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
How does a spinal anaesthetic cause a headache?
The spinal anaesthetic needle will create a hole that will cause a leak of CSF from the sura that pulls the meninges to cause a headache
Treated with analgesia and sealing the hole with the patients blood
How long should surgery be postponed for after a resp tract infection?
4 weeks
Because the infection will cause hyperactivity in the resp tract and increase the risk of infection post-op
What is the aim for [Hb] in patients with IHD compared to no IHD?
IHD <90 Hb
No IDH <70 Hb
What is the difference between group and screen and crossmatch?
A type and screen is ordered if blood transfusion is likely but not certain
While a crossmatch order indicates to the transfusion service that blood transfusion is required
Why are 2 samples for group and save taken?
To minimise errors
What is a group and screen test?
The type and screen are the primary pre-transfusion tests performed. Testing includes the determination of patient’s ABO group, RhD type, and a screen for the detection of atypical antibodies
Additional testing for red cell antibody identification is performed when atypical antibodies are detected
What is a cross match test?
a way to test your blood against a donor’s blood to make sure they are fully compatible
It’s essentially a trial transfusion done in test tubes to see exactly how your blood will react with potential donor blood
How long before surgery so antiplatelets need to be stoped?
7 days
Eg. clopidogrel, prasugrel and ticagrelor
What is the surgical aim for HbA1c?
<69mmol/mol
What is the starvation period for food/milk?
> 6hrs
What is the starvation period for clear fluid?
> 2hrs
Includes black coffee sometimes
When should steroids be prescribes for anaesthesia?
If the patient has been on 10mg prednisolone or more for 2 weeks+ in the past 3 months
How is obstruction sleep apnoea screened?
Using STOP-BANG
Why is obstructive sleep apnoea screened for before surgery?
Because patients will have intermittent obstruction when asleep after recovery as their tissues relax after surgery
Why does aortic stenosis contraindicates spinal anaesthesia?
Because it causes decreased BP and myocardial perfusion which isn’t tolerated well in these patients
By how much does frailty increase the risk of complications?
x2
What is epiglotitis?
An emergency
May respond to steroids and antibiotics but may also ned intubation to secure the airway
