Care of the diabetic surgical patient and the surgical patient on steroids.

Question 1

Specific perioperative problems in patients with diabetes

Answer 1

Predisposition to IHD

• Greater risk of perioperative MI, & has a substantially higher mortality, particularly females
• Infarction may be painless or ‘silent’ (possibly due to autonomic neuropathy)

Increased danger of cardiac arrest

• Due to autonomic neuropathy

Renal problems

• Predisposition to diabetic nephropathy
• Tendency to chronic renal failure

Predisposition to peripheral vascular disease

• Greater risk of perioperative strokes & lower limb ischaemia

Predisposition to heel pressure sores

• Especially if there is peripheral neuropathy and/or ischaemia

Increased incidence of postoperative infection

• In the wound, chest or urinary tract

Obesity

• Particularly common in T2D
• Associated with increased operative morbidity
• Stress (including surgery, trauma and infections) causes increased production of catabolic hormones which oppose the action of insulin (see Ch. 2 ), making diabetic control more difficult
• General anaesthesia, surgery, deprivation of oral intake and postoperative vomiting disrupt the delicate balance between dietary intake, exercise (energy utilisation) and diabetic therapy
• Diabetic ketoacidosis is a cause of elevated leucocyte count and raised amylase level, which may be confusing in the diagnosis of patients presenting with an acute abdomen. Indeed, ketoacidosis may sometimes present with abdominal pain
• There is a greater risk of hospital-acquired infection, which may be elusive as a cause of deterioration
• Episodes of cardiac ischaemia and infarction may be painless
• There may be reduced renal reserve or more overt evidence of renal impairment

Question 2

1. Preop assesment for diabetic patients undergoing surgery:
2. What blood glucose level is not acceptable and why
3. The general principles of perioperative management are: (insulin dependent diabetes)

Answer 2

1. Serial bloods & HbA1 (4 and 10 mmol/L)

Potential cardiac problems: ECG

potential renal problems: U+Es

2. 13 mmol/L - > ketoacidotic state -> high risk mortality
3. • Establish good diabetic control before operation

• Give insulin as a continuous intravenous infusion during the operative period
• Give an infusion of dextrose throughout the operative period to balance the insulin given and to make up for lack of dietary intake
• Add potassium to the dextrose infusion
• Monitor blood glucose and electrolytes frequently throughout the operative and early postoperative period

Question 3

Detailed explanation of perioperative management of insulin dependent diabetic patients:

Answer 3

Question 4

Perioperative management of diabetic patients using an insulin infusion

Answer 4

Question 5

1. Diabetics controlled on oral hypoglycaemic drugs

2. Diabetics controlled by diet alone

3. Poorly controlled diabetes on emergency admission

Answer 5

1. Many patients are receiving short-acting sulphonylureas such as glipizide. Metformin discontinued -> risk of lactic acidosis. If glycaemic control is difficult then an insulin regimen should be used as above.

On the morning of the operation, the patient is starved in the usual manner and the short-acting sulphonylurea omitted to be reintroduced when oral intake is resumed. Blood glucose should be monitored at least 4-hourly. If glucose rises above 13 mmol/L, it can be controlled by small subcutaneous doses of short-acting insulin, e.g. 6 units of soluble insulin. If a major operation is planned or if postoperative ‘nil by mouth’ is likely to be prolonged, it is best to use insulin and glucose infusions as for insulin-dependent diabetes.

If preoperative control is adequate, these patients require no special perioperative measures; they do not become hypoglycaemic and blood glucose rarely drifts above acceptable levels. Finger-prick blood glucose measurement may be used if there is any doubt.

?infection or vomiting. The diabetes must first be brought under control with rehydration and infusions of insulin, glucose and potassium.

Question 6

What is outpatient surgery?

Answer 6

also known as ambulatory surgery, day surgery, day case surgery, or same-day surgery, is surgery that does not require an overnight hospital stay. The term “outpatient” arises from the fact that surgery patients may enter and leave the facility on the same day. The advantages of outpatient surgery over inpatient surgery include greater convenience and reduced costs

Question 7

Peri-operative use of intravenous insulin:

‘variable rate intravenous insulin infusion’ (VRIII) should replace the ambiguous term ‘sliding scale’.

Patients with a planned short starvation period (no more than one missed meal in total) should be managed by modification of their usual diabetes medication, avoiding a VRIII wherever possible.

Patients expected to miss more than one meal should have a VRIII. However, patients on lifestyle alone or on once daily metformin, should only start a VRIII if their capillary blood glucose levels are greater than 12mmol/L on 2 consecutive occasions.

The recommended first choice substrate solution for a VRIII is 5% dextrose in 0.45% sodium chloride and either 0.15% potassium chloride (KCl) or 0.3% KCl.

Insulin should be prescribed according to National Patient Safety Agency (NPSA) recommendations for safe use of insulin, with the brand name and

Question 8

1. Blood sugar levels in diagnosing diabetes:
2. A fasting plasma glucose test is taken after at least

Answer 8

1. Image
2. eight hours of fasting and is therefore usually taken in the morning

Question 9

1. Normal and diabetic blood sugar ranges
2. Oral Glucose Tolerance Test (OGTT)
3. HbA1c test for diabetes diagnosis

Answer 9

1. Image
2. An oral glucose tolerance test involves taking a first taking a fasting sample of blood and then taking a very sweet drink containing 75g of glucose.

After having this drink you need to stay at rest until a further blood sample is taken after 2 hours.

3. Normal: Below 42 mmol/mol (6.0%)

Prediabetes: 42 to 47 mmol/mol (6.0 to 6.4%)

Diabetes: 48 mmol/mol (6.5% or over)

Question 10

In respect of glycogenolysis and insulin secretion, what is the body’s response to severe trauma such as surgery? Would these responses tend to raise or lower blood glucose?

Question 11

*What are the symptoms and signs of hypoglycaemia?

1. The most common cause of hypoglycaemia is?
2. The major risk factors for developing hypoglycaemia are:

Answer 11

1. • iatrogenic means; accidental overdose of SC insulin or PO hypoglycaemic drugs*

+ (late) gastric dumping syndrome

+ decompensated liver disease

+ adrenal insufficiency

2. Diabetes mellitus

Post-gastrectomy or gastric bypass surgery

Alcohol excess or renal dialysis

Beta blockers

Question 12

Clinical Features of hypoglycaemia

Answer 12

common symptoms: are sweating, tingling lips or extremities, tremor, dizziness, or slurred speech.

Clinical signs: pallor and confusion, tachycardia or tachypnoea, focal neurology, or a reduced Glasgow Coma Score. These features are often non-specific, therefore it is important to routinely check the capillary blood glucose as part of any emergency assessment.

It is important to note that patients taking beta blocker therapy may not exhibit the signs of symptoms of hypoglycaemia, which are predominantly mediated by the sympathetic nervous system. Beta blockers also inhibit hepatic gluconeogenesis and will increase the risk of hypoglycaemia.

Question 13

Investigations for hypoglycaemia

Answer 13

Capillary blood glucose (BM) measurement (Fig. 1). A serum blood glucose can also be measured, but this should not delay any needed urgent management.

If the patient is not known to be on any hypoglycaemic agents, consider investigating for an underlying cause…

Pre-operatively: assessment for comorbidities such as chronic liver disease

Post-operatively: assess the patient nutritional intake (as it is not uncommon for patients to be starved for prolonged periods of time in the peri-operative period).

Question 14

Management of hypoglycaemic patients

Answer 14

A to E approach

Conscious Patient:

• Oral glucose (such as 10g GlucoGel or 120ml Lucozade) immediately
• monitor the capillary blood glucose levels every 1-2hrs until stable
• ensure patient eats complex carbohydrates (e.g. bread) to maintain their BM.
• If no improvement with oral glucose, start IV glucose 1L 10% over 8hrs and monitor BMs.

Unconscious Patient

- protect their airway & start high flow O2.

• Gain IV access & give 100ml of 20% glucose stat. If there is any delay in obtaining IV access, give 1mg IM glucagon immediately. (care with the conc because concentration is irritant especially if extravasation occurs)

Once a suitable consciousness level returns, prescribe 1L 10% glucose over 8hrs and monitor the capillary blood glucose regularly to ensure levels are >5mmol.

Question 15

Intra-Operative Glucose Monitoring

Answer 15

BM measurements should be taken regularly every 30 mins in diabetic patients. Any diabetic patient undergoing major surgery should also be considered for a variable rate insulin infusion for the duration of procedure.

If the blood glucose level is <4mmol at any point, the IV glucose infusion rate should be increased and the insulin infusion stopped. Recheck after 30mins for improvement. Any level <2mmol should be treated as a hypoglycaemic emergency, as discussed above.

Post-operative blood glucose levels should be measured regularly. Variable rate insulin infusion regime should be continued until the patient is eating and drinking normally, before resuming their normal therapy. For type 1 DM patients, continue the IV sliding scale insulin for 30mins after the normal SC insulin injections are given to ensure overlap in insulin therapies.

Question 16

Would these symptoms and signs (in hypoglycaemia) be apparent during general anaesthesia.? Explain your answer.

Question 17

What could be the consequences of hypoglycaemia during anaesthesia?

Question 18

Would the body’s responses to surgery increase or decrease the risk of ketoacidosis in diabetic patients in the intraoperative and postoperative period

Answer 18

increase?

Question 19

What is the target range of intraoperative blood glucose? Below what value does a low intraoperative blood glucose require ‘Rescue Treatment’. Above what level should intraoperative hyperglycaemia be treated (either new treatment or additional treatment)?

Question 20

Patients need to be nil by mouth for 6 hours prior to surgery to reduce the risk of the aspiration of gastric contents at the induction of anaesthesia.

Question 6: Why is there a risk of aspiration of gastric contents at induction of anaesthesia?

Question 7: Why is aspiration of gastric contents into the respiratory tract so dangerous?

Question 21

In general terms in respect of perioperative management diabetes falls into three categories:

1. Diet controlled

If the blood glucose rises above ? then advice should be sought from the diabetes team

2. Oral Hypoglycaemics
The commonest agents are Metformin and Gliclazide. The half-life of Metformin is ? and Gliclazide is ?

3. How many half-lives does it take for a drug to be totally cleared from the blood?

Answer 21

1. 11 mmol/L
2. 6 hrs

10 hrs

3. After one half-life the amount of drug remaining in the body is 50% after two half-lives 25%, etc. After 4 half-lives the amount of drug (6.25%) is considered to be negligible regarding its therapeutic effects. The half-life of a drug depends on its clearance and volume of distribution.

Question 22

How can we identify diabetic patients suitable for day surgery?

Answer 22

Question 23

Guideline for peri-operative monitoring of diabetes and management of hyperglycaemia and hypoglycaemia in patients undergoing surgery with a short starvation period (one missed meal)

1. These guidelines are for the management of well- controlled patients (HbA1c <69mmol/mol, 8.5%) undergoing surgery with a short starvation period.
2. Monitor capillary blood glucose on admission and hourly during the day of surgery. The target blood glucose in the pre-operative, anaesthetised or sedated patient should be 6-10mmol/L (up to 12mmol/L may be acceptable). The target of 6-10mmol/L is for those who are treated with glucose lowering agents – i.e. insulin, (either subcutaneously, or via an insulin infusion) or sulphonylurea therapy. In the awake patient on agents that do not produce hypoglycaemia, provided they have not been given insulin, lower blood glucose values down to 3.5mmol/L are safe and do not require IV glucose or other rescue treatment.
3. At the pre-operative assessment clinic, all patients should have emergency treatment for hypoglycaemia written on their drug chart – i.e. Glucogel®, and 20% dextrose. Rapid acting insulin should also be prescribed

Management of hyperglycaemia

Answer 23

Blood glucose greater than 12mmol/L either pre- or post- surgery

o Check capillary ketone levels using an appropriate bedside monitor if available

o If capillary blood ketones are greater
than 3mmol/L or urinary ketones greater than +++ or greater cancel surgery, follow DKA guidelines and contact the diabetes specialist team or the on call medical team for advice

• Pre-operative hyperglycaemia:

(blood glucose greater than 12mmol/L with blood ketones less than 3mmol/L or urine ketones less than +++)

T1D: SC rapid acting analogue insulin (i.e. Novorapid®, Humalog® or Apidra®). Assume that 1 unit will drop the blood glucose by 3mmol/L. Recheck blood glucose 1 hr later to ensure it is falling. If surgery cannot be delayed commence a VRIII.

T2D: give 0.1 units/kg of SC rapid acting analogue insulin, and recheck blood glucose 1 hour later to ensure it is falling. If surgery cannot be delayed or the response is inadequate, commence a VRIII.

• Post-operative hyperglycaemia:

(blood glucose greater than 12mmol/L with blood ketones less than 3mmol/L or urine ketones less than +++)

T1D: give subcutaneous rapid acting analogue insulin. Assume that 1 unit will drop blood glucose by 3mmol/L BUT wherever possible take advice from the patient about the amount of insulin normally required to correct a high blood glucose. Recheck the blood glucose 1 hour later to ensure it is falling. Repeat the subcutaneous insulin dose after 2 hours if the blood glucose is still above 12mmol/L. In this situation the insulin dose selected should take into account the response to the initial dose – consider increasing the dose if the response is inadequate. Recheck the blood glucose after 1 hour. If it is not falling consider introducing VRIII.

T2D: give 0.1 units/kg of subcutaneous rapid acting analogue insulin, and recheck blood glucose 1 hour later to ensure it is falling. Repeat the subcutaneous insulin after 2 hours if the blood glucose is still above12mmol/L. In this situation the insulin dose selected should take into account the response to the initial dose – consider doubling the dose if the response is inadequate. Repeat the blood glucose after another hour. If it is not falling consider introducing VRIII.

Question 24

Management of hypoglycaemia & hypoglycaemia risk:

Answer 24

Admission or peri-operative hypoglycaemia (capillary blood glucose less than 6mmol/L).

N.B. patients on diet alone are not at risk of hypoglycaemia and are excluded from the guideline below:

o If CBG is 4-6mmol/L and the patient has symptoms of hypoglycaemia: consider giving 50ml of 20% glucose as a stat iv bolus and repeat the CBG after 10 minutes

o If CBG is less than 4mmol/L; give 75- 100ml of 20% glucose (i.e. 300-400 ml/hr using an infusion pump) and repeat the capillary blood glucose after 10 minutes

o Try to avoid stopping the VRIII in type 1 diabetic patients. If it is stopped recommence as soon as the blood glucose rises above 5mmol/L

o Persistent hypoglycaemia should be referred urgently to the diabetic specialist team or the on-call medical team

o Increase frequency of blood glucose monitoring until normoglycaemia achieved and then revert to monitoring blood glucose hourly until the patient is eating and drinking

Question 25

Guideline for the use of a variable rate intravenous insulin infusion (VRIII)

1. The aim of the VRIII is to achieve and maintain glucose levels within the target range of ?, although up to 12mmol/L may be acceptable.
2. This is done by?

Answer 25

1. 6-10mmol/L
2. Infusing a constant rate of glucose-containing fluid as substrate while infusing insulin at a variable rate.

Question 26

The VRIII is the preferred method of controlling the surgical patient’s serum glucose in the following circumstances:

Answer 26

o Patient with T1D undergoing surgery with a starvation period greater than 1 missed meal

o Patient with T1D undergoing surgery who has not received background insulin

o Patient with T2D undergoing surgery with a starvation period > 1 missed meal and develops hyperglycaemia (CBG >12mmol/L)

o Patients with poorly controlled diabetes as defined as an HbA1c >69mmol/mol (>8.5%)

o Most patients with diabetes requiring emergency surgery

Question 27

Guideline for the use of a variable rate intravenous insulin infusion (VRIII)

Indication for VRIII:

+ Patients anticipated to have a long starvation period (i.e. 2 or more missed meals)

+ Decompensated diabetes

Principles

1. If the patient is already on a long acting insulin analogue (e.g. Levemir®, Lantus® or Tresiba®) these should be continued at 80% of the usual dose.
2. Heavier patients often require more insulin per hour.
3. Initial insulin infusion rate should be determined by the bedside capillary blood glucose (CBG) measurement.
4. Hourly bedside CBG measurement should be taken to ensure that the intravenous insulin infusion rate is correct - initially for the first 12 hours or as locally agreed
5. If the blood glucose remains over 12mmol/L for 3 consecutive readings and is not dropping by 3mmol/J/hr or more the result should be rechecked and if the result is confirmed, scale should be changed as shown in the table below
6. If the blood glucose is less than 4.0mmol/L, the insulin infusion rate should be reduced to 0.5 or 0.2 units per hour (depending on which scale is being used), and the low blood glucose should be treated as per the National Guideline for the Management of Hypoglycaemia in Adults with Diabetes irrespective of whether the patient has symptoms. However, if the patient has continued on their long acting background insulin, then their VRII can be switched off, but the regular CBG measurements need to continue

Answer 27

1.

2.

3.

4.

Question 28

Question 9: What is the half-life of intravenous insulin?

Question 29

Indications for a Variable Rate Insulin Infusion (VRII) are:

Patients anticipated to have a long starvation period (i.e. 2 or more missed meals)

Decompensated or poorly controlled diabetes.

Question 9: What is the half-life of intravenous insulin?

Question 10: Use the answer to question 9 to help you explain why the two situations above are best managed with a VRII.

Question 30

Question 11: Why do guidelines for fluid administration alongside a VRII recommend a solution containing glucose and potassium (e.g 5% dextrose with 20 mmol/l of potassium)?

Answer 30

Question 31

Question 12: How many calories (kcal or kJ) does a litre of 5% dextrose contain?

Answer 31

1700 kcal?

1700 x 4.2 = 7140

Question 32

Management of steroids around surgery

1. Patients may be on long-term steroids for a number of reasons such as transplantation or polymyalgia rheumatica (a.What is this?) Exogenous steroids cause hypothalamo-pituitary (HPA) axis suppression.
2. It can be assumed that patients who are more likely to develop HPA axis suppression are:
3. Question 1: Why do exogenous steroids cause HPA suppression?

Question 2: What normally happens to serum ACTH after a major trauma such as surgery?

Question 3: What is the benefit to the patient of your answer to Question 2?

Question 4: Describe Cushingoid features?

Answer 32

1. Pain, stiffness and inflammation in the muscles around the shoulders, neck and hips.

The main symptom is muscle stiffness in the morning > 45 mins. Other symptoms, including:

extreme tiredness, loss of appetite, weight loss, depression

2. Those who receive high doses (>20-30mg prednisolone/ equivalent)

long periods (>3wks)

appear to have Cushingoid features

3. image

Question 33

Question 2: What normally happens to serum ACTH after a major trauma such as surgery?

Question 3: What is the benefit to the patient of your answer to Question 2?

Question 34

Question 4: Describe Cushingoid features?

Explain each symptom

Answer 34

Question 35

Many patients undergoing surgery are nil by mouth and cannot take their oral steroids.

Question 5: What is the Eponym of the crisis that may occur if a patient whose steroids are suddenly stopped undergoes a trauma such as surgery?

Question 6: Describe the clinical and biochemical features of your answer to question 5

Question 36

Question 7: Why is it very difficult to detect such a crisis in the operative and postoperative situation?

Question 37

Given that it is very difficult to detect hypoadrenalism in the operative and postoperative situation, patients on exogenous steroids who cannot continue their oral medication are given intravenous steroids to ‘cover’ the intra and postoperative phases. A common regimen is 25 mg of hydrocortisone IV four times a day.

Question 8: Given that IV hydrocortisone has to be given four times a day, estimate the plasma half- life of hydrocortisone.

Finally, always discuss these patients with the anaesthetist because he/she will need to provide cover at induction and during anaesthesia.