h_anaesthesia
Table of Contents
history of anaesthesia
a brief history of local anaesthesia
- 1860: Niemann purifies cocaine, an alkaloid contained in the leaves of Erythroxylon coca, a shrub growing in the Andes.
- 1880: Von Anrep observed the local anaesthetic effects of cocaine when given subcutaneously.
- 1884: Sigmund Freud studied the physiologic effects of cocaine & used it to wean a colleague off morphine but produced one of the 1st-known cocaine addicts of modern times!
- Koller introduced cocaine as a LA in ophthalmology & Hall in dentistry.
- 1885: Halsted lays foundation for nerve block anaesthesia surgery by demonstrating that cocaine could stop the transmission in nerve trunks.
- Corning produced spinal anaesthesia in dogs.
- 1905: After 13 yrs research, a cocaine substitute was found - procaine - which became the prototype for local anaesthetic agents for nearly 50 yrs.
- 1948: lignocaine introduced.
- 2005: articaine introduced in Australia as LA for dental use.
brief timeline of general anaesthesia
pre-1846
- Surgical procedures uncommon.
- Understanding of the pathophysiology of disease & the rationale for surgery was rudimentary.
- Aseptic technique & the prevention of wound infection were almost unknown.
- Lack of a satisfactory anaesthetic was a major deterrent.
- Mortality was high & surgery mainly for emergencies only - eg. limb amputation;
- Analgesics available included alcohol, hashish, opium derivatives, while physical methods such as packing a limb in ice or making it ischaemic with a tourniquet were occasionally used.
- Despite nitrous oxide being discovered in 1776 by Priestley, & its anaesthetic properties being noted in 1796 it was not used in medicine.
- Faraday noted in ~1816 that inhalation of diethyl ether produced similar effects to nitrous oxide. But despite its use at carnivals & at “ether frolics” it was not used in medicine.
- Partly this was due to general lack of concern for the well-being of one's fellows & at a time when burning witches at the stake was commonplace. The gradual change in attitudes along with advances in medicine & chemistry in mid-19th century paved the way for development of anaesthetics.
the development of surgical anaesthesia
- 1846: Morton's classic public demonstration of ether as a surgical anaesthetic.
- Ether - the ideal “first” anaesthetic:
- readily made in pure form; liquid at room temp.; readily vaporised;
- potent (unlike nitrous oxide) - a few volumes percent adequate
- supported respiration & circulation - important at a time when known physiology was inadequate for assisted ventilation & circulation.
- not toxic to vital organs
- 1847: Scottish obstetrician James Simpson introduced chloroform as anaesthetic.
- Chloroform became popular anaesthetic esp. in UK for nearly 100yrs as it had a more pleasant odour & non-inflammable, despite it being hepatotoxic & a severe cardiovascular depressant with a relatively high incidence of post-op death!
- 1863: Nitrous oxide re-introduced largely through efforts of Colton.
- 1868: Combined use of oxygen & nitrous oxide described by Andrews.
- soon thereafter, the 2 gases became available in steel cylinders.
- 1929: Anaesthetic properties of cyclopropane accidentally discovered.
- After extensive clinical trials, cyclopropane became the most widely used GA for next 30yrs.
- However, the increasing risk of explosions by the increasing use of electrical equipment meant a safer agent was needed.
- 1935: Lundy demonstrates usefulness of IV thiopentone, originally as sole agent, but doses required caused serious depression of CVS, Resp & CNS depression. It did however, become enthusiastically accepted for rapid induction of GA.
- 1940's: Anaesthetists use curare to provide muscle relaxation, permitting adequate conditions for surgery with light levels of anaesthesia, minimising cardiovascular depression & post-op sedation. Several synthetic substitutes used over next 6 yrs.
- 1956: ICI introduce halothane - a non-flammable anaesthetic which became the basis for most of the newer agents.
- 1960: methoxyflurane introduced but its use as a GA limited due to nephrotoxicity.
- 1973: Enflurane introduced into general clinical use, initially to avoid rpt use of halothane.
- Lower incidence of arrhythmias, post-op nausea & vomiting than halothane
- Potentiates muscle relaxants, reducing doses needed of those.
- Problems:
- seizures may occur in predisposed pts
- uterine relaxation at deep levels a problem in labor
- 1981: Isoflurane introduced:
- Depth of anaesthesia more rapidly adjusted than with enflurane or halothane.
- Causes systemic vasodilation (incl. coronary vessels), but maintains cardiac output.
- Arrhythmias uncommon allowing higher doses of adrenaline for hemostasis.
- Potentiates muscle relaxants, reducing doses needed of those.
- Allows control of cerebral blood flow & intracranial pressure.
- Minimal metabolism & no reported hepato/nephrotoxicity.
- Problems:
- more pungent odor than halothane
- progressive resp. depression & hypotension
- uterine relaxation can be undesirable
- 1990's propofol introduced as an IV induction agent
- Rapid induction & recovery from GA - good for brief anaesthesia in day stay pts
- Minimal post-op confusion cf thiopentone but similar nausea, vomiting & headache.
- Injection is more painful but rarely followed by phlebitis or thrombosis.
- Can be used as continuous infusion with opioids/nitrous oxide.
- 1990's: Sevoflurane introduced
h_anaesthesia.txt · Last modified: 2009/03/18 02:46 by 127.0.0.1