Anaesthetics Flashcards
What is a day surgery case?
planned admission where someone undergoes theatre and goes home the same day
What is a day of surgery admission (DOSA)?
when a patient attends hospital to be admitted on the day of their surgery rather than staying the night before
What are the advantages of DOSA?
better sleep less anxious reduced infection risk reduced falls and delirium risk in elderly more cost effective
What are the disadvantages of DOSA?
shorter time for consent
patient may be late
incorrect fasting
incorrect medication taken the day of
How long must a patient fast
a) food?
b) milk?
c) clear liquid?
a) 6 hours
b) 4 hours
c) 2 hours
When are patients ideally seen at the pre admission clinic?
6-8 weeks
What is the purpose of the PAC?
patient told about side effects of anaethesia and fasting requirements
determine if any other important issues ie
airway difficulties, drug reactions, post-operative nausea risk
what should be screened for patients ASA grade 3 or patients having major surgery?
anaemia screen
Haemostasis (coagulation and LFTs)
Kidney function (or if at risk of AKI
ECG
What puts patients at risk for an AKI?
intraperitoneal surgery CKD (eGFR<60) Diabetes Heart failure Age 65 or over Liver disease Nephrotoxic drugs (ACEi, NSAIDs)
Which factors need to be considered before discharge?
pain controlled no N+V no complications accceptable SEWS passed urine someone at home for 24hrs
Which drugs should be omitted day of surgery?
ACE inhibitors Angiotensin 2 antagonists (ARBs) Diuretics unless for heart failure Aspirin, clopidogrel, dipyridamole, warfarin. Lithium NSAIDs non-essential eg. vitamins, HRT, laxatives.. oral contraceptives
How does reflux affect anaesthetics?
may decide to intubate
What are the characteristics of acute pain?
sudden onset
known cause
controlled by normal analgesics
What are the 3 pillars of general anaesthesia?
- not being aware
- analgesia
- paralysis
What proportion of patients who present to a surgeon are surgically managed?
1 in 3
What proportion of patients go home on the day of their surgery?
70%
If a patient stops breathing, what keeps them alive?
functional residual capacity of the lungs
How can functional residual capacity be increased? what does this achieve?
give patient 100% oxygen to replace air in the FRC will give the patient longer to stay alive
What is the risk of continuing cardiovascular medications during surgery?
hypotension
Which drug must be stopped before surgery because it causes prolonged hypotension?
ACE-i
What is the difference between aspirin and other NSAIDs?
aspirin irreversibly blocks platelets
How long before surgery is aspirin stopped? Why?
7 days
risk of bleeding
wait this long for half life of platelets not half life of aspirin
How many half lives would reduce a drug’s plasma concentration to an acceptable level?
5
Why are diabetic patients undergoing surgery at risk of
a) hypoglycaemia?
b) hyperglycaemia?
a) fasted means they cannot take medication
b) stress
What is an LMA?
a laryngeal mask airway: supraglottic airway device
What is the difference between an LMA and intubation?
LMA sits above the glottis in the oesophagus
whereas intubation involves inserting an endotracheal tube past the glottis
What is the glottis?
middle part of larynx where vocal cords are
What is the tidal volume?
amount of air inspired/expired with each breath during normal breathing
What is the vital capacity?
max amount of air expired after max inspiration
What is the inspiratory reserve volume?
maximum volume of gas inspired after normal expiration
so it is on top of the tidal volume
ie. inspiratory capacity - tidal volume
What is the expiratory reserve volume?
maximum volume of gas expired on top of tidal volume
ie. expiratory capacity - tidal volume
What is the residual volume?
the volume of gas that remains in the lungs after max exhalation
ie. keeps lungs open to stop resistance
What is the functional residual capacity?
the amount of air in the lungs after normal breathing
ie. their residual volume + the expiratory reserve volume
What proportion of lung volume is the FRC?
40%
Which nerves stimulate B2 adrenoreceptors in the smooth muscle of the lung? what does this do?
sympathetic stimulation increases diameter of airways –> bronchodilation
Which receptors are stimulated by parasympathetic nerves in the lung’s smooth muscle?
muscarinic receptors which decrease diameter of airways –> bronchoconstriction
Where are alpha1 receptors found? what do they do?
vascular smooth muscle
increase contraction
Where are alpha2 receptors found? what do they do?
CNS
dec sympathetic outflow (inhibit noradrenaline release)
Where are beta 1 receptors found? what do they do?
cardiac cells
inc heart rate, inc contractility, inc renin release
Where are beta 2 receptors found? what do they do?
vascular and bronchodilator smooth muscle
vasodilation + bronchodilation
What kind of neurotransmitter is GABA?
inhibitory: when it interacts with receptors of a neurone it makes it less likely to fire an action potential or release neurotransmitters
What is a GABA A receptor?
ionotropic: opens channel allowing negative Cl ion to flow into the cell, hyperpolarising it and making it less likely to fire an action potential
What are GABA B receptors?
g-protein coupled receptors that allow positive K+ to flow out of the neurone to hyperpolarise it and make it less likely to fire an action potential
What is atelectasis?
alveoli collapse or do not expand properly
What affect does smoking have on post-operative nausea and vomiting?
it decreases it
Why is it important to minimise gastric acid before surgery?
to prevent pulmonary acid aspiration which can cause a type of pneumonia called Mendelson syndrome
Should medication be given to a patient who is fasted for theatre?
yes
can be given with a sip of water
Should aspirin be stopped before surgery?
can be given if needed to reduce risk of post-op MI
How long before surgery should clopidogrel be stopped?
7 days
What warfarin patients are high risk?
- AF or valve disease w past arterial thrombosis
- VTE in last 3 months
- mechanical non-bio prosthetic valve
- multiple prosthetic heart valves
How should a patient usually on warfarin be managed post-op if there is no excess bleeding?
restart warfarin day of procedure and give prophylactic heparin
Why is it important that a diabetic patient isnt
a) hypo
b) hyper
peri-operatively?
a) can cause irreversible brain damage
b) wound infection + cardiac complications
How should glycaemic control of a diabetic patient be assessed before surgery?
HbA1c
- if >75mmol/mol its poor
- if >108mmol/mol needs control before proceed
What is important when considering PaO2?
inspired O2
Is pH a linear scale?
no it is logarithmic
How should naloxone be given?
dose = 400mcg
give in 40mcg boluses
Do anaphylaxis and sepsis cause vasodilation or vasoconstriction?
vasodilation
What is cardiac output equal to?
HR x SV
What is mean arterial blood pressure equal to?
CO x SVR
What is the dose and route of administration of adrenaline during
a) cardiac arrest?
b) anaphylaxis?
a) 1mg IV
b) 0.5mg IM
The ABGs of a patient in sudden cardiac arrest having had no bystander CPR and with no preceding ABG abnormality will likely demonstrate?
mixed respiratory and metabolic acidosis due to ischaemia and apnoea
How long before surgery should COCP be stopped?
4 Weeks
How long before surgery should clopidogrel be stopped?
7 days
How long before surgery should warfarin be stopped?
5 days
