General pre-operative measures Flashcards
What % of the stomach contents enters the duodenum per minute
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
20 minutes
2 hours
how long does it take for the stomach to empty a predominantly CHO meal compared to that of a high fat/protein meal
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.
When can it be safely assumed that the stomach is empty
No food intake < 6 hours AND normal peristalsis occurring
Is milk considered a liquid or a solid with regard to gastric emptying
Solid –> milk congeals in the stomach
Which clears from the stomach faster and why: Breastmilk versus non-human milk
Breast milk (lower fat and protein content)
4 hours breast milk
6 hours non-human milk or formula
Induction technique for a patient with peritonitis?
RSI (Abnormal peristalsis inperitonitis)
Induction technique for patient with bowel obstruction?
RSI (obstructed peristalsis)
Induction technique for trauma patient or patient in shock?
RSI (SNS related delayed gastric emptying)
Which drugs reduce LOS pressure
Anticholinergics
Opioids
Ethanol
Does gastritis increase the risk of regurgitation and aspiration
NO
What is the required fasting period for a light meal
6 hours
What constitutes ‘clear fluids’ 2 hour fasting time
Water Non-particulate juices Isotonic drinks Black tea Black coffee
(includes chewing gum)
How can regular oral medication be administered prior to surgery?
Up to 30 minutes before surgery and with 30 ml of water
What is the mechanism by which prokinetic agents reduce gastric volume and what are two examples of these drugs
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
When should PPIs/H2RA/Antacids/Prokinetics be administered
PPI/H2RA/Prokinetics - 90 minutes prior to surgery
Antacids - immediately before surgery
What is Virchows triad
Virchow (1856) identified three factors contributing to the formation of venous thrombi
- Hypercoaguability
- Vessel wall injury
- Venous Stasis
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
40 - 80 % will get Detectable DVT
10% will die of PE
Above what age is a risk factor for VTE
> 60 years
Above what BMI is considered an independent risk factor for VTE
> 30 kg/m^2
What is the travel duration that constitutes a risk factor for VTE
Continuous travel for > 3 hours within 4 weeks before/after surgery
List the diseases associated with VTE
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
What is the cut off duration of surgery that determines risk of VTE
< 30 mins - lower risk
> 30 min - higher risk
When should OCP be stopped prior to surgery
Four weeks before elective surgery
When are graduated compression anti-embolism stockings indicated and when are they contraindicated
Indicated: all surgical inpatients
Contra-indicated: peripheral vascular disease
What is the mechanism of action of enoxaparin
Acts via antithrombin 3 to inhibit factor Xa
List strategies to prevent VTE
- Risk assessment and stop OCP 4 weeks before elective surgery
- Written and verbal info always
- Graduated compression stockings all patients except PVD patients (intermittent pneumatic compression devices also)
- High risk –>LMWH/Fondaparinux
- 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)
What poses less risk of VTE: GA or RA
Regional Anaesthesia poses less risk (but timing important to avoid hematoma)
When should a vena caval filter be considered?
VTE< 1 month and anticoagulation contraindicated
What effect does metoclopramide have on the LOS ?
Increase LOS tone via a peripheral procholinergic action
Does Calcium Chloride antacid cause diarrhoea?
No it causes constipation
What are two examples of non-particulate antacids and when should these be given?
Non-particulate antacids (sodium citrate, magnesium trisilicate)
1 hour before surgery
Can ranitidine cause confusion
Yes, it can cause reversible confusion
What is the purpose of the preoperative visit
Confirm (or do in emergencies) preoperative assessment
Identify problems have been planned for and managed
To find out if the patients condition has changed
What is required in the time between the pre-admission assessment and the preoperative visit
Reduce patient risk (Fitness, smoking, drug compliance)
Prepare staff and equipment required for surgery
Prepare staff and facilities for postoperative care
What are the 5 most common patient concerns during the preoperative assessment
- MRSA infection
- Dying under anaesthetic
- Being awake and paralyzed
- Intraoperative pain (regional)
- Postoperative pain and PONV
