Pharm - General Anaesthesia Flashcards
What are the physiological state induced by General anaesthesia ?
- Analgesia
- Amnesia
- Loss of consciousness
- Inhibition of sensory & autonomic reflexes
- Skeletal muscle relaxation
What type of drugs are given prior to general anaesthesia?
- To relieve anxiety – benzodiazepines.
- To prevent allergic reactions – anti-histamines.
- To prevent nausea & vomiting – anti-emetics
- To provide analgesia – opioids.
- To prevent bradycardia & secretion – atropine
What are the two categories of Anaethesic agents ?
- Inhalation - for maintenance
*Intravenous - For Induction & short procedures
What is Induction of General anaesthesia?
This is the time from administration of GA to achievement of surgical anaesthesia.
What is Recovery of General anaesthesia?
This is the reverse of induction.
What are the types of Inhaled general anaesthetics?
- Halogenated Hydrocarbon
- Non-halogenated gas
What are examples of Halogenated hydrocarbons?
Desflurane
Isoflurane
Sevoflurane
Halothane
” DISH “
What is an example of Non-Halogenated gas?
Nitrous Oxide
How are inhaled general anaesthetics measured?
Their partial pressure or “tension” in the inhaled air or in the blood or other tissue is a measure of their concentration
Fill in the blanks. “ 50% nitrous oxide in inhaled air would have a partial pressure of
__________.”
380 mm Hg
What are the factors influencing the rate at which the therapeutic concentration of inhaled anaesthetics achieved in brain?
- Solubility
- Pulmonary ventilation
- Partial pressure of inhaled gas.
- Alveolar blood flow
- Arteriovenous concentration gradient
What are the most important characteristics of Inhalation GA which govern anaethesia?
- Solubility in the blood (blood : gas partition co-efficient).
- Solubility in the fat
(oil : gas partition co-efficient)
Fill in the blanks.” In regards to the Inhalation agent, _________________ is the single most important factor in determining speed of induction & recovery.”
Solubility in the blood
True or False? “ The more soluble an agent is in the blood the more must be dissolved to raise its partial pressure.”
TRUE!!
True or False? Agents that are less soluble in blood (ex. nitrous oxide) provide a rapid induction because the blood reservoir is small & anaesthetic is available to pass into the brain sooner.
TRUE!!
True or False? The higher the lipid solubility the potent the anaesthetic ex Halothane.
TRUE !!
What is the minimum alveolar concentration (MAC)?
This is defined as the concentration of inhaled anaesthetic, (as a % of inspired air), at which 50% of patients do not respond to a surgical stimulus
True or False? The more lipid soluble the anaesthetic , the lower the MAC and the greater the potency.
TRUE!!
In the event of Malignant hyperthermia caused by the use of Inhaled Anaesthetics except Nitric oxide , what is the drug choice of treatment ?
Dantrolene
What is an Adverse effect of Nitrous oxide?
Risk of bone marrow depression w prolonged administration(›6hr) causes inactivation of methionine synthase, needed for DNA & protein synthesis→ bone marrow depression.
What is the MAC for Nitrous oxide?
100%
Which halogenated hydrocarbon inhaled anaesthetics is a powerful coronary vasodilator?
Isoflurane
What is the MAC of Isoflurane ?
1.4%
Which halogenated hydrocarbon inhaled anaesthetics is used for GA especially in children, b/cause it is not irritating to airways?
Sevoflurane
What is the MAC for Sevoflurane?
3%
Which inhaled anaesthetics is a Respiratory tract irritant → coughing & bronchospasm?
Desflurane
What is the MAC for Desflurane?
6 %
Which inhaled anaesthetic can have levels of Fluoride detected after use?
Sevoflurane
Which Inhaled anaesthetic causes a potential for Malignant Hyperthermia?
Desflurane , Isoflurane & Halothane
What are the Adverse effects pf Halothane?
- Hepatotoxicity – halothane hepatitis (fulminant hepatic necrosis)
- Cardiac arrhythmias, * Hypotension
- Malignant hyperthermia
What is the MAC for Halothane ?
0.75 %
What are the Types of Intravenous General Anaesthetics used ?
Barbituates
Benzodiazepines
Dissociative - Ketamine
Opioids
Miscellaneous- Etomidate , Propofol
What is the MOA of Thiopental?
It binds to GABA A receptor which results in prolonged opening of the chloride channel.
What are the adverse effects of Thiopental?
- Depresses cerebral blood flow & oxygen consumption by brain.
- May induce laryngospasm & bronchospasm
What happens if Benzodiazepines are used with Opioids?
Cardiovascular collapse & respiratory arrest can occur
What are the Clinical functions of Benzodiazepines ?
- Pre-operative Sedation.
- Intraoperative Sedation.
- Part of balanced anaesthesia.
How can the effects of Benzodiazepines be reversed?
Giving the drug Flumazenil
Which Benzodiazepines is the preferred choice for induction and maintenance of Anaesthesia?
Midazolam
Which drug is an analogue of phencyclidine (PCP, “angel dust”) w/ similar properties?
Ketamine
What happens when a patient is given a Dissociative anaesthetic?
The patient may remain conscious although amnesic & insensitive to pain.
What are the adverse effects of Ketamine?
Disorientation, sensory & perceptual illusions, vivid & unpleasant dreams
What is the treatment for Opioid overdose?
Naloxone
Which Intravenous general anaesthetic is used in critical care setting as continuous infusion to provide prolonged sedation?
Propofol
What are the adverse effects of Propofol?
Hypotension
Negative inotropic effects
Apnoea
Which drug can be used for for induction of anaesthesia in patients with limited cardiovascular reserve?
Etomidate
Which drug with a prolonged Prolonged infusion can cause possible risk of adrenocortical suppression ?
Etomidate
What is the MOA of Ketamine?
Inhibits NMDA receptor
