The valuable contribution of observational studies to nephrology

In studies on the effects of therapy (or other interventions), the randomized controlled trial (RCT) is an almost unbeatable standard in clinical research. The value of RCTs leaves unabated the valuable contributions of observational studies to medicine. This paper discusses some limitations of RCTs providing examples where these are not possible, inappropriate, inadequate, or unnecessary. Thereafter, it focuses on observational studies and gives a number of examples of studies on etiology, diagnosis, prognosis, and adverse effects, where observational designs have provided answers to research questions that could not have been answered by RCTs. Strengths and weaknesses of the different observational study designs are discussed. Finally, it is concluded that both observational studies and RCTs fulfill a complementary and valuable role in nephrology.     

Retrospective clinical studies in surgery: potentials and pitfalls

As many surgical studies are performed retrospectively, it is desirable to improve the conduct, analysis and reporting of such research designs. This article reviews some of the most common forms of bias encountered in clinical research and outlines various types of study design and analysis that can help to minimize the amount of bias introduced into the results. We describe the advantages and disadvantages of 'raw' data analysis, stratified analysis, matched pair analysis and multivariate analysis, and apply them to an example of a hypothetical hand surgery study.     

Urinary biomarkers may provide prognostic information for subclinical acute kidney injury after cardiac surgery

Objective

This study aimed to determine the biomarker-specific outcome patterns and short-and long-term prognosis of cardiac surgery–asoociated acute kidney injury (AKI) identified by standard criteria and/or urinary kidney biomarkers.

A new method of intraoperative hydraulic impedance measurement provides valuable prognostic information about infrainguinal graft patency.

PURPOSE: Prognostic information about graft outcome, obtained by using a new method for intraoperative measurement of vascular impedance, was evaluated. METHODS: Hydraulic impedance was measured in 136 infrainguinal bypass grafts that were entered into a multicenter trial. Seventy femoropopliteal and 66 femorocrural polytetrafluoroethylene (PTFE) grafts were used. The arterial impedance measurement involved a silicon bypass graft temporarily inserted between the proximal and distal anastomoses sites. A flowmeter probe and a pressure transducer were incorporated into the tube. The digitally stored waveforms were subjected to a fast Fourier transformation and both input (Z(x)) and characteristic (Z(0)) impedances, as well as phase relations, were computed and related to graft outcome after 3 years. RESULTS: Significant prognostic information for both popliteal and crural grafts was provided by means of the phase angle of the first harmonic. Primary and secondary patency rates for popliteal bypasses were 45% +/- 1% and 65% +/- 2% for phase angles greater than -40 degrees (n = 57) and 37% +/- 1% and 40% +/- 1% for phase angles less than -40 degrees (n = 13, p(prim ) = not significant, p(sec) < 0.01). For crural grafts, the secondary patency rates were 49% +/- 1% and 61% +/- 2% for phase angles greater than -40 degrees (n = 53) and 15% +/- 1% and 0% for phase angles less than -40 degrees (n = 13, P <.01). All crural bypass grafts with phase angles less than -40 degrees occluded within 16 months. Steady flow resistance, as well as Z(x) and Z(0), failed to indicate a significant relation to graft prognosis. CONCLUSION: This method provides reliable prognostic information regarding graft patency and opens hydraulic impedance measurement to clinical surgery. The phase lag between flow and pressure curves, as expressed by the phase angle of the first harmonic, provides significant prognostic information.     

An anesthesia information system designed to provide physician-specific feedback improves timely administration of prophylactic antibiotics

Surgical site infections are a frequent cause of morbidity and mortality and add significantly to the cost of care. One component of the national Surgical Infection Prevention (SIP) program is to ensure timely administration of prophylactic antibiotics, a key factor to reduce postoperative infection. Our anesthesia department decided to assume the responsibility for timing and administration of antibiotic prophylaxis and we initiated a multitiered approach to remind the anesthesiologist to administer the prophylactic antibiotics. We used our anesthesia clinical information system to implement practice guidelines for timely antibiotic administration and to generate reports from the database to provide specific feedback to individual care providers with the goal of ensuring that patients receive antibiotic prophylaxis within 1 h of incision. Before the initiation of this project, 69% of eligible patients received antibiotics within 60 min of the incision. After the program began, there was a steady increase in compliance to 92% 1 yr later. Provider-specific feedback increases compliance with practice guidelines related to timely administration of prophylactic antibiotics. Anesthesia information systems hold promise for implementing and monitoring new practice guidelines and the anesthesiologist may play a key role in influencing surgical outcomes by ensuring appropriate therapy that may not be directly related to anesthesia care.     

Performance-based tests and self-reported questionnaires provide distinct information for the preoperative evaluation of total hip arthroplasty patients

Our objectives were to assess relationships between self-reported questionnaires and 2-minute walk test (2MWT) and timed get-up-and-go test (TUG) in preoperative total hip arthroplasty patients. A total of 162 patients completed the Western Ontario and McMaster Universities Osteoarthritis Index and Short Form 36 and performed 2MWT and TUG. Correlations between self-reported questionnaires and 2MWT and TUG were mild to moderate, indicating that the 2MWT and TUG capture additional dimensions of preoperative total hip arthroplasty function not measured by the Western Ontario and McMaster Universities Osteoarthritis Index and Short Form 36. Use of walking aids, female sex, and presence of other painful joints were significantly associated with 2MWT, whereas older age and additional painful joints were significantly associated with TUG. These 2 tests are easy to perform in clinical practice and contribute to a comprehensive assessment of preoperative status.     

Opioid analgesia: new information from gene knockout studies

The cloning of opioid peptides and receptors has led to the development of knockout mice deficient in a gene encoding for each peptide and each receptor. The major advantage of the knockout approach is the complete selectivity that the removal of a protein encoded for by a gene provides. These knockout animals are adding to our knowledge of the physiology, pathophysiology and pharmacology of opioid systems. In addition, they are providing real impact in addressing the long-standing debates over receptor subtype heterogeneity and functional cooperativity between receptor subtypes.