Why is the management of diabetes especially important in the surgical setting?
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.
What are the manifestations of hypoglycemia
- Dizziness 2. Irritability 3. Sweating 4. Tingling lips 5. Feeling tired 6. Palpitations (fast heartbeat)
Should insulin be stopped before surgery? Why?
Insulin should not be discontinued as the resulting hyperglycaemia can lead to delayed wound healing and infection
What class of drug is Linagliptin?
How do DPP-4 inhibitors work?
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.
Give an example of a prototypical drug of the sodium-glucose cotransporter-2 (SGLT-2) inhibitors class of antidiabetic medication
Empagliflozin, Dapagliflozin, Canaglifozin
Gliclazide is an example of what class of antidiabetic medication?
How does gliclazide work?
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
Should oral antidiabetic medication be stopped prior to surgery?
Yes, insulin-promoting drugs are discontinued the day before surgery
With what dose should patients on chronic oral steroids be given a ‘stress-dose’ corticosteroids IV perioperatively?
If taking steroids > 10 mg/day
Why are ‘stress-dose’ corticosteroids given?
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
What are the effects of long-term, high-dose steroid use?
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
Why should tobacco be discontinued prior to surgery?
Because it can affect wound and bone healing as well as increase the risk of VTE
How does tobacco affect wound and bone healing?
Nicotine has a vasoconstrictive effect
What is sickle cell disease?
An inherited haemoglobinopathy that results in the formation of haemoglobin S (HbS) instead of HbA and causes RBCs to distort into a crescent shape
How is sickle cell disease relevant in surgery?
- 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
Name four or five common triggers of a sickle cell crisis
- 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
What is the blood glucose level threshold for surgery?
Surgery should be avoided if values > 11 mmol/L (65 mg/dL)
What’s the childbearing age?
How long should surgery be postponed following an MI?
Until at least six months
Define the ASA surgical risk classification
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
Signs and symptoms of anaphylaxis
- Hypotension 2. Tachycardia 3. Bronchospasm 4. Angioedema
Why take blood pressure from left arm?
Because the plumbing from the heart (left ventricle) to the left arm is more direct, giving a more representative value
What’s a normal WBC count?
Between 4,000 and 11,000 WBCs per μL of blood
What are the minimum levels of haemoglobin and haematocrit for elective surgery?
Haemoglobin 10 mg/dL and Hct 30 %
Which pathway does PTT check?
Which pathway does PT check?
What does SGLT2 stand for?
Sodium-glucose cotransporter 2 inhibitors
What does GLP-1 stand for?
Glucagon-like peptide 1 receptor agonists
How do SGLT2 inhibitors work?
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)
Sitagliptin and Linagliptin are an example of what class of antidiabetic medication?
What are the pharmacodynamic considerations in elderly patients?
- 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.
What is latex and where does it occur naturally?
Latex is a natural substance which occurs in the sap of the rubber tree (Hevea brasiliensis)
What certain food allergies are related to natural rubber latex allergy?
Banana, avocado, kiwi and chestnut
How does aspirin worsen asthma symptoms?
Because by inhibiting the COX, all arachidonic acid will be converted into leukotrienes
Describe the arachidonic acid pathway
Name three harmful effects of perioperative smoking
- Nicotine results in generalised vasoconstriction and tissue hypoperfusion
- Nicotine potentiates platelet adhesion resulting in microvascular clot formation
- Carbon monoxide binds to haemoglobin, causing oxygen dissociation from haemoglobin and further tissue hypoperfusion