General pre-operative measures

Question 1

What % of the stomach contents enters the duodenum per minute

Answer 1

2%

Question 2

What is the t1/2 of water and clear fluids in the stomach and how long does it take to completely clear these from the stomach

Answer 2

20 minutes

2 hours

Question 3

how long does it take for the stomach to empty a predominantly CHO meal compared to that of a high fat/protein meal

Answer 3

CHO empty faster than proteins empty faster than fats
(Fats empty the slowest)

Light breakfast with toast: 4 hours clear

High fat/protein meal: takes 6 hours to clear.

Question 4

When can it be safely assumed that the stomach is empty

Answer 4

No food intake < 6 hours AND normal peristalsis occurring

Question 5

Is milk considered a liquid or a solid with regard to gastric emptying

Answer 5

Solid –> milk congeals in the stomach

Question 6

Which clears from the stomach faster and why: Breastmilk versus non-human milk

Answer 6

Breast milk (lower fat and protein content)

4 hours breast milk

6 hours non-human milk or formula

Question 7

Induction technique for a patient with peritonitis?

Answer 7

RSI (Abnormal peristalsis inperitonitis)

Question 8

Induction technique for patient with bowel obstruction?

Answer 8

RSI (obstructed peristalsis)

Question 9

Induction technique for trauma patient or patient in shock?

Answer 9

RSI (SNS related delayed gastric emptying)

Question 10

Which drugs reduce LOS pressure

Answer 10

Anticholinergics
Opioids
Ethanol

Question 11

Does gastritis increase the risk of regurgitation and aspiration

Answer 11

NO

Question 12

What is the required fasting period for a light meal

Answer 12

6 hours

Question 13

What constitutes ‘clear fluids’ 2 hour fasting time

Answer 13

Water
Non-particulate juices
Isotonic drinks
Black tea
Black coffee

(includes chewing gum)

Question 14

How can regular oral medication be administered prior to surgery?

Answer 14

Up to 30 minutes before surgery and with 30 ml of water

Question 15

What is the mechanism by which prokinetic agents reduce gastric volume and what are two examples of these drugs

Answer 15

Metoclopramide
Erythromycin

Procholinergic effects and antidopaminergic (peripherlal D2 receptor) actions

OR

via action on motilin receptors and direct action on smooth muscle to increase tone

Question 16

When should PPIs/H2RA/Antacids/Prokinetics be administered

Answer 16

PPI/H2RA/Prokinetics - 90 minutes prior to surgery

Antacids - immediately before surgery

Question 17

What is Virchows triad

Answer 17

Virchow (1856) identified three factors contributing to the formation of venous thrombi

1. Hypercoaguability
2. Vessel wall injury
3. Venous Stasis

Question 18

What percentage of high risk patients who do not receive prophylaxis develop detectable DVTs and what percent of high risk patients who do not receive prophylaxis die from PE

Answer 18

40 - 80 % will get Detectable DVT

10% will die of PE

Question 19

Above what age is a risk factor for VTE

Answer 19

> 60 years

Question 20

Above what BMI is considered an independent risk factor for VTE

Answer 20

> 30 kg/m^2

Question 21

What is the travel duration that constitutes a risk factor for VTE

Answer 21

Continuous travel for > 3 hours within 4 weeks before/after surgery

Question 22

List the diseases associated with VTE

Answer 22

Any medical illness or infection
Recent CVE/MI
Varicose veins with phlebitis
Trauma (especially lower limb fractures or spinal injury)
Haematological diseases - paraproteinaemia
Nephrotic syndrome
Inflammatory bowel disease

Question 23

What is the cut off duration of surgery that determines risk of VTE

Answer 23

< 30 mins - lower risk

> 30 min - higher risk

Question 24

When should OCP be stopped prior to surgery

Answer 24

Four weeks before elective surgery

Question 25

When are graduated compression anti-embolism stockings indicated and when are they contraindicated

Answer 25

Indicated: all surgical inpatients

Contra-indicated: peripheral vascular disease

Question 26

What is the mechanism of action of enoxaparin

Answer 26

Acts via antithrombin 3 to inhibit factor Xa

Question 27

List strategies to prevent VTE

Answer 27

1. Risk assessment and stop OCP 4 weeks before elective surgery
2. Written and verbal info always
3. Graduated compression stockings all patients except PVD patients (intermittent pneumatic compression devices also)
4. High risk –>LMWH/Fondaparinux
5. Other
   - Avoid dehydration
   Early mobilization
   Regional Anaesthesia (lower risk for VTE vs GA)
   Consider vena caval filters (VTE < 1 month and anticoagulation is C/I)

Question 28

What poses less risk of VTE: GA or RA

Answer 28

Regional Anaesthesia poses less risk (but timing important to avoid hematoma)

Question 29

When should a vena caval filter be considered?

Answer 29

VTE< 1 month and anticoagulation contraindicated

Question 30

What effect does metoclopramide have on the LOS ?

Answer 30

Increase LOS tone via a peripheral procholinergic action

Question 31

Does Calcium Chloride antacid cause diarrhoea?

Answer 31

No it causes constipation

Question 32

What are two examples of non-particulate antacids and when should these be given?

Answer 32

Non-particulate antacids (sodium citrate, magnesium trisilicate)

1 hour before surgery

Question 33

Can ranitidine cause confusion

Answer 33

Yes, it can cause reversible confusion

Question 34

What is the purpose of the preoperative visit

Answer 34

Confirm (or do in emergencies) preoperative assessment
Identify problems have been planned for and managed
To find out if the patients condition has changed

Question 35

What is required in the time between the pre-admission assessment and the preoperative visit

Answer 35

Reduce patient risk (Fitness, smoking, drug compliance)

Prepare staff and equipment required for surgery

Prepare staff and facilities for postoperative care

Question 36

What are the 5 most common patient concerns during the preoperative assessment

Answer 36

1. MRSA infection
2. Dying under anaesthetic
3. Being awake and paralyzed
4. Intraoperative pain (regional)
5. Postoperative pain and PONV