A very concise set of notes covering the important aspects of anaesthesia & surgical drugs required to pass the GPhC exam. Topics include:
- General anaesthetics
- Local anaesthetics
- Pre- & peri-operative medicine
GENERAL ANAESTHESIA
OVERVIEW:
- TWO MAIN TYPES of general anaesthetics (GAs):
o IV
o Inhalational (using a volatile liquid or gas)
- Anaesthesia can be INDUCED & MAINTAINED using either type (often used in combin.)
- When should the DOSE of GAs be REDUCED:
o Pt has severe hepatic impairment (less metabolism of GA)
o Pt is acutely ill (may exacerbate dyspnoea)
o Pt is debilitated
GA PHARMACOLOGY:
MOA: Cause CNS DEPRESSION through different mechanisms:
o Enhance effects of GABA (Propofol, Etomidate, Barbiturates, Fluorinated liquid)
o Inhibit effects of Glutamate on NMDA receptors (Ketamine, N2O) – illicit drugs
- This leads to THREE MAIN EFFECTS:
o Unconsciousness/Sedation
o Complete loss of sensation (Can’t feel, smell, hear, or see anything)
o Muscle Paralysis (which also disables your reflexes – no twitching during surgery)
- GAs put the pt in a MEDICALLY INDUCED, REVERSIBLE COMA
- This differs from analgesia which just treats PAIN but allows you to feel other stimuli e.g.
pressure, temperature, vibrations etc.
Intravenous GAs Inhalational GAs
- Propofol - Nitrous Oxide (N2O)
- Etomidate - Fluorinated volatile liquids
- Barbiturates (‘-Tals’) (‘-Fluranes’):
o Thiopental o Desflurane
o Phenobarbital NOT indicated for GA o Sevoflurane
- Ketamine (NMDA antagonist) o Isoflurane
GENERAL SIDE EFFECTS OF ALL GAs:
- HYPOtension: due to relaxation of vascular smooth muscle Vasodilation
- HYPOthermia: vasodilation of peripheral vessels increased HEAT LOSS (feel colder)
- Nausea & Vomiting (PONV): GAs stimulate the CTZ emesis
DRUG-SPECIFIC SIDE EFFECTS:
- Fluorinated liquids:
o Reflex Tachycardia: HR increases as a homeostatic reflex to increase BP – almost
all GAs disable this reflex EXCEPT for fluorinated liquids
o Airway irritation: these volatile liquids have a PUNGENT SMELL – induces
bronchospasm & should NOT be used for induction except for Sevoflurane
o Malignant Hyperthermia (see below)
- IV GABA enhancers: Respiratory depression - similar mechanism to benzos & opioids
- NMDA Antagonists: Hallucinations & Nightmares – rationale for abuse potential
, MALIGNANT (lethal) HYPERTHERMIA (MH):
- MH: RARE but LIFE-THREATENING reaction to TWO MAIN DRUGS:
o Fluorinated liquids (‘Fluranes’)
o Suxamethonium (Neuromuscular blocker – NOT a GA)
- SYMPTOMS (RAT): These symptoms are all caused by an INCREASE in
o Rigidity of muscles METABOLISM increased muscle activity, increased
o Acidosis CO2 production (produces carbonic acid) & increases
o Temperature temperature (heat is a by-product of metabolism)
- TREATMENT:
o Dantrolene: muscle relaxant reduces heat generated from muscle
contractions
o STOP the offending drug (e.g. fluorinated liquids or suxamethonium)
CHOICE OF GAs FOR INDUCTION (i) & MAINTENANCE (m)
- Propofol - i AND m : BEST ALL-ROUND GA (but has slight hangover effect)
- Thiopental – i ONLY: VERY SHORT ACTING barbiturate with little analgesic effect -
although it’s short-acting, it accumulates in adipose tissue sedation lasts 24 HOURS
- Etomidate – i ONLY: Like thiopental (short-acting & no analgesia) - weakest hangover
- Ketamine – i ONLY: RARELY used due to psychiatric ADRs – used mainly in PAEDIATRICS
- Nitrous oxide – m ONLY: difficult to induce sedation due to lack of potency – but has
GOOD ANALGESIC properties – often combined with other GAs to reduce their dose
PERI- & PRE-OPERATIVE DRUGS (NOT anaesthetics)
1- BENZODIAZEPINES:
- Useful for SEDATION, ANXIOLYSIS, & ANTEROGRADE AMNESIA (inability to form new
memories after taking the drug – so pt won’t remember going into the operating room)
- ORAL, SHORT-ACTING benzos often used as premedication – EXAMPLES:
o Lorazepam
o Temazepam
- ANTIDOTE for benzo OD = Flumazenil (benzo-receptor INHIBITOR on GABA receptor)
2- ANTIMUSCARINICS (AMs):
- Useful in DRYING BRONCHIAL & SALIVARY SECRETIONS which may be caused by:
o Intubation Anything that touches the RT will stimulate
o Inhalational GAs saliva/mucus secretion – this is a reflex to
o Surgery of the respiratory tract (RT) either digest/remove the foreign object
- Useful in counteracting the muscarinic ADRs of NEOSTIGMINE (acetylcholinesterase
inhibitor)
- EXAMPLES:
o Glycopyrronium
o Hyoscine hydrobromide (Scopolamine – also has ANTI-EMETIC effects)
o Atropine (ONLY FOR EMERGENCIES)
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller muammalal-bayati. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $7.80. You're not tied to anything after your purchase.
