IV and inhalational anaesthetics Flashcards
What drug is used for induction and maintenance using IV drugs alone?
Propofol
Which drug has:
- anti-emetic properties?
- what is it used for?
Propofol
- anti-emetic properties
- used for maintaining sedation on ITU, total IV anaesthesia, day case surgery
Which agent has a rapid sequence of induction?
- what are the disadvantages?
Sodium thiopentone
- marked myocardial depression
- metabolites accumulate quickly
- little analgesic effect
- unsuitable for a maintenance
Ketamine
- what is it used for?
- what are its advantages?
- what is its disadvantage?
Ketamine
Use: may be used as induction
Advantages:
- has moderate - strong analgesic properties
- produces little myocardial depression (useful in haemodynamically unstable patients)
Disadvantage:
- may produce dissociative anaesthesia -> nightmares, hallucinations, agitation (as a drug wears off)
Etomidate
- advantage (1)
- disadvantages (3)
Etomidate
Advantage: has a good cardiac profile (very little haemodynamic instability)
Disadvantages:
- no analgesic properties
- may result in adrenal suppression (even short use) -> therefore not used for maintenance
- post-op vomiting is common
Components of checklist before introduction of anaesthesia (7)
Before the induction of anaesthesia, the following must have been checked:
- Patient has confirmed: Site, identity, procedure, consent
- Site is marked
- Anaesthesia safety check completed
- Pulse oximeter is on patient and functioning
- Does the patient have a known allergy?
- Is there a difficult airway/aspiration risk?
- Is there a risk of > 500ml blood loss (7ml/kg in children)?
Mechanism of action of propofol
Not yet fully understood, thought to act on GABAA receptors and sodium channels on the reticular formation
What allergies predispose the patient to anaphylactic reaction with propofol use?
Egg and soy -> as propofol is mixed with the substances containing these components (poor solubility in the water)
Propofol infusion syndrome
- cause
- clinical features
- management
Propofol infusion syndrome
Etiology: high doses and prolonged administration of propofol
Clinical features: severe metabolic acidosis, rhabdomyolysis, renal failure, and/or cardiac failure (often fatal)
Management: discontinue propofol immediately, symptomatic treatment (catecholamines, fluid resuscitation)
Mechanism of action of Etomidate
Etomidate
MoA: GABA receptors in reticular formation
What’s Etomidate good for? Why?
Etomidate
It has the least effect on CVS (it does not cause depression of the myocardium)
* therefore used in anaesthesia of the patients with myocardial instability
Mechanism of action of Ketamine
Ketamine
MoA: NMDA receptor antagonist (type of glutamate receptor)
What’s the advantage of Ketamine over other anaesthetics in an emergency setting?
- it can be administrated IM (apart from IV) -> so if IV access is difficult we still can give it
- good for polytrauma and hypotensive patients -> it does not induce CV depression
What type of procedure Ketamine is good for?
What is other use of Ketamine (aside from surgeries)?
Ketamine
- short and painful procedures e.g. fracture reduction
*Ketamine used in treatment of resistant asthma
Mechanism of action of barbiturates
Barbiturates
MoA: enhance GABA action -> via increased duration of Cl channels opening -> hyperpolarisation of post-sympathetic neurones -> reduced neural excitability
What’s disadvantage of barbiturate use?
They are highly lipid soluble -> have high potency with narrow therapeutic index
Rapid onset of action and recovery
Examples of barbiturates (name few)
- thiopental
- phenobarbital
- pentobarbital
- secobarbital
- methohexital
Side effects of barbiturates
- Hypotension (dose-dependent)
- Respiratory depression and/or apnea (dose-dependent)
- Laryngospasm, bronchospasm (histamine release)
- Myoclonus
- Painful injection
- Dependence
- Cytochrome P450 induction
- Contraindicated in porphyria
Indications for barbiturate use
- Short, painful procedures (e.g., pentobarbital or secobarbital for sedation during fracture reduction)
- Desired reduction of intracranial pressure (e.g., thiopental for brain edema following trauma or surgery)
- Sedation for electroconvulsive therapy (e.g., methohexital)
- Status epilepticus (e.g., phenobarbital)
Barbiturate overdose
- clinical features
- management
Barbiturate overdose
Clinical features: impaired consciousness, coma, respiratory failure, cardiovascular depression
Management
- Secure airways, oxygenation, monitoring
- fluid resuscitation
- ECG: monitor for arrhythmia
- ABG: monitor for metabolic acidosis, ↑ levels of serum lactic acid
- Measure the alcohol and barbiturate levels in serum in cases of suspected alcohol intoxication
- Antidote: sodium bicarbonate (NaHCO3
What are inhalational anaesthetics used for?
- induction and maintenance of general analgesia
- sedation
- What are the three most commonly used inhalational anaesthetics?
- Which one of these is MOST COMMONLY used?
Sevoflurane is the most commonly used -> due to its rapid onset of action and also patient recover quickly from it
Which one of the inhaled GA is the most commonly used?
Sevoflurane is the most commonly used -> due to its rapid onset of action and also patient recover quickly from it
What are the physiological effects of the use of inhalational anaesthetics?
- respiratory depression
- decrease in arterial blood pressure
- decrease in cerebral metabolic demand
- increase in cerebral blood flow
What is the disadvantage of the use of inhalational anaesthetics?
They do not provide post-op pain relief
How do inhalational anaesthetics are taken up into the blood?
Passively, via diffusion
How are inhalational anaesthetics eliminated?
They are eliminated via the lungs
Can Nitrous Oxide be administrated on its own?
- Nitrous oxide is not effective on its own
- it would be often administrated with another inhalational anaesthetic
Nitrous oxide increases the speed of onset of action of the other anaesthetic
Sevoflurane
- advantages
Sevoflurane is the most commonly used inhalational anaesthetic
- rapid onset of action -> narcosis can be achieved within one minute
- rapid onset of recovery
- good for induction
*also can be given via mask -> very good for paediatric surgery
General side effects of inhalational anaesthetics
General side effects
- Nausea/vomiting → inhalational anesthetics are contraindicated in patients who are not sober
- Risk of malignant hyperthermia
- Postoperative shivering
