Summary Anaemia is common, particularly in women and the commonest underlying cause, iron deficiency, is often overlooked. Anaemia is associated with increased morbidity and mortality in patients undergoing anaesthesia; however, women are defined as being anaemic at a lower haemoglobin level than men. In this narrative review, we present the history of iron deficiency anaemia and how women’s health has often been overlooked. Iron deficiency was first described as ‘chlorosis’ and a cause of ‘hysteria’ in women and initial treatment was by iron filings in cold wine. We present data of population screening demonstrating how common iron deficiency is, affecting 12–18% of apparently ‘fit and healthy’ women, with the most common cause being heavy menstrual bleeding; both conditions being often unrecognised. We describe a range of symptoms reported by women, that vary from fatigue to brain fog, hair loss and eating ice. We also describe experiments exploring the physical impact of iron deficiency, showing that reduced exercise performance is related to iron deficiency independent of haemoglobin concentration, as well as the impact of iron supplementation in women improving oxygen consumption and fitness. Overall, we demonstrate the need to single out women and investigate iron deficiency rather than accept the dogma of normality and differential treatment; this is to say, the need to change the current standard of care for women undergoing anaesthesia.
Iron is an essential nutrient for oxygen supply and aerobic metabolism. Iron deficiency impacts cellular respiration and mitochondrial energy metabolism, which can lead to reduced skeletal muscle function and muscle mass, causing sarcopenia. Intravenous iron offers the ability to rapidly correct iron deficiency, but the functional impact on patient mental and physical health is unclear. We assessed the effects of intravenous iron therapy on physical function and quality of life in the treatment of adults with non-anaemic iron deficiency. An update and reanalysis of a previously published Cochrane systematic review was performed to assess randomized controlled trials that compared any intravenous iron preparation with placebo in adults. The primary functional outcome measure was physical performance as defined by the trial authors. Secondary outcome measures included fatigue and quality-of-life scores, and adverse effects at the end of follow-up. Biochemical efficacy was assessed by change in serum ferritin and haemoglobin concentration levels. Twenty-one randomized controlled trials, comprising 3514 participants, were included. Intravenous iron compared with placebo resulted in significantly increased physical function measured by mean peak oxygen consumption (mean difference [MD] 1.77 mL/kg/min, 95% confidence interval [CI] 0.57 to 2.97). An overall improvement in fatigue was seen (standardized MD 0.30, 95% CI À0.52 to À0.09) but no overall difference in quality of life (MD 0.15, 95% CI À0.01 to 0.31). Biochemically, intravenous iron resulted in improved serum ferritin (MD 245.52 μg/L, 95% CI 152.1 to 338.9) and haemoglobin levels (MD 4.65 g/L, 95% CI 2.53 to 6.78). There was a higher risk of developing mild adverse events in the intravenous iron group compared with the placebo group (risk ratio 1.77, 95% CI 1.10 to 2.83); however, no differences were seen in serious adverse events (risk difference 0, 95% CI À0.01 to 0.01). The quality of evidence was rated 'low' and 'very low' for all outcome variables, except for fatigue, mainly due to most studies being judged as having a high risk of bias. In non-anaemic iron-deficient adults, the use of intravenous iron compared with placebo improved physical function and reduced fatigue scores. However, we remain uncertain about the efficacy in this population due to low-quality evidence, and there is a need for further studies to address potential impact on overall quality of life.
Vestibular-multisensory interactions are essential for self-motion, navigation and postural stability. Despite evidence suggesting shared brain areas between vestibular and somatosensory inputs, no study has yet investigated whether somatosensory information influences vestibular perception. Here, we used signal detection methods to identify whether somatosensory stimulation might interact with vestibular events in a vestibular detection task. Participants were instructed to detect near-threshold vestibular roll-rotation sensations delivered by galvanic vestibular stimulation in one-half of experimental trials. A vibrotactile signal occurred to the index fingers of both hands in half of the trials, independent of vestibular signals. We found that vibrotactile somatosensory stimulation decreased perceptual vestibular sensitivity. The results are compatible with a gain regulation mechanism between vestibular and somatosensory modalities.
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