Is the Allen's test adequate to safely confirm that a radial artery may be harvested for coronary arterial bypass grafting?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether the Allen's test, plethysmography, Doppler ultrasound or MRI imaging was the best method of assessing the presence of adequate collateral blood flow in the arm preoperatively prior to radial artery harvest for conduits during CABG surgery. Altogether 176 papers were identified using the reported search of which 15 represented the best evidence on the topic. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses were tabulated. We conclude that whilst there are theoretical limitations with the Allen's test, for most patients it is an adequate method of assessing collateral arm flow prior to radial artery harvest and several large studies have confirmed the absence of neurological and vascular adverse outcome with a modified Allen's test cut-off point of up to 12 s. However, if there are concerns about collateral flow then a second confirmatory test such as dynamic Doppler ultrasound or measurement of digital pressure changes with radial artery occlusion can also be used prior to harvest. Newer techniques such as Gadolinium-enhanced magnetic resonance angiography have also been described to confirm adequate collateral circulation prior to radial artery harvest for CABG conduit and whilst in time they might come to represent an ultimate 'gold standard' they are clearly too expensive and impracticable for everyday use.     

Is skeletonised internal mammary harvest better than pedicled internal mammary harvest for patients undergoing coronary artery bypass grafting?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether skeletonised internal mammary artery (IMA) is better than pedicle IMA in coronary artery bypass grafting? Altogether 106 papers were found using the reported search, of which 12 presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of these papers are tabulated. We conclude that skeletonisation increases the length of conduit by around 3 cm and may also increase flow and conduit diameter. Skeletonisation should be the technique of choice for diabetics in whom BIMA harvest is desired, but at the expense of an extra 15-20 min per operation, no convincing outcome benefits have been shown for single IMA harvest.     

Does magnesium offer any additional benefit in patients having anti-arrhythmic treatment for atrial fibrillation following cardiac surgery?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether treatment with magnesium in addition to an anti-arrhythmic is beneficial to patients who have gone into atrial fibrillation after cardiac surgery. Altogether 466 papers were identified using the below mentioned search, of which 8 papers presented the best evidence to answer the clinical question. The author, journal, date and country of publication, patient group, relevant outcomes and weaknesses were tabulated. We conclude that while the literature on magnesium prophylaxis and non-cardiac surgical studies on magnesium therapy for atrial fibrillation suggest that magnesium may be of benefit, there are currently no studies in post-cardiac surgery atrial fibrillation to support the use of magnesium therapy for these patients.     

DNA heterogeneity and phosphorylation unveiled by single-molecule electrophoresis

Broad-spectrum analysis of DNA and RNA samples is of increasing importance in the growing field of biotechnology. We show that nanopore measurements may be used to assess the purity, phosphorylation state, and chemical integrity of nucleic acid preparations. In contrast with gel electrophoresis and mass spectrometry, an unprecedented dynamic range of DNA sizes and concentrations can be evaluated in a single data acquisition process that spans minutes. Because the molecule information is quantized and digitally recorded with single-molecule resolution, the sensitivity of the system can be adjusted in real time to detect trace amounts of a particular DNA species.     

Best evidence topic report. Antibiotics in acute exacerbations of chronic obstructive pulmonary disease

Report by Ross Murphy, Specialist Registrar
Checked by Martin McKechnie, Specialist Registrar
Joel Dunning, RCS Fellow     

The medial collateral ligament of the elbow is not isometric: an in vitro biomechanical study

BACKGROUND: The anterior bundle of the medial collateral ligament (AMCL) of the elbow has been shown to be the most important valgus stabilizer of the elbow. However, the isometry of this band has not been quantified. HYPOTHESIS: Isometric fibers exist within the AMCL, and these fibers are located within its central region. STUDY DESIGN: Controlled laboratory study. METHODS: Twelve cadaveric elbow specimens were mounted in a testing apparatus in a valgus gravity-loaded orientation. Passive supinated flexion was performed and the motion recorded using an electromagnetic tracking device. Hundreds of attachment points for the AMCL of the elbow were recorded on the medial epicondyle and ulna. The overall change in length between each point on the ulna to every humeral point, throughout the arc of motion, was quantified (DeltaL = Lmax - Lmin). The locations of the smallest DeltaL values were determined relative to the attachment site of the AMCL on the medial epicondyle. RESULTS: True isometry was not found throughout the arc of flexion. The smallest DeltaL values averaged 2.8 +/- 1.2 mm (range: 0.7 mm to 5.2 mm). Isometric fibers do not exist within the AMCL; however, "nearly" isometric areas are located on the lateral aspect of the attachment site of the AMCL on the medial epicondyle, near the anatomic axis of rotation. CONCLUSIONS: We postulate that these nearly isometric areas would be the most ideal location for graft attachment during reconstruction of the AMCL.     

Resistance to disruption and gapping of peripheral nerve repairs: an in vitro biomechanical assessment of techniques

One potential cause of suboptimal results after nerve repair is disruption or gapping of the neurorrhaphy in the postoperative period. This study assesses the biomechanical strength of five nerve repair techniques: fibrin glue, simple epineurial sutures, and three other novel neurorrhaphy methods. Fifty rabbit sciatic nerve segments were divided and repaired utilizing one of five different methods, producing five groups of ten specimens. Fibrin glue and four epineurial suture techniques (simple, horizontal mattress, "Tajima," "Bunnell") were employed. Repaired nerve segments were ramp-loaded to failure on an Instron 8300 materials-testing machine at a displacement rate of 5 mm/min. Gapping at the repair site was captured using high-resolution video. Differences among the five groups were assessed for significance using ANOVA and Fisher's protected least squares differences post-hoc testing. The mean force to produce disruption was higher for mattress suture repairs relative to simple repairs, but not significantly so (p = 0.31). Both were significantly stronger than fibrin glue repairs (p < 0.0001). "Tajima" and "Bunnell" repairs were both statistically stronger than glue (p < 0.0001), simple (p < 0.0001), or mattress (p = 0.0004) repairs, but not significantly different from one another (p = 0.48). Data for gapping at the repair site were similar with all suture techniques outperforming fibrin glue (p = 0.003). "Bunnell" repairs demonstrated the most resistance to gapping, compared to glue (p < 0.0001), simple (p = 0.0001), mattress (p = 0.007) and "Tajima" repairs (p = 0.01). These data demonstrate that repairs done utilizing fibrin glue are significantly weaker than all types of suture repairs. Two novel techniques for nerve repair (epineurial "Tajima" and "Bunnell") are significantly more resistant to disruption and gapping. Further evaluation to assess the effect of these repair techniques on function is required.     

The implications of NICE guidelines on the management of children presenting with head injury

Background: NICE guidelines for the management of head injury were published in June 2003. Their recommendations differ markedly from previous guidelines published by the Royal College of Surgeons (RCS). In place of skull radiography and admission, computed tomography (CT) is advocated. The impact of these guidelines on service provision in the UK is unknown. Methods: Data on all clinical correlates of children presenting with any severity of head injury was collected in three hospitals in the northwest of England. The current skull radiograph (SXR), CT scan, and admission rates were determined. The rates of SXR, CT scan, and admission that should have occurred when following either the RCS or NICE guidelines were then determined. Results: Data from 10 965 patients who attended three hospitals between February 2000 and August 2002 was studied. Twenty five per cent of patients received a SXR, 0.9% a CT scan, and 3.7% were admitted. Strict adherence to the RCS guidelines would have resulted in a 50% SXR rate, a 1.6% CT scan rate, and a 7.1% admission rate. Adherence to NICE guidelines would result in a 0.3% SXR rate, an 8.7% CT scan rate, and a 1.4% admission rate, although the CT rate would drop to 6.3% if vomiting three or more times in the under 12s was used instead of more than one vomit. Conclusions: The new NICE guidelines do not increase the workload caused by patients attending with head injury but they move their management from the observation ward to the radiology department.