Anaesthetics Flashcards
3 components of anaesthesia?
hypnosis (amnesia)
analgesia
muscle relaxation (akinesis)
3 levels of hypnosis? how do anaesthetic agents therefore act?
awake (LA)
sedation (sedation)
asleep (GA)
3 local techniques:
local - minor surgery - laceration repair
regional - target specific nerves (brachial plexus or sciatic) - for post-op pain relief
neuraxial - spinal/epidural - intra-op, post-op use
what is the difference between spinals and epidurals?
Spinal (subarachnoid block) goes through both ligaments and dura to CSF via an injection at lumbar region, single bolus, faster onset, smaller dose, anaesthetic only
Epidural - needle goes between ligaments and dura and a catheter is passed
continuous infusion, slow onset, larger dose required, anaesthesia+analgesia, T or L spine
where are spinals and epidurals incisions done?
below the highest nerve root affected by the block
normally this is T10 dermatome - umbilicus
why is incision for epidurals/spinals not done above this level?
GA would be required
also epidurals would be insufficient post-op analgesia
MODA: LA:
reversibly blocks Na+ channels
inhibits generation of action potentials in nerve cells
smaller diameter, unmyelinated fibres blocked first
order of block: L.A:
b fibres (autonomic - vasoconstriction)
C and A(d) - pain and temp
A(b) - light touch and pressure
A(a) and A(Y) - motor and proprioception
what is often used in combination with LA? why?
adrenaline - vasoconstriction leads to reduced bleeding and prolonged effects of the LA through reduced absorption from tissues
where should adrenaline not be used?
in end arteries such as fingers
examples of L.A?
lidocaine
bupivicaine
lidocaine onset and duration, when used?
immediate onset, lasts 15m
small procedures - laceration repairs, chest drains, large cannulae
bupivicaine onset and duration, when used?
regional, spinal, epidural
10m onset - lasts 2h anaesthetic, 12-24h as analgesic
what do epidural infusions have running through them commonly and what should this indicate?
opioids
do not prescribe further opioids
what does induction and maintenance mean regarding general anaesthesia?
induction - sending to sleep
maintenance - keeping asleep
how are hypnotic drugs given?
inhaled or IV
3 examples of inhalational hypnotic drugs:
Isoflurane - cheapest - maintains sedation
Desflurane - maintains sedation - quick wears off
Sevoflurane - induces+/-maintains sedation
3 examples of IV hypnotic drug:
Propofol - quick onset - commonest - also antiemetic - fast redistribution (fast recovery of consciousness)
Thiopenthal - quick - emergency anaesthetics
Ketamine - used in CVS instability - also analgesic
pros and cons of induction via inhaled and IV:
IV - commoner, requires cannula, rapid onset, depresses airway reflexes, apnoea common
Inhaled - good for needle phobics, slow onset, irritates airway, usually keep breathing
once GA has taken effect, patients often stop breathing, how is their airway managed? (2)
spontaneous breathing
controlled ventilation
t1rF caused by what specific problem?
alveolar collapse or fluid in alveoli
name an agent which reverses the effects of midazolam?
Flumazenil
which drug is hepatotoxic and also can harm theatre staff if accumulated use?
halothane
name an anaesthetic agent which has anti emetic properties
propofol
Propofol features:
GABA receptor agonist
Rapid onset of anaesthesia
Pain on IV injection
Rapidly metabolised with little accumulation of metabolites
Proven anti emetic properties
Moderate myocardial depression
Widely used especially for maintaining sedation on ITU, total IV anaesthesia and for daycase surgery
Sodium thiopentone
features:
Extremely rapid onset of action making it the agent of choice for rapid sequence of induction Marked myocardial depression may occur Metabolites build up quickly Unsuitable for maintenance infusion Little analgesic effects
Ketamine features:
NMDA receptor antagonist
May be used for induction of anaesthesia
Has moderate to strong analgesic properties
Produces little myocardial depression making it a suitable agent for anaesthesia in those who are haemodynamically unstable
May induce state of dissociative anaesthesia resulting in nightmares
Etomidate features:
Has favorable cardiac safety profile with very little haemodynamic instability
No analgesic properties
Unsuitable for maintaining sedation as prolonged (and even brief) use may result in adrenal suppression
Post operative vomiting is common
A seventy-two-year-old woman with rheumatoid arthritis is recovering on the ward 6 days following a left hemi-colectomy for a tumour in the descending colon. She complains to the nurse looking after her that she has developed pain in her abdomen. The pain is diffuse and came on suddenly but has gradually been getting worse since onset. She ranks it an 8/10. She has not opened her bowels or passed flatus since the procedure. dx? iX?
anastamotic leak
diagnosed with abdominal CT
what is contraindication of using LMA?
being non-fasted
LMA doesn’t isolate the airway and cannot provide control against gastric reflux - risk of asapiration
also obesity (morbid)
contraindications for nasopharyngeal airway?
Basilar skull fracture and underlying coagulopathy
periorbital ecchymosis and clear fluid leaking from one nostril
which manouvres can open the airway? (3)
head tilt
chin lift
jaw thrust
is xray needed commonly pre-op in patients?
no
what do nice commonly recommend ix for pre-op?
ECG in over 65
renal disease - FBC, ECG
On approaching the bedside of an elderly obese man, you find him quite drowsy. When you call out his name, you hear a grunting noise. You call out for the nurse’s help. Oxygen saturations are 82% on air.
What is the next step in the immediate management of this patient?
head tilt, chin lift, jaw thrust first
A 17-year-old man undergoes an elective right hemicolectomy. Post operatively he receives a total of 6 litres of 0.9% sodium chloride solution, over 24 hours. Which of the following complications may ensue?
hyperchloric acidosis
A 45-year-old woman is admitted with acute pyelonephritis. She requires intravenous access for antibiotics and maintenance fluids as she is currently taking limited fluids due to vomiting. She is haemodynamically stable. which cannula?
1x20G cannula
A 3-year-old is injured in a road traffic accident and is hypotensive and tachycardic due to a suspected splenic injury, she is peripherally shut down. how to get access?
Intraosseous
A 73-year-old man with Dukes C colonic cancer requires a long course of chemotherapy. He has poor peripheral veins. access??
Hickmann line
which site is preferred for central line access?
internal jugular as femoral high infection rate
50M RTC The helicopter emergency service attends the scene. GCS is 7 (E2, V1, M5) and he has no air entry on the left side of the chest, with an open fractured neck of femur on the right hand side.
Temperature: 37.6ºC.
Heart rate: 110bpm.
Blood pressure: 60/40mmHg.
SpO2: 95% on air.
Respiratory rate: 22/min.
His fractured femur is reduced at the scene but in view of his low GCS the decision is made to intubate him at the scene. What is the best agent for induction of anaesthesia?
Ketamine
as good for those who are haemodynamically unstable
healthy, non-smoker, minimal or no alcohol use - ASA?
1
Including, but not limited to, well-controlled diabetes, hypertension. Social drinker. Smoker - ASA?
2
ncluding, but not limited to: poorly control diabetes/asthma, hypertension. BMI > 40. Previous MI > 6m ago. ASA?
3
also ESRD
ncluding, but not limited to: recent MI (<3m), severe reduction in ejection fraction - ASA?
4
Including, but not limited to: ruptured AAA, massive trauma. ASA?
5
cause of RLL consolidation in pt who has been ventilated post op for 14/7?
tracheo-oesophageal fistula formation
A 22-year-old lady undergoes a total thyroidectomy for Graves disease. 6 hours post operatively she develops respiratory stridor and develops a small haematoma in the neck - mx?
immediate reoval of sx clips on ward
44-year-old lady undergoes a total thyroidectomy for recurrent multinodular goitre. 3 days post operatively she is still troubled by a hoarse voice. mx?
laryngoscopy