Anaesthetics Flashcards
Positional manoeuvre to open airway:
- head tilt
- chin lift
- jaw thrust
What is an oropharyngeal airway used for?
- easy to insert and use
- no paralysis
- ideal for very short procedures
- often bridge to more definitive airway
What is a laryngeal mask used for?
- very easy
- sits on pharynx and aligns to cover airway
- poor control against reflux of gastric contents
- paralysis not required
- especially day surgery
- not suitable high pressure ventilation
What is a tracheostomy used for?
- reduces work of breathing
- useful in slow weaning
- percutaneous in ITU
- dries secretions, humidified air required
What is an endotracheal tube used for?
- optimal control of airway once cuff inflated
- short or long term
- errors in insertion may result in oesophageal intubation
- paralysis required
- higher ventilation pressures used
ASA I:
- normal healthy patient
- non-smoking, no/minimal alcohol use
ASA II:
- mild systemic disease
- e.g. current smoker, social drinker, pregnancy, obesity, well controlled diabetes/HTN, mild lung disease
ASA III:
- severe systemic disease
- substantial limitations
- poorly controlled diabetes, morbid obesity, hepatitis, alcohol abuse, pacemaker, ESRD, regular dialysis, MI, cerebrovascular
ASA IV:
- severe systemic disease that is constant threat to life
- e.g. recent MI, cerebrovascular, ongoing ischaemia of heart, valve dysfunction, sepsis, DIC, ARD, ESRD
ASA V:
- moribund patient not expected to survive without operation
- e.g. rupture aneurysm, massive trauma, ischaemic bowel, multiple organ dysfunction
ASA VI:
- brain dead
- organs being removed for donor purposes
How is propofol used as an anaesthetic agent?
- GABA receptor agonist
- rapid onset
- pain on IV injection
- rapidly metabolised with little metabolite accumulation
- anti emetic
- moderate myocardial depression
- maintaining sedation in ITU, total IV anaesthetic and daycare surgery
How is sodium thiopentone used as an anaesthetic agent?
- very rapid onset
- marked myocardial depression
- metabolites build quickly
- unsuitable for maintenance
- little analgesic
How is ketamine used as an anaesthetic agent?
- NMDA receptor antagonist
- induction of anaesthesia
- moderate to strong analgesic properties
- little myocardial depression so suitable for haemodynamically unstable
- dissociative anaesthesia resulting in nightmares
How is etomidate used as an anaesthetic agent?
- favourable cardiac safety profile - haemodynamic instability
- no analgesia
- unsuitable for maintaining sedation as prolonged use can cause adrenal suppression
- post operative vomiting is common
What to do if blood loss in surgery where transfusion is unlikely?
group and save
What to do if blood loss in surgery where transfusion is likely?
cross match 2 units
salpingectomy for ruptured ectopic pregnancy, total hip replacement
What to do if blood loss in surgery where transfusion is definite?
cross match 4-6 units
total gastrectomy, oophorectomy, oesophagectomy, elective AAA repair, cystectomy, hepatectomy
Inhaled anaesthetic:
- halothane
- ADR: hepatotoxicity, myocardial depression, malignant hyperthermia
What are peripheral venous cannulas unsuitable for?
- vasoactive drugs
- e.g. inotropes and irritant drugs e.g. TPN
- unless very short setting
How should central lines be inserted?
- using US
- femoral lines easier to insert but high infection rates
- internal jugular preferred - multiple lumens
How should intraosseous access be inserted and what is it used for?
- anteromedial aspect of proximal tibia
- access to marrow cavity and circulatory
- preferred in paediatric
- may be used in adults
What are tunnelled lines?
- Groshong and Hickman
- popular for long term therapeutic
- inserted using US into internal jugular vein and then tunnelled under skin
- can be linked to injection ports under skin
- popular in paediatric
What is a peripherally inserted central cannula?
- picc lines popular for central venous access
- inserted peripherally so less major complications than conventional central lines
Orange cannula size and flow rate:
- 14g
- 270ml/min
Grey cannula size and flow rate:
- 16g
- 180ml/min
Green cannula size and flow rate:
- 18g
- 80ml/min
Pink cannula size and flow rate:
- 20g
- 54ml/min
Blue cannula size and flow rate:
- 22g
- 33ml/min
What kind of drug is lidocaine?
- amide
- LA and anti arrhythmic
- affects sodium channels
- hepatic metabolism, protein bound, renal excreted
Lidocaine toxicity:
- due to IV or excess administration
- increased risk in liver dysfunction or low protein
- treat with IV 20% lipid emulsion
- initial CNS over activity and then depression
- blocks inhibitory pathways and then activating pathways as well
- cardiac arrhythmias
- increased doses combined with adrenaline
What does lidocaine interact with?
- beta blockers
- ciprofloxacin
- phenytoin
What kind of drug is cocaine and what is it used for?
- salt - cocaine hydrochloride
- LA paste
- 4 and 10% conc
- nasal mucosa -ENT
- vasoconstriction
- lipophilic so readily crosses BBB
- can cause arrhythmias and tachycardia
What kind of drug is bupivacaine:
- binds to intracellular portion of sodium channels and blocks sodium influx into nerves
- prevents depolarisation
- longer action than lidocaine
- topical wound infiltration at conclusion of surgical procedures
- cardiotoxic so contra in regional blockage
- levopbupivicaine less cardiotoxic and causes less vasodilation
What is prilocaine used for:
- less cardiotoxic
- intravenous regional anaesthesia
Dose of lignocaine plain and with adrenaline:
- 3mg/kg
- 7mg/kg
Dose of bupivacaine plain and with adrenaline:
- 2mg/kg
- 2mg/kg
Dose of prilocaine plain and with adrenaline:
- 6mg/kg
- 9mg/kg
Max dose lignocaine:
200mg
Max dose lignocaine:
500mg
Max dose bupivicaine:
150mg
What is malignant hyperthermia?
- often seen after anaesthetics
- hyperpyrexia and muscle rigidity
- excessive release of calcium from sarcoplasmic reticulum
- associated with defect chromosome 19 encoding ryan-done receptor
- autosomal dominant
Causative agents malignant hyperthermia:
- halothane
- suxamethonium
- antipsychotics (NMS)
Investigations and management malignant hyperthermia:
- CK raised
- contracture tests with halothane and caffeine
- manage with dantrolene - prevents calcium release from SR
When are nasopharyngeal airways used and contraindicated?
- decreased GCS
- ideal for seizures
- NOT in base skull fractures
What is suxamethonium?
- muscle relaxant
- depolarising neuromuscular blocker
- inhibits Ach at NM junction
- fastest onset and shortest duration
- generalised muscular contraction prior to paralysis
- ADR: hyperkalaemia, malignant hyperthermia, lack of acetylcholinesterase
What is atracurium?
- muscle relaxant
- non depolarising neuromuscular blocking drug
- 20-45 minutes action
- generalised histamine release on administration may produce facial flushing, tachycardia and hypotension
- not excreted by liver or kidney, broken down in tissue by hydrolysis
- reversed by neostigmine
What is vecuronium?
- muscle relaxant
- non depolarising neuromuscular blocking drug
- 30-40 minutes action
- degraded by liver and kidney and effects prolonged in organ dysfunction
- reversed by neostigmine
What is pancuronium?
- muscle relaxant
- non depolarising neuromuscular blocekr
- 2-3 minutes for onset
- duration 2 hours
- partially reversed with neostigmine
What are the depolarising and non-depolarising neuromuscular blocking drugs?
- depolarising: suxamehtonium (succinylcholine)
- non-depolairisng: tubocurarine, atracurium, veruconium, pancuronium
How do depolarising neuromuscular blocking drugs work and ADR?
- bind to nicotinic ach receptors so persistent depolarising of motor end plate
- ADR: malignant hyperthermia, hyperkalaemia
CONTRA of depolarising neuromuscular blocking drugs:
-penetrating eye injuries
-acute narrow angle glaucoma
(suxamethonium increases intra-ocular pressure)
How do non-depolarising neuromuscular blocking drugs work and ADR?
- competitive antagonist of nicotinic ach receptors
- ADR: hypotension
How do you reverse non-depolarising neuromuscular blocking drugs?
acetylcholinesterase inhibitors e.g. neostigmine
What is paralytic ileus?
- common complication after bowel surgery especially
- no peristalsis results in pseudo-obstruction
- also in association with chest infections, myocardial infarction, stroke and AKI
- deranged electrolytes can contribute
Early causes of post-op pyrexia (0-5 days):
- blood transfusion
- cellulitis
- UTI
- physiological systemic inflammatory reaction
- pulmonary atelectasis
Late causes of post-op pyrexia:
-VTE
pneumonia
-wound infection
-anastomotic leak
3 phases of operation on checklist:
- before induction of anaesthesia
- before incision of skin
- before patient leaves room
What needs to be checked before induction of anaesthesia?
- patient identify confirmed
- site marked
- anaesthesia safety check completed
- pulse oximeter on patient and functioning
- allergies
- any aspiration or airway risk
- risk of >500ml blood loss?
When should women stop taking the pill/hormone replacement before surgery?
4 weeks
What are the stages of wound healing?
- haemostasis
- inflammation
- regeneration
- remodeling
What is the haemostats stage of wound healing?
- minutes to hours after
- vasospasm in adjacent vessels, platelet plug formation and generation of fibrin rich clot
What is the inflammation stage of wound healing?
- days 1-5
- neutrophils migrate into wound
- growth factors released (basic fibroblast growth factor and VEGF)
- fibroblasts replicate within adjacent matrix and migrate into wound
- macrophages and fibroblasts couple matrix regeneration and clot substitution
What is the regeneration stage of wound healing?
- days 7-56
- platelet derived GF and transformation GF stimulate fibroblasts and epithelial cells
- fibroblasts produce collagen network
- angiogenesis occurs and wound resembles granulation tissue
What is the remodelling stage of wound healing?
- week 6-1 year
- longest phase of healing process may last up to 1 year
- fibroblasts differentiate (myofibroblasts) and these facilitate wound contraction
- collagen fibres remodelled
- microvessels regress leaving pale scar
What is a hypertrophic scar?
- excess collagen
- nodules with randomly arranged fibrils and parallel fibrils
What is a keloid scar?
- excess collagen in scar
- beyond boundaries of original injury
- no nodules
- do not regress over time and may recur following removal
Drugs impairing wound healing:
- NSAID
- steroid
- immunosuppressive
- anti-neoplastic
