Anaesthetics Flashcards
why are patients fasted before general anaesthesia?
to reduce risk of aspiration of stomach contents and subsequent pneumonitis
when is risk of aspiration highest in general anaethesia?
before and during intubation and during extubation
what is the typical fasting for an operation?
6 hours before no food or feeds
2 hours before no clear fluids - fully NBM
what is preoxygenation in anaesthesia?
when patient has several minutes of breathing 100% O2 to give a reserve of oxygen for the period between when they lose consciousness and when they are successfully intubated and ventilated
what is premedication in general anaesthesia?
medication given to a patient before they are put under inorder to relax them, reduce anxiety, pain and make intubation easier
what 3 medications may be used for premedication?
benzodiazepines - to relax muscles and reduce anxiety as well as causing amnesia - midazolam
opiates - to reduce pain and hypertensive response to laryngoscope - fentanyl or alfentanyl
Alpha-2adrenergic agonists - help with sedation and pain - clonidine
when is rapid sequence induction used?
in emergency/non-fasted patients
in high risk patients - GORD, pregnancy
what is induction in anaesthetics?
when the patient becomes unconsious
what are 2 methods that can be used in rapid sequence induction to reduce risk of aspiration?
upright positioning of patient
cricoid pressure
what is the triad of general anaesthesia?
Hypnosis
muscle relaxation
analgesia
what are the 2 delivery methods of hypnotic agents?
IV or inhalation
what are 4 IV medications used as hypnotic agents in general anaesthesia?
propofol - most common
ketamine
thiopental sodium
etomidate - rare
what are 4 Inhaled hypnotic agents used in general anaesthesia?
sevoflurane - most common
desflurane - bad for environment
isoflurane - rare
nitrous oxide
what is total IV anaesthesia, what medication is usually used and what are the benefits?
when IV medication is used for both induction and maintenance of general anaesthesia
propofol most commonly used
nicer recovery for patient
How do muscle relaxants work?
block acetylecholine at neuromuscular junction from stimulating response
what are the two categories of muscle relaxants?
depolarising and non-depolarising
what medications can reverse the effect of neuromuscular blocking agents in anaesthetics?
cholinesterase inhibitors - neostigimine
what is an example of a depolarising muscle relaxant?
suzamethonium
what are 2 examples of non-depolarising muscle relaxants?
rocuronium
atracurium
what medication can be used to reverse non depolarising muscle relaxants specifically?
sugammadex
what are 4 common medications used for analgesia in general anaesthetics?
fentanyl
alfentanil
remifentanil
morphine
what 3 antiemetics are often given for postoperative nausea?
ondansetron (5HT3 receptor antagonist) - Avoid in long QT risk
Dexamethasone - caution in diabetes or immunocompromise
cyclizine - H1 receptor antagonist - caution in HF and elderly
what tests can be done to check muscle relaxants have worn off before emergence?
nerve stimulation either of ulnar nerve for thumb twitching or of facial nerve for orbiculares oculi muscle movement
normally tested in train of four - stimulate nerve 4x > shouldn’t get weaker with repeated stimulation > sign muscle relaxant not quite worn off yet
what are 2 most common risks of general anaesthesia?
sore throat
post op nausea and vomiting
what are 7 significant risks of general anaesthesia?
accidental awareness
aspiration
dental injury
anaphylaxis
cardiovascular event
malignant hyperthermia - rare
death
what is malignant hyperthermia?
rare potential fatal response to anaesthesia
what medications increase risk of malignant hyperthermia?
volatile anaesthetics
suxamethonium
what is the inheritance pattern for increased risk of malignant hyperthermia?
autosomal dominant
what are 6 signs of malignant hyperthermia?
Hyperthermia
increased CO2 production
tachycardia
muscle rigidity
acidosis
hyperkalaemia
what is the treatment of malignant hyperthermia?
Dantrolene - interrupts muscle rigidity and hypermetabolism by interfering with movement of calcium ions in skeletal muscle
what dose of dantrolene is given in malignant hyperthermia?
2-3mg/Kg then a further 1mg/kg if necessary
How are peripheral nerve blocks usually performed?
by ultrasound with help of nerve stimulator to accurately apply anaesthesia to target nerve
what is central neuraxial anaesthesia also known as?
spinal block
where is anaesthsia injected in a spinal block?
local anaesthetic into CSF within subarachnoid space
where is a spinal block usually placed?
L3/4 or L4/5
how long do spinal blocks usually last?
1-3 hours
where is the anaesthesia injected in an epidral?
outside dural mata in epidural space - medication diffuses to surrounding tissues and spinal nerve roots
what medication is often used in epidurals?
levobupivacaine w/ or w/o fentanyl
what are 6 adverse effects of epidural?
headache if dura is punctured
hypotension
motor weakness in legs
nerve. damage
infection including meningitis
haematoma - may cause spinal cord compression
what are 2 added risks to epidural in pregnancy?
prolonged second stage
increased probability of instrumental delivery
what size endotrachial tubes are generally for women?
7-7.5mm
what size endoctrachial tubes are generally for men?
8-8.5mm
what is the name of the additional hole in the tip of the endotrachial tube in case of blockages to the main hole?
murphy’s eye
what can be used to check the pressure of the endotrachial pilot balloon?
a manometer (pressure sensor) to check for under or over inflation
what are two devices that can be used to help with endotrachial intubation?
A bougie - smaller than endotrachial tube, inserted into trachea first to guide endotrachial tube
Stylet - metale wire inserted into endotrachial tube to bend to correct shape
what is awake fibre optic intubation?
endoscopy guided intubation in awake patients
what is trismus?
difficulty opening the jaw due to pain or restriction
what are supraglottic airway devices?
1st line after failure of intubation
form a seal around the opening of the larynx
can have inflatable or non-inflatable cuffs
I-gel = non-inflatable
what are guedel airways?
oropharyngeal airway that is ridgid and creates a passage between front of teeth and base of tongue maintaining a patent upper airway
how do you measure the size of a guedel airway?
from centre of mouth to angle of jaw
how are nasopharyngeal airways sized?
from edge of nostril to tragus of ear
what is a contraindication to nasopharyngeal airway insertion?
base of skull fracture
what are 6 signs of base of skull fracture?
Racoon eyes
battles sign - bruising of mastoid process
CSF rhinorrhoea
cranial nerve palsy
haemotympanum
what are 5 indications for tracheostomy?
resp failure with need for long term ventilation
prolonged weaning from mechanical ventilation in ICU
upper airway obstruction
management of resp secretions in patients with paralysis
reducing risk of aspiration
what are the 4 levels of airways for patients?
plan A - laryngoscopy and tracheal intubation
plan B - supraglottic airway device
plan C - face mask ventilation and wake patient
plan D - cricothyroidotomy
what are arterial lines?
type of cannula in artery which can measure BP and take ABG samples
NEVER GIVE MEDICATION THROUGH ARTERIAL LINE
what are 3 veins that central lines can be inserted into?
internal jugular
subclavian
femoral
what are vas caths?
type of central venous catheter inserted temporarily usually into internal jugular or femoral vein with 2/3 lumens that can be used for short term haemodialysis
what is a picc line?
a type of central line fed through venous system peripherally until in vena cava or R atrium
low risk of infection and can stay for longer periods
what is a hickman line?
a type of tunnelled central venous catheter which entres skin on chest and travels through subcut tissue into subclavian or jugular vein to sit in superior vena cava
used for regular IV treatment e.g. chemo or dialysis
what is a swan-ganz catheter?
a pulmonary artery catheter that’s inserted into internal jugular vein though central venous system through heart and into pulmonary artery
can be used to measure pressures in pulmonary artery
what is a portacath?
type of central venous catheter with small chamber under skin at top of chest used to access device that is connected to catheter that travels through SC tissue into subclavian vein with tip in SVC or R atrium
what are 3 scoring systems that can be used to predict mortality at time of admission to ICU?
APACHE - acute physiology and chronic health evaluation
SAPS - simplified acute physiology score
MPM - mortality prediction model
what does PEG stand for?
percutaneous endoscopic gastrostomy
how should TPN be delivered?
through central line to avoid thrombophlebitis
what are 9 complications of ICU admission?
Ventilator associated lung injury
ventilator associated pneumonia
catheter related blood stream infections
catheter associated UTIs
stress related mucosal disease - erosion of upper GI tract
Delirium
VTE
critical illness myopathy
critical illness neuropathy
what are 2 short term complications of ventilators?
pulmonary oedema
hypoxia
what are 3 traumas caused by ventilators?
barotrauma - damage from pressure changes
volutrauma - damage from overinflation of alveoli
inflammation
what are 4 long term complications of ventilator trauma?
lung fibrosis
reduced lung function
recurrent infection
cor-pulmonale
what patient positioning reduces risk of ventilator associated pneumonia?
bed at 30 degree angle with head elevated - reduces bacterial aspiration
what is stress related mucosal disease?
damage to stomach mucosa due to impaired blood flow. increases risk of upper GI bleed
what can be done to reduce risk of stress related mucosal disease?
PPIs or H2 receptor antagonists
starting NGs early even in small volumes
what medication can be used in ICU to sedate patients?
Dexmedetomidine
what are 2 options for reducing risk of VTE in ICU?
LMWH
Intermittened penumatic compression - flowtrons
what is critical illness myopathy?
muscle wasting and weakness during critical illness
affects limbs and respiratory muscles most
Corticosteroids and muscle relaxants increase risk
what are 2 long term effects of critical illness myopathy?
reduced exercise capacity
reduced QOL
What is critical illness polyneuropathy?
degeneration of sensory and motor nerve acons during critical illness and ICU treatment often alongside critical illness myopathy
what can reduce risk of critical illness polyneuropathy?
good glycaemic control
what is the pattern of critical illness polyneuropathy?
symmetrical weakness, decreased muscle tone and reduced reflexes
what is acute respiratory distress syndrome?
severe inflammatory reaction of lungs causing atelectasis, pulmonary oedema, decreased lung compliance and fibrosis (after 10 days)
clinically causes acute resp distress, hypoxia, bilateral infliltrates on CXR
what is the management of ARDS?
resp support
prone positioning
careful fluid management to avoid excess collecting in lungs
why are patients with ARDS positioned prone?
reducing compression of lungs by other organs
improve blood flow to lungs
improve clearing of secretions
improve overall oxygenation
reduce need for mechanical ventilation
what % FiO2 can be delivered via nasal cannulae?
24-55% O2
what % FiO2 can a simple face mask deliver?
40-60% O2
what FiO2 can venturi masks deliver?
24-60% O2
what FiO2 can non-rebreathe mask deliver?
60-95% O2
what is the FiO2 of 1L nasal cannula?
24%
what is the FiO2 of 2L nasal cannula?
28%
what is the FiO2 of 4L nasal cannula?
36%
what is the FiO2 of 5L via face mask?
40%
what is the FiO2 of 8L via face mask?
60%
what is the FiO2 of 8L via non-rebreathe mask?
80%
what is the FiO2 of 10L via non-rebreathe mask?
95%
what is positive end expiratory pressure (PEEP)?
additional pressure in the airway at the end of expiration to help keep the airways from collapsing and improve ventilation of alveoli
what is CPAP?
continuous positive airway pressure - constant pressure added to lungs to keep airway expanded (PEEP) used in conditions where airways are likely to collapse
what is NIV?
a full face mask, hood or tight fitting nasal mask that forcefully blows air into the lungs to ventilate them
BiPAP - Bilevel positive ailrway pressure
cycles of high and low pressure to correspond to inspiration and expiration
what are 7 basic controls for mechanical ventilation?
FiO2
Resp rate
tidal volume
inspiratory:expiratory ratio
peak flow rate
peak inspiratory pressure
positive end expiratory pressure
what is preload in cardiophysiology?
the amount the heart muscle is stretched when filled with blood BEFORE contraction
relates to the volume of blood in the ventricle at the end of diastole
what is afterload in cardiophysiology?
the resistance that the heart muscle has to overcome to eject blood from the left ventricle
How much resistance there is to pushing blood through aortic valve
what are 2 common causes of raised afterload?
HTN
aortic stensis
what is contractility in cardiophysiology?
the strength of the heart muscle contraction
what is systemic vascular resistance in cardiophysiology?
resistance in systemic circulation that the heart must overcome to pump blood around the body
what is the stroke volume in cardiophysiology?
volume of blood ejected in each beat
what is the cardiac output in cardiophysiology?
the volume of blood ejected by the heart per minute