osce stuff , anatomy, positioning Flashcards
which artery is most likely responsible for extradural haematoma? what do they look like and why?
middle meningeal
found at pterion - junction between temporal, parital and ethmoid
extradural haematomas arise between dura and skul and are bounded by attachment sites of dura and skull hence give a classic concave shape.
ich
what type of vessel and patient group is a subdural haematoma seen in?
venous - slow bleed
elderly, chronic alcohol , coagulopathies
What are the indications for jugular venous cannulation …
Medications - norad, high concentration pottasium , long term abx
Difficult access
Measurement of CVP , CO monitoring and swan ganz
Measurement of venous saturations and paO2
which type of brain bleed, classically presents with a lucid period?
extra dural
where are subdural haematomas found
between dura and arachnoid
limited by the one side of brain by falx cerebri
cresent shape
how would a chronic subdural appear on CT?
less bright, darker area of bleed.
which 3 views of C spine are needed to assess?
Lateral view - should be able to see all 7 vertebrae
Anteroposterior view
Open mouth odontoid view - good for diagnosing fracture or lateral displacement of odontoid process
how is a C spine Xray systematically reviews?
allignment:
a line should pass through anterior vertebral bodies
a line should pass through anterior and posterior aspect spinal canal
a line passing through the tips of spinous process
bony
assess height of the bodies
contours
pedicles
transverse and spinous processes
cartilages - invertebral disc space.Vertebral malalignment of more than 3mm suggests vertebral dislocation.
what is the normal space between anterior arch of atlas and odontoid process
less than 3mm
what should be considered when optimising patients positon
patient
* avoid nerve injuries
* avoid dislogment of ET tube
surgery
* correct positon for surgery - may need to be a compromise
access for anaesthetist e.g. IV cannula, NMBA monitoring
what patients are most at risk of poor positioning?
elderly - less mobile joints, poor skin integrity, less fat to pad nerves
obesity - more likely to be difficult to position and therefore may lead to poor positoning
diabetic - poor skin
arthritis
what are the factors that can result in positional harm
tourniquets
abnormal positons e.g. prone, head down (cerebral oedema)
long operations
anaesthesia - patient cant feedback
what are the mechanism of nerve injury from poor positoning ?
compression
ischaemia
direct truama - cutting
tension - stretch
what are the different types of nerve injury ?
Neuropraxia - mild tempory from compression
axonetmesis - axon damaged but epineurium and perineureum intact. wallerian regeneration 1-2mm/day
neuronetmesis - complete sethering, hard to recover from
consequence of ulnar nerve damage
loss of sensation medial 1 1/2 fingers palmer and dorsal surface
motor - finger abduction and adduction, adduction of the thumb. hypothenar weakness (little finger)
what are the anaesthetic consequences of laparoscopic surgery
A: dislogement of tube - endobronchial intubation. LMA doesnt sit well - should avoid LMA. increased risk of aspiration due to raised gastric pressures
B: reduced FRC, closing volume may now exceed FRC, atlectasis and shunting, hypoxaemia. can add PEEP to overcome. increased airway pressures, risk of barotrauma.
CO2 absorption - respiratory acidosis
C: increased thoracic pressures, reduce preload and hence CO.
increased PVR
D: raised ICP, can get cerebral oedema
E: poor renal perfusion due to low CO, AKI, poor clearance of drugs
G: poor GI and liver perfusion - affects metabolism of anaesthetic drugs. increased N&V
what are the contraindications to laparoscopic surgery?
known raised ICP
haemodynamic instabilty
patent FO - increased PVR and pressure on right side may reverse shunt.
how can patient injury be minimised in surgery
secure to table
use padding
tape eyes closed
tourniquet timer
awareness of positoning e.g. how long been in trendelburg - have a break
what is well leg compartment syndrome?
if a leg is raised
there is reduced perfusion especially in pneumoperitoneum
can mimic compartment syndrome
more likely in long operation, large muscle mass, hypotension.
can flatten every 2 hours to re-establish circulation
Which drugs have to be given via central line?
NORAD , vasopressin
Chemotherapy drugs
High conc pottasium
TPN
In what situations may a DINIMAP be inaccurate ?
Incorrect cuff size
Arrhythmias
Movement
External pressure
How are risks to patient having laser airway surgery minimised
Low FiO2
Special ET non flammable tube
Double cuff
Filled with saline or methyl blue dye
Non reflective Matt surgical instruments
How are risks to patient having laser airway surgery minimised
Low FiO2
Special ET non flammable tube
Double cuff
Filled with saline or methyl blue dye
Non reflective Matt surgical instruments
What is the definition of ultrasound?
Sound waves above the frequency of human hearing (>20kHz)
What frequency of ultrasound is used in medical ultrasound
5 MHz (ultrasound is 20KHz )
What is the piezoelectric effect ?
The phenomenon whereby piezoelectric crystals are able to convert current of a specific frequency into sound waves of a corresponding frequency and vice versa. It occurs because current will cause crystals to vibrate and emit sound waves
What is the name of these probes , give examples of when they are used
Linear probe - e.g for nerve blocks - brachial plexus
Curved linear to do a spinal in obese patient and view the ligamentum flavum
Phased array probe - subcostal imaging of the heart
what is this..
von recklinghaus oscilonometer
(2 wires)
what is this..
sphygomomanometer
s fig mo man o meter
what is this
DINAMAP
device for indirected non invasive automated MAP monitoring
what are the causes of ultrasound signal attenuation?
Ultrasound signal attenuation refers to the reduction in the strength (amplitude) of an ultrasound wave as it travels through tissue or other media
absorption of waves by tissue
reflection and scattering of waves
divergence and refraction of sound waves as they pass through tissues.
what can an erector spinae block be used for? what is an alternative block?
rib fractures, breast surgery
paraspinal block is an alternative as more likely to get ventral rami - more effective but riskier - treated like neuroaxial e.g. cant do if on anti-coagulants.
(the ventral rami go all the way around to the front and cover sensory up to sternum, dorsal rami only cover the back area)
where do you inject in an interscalene block?
between C5 and C6
what other nerves can be found near middle scalene in a interscalene block?
long thoracic
dorsal scapular
(could damage these when needling)
Reasons for needing a tracheostomy?
weaning on ITU
upper airway surgery - inserted by ENT
someone cant clear secretions - risk of aspiration
What is the RAS score used on ITU?
Richmond agitation sedation scale
from +4 to -5
normal is 0
+4 - very aroused e.g. fighting
-5 - very sedated / unarousable
What are the reasons for tracheostomy weaning on ITU?
Can reduce sedation - assess neurology better, able to get back to more normality
passy mure valve and talking
mouth hygeine
what is the difference between surgical and percutaneous trachy
surgical tracheostomies are usually in more complex cases - improtant to know when assessing as this can tell you if this is a complex case.
infection rates much higher with surgical.
at what level is tracheostomy inserted?
usually between 2nd and 3rd tracheal ring
how do you descibe a tracheostomy tube..
size - internal diameter
cuffed/ uncuffed
fenestrated?
inner tube?
adjustable length?
what is this..
passy muir valve
inspiration allowed but valve shuts on expiration, expired air diverted to upper airway for phonation
MUST have cuff down!
what are the complications of tracheostomies?
immediate - bleeding, failure, ventilation issues, reactions to drugs given (roc, proporfol), damage to posterior tracheal wall
early - secretions blocking tube, dislodged tube
later - innonimate artery erosion and bleed, infections
how long can a percutaneous trachy be left in?
30 days
in an emergency for someone with a trachy, what 2 things can be found at the bedside?
blue box - trachy equiptment e.g. paeds face mask , suction catheter
trachy algorithm
what spinal levels mediate pain in labour?
T10 to L1 - contractions
S3 to S5 - delivery
how common are some of the complications of epidurals..
NAP3
Failure to work- 1 in 20
Hypotension - 1 in 50
Headache - 1 in 150
Nerve damage - temporary 1 in 2000, permanent 1 in 15000
paralysis 1 in 250,000
risk of meningitis also rare
for spinal anaesthesia in C section, what level do you want to block up till?
T4 - nipple line
describe the mallampati scoring system..
scored from 1 to 4 depending on view of oropharynx. correlated with ease of intubation
1 = PUSH - tonsillar Pillar, uvula, soft palate, hard palate
2 = USH = uvula, soft palate, hard
3 - SH = soft and hard
4- H = hard palate only
class 3 and 4 - should suggest difficult intubation
what is the thyromental distance?
tip of thyroid cartilage to tip of chin
should be more than 6cm, less than this makes laryngoscopy hard
what sternomental distance suggests difficult laryngoscopy?
less than 12.5cm
what scoring systems do you know to test difficulty of intubation..
mallampati
thyromental and sternomental distance
wilson score - takes into account BMI, head and neck movement, jaw movmeent , receeding mandible and buck teeth - each scored on a three-point
scale (0-2). A total score of 2 or more is associated with an increased incidence of difficult intubation
how is a mallampati performed?
patient sits opposite the anaesthetist with their head in a neutral position,
the mouth open as wide as possible and the tongue protruded maximally
what are the predictors of difficult mask ventilation?
BMI >25
age >55
beard
dentures
history of OSA
facial abnormalites
clinical signs of tension pneumothorax
dyspnoea / respiratory distress
low sats
hypotension
tachycardia
why may stridor develop post thyroid surgery?
tracheal compression from haematoma
vocal cord paralysis - recurrent laryngeal nerve palsy
why may a patient become breathless post subclavian central line insertion?
higher risk of pneumothorax or haemothorax
what is a normal JVP?
less than 4cm above manubrium when sat at 45 degrees