Perioperative Management of Diabetes and the Emerging Role of Anaesthetists as Perioperative Physicians

Authors: N. Levy; N et al

Br J Anaesth. 2016;116(4):443-447.

Diabetes is the most common metabolic disorder and affects about 6–7% of the population and about 16% of the inpatient population.^[1,2] Diabetes leads to accelerated atherosclerosis and patients are at higher risk of renal impairment, coronary vascular disease, peripheral vascular disease and cerebro-vascular disease. Subsequently, the surgical patient with diabetes is at higher risk of perioperative morbidity and mortality and subsequently longer length of hospital stays.^[3–13] The reasons for this excess morbidity and mortality is multifactorial and includes increased risks of Hypoglycaemia and hyperglycaemia,^[3–15] infective complications (both surgical site infections (SSIs) and systemic infections),^[3–13] medical complications including acute kidney injury (AKI), acute coronary syndromes (ACS) and acute cerebro-vascular events,^[3–13] hospital acquired diabetic ketoacidosis (DKA),^[2,16] use of variable rate i.v. insulin infusion (VRIII),^[2,14]misuse of insulin,^[17,18] complex polypharmacy^[2,14] and multiple co-morbidities including microvascular and macrovascular complications of the diabetes.^[4,5]

On the basis of these concerns, NHS Diabetes commissioned the Joint British Diabetes Societies (JBDS) to produce guidance to optimise the management of the surgical patient with diabetes with the explicit aim of reducing the incidence of hypoglycaemia and hyperglycaemia, the risk of medical and infective complications, the risk of insulin and VRIII related harm and reducing the excess length of stay.^[5]

The JBDS proposed the concept of the comprehensive care pathway for the management of the surgical patient with diabetes and utilised the enhanced recovery programme’s concept of a multi-disciplinary pathway starting with the general practitioner (GP) and finishing at discharge (Fig. 1).^[5] When the guidelines were first published in 2011 there were no prospective studies on which to base recommendations. It was necessary to reflect on current practice and reject policies that were clearly associated with harm. The main recommendations of the JBDS recommendations were:

• Promote day surgery and day of surgery admission when and where possible. This was based on the simple premise that if a patient is not in hospital it is less likely for iatrogenic harm to occur. It was also recognised that there was a widespread regional variation of care. Whilst some hospitals actively encouraged the elective surgical patient with diabetes to be managed in day surgery units (DSU), and managed these patients very well, many DSUs actively discouraged day surgery for any patient with diabetes.^[19,20]
• Promote self-medication, if possible, as many patients are often more knowledgeable than ward medical and nursing staff about their own medical conditions, and have a vested interest to self -medicate properly.^[21]
• Avoid the use of sliding scales/VRIII when and where possible, and that modification of the patient’s usual diabetes medication was preferable. This modification should be agreed in the PAU
• Indications for the use of the VRIII include poor glycaemic control and anticipated prolonged starvation (defined as missing more than two meals).
• Every hospital should have guidelines to promote the safe use of the VRIII.
• To prevent iatrogenic hyponatraemia and hypokalaemia,^[22]the maintenance fluid whilst on a VRIII should be 5% glucose in 0.45% saline with either 0.15 or 0.3% potassium chloride based on daily electrolyte assessment.
• Promote the concept that ideal capillary blood glucose (CBG) should be 6–10 mmol litre⁻¹, and that an acceptable CBG is 4–12 mmol litre⁻¹.
• To prevent neuroglycopaenia in the unconscious state, the CBG should be measured hourly.
• Promote the concept that the elective patient should have an glycated haemoglobin (HbA1c) of <8.5% (69 mmol mol⁻¹) where practically possible.^[5]

 

Comprehensive Care pathway for the elective surgical patient with diabetes.

The authors of the JBDS guidelines recognise that there are no studies to demonstrate that actively lowering an elevated HbA1c improves outcome. However the following is acknowledged:

• Poor chronic preoperative glycaemic control as defined by elevated HbA1c is associated with a worse outcome.^[9–13]
• Poor acute perioperative glycaemic control as defined by elevated perioperative CBGs are associated with a worse outcome.^[3–8]
• Good long term preoperative glycaemic control allows in selected patients the diabetes to be safely managed without the VRIII (i.e. manipulation of normal diabetes medication), and thus promotes day surgery, and shorter length of hospital stays and shorter periods in which iatrogenic complications can occur.^[23]
• The VRIII is associated with iatrogenic complications (including hypoglycaemia; hyperglycaemia; DKA; extended stay^[2,14]hyponatraemia^[22,24] and death^[24–28]).
• Based on the above premises, a patient who has chronic poor glycaemic control (as defined as an elevated HbA1c) is more likely to suffer perioperative dysglycaemia and subsequently have a higher incidence of surgical site infection, systemic infections and other medical complications. Furthermore, they are more likely to be managed with a VRIII.
• Patients dislike and distrust the VRIII, and would prefer to avoid them if and when possible.
• Poor chronic glycaemic control as defined as an elevated HbA1c is associated with a worse outcome, and therefore allows identification of patients at higher risk of complications.^[9–13]Thus an elevated HbA1c will help identify patients that require a higher level of care postoperatively.

In this edition of the BJA, Jackson and colleagues²⁹ have reported a region-wide audit of the perioperative management of patients with diabetes undergoing elective surgery in the North West of England completed by NWARG (North West Research and Audit Group). This audit is one of the first major studies to originate from a trainee network. Eighty-five doctors and two audit clerks in 17 hospitals were involved in the audit, but of significant interest is that NWARG attracted no funding for this work. It illustrates the ability of trainee networks to gather large data rapidly, and creates the potential for collaborative projects between trainee networks and national guideline producing organizations. In addition it allowed local hospitals to benchmark themselves against regional practice and hence encourage change to local practices to improve compliance and so improve quality of care, in this case compliance with national diabetes guidance.

The report by Jackson and colleagues^[29] demonstrates the potential impact of the new anaesthetic trainee research networks. The first one being formed in 2012 in the South West.^[30] The Research and Audit Federation of Trainees (RAFT) is a supporting network for these regional groups whose number now approaches twenty organizations spread across the UK, and further information is available on the RAFT website.^[31] RAFT is a key element in the National Institute of Academic Anaesthesia (NIAA) strategy to support anaesthetic trainees involved in research to improve patient care.^[32] The aim is to increase the opportunities for all anaesthetic trainees to be involved in high impact research, which can be difficult outside of the major centres and with the rotational training programme necessary to deliver the entire curriculum. Research as defined in Annex G of the Curriculum for training in anaesthetics is a mandatory component of the curriculum.^[33] In addition RAFT is represented at Council and Board level in the NIAA and the Health Services Research Centre (HSRC). RAFT, via its associated regional groups, link to the Quality Audit and Research Co-ordinators (QuARCs) found in most NHS hospitals.

Over the two-week period in October 2013 all patients undergoing elective surgery at participating hospitals during the weekdays were eligible for inclusion for the study by Jackson and colleagues. Pregnant, paediatric and non-elective patients were excluded to align with National guidance; 247 patients with diabetes were identified and included. Of the captured eligible patients in the audit, 87% were seen in the preoperative assessment clinic. A preoperative HbA1c was recorded in 71%. 20% (34/168) of patients who had had their HbA1c recorded had an HbA1c greater than 69 mmol mol⁻¹.

Jackson and colleagues found that a CBG was performed before induction of anaesthesia in 93% of patients. The CBG was in the acceptable range (4 to 12 mmol litre⁻¹) in 89% and ideal range (6 to 10 mmol litre⁻¹) in 61%. Three patients had CBG less than 4 mmol litre⁻¹ and 22 patients had CBG greater than 12 mmol litre⁻¹. Intra-operative CBG were only available for 105/247 (43%) patients. During the operation, 50% of patients (53/105) were in the ideal range, 85% (89/105) were in the acceptable range. In recovery 73% (165/226) of patients had CBG recorded. Postoperative values were within the acceptable range in 91% (150/165) and in the ideal range for 55% (91/165) of patients.

The majority of patients returned to normal food and diet in a timely manner, with 57% (135/238) eating within one h of the end of surgery and a further 36% (86/238) planning. Only 7% (17/238) of patients did not eat the next meal, either because of a surgical decision or postoperative nausea or vomiting.

In the study by Jackson and colleagues only 8% (3/39) patients who had a VRIII, had the preferred fluid of 5% glucose in 0.45% saline with premixed potassium chloride to run concurrently. It is well recognized that the use of the VRIII is associated with hyponatremia because of insufficient saline in the substrate solution.^[22] A recently published study has attributed the higher incidence of hyponatraemia and death in surgical patients with diabetes as a result of the practice of administering only dextrose containing fluids to the surgical patient with diabetes whilst on a VRIII.^[24]

Jackson and colleagues have thus demonstrated that the guidance suggested by the JBDS in 2011 had not been adopted in their region by October 2013. Furthermore they have demonstrated that the non-adoption is associated with practice that is potentially harmful. One of the key recommendations of the JBDS guidelines was to keep the CBG in the ideal range of 6–10 mmol litre⁻¹ in an effort to prevent hypo- and hyperglycaemia. Hypoglycaemia is defined as capillary blood glucose less than 4 mmol litre⁻¹ (70 mg dl⁻¹) and in the patient with diabetes is caused by a relative excess of insulin or insulin secretins compared with carbohydrate intake. Hypoglycaemia is not a benign condition as demonstrated by the recent critical care studies in which intensive insulin therapy was used to aim for a CBG of 4–6 mmol litre⁻¹.^[25–28] The treatment groups all had harm and death associated with the tight glucose control and post hoc analysis of the Normoglycaemia in Intensive Care Evaluation – Survival Using Glucose Algorithm Regulation (NICE–SUGAR) Study has identified a CBG <4 mmol litre⁻¹ as being an independent risk factor for death.^[27]

Perioperative hyperglycaemia (as defined as CBG >10 mmol litre⁻¹ (180 mg dl⁻¹)) is associated with an increased risk of SSI, systemic infections and other medical complications of surgery including AKI and ACS. This association has been demonstrated in a number of surgical specialities.^[3–7]

In the study by Jackson and colleagues many patients routinely needlessly fasted for 10 to 16 h, resulting in more than one missed meal. There was also clearly considerable room to improve prioritization of patients with diabetes on operating lists; only 51% of patients were listed first. Minimizing interruptions to food and medication routines reduces the need for VRIII, improves perioperative glycaemic control and improves patient satisfaction. Jackson and colleagues suggest that in 69% (27/39) the use of the VRIII may not have been indicated. Equally worryingly they identified at least 10% (25 patients from their cohort of 238) who missed two or more meals and potentially should have had a VRIII. The VRIII is an offshoot of the Alberti GIK (glucose insulin potassium)^[34] regime and was never subjected to rigorous scientific studies before its widespread introduction. In theory, the VRIII has the potential for achieving excellent glycaemic control; however in reality the use of VRIII is associated with patient harm and death. Recent studies from the highly staffed critical care environment including the Van den Berghe studies; the efficacy of Volume Substitution and Insulin Therapy in Severe Sepsis (VISEP) and the NICE–SUGAR studies have demonstrated the use of the VRIII is associated with hypoglycaemia and death.^[25–28] Repeated national UK audits have also demonstrated that on the general ward it is associated with harm, and patients on the VRIII are often either hypoglycaemic or hyperglycaemic.^[2,14] This may be because of the fact that approximately one in 20 patients are having three or less CBG measurements per day. Furthermore issues with either delayed establishment of the VRIII or delayed administration of sub cutaneous insulin after discontinuation of the VRIII, have been identified, both potentially leading to DKA.^[2,14] Thus, the advice is to avoid the use of the VRIII when and where possible. Despite these concerns, there is currently no other viable option for managing diabetes in the surgical patient who has a prolonged starvation period, and in these patients the use of the VRIII is justified with the aim of preventing the deleterious effects of hyperglycaemia and DKA in the patient with type 1 diabetes.^[4,5]

Since the guidelines were published in 2011, several papers have been published that demonstrate the advantages of protocol-driven care for the surgical patient with diabetes. In one study (published only as an abstract), the authors audited the incidence of VRIII use and the manipulation of normal drugs use in the anaesthetic room before and after introduction of the national guidance to their District General Hospital, and the CBG in the anaesthetic room. Post introduction, they demonstrated significant reduction in VRIII use, and simultaneously the CBG was significantly more often in the acceptable range of 4–12 mmol litre⁻¹, and there was significantly less preoperative hypoglycaemia.^[35] In a retrospective study, the authors demonstrated that their preoperative manipulation of insulins was safe and effective and was not associated with hypoglycaemia or significant hyperglycaemia.^[36] In a prospective study, the authors demonstrated that basal insulins if reduced by 20% was a safe strategy to maintaining perioperative glycaemic control.^[37] There have also been several papers published that demonstrate that perioperative manipulation of the subcutaneous insulin infusion (CSII) pump therapy is safe and effective.^[38,39]

In 2015, the JBDS updated their guidelines^[4] (which the Royal College of Anaesthetists (RCoA) endorsed again). There were minor modifications to the dosing regimens taking into account feedback and new publications in the literature. More importantly after the publication of the post hoc analysis of NICE Sugar,^[27]which demonstrated a ‘dose – response relationship’ between the degree of hypoglycaemia and risk of death, the acceptable preoperative and intraoperative range has been narrowed to 6–12 mmol litre⁻¹, and values of <6 mmol litre⁻¹ should now be regarded as imminent hypoglycaemia and treated.

With the surgical population becoming both older and having more co-morbidities, the RCoA recognizes the need to improve the management of the surgical patient with co-morbidity. Traditionally, the care of the patients undergoing major surgery has been tailored to the operation itself and the disease being treated by the procedure. However the majority of complications which occur after surgery are not as a result of technical failures by the surgical team, but are often foreseeable medical complications secondary to an underlying disease process. Subsequently the RCoA established the collaborative Perioperative Medicine programme in 2014.^[40] The remit of the programme is to reduce variation and improve patient outcomes after surgery by having an integrated agenda and promoting a patient centred care pathway. This pathway is very similar to the pathway outlined in Fig. 1, but also identifies the fact that some patients never fully recover after major surgery. Thus, additionally, the Perioperative Medicine programme recognizes the fact that primary care services will need post discharge support and excellent communication from a team of hospital experts, who understand the impact of the major surgery on the individual patient and can help advise and co-ordinate ongoing medical issues that have arisen from the surgery. Guidelines for the Provision of Anaesthetic Services (GPAS) are being updated to promote the collaborative perioperative medicine programme.

GPAS forms the basis of recommendations produced by the Royal College of Anaesthetists for anaesthetists with managerial responsibilities for service, and for other healthcare managers.^[41] Subsequent to the Francis Enquiry, far reaching changes to the inspection process were introduced in 2013 by the Care Quality Commission (CQC). The CQC now inspects organizations using five domains underpinned by standard Key Lines of Enquiry (KLOEs). The organization must now be able to demonstrate that it is: safe; effective; caring; responsive and well led. In 2014, the RCoA mapped the standards that underpin Anaesthesia Clinical Services Accreditation (ACSA) to one or more of these five domains, thus integrating Guidelines for the Provision of Anaesthetic Services (GPAS) and ACSA with the requirements laid down by the CQC. The RCoA is again conducting the annual GPAS updating consultation, not only to advise on standards that should be adhered to, but also to ensure that that it will fulfil the standard criteria for accreditation by the National Institute for Health and Care Excellence (NICE). NICE accreditation requires a high level of evidence in recommendations, and this matches the desire of the College to promote evidence-based practice. In the future, departments that wish to be ACSA accredited, and pass CQC inspection will need to embrace GPAS.

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