European Society of Anaesthesiology.

Significant overnight oxygen desaturation is common in patients discharged from ICU who have received prolonged mechanical ventilation. This group also has a significant incidence of sleep-related breathing disorders and this mechanism is likely to be important in the pathogenesis of the hypoxaemia.

Vascular and clinical assessments of arterio-venous fistula (AVF) function and access are important in patients undergoing or preparing to undergo renal dialysis. Objective assessment techniques include colour duplex ultrasound and more recently medical infrared thermography. Ideally, these should help assess problems relating to fistula failure or to vascular steal from the hand which can result from excessive fistula blood flow. The clinical value of thermography, as yet, has not been assessed for this patient group. The aims of this study were therefore to investigate the relationships between thermography skin temperature measurement and (a) quantitative ultrasound measurement of AVF blood flow, and (b) qualitative clinical assessment of vascular steal from the hands. Fifteen adult patients underwent thermal imaging of the upper limbs, colour duplex ultrasound to derive AVF blood flow from brachial artery blood flow measurements, and a clinical evaluation for vascular steal. Temperature measurements were extracted from the thermograms, including bilateral arm and hand (Fistula -- Non-Fistula) differences, for comparison with derived AVF blood flow and steal grading. Derived AVF blood flow ranged from 30 to 1,950 ml min(-1), with a mean rate close to one litre per minute. Thermography detected the warmer superficial veins in proximity to the patent fistulas, with bilateral differences in fistula region skin temperature correlated with derived AVF blood flow (using maximum temperature measurements the correlation was +0.71 [p < 0.01]; and using mean temperature measurements the correlation was +0.56 [p < 0.05]). When thermography measurements were compared with the clinical assessment of steal the mean hand temperature differences separated steal from non-steal patients with an accuracy of greater than 90%. In summary, we have now demonstrated the potential clinical value of medical infrared thermography for assessing AVF function in renal patients.

In the intravenous iron therapy to treat iron deficiency anaemia in patients undergoing major abdominal surgery (PREVENTT) trial, the use of intravenous iron did not reduce the need for blood transfusion or reduce patient complications or length of hospital stay. As part of the trial protocol, serum was collected at randomisation and on the day of surgery. These samples were analysed in a central laboratory for markers of iron deficiency. We performed a secondary analysis to explore the potential interactions between preoperative markers of iron deficiency and intervention status on the trial outcome measures. Absolute iron deficiency was defined as ferritin <30 lg.l À1 ; functional iron deficiency as ferritin 30-100 lg.l À1 or transferrin saturation < 20%; and the remainder as non-iron deficient. Interactions were estimated using generalised linear models that included different subgroup indicators of baseline iron status. Co-primary endpoints were blood transfusion or death and number of blood transfusions, from randomisation to 30 days postoperatively. Secondary endpoints included peri-operative change in haemoglobin, postoperative complications and length of hospital stay. Most patients had iron deficiency (369/452 [82%]) at randomisation; one-third had absolute iron deficiency (144/452 [32%]) and half had functional iron deficiency (225/452 [50%]). The change in pre-operative haemoglobin with intravenous iron compared with placebo was greatest in patients with absolute iron deficiency, mean difference 8.9 g.l À1 , 95%CI 5.3-12.5; moderate in functional iron deficiency, mean difference 2.8 g.l À1 , 95%CI À0.1 to 5.7; and with little change 320

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