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
what is the equation for cardiac output?
CO = Strove volume x heart rate
what is mean arterial pressure in cardiophysiology?
the average blood pressure of the entire cardiac cycle including both systole and diastole
A product of cardiac output and systemic vascular resistance
what are 5 complications of low mean arterial pressure?
hypoperfussion
hypoxia
anaerobic respiration
lactate production
tissue damage
How is central venous pressure monitored?
through a central venous catheter in vena cava/R atrium
what do positive inotropes do?
increase contractility fo the heart increasing cardiac output and MAP
used for patients with low cardiac output e.g. HF, MI or following heart surgery
how do most positive inotropes work?
catecholamines which stimulate the sympathetic nervous system via alpha and beta adrenergic receptors
what are 5 examples of catechloamine positive inotropes?
adrenaline
dobutamine
isoprenaline
noradrenaline - weak inotrope, mostly vasopressors
dopamine - at higher infusion rates
what are 2 examples of non-catechloamine positive inotropes?
milrinone - phosphdoesterase-3 inhibitor
levosimedan - increases myocyte sensitivity to calcium
how are positive inotropes given?
through central venous catheter
what are 3 examples of negative inotropes?
beta blockers
calcium channel blockers
flecainide
how do vasopressors work?
cause vasoconstriction which increased systemic vascular resistance therefore increasing mean arterial pressure
what are 6 examples of vasopressors?
noradrenalin - central line
vasopressin - central line
adrenaline - central line or bolus
metaraminol - bolus/infussion
ephederine - bolus
phenylephrine - bolus/infusion
what are 2 examples of antimuscarinics used to treat bradycardia?
glycopyronium - block acetylchline recepros
Atropine
what is an intra-aortic balloon pump?
a ballon inserted through the femoral artery to the descending aortic artery which is inflatted and deflated synchronised to the heart contractions to push blood back into the coronary arteries in diastole by inflating and pull blood out the heart by deflating in systole
causing increased coronary blood flow, reduces afterload and increased cardiac output
what are 5 indications for acute dialysis?
AEIOU
Acidosis - severe and non-responsive
Electrolyte abnormalities - treatment resistant
Intoxication - severe overdose
Oedema - severe and unresponsive pulmonary oedema
Uraemia symptoms - seizure, reduced conciousness
what are 2 different types of haemodialysis?
continuous renal replacement therapy
intermittent haemodialysis
what are 2 positional manoeuvres that can be used to open airway?
head tilt/chin lift
jaw thrust - preferred if ?C spine injury
what are oropharyngeal (guedel) airways used?
for very short procedures
to bridge difficult airways
when are laryngeal masks used (igel)?
when paralysis not required and patient able to self ventilate
not suitable for high pressure ventilation
poor control against reflux
when are tracheostomies used?
reduces work of breathing an dead space
useful for slow wean
humidified air required
useful in ITU
when are endotracheal tubes used?
provides optimal control of airway
short and long term
paralysis required
higher ventilation pressures
errors in insertion may lead to oesophageal intubation - need to monitor end tidal CO2 (capnography)
what is the american society of anaesthesiologists (ASA) level 1 classification of patients?
normal healthy, non- smoker, minimal alcohol
what is the american society of anaesthesiologists (ASA) level 2 classification of patients?
mild systemic disease - current smoker, social drinker, pregnant, obese, well controlled diabetes/HTN, mild lung disease
what is the american society of anaesthesiologists (ASA) level 3 classification of patients?
Patient with severe systemic disease
Functional limitation, poor control HTN/DM, morbid obesity, COPD, hepatitis, alcohol dependance, pacemaker, reduced ejection fraction, end stage renal disease with dialysis, MI >3 months ago, cerebrovascular accidnet
what is the american society of anaesthesiologists (ASA) level 4 classification of patients?
Patient with severe systemic disease that is constant threat to life
MI <3 months ago, ongoing cardiac ischaemia/severe valve dysfunction, severe reduction in ejection fraction, sepsis, DIC, ARD, end stage renal no dialysis
what is the american society of anaesthesiologists (ASA) level 5 classification of patients?
Moribund patient not expected to survive without operation
ruptures AAA, massive trauma, intracranial bleed with mass effect, ishcaemic bowel with cardiac pathology/multiple organ failure
what is the american society of anaesthesiologists (ASA) level 5 classification of patients?
declared brain dead who’s organs are being harvested
what is the MOA of propofol?
GABA receptor agonist
what is a common side effect of propofol?
pain on IV injection
what are 3 advantages of propofol?
rapid onset of anaesthesia
rapidly metabolised and little accumulation of metabolites
antiemetic properties
what 2 disadvantage of propofol?
causes moderate myocardial depression - hypotension
Pain on injection
what general anaesthetic has a very rapid onset but can cause marked myocardial depression and build up of metabolites?
sodium thiopentone - good for rapid sequence induction though cannot be used for maintenance infusion
what is the MOA of ketamine?
NMDA receptor antagonist
what are 2 advantages of ketamine as general anaesthesia?
moderate to strong analgesia also
little myocardial depression - good in haemodynamic instability
what is 1 side effect of ketamine as anaesthetic?
may induce state of dissociate anaesthesia and nightmares
what are 3 disadvantages of etomidate?
no analgesic properties
unsuitable for maintainance as may result in adrenal supression
post operative vomiting is common
Myoclonus is an adverse effect
what is an adverse effect of thiopental?
laryngospasm
what are 3 examples of volatile anaesthetics?
isoflurane
desflurane
sevoflurane
what are 3 adverse effects of volatile anaesthetics?
myocardial depression
malignant hyperthermia
halothane is hepatotoxic
when should NOS not be used for anaesthesia?
can diffuse into gas filled body compartments so should in avoided in pneumothorax as can cause tension
what is the largest cannula?
Orange - 16g - 270ml/min
what is the smallest canula?
blue - 22g - 33ml/min
what is the gage and flow rate of a grey canula?
16g
180ml/min
what is the gage and flow rate of a green cannula?
18g
80ml/min
what is the gage and flow rate of a pink cannula?
20g
54ml/min
what are 5 muscle relaxants?
suxamethonium
atracurium
vecuronium
pancuronium
rocuronium
what is the only depolarising muscle relaxant?
suxamethonium
what is the MOA of suxamethonium?
inhibits action of acetylcholine and NM junction
which muscle relaxant causes fasciculation prior to muscle relaxation?
suxamethonium
what muscle relaxant has the shortest onset and duration?
suxamethonium
what are 3 adverse effects of suxamethonium?
hyperkalaemia
malignant hyperthermia
genetic variation causing lack of acetylcholinesterase to break it down => longer to wear off
what is the duration of action of atracurium?
30-45 mins
what can be used to reverse atracurium?
neostigimine - acetylcholinesterase inhibitor
what is an advantage of atracurium?
not renally or hepatically excreted - broken down by hydrolysis in tissues
what are 3 side effects of atracurium?
generalised histamine release causes
facial flushing
tachycardia
hypotension
what is the duration of action of vecuronium?
30-40 mins
how is vecuronium excreted?
broken down by liver and kidneys => effect is prolonged in organ dysfunction
neostigimine can reverse what 2 muscle relaxants?
atracurium and vecuronium
what is the onset of action for pancuronium?
2-3 minutes
what is the duration of action of pancuronium?
up to 2 hours
is pancuronium reversible with neostigimine?
partially reversible
what is a contraindication to suxamethonium?
penetrating eye injuries or acute closed angle glaucoma as increase intra-ocular pressure
what are 5 early (<5 days) causes of post operative pyrexia?
blood transfusion
cellulitis
UTI
Pulmonary atalectasis - unlikely
Physiological systemic inflammatory reaction - usually in 1st day
what are 5 late (>5 days) causes of post op pyrexia?
VTE
Penumonia
Wound infection
anastomotic leak
what is postoperative ileus?
AKA parylitic ileus is a common complication of bowel surgery causing reduced bowel peristalsis and pseudo obstruction
what are 5 features of postoperative ileus?
abdo distension/bloating
abdo pain
nausea/vom
inability to fart
inability to eat
what can contribute to postoperative ileus?
deranged electrolytes - potassium, magnesium and phosphate
what is the management of postoperative ileus?
NBM
NG tube if vomiting
IV fluids + electrolytes if needed
TPN
what are the 3 ‘time out’ times in the operating theatre?
before induction of anaesthesia
before incision
before patient leaves
what must be checked before induction of anaesthesia?
patient confirmed site, identity, procedure, consent
site is marked
anaesthesia safety check
Pulse ox on patient and working
Allergies
difficult airway or aspiration risk
risk of >500ml blood loss
what is the antidote to local anaesthetic toxicity?
intralipid (lipid emulsion) 20%
1.5ml/Kg over 1 min followed by 0.25ml/kg/min infusion
what are 5 local anaesthetic agents?
Lidocaine
Bupivacaine
levobupivacaine
Tetracaine
Cocaine
what is the MOA of local anaesthetics?
inhibit neuronal condition by preventing opening of voltage gated sodium channels on axon preventing depolarisation of the axon and therefore stopping the action potential
what are 3 medications that interact with lidocaine?
beta blockers
ciprofloxacin
phenytoin
what are the signs of local anaesthetic toxicity?
initially CNS overactivity - sensory sensations, seizure, headache - then CNS depression - coma
then cardiac arrhythmias and arrest
what medication can be added to local anaesthetics to allow for increased doses by reducing systemic absorption?
adrenaline - causes vasoconstriction so less systemic absorption
what are 3 characteristics of lidocaine?
hepatically metabolised
protein bound
renally excreted
what surgeries may use cocaine as local anaesthetic?
ENT
what is a beneficial property of bupivicaine?
longer duration of action than lidocaine
what is a serious side effect of bupivacaine?
cardiotoxic
what is the max dose of lidocaine?
3mg/kg or max of 200mg - 20ml (1%)
what is the max dose of lidocaine with adrenaline?
7mg kg or max of 500mg - 50ml (1%)
what is the max dose of bupivocaine 0.5%?
2mg/kg or max of 150mg (30ml)
what are 5 surgeries where transfusion is unlikely?
simple hysterectomy
appendicectomy
thyroidectomy
elective c section
lap cholecycstecomy
do group and save no cross match needed
what are 2 examples of surgeries where chance of transfusion is likely?
salpigectomy for rupture ectopic
total hip replacement
cross match 2 units
what are 6 examples of surgeries where chance of transfusion is definite?
total gastrectomy
oophrectomy
oesophagectomy
elective AAA repair
cyctectomy
hepatectomy
cross match 4-6 units
what are 2 symptoms of malignant hyperthermia?
hyperpyrexia
muscle rigidity
what causes malignant hypethermia?
excessive release of Ca2+ from sarcoplasmic reticulum of skeletal muscle
associated with defect on chromosome 19
how is susceptibility to malignant hyperthermia inherited?
autosomal dominant
what are 3 medications that can cause malignant hyperthermia?
Halothane
suxamethonium
antipsychotics - neuroleptic malignant syndrome
what is the management of malignant hyperthermia?
dantrolene - 2-3mg/kg then 1mg/kg up to max of 10mg’kg
prevents Ca2+ release
what are 2 complications of NG tubes?
aspiration
misplaced tube
what is a contraindication to NG insertion?
head injury - basal skull fracture
what are 3 advantages of naso jejunal feeding?
avoids aspiration risk of feed pooling in stomach
Usually done intraopratively
safe to use following oesophagogastric surgery
what is a feeding jejunostomy?
surgically sited feeding tube
can be used lol term
low risk aspiration - safe following upper gi sugery
main risk - tube displacement and peritubal leakage following insertion - risk of peritonitis
what is PEG feeding?
percutaneous endoscopic gastrostomy
what is PEG feeding?
combined endoscopic and percutaneous tube insertion
not possible in patients who cannot undergo successful surgery
aspiration and insertion site leakage risk
what is TPN?
definitive option in patient whom enteral feeding is contraindicated in
individualised prescribing and monitoring needed
Administered centrally - strongly phlebitic
long term use associated with fatty liver and deranged LFTs
what is hartmans solution?
Na - 130 mmol
K - 4 mmol
Cl - 110 mml
Lactate - 28 mmol
what is a risk of excessive normal saline administration?
hypercholraemic acidosis
Hartmans is used in theatre as lower risk due to being more physiological
what are physiological plasma concentrations of sodium, potasium, chloride and bicarb?
Na - 137-147
K - 4-5.5
Cl - 95-105
Bicarb - 22-25
what are 4 risk factors for surgical hypothermia?
ASA grade 2 or higher
major surgery
low body weight
large amounts of cold IV infusions and blood transfusions
when should warming devices be used for patients?
if surgery >30 minutes or high risk patient
all fluids >500ml should be warmed before administration
what are 5 complications of perioprative hypothermia?
coagulopathy - hypothermia impaires clotting leading to increased bleeding
prolonged recovery from anaesthesia
impaired wound healing due to reduced blood flow
increased risk of infection
shivering - increases metabolic rate increasing risk of MI in vulnerable patients
what are 4 stages of wound healing?
heaemostasis
inflammation
regeneration
remodeling
what happens in wound haemostasis?
within minutes to hours of injury Vasospasm in adjacent vessels, platelet plug formation and generation of fibrin rich clot.
what happens in inflammation of a wound?
neutrophil migration into wound
growth factors release including basic fibroblast growth factor and vascular endothelial growth factor
fibroblasts replicate within adjacent matrix and migrate into wound
macrophages and fibroblasts cuple matrix regeneration and clop substitution
what happens in regeneration in wound healing?
platelet derieved growth factor and transformation growth factors stimulate fibroblasts and epithelial cells
fibroblasts produce collagen network
angiogenesis occurs and wound resembles granulation tissue
what happens in remodeling of wounds?
longest phase of healing
fibroblasts become differentiated and facilitate wound contraction
collagen fibres remodeled
microvessels regress leaving pale scar
what are hypertrophic scars?
excessive amounts of collagen within the bounds of the original injury
contains nodules
what are keloid scars?
excessive amounds of collagen within scar passing beyond the boundaries of the original injury
no nodules, may recur following removal
what medical patients are at increased risk of VTE?
patients with significant reduction in mobility for 3+ days
what surgical patients are at increased risk of VTE?
hip/knee replacement
hip fracture
GA and surgery >90 mins
Surgery of pelvis or lower limb >60 mins
Acute surgical admission with inflammatory or intrabdominal condition
surgery with significant reduction in mobility
what are 10 risk facts for VTE?
Cancer
>60 years
thrombophilia - FV leiden, antiphospholipid syndrome
BMI >35
Dehydration
medicao comorbidities - heart disease, metabolic/endo pathologies, resp disease, inflammatory conditions
critical care admission
HRT/COCP
Varicose veins
pregnancy or <6 weeks post-partum
what are 2 types of mechanical VTE prophylaxis?
anti-embolism stockings
intermittent pneumatic compression (flowtrons)
what are 3 medications used for VTE prophylaxis?
LMWH - enoxaparin - reduce dose in renal imapairment
Unfractioned heparin - in CKD
Fodaparinux sodium
when should COCP be stopped before surgery?
4 weeks
what are 2 post surgical interventions to prevent VTE?
keep patient hydrated
mobalised asap
how long should VTE prophylaxis be given for elective hip replacement?
28 days LMWH + TEDs until discharge
or LMWH 1 days + aspirin 28 days
or riveroxiban
how long should VTE prophylaxis be given for elective knee replacement?
LMWH 14 days with TEDs until discharge
or Aspirin for 14 days
or riveroxiban
How long after spinals/epidural removal can VTE prophylaxis be given?
4-6 hours
what are 3 measures that increase risk of surgical site infection?
shaving wound using razor
non-iodine impregnanted incise drapes
tissue hypoxia
delayed administration of prophylactic antibiotics
when are Abx needed in surgery?
placement of prosthesis or valve
clean-contaminated surgery
contaminated surgery
what nerve may be damaged in an auxillary nerve clearance?
long thoracic
what procedure can damage the hypoglossal nerve?
carotid endarterectomy
what electrolyte disturbance can be caused by neurosurgery?
hyponatraemia due to SIADH
what causes ileus following GI surgery?
fluid sequestration and loss of electrolytes
what are 4 symptoms of post operative ileus?
abdo distension/bloating
abdo pain
nausea and vomiting
complete constipation
what is post operative ileus?
deceleration or arrest in motility following surgery
what are 6 RF for post operative ileus?
increased age
electrolyte disturbance
neurological disorder
anticholinergic/opioid use
intra surgical opioids
excessive oprative interstinal handling
what investigation is used to confirm post op ileus?
CT abdo pelvis
what is the management of post op ileus?
NBM
NG tube suction
Blood
encourage mobalisation
reduce opiates
TPN with prolonged ileus
what are patients post cardiac surgery prone to?
hypokalaemia and arrythmias
what is an anastomotic leak?
leak of luminal contents from surgical join
what are 5 risk factors for anastomotic leak?
meds - immunosupressive
Diabetes
emergency surgery
extended operative time
peritoneal contamination
what are 4 signs of anastomotic leak?
3-5 days post op
worsening abdo pain
sepsis signs
peritonism
how do you diagnose anastomotic leak?
Ct with IV contrast
what is the management of anastamotic leak?
IV Abx and bowel rest if minor
endoluminal vacuum therapy
surgical intervention - laparotomy and wash out
what generic test should be done pre-op for elective cases?
bloods - fbc, u+e, lfts, clotting, group and save
urinalysis
pregnancy test
sickle cell test
ECG
how long can patients have clear fluids before surgery?
up to 2 hours before
how long can patients have solids before surgery?
up to 6 hours before
what are 3 complications of poorly managed diabetes during surgery?
increased risk wound/resp infection
increased risk post op AKI
increased length hospital stay
what is classed as good glycaemic control?
hba1c <69
what patients need variable rate infusion?
patients with poorly controlled diabetes
surgery requiring missing more than one meal
how should metformin be taken on day of surgery?
as normal
if TDS - omit lunch time dose
how should sulfonylureas be taken on day of surgery?
omit
risk of hypo
how should -gliptins be taken on day of surgery?
take as normal
how should GLP-1 analogues be taken on day of surgery?
take as normal
how should SGLT-2 inhibitors be taken on day of surgery?
omit on day of surgery
risk of normoglycaemic DKA
how should once daily insulins be taken on day before and day of surgery?
80% of usual dose
how should biphasic or ultralong acting insulins be taken on day of surgery?
half usual morning dose and leave evening unchanged
at what eGFR should metformin be omitted for surgery?
<60
what % of surgical patients will get a surgical site infection?
5%
what are 4 things that increase risk of surgical site infection?
Shaving wound with razor
using non-iodine impregnate incision drapes
tissue hypoxia
delayed administration of prophylactic antibiotics in tourniquet surgery
what are 4 preoperative measures that can be taken to reduce surgical site infections?
don’t remove body hair routinely
Use electrical clippers for hair removal
antibiotic prophylaxis if - placement of prosthesis, clean contaminated surgery, contaminated surgery
aim for single dose IV Abx on anaethesia
what are 2 measures that can be done to reduce risk of surgical site infection intraoperatively?
prep skin with alcoholic chlorhexidine
cover surgical site with dressing
what are the 2 most common organisms in surgical site infection?
S. aureus
E. Coli
what are the 3 classifications of surgical site infection?
Superficial incisional - within 30 days, skin and subcutaneous tissue
Deep incisional - within 30 days or a year if due to implant, fascia and muscle layers involved
Oran/space - within 30 days or a year if due to an implant, any anatomy other than incisions which was opnened/manipulated during surgery
what percentage of fluid in intracellular?
60-65%
28L
what percentage of fluid is extracellular?
35-40%
14L
what proportion of fluid is plasma, interstitial and transcellular?
5%
24%
3%
3L
10L
1L
what are 4 things that shift oxygen dissociation curve to left?
L rule - shifts to left, Lower O2 delivery
Low H+ - alkali
Low pCO2
Low 2,3 DPG
Low temperature
also HbF, methaemoglobin, carboxyhaemoglobin
what are 4 things that cause O2 dissociation curve to shift to R?
CADET face Right
Co2 high
Acid
2,3-DPG high
Exercise and Temperature
what is the FiO2 of room air?
21%
what is the FiO2 delivered via nasal canula?
24-44%
what is the FiO2 of simple face masks?
40-60%
what is the FiO2 of non-rebreathe mask?
60-95%
when should warfarin be stopped before elective surgery?
5 days
when should DOACs be stopped before surgery?
24-72 hours depending on creatinine clearance
what are 6 cytochrome P450 inducers?
PC BRAS
Phenytoin
Carbamazepine
Barbiturates
Rifampicin
Alcohol (chronic excess)
Sulphonylureas
lead to decreased concentrations of other drugs
what are 9 cytochrome P450 inhibitors?
AO DEVICES
Allopurinol
Omeprazole
Disulfiram
ERYTHROMYCIN
Valporate
Isoniazid
Ciprofloxacin
Ethanol (acute intoxication)
Sulphonamides
Increase concentration of drugs
what are 7 medications to stop pre surgery?
I LACK OP
Insulin
Lithium
Anticoagulant/platelets
COCP/HRT
K-sparing diuretics
Oral hypoglycaemics
Perindopril and other ACEIs
what should the COCP /HRT be stopped pre-op?
4 weeks before
when should lithium be stopped pre-op?
omit dose of day before
