Fluid warmers and aluminium toxicity

Summer is almost upon us and we have a bumper issue of Anaesthesia lined up for you this month. In a landmark study Perl et al. report that uncoated aluminium plates in the CE-marked enFlow® fluid warming system release aluminium when used with a balanced crystalloid solution at levels far above FDA-recommended limits. The short and long-term clinical implications are unclear at present, but the manufacturer of enFlow® recently issued a global market recall. This received widespread attention from many news outlets, including The Guardian. Long-term sequelae of aluminium toxicity may include neurological impairment, Alzheimer’s disease and metabolic bone disease. Professor Exley, a chemist from Keele University and a recognised aluminium toxicity expert, argues a full investigation is now required. In the accompanying editorial, Charlesworth and van Zundert make a strong case for clinicians to be at the forefront of research on commonly used medical devices whilst also promoting clinical vigilance. A newly published paper from Taylor et al. seems to validate the conclusions drawn by Perl et al., more so for other balanced crystalloid solutions and blood products. Watch this space for more news!

Figure 1.pngFigure 1 Sketch of fluid‐warming disposables with aluminium heating plate in the fluid chamber. a: parylene (purple)‐coated device; b: non‐coated device. PVC tubing is drawn in black and the aluminium plate is drawn in grey. Note in (b), the fluid is in direct contact with aluminium.

Articles related to transfusion medicine and patient blood management are always popular. In this month’s issue, Trentino et al., retrospectively investigated the interaction between anaemia and red cell transfusion and what effect transfusion may have on mortality and length of stay at various levels of nadir haemoglobin. They retrospectively analysed 60,955 surgical admissions and observed higher mortality with red cell transfusion at haemoglobin levels greater than 90 g.l−1, whereas at all levels below 90 g.l−1 mortality was not significantly different. This is an important study which adds to the evidence base supporting restrictive transfusion, but like most observational studies, it demonstrates an association and uncontrolled confounding is likely. In addition, the effects of restrictive transfusion strategies are still unclear in certain perioperative subgroups such as those with cardiovascular disease.

Staying on the theme of anaemia and transfusion, Keeler et al. report a secondary analysis of a previously published randomised trial that evaluated the effect of intravenous iron versus oral iron on haemoglobin and transfusion requirements in patients with colorectal cancer-associated anaemia. In this secondary analysis, they compared quality of life scores between both study groups using validated questionnaires such as the EQ-5D-5L, SF-36 and FACT-An. Intravenous was associated with higher quality of life scores across multiple domains as compared with oral iron three months following surgery. In their accompanying editorial, Shah and Bailey discuss some of the current challenges in measuring outcomes following surgery with regards the methods used to determine a minimum clinically important difference and the choice of outcome measurement tools.

Elsewhere, Oller et al. evaluated the effect of a novel crystalloid fluid (Oxsealife®) on recovery from haemorrhagic shock in pigs. One of the beneficial properties of this fluid is that it is able to generate microvascular nitric oxide and scavenge reactive oxygen species generated during the ischaemia-reperfusion injury. Through a series of experiments, they observed improvements in serum markers of organ function, oxygen delivery, and better maintenance of glycocalyx integrity in pigs receiving this fluid compared to those receiving whole blood. This is a very promising physiological alternative to blood in the management of haemorrhage shock and early phase human studies are warranted.

There is growing interest in the measurement and impact of frailty across all medical specialities, yet there is no gold-standard method to achieve this. Pugh et al. prospectively evaluated the inter-rater reliability of the Clinical Frailty Scale (CFS), on a variety of healthcare professionals, for assessing frailty in patients admitted to critical care. They used this tool based on the findings of a systematic review which identified the CFS as the most commonly reported frailty assessment tool in critical care. The CFS is a nine-category assessment tool (Fig. 2) that is easy to administer and a CFS rating >4 is considered frail. They observed a good level of inter-rater agreement in frailty assessment using the CFS but identified independent factors, such as the assessor having a medical background, which could influence ratings. In the accompanying editorial, Falvey & Ferrante discuss the challenges in defining frailty, and why it is important to assess for it in the critically ill patients.

Figure 2.pngFigure 2 Rockwood clinical frailty scale.

There is huge interest currently in the potential advantages of the peri-operative use of dexmedetomidine, and in this month’s issue, we have two such articles. Cheng et al. performed a multicentre randomised trial evaluating the effect of intra-operative dexmedetomidine on cognitive decline in patients aged >65 years undergoing elective gastrointestinal laparotomy surgery. They observed a reduction in cognitive decline up to one postoperative month, which was mechanistically associated with changes in serum brain-derived neurotrophic factor. Whether or not this beneficial effect persists at longer follow-up time points requires further investigation. Grape et al. also performed a systematic review comparing the analgesic efficacy on intra-operative dexmedetomidine with remifentanil. They found improvements in pain scores during the first 24 hours and fewer side effects in patients who received dexmedetomidine.

Gomez-Rios evaluated the performance of a new video laryngeal mask, TotaltrackTM, which combines a supraglottic airway with a videolaryngoscope (Figure 3). The device was found to be acceptable in 300 patients, though further studies comparing it to current standards of airway management are required to determine its precise role in airway management. Boisson et al compared a non-invasive, cardiac output photoplethysmographic device (Clearsight) with a conventional PiCCO device in 20 adults undergoing elective surgery. They observed no differences in overall performance with regards to measuring absolute and changing stroke volumes. The non-invasive nature of this device may increase the uptake of goal-directed therapy.

Figure 3.jpgFigure 3 The Totaltrack video laryngeal mask and its components. Side and rear view of the device. 1. Videotrack; 2. memory card; 3. non‐rechargeable battery‐operated light; 4. supraglottic airway; 5. high‐volume, low‐pressure cuff; 6. rigid blade; 7. tip of the blade protected by a silicone cover; 8. intubation channel guide; 9. laryngeal suction channel; 10. gastric suction channel; 11. tracheal tube; 12. tracheal tube connector; and 13. distal aperture of the gastric suction channel.

In our reviews and guidelines section, we are pleased to publish the 2019 Association of Anaesthetists and British Association of Day Surgery guidelines for day-case surgery (Fig. 4). This is essential reading for all anaesthetists, clinical leads and theatre managers. Lastly, we have a very interesting, narrative review by Sepulveda et al. on neural inertia, a phenomenon that may explain the resistance observed to changes in consciousness induced by total intravenous anaesthesia, independent of drug kinetics.

Figure 4Figure 4 Key recommendations from the day-case surgery guidelines.

Over on Anaesthesia Reports, we have some fascinating articles on a triple regional analgesia technique for pleuropulmonary sarcoma resection, analgesia using a wound catheter after clamshell thoracotomy (Fig. 5), CSF-cutaneous fistula formation following accidental dural puncture, and delayed presentation of cardiac tamponade following traumatic diaphragmatic hernia repair. This case report from Saunders et al. has the highest Altmetric score from our new journal. Congratulations to the authors!

Figure 5.jpgFigure 5 Intra-operative placement of a wound catheter.

We are sad to report that two of our senior editors are stepping down after many years of service at the journal. Good luck to Professor Jaideep Pandit and Dr Stuart White on their future endeavours. We have appointed several new editors including Dr’s Laura Duggan, Seema Agarwal, and two of our previous Trainee Fellows, Helen Laycock and Kariem El-Boghdadly. Finally, we have a new system for manuscript submissions with separate sites for Anaesthesia and Anaesthesia Reports. Make sure you send us your work for an efficient, friendly and helpful peer review service.

Dr Akshay Shah and Professor Andrew Klein