AimsAtrial fibrillation is frequently encountered in critical illness and causes adverse effects including haemodynamic decompensation, stroke and longer hospital stay. It is common to supplement serum magnesium for the purpose of preventing new-onset atrial fibrillation. However, no randomised studies support this practice in the non-cardiac surgery critical care population, and its effectiveness is unclear. We sought to investigate the effectiveness of magnesium supplementation in preventing new-onset atrial fibrillation in a mixed critical care population.MethodsWe conducted a single centre retrospective observational study of adult critical care patients. We employed a natural experiment design, using the supplementation preference of the bedside critical care nurse as an instrumental variable.Using the electronic patient record, magnesium supplementation opportunities were defined and linked to the bedside nurse. Nurse preference for administering magnesium was obtained using multilevel modelling. The results were used to define ‘pro’ and ‘anti’ supplementation groups, which were inputted into an instrumental variable regression to obtain an estimate of the effect of magnesium supplementation.Results9,114 magnesium supplementation opportunities were analysed, representing 2,137 critical care admissions for 1,914 patients. There was significant variation in magnesium supplementation practices attributable to the individual nurse, after accounting for covariates. The instrumental variable analysis showed magnesium supplementation was associated with a 3% decreased chance of experiencing new-onset atrial fibrillation (95% CI −0.06 to −0.04, p = 0.03).ConclusionsThis study supports the strategy of routine magnesium supplementation, but further work is required to identify optimal serum magnesium targets for prophylaxis of atrial fibrillation.What’s New?Routine administration of supplemental magnesium sulphate is associated with a reduced chance of developing new-onset Atrial Fibrillation, in a general critical care cohort.This finding agrees with previous Randomised Controlled Trial results which are limited to the cardiac critical care population.This finding disagrees with previously published observational studies, which is likely due to better control of unmeasured confounding.There is significant variation in serum magnesium supplementation attributable to the individual bedside critical care nurse.Electronic health records offer the ability to evaluate the effectiveness of routinely administered treatments which lack evidence in an affordable way.Natural experiments and instrumental variable analysis offer the opportunity to derive causally robust estimations of treatment effectiveness by better accounting for unobserved confounding.

IntroductionMany routinely administered treatments lack evidence as to their effectiveness. When treatments lack evidence, patients receive varying care based on the preferences of clinicians. Standard randomised controlled trials are unsuited to comparisons of different routine treatment strategies, and there remains little economic incentive for change.Integrating clinical trial infrastructure into electronic health record systems offers the potential for routine treatment comparisons at scale, through reduced trial costs. To date, embedded trials have automated data collection, participant identification and eligibility screening, but randomisation and consent remain manual and therefore costly tasks.This study will investigate the feasibility of using computer prompts to allow flexible randomisation at the point of clinical decision making. It will compare the effectiveness of two prompt designs through the lens of a candidate research question—comparing liberal or restrictive magnesium supplementation practices for critical care patients. It will also explore the acceptability of two consent models for conducting comparative effectiveness research.Methods and analysisWe will conduct a single centre, mixed-methods feasibility study, aiming to recruit 50 patients undergoing elective surgery requiring postoperative critical care admission. Participants will be randomised to either ‘Nudge’ or ‘Preference’ designs of electronic point-of-care randomisation prompt, and liberal or restrictive magnesium supplementation.We will judge feasibility through a combination of study outcomes. The primary outcome will be the proportion of prompts displayed resulting in successful randomisation events (compliance with the allocated magnesium strategy). Secondary outcomes will evaluate the acceptability of both prompt designs to clinicians and ascertain the acceptability of pre-emptive and opt-out consent models to patients.Ethics and disseminationThis study was approved by Riverside Research Ethics Committee (Ref: 21/LO/0785) and will be published on completion.Trial registration numberNCT05149820.

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Atrial fibrillation is a frequently encountered condition in critical illness and causes adverse effects including haemodynamic decompensation, stroke and prolonged hospital stay. It is a common practice in critical care to supplement serum magnesium for the purpose of preventing episodes of atrial fibrillation. However, no randomised studies support this practice in the non-cardiac surgery critical care population, and the effectiveness of magnesium supplementation is unclear. We sought to investigate the effectiveness of magnesium supplementation in preventing the onset of atrial fibrillation in a mixed critical care population. We conducted a single centre retrospective observational study of adult critical care patients. We utilised a natural experiment design, using the supplementation preference of the bedside critical care nurse as an instrumental variable. Using routinely collected electronic patient data, magnesium supplementation opportunities were defined and linked to the bedside nurse. Nurse preference for administering magnesium was obtained using multilevel modelling. The results were used to define "liberal" and "restrictive" supplementation groups, which were inputted into an instrumental variable regression to obtain an estimate of the effect of magnesium supplementation. 9114 magnesium supplementation opportunities were analysed, representing 2137 critical care admissions for 1914 patients. There was significant variation in magnesium supplementation practices attributable to the individual nurse, after accounting for covariates. The instrumental variable analysis showed magnesium supplementation was associated with a 3% decreased relative risk of experiencing an atrial fibrillation event (95% CI − 0.06 to − 0.004, p = 0.03). This study supports the strategy of routine supplementation, but further work is required to identify optimal serum magnesium targets for atrial fibrillation prophylaxis.

Background: This report describes the use of intranasal dexmedetomidine to control incident pain and facilitate daily change of dressing in a patient with cutaneous breast cancer. Case presentation: A 45-year-old woman with extensive thoracic cutaneous metastatic bilateral breast cancer requiring daily 2-hour dressing changes to manage significant exudate. Pain during change of dressing was severe and unresponsive to usual analgesics. Deeper sedation was not an option as the patient was required to change position 1 hour into dressing change. Case management: Intranasal dexmedetomidine was administered 40 minutes prior to dressing change and provided effective rousable sedation and analgesia for the duration of the procedure. Case outcome: Dexmedetomidine provided rousable sedation, allowing the patient to follow commands and mobilise during the procedure. Pain was controlled. No adverse cardiovascular effects were noted with the use of intranasal dexmedetomidine. Conclusion: Intranasal dexmedetomidine is a potentially useful medication for procedural sedation in the management of complex wound dressings. It provides rousable short-term sedation, anxiolysis and analgesia. Further research into the role of intranasal dexmedetomidine to facilitate challenging dressing changes in a community setting is warranted.