General Anaesthesia Flashcards
Name the 2 broad groups and agents of iv induction agents (7)
• Barbiturates: sodium thiopentone
• non-barbiturates: propofol, etomidate, ketamine, benzodiazepines
Indications of sodium thiopentone (4)
Rapid (-30 seconds) induction but no analgesia.
Control convulsions in eclampsia and epilepsy
Electro-convulsive therapy
Sustained titrations in head injury patients who have raised ICP and are being ventilated in ICU
Best for emergency C/S that need GA (awake to stage 3 in 30s)
Name 6 effects sodium thiopentone has on the CNS
• most Rapid induction:one arm-brain circulation time, about 30 seconds (due to acidic nature, causing more unionised free fraction to cross BBB)
• sedation, hypnosis, anticonvulsant (analogue of phenobarbitrone )
• decreased intracranial pressure (vasoconstriction - decreased blood flow)
• cerebral oxygen consumption rate (CMRO2) decreased. Protect in focal ischaemia, not global
• analgesic in small dose
• decrease intraocular pressure
Name 2 effects sodium thiopentone has on the respiratory system
• Resp depression - hypoventilation. Apnoea 2-3 min
• excitatory effect on upper airway structures causing cough, hiccups laryngospasm, bronchospasm, especially when attempting to place airway devices
Name 2 effects sodium thiopentone has on the CVS
• Decreased cardiac output due to peripheral vasodilation and depression of contractility
• leading to hypotension especially in patients with fixed cardiac output
• intra-arterial and extravenous injection- never use stronger than 2.5%!
Name 2 effects sodium thiopentone has on the eyes
• Initially mydriasis then miosis
• decreased intra-ocular pressure
Name 1 effects sodium thiopentone has on the uterus
Crosses placental barrier shortly after iv induction
Hypoxia and acidosis fetus
Name 6 advantages of using sodium thiopentone for induction
• Pleasant, rapid induction <30 s
• absence delirious phase
• rapid recovery
• No nausea
• reliable
• Cheap
Name 5 side effects of sodium thiopentone
- Intra-arterial injection
- Respiratory depression (apnoea)
- Myocardial contractility depression (bradycardia.)
- Vasodilation (hypotension)
5-anaphylaxis type 1
Also local nerve damage, laryngospasm, bronchospasm, hiccups, cough,
Half life too long 8 hours
Name 4 absolute contraindications to sodium thiopentone
- Porphyria variegata (precipitate attack )
- Fixed cardiac output states eg constrictive pericarditis!
- Airway obstruction
4 severe shock
Adrenal insufficiency
Also previous allergy, endocrine diseases eg hypothyroid , Addison’s
Name 4 immediate signs of intra- arterial injection of sodium thiopentone
1 white hand
2. Intense burning pain
3. Areas of skin discolouration
4 - delayed induction (>30s)
Name 4 late signs of intra- arterial injection of sodium thiopentone
- oedema
- Blisters and ulceration
- Gangrene.
4 loss limb
How to treat intra-arterial injection of thiopentone? (6)
- Stop injecting and don’t remove cannula
- Flush with iv fluids to dilute STP
- Lignocaine to decrease burning
- NB prevention: iv heparin to prevent clotting of artery thrombosis
- Papaverine = antidote: vasodilation or
- Brachial plexus or stellate ganglion block (sympatholysis) (reduced vasoconstriction)
Name 6 effects of propofol on the CNS
- Mainly hypnotic (occur in 1 brain-arm circulation time) but no analgesia.
- Subhypnotic doses provide sedation and amnesia , anticonvulsant
- Hallucinations and opisthotonus!
- Decreased ICP
- Decrease cerebral perfusion pressure and CMRO2 (less than thiopentone )
- Lower intra ocular pressure
Name 2 resp effects of propofol
• Hypoventilation and apnea >30 s, greater than other induction agents. RR less for at least 2 min, minute volume lowered as long as 4 min.
• Decreased sensitivity of upper airway - decreased reflexes so can intubate with propofol use only. Best for LMA.
Name CVS effects of propofol (3)
• Decrease bp quite severely (due to decreased systemic vascular resistance , cardiac output and L ventricular stroke index) (block pressure sensors aortic arch)therefore
• decreased pre- and after-load (vasodilation and myocardial depression)
• decrease myocardial oxygen consumption and lower myocardial blood flow
Heart rate constant!
Cardiotoxic.
Name the advantages of using propofol (7)
• Ideal for TIVA :short elimination half life
• ideal agent for conscious sedation
• Good intubating conditions and early placement of laryngeal mask
• safe in malignant hyperthermia and porphyria ( not thiopentone ).
• pleasant induction
• pleasant recovery without nausea/hangover - antiemetic!
• anti-pruritic
• anxiolytic, amnesia
• erection?
Name 7 side effects of propofol
- Pain on injection (add opioid or lignocaine and use large vein with fast running drip ) (due to long chain fatty acids)
2.apnoea - Decreased bp
4 thrombophlebitis - Anaphylaxis
- Myoclonus, opisthotonos
- Propofol infusion syndrome PRIS (prolonged use)
Convulsions and delayed recovery have been reported but are controversial
Bacteria like to breed in it. Need to use within 6h of opening
Name the 7 CNS effects of etomidate
- Primarily hypnotic (1 arm-brain circ time), no analgesia
- Decrease intracranial pressure
- Decrease cerebral blood flow
4- lower CMRO2 - Cerebral perfusion pressure well maintained!
- High incidence myoclonic movements!
- EEG ass with grand mal epilepsy!
Name 4 respiratory effects of etomidate
- Post-induction brief period of hyperventilation! At times followed by apnea
- High incidence cough and hiccups! Before hypnosis
- Ventilator response to raised co2 diminished
- Safe in asthmatics as it doesn’t release histamine and cause bronchospasm (unlike thiopentone)
Name CVS effects of etomidate (3)
• No hypotension!
• No myocardial depression! Minimal increase in hr.
• myocardial oxygen supply/ demand ratio well maintained
Name endocrine effects of etomidate (2)
Inhibits synthesis of adrenal gland hormones
• decreased cortisol after single and cont infusion (careful in major trauma, sepsis etc that are dependent on stress hormones!)
• decreased mineralocorticoids (aldosterone) if used solely as induction agent
By 11 beta hydroxylase and 17 alpha inhibition. Lasts for 8 hours after single bolus. Vit c restore cortisol to normal levels.
Problem with TIVA and sole agent induction!
What is the induction agent of choice in healthy patients?
Propofol
What is the induction agent of choice in the poor risk cardiac patients?
Etomidate
Name advantages of using etomidate? (4)
• No CVS effects
• safe for asthmatics
• rapid induction
• rapid smooth recovery
Name side effects of etomidate (7)
• Severe pain on injection!
• Myoclonic movements!
• nausea and vomiting!
• adrenal hormones synthesis inhibition - may precipitate Addison’s crisis
• venous irritation or thrombophlebitis
• possible seizures
• expensive
Intra- arterial injection no pathology
Brand bewe braak bynier Baie duur
Which 2 benzodiazepines can be used for induction?
Diazepam and midazolam (better)
LorazePam most potent
Why are benzodiazepines not ideal for induction? (3)
• Big differences in individual metabolism between patients
• large doses needed for anaesthesia leading to prolonged effect
• active metabolites further prolong effects
Name 3 CNS effects of benzodiazepines
• Sedation, hypnosis, anxiolysis!, amnesia, central muscle relaxation
• Anti-convulsant
• lowers CMRO2 and cerebral blood flow (less brain protection than thiopentone)
Name resp effect of benzodiazepines
Dose dependent respiratory depression, exaggerated in COAD patients and elderly. Midazolam > diazepam. Later onset (after 3 min) and sustained for about 15 min, but apnea less common than other agents
Synergistic action when used with opiate
Name cardiovascular effect of benzodiazepines
None really, slight hypotension. Worse if add opioid. Good for cardiac patients
Name four side effects of benzodiazepines
- Inter-individual variation extreme
- Thrombophlebitis with diazepam and lorazepam
- Prolonged post-op amnesia, sedation, resp depression especially if combined with opioid.
- Synergism occurs with induction agents, opioids, sedatives in combination with benzos to give severe resp depression and hypotension.
What drug can be used to reverse the effects of benzodiazepines? (Especially respiratory depression)
Flumazenil (anexate) 0, 1 mg boluses
What, in simple terms, makes the moa of ketamine so different to the other induction agents?
Act on NMDA receptor in brain (ca channel blocker), not GABAa receptor (cl channel opener ). Cause dissociative anaesthesia (conscious but fully amnesic and insensitive to pain), cataleptic
Very large therapeutic index and can administer any route
Name the effects of ketamine on the CNS (7)
• Complete analgesia!
• increased cerebral metabolism
• increase CMRO 2
• increase cerebral blood flow
• increase ICP! And IOP
• Petite mal activity on EEG
• delirium/excitement phenomena post-op: hallucinations, dreams! Floating sensation etc
• cataleptic
• dissociation.
• nystagmus
Name respiratory effects ketamine (4)
• apnea only sometimes with very high doses
• very good bronchodilator (sympathomimetic)
• Reflexes eg cough, swallowing etc well maintained so no need for airway device - protect and can breathe spontaneously
• hyper salivation! May cause obstruction/silent aspiration; some may laryngospasm
• increased skeletal muscle tone
Blunt response to hypercarbia and hypoxia so keep an eye on it
Normal ventilator response to Co maintained
Name cardiovascular effects ketamine (3)
• Releases noradrenaline centrally causing hypertension, tachycardia, increased cardiac output but eventually cardiac depression once catecholamines stores are depleted!
• inhibit neuronal uptake of catecholamines and increase its release
• direct negative inotropic effects in vitro and directly once catecholamines depleted causing cardiac depression
Good for poor cardiac function patients or hypovolemic shock!
Name the benefits/ indications of ketamine (6)
• Sole agent in short procedures
• induction in poor risk patients: cardiac camponade or constrictive pericarditis
• emergencies
• analgesia
• asthma
• children minor procedures and with congen heart disease
Etc
Name contraindications of ketamine (6)
•Hypertension!
• myocardial ischaemia IHD
• increased ICP, TBI
• penetrating eye injuries
• psych patients
• aneurysms
• decreased catecholamines: cardiac depression
• epileptics
• decompensated shock
Which anaesthesia agents should be used for history post-op nausea and vomiting?
Propofol TIVA
Treatment of postoperative hypotension due to hypovolaemia? (4)
• Elevate legs
• iv volume expander
• vasoconstrictors: phenylephrine if tachycardia, ephedrine, etilephrine (effortil) if bradycardia.
Which opioid is both metabolised by the liver and excreted by the kidneys?
Morphine
Which is the only opioid not metabolised by the liver? What metabolised by?
Remifentanil
(Metabolised by red cell esterases. Doesn’t accumulate in body ).
Which opioid has the shortest duration of action?
Remifentanil = ultra short acting (then alfentanil)
Which opioid has the longest duration of action?
Morphine (then fentanyl )
What are the effects of opioid on CVS?
Decrease sympathetic activity can cause bradycardia and hypotension, but very little
What are the effects of opioid on respiratory? ( 3)
• Hypoventilation (decrease hypoxic drive, decrease sensitivity of brain stem to Pa CO2 ) - apnoea! (Mu receptor)
• chest wall rigidity (centrally mediated muscle contraction)
• blunts airway reflexes - bronchospasm (histamine release)
What are the effects of opioid on CNS? (6)
• miosis (overdose- pin point pupils)
• nausea and vomiting! (Stim chemoreceptor trigger zone)
• slow waves on EEG in high doses
• Reduce CMRO 2 (central depressant) (sedative)
• reduce cerebral blood flow
• decrease ICP
Tolerance
Analgesic, can sometimes cause Hyperalgesia
What are the effects of opioid on git? (4)
• Decrease gastric emptying
• spasm of sphincter of Oddi (pain)
• Constipation and ileus
• nausea and vomiting
What are the effects of opioid on endocrine?
Decrease stress hormones
What are the effects of opioid on miscellaneous (4)?
- addiction potential
- Tolerance
- Pruritis
- Histamine release (morphine)
Urinary retention
Miosis
What drug reverses the side effects of opioids? Dose
Naloxone 5 ug/kg nitrated to effect IM
Used mostly for opioid induced apnoea but also reverse analgesia so remember to give alternative analgesic
Uses Mgso4 in theatre (4)
• Pain treatment (calaum antag . )
• blunt somatic, autonomic, endocrine reflexes provoked by noxious stimuli
• vasodilation for hypertension?
• prevention and treatment eclampsia
Name the 8 phases and steps of general anaesthetic administration
- Pre-op evaluation and medication
- Preparation equipment and drugs
- Iv access
- Induction of unconsciousness
- Manage airway
- Maintenance anaesthesia
- Wake up and reversal muscle relaxation (NDMR)
- Observe and support in PACU
Name 6 signs inadequate anaesthesia
•Tachycardia/dysrhythmias
• hypertension
• sweating or salivation or tears
• movement if not relaxed
• dilation pupils
• increased breathing efforts if not paralysed
Name 3 patient factors that prolong arm-brain circulation time
• Decreased cardiac output
• old age
. Hypothermia
Therefore inject slowly and wait for effect.
Name the order of distribution in bodyof iv induction agent-s
• vessel rich group; brain, heart, kidney, liver
• muscle
• fat
• bone
Which induction agent is not highly protein bound?
Ketamine 12% (
Rest 75%
How identify sodium thiopentone?
Yellow powder, garlic smell, bitter taste
How prepare sodium thiopental?
Add 20 ml fluid to powder ampule to give 2,5% 25 mg /ml
Name 2 factors that will influence the dose of thiopentone given
•Acidosis: give less
. Hypoproteinemia: give less
Name 3 relative contraindications to sodium thiopentone
• Atopic asthma
• severe liver disease, anaemia
• myxoedema
Name 6 features propofol infusion syndrome
- Sudden onset marked bradycardia / total heart block resistant to treatment
- Lipaemic plasma
- Hepatomegaly
- Metabolic acidosis (base deficit >10 )
- Rhabdomyolysis, myoglobinuria
- Multi organ failure
Pathogenesis propofol infusion syndrome (6)
• Blockade l-cat
• therefore decreased FFA transfer to cells
• decreased mitochondrial oxygen utilisation
• decreased fatty acid beta oxidation
. Decreased ATP production (run out of energy)
• increased FFA in blood
Treatment propofol infusion syndrome? (3)
• Prevention: keep infusion <4 mg/kg /h and not longer than 24h
• dialysis/plasmapheresis
• pacemaker
Dexmedetomidine moa?
Highly selective alpha 2 agonist
Used as infusion induction
Name 4 advantages dexmedetomidine
• Little respiratory depression!
• sedation, but not severe so can mobilise early. (Main Indic, alpha 2 agonist)
• analgesia
• anti-shivering
Anxiolysis
Name 2 disadvantages dexmedetomidine
• Biphasic blood pressure response
• severe hypotension later, dose dependent
Name 6 drugs that cause delayed awakening
• Benzodiazepine premedication
• opioid overdose intra-op
• Insufficient reversal nondepolarising muscle relaxants!
• suxamethonium apnoea!
• Failure to discontinue anaesthetic vapour!
• pre-operative alcohol intoxication
Name 4 endocrine causes of delayed awakening
• severe hypothyroidism!
• hypoglycaemia
• DKA, honk
. Addison’s crisis
Name 3 electrolyte causes of delayed awakening
• Hyponatraemia!
• hypo or hyper? Ca!
• hyper mg (mGs04 treatment eg)!
Name 2 acid base causes of delayed awakening
• Hypercapnoea (“Carbon dioxide narcosis”) due to hypoventilation
• hypocapnoea (no drive for breathing) due to hyperventilation
Name 2 intra-operative complication causes of delayed awakening
• Cerebro-vascular incident
• mi
Which agent is a phencyclidine derivative?
Ketamine
Which induction agent is contraindicated in soy allergy?
Propofol
Preferred induction agent in concious patient with heart stab wound to RV?
Ketamine
Induction agent of choice for gross hypovolaemia?
Ketamine because stimulate SNS
Which anaesthetic agent is an imidazole derivative?
Etomidate
Anaesthetics suppress CNS in which order? (4)
- Cortex
- Basal ganglia
- Spinal cord
- Medulla oblongata
Name 3 anaesthetic agents that release noradrenaline
- cocaine
- ketamine
- ephedrine
Name 6 relative contraindications to sodium thiopental
• Status asthmaticus
• hypovolaemia
• severe anaemia/liver/ renal disease
• dystrophica myotonia-prolonged apnea
• myasthenia gravis
• myxoedema
Induction doses propofol? (3)
• premedicated: 1,5-2,5 mg/ kg
• un premedicated: 2,25-2,5 mg/ kg
• age >60:1-1,75 mg/ kg
Maintenance dose propofol?
6-12 mg/kg/h
Name a contraindication to benzo for induction
Myasthenia graves
Name 5 cautions to take in induction with benzo
• Elderly
• debilitated
• with other cns depressants
• renal and liver disease
• pregnancy
Iv induction dose ketamine?
1-2 mg/kg
IM induction dose ketamine?
2-5 mg/kg
Po/pr induction dose ketamine?
6-10 mg/kg
What kind of opioid receptors are found in brain?
Mu opioid peptide receptor
What kind of opioid receptors are found in spinal cord?
Delta opioid peptide receptor
What kind of opioid receptors are found in git?
Kappa opioid peptide receptor
What kind of opioid receptors are found in joints?
Nociceptin orphanin fq peptide receptor
Iv Dose morphine?
Load 0,05-0,1 mg /kg then regular small maintenance doses or infusion. Every 4 hours!
IM dose morphine?
10-15 mg 4 hourly
Name 5 things kept in fridge in anaesthesia
• Oxytocin
• ice pack
•Insulin
• non-depolarising muscle relaxants: atracurium, cisatracurium, pancuronium, rocaronium
• red cell concentrate stored in fridge
What does weight of N2O cylinder depend on?
Critical temperature
