Preoperative Assessment

Question 1

Why is the management of diabetes especially important in the surgical setting?

Answer 1

Besides uncontrolled diabetes, surgical procedures can also alter normal glucose homeostasis and result in hyperglycaemia, which is a risk factor for postoperative infection and impaired wound healing.

Question 2

What are the manifestations of hypoglycemia

Answer 2

1. Dizziness 2. Irritability 3. Sweating 4. Tingling lips 5. Feeling tired 6. Palpitations (fast heartbeat)

Question 3

Should insulin be stopped before surgery? Why?

Answer 3

Insulin should not be discontinued as the resulting hyperglycaemia can lead to delayed wound healing and infection

Question 4

What class of drug is Linagliptin?

Answer 4

DPP-4 inhibitor

Question 5

How do DPP-4 inhibitors work?

Answer 5

Physiologic DPP-4 (dipeptidyl peptidase-4) enzymes inactivate incretin hormone and glucagon-like peptide (GLP-1) that are naturally released in the intestines during mealtimes and cause an increase in insulin secretion by stimulating beta cells and a decrease in glucagon secretion by inhibiting alpha cells. Thus, DPP-4 inhibitors prolong the natural hypoglycaemic effect of incretin hormones.

Question 6

Give an example of a prototypical drug of the sodium-glucose cotransporter-2 (SGLT-2) inhibitors class of antidiabetic medication

Answer 6

Empagliflozin, Dapagliflozin, Canaglifozin

Question 7

Gliclazide is an example of what class of antidiabetic medication?

Answer 7

Sulfonylureas

Question 8

How does gliclazide work?

Answer 8

Binds to the beta-cell sulfonyl urea receptor and subsequently blocks ATP-sensitive potassium channels, which causes an influx of calcium in the pancreatic beta cells, resulting in an increase in insulin release

Question 9

Should oral antidiabetic medication be stopped prior to surgery?

Answer 9

Yes, insulin-promoting drugs are discontinued the day before surgery

Question 10

With what dose should patients on chronic oral steroids be given a ‘stress-dose’ corticosteroids IV perioperatively?

Answer 10

If taking steroids > 10 mg/day

Question 11

Why are ‘stress-dose’ corticosteroids given?

Answer 11

To avoid an adrenal crisis. Because surgical stress causes an increase in cortisol production, patients receiving regular exogenous corticosteroids will have a dampened ability to produce endogenous physiological glucocorticoid and won’t be able to produce enough cortisol to mount a response in such cases, resulting in an adrenal crisis with consequences such as lethargy and feeling weak

Question 12

What are the effects of long-term, high-dose steroid use?

Answer 12

Adrenal function suppression: 1. Increased risk of poor or delayed wound healing due to a decreased inflammatory process 2. Increased risk of infection due to decreased inflammatory response. N.B. Low WBC may mask infection

Question 13

Why should tobacco be discontinued prior to surgery?

Answer 13

Because it can affect wound and bone healing as well as increase the risk of VTE

Question 14

How does tobacco affect wound and bone healing?

Answer 14

Nicotine has a vasoconstrictive effect

Question 15

What is sickle cell disease?

Answer 15

An inherited haemoglobinopathy that results in the formation of haemoglobin S (HbS) instead of HbA and causes RBCs to distort into a crescent shape

Question 16

How is sickle cell disease relevant in surgery?

Answer 16

1. Small changes in oxygen tension cause HbS to form crystalline structures that distort red blood cells into a sickle shape that’s unable to deform in shape to fit small capillaries, obstructing microvascular flow and leading to ischaemia. 2. Patients are prone to hypoxia due to the decreased oxygen-carrying capacity of HbS and of the blood due to secondary anaemia as a result of the spleen destroying the abnormal RBCs

Question 17

Name four or five common triggers of a sickle cell crisis

Answer 17

1. Emotional stress and anxiety 2. Infection 3. Dehydration - blood becomes thicker and sickle-shaped RBCs are more likely to stick together and cause vaso-occlusion 4. Hypoxia 5. Vascular stasis

Question 18

What is the blood glucose level threshold for surgery?

Answer 18

Surgery should be avoided if values > 11 mmol/L (65 mg/dL)

Question 19

What’s the childbearing age?

Answer 19

12-45

Question 20

How long should surgery be postponed following an MI?

Answer 20

Until at least six months

Question 21

Define the ASA surgical risk classification

Answer 21

Class I - healthy patient Class II - mild systemic disease (obese, DM, HTN) Class III - severe systemic disease that limits activity (angina, COPD, cerebral palsy in wheelchair) Class IV - incapacitating systemic disease that is a constant threat to life Class V - not expected to survive past 24 hours Class VI - declared legally brain dead

Question 22

Signs and symptoms of anaphylaxis

Answer 22

1. Hypotension 2. Tachycardia 3. Bronchospasm 4. Angioedema

Question 23

Why take blood pressure from left arm?

Answer 23

Because the plumbing from the heart (left ventricle) to the left arm is more direct, giving a more representative value

Question 24

What’s a normal WBC count?

Answer 24

Between 4,000 and 11,000 WBCs per μL of blood

Question 25

What are the minimum levels of haemoglobin and haematocrit for elective surgery?

Answer 25

Haemoglobin 10 mg/dL and Hct 30 %

Question 26

Which pathway does PTT check?

Answer 26

Intrinsic

Question 27

Which pathway does PT check?

Answer 27

Extrinsic

Question 28

What does SGLT2 stand for?

Answer 28

Sodium-glucose cotransporter 2 inhibitors

Question 29

What does GLP-1 stand for?

Answer 29

Glucagon-like peptide 1 receptor agonists

Question 30

How do SGLT2 inhibitors work?

Answer 30

Sodium-glucose cotransporter-2 mediates the reabsorption of 80-90 % of filtered glucose in the kidney. Thus SGLT2 inhibitors induce glycosuria (i.e. increase urinary glucose excretion)

Question 31

Sitagliptin and Linagliptin are an example of what class of antidiabetic medication?

Answer 31

DPP-4 inhibitors

Question 32

What are the pharmacodynamic considerations in elderly patients?

Answer 32

1. Declining liver and renal function lessen the rate of elimination 2. Elderly patients have a relatively low water content, leading to increased drug concentrations compared with younger patients 3. Potency of drugs is increased because elderly less well-nourished patients have lower levels of circulating plasma protein, which normally binds drugs and makes them ineffectual 4. Elderly patients are often on polypharmacy and the chance of adverse drug interactions is raised.

Question 33

What is latex and where does it occur naturally?

Answer 33

Latex is a natural substance which occurs in the sap of the rubber tree (Hevea brasiliensis)

Question 34

What certain food allergies are related to natural rubber latex allergy?

Answer 34

Banana, avocado, kiwi and chestnut

Question 35

How does aspirin worsen asthma symptoms?

Answer 35

Because by inhibiting the COX, all arachidonic acid will be converted into leukotrienes

Question 36

Describe the arachidonic acid pathway

Answer 36

Question 37

Name three harmful effects of perioperative smoking

Answer 37

1. Nicotine results in generalised vasoconstriction and tissue hypoperfusion
2. Nicotine potentiates platelet adhesion resulting in microvascular clot formation
3. Carbon monoxide binds to haemoglobin, causing oxygen dissociation from haemoglobin and further tissue hypoperfusion