Common conditions and anaesthesia

Question 1

What are 5 types of cardiovascular issues that may be present in a patient undergoing surgery, that the anaesthetist should think about?

Answer 1

1. Ischaemic: angina, MI
2. Valve: stenosis, incompetent, mixed
3. Rhythm: AF, block
4. Muscle: cardiomyopathy
5. Congenital

Question 2

What are 3 important points for anaesthetists to remember about patients diagnosed with AF?

Answer 2

1. Often on warfarin - impact on surgery (discontinue 5 days before, bridging with heparin)
2. Rate control - if poorly controlled will have some short beats in which heart doesn’t fill adequately
3. 15% reduction in cardiac output

Question 3

What must be done with patients taking warfarin prior to surgery?

Answer 3

Stop 5 days before, may need bridging therapy with heparin (unfractionated heparin or low molecular weight heparin)

Question 4

What is the goal INR for major and minor surgeries?

Answer 4

• <1.5 major surgery
• <2 minor surgery

Question 5

What are 2 key things to consider prior to surgery in a patient with cardiac valve disease?

Answer 5

1. May be associated with infections such as SBE (subacute bacterial endocarditis), may require prophylactic antibiotics
2. Warfarin - if valve replaced, if replaced with mechanical valve

Question 6

What type of congenital cardiac disese may required prophylactic antibiotics?

Answer 6

ASD, VSD (aortic and ventricul septal defects) (also congenital valve problems)

Question 7

What is important to remember about pacemakers and surgery, and how can this be fixed?

Answer 7

• Diathermy can sometimes inhibit pacemaker, may see complete block on ECG whilst being used
• Can fix it with a magnet or cardiac technicians; can help by moving diathermy away from pacemaker
• use of bipolar diathermy less asocciated with pacemaker interference

Question 8

Why is the degree of reversibility of reduced FEV1 in COPD important to know for surgery?

Answer 8

In case someone becomes wheezy on the table

Question 9

Why is the presence of emphysema relevant to surgery?

Answer 9

Impacts on inahlation of anaesthesia

Question 10

What type of infusions are commonly used in surgery for patients with diabetes?

Answer 10

Glucose-insulin-potassium infusions

Question 11

What is the most challenging type of procedure for diabetic patients and why?

Answer 11

Minor surgery: hard to decide whether to start insulin infusions, how much oral hypoglycaemics to give etc.

Question 12

When does renal disease make surgery/ anaesthesia more difficult?

Answer 12

If acute - coming up for transplant or recently dialysed

Question 13

Why is most renal disease coped with well these days in surgery/ anaesthesia?

Answer 13

Modern anaesthetic agents exhaled or excreted through liver, so can cope with renal disease well

Question 14

What are 2 issues with liver disease that may arise in surgery/anaesthesia?

Answer 14

1. Reduced drug clearance in severe liver disease; increased sensitivity to some drugs e.g. warfarin (not anaesthetics)
2. Abnormal clotting - may need to consider earlier use of FFP or vitamin K

Question 15

What are the key goals in a diabetic patient during surgery?

Answer 15

• Prevention of hypoglycaemia and ketoacidosis during surgery and anaesthesia is paramount
• Maintenance of blood sugar levels and recovery from metabolic stress of surgery is now thought to be much more important than it used to be

Question 16

When should glycaemic control be optimised for elective surgery?

Answer 16

Ideally prior to the surgery; major surgery should be delayed if HbA1c is >75mmol/mol until control improved

Question 17

When should diabetic patients be placed on the theatre list?

Answer 17

Ideally first - should undergo surgery in the morning rather than waiting until afternoon

Question 18

For diabetic inpatients undergoing surgery, what is the rule for oral hypoglycaemics?

Answer 18

None given on the morning of the operation

Question 19

When is a key point to measure blood sugar levels for surgery?

Answer 19

Before induction of anaesthesia - should be measured and known

Question 20

What determines a ‘minor’ operation?

Answer 20

Patient will be able to eat and drink in <4 hours

Question 21

What are the 4 key points for minor surgery for Type 2 diabetes?

Answer 21

1. Omit metformin 48 hours pre-op
2. Omit other oral hypoglycaemics on day of surgery
3. if BG < 12 mmol/L, continue, no insulin
4. BG > 12 mmol/L - if surgery must continue, move into major surgery regimen

Question 22

How often should blood glucose be checked during minor surgery with Type 2 diabetics?

Answer 22

at least once during surgery, or hourly

Question 23

How often should blood glucose be checked for type 2 diabetics following minor surgery?

Answer 23

Check hourly until eating, then 4 hourly

Question 24

When should oral hypoglycaemics (+ metformin) be restarted for type 2 diabetics following minor surgery? What changes may need to be made to medications post-operatively?

Answer 24

• non-metformin: when eating.
• may need to increase dose, with or without insulin, for a while
• delay metformin until day 4, watch renal function

Question 25

For each of the 3 key times of insulin regime, what pre-op changes are made for type I diabetics for minor and surgery?

Answer 25

1. if on teatime/ bedtime Lantus/Glargine or Levemir/Determir, reduce dose by 50% on the day prior to surgery
2. If on basal bolus regimen with bedtime isophane (Humulin I, Insulatard), reduce isophane by 20%
3. If on b.d. mixed insulin (e.g. Mixtard 30, Novomix 30, Humalog Mix50, Humalog Mix25), reduce teatime dose by 20%

Question 26

When blood glucose is checked for type I diabetics for minor surgery, what are the 2 rules that are followed based on the result?

Answer 26

1. If 4-12mmol/L, process
2. If >12 mmol/L commence infusion as for major surgery

Question 27

How frequently should blood glucose be monitored for type I diabetics for minor surgery?

Answer 27

monitor hourly

Question 28

When should insulin be resumed for type 2 diabetics following minor surgery? What are 4 rules for what should be done based on the type of insulin?

Answer 28

• Give subcut insulin with post-op lunch

1. if b.d. mixture e.g. Mixtard 30, give 50% of usual breakfast dose 30 minutes prior to lung
2. if b.d. analogue mixture e.g. Novomix or Humalog, give 50% of usual breakfast dose with lunch
3. If on Novorapid/Humalog, give usual dose with lunch
4. If on Actrapid prior to meals, give usual dose 30 mins before meal

Question 29

For type I diabetic patients who undergo minor surgery later in the day, what are 4 rules re. insulin and glucose?

Answer 29

1. Give 50% of usual insulin with light breakfast
2. Check blood glucose pre-op and proceed as above (4-12 proceed, >12 commence infusion as for major surgery)
3. Monitor blood glucose hourly
4. Restart usual inulin with evening meal if eating

Question 30

What changes should be made to anti-diabetic drugs in type 2 diabetics undergoing major surgery?

Answer 30

Omit oral hypoglycaemics on the day of surgery

Question 31

Why should metformin sometimes be stopped prior to surgery in type 2 diabetics? What are the situations when it should be stopped?

Answer 31

• Metformin is renally excreted; renal impairment may lead to accumulation and lactic acidosis during surgery
• If the patient will miss more than one meal or there is significant risk of the patient developing acute kidney injury (e.g. eGFR <60), stop metformin when fast begins

Question 32

When is glucose infusion required during major surgery for type 2 diabetics?

Answer 32

Not unless blood glucose is less than 4mmol/L

Question 33

How often should blood glucose levels be recorded pre- and post-operatively?

Answer 33

1-2 hour (2 hourly if extremely stable post-operatively)

Question 34

What 2 things should be started in the recovery room for type 2 diabetics following major surgery?

Answer 34

1. Dextrose and insulin: 10% dextrose run at 60ml/ hour, Actrapid 50 units in 50ml normal saline infusion pump, titrated against blood sugar
2. Also normal saline with KCl run at 60ml/ hour to prevent hyponatraemia

Question 35

Why are type 2 diabetics given normal saline with KCl following major surgery?

Answer 35

to prevent hyponatraemia

Question 36

Which type of type 2 diabetics may require more insulin following major surgery?

Answer 36

Obese patients and those on steroids

Question 37

What blood glucose should be aimed for post-operatively in type 2 diabetics following major surgery?

Answer 37

4-12mmol/L

Question 38

What should be done if post-operative blood glucose falls below 4 in a type 2 diabetic following major surgery?

Answer 38

run in 50mls of 10% glucose and recheck blood glucose prior to restarting insulin

Question 39

When should oral hypoglycaemics be resumed for type 2 diabetics following major surgery? What changes may be made?

Answer 39

when eating; dose may need to be increased and/or insulin may be required for a short period

Question 40

For type I diabetics undergoing minor surgery, what changes should be made to insulin on the day of surgery?

Answer 40

Omit morning insulin on the day

Question 41

What 2 things should be done re insulin and blood glucose on the day of major surgery for type 1 diabetics?

Answer 41

1. Omit morning insulin
2. Check bedside blood glucose and comence dextrose and insulin infusion
   3.

Question 42

How often should blood glucose be monitored for type I diabetics undergoing major surgery?

Answer 42

Monitor blood glucose 2 hourly when completely stable

Question 43

When should usual insulin be restarted in a type I diabetic following major surgery?

Answer 43

when eating again

Question 44

If, depsite trying to avoid it, a major surgery for a type I diabetic does occur later in the day, what 4 things should be done?

Answer 44

1. Give 50% of usual insulin with light breakfast if allowed
2. If fasting, omit morning insulin and ocmmence infusion (this step is missing from minor surgeries for type I)
3. Monitor blood glucose hourly then 2 hourly post op when stable (vs 1 hourly for minor surgeries)
4. Restart usual insulin when eating

Question 45

Why is tight glycaemic control (e.g. 4-6 ot 4-8) popular in diabetics in surgery?

Answer 45

Hypoglycaemia is extremely dangerous - can kill or cause permanent brain damage, so complete lack of control is very bad. Good to err on side of tight control, but don’t cause hypos (can be masked by GA)

Question 46

What type of way of using insulin is given in surgery?

Answer 46

Insulin sliding scale