Anaesthetics Flashcards
Basic techniques to stabilise an airway (2)
Head tilt chin lift
Jaw thrust
% of O2 in 15L via NRBM/Reservoir mask
85%
Indication for an airway adjunct
Airway patent on manoeuvre but stops when not
How do you measure the size of Oropharyngeal airway needed
Angle of mandible to incisors
CI for Oropharyngeal airway
Conscious
Gag reflex
Indication for Nasopharyngeal airway
Cannot tolerate OPA because they are conscious
CI for NPA
Basal skull fracture (Panda eyes and Battle’s sign)
How do you measure the length of the NPA an individual requires
Tragus to incisor
Size of NPA for males and females?
M= 7
F=6
Nasal cannulae oxygen delivery?
1-6L/Min
Max 40% O2
Hudson mask/simple face mask oxygen delivery?
5-10L
Venturi mask advantage?
Controlled amount of 02 delivery
O2 delivery from a venturi mask in increasing order
Blue= V24= 2-4L/min White= V28= 4-6L/min Yellow= V35= 8-10L/Min Red= V40= 10-12L/Min Green=V60= 12-15L/Min
(Vx= % O2 delivered)
When using the bag-valve mask how many breaths per min and how hard do you squeeze it?
12/min
1/3rd volume of the bag
Requirements for NIV?
Alert Conscious Co-operative Cough Can maintain own airway Own resp effort is good
Indication for CPAP
Acute hypoxic respiratory failure
Indications for BIPAP
Hypercapnic COPD exacerbation
Size of LMA in males and females
Male= 4 Female= 3
If not anaesthetist is present what airway is 1st line in a cardiac arrest
LMA
ET tube them if anaesthetist is present
ET tube size in Males and Females
M= 9 +/- 0.5 F= 8 +/- 0.5
Where do the two black lines go when the ET tube is inserted
On either side of the vocal cords
How do you hold a laryngoscope and where does it go?
Left hand
Valecular
(use chin lift)
How do you confirm the position of an ET tube?
Capnograph- CO2 in expiration Auscultate over lungs- Apices and bases +/- Stomach Direct visualisation Misting in tube Symmetrical chest movement \+/- Sats rising
Early and late complications of an ET tube
Early- Trauma, aspiration, airway obstruction, hypoxia if prolonged attempts
Late- Infection, mucosal damage, vocal cord injury
Tracheal stenosis
Indications for a tracheostomy
Emergency access Upper airway obstruction Impaired resp function E.G Head trauma Assist in ventilation weaning Long term ventilation
Indications for a cricothyroidotomy
Emergency airway
Obstruction at or above larynx
Process of anaesthesia (6 steps)
Pre-op assessment
IV access/Monitoring (14G-24G)
Induction
Analgesia + muscle relaxation
Maintain AMNESIA, AKINESIS AND ANALGESIA
Reversal
How is amnesia achieved
Induction agent lasting 4-10 mins
Maintained via inhalation/volatile agents
Advantages and disadvantages to Propofol
+ Suppresses airway reflexes
+ Decreased PONV
- Involuntary movements
- Marked reduction in HR & BP
- Pain upon injection
What is propafol
Induction agent to induce amnesia
lipid based therefore white emulsion
1.5-2.5 mg/kg
What is thiopentone
Barbituate used to induce amnesia
4-5mg/kg
Used for RSI
Advantages and disadvantages to thiopentone
+ RSI (FAST ONSET)
+ Anti-epileptic so protects the brain
- BP decrease with HR increase
- Rash
- Bronchospasm
- CI in porphyria
- Thrombosis and gangrene if intra-arterial as blocks arterioles
When is Ketamine used as an induction agent
What form of amnesia does it cause?
Good as sole anaesthetic for short procedures E.G burn dressing change
1-1.5 mg/kg
Dissociative= Profound analgesia and anterograde amnesia
Advantages and disadvantages to Ketamine
+ Slow onset (90s)
+ Increase in HR & BP
+ Bronchodilatation
- N&V
- Emergence phenomenon- vivid dreams and hallucinations
What is Etomidate
Steroid based induction agent
Rapid onset
Use if you want to minimise haemodynamic instability
Advantages and disadvantages to etomidate
+Haemodynamic stability
+ No impact on BP
+ Lowest hypersensitivity risk
- Pain upon injection
- High incidence of PONV
- Spontaneous movements
- Adreno-cortico suppression
What 2 methods are used to maintain amnesia?
Total IV anaesthesia- Propofol infusion via IV + Fentanyl
Inhalation anaesthesia using an inhalation agent
Inhalation agents- Benefits of Isoflurane
Lowest impact on organ blood flow
Good if an organ donor!
Inhalation agents- Benefits of Sevoflurane
Sweet smelling
Good for children
Inhalation induction
Inhalation agents- Benefits of Desflurane
Rapid onset and offset- Does not accumulate in fat!
Good for long operations
What is the minimum alveolar concentration
Concentration of vapour that prevents reaction to a set depth and width of skin incision in 50% of patients
BUT provides amnesia in 100%
MAC of: Nitrous oxide Sevoflurane Isoflurane Desflurane Enflurane
Nitrous oxide- 104% Sevoflurane- 2% Isoflurane- 1.15% Desflurane- 6% Enflurane- 1.6%
When are short acting analgesics used?
Give examples of them.
Intra-operatively, suppress response to layrngoscope, surgical pain
Remifentanil, Alfentanil, Fentanyl
Of Remifentanil, Alfentanil and Fentanyl which is most potent with the fastest onset?
Which can be given IV?
Remifentanil> Alfentanil>Fentanyl
Remifentanil- IV
Which NSAIDS can be given IV
Parecoxib
Ketorolac
In a surgical setting when should morphine/Oxycodone be given?
Intra- or Post-operatively
If the former then give 15-20 mins before the end of the operation
Give examples of short,Int and long acting non-depolarising muscle relaxants
Short- Atracurium, Mivacurium (30 mins)
Int- Rocuronium, Vecuronium (30-60 mins)
Long- Pancuronium (60+ mins)
Mechanism of action and Properties of non-depolarising muscle relaxants
Blocks Nicotinic R preventing depolarisation by Ach
Slow onset, variable duration, fewer side effects
Mechanism of action of depolarising muscle relaxants
Mimic Ach so bind nicotinic receptors inducing a contraction/fasiculations (PHASE 1)
Desensitisation to the efffcts of Ach with muscle fatigue and relaxation
What is Suxamethonium
A non-depolarising muscle relaxant
1-1.5 kg/mg
Quick onset and offset (use in RSI)
Suxamethonium Side effects?
Fasiculations, Pain, HYPERkalaemia, Prolonged apnoea
Inc ICP/IOP/Gastric pressure
Malignant hyperthermia
How do you reverse suxamethonium related malignant hyperthermia
Dantrolene
What reversal agent potentiates the action of Suxamethonium
Neostigmine
What is neostigmine?
What must it be given with?
Anti-cholinesterase so prevents Ach breakdown to can reverse the action of non-depolarising muscle relaxants
Add an anti-muscarinic like glycopyrolate to prevent bradycardia
Drawbacks of neostigmine
N&V, cannot reverse profound block, slow onset and peak at 7-11 mins
What is sugammadex?
Causes water soluble complex formation to immediately reverse the effects of a muscle relaxant
Nil effect on nicotinic receptors
16 mg/kg if wanting immediate reversal
Drawbacks of sugammadex
Hypotension
Airway compromise if lower dose
VERY EXPENSIVE SO ONLY USE WHEN NECESSARY
What is Ephedrine
Inotropic agent acting on alpha and beta receptors
Increases both HR and BP
What is phenylephrine?
Inotropic agent acting directly on alpha receptors
Increase in BP (B/C VASOCONSTRICTION)
Decrease in HR
What is metaraminol?
Inotropic agent mixed direct/indirect action mostly on alpha receptors
Increase in BP (B/C vasoconstriction)
Decrease in HR
Inotropic agents used in ICU/Sepsis
NorA, Adrn, Dobutamine
What % of GA patients will vomit?
20-30% without medication
When would you give sodium citrate/H2 antagonist (antacid)
Aspiration risk E.G in Obstetrics/Obese/GORD/Difficult airway
Process of anaesthetic reversal
Stop vapours
Give O2
Throat suction
Reverse muscle relaxation
What are the two types of LA?
Esters- lipid soluble hydrophobic aromatic group (Procaine, Benzocaine, amethocaine, cocaine)
Amides- Charged hydrophilic group (Ropivacaine, Prilocaine, Levobupivacaine) REMEMBER BY HAVING 2 ‘i’ in their name
Max dose of Lignocaine
3
7 with adrenaline
Max dose of Bupivacaine/Levobupivacaine
2 (no change with adrenaline)
Max dose of Prilocaine
6
9 with adrenaline
When should you not use adrenaline
On terminal regions like the penis or digits
What is LA toxicity? Describe the presentation.
Exceeding max safe dose leading to Na+ channel blockage in the brain and heart
Confusion/Drowsiness/Coma/Convulsions/Light headedness/slurring of speech Tingling around mouth Excitatory symptoms Muscle twitching CV toxicity
How does LA toxicity impact the CV system?
Initial Tchycardia + HTN
Later hypotension and bradycardia
Leading to heart block and ventricular arrhythmias
Treatment of LA assoicated cardiac arrest
Intralipid 1.5 mls/kg
Keep doing CPR for 1 hour as intralipid takes a while to work
Iv Benzo if convulsing
Atropine if bradycardia persists + raise legs to treat hypotension
Steps to working out safe dose of LA
Work out max dose of drug in mg by multiplying max dose (mg/kg) by weight (kg)
Convert % of drug into mg/ml by multiplying by 10 (0.25%= 2.5mg/ml)
Divide Max dose (mg) by aforementioned how much mg/ml can be used (mg/ml)
Final figure in Ml
Where does the SC end?
Lower border of L1
Where does the SA space end?
S1
Where does the epidural space end?
Sacrococcygeal hiatus
Where does a spinal block inject into
Subarachnoid space
Where does an epidural inject into
Epidural space
Where can you do a spinal block?
L2 to S2
The lower the safer!
Harder past L5
Where can you do an epidural block?
Any level;
Risk SC damage if above L1
Benefits of Spinal/epidural over opiate analgesia
Fewer post-op respiratory complications Less PONV No precipitation of obstructive sleep apnoea Less chance of infection Decreased CV/Resp impact
How do you test for spinal onset?
Cold spray
Ice cube
Describe a spinal block
5-10 min onset Lasts 2-3 hours
RAPID ACTION
Dense motor block
Describe an epidural
LA +/- Opioid
10-15 min onset (Slower than spinal)
lasts up to 72 hours
Catheter can provide continuous infusion
CI for spinal/epidural
Increased ICP (coning risk)
Aortic/Mitral stenosis
Sepsis
Coagulopathy
Ways in which pain can be classified
Duration
Cause
Mechanism- Nociceptive vs neuropathic
Perception
What is nociceptive pain
Obvious tissue injury
Well localised
Dull if visceral
Sharp if muscles/bones/skin
What is neuropathic pain
Nervous system damage/abnormality
No protective function
Poorly localised
Neuro symptoms
Are alpha delta or C nerves faster?
Alpha delta- Faster sharp pain
C nerves- Persistent pain (Burning)
How do you treat acute nociceptive pain
Reverse WHO ladder
Trauma or Post-op!
Step down as pain improves
Key pain Q
How long
Cause
Pain mechanism
What is clonidine?
Alpha agonist.
Works centrally to ameliorate pain
Decreases BP
Sedative effect
Minimum recommended fasting time for:
Solids
Milk
breast fed infants
Solids- 6 hours
Milk- 6 hours
breast fed infants- 4 hours
Minimum recommended fasting time for:
Clear fluids
Alcohol
Boiled sweets/chewing gum
Clear fluids- 2 hours
Alcohol- At least 24 hours
Boiled sweets/chewing gum- Avoid but carry on with surgery
What is the lowest ml of fluid associated with morbidity in surgery
30ml
Impact of prolonged fasting
Headache, Anxiety, N&V, Dehydration, Hypotension, Metabolic disturbance
Factors impacting gastric emptying
Diabetes, CKD, Pyloric stenosis, Pregnancy, Obesity, Head trauma
Up to what time are children allowed H20 before surgery
1 hour before
Rapid sequence induction- indication
Full stomach
Use cuffed ET tube
RSI 3 phases
1) Preoxygenation with 3 mins tight fitting face mask or 5 full VC breaths
2) Induction with thiopentone or propofol + Recuronium or suxamethonium
3) Cricothyroid pressure + no ventilation (gentle if desaturate) + remove once ET tube in
Side effects of GA
Sore throat, tissue damage, confusion memory loss
Infection is uncommon as is teeth damage.
Eye damage is rare
Phases to pre-op assessment
Introduction/Details Previous anaesthetic Hx Exercise tolerance General health CVS/Resp/GI- Inc DM/Neuro/MSK/Dental DHx SHx FHx- Problems with anaesthetic Fasting check- clear fluids oly 6 hrs before then NBM 2 hours before Examination and Mallampati score
ASA grading
1- Healthy 2- Mild-mod sys disease with no limitation 3- Severe sys disease with limitation 4- Constant threat to life 5- Not expected to survive
Pre-op investigations if:
>80
60-80
<60
> 80- FBC, U&Es, ECG
60-80- SG>3 get all above, FBC only if SG2
<60- SG>3 get FBC (+U&Es if SG>4)
Surgical grades 1-4
1- Minor (Skin excision)
2- Intermediate (Tonsillectomy)
3- Major (Hysterectomy)
4- Major + (Joint replacement, thoracic)
RF for post-op N&V
Young. Female. Anxious. Etomidate. No2. Opiates. Volatile agents. Abd surgery
Treating intra-operative N&V
Ondansetron or Dex
Treating recovery N&V
Ondansetron is generally considered to be 1st line
Dexamethasone, cylizine, prochlorperazine are all alternatives
Post op fluid aims
Replace loss and achieve optimum SV/CO
What factors impact the speed of LA
Baricity, conc, volume, level of injection, speed of injection
CEPOD examples for Immediate Urgent Scheduled Elective
Immediate- life/organ saving, resus, AAA, fasciotomy
Urgent- 6 hours- Potentially life threatening, hours available for resus
Scheduled- 24-58 hours- Not an immediate threat to life (Tumour excision that if left could bleed)
Elective- Planned to suit patient
Order of process for GA + Intubation
Oxygenation Opioid Induction Volatile agent Bag-mask Muscle relaxant ET intubation
Order of process for GA + LMA
Oxygenation Opioid Induction Volatile agent Bag-mask LMA insertion
What is high frequency USS?
7-18Hz
Poor depth
Linear probe
SUPERFICIAL STRUCTURES
What is low frequency USS?
2-6Hz
Curvilinear probe
DEEP STRUCTURES
What primarily generates resolution on an USS?
Frequency
How and why do you adjust depth on an USS?
Want subject in the centre
so start with high depth and then adjust
How and why do you adjust gain on an USS?
Artificial multiplication of a structure
Better able to see deeper structures
Blood moving away is generally what colour on a doppler USS?
Blue
Blood moving towards is generally what colour on a doppler USS?
Red
What is a FAST scan?
Focussed Assessment Sonography for Trauma
Detects fluid/bleeding
Low specificity to cannot rule in
Misses retroperitoneal bleeds
Mallampati scores
1->4
What score signifies a difficult intubation?
1- See everything
2- See whole uvula (cannot see ant/post pillars completely)
3- Only uvula base
4- Soft palate not visible
3&4= Difficult intubation
What are your goals for treating shock?
Normalise lactate UO>0.5 MAP>65 Central venous oxygen sats >70% CVP 8-12 mmHg
Examples of vasopressors
Noradrenaline, Phenylephrine, Vasopressin, Metarminor
Examples of inotropes
Adrenaline, Dobutamine, Isoprenaline, Ephridine
When would you use Noradrenaline in shock?
Low CO
Septic shock
In what type of shock are vasopressors like NA, Vasopressin, phenylephrine indicated
Distributive
In what type of shock are inotropic agents like dobutamine indicated
Cardiogenic
What does CVP inform you of?
Fluid status, look at trend post-fluid
Key signs of shock
What compensatory signs may be seen
Hypotension (NOT ESSENTIAL…)
High lactate (>3)
BE
A bounding pulse can be a sign of what type of shock
Distributive
What is Beck’s triad?
Tamponade
Hypotension, Inc JVP, Pul oedema, Faint heart sounds
Describe obstructive shock
Afterload problem (Outflow block) PE, Tamponade, Pneumothorax, Fluid overload
Poor prognostic signs in hypovolaemic shock
BP<90 Low GCS Mottled Unresponsive to fluid Ongoing bleed
What are the 4 types of shock
Hypovolaemic
Cardiogenic
Obstructive
Distributive
Levels of care 0-3
0- Normal ward
1- Inc deterioration risk (CC Outreach)
2- Single failing organ system/Major burns
3- ICU (MULTI-ORGAN FAILURE)
If a patient comes to ICU their clinical state must be…
Potentially reversible
Long term health means patient can benefit from intensive care
How do you assess volume status
UO HR inc albumin inc urea (if dehydrated) Haematocrit (inc if dehydrated) creatinine Skin turgor BP
What is the 4, 2, 1 rule for fluid maintenance?
4ml/kg/hr for 1st 10kg Wx
2ml/kg/hr for next 10kg
1,l/kg/hr for remaining ideal Wx
Most adults 20-30ml/kg/hr
On an echo what does the IVC size suggest about the type of shock?
Small IVC- Hypovolaemia
Dilated IVC- Decreased contractility, so likley cardiogenic
Loss of normal structure= Tamponade? Obstructive shock
Parasternal echo veiw shows…
Transverese of long axis view
Apical echo view shows…
4 chambers
Subcostal echo view shows…
IVC- N.B. Should collapse <50% on insp)
Can also have a 4 chamber view
What is T1RF?
Hypoxaemia because V/Q Mismatch
Pneumonia, asthma, COPD, pneumothorax, ARDS, CHD, Bronchiectasis, Pul. HTN
What is T2RF?
Hypoxaemia and Hypercapnia due to ventilatory failure
Neuromuscular- Flail chest COPD/ASTHMA when severe and tired Oedema Loss of Resp drive Hypoventilation Trauma
What is the pathophysiology of ARDS?
Lung damage secondary to severe systemic illness
Induces a rise in inflammatory mediators
Increases cap permeability, Non-cardiogenic pul.oedema, Multi organ failure
What is Fi02?
Fraction of inspired oxygen
Helps to contextualise hypoxia
What is the main indicator for oxygen?
Hypoxaemia NOT BREATHLESSNESS
What does CPAP do to the airways?
Splints them open to improve FRC
Net effect to ameliorate V/Q mismatch
Type of respiratory failure where CPAP is used?
T1RF
How does BIPAP work?
CPAP + additional pressure to support ventilation
Increasing TV
Type of respiratory failure where BIPAP is used?
Hypercapnic COPD exacerbations
MSK conditions where there is respiratory failure
HELPS VENTILATION
Problems with ET tubes and sedation
Hypotension
Gastroparesis
Immobility
Pneumonia risk
Signs of increased ICP
Pupillary dilatation
Sluggish then fixed pupillary reflexes
Aphasia
Reduced consciousness/GCS
How do you manage increased ICP in ICU?
Avoid pyrexia Prevent seizures Elevate head to 30 degrees Sedation Ameliorate hypoxia and hypercapnia Hypertonic saline Mannitol (Inc blood osmolarity) Decompressive craniotomy
What is a poor prognostic sign on CT after brain injury?
Loss of differentiation
Looks hazy grey
Secondary brain injury precipitated by…
Hypoxia
Hypoperfusion
Hypoglycaemia
What does renal failure indicate about end organ perfusion in a critical care context?
Poor end organ perfusion
Look for anuria and increased serum creatinine
Complications of renal failure?
Uraemia- Encephalopathy, Pericarditis, Coagulopathy
Fluid overload
Metabolic acidosis
Hyperkalaemia
5 major principles of the MCA?
Presumption of capacity Support to make own decisions Able to make an unwise decision Best interests checklist if no capacity Least restrictive option that infringes on freedom least
Principles of capacity
Understand, Retain, Weigh up, Communicate
What is futility?
Low treatment efficacy
Physiological (Quantitative/Qualitative) or cost-based
What is death?
Irreversible loss of capacity for breathing and consciousness
How do you confirm brainstem death?
Continuous loss of Cardio-resp function for 5 minutes
Pupils, Supra-orbital pressure, corneal reflex
May still have beating heart…
Deceased donors must be Dx by how many consultants?
The death must be what?
3
Also must be on ventilator
Predictable and controlled death!
Process of organ donation in brainstem death
Test to confirm death > optimise physiology > Mobilise team > Organ retrieval
TAKEN TO THEATRE ONCE RETRIEVAL TEAM HAS ARRIVED
Process of organ donation in circulatory death
Mobilise team > Stop support> Death within time constraint> Dx death > Organ retrieval
Potential for stand down therefore not definitely going to theatre like in brainstem death, plus team is mobilised earlier