ILA 4: Diabetes perioperative management

Question 1

Scenario 1: Elective Surgery in a patient with type 2 diabetes.
Mr Woods is a 69 year old patient who has been listed for a total knee replacement. He is overweight and has osteoarthritis and type 2 diabetes. He takes gliclazide
160mg bd.
a) With regards his diabetes, what history, examination and investigations would you want to obtain before giving him an anaesthetic?
b) How do sulfonlyureas work?

Answer 1

• History: current symptoms, disease control, microvascular complications (eyes, nerves, kidneys), macrovascular (CHD, stroke/TIA, PVD)
• Exam:
• HbA1c : <75 is usually okay for elective surgery
• Other bloods: glucose, UEs/creatinine
• Urinalysis
• ECG

b) Increase endogenous insulin release

Question 2

Fasting in DM:

a) What are the starvation rules for theatre?
b) What will happen if this patient continues to take his oral diabetic medication whilst he his fasting?
c) What advice should he be given regarding on taking medication the day before surgery?
d) Does he need a sliding scale or can be managed using the FAST/CHECK regime?
e) Where should he be placed on the list?
f) When should he restart taking his tablets after his operation?

Answer 2

a) 6 hours for solid food, 4 for cloudy fluids, 2 hours for clear fluids
b) Hypoglycaemia
c) Omit medications
d) Fast/check? (moderate surgery in T2DM)
e) Early (to limit fasting/medication omission period)
f) Straight away

Question 3

Problems with surgery in DM

Answer 3

HYPO:
- Patients are usually fasted (of major significance in T1DM, less so in T2DM): they need basal insulin and without additional carbohydrate will develop hypoglycaemia
- Unconscious patients can’t complain of symptoms of a hypo and can die of severe hypo.
HYPER:
- Trauma of major surgery may provoke the release of stress hormones (e.g. adrenaline and cortisol), which increases insulin requirements
- Poor and erratic absorption of SC insulin if peripheral vessels are shut down

Question 4

Surgical management of DM

a) Monitoring
b) Omission of anti-diabetic meds and fast/check monitoring - who is this appropriate in?
c) Separate glucose/insulin infusions (“sliding scale”/ variable intravenous insulin infusion) - who is this appropriate in?

Answer 4

a) Capillary glucose is measured regularly and accurately, recorded and acted upon
b) Short procedures in all patients, minor surgery (e.g. arthroscopy, D and C), ?moderate surgery in T2DM, patients should be early on operative list!
c) All emergency surgery, moderate or major surgery in Type 1 diabetes, major surgery in Type 2 diabetes

Question 5

Omission of anti-diabetic meds and fast/check monitoring: process

Answer 5

• patient is placed early on operating list.
• usual insulin injection or tablets omitted
• measure capillary glucose hourly using meter.
• give single dose of SC soluble insulin (Actrapid), 6U, if blood glucose rises >17 mmol/l
• if blood glucose continues to rise consider IV regimen, then restart normal regimen when eating and drinking normally

Question 6

Separate glucose/insulin infusions (“sliding scale”)

Answer 6

• place patient at end of list or in the afternoonto give time to reach target glucose (7–11 mmol/l)
• glucose infusion: 500 ml 10% dextrose + 20 mmol KCl
  give at a rate of 50 ml/h using pump
• insulin infusion: soluble insulin 50 units, in 0.9% saline, 50 ml, delivered by syringe driver (?IV)
• capillary blood measured hourly and insulin pump adjusted to maintain glucose as above

Question 7

Hypogylcaemia.

a) Blood glucose below…?
b) Causes
c) Clinical fx
d) Whipple’s triad for diagnosis
e) Management

Answer 7

a) 3.0 mmol/L
b) Diabetic meds (insulin, sulfonylureas), alcohol/illness, inadequate intake, excess exercise, insulinoma, hypoadrenalism, factitious
c) Sweating, tremor, palpitations, poor coordination, paraesthesiae, abnormal behaviour (aggression, fugue states), coma, seizures (focal or generalised), hemiplegia can occur with a normal conscious level
d) 1. Plasma hypoglycaemia. 2. Symptoms attributable to a low blood sugar level. 3. Resolution of symptoms with correction of the hypoglycaemia
e) Glucogel/glucose tablets/drink, then IV glucose (75-80 ml 20% glucose or 150-160 ml of 10% glucose) or IM glucagon if no IV access

Question 8

Scenario 2: Elective surgery in a patient with T1DM.
Mrs Hepplethwaite is a 45 year old patient with type 1 diabetes. She is due to have a TAHBSO (due to last 1.5hours). She takes novorapid (rapid-acting) with meals (dose according to her carbohydrate load) and levemir (intermediate-acting)
15units bd. You are visiting her on the ward the evening before her operation.

a) What happens if a patient with type 1 diabetes omits their insulin?
b) What happens if a patient with type 1 diabetes continues to take their insulin whilst they are fasting?

Answer 8

a) Hyperglycaemia - risk of DKA

b) Hypoglycaemia

Question 9

Mrs Hepplethwaite is 1st on the list for her operation tomorrow. You need to start her on a sliding scale. The components of a sliding scale are intravenous insulin and intravenous fluids.

a) What concentration of insulin do you prescribe?
b) What fluids do you run through in a separate IV infusion?

Answer 9

a) 50 units, in 0.9% saline, 50 ml (1 unit per ml)

b) 500 ml 10% dextrose + 20 mmol KCl give at a rate of 50 ml/h using pump (if serum K+ < 5)

Question 10

You are bleeped to the ward to assess Mrs Hepplethwaite on the morning of surgery as she has become unresponsive. You assess her using an ABCDE approach and this is what you find:
A-clear, no noisy breathing
B- chest clear, sats 94% on air
C- HR 100, BP 140/90, CRT <2secs, sweaty. She has IV access.
D- GCS 9/15 (E2, V3, M4), Pupils reactive, glucose 1.8mmol/l

a) What do you do?
b) What would you do if she didn’t have IV access?

Answer 10

a) IV glucose bolus: 75-100ml (20% dex) or 150-200ml (10% dex) - observe response over 5 mins and repeat as necessary
b) Cooperative: glucose tablet, glucose drinks.
Poor cooperation: glucogels.
Unconscious: IM glucagon (not if fasting?)

Question 11

Scenario 3: Emergency surgery in a patient with T2DM.
Mr Bernstein is a 68year old man who has type 2 diabetes for which he takes gliclazide 160mg bd.
He has been admitted to SAC via ED. He is vomiting,
has acute abdominal pain and abdominal distension and is made NBM with an NG tube.
His investigations reveal he has large bowel obstruction and he is due to have a laparotomy in the next 6 hours. His blood glucose has been 18mmol/L for the last 2h.

a) How does emergency surgery differ from elective surgery when managing patients with diabetes?
b) Why might blood sugar be elevated in an unwell surgical patient?
c) What problems may hyperglycaemia cause in a surgical patient?

Answer 11

a) All go on sliding scales
b) Cortisol stress response
c) Increased infection rates, poor wound healing, increased hospital stay and other complications, Increased urine output so dehydration and fluid balance derangement, risk of DKA

Question 12

You follow the STH diabetes protocol and check a lab blood glucose, U+Es and a plasma bicarbonate which comes back at 20mmol/L.
You decide to start a sliding scale for the patient whilst he his waiting to go theatre.
a) What rate do you start the insulin at?
b) What intravenous fluids do you start and what do you run them at?

Answer 12

a) 4 units/hour (as per the STH sliding scale)

b) NaCl (0.9%)

Question 13

Scenario 4: An acutely unwell patient with T1DM.
You are the F1 working in ED and a 24 year old patient with type 1 diabetes presents with a 48h history of vomiting and abdominal pain. She is known to
have poor control of her diabetes. She has a blood glucose of 19mmol/l. You are worried she has DKA.

a) What fluid will you prescribe to resuscitate her with? How soon should this be started? How much will you give her?
b) She tells you she weighs 8 stone (50kg). What rate will you start the insulin infusion at?
c) How often will you measure her blood glucose and ketones?
d) What is the danger of giving too much fluid?
e) What electrolyte abnormality must you be careful to avoid?

Answer 13

a) NaCl 0.9%, 500ml over 10-15 mins (not Hartmann’s as the lactate will be converted to glucose), then re-assess and prescribe more as necessary up to 2L
b) 0.1 units/kg/hr - for her, 0.1/50/hr = 5 units per hour
c) Hourly
d) Fluid overload and cerebral oedema
e) Hypokalaemia, also hypernatraemia/ hyperchloraemic metabolic acidosis

Question 14

DKA: diagnostic criteria

think: Diabetic, Keto, Acidosis

Answer 14

Diabetic: glucose >11 or known DM
Keto: blood ketones > 3mmol/L (ketonaemia) or urinary ketones +2 or more on urine dip (ketonuria)
Acidosis: Bicarbonate < 15mmol/L or venous pH < 7.3

Caveats:

• hyperglycaemia may not always be present
• low blood ketone levels (<3 mmol/L) do not always exclude DKA

Question 15

DKA: causes (5 Is)

Answer 15

Insulin
Infection
Intoxication
Injury
Infarction

Question 16

DKA: clinical features

a) Symptoms
b) Signs

Answer 16

a) Polyuria and polydipsia, vomiting, abdominal pain, weight loss, weakness and lethargy
b) DEHYDRATION (dry mucous membranes, decreased skin turgor/skin wrinkling, sunken eyes, slow capillary refill, tachycardia with weak pulse, hypotension, confusion/coma if severe).
Kussmaul respiration (deep hyperventilation) and acetone smell (like pear drops) on the breath

Question 17

DKA: investigations

a) Key initial investigations
b) What would be typically seen on:
- electrolytes (Na+, K+)
- urea and creatinine
- ABG
c) Other bloods to do (for possible causes/ DDx)

Answer 17

a) A-E assessment, BM, Bloods for glucose and ketones, VBG, urine dip, ECG
b) Ix:
- Electrolytes - Na+ and K+ may be high normal or low. Note: there is generally cellular K+ depletion even if blood levels are high.
- Urea and creatinine - elevated due to prerenal acute kidney injury
- Arterial blood gases - metabolic acidosis with low pH and low HCO3; pCO2 should be normal but can be depressed by respiratory compensation; low pO2 may indicate a primary respiratory problem as a precipitant.

c) Cardiac enzymes - if myocardial ischaemia/infarction is suspected - eg, troponin.
Creatine kinase - rhabdomyolysis may also exist (also increased in myocardial infarction).
Amylase - if pancreatitis is suspected.
Blood cultures (septic screen)

Question 18

DKA: investigations

a) Key initial investigations
b) What would be typically seen on:
- electrolytes (Na+, K+)
- urea and creatinine
- ABG
c) Other bloods to do (for possible causes/ DDx)
d) Other useful investigations ,etc.

Answer 18

a) A-E assessment, BM, Bloods for glucose and ketones, VBG, urine dip, ECG
b) Ix:
- Electrolytes - Na+ and K+ may be high normal or low. Note: there is generally cellular Na+/K+ depletion even if blood levels are high.
- Urea and creatinine - elevated due to prerenal acute kidney injury
- Arterial blood gases - metabolic acidosis with low pH and low HCO3; pCO2 should be normal but can be depressed by respiratory compensation; low pO2 may indicate a primary respiratory problem as a precipitant.

c) Cardiac enzymes - if myocardial ischaemia/infarction is suspected - eg, troponin.
Creatine kinase - rhabdomyolysis may also exist (also increased in myocardial infarction).
Amylase - if pancreatitis is suspected.
Blood cultures (septic screen)

d) CXR, CT head, etc.

Question 19

DKA: osmolality and anion gap.

a) Equation for osmolality. What happens in DKA?
b) If osmolality very high and no significant ketonaemia, possible diagnosis?
c) Anion gap equation. What happens in DKA?

Answer 19

a) 2Na + K + urea + glucose (normal ~ 285). In DKA, usually > 290 mOsm/kg
b) HONK/HHS: usually osmolality > 320
c) [Na+] - ([Cl-] + [HCO3-]). Usually > 13mmol/L

Question 20

DKA: signs of severe cases

a) Metabolic tests
b) Bedside tests

Answer 20

a) Blood ketones > 6 mmol/L.
Bicarbonate < 5 mmol/L.
Venous/arterial pH < 7.0.
Hypokalaemia on admission (under 3.5 mmol/L).
Anion gap > 16

b) GCS < 12.
Oxygen saturation < 92% on air (assuming normal baseline respiratory function).
Systolic BP < 90 mm Hg.
Pulse rate over 100 or below 60.

Question 21

DKA: initial management

Answer 21

• A-E and immediate resuscitation as required.
• HDU / ITU management
• Monitor SpO2, continuous ECG monitor, BP and HR.
• Obtain large-bore peripheral IV access or insert central venous catheter.
• Urinary catheterisation is usually carried out to monitor urine output and will also allow urinalysis.
• Consider VTE
• In unconscious, drowsy or vomiting patients, consider passing a nasogastric tube.

Question 22

DKA: management

a) definitive treatment
b) monitoring
c) aims of treatment

Answer 22

a) Appropriate fluid replacement, followed by insulin administration.
- IV crystalloid (e.g. 500ml NaCl 0.9%, over 10-15 mins. Repeat and seek help if SBP < 90)
- IV insulin infusion (0.1 units/kg/hr)
- Add KCl unless anuria suspected
- When glucose is < 14 mmol/L, add 10% dextrose infusion to prevent over-rapid correction of hyperglycaemia

b) Monitor blood ketones/glucose/pH and electrolytes hourly, and adjust insulin/dex and KCl accordingly

c) Restore circulating plasma volume, reduce ketones by 0.5 mmol/L/hr, increase HCO3- by 3.0 mmol/L/hr, reduce BM by 3.0 mmol/L/hour and maintain K+ between 4.0 and 5.5 mmol/L.
If these rates are not achieved then the insulin infusion rate should be increased.