304 Perioperative anaesthesia Flashcards
What are the factors the patient needs to be fit enough for before surgery?
Potential complications and the stress response to surgery
What is the surgical stress response?
Complex neuro-endocrine activation that leads to metabolic, immunological, and haematological activations
It’s relative to the size of the insult so can be minimised by reducing invasiveness
What is the Duke activity status questionnaire (DASI)?
It estimates metabolic equivalents
How many metabolic equivalents is walking up 2 flights of stairs considered to be?
4
What is the ASA score?
American society of Anaesthesiologists
A method of assessing fitness for surgery
1: normal healthy patient
2: Patient with mild systemic disease
3: Patient with severe systemic disease
4: Systemic disease that is a constant risk to life
5: Patient won’t survive without surgery
6: Brain dead patient ready for organ donation
What are some surgical risk prediction models?
P-POSSUM
- Predicts 30-day mortality. It considers patient and surgical factors
NELA
-Predicts 30-day mortality of emergency laparotomy patients
SORT
-Predicts 30-day mortality
ACS NSQIP
-Predicts 30-day mortality, return to theatre, readmission, and discharge for acute care facility. But is time0consuming and expensive
What is the minimum size of an AAA to require surgery?
5.5cm
But also depends on the speed of development
How does cardiopulmonary exercise testing test fitness?
It provides an objective measure of physical fitness to predict perioperative risk
What is CPET?
Cardiopulmonary exercise testing
How does CPET work?
A patient is asked to cycle against resistance while their breath is measured for different gasses
Fitter people can go longer before they start producing lactic acid
What gas is measured in CPET?
VO2 or VCO2
Oxygen consumption or CO2 excretion to calculate the anaerobic threshold
What si meant by failure to rescue?
Dealing with complications early to improve mortality
At what anaerobic threshold is a patient considered high risk?
<11
Shows increased risk of complications
What are the benefits of CPET?
-Identifies pathology
-May encourage patients to exercise because it proves that it is safe
-Helps patients to understand the risk of surgery
-Identifies needs for prehabilitation
What is ‘prehabilitation’?
-Improving physical activity
-Optimising nutrition
-Improving psychological well-being
All to improve the improve the anaerobic threshold and improve outcomes of surgery
What are the disadvantages of ‘prehabilitation’?
-Requires delay to surgery which isn’t always appropriate
-Not all patients will benefit because they are already fit
-It’s resource intensive and not available everywhere
Which pathologies provide a window for prehabilitation?
Fully elective surgery
Patients with cancers and having neo-adjuvant chemotherapy
What is neo-adjuvant chemotherapy?
Chemo before and after resection
It has better outcomes
How does the dose of morphine differ between oral and subcutaneous administration?
Morphine has a lower bioavailability orally than subcut, so give half dose subcut
Morphine bioavailability orally: 30-50%
How much is given for a breakthrough dose for opioids?
1/6th of the normal dose
What is a breakthrough dose?
The dose given to a patient with chronic pain when when their pain had a sudden exacerbation but they’re already on analgesia
How does a decreased ability to take deep breaths increase risk of complications?
It prevents the constant flow of air throughout the lung and makes pneumonia and lung collapse a greater risk
Can be minimised with analgesia to allow the patient to breath because they wont feel the postoperative pain
What is the massive haemorrhage?
Loss of more than one blood volume within 24 hours (around 70 mL/kg, >5 litres in a 70 kg adult) 50% of total blood volume lost in less than 3 hours. Bleeding in excess of 150 mL/minute
What is the purpose of cricoid pressure during anaesthetic induction?
To prevent the passage of gastric contents in the airway
