Oxygen sensing,anaesthesia and critical care: a narrative review

In 2019, the scientists who discovered how cells sense and adapt to oxygen availability were awarded the Nobel Prize. This elegant sensing pathway is conserved throughout evolution, and it underpins the physiology and pathology that we, as clinicians in anaesthesia and critical care, encounter on a daily basis. The purpose of this review is to bring hypoxia-inducible factor, and the oxygen-sensing pathway as a whole, to the wider clinical community. We describe how this unifying mechanism was discovered, and how it orchestrates diverse changes such as erythropoiesis, ventilatory acclimatisation, pulmonary vascular remodelling and altered metabolism. We explore the lessons learnt from genetic disorders of oxygen sensing, and the wider implications in evolution of all animal species, including our own. Finally, we explain how this pathway is relevant to our clinical practice, and how it is being manipulated in new treatments for conditions such as cancer, anaemia and pulmonary hypertension.     

Silver Diamine Fluoride Protocol for Reducing Preventable Dental Hospitalisations in Victorian Children

IntroductionThis study was designed to assess whether a dental caries management protocol combining a single application of 38% silver diamine fluoride (SDF) with comprehensive oral health education will successfully divert high-risk children from dental treatment under dental general anaesthesia (DGA), arrest active caries in primary teeth, and improve parent-reported child oral health–related quality of life (OHRQoL).MethodsChildren aged 2 to 10 years, who attended two public dental agencies in Victoria, Australia, and were unable to tolerate restorative treatments in the clinic setting, elected to participate in either a 38% SDF intervention protocol or, alternatively, referral for DGA. Follow-up examinations were completed at 6 months to assess caries progression, decayed missing filled tooth index, PUFA index (pulpal involvement, ulceration, fistula, abscess), DGA referral rates, and OHRQoL (Early Childhood Oral Health Impact Scale [ECOHIS]).ResultsOf the total sample, 89.5% of children (n = 102) [mean (SD) age, 4.1 (1.0) years] with 401 active carious lesions elected to participate in the 38% SDF protocol; 10.5% (n = 12) of parents opted for referral for treatment under DGA. The proportion of active caries subsequently arrested at follow-up (number of arrested lesions/number of lesions treated) was 0.78 (95% CI, 0.69 to 0.87). There was an 88% reduction in referrals for DGA in eligible children over the 6-month period. The 38% SDF intervention group showed a significant improvement in ECOHIS scores at follow-up (P < .001).DiscussionAdoption of the 38% SDF intervention protocol resulted in a significant reduction in the rate of preventable dental hospitalisations. Most parents opted against referral for DGA. Parent-reported OHRQoL for children improved significantly.     

Evidence-based strategies to reduce the incidence of postoperative delirium: a narrative review

Delirium is one of the most commonly occurring postoperative complications in older adults. It occurs due to the vulnerability of cerebral functioning to pathophysiological stressors. Identification of those at increased risk of developing delirium early in the surgical pathway provides an opportunity for modification of predisposing and precipitating risk factors and effective shared decision-making. No single delirium prediction tool is used widely in surgical settings. Multi-component interventions to prevent delirium involve structured risk factor modification supported by geriatrician input; these are clinically efficacious and cost effective. Barriers to the widespread implementation of such complex interventions exist, resulting in an ‘implementation gap’. There is a lack of evidence for pharmacological prophylaxis for the prevention of delirium. Current evidence suggests that avoidance of peri-operative benzodiazepines, careful titration of anaesthetic depth guided by processed electroencephalogram monitoring and treatment of pain are the most effective strategies to minimise the risk of delirium. Addressing postoperative delirium requires a collaborative, whole pathway approach, beginning with the early identification of those patients who are at risk. The research agenda should continue to examine the potential for pharmacological prophylaxis to prevent delirium while also addressing how successful models of delirium prevention can be translated from one setting to another, underpinned by implementation science methodology.     

Obstetric analgesia and anaesthesia in SARS-CoV-2-positive parturients across 10 maternity units in the north-west of England: a retrospective cohort study

Since the start of the COVID-19 pandemic, few studies have reported anaesthetic outcomes in parturients with SARS-CoV-2 infection. We reviewed the labour analgesic and anaesthetic interventions utilised in symptomatic and asymptomatic parturients who had a confirmed positive test for SARS-CoV-2 across 10 hospitals in the north-west of England between 1 April 2020 and 31 May 2021. Primary outcomes analysed included the analgesic/anaesthetic technique utilised for labour and caesarean birth. Secondary outcomes included a comparison of maternal characteristics, caesarean birth rate, maternal critical care admission rate along with adverse composite neonatal outcomes. A positive SARS-CoV-2 test was recorded in 836 parturients with 263 (31.4%) reported to have symptoms of COVID-19. Neuraxial labour analgesia was utilised in 104 (20.4%) of the 509 parturients who went on to have a vaginal birth. No differences in epidural analgesia rates were observed between symptomatic and asymptomatic parturients (OR 1.03, 95%CI 0.64–1.67; p = 0.90). The neuraxial anaesthesia rate in 310 parturients who underwent caesarean delivery was 94.2% (95%CI 90.6–96.0%). The rates of general anaesthesia were similar in symptomatic and asymptomatic parturients (6% vs. 5.7%; p = 0.52). Symptomatic parturients were more likely to be multiparous (OR 1.64, 95%CI 1.19–2.22; p = 0.002); of Asian ethnicity (OR 1.54, 1.04–2.28; p = 0.03); to deliver prematurely (OR 2.16, 95%CI 1.47–3.19; p = 0.001); have a higher caesarean birth rate (44.5% vs. 33.7%; OR 1.57, 95%CI 1.16–2.12; p = 0.008); and a higher critical care utilisation rate both pre- (8% vs. 0%, p = 0.001) and post-delivery (11% vs. 3.5%; OR 3.43, 95%CI 1.83–6.52; p = 0.001). Eight neonates tested positive for SARS-CoV-2 while no differences in adverse composite neonatal outcomes were observed between those born to symptomatic and asymptomatic mothers (25.8% vs. 23.8%; OR 1.11, 95%CI 0.78–1.57; p = 0.55). In women with COVID-19, non-neuraxial analgesic regimens were commonly utilised for labour while neuraxial anaesthesia was employed for the majority of caesarean births. Symptomatic women with COVID-19 are at increased risk of significant maternal morbidity including preterm birth, caesarean birth and peripartum critical care admission.     

Principles of environmentally-sustainable anaesthesia: a global consensus statement from the World Federation of Societies of Anaesthesiologists

The Earth’s mean surface temperature is already approximately 1.1°C higher than pre-industrial levels. Exceeding a mean 1.5°C rise by 2050 will make global adaptation to the consequences of climate change less possible. To protect public health, anaesthesia providers need to reduce the contribution their practice makes to global warming. We convened a Working Group of 45 anaesthesia providers with a recognised interest in sustainability, and used a three-stage modified Delphi consensus process to agree on principles of environmentally sustainable anaesthesia that are achievable worldwide. The Working Group agreed on the following three important underlying statements: patient safety should not be compromised by sustainable anaesthetic practices; high-, middle- and low-income countries should support each other appropriately in delivering sustainable healthcare (including anaesthesia); and healthcare systems should be mandated to reduce their contribution to global warming. We set out seven fundamental principles to guide anaesthesia providers in the move to environmentally sustainable practice, including: choice of medications and equipment; minimising waste and overuse of resources; and addressing environmental sustainability in anaesthetists’ education, research, quality improvement and local healthcare leadership activities. These changes are achievable with minimal material resource and financial investment, and should undergo re-evaluation and updates as better evidence is published. This paper discusses each principle individually, and directs readers towards further important references.     

Propofol use in children with allergies to egg,peanut, soybean or other legumes

Propofol is the most commonly administered intravenous agent for anaesthesia in children. However, there are concerns that the emulsified preparation may not be safe in children with an allergy to egg, peanut, soybean or other legumes. We conducted a retrospective study of children with immunologically confirmed egg, peanut, soybean or legume allergy and who underwent general anaesthesia at Princess Margaret Hospital for Children between 2005 and 2015. We extracted details regarding allergy diagnosis, each anaesthetic administered and any adverse events or signs of an allergic reaction in the peri-operative period. A convenience sample of patients without any known food allergies was identified from our prospective anaesthesia research database and acted as a control group. We identified 304 food-allergic children and 649 procedures where propofol was administered. Of these, 201 (66%) had an egg allergy, 226 (74%) had a peanut allergy, 28 (9%) had a soybean allergy and 12 (4%) had a legume allergy. These were compared with 892 allergy-free patients who were exposed to propofol. In 10 (3%) allergy patients and 124 (14%) allergy-free patients, criteria for a possible allergic reaction were met. In nine of the food-allergic children and in all the controls valid non-allergic explanations for the clinical symptoms were found. One likely mild allergic reaction was experienced by a child with a previous history of intralipid allergy. We conclude that genuine serious allergic reaction to propofol is rare and is not reliably predicted by a history of food allergy.     

General anaesthesia for operative obstetrics

General anaesthesia in obstetrics is reducing with a reported use in only 4% of caesarean sections in 2017–2018. Obstetric surgery is often urgent, requiring effective team communication and a rapid, focused preoperative assessment. Physiological changes of pregnancy increase the incidence of aspiration, desaturation and failed intubation. In addition, the rapidly evolving circumstances add additional stress, impacting on performance. Hypotension from aortocaval compression is common and minimized by left lateral tilt or uterine displacement. Rapid sequence induction with tracheal intubation remains gold standard but supraglottic devices are advocated in the event of failed intubation. Awareness remains relatively common and adequate depth of anaesthesia should be maintained and monitored. Complications are more common in obese pregnant patients. Whilst women with pre-eclampsia are at particular risk of hypertensive responses to intubation and extubation, intravenous opiates can ameliorate this. Improved multidisciplinary communication on the delivery suite allows for pre-emptive assessment of patients at risk of requiring an operative delivery. With diminishing individual experience of general anaesthesia in obstetrics and delivery suite often being covered by junior doctors, simulation exercises can improve confidence, performance and team working.     

西安地区成人改良Jackson骶骨棒棒道影像学测量

目的 通过收集西安地区成人的影像学资料，为改良Jackson骶骨棒的操作提供解剖学数据参考。方法 将100例健康成年人作为研究对象，对其进行三维CT扫描，获得所需数据，将数据录入Mimics软件中处理，利用软件确定棒道入口，测量棒道长度，对不同性别间进行统计学分析。结果 男性测得棒道长度为（35.05±6.19） mm，最大值为52 mm；女性为（34.19±5.84） mm，最大值为46 mm。男性骶骨棒棒道长度略大于女性，但差异无统计学意义（P＞0.05）。结论 经测量100例西安地区健康成人改良Jackson骶骨棒棒道长度得知，术中男性骶骨棒棒道深度应控制在52 mm以内，女性控制在46 mm以内，但个体差异较大，术前进行测量可指导手术医师制定手术方案，提高手术安全性。     

General anaesthesia for ophthalmic surgery

The majority of ophthalmic surgeries are performed as day cases under topical or regional anaesthesia with or without intravenous sedation. However, general anaesthesia is necessary in certain circumstances e.g. local anaesthetic allergy or patients who are unable to cooperate or to lie flat or still. Patients for ophthalmic surgery are frequently elderly with multiple comorbidities, such as diabetes and hypertension. Patients with rare genetic syndromes may present for eye surgery. Therefore adequate preoperative evaluation and preparation will minimize perioperative complications. The goals of general anaesthesia are smooth induction and emergence, with stable intra-ocular pressure (IOP) and akinesia of the globe. These can be achieved with a combination of intravenous and inhalational agents with or without muscle relaxants and opiates. Use of the laryngeal mask airway has the advantage of causing a smaller rise in IOP on insertion and less coughing on emergence. Total intravenous anaesthesia with propofol and remifentanil has the advantages of causing less postoperative nausea and vomiting (PONV), reduced stress response to airway intervention, rapid recovery and smooth emergence. Some eye procedures require special consideration, for example, strabismus and vitreoretinal surgery involves traction of the rectus muscles producing a higher incidence of oculocardiac reflex and PONV. Most ophthalmic surgery produces mild to moderate pain amenable to non-opioid analgesics. Intraoperative topical and regional anaesthesia reduce postoperative pain and opiate requirement. Open globe injury and a full stomach present unique challenges to prevent increase in IOP as well as protecting the airway.