxemic respiratory failure following abdominal surgery: A randomized clinical trial. JAMA 2016; 315:1345–53.
This multicenter randomized controlled trial investigated whether the use of noninvasive ventilation (NIV) obviates the need for invasive mechanical ventilation among patients developing hypoxemic acute respiratory failure after abdominal surgery. Patients were randomly allocated either to a standard oxygen therapy group (up to 15 l/min to maintain oxygen saturation measured by pulse oximetry of 94% or higher) (n = 145) or a NIV group in which patients received NIV via facial mask (inspiratory pressure support level, 5 to 15 cm H2O; positive end-expiratory pressure, 5 to 10 cmH2O; fraction of inspired oxygen titrated to maintain oxygen saturation measured by pulse oximetry of 94% or higher) (n = 148). The main outcome measure was all-cause tracheal intubation within the following 7 days. The use of NIV compared with standard oxygen therapy reduced the risk of tracheal intubation (33.1% vs. 45.5%; 95% CI, -23.5% to -1.3%), which suggests its use is beneficial in patients developing hypoxemic respiratory failure after abdominal surgery.
Take home message: This randomized controlled trial including patients who developed hypoxemic respiratory failure after abdominal surgery showed that the use of noninvasive ventilation compared with standard oxygen therapy reduces the need for tracheal intubation.
Effect of inhaled xenon on cerebral white matter damage in comatose survivors of out-of-hospital cardiac arrest: A randomized clinical trial. JAMA 2016; 315:1120–8.
Experimental data reporting on neuroprotective efficacy of drugs during brain ischemic/hypoxic injury have thus far failed to prove effective in any clinical setting. In this randomized single-blind phase 2 clinical drug trial conducted between August 2009 and March 2015 at two multipurpose intensive care units in Finland, 110 comatose survivors of out-of-hospital cardiac arrest were assigned to receive early either inhaled xenon combined with hypothermia (33 °C) for 24 h (n = 55 in the xenon group) or hypothermia treatment alone (n = 55 in the control group). The primary end point was cerebral white matter damage as evaluated by fractional anisotropy from diffusion tensor magnetic resonance imaging (MRI) scheduled to be performed between 36 and 52 h after cardiac arrest. It was found that patients in the xenon group exhibited less white matter damage at MRI, yet no difference in mortality or neurologic outcomes was seen at 6 months after the event.
Take home message: In this randomized controlled trial including comatose survivors of out-of-hospital cardiac arrest, early application of xenon plus hypothermia for 24 h resulted in less white matter damage at MRI than hypothermia alone, but no difference was observed in mortality or neurologic outcomes at 6 months.
Effect of mindfulness-based stress reduction vs cognitive behavioral therapy or usual care on back pain and functional limitations in adults with chronic low back pain: A randomized clinical trial. JAMA 2016; 315:1240–9.
Chronic low back pain is a leading cause of disability in the United States and other Western nations. However, little evidence is available directly comparing conservative treatment options, and some commonly recommended treatments such as cognitive behavioral therapy (CBT) have limited availability. In this study, the authors directly compared CBT with mindfulness-based stress reduction (MBSR) and usual care. The MBSR approach is relatively easily implemented and focuses on awareness and acceptance of experiences including physical discomfort and difficult emotions. A total of 342 adults with chronic nonspecific low back pain participated in the trial. At 26 weeks, the coprimary outcomes of functional limitation and pain bothersomeness were improved for both CBT and MBSR groups relative to usual care, although there were no significant differences between the active treatments. Thus MBSR may provide benefit to chronic low back pain sufferers with efficacy similar to the well-established approach of using CBT.
Take home message: In this randomized, interviewer-blind, clinical trial, MBSR was found to provide benefit to chronic low back pain sufferers with efficacy similar to the well-established approach of using CBT.
The effects of power, leadership and psychological safety on resident event reporting. Med Educ 2016; 50:343–50.
Since physicians in training are in a key position to identify unsafe conditions and adverse events, institutional safety relies on their willingness to submit reports. Given this acknowledged vital role, what deters residents? This study queried 106 residents, in eight specialties, at a single institution. Using multiple survey tools, residents’ intentions to report safety concerns were evaluated with respect to the impact “perceived power distance” or hierarchy among members of the organization, “leader inclusiveness” or explicit support, and “psychological safety” had on their actions. The results indicate that psychological safety significantly and directly impacts the plan to report. Both “perceived power distance” and “leader inclusiveness” function as significant, independent variables to influence the impact of psychological safety. Thus, institutional culture impacts the intention of individuals to report safety events. These results have implications for targets of potential institutional cultural change to encourage residents to share their concerns.
Take home message: This study indicates that psychological safety significantly and directly impacts the plan to report safety events.