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Anaesthetic management of diabetes
ENDOCRINOLOGY
Anaesthetic management of diabetes
Learning objectives After reading this article, you should be able to: C explain two different pathophysiologies of diabetes C describe five long-term complications of diabetes C describe three different treatment strategies available for diabetics
Inas Ahmed Swamy Mruthunjaya
Abstract Diabetes is a complex metabolic disorder that is increasing in incidence globally. It is the most common non-communicable disease worldwide. Diabetic patients pose a challenge to anaesthesia and surgery due to the organs and systems affected by the disease. Good glycaemic control perioperatively is essential to minimize complications. There is an increasing number of therapies to control diabetes, and this is rapidly evolving, so a multidisciplinary approach to the management of these patients is recommended, and increasingly the patients themselves should be participating in managing their diabetes as long as possible.
may lead to retinopathy, nephropathy, peripheral neuropathy and autonomic neuropathy.
Categories of diabetes Type 1 Immune-mediated: this has an incidence of 5e10% and results from an absolute deficiency in the production of insulin resulting from a destructive autoimmune process that targets the islets of Langerhans in the pancreas. These patients can be identified by genetic markers or serological evidence of the autoimmune process causing the disease.
Keywords Diabetes; fasting blood sugar; glycated haemoglobin; insulin; oral hypoglycaemics; variable rate intravenous insulin infusion Royal College of Anaesthetists CPD matrix: 1A01, 1A02, 2A03, 2G01, 3J00
Type 2 The prevalence of type 2 diabetes is 90e95% and results from a combination of peripheral resistance to insulin and a relative insulin deficiency. Patients with type 2 diabetes differ from type 1 diabetics in that they often do not require insulin and are less likely to develop ketoacidosis. The aetiology of type 2 diabetes in not known and there is no evidence of it being related to autoimmune disease. Most type 2 diabetics are obese, which in itself increases insulin resistance. Such patients often go undiagnosed for years as the hyperglycaemia is gradual and the classic symptoms of diabetes are not evident.
Diabetes is a group of metabolic disorders that is characterized by hyperglycaemia. This may be due to defects in insulin secretion, insulin action, or both. Long-term, poorly controlled blood sugar results in multiorgan disease and failure, particularly the eyes, kidneys, nerves, heart, and blood vessels.
Pathophysiology Ultimately this is a failure of insulin acting on its target tissue with consequent abnormality in metabolizing carbohydrates, fat and protein. Several processes are involved and this ranges from deficient insulin production resulting from autoimmune destruction of the islets of Langerhans to a resistance to normal quantities of insulin peripherally. Often both processes coexist and it may be difficult to distinguish which is the primary reason for hyperglycaemia.
Gestational diabetes This has an incidence of 7%. Although traditionally defined as glucose intolerance first identified during pregnancy, more recently it was recommended that parturients who meet the criteria are diagnosed as overt rather than gestational diabetics. Figure 1 shows the different types of diabetes and the stages of hyperglycaemia associated with it. Box 1 demonstrates the aetiological classification of diabetes.
Clinical features
Pre-diabetes
Typically hyperglycaemia is associated with polyuria, polydipsia and weight loss. It may also be associated with polyphagia, blurred vision and susceptibility to infections. Diabetic patients may present as medical emergencies in the form of any of the diabetic comas. These may be hypoglycaemic, diabetic ketoacidosis or hyperosmolar non-ketotic coma. Features of long-term disease will depend on the organs affected and the extent of damage. The long-term complications
Patients whose blood tests do not meet the criteria of diabetes but are still higher than normal can be termed as pre-diabetics. Another test to identify high risk of diabetes is A1C (glycosylated haemoglobin), which is used to identify diabetes. This is a marker of glycaemic control over the preceding 3 months. A1C levels above normal but below the diabetes cutoff point (5.7e6.4 %) are at very high risk of developing diabetes.1 Diagnosis (Box 2).
Prevention and treatment
Inas Ahmed FRCA is a Specialty Registrar in Anaesthesia in the Northwest Deanery, UK. Conflict of interest: none declared.
Changing lifestyle: diet and exercise have been shown to be effective in reducing the incidence of diabetes. Antidiabetic agents
Swamy Mruthunjaya FCARCSI is a Locum Consultant Anaesthetist in Manchester Royal Infirmary, UK. Conflict of interest: none declared.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 15:10
453
Ó 2014 Elsevier Ltd. All rights reserved.
ENDOCRINOLOGY
Disorders of glycaemia: aetiologic types and stages
Stages Types
Normoglycaemia Normal glucose regulation
Hyperglycaemia Impaired glucose tolerance or Impaired fasting glucose (pre-diabetes)
Diabetes melitus Not insulin requiring
Insulin requiring for control
Insulin requiring for survival
Type 1* Type 2 Other specific types**
Gestational diabetes**
*Even after presenting in ketoacidosis, these patients can briefly return to normoglycaemia without requiring continuous therapy (i.e. ‘honeymoon’ remission); **in rare instances, patients in these categories may require insulin for survival (From Diabetes Care 2010; 33(Suppl 1) with kind permission.)
Figure 1
Glucagon-like peptide-1 (GLP-1) receptor agonists (e.g. exenatide): an oral challenge of glucose rather than IV challenge results in an augmented release of insulin. This is due to the incretins (intestine-derived peptides secreted in response to meals), which limit postprandial
glucose rises and decrease glucagon secretion. It is however rapidly degraded by enzymes. Dipeptidyl peptidase-IV (DPP-4) inhibitors (e.g. sitagliptin): the effect of the incretins is limited due to rapid
Summary of the diagnostic criteria for diabetes1,2
Aetiologic classification of diabetes mellitus
C C
Type 1 diabetes Immune-mediated Idiopathic
OR C
C C
C
Type 2 diabetes Other specific types Genetic defects of cell function Genetic defects in insulin action Diseases of the exocrine pancreas Endocrinopathies Drug or chemical induced Infections Uncommon forms of immune-mediated diabetes Other genetic syndromes sometimes associated with diabetes
Fasting plasma glucose 7.0 mmol/litre. (Fasting is defined as no caloric intake for at least 8 hours.)
OR C
2-hour plasma glucose 11.1 mmol/litre during an oral glucose tolerance test (OGTT). The test should be performed as described by the World Health Organization, using a glucose load containing the equivalent of 75 g anhydrous glucose dissolved in water.
OR C
Gestational diabetes mellitus
The classification is taken from Diabetes care, 2010; 33(Suppl 1), with kind permission.
In a patient with classic symptoms of hyperglycemia or hyperglycaemic crisis, a random plasma glucose 11.1 mmol/litre.
From Diabetes care, 2010; 33 (Suppl 1), with kind permission.
Box 1
ANAESTHESIA AND INTENSIVE CARE MEDICINE 15:10
HbA1C 6.5%
Box 2
454
Ó 2014 Elsevier Ltd. All rights reserved.
ENDOCRINOLOGY
deactivation by DPP-4, which is widely available in the body. These drugs prevent the inactivation of GLP-1 and prolong the effect of the endogenously secreted incretin. Thiazolidinediones (e.g. pioglitazone): this is an insulin sensitizer, which acts by increasing the efficiency of glucose transporters. This group of drugs acts by activating peroxisome proliferator activated g nuclear receptors particularly on fat and muscles. This results in altered gene transcription in fat cells and reducing free fatty acids. This in turn is believed to enhance the insulin e receptor signalling in skeletal muscle therefore insulin sensitivity throughout the body. Other potential benefits include fat redistribution from visceral to subcutaneous, which reduces cardiovascular risk. In addition, this group has anti-inflammatory effects and improves hypertension and coronary vascular endothelial function. Thiazolidinediones have been associated with an increased incidence of myocardial infarction. Insulin analogues: the principle of management with insulin is to mimic the physiological pattern of insulin secretion in normal people so it covers both the basal rate and the postprandial response. This is used as mainstay of treatment for type 1 diabetes, and as an additional tool in type 2 diabetes. Besides achieving glycaemic control, insulin improves insulin resistance and offers cardiovascular benefits. Fast-acting analogues (e.g. lispro): this usually has a rapid onset of action ranging from 5 to 15 minutes. It reaches peak activity 2 hours after injection, and duration of action does not exceed 5 hours. Long-acting analogues (e.g. glargine): prolonged effect is a result of a decreased solubility resulting in a slow release from the site of injection and a prolonged effect. Biguanides (e.g. metformin): this improves insulin sensitivity particularly in skeletal muscle. Other advantages include decreasing hepatic gluconeogenesis and decreasing glycogenolysis. It is associated with weight loss, decreasing cardiovascular risk factor and cancer risk. Sulphonylureas (e.g. glibenclamide): sulphonylureas act by both stimulating insulin release and improving peripheral sensitivity to insulin. Meglitinides (e.g. glinides): meglitinides act by stimulating rapid insulin production. They have a quicker onset and shorter duration compared to sulphonylureas. a-glucosidase inhibitors (e.g. acarbose): acarbose blocks a glucosidase enzyme, which is present in the brush border of the small intestine. This results in delayed absorption of glucose so decreases postprandial glucose surges. Synthetic amylin analogues (e.g. pramlintide): amylin is a neurohormone that is released from the pancreas with insulin, therefore is deficient in type 1 diabetes. Amylin is released in response to food in the intestine, and its pattern of secretion closely resembles that of insulin. Amylin causes a decreased glucagon secretion, a delay in gastric emptying and induces the feeling of satiety. In addition it slows the absorption of glucose
ANAESTHESIA AND INTENSIVE CARE MEDICINE 15:10
from the insulin therefore allowing the insulin to exercise glycaemic control. Pramlintide resembles amylin and is administered as a subcutaneous injection two or three times daily before meals.3 Surgery Bariatric surgery: this is indicated for patients with type 2 diabetes and a body mass index of 35. It has been reported that such surgeries produce a significant improvement, even remission of type 2 diabetes. These are increasingly laparoscopic procedures, and complications include anastomotic leak, wound infection, haemorrhage and pulmonary complications, as well as nutritional deficiencies. Pancreas transplant: this is usually associated with a simultaneous kidney transplant to treat the diabetic nephropathy and so excludes elderly patients and those with severe coronary artery disease due to the increase surgical morbidity associated with such a major surgery. Side effects include haemorrhage, failed graft and lifelong immunosuppression.4 Allogenic islet transplantation: may be an appropriate alternative to those patients who are unwilling or unwell enough to undergo a pancreas transplant. This often results in insulin independence, but even when that is not achieved, a significantly better glycaemic control is achieved.5
Why diabetes challenges anaesthesia and surgery Multiple associated co-morbidities and multi-systems affected. Obesity. Cardiovascular risk factors and the increased possibility of developing silent myocardial ischaemia. Stiff joint syndrome may cause difficult airways. Autonomic neuropathy may result in gastroparesis increasing the risk of aspiration. Nephropathy may limit the use of intraoperative and postoperative non-steroidal anti-inflammatory drugs. Glycaemic control needs to be maintained both intraoperatively and postoperatively. These patients are also more prone to wound infections. Poor preoperative glycaemic control was associated with increased postoperative complications, including increased need for blood products and longer critical care and hospital stay.
Preoperative assessment and preparation A thorough history covering a system review with emphasis on cardiac, renal and neurological systems is carried out, in addition to an assessment of adequacy of diabetic control. Comorbidities should therefore be identified, investigated and optimized. Following a full examination, a battery of tests is usually requested including full blood count, renal profile and an ECG is carried out. Further cardiac investigations may be carried out including echocardiogram and stress testing. It is important to ensure glycaemic control is optimized before surgery and a diabetes management plan is present for the perioperative
455
Ó 2014 Elsevier Ltd. All rights reserved.
ENDOCRINOLOGY
period. Ideally, such a plan should be multidisciplinary and involve the patient and the diabetes specialist team. In most organizations this will mean the use of protocols or guidelines to guide management. High-risk patients are identified and appropriate post-operative plans set in place, which may include high-dependency or intensive care treatment. Some units recommend the cessation of metformin 24 hours preoperatively to minimize the chance of lactic acidosis. Increasingly, it is now being recommended to maintain glycaemic control in the elective surgical patient by manipulating the patient’s usual medication. This however requires the fulfilment of a few criteria, which are: surgery can be carried out early on a morning or afternoon list short starvation period (only one missed meal) good diabetes control prior to admission (HbA1C <8.5%) high probability that the patient will self-manage their diabetes during the immediate post-operative period. If the patient is normally treated with insulin, the variable rate intravenous insulin infusion (VRII) should not be discontinued until a short-acting bolus has been given and background insulin is in place. It is recommended that if the patient is on long-acting insulin, that this would be maintained alongside a VRII. If a VRII is used, it is suggested to use 0.45% sodium chloride and 5% glucose with either 0.15 or 0.3% potassium chloride as the fluid of choice. Capillary blood glucose (CBG) acceptable targets are 4e12 mmol/litre and it is advisable to avoid peaks and troughs in glycaemic control.
the hyperchloraemic metabolic acidosis. Glucose-containing solutions should only be administered in hypoglycaemia. Promote early return to normal diet. It is recommended to use multimodal analgesic techniques and administer antiemetics to encourage the patient to go back to oral intake and take over their diabetes management as soon as possible.
Postoperative care In recovery and the ward Follow the same principles as before, maintaining volume status and electrolyte balance. CBG regularly accepting a blood sugar of 4e12 mmol/litre, and encouraging patient to start oral intake and take over their management of diabetes. It is no longer recommended to delay discharge due to hyperglycaemia only, as the patient’s ability to manage themselves should be considered. Support from the diabetes specialist team should also be available.
In emergency surgery The lack of time for appropriate planning makes this even more challenging. It is recommended that if the patient was taking long-acting insulin that this be continued. If blood glucose rises above 10 mmol/litre, it is advised to start VVII and that this should continue till the patient is eating and drinking. To assist in subsequent diabetes management, it is wise to assess A1C.6e8
New technologies More and more patients are now receiving continuous subcutaneous insulin infusion (CSII) therapy (also called insulin pump therapy) to achieve glycaemic control. Some units have now incorporated these pumps in the perioperative care. Some criteria must be met including the availability of the patient’s insulin and pumps for the duration of the hospital stay and the anaesthetic, recovery and surgical team’s comfort using these pumps and achieving glycaemic control with it. However, it is recommended to be removed if radiology is ever required and for emergency procedures. Some manufacturers also prohibit the use of electrocautery, so this needs to be taken into consideration.9
Intraoperative Anaesthetic technique: standard monitoring in the form of ECG, pulse oximetry, capnography and gas analysis is indicated, as with any operation. In addition to securing IV access, invasive monitoring with arterial and central venous catheters may be indicated. Non-invasive cardiac output monitoring should be considered. Central neuraxial blocks in the form of spinal or epidural may be helpful in conjunction with general anaesthesia, after a thorough documentation of any pre-existing neurological defects. Regional anaesthesia should always be considered, particularly in patients with suspected difficult airway due to stiff joint syndrome. This would offer the added advantages of decreasing stress response and blood loss, decreasing thrombo-embolic risk and importantly an early return to oral intake.
Continuous glucose monitoring and closed-loop system This is glycaemic control system that consists of pumps for the insulin infusion and a glucose sensor for glucose level monitoring. This feeds into computerized algorithms, which regulate further insulin release. This system provides better glycaemic control, and some units are incorporating its use in the perioperative period particularly in the day surgery setting. Disadvantages to its use include costs and preparation time.10 A
Equipment: body and fluid warmers must be available. Rapid infusers, and blood products should be made available if the surgery requires it. Maintaining glycaemic control: capillary blood glucose should be checked before induction and hourly after that throughout the procedure. Hyperglycaemia can be treated by either subcutaneous insulin or variable rate intravenous insulin infusion (VRII).
REFERENCES 1 Inzucchi S, Bergenstal R, Fonseca V, et al. Diagnosis and classification of diabetes mellitus. Diabetes Care 2010; 33: 62e72. 2 Valentine NA, Alhawassi TA, Roberts GW, et al. Detecting undiagnosed diabetes using glycated haemoglobin: an automated screening test in hospitalized patients. Med J Aust 2011; 194: 160e4.
Maintaining intravascular volume: it is important to maintain intravascular volume and keep electrolytes within normal range. Hartmann’s solution can be used over 0.9% saline to minimize
ANAESTHESIA AND INTENSIVE CARE MEDICINE 15:10
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Ó 2014 Elsevier Ltd. All rights reserved.
ENDOCRINOLOGY
3 Nicholson G, Hall GM. Diabetes mellitus: new drugs for a new epidemic. Br J Anaesth 2011; 1: 65e73. 4 Rubino F, Kaplan LM, Schauer PR, et al. The Diabetes Surgery Summit consensus conference. Recommendations for the evaluation and use of gastrointestinal surgery to treat type 2 diabetes mellitus. Ann Surg 2010; 251: 399e405. 5 Barton FB, Rickels MR, Alejandro R, et al. Improvement in outcomes of clinical islet transplantation:1999-2010. Diab Care 2012; 35: 1436e45. 6 Bajwa SS, Kalra S. Diabeto-anaesthesia: a subspecialty needing endocrine introspection. Indian J Anaesth 2012; 56: 513e7. 7 Dhatariya K, Levy N, Kilvert A, et al. Diabetes UK position statements and care recommendations. NHS diabetes guideline for the
ANAESTHESIA AND INTENSIVE CARE MEDICINE 15:10
perioperative management of the adult patient with diabetes. Diabet Med 2012; 29: 420e33. 8 Wong J, Zoungas S, Wright C, et al. Evidence-based guidelines for perioperative management of diabetes in cardiac and vascular surgery. World J Surg 2010; 34: 500e13. 9 Boyle M, Seifert KM, Beer KA, et al. Guidelines for application of continuous subcutaneous insulin infusion (insulin pump) therapy in the perioperative period. J Diabetes Sci Technol 2012; 6: 184e90. 10 Pichardo-Lowden A, Gabbay RA. Management of hyperglycemia during the perioperative period. Curr Diab Rep 2012; 12: 108e18.
457
Ó 2014 Elsevier Ltd. All rights reserved.
Anaesthetic management of diabetes
Learning objectives After reading this article, you should be able to: C explain two different pathophysiologies of diabetes C describe five long-term complications of diabetes C describe three different treatment strategies available for diabetics
Inas Ahmed Swamy Mruthunjaya
Abstract Diabetes is a complex metabolic disorder that is increasing in incidence globally. It is the most common non-communicable disease worldwide. Diabetic patients pose a challenge to anaesthesia and surgery due to the organs and systems affected by the disease. Good glycaemic control perioperatively is essential to minimize complications. There is an increasing number of therapies to control diabetes, and this is rapidly evolving, so a multidisciplinary approach to the management of these patients is recommended, and increasingly the patients themselves should be participating in managing their diabetes as long as possible.
may lead to retinopathy, nephropathy, peripheral neuropathy and autonomic neuropathy.
Categories of diabetes Type 1 Immune-mediated: this has an incidence of 5e10% and results from an absolute deficiency in the production of insulin resulting from a destructive autoimmune process that targets the islets of Langerhans in the pancreas. These patients can be identified by genetic markers or serological evidence of the autoimmune process causing the disease.
Keywords Diabetes; fasting blood sugar; glycated haemoglobin; insulin; oral hypoglycaemics; variable rate intravenous insulin infusion Royal College of Anaesthetists CPD matrix: 1A01, 1A02, 2A03, 2G01, 3J00
Type 2 The prevalence of type 2 diabetes is 90e95% and results from a combination of peripheral resistance to insulin and a relative insulin deficiency. Patients with type 2 diabetes differ from type 1 diabetics in that they often do not require insulin and are less likely to develop ketoacidosis. The aetiology of type 2 diabetes in not known and there is no evidence of it being related to autoimmune disease. Most type 2 diabetics are obese, which in itself increases insulin resistance. Such patients often go undiagnosed for years as the hyperglycaemia is gradual and the classic symptoms of diabetes are not evident.
Diabetes is a group of metabolic disorders that is characterized by hyperglycaemia. This may be due to defects in insulin secretion, insulin action, or both. Long-term, poorly controlled blood sugar results in multiorgan disease and failure, particularly the eyes, kidneys, nerves, heart, and blood vessels.
Pathophysiology Ultimately this is a failure of insulin acting on its target tissue with consequent abnormality in metabolizing carbohydrates, fat and protein. Several processes are involved and this ranges from deficient insulin production resulting from autoimmune destruction of the islets of Langerhans to a resistance to normal quantities of insulin peripherally. Often both processes coexist and it may be difficult to distinguish which is the primary reason for hyperglycaemia.
Gestational diabetes This has an incidence of 7%. Although traditionally defined as glucose intolerance first identified during pregnancy, more recently it was recommended that parturients who meet the criteria are diagnosed as overt rather than gestational diabetics. Figure 1 shows the different types of diabetes and the stages of hyperglycaemia associated with it. Box 1 demonstrates the aetiological classification of diabetes.
Clinical features
Pre-diabetes
Typically hyperglycaemia is associated with polyuria, polydipsia and weight loss. It may also be associated with polyphagia, blurred vision and susceptibility to infections. Diabetic patients may present as medical emergencies in the form of any of the diabetic comas. These may be hypoglycaemic, diabetic ketoacidosis or hyperosmolar non-ketotic coma. Features of long-term disease will depend on the organs affected and the extent of damage. The long-term complications
Patients whose blood tests do not meet the criteria of diabetes but are still higher than normal can be termed as pre-diabetics. Another test to identify high risk of diabetes is A1C (glycosylated haemoglobin), which is used to identify diabetes. This is a marker of glycaemic control over the preceding 3 months. A1C levels above normal but below the diabetes cutoff point (5.7e6.4 %) are at very high risk of developing diabetes.1 Diagnosis (Box 2).
Prevention and treatment
Inas Ahmed FRCA is a Specialty Registrar in Anaesthesia in the Northwest Deanery, UK. Conflict of interest: none declared.
Changing lifestyle: diet and exercise have been shown to be effective in reducing the incidence of diabetes. Antidiabetic agents
Swamy Mruthunjaya FCARCSI is a Locum Consultant Anaesthetist in Manchester Royal Infirmary, UK. Conflict of interest: none declared.
ANAESTHESIA AND INTENSIVE CARE MEDICINE 15:10
453
Ó 2014 Elsevier Ltd. All rights reserved.
ENDOCRINOLOGY
Disorders of glycaemia: aetiologic types and stages
Stages Types
Normoglycaemia Normal glucose regulation
Hyperglycaemia Impaired glucose tolerance or Impaired fasting glucose (pre-diabetes)
Diabetes melitus Not insulin requiring
Insulin requiring for control
Insulin requiring for survival
Type 1* Type 2 Other specific types**
Gestational diabetes**
*Even after presenting in ketoacidosis, these patients can briefly return to normoglycaemia without requiring continuous therapy (i.e. ‘honeymoon’ remission); **in rare instances, patients in these categories may require insulin for survival (From Diabetes Care 2010; 33(Suppl 1) with kind permission.)
Figure 1
Glucagon-like peptide-1 (GLP-1) receptor agonists (e.g. exenatide): an oral challenge of glucose rather than IV challenge results in an augmented release of insulin. This is due to the incretins (intestine-derived peptides secreted in response to meals), which limit postprandial
glucose rises and decrease glucagon secretion. It is however rapidly degraded by enzymes. Dipeptidyl peptidase-IV (DPP-4) inhibitors (e.g. sitagliptin): the effect of the incretins is limited due to rapid
Summary of the diagnostic criteria for diabetes1,2
Aetiologic classification of diabetes mellitus
C C
Type 1 diabetes Immune-mediated Idiopathic
OR C
C C
C
Type 2 diabetes Other specific types Genetic defects of cell function Genetic defects in insulin action Diseases of the exocrine pancreas Endocrinopathies Drug or chemical induced Infections Uncommon forms of immune-mediated diabetes Other genetic syndromes sometimes associated with diabetes
Fasting plasma glucose 7.0 mmol/litre. (Fasting is defined as no caloric intake for at least 8 hours.)
OR C
2-hour plasma glucose 11.1 mmol/litre during an oral glucose tolerance test (OGTT). The test should be performed as described by the World Health Organization, using a glucose load containing the equivalent of 75 g anhydrous glucose dissolved in water.
OR C
Gestational diabetes mellitus
The classification is taken from Diabetes care, 2010; 33(Suppl 1), with kind permission.
In a patient with classic symptoms of hyperglycemia or hyperglycaemic crisis, a random plasma glucose 11.1 mmol/litre.
From Diabetes care, 2010; 33 (Suppl 1), with kind permission.
Box 1
ANAESTHESIA AND INTENSIVE CARE MEDICINE 15:10
HbA1C 6.5%
Box 2
454
Ó 2014 Elsevier Ltd. All rights reserved.
ENDOCRINOLOGY
deactivation by DPP-4, which is widely available in the body. These drugs prevent the inactivation of GLP-1 and prolong the effect of the endogenously secreted incretin. Thiazolidinediones (e.g. pioglitazone): this is an insulin sensitizer, which acts by increasing the efficiency of glucose transporters. This group of drugs acts by activating peroxisome proliferator activated g nuclear receptors particularly on fat and muscles. This results in altered gene transcription in fat cells and reducing free fatty acids. This in turn is believed to enhance the insulin e receptor signalling in skeletal muscle therefore insulin sensitivity throughout the body. Other potential benefits include fat redistribution from visceral to subcutaneous, which reduces cardiovascular risk. In addition, this group has anti-inflammatory effects and improves hypertension and coronary vascular endothelial function. Thiazolidinediones have been associated with an increased incidence of myocardial infarction. Insulin analogues: the principle of management with insulin is to mimic the physiological pattern of insulin secretion in normal people so it covers both the basal rate and the postprandial response. This is used as mainstay of treatment for type 1 diabetes, and as an additional tool in type 2 diabetes. Besides achieving glycaemic control, insulin improves insulin resistance and offers cardiovascular benefits. Fast-acting analogues (e.g. lispro): this usually has a rapid onset of action ranging from 5 to 15 minutes. It reaches peak activity 2 hours after injection, and duration of action does not exceed 5 hours. Long-acting analogues (e.g. glargine): prolonged effect is a result of a decreased solubility resulting in a slow release from the site of injection and a prolonged effect. Biguanides (e.g. metformin): this improves insulin sensitivity particularly in skeletal muscle. Other advantages include decreasing hepatic gluconeogenesis and decreasing glycogenolysis. It is associated with weight loss, decreasing cardiovascular risk factor and cancer risk. Sulphonylureas (e.g. glibenclamide): sulphonylureas act by both stimulating insulin release and improving peripheral sensitivity to insulin. Meglitinides (e.g. glinides): meglitinides act by stimulating rapid insulin production. They have a quicker onset and shorter duration compared to sulphonylureas. a-glucosidase inhibitors (e.g. acarbose): acarbose blocks a glucosidase enzyme, which is present in the brush border of the small intestine. This results in delayed absorption of glucose so decreases postprandial glucose surges. Synthetic amylin analogues (e.g. pramlintide): amylin is a neurohormone that is released from the pancreas with insulin, therefore is deficient in type 1 diabetes. Amylin is released in response to food in the intestine, and its pattern of secretion closely resembles that of insulin. Amylin causes a decreased glucagon secretion, a delay in gastric emptying and induces the feeling of satiety. In addition it slows the absorption of glucose
ANAESTHESIA AND INTENSIVE CARE MEDICINE 15:10
from the insulin therefore allowing the insulin to exercise glycaemic control. Pramlintide resembles amylin and is administered as a subcutaneous injection two or three times daily before meals.3 Surgery Bariatric surgery: this is indicated for patients with type 2 diabetes and a body mass index of 35. It has been reported that such surgeries produce a significant improvement, even remission of type 2 diabetes. These are increasingly laparoscopic procedures, and complications include anastomotic leak, wound infection, haemorrhage and pulmonary complications, as well as nutritional deficiencies. Pancreas transplant: this is usually associated with a simultaneous kidney transplant to treat the diabetic nephropathy and so excludes elderly patients and those with severe coronary artery disease due to the increase surgical morbidity associated with such a major surgery. Side effects include haemorrhage, failed graft and lifelong immunosuppression.4 Allogenic islet transplantation: may be an appropriate alternative to those patients who are unwilling or unwell enough to undergo a pancreas transplant. This often results in insulin independence, but even when that is not achieved, a significantly better glycaemic control is achieved.5
Why diabetes challenges anaesthesia and surgery Multiple associated co-morbidities and multi-systems affected. Obesity. Cardiovascular risk factors and the increased possibility of developing silent myocardial ischaemia. Stiff joint syndrome may cause difficult airways. Autonomic neuropathy may result in gastroparesis increasing the risk of aspiration. Nephropathy may limit the use of intraoperative and postoperative non-steroidal anti-inflammatory drugs. Glycaemic control needs to be maintained both intraoperatively and postoperatively. These patients are also more prone to wound infections. Poor preoperative glycaemic control was associated with increased postoperative complications, including increased need for blood products and longer critical care and hospital stay.
Preoperative assessment and preparation A thorough history covering a system review with emphasis on cardiac, renal and neurological systems is carried out, in addition to an assessment of adequacy of diabetic control. Comorbidities should therefore be identified, investigated and optimized. Following a full examination, a battery of tests is usually requested including full blood count, renal profile and an ECG is carried out. Further cardiac investigations may be carried out including echocardiogram and stress testing. It is important to ensure glycaemic control is optimized before surgery and a diabetes management plan is present for the perioperative
455
Ó 2014 Elsevier Ltd. All rights reserved.
ENDOCRINOLOGY
period. Ideally, such a plan should be multidisciplinary and involve the patient and the diabetes specialist team. In most organizations this will mean the use of protocols or guidelines to guide management. High-risk patients are identified and appropriate post-operative plans set in place, which may include high-dependency or intensive care treatment. Some units recommend the cessation of metformin 24 hours preoperatively to minimize the chance of lactic acidosis. Increasingly, it is now being recommended to maintain glycaemic control in the elective surgical patient by manipulating the patient’s usual medication. This however requires the fulfilment of a few criteria, which are: surgery can be carried out early on a morning or afternoon list short starvation period (only one missed meal) good diabetes control prior to admission (HbA1C <8.5%) high probability that the patient will self-manage their diabetes during the immediate post-operative period. If the patient is normally treated with insulin, the variable rate intravenous insulin infusion (VRII) should not be discontinued until a short-acting bolus has been given and background insulin is in place. It is recommended that if the patient is on long-acting insulin, that this would be maintained alongside a VRII. If a VRII is used, it is suggested to use 0.45% sodium chloride and 5% glucose with either 0.15 or 0.3% potassium chloride as the fluid of choice. Capillary blood glucose (CBG) acceptable targets are 4e12 mmol/litre and it is advisable to avoid peaks and troughs in glycaemic control.
the hyperchloraemic metabolic acidosis. Glucose-containing solutions should only be administered in hypoglycaemia. Promote early return to normal diet. It is recommended to use multimodal analgesic techniques and administer antiemetics to encourage the patient to go back to oral intake and take over their diabetes management as soon as possible.
Postoperative care In recovery and the ward Follow the same principles as before, maintaining volume status and electrolyte balance. CBG regularly accepting a blood sugar of 4e12 mmol/litre, and encouraging patient to start oral intake and take over their management of diabetes. It is no longer recommended to delay discharge due to hyperglycaemia only, as the patient’s ability to manage themselves should be considered. Support from the diabetes specialist team should also be available.
In emergency surgery The lack of time for appropriate planning makes this even more challenging. It is recommended that if the patient was taking long-acting insulin that this be continued. If blood glucose rises above 10 mmol/litre, it is advised to start VVII and that this should continue till the patient is eating and drinking. To assist in subsequent diabetes management, it is wise to assess A1C.6e8
New technologies More and more patients are now receiving continuous subcutaneous insulin infusion (CSII) therapy (also called insulin pump therapy) to achieve glycaemic control. Some units have now incorporated these pumps in the perioperative care. Some criteria must be met including the availability of the patient’s insulin and pumps for the duration of the hospital stay and the anaesthetic, recovery and surgical team’s comfort using these pumps and achieving glycaemic control with it. However, it is recommended to be removed if radiology is ever required and for emergency procedures. Some manufacturers also prohibit the use of electrocautery, so this needs to be taken into consideration.9
Intraoperative Anaesthetic technique: standard monitoring in the form of ECG, pulse oximetry, capnography and gas analysis is indicated, as with any operation. In addition to securing IV access, invasive monitoring with arterial and central venous catheters may be indicated. Non-invasive cardiac output monitoring should be considered. Central neuraxial blocks in the form of spinal or epidural may be helpful in conjunction with general anaesthesia, after a thorough documentation of any pre-existing neurological defects. Regional anaesthesia should always be considered, particularly in patients with suspected difficult airway due to stiff joint syndrome. This would offer the added advantages of decreasing stress response and blood loss, decreasing thrombo-embolic risk and importantly an early return to oral intake.
Continuous glucose monitoring and closed-loop system This is glycaemic control system that consists of pumps for the insulin infusion and a glucose sensor for glucose level monitoring. This feeds into computerized algorithms, which regulate further insulin release. This system provides better glycaemic control, and some units are incorporating its use in the perioperative period particularly in the day surgery setting. Disadvantages to its use include costs and preparation time.10 A
Equipment: body and fluid warmers must be available. Rapid infusers, and blood products should be made available if the surgery requires it. Maintaining glycaemic control: capillary blood glucose should be checked before induction and hourly after that throughout the procedure. Hyperglycaemia can be treated by either subcutaneous insulin or variable rate intravenous insulin infusion (VRII).
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Maintaining intravascular volume: it is important to maintain intravascular volume and keep electrolytes within normal range. Hartmann’s solution can be used over 0.9% saline to minimize
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3 Nicholson G, Hall GM. Diabetes mellitus: new drugs for a new epidemic. Br J Anaesth 2011; 1: 65e73. 4 Rubino F, Kaplan LM, Schauer PR, et al. The Diabetes Surgery Summit consensus conference. Recommendations for the evaluation and use of gastrointestinal surgery to treat type 2 diabetes mellitus. Ann Surg 2010; 251: 399e405. 5 Barton FB, Rickels MR, Alejandro R, et al. Improvement in outcomes of clinical islet transplantation:1999-2010. Diab Care 2012; 35: 1436e45. 6 Bajwa SS, Kalra S. Diabeto-anaesthesia: a subspecialty needing endocrine introspection. Indian J Anaesth 2012; 56: 513e7. 7 Dhatariya K, Levy N, Kilvert A, et al. Diabetes UK position statements and care recommendations. NHS diabetes guideline for the
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perioperative management of the adult patient with diabetes. Diabet Med 2012; 29: 420e33. 8 Wong J, Zoungas S, Wright C, et al. Evidence-based guidelines for perioperative management of diabetes in cardiac and vascular surgery. World J Surg 2010; 34: 500e13. 9 Boyle M, Seifert KM, Beer KA, et al. Guidelines for application of continuous subcutaneous insulin infusion (insulin pump) therapy in the perioperative period. J Diabetes Sci Technol 2012; 6: 184e90. 10 Pichardo-Lowden A, Gabbay RA. Management of hyperglycemia during the perioperative period. Curr Diab Rep 2012; 12: 108e18.
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