N. Levy

Peri‐operative iv fluids in diabetic patients – don’t forget the salt

It is estimated by the International Diabetes Federation that 246 million adults worldwide have diabetes mellitus and the figure is expected to reach 380 million by 2025 [1]. Anaesthetists will be involved in the care of more diabetic patients as they present in increasing numbers for surgery as a result of the complications of diabetes. The cornerstone of metabolic control in the peri-operative period, except for Type II diabetics undergoing minor surgery, is the administration of intravenous (iv) glucose with potassium chloride and a variable insulin infusion. Standard anaesthetic and surgical texts recommend the use of 5% or 10% glucose at a rate of 125–83 ml.h [2–6]. This corresponds to practice in nine out of 11 acute hospitals in the East Anglia region as shown by the authors’ recent audit (unpublished results). It is likely, therefore, that this regimen is common nationally. There are problems, however, with the uncritical acceptance of these recommendations, in particular the development of hyponatraemia. Excess free water is a well recognised complication of the use of glucose iv in non-diabetic patients [7] and has also been described with the use of sliding scale regimens in diabetic patients [6, 8, 9]. In nondiabetic patients the peri-operative use of glucose iv without sodium chloride would not be advocated, so the failure to emphasise the need for sodium in diabetic patients is surprising. This omission may have arisen, at least in part, as a consequence of the way iv regimens for diabetic patients developed over past decades. Peri-operative mortality amongst diabetic patients was high until the 1970s because of inadequate administration of insulin [10, 11]. A variety of methods to achieve glycaemic control were used in the 1970s with the insulin often administered subcutaneously. In 1979, in a seminal paper, Alberti and Thomas described a simple and safe method of achieving glycaemic control whereby glucose, insulin and potassium were infused at a fixed rate [12]. The ‘Alberti regimen’ rapidly became established practice at a time when infusion pumps were unreliable; the inclusion of glucose, insulin and potassium in the same bag of iv fluid ensured safety. A carbohydrate load of 180 g glucose per day was recommended to minimise catabolism (7.5 g.h). Alberti and Thomas also described the use of other iv fluids in conjunction with the glucose-insulin-potassium regimen, but lactate-containing solutions (such as Hartmann’s solution) were not recommended because they were thought to exacerbate the hyperglycaemia [12, 13]. The experimental data supporting the avoidance of lactate-containing solutions were weak [13] and there are strong theoretical reasons for suggesting that Hartmann’s solution is most unlikely to adversely affect glycaemic control. Since lactate is a 3-carbon compound and glucose is a 6-carbon compound, then in one litre of Hartmann’s solution the 29 mmol of lactate would yield 14.5 mmol of glucose at most. This assumes that the biosynthetic pathways of gluconeogenesis are 100% efficient, one litre is given instantaneously, and that no lactate is oxidised. The initial glucose distribution space is the extracellular fluid volume which in a 70 kg patient would be 12–15 litres. Thus, the maximum increase in glucose concentration with one litre of Hartmann’s would be about 1 mmol.l and in clinical practice the effect on blood glucose will be much less. The longstanding irrational fear of using lactate-containing solutions has probably contributed significantly to hyponatraemia in diabetic patients. With the ‘Alberti regimen’ neither glucose nor insulin could be varied independently. If blood glucose was not adequately controlled, the bag of iv fluid had to be discarded and a new bag of glucose with the appropriate amount of insulin and potassium started. Although inherently safe, the practicalities of frequent changes of infusion made this regimen labour intensive which contributed to inadequate glycaemic control [14]. Variable rate insulin regimens became feasible in the 1980s as a result of reliable infusion pumps and the widespread availability of rapid accurate monitoring of blood glucose concentrations [14–16]. Insulin and glucose could be administered separately by infusion pumps with the rate of insulin infusion adjusted according to the circulating glucose value. This had become common practice in the Oxford region by 1993 when over 70% of anaesthetists used variable rate insulin infusions for glycaemic control during major surgery [15]. The use of separate glucose and insulin infusions can achieve excellent glycaemic control peri-operatively and provides substrate with insulin. However, the unthinking adoption of the regimen has inadvertently exposed diabetic patients to the potentially dangerous complication of hyponatraemia. Although this is unlikely to be more than a biochemical abnormality in most patients, symptoms of cerebral oedema may occur with lethargy and headache, seizures, coma and even death [17]. Grant and colleagues commented on the occurrence of hyponatraemia as a complication of variable rate insulin infusions and suggested the additional infusion of 0.9% sodium chloride in the event of hyponatraemia [6]. However, even though they recommended additional saline iv the rate of glucose infusion remained 100 ml.h. There is the obvious risk of fluid overload in these circumstances together with the practical difficulties of several iv infusions. Many studies have shown that hypotonic iv solutions predispose to Anaesthesia, 2008, 63, pages 1043–1045 .....................................................................................................................................................................................................................

Is the pursuit of DREAMing (drinking, eating and mobilising) the ultimate goal of anaesthesia?

Defining good anaesthetic care has been subject of much debate, but there is still no consensus. Differences in anaesthetic care have been shown not to affect surgical mortality, even in patients undergoing cardiac surgery [1], and death under general anaesthesia is now such a rare event that alternative measures of the quality of anaesthetic care provision have been explored. These include: measuring patient satisfaction; patient-reported outcome measures (PROMS); measuring quality indicators, including postoperative pain scores, incidence of postoperative nausea and vomiting, postoperative temperature, postoperative functional and cognitive performance; and assessing the patient’s perception of the anaesthetist’s communication skills [2–6]. The analysis of quality of recovery has changed and has progressed from the immediate assessment of physiological parameters at a single postoperative time-point to the assessment of broader postoperative ability [2, 3].

Deprescribing: implications for the anaesthetist.

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Chlorhexidine anaphylaxis: implications for post‐resuscitation management

References 1. Saito T, Den S, Tanuma K, Tanuma Y, Carney E, Carlsson C. Anatomical bases for paravertebral anesthetic block: fluid communication between the thoracic and lumbar paravertebral regions. Surgical-Radiologic Anatomy 1999; 21: 359–63. 2. Karmakar MK, Gin T, Ho AM. Ipsilateral thoraco-lumbar anaesthesia and paravertebral spread after low thoracic paravertebral injection. British Journal of Anaesthesia 2001; 87: 312–6. 3. Carney J, Finnerty O, Rauf J, Bergin D, Laffey JG, Mc Donnell JG. Studies on the spread of local anaesthetic solution in transversus abdominis plane blocks. Anaesthesia 2011; 66: 1023–30. 4. Børglum J, Jensen K, Moriggl B, L€ onnqvist P, Christensen A, Sauter A. Ultrasound-guided transmuscular Quadratus Lumborum blockade. British Journal of Anesthesia 2013. http://bja. oxfordjournals.org/forum/topic/brjana_ el%3B9919 (accessed 30/11/2015). 5. Schuenke MD, Vleeming A, Van Hoof T, Willard FH. A description of the lumbar interfascial triangle and its relation with the lateral raphe: anatomical constituents of load transfer through the lateral margin of the thoracolumbar fascia. Journal of Anatomy 2012; 22: 568–76.

Controversies in the peripartum management of diabetes.

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Is 10 litres of 4% dextrose in 0.18% saline NICE?

comment on whether they consider serratus anterior plane block suitable for providing analgesia for patients with thoracic trauma, and if they were aware of any trauma cases in which the block was performed and their outcome. Also, could this technique be used to provide continuous analgesia by siting the catheter tip superficial to the serratus anterior muscle? Finally, do the authors consider this block to be suitable for patients with deranged coagulation or who are taking anticoagulants?

Current BNF recommendations on peri‐operative cessation of clopidogrel

general anaesthesia at our hospital, the fetus is monitored using a Phillips Avalon Fetal Monitor FM30 machine (Fig. 4), which uses exactly the same caution and emergency audible alarms as the MP70 anaesthetic monitor, and indicates problems such as abnormal fetal heart rate or loss of contact, both common occurrences in this setting. The Fetal Monitor alarm distracts the anaesthetist from his ⁄ her current task, and further, when trying to locate the source of the alarm, potentially affects the quality of clinical care provided. In addition, anaesthetists familiar with this type of false alarm become desensitised to the alarm sound and risk ignoring an important warning. We believe that when designing equipment, manufacturers must consider the likelihood of concurrent use with other monitors in the same clinical area and ensure that each machine’s alarms are distinctive and unique. C. Pollit G. Graham St Thomas’ Hospital, London, UK Email: chris.pollitt@nhs.net

A new effective non-invasive method of cooling patients with malignant hyperthermia

expiratory pressure (PEEP) valve resulting in high PEEP. Following the satisfactory completion of the routine preoperative checklist, anaesthesia commenced. A PEEP valve was already present in the expiratory limb of the circle system and it was opened fully counter-clockwise to cancel any PEEP. The valve was not removed from the circle system. Shortly after IPPV was started the high PEEP alarm sounded. Malfunction of the PEEP valve was suspected and it was removed immediately. It was observed that the nut which secures the cylindrical PEEP valve to the plastic domeshaped cover had completely fallen from its intended position and was lying on the unidirectional valve. Removal of the valve and replacing it with a standard cover promptly abolished the high PEEP and restored normal ventilation. A PEEP valve of this nature has two components: a cylindrical PEEP valve and a plastic dome-shaped cover and these two components are assembled together with the use of a nut. On close examination, I found that when the PEEP valve is opened counter clockwise to its full extent, the cylindrical valve rotates in a manner so as to undo the nut from the assembly. Hence it is likely that the nut could become loose following repeated attempts to fully open the PEEP valve during the course of its routine use. I suspect that the nut fell from its intended position onto the unidirectional valve when I attempted to fully open the valve during my preoperative check. I wish to make the following suggestions to overcome this problem: the PEEP valve should be connected to the anaesthetic machine only if it is required; the assembly of the valve should be carefully inspected before it is attached to the anaesthetic machine; and the manufacturer could improve the safety of this assembly by securely anchoring the nut to the plastic cover so that the nut does not fall from its intended position, even if the PEEP valve is completely unscrewed and detached from the cover-nut unit. Furthermore, use of a reverse threaded nut could overcome this problem as the counter clockwise turns of the PEEP valve will tighten the nut and thereby augment its safety.

Monitoring guidelines: a missed opportunity?

We read with interest the recent AAGBI recommendations for standards of monitoring during anaesthesia and recovery [1]. We appreciate that the introduction of most routine monitoring during anaesthesia has not been subjected to rigorous randomised controlled investigation. The progressive reduction in anaesthesia-related morbidity and mortality is therefore linked to monitoring by association only. However, more recent developments in monitoring have been subjected to randomised controlled trials. Of particular interest to us is the use of cardiac output monitors during the operative period, for which Grade A evidence is available for their use in reducing hospital length of stay and morbidity [2–7]. No specific recommendation for cardiac output monitoring is made in the AAGBI guidelines. We suggest that this represents a significant missed opportunity for the introduction of such monitoring as standard for major surgical procedures, as this would enable targeted fluid management to optimise tissue perfusion intra-operatively, reduce hospital length of stay after major surgery and lead to a reduction in overall morbidity [2–7]. A number of cardiac output monitoring devices are available [2]. Pulmonary artery catheterisation is still cited as the ‘gold standard’ of cardiac output monitoring, but there are concerns regarding its use and effect on patient outcome [8]. The aim of intra-operative cardiac output monitoring is to optimise tissue perfusion and oxygen delivery to organs during the surgical insult, whilst avoiding the consequences of fluid overload. Conventional monitoring of cardiovascular status including the central venous pressure (CVP) is insufficiently sensitive to detect deficits in perfusion, and in studies comparing the use of cardiac output monitoring verses CVP monitoring, those patients that were optimised with cardiac output monitoring do considerably better than those patients whose treatment was guided using the CVP [5–7]. The majority of data available for operative fluid optimisation relates to oesophageal Doppler monitoring [2–4, 6, 7]. A meta-analysis of randomised controlled trials examining the effect of oesophageal Doppler monitoring on patient outcomes showed significant benefits with an average reduction of length of stay of 2.98 days (p < 0.0001), with an associated reduction in morbidity, but there was no overall effect on mortality [3]. Although less evidence is available for other forms of cardiac output monitoring, they are designed to provide similar information and should deliver similar benefits. Pearse et al. conducted a randomised controlled trail using LiDCO for postoperative fluid management and demonstrated shorter hospital stays with fewer complications [5]. The economic benefits of cardiac output monitoring have been highlighted in evidence submitted to Parliament by the Improving Surgical Outcomes Group [9]. They estimated that in 2004 fewer than 40 000 of the 1 million patients who could have benefited from optimisation were monitored with the equipment to allow this to occur. Savings to the NHS in the order of £2 million for an average NHS Trust were estimated, taking into account capital outlay and running costs. In summary, cardiac output monitoring has been demonstrated to result in significant reductions in morbidity when used for intra-operative fluid optimisation. In particular, the reduction in length of stay and complications could result in significant benefits for individual patients and also in economic terms for the NHS as a whole. We hope that these factors will be considered in the next edition of the Association’s guidelines.

Pre‐emptive use of haloperidol in ICU to prevent emergence agitation

It is well known that a slight error in a test, an experiment or a calculation can render the results invalid. Likewise, an error in a publication can lead to misleading information. These errors can range from typographical, formatting or printing errors, which are obvious and are of little clinical significance in the majority of occasions. Some errors can lead to not particularly wrong, but confusing or misleading clinical information. Most journals, including Anaesthesia, insert a correct version in a succeeding journal issue as an erratum. If one were to rely on just the original article without referring to the erratum subsequently reported, it is possible to get the wrong clinical message. We came across one such erratum [1] which had the potential to change the message in the original article [2]. We searched, therefore, all the issues of Anaesthesia from 1996 to 2006 and found 37 errata published. These included omissions, spelling mistakes, printing mistakes, typing errors, and wrongly cited references, etc. Perhaps one should not be surprised that a small error can lead to a markedly different message, and journals rightly insert the correct version in a subsequent issue. What is interesting to note is that there is no way of connecting the original article with the subsequently published correction, even using the Blackwell Synergy online service. When manually searching for the errata, we found that where and how they are inserted varies from journal to journal. In Anaesthesia these are generally printed on the last page of an issue, although this is not consistent. Furthermore, when reading an issue of a journal, if a reader comes across an erratum we wonder how many would relate this to the original article and see if it changes the conclusion. The article cited above [2] is one of the 20 most read articles in the last 12 months. Yet, on the contents page there is no indication of the erratum published in a later issue of the journal, which has the potential to change the clinical message. It is only when the full text link is followed that one will see at the end that the article is cited by another article. One would think that with recent advances in computing technology it would be possible to provide a link to the erratum alongside the original article.