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Pharmacology Jeopardy Block 2 Part II Peter O. Beaumont, M.Sc. (Pharm) St. Vinnie’s Fall 2000. Local and General Anaesthesia. The Five Goals of General Anaesthesia. What are… Analgesia, amnesia, muscle relaxation, LOC and Loss of somatic & visceral reflexes
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PharmacologyJeopardy • Block 2 Part II • Peter O. Beaumont, M.Sc. (Pharm) • St. Vinnie’s Fall 2000
What are… • Analgesia, amnesia, muscle relaxation, LOC and Loss of somatic & visceral reflexes • The first three are universal, the last two are somewhat secondary
The Surgical Stage of Anaesthesia,and the easiest test to determine it
What are… • Stage III, and the eyelash reflex test
The greatest medical concern in Guedel’s stage II of anaesthesia
What is… • Aspiration of vomit • During this stage, delirium and excitement are often accompanied by retching,vomiting and incontinence. • Intubation must unfortunately wait until the patient loses gag reflexes
What is… • analgesia • this is soon accompanied by amnesia, but consciousness is not lost. • Remember, not all anaesthetics show all stages, and further, not all agents are good analgesics e.g. halothane
What is… • Nitrous Oxide • The others are all volatile liquids
What is… • Very slowly • The sooner the point of saturation is reached, the sooner the blood is willing to give up the agent to the brain tissues
The rate of onset of anaesthesia in a patient with heart failure
What is… • Faster than normal • This is is a tough concept • slowly flowing blood will reach its saturation sooner than fast flowing blood • A greater fraction of the CO goes to the brain in failure
Once you stop the flow of Nitrous and oxygen, this may happen to the patient post-op
What is… • Diffusion Hypoxia • A high partial pressure of gas coming out of solution dilutes oxygen in the lungs in the post-op patient • Only happens with nitrous oxide, others are used a too low partial pressure
When 1/2 your patients do not jump off the table following induction, this point is reached
What is… • MAC • By definition… when 50% of patients do not respond to a painful stimulus • highly dependent on degree of stimulation • Elderly and children have lower MAC
This prototypic GA has good effect, but high metabolism makes it undesirable these days
What is… • Halothane • Release of halogens can cause hepatotoxicity (methoxyflurane does this as well, so it is rarely used)
If you use halothane for a D&C, you must also use these two adjuncts
What are… • Opiods and oxytocin • Halothane has virtually no analgesic effect • oxytocin causes uterine contraction to counteract the relaxant effect of halothane
Were it not for concurrent muscle paralysis, patients induced with this agent might hurt themselves
What is… • Enflurane • Seizure complexes on EEG • EEG goes with Enflurane
This GA is great for maintenance, but rarely used for induction
What is… • Desflurane • Extreme sympathetic stimulation during induction. Also has a sharp irritating odour • Rapid post-op recovery
Some consider this GA to be the ‘Cadillac’ inhalation agent for short procedures
What is… • Sevoflurane • rapid onset and recovery • little airway irritation • 2-5% hepatic metabolism makes it less desirable for long procedures • Sevo is the “Seville”
Were it not for a high MAC, this agent would be a nearly ideal GA
What is… • Nitrous Oxide • No CV depression, excellent analgesia • Must be used with a second GA and paralytic agent
What are… • Barbiturates • Thiopental was the first - Still used widely today • Onset in 1 minute
While inhalation agents terminate their effect by exhalation, this is the mechanism for barbiturates
What is… • Redistribution • Also known as gamma phase redistribution • 99% hepatic metabolism to inactive compound AFTER termination of sedation effect
Incapable or reaching stage III themselves, these agents provide sedation and amnesia
What are… • benzodiazepines • Diazepam, lorazepam and midazolam are short acting agents • Slower onset than barbiturates • used as part of “balanced anaesthesia”
Occasionally used alone in Cardiac Sx, these agents typically support GA agents with analgesia
What is… • Opiods • patient may be ‘aware’ of or recall the Sx • Chest tightness impairing ventilation may occur
What is… • Neuroleptanesthesia • Important for painful, invasive procedures requiring patient cooperation
Dr’s and patients agree, this drug is the ‘real Pro’ of the induction agents
What is… • Propafol • Similar induction to barbiturates, but faster recovery • Patients feel much better post-op • May even have anti-emetic properties • much much more expensive than thiopental
What is… • dissociative anesthesia • Produced by ketamine alone • Similar to PCP • only CVS stimulant • good for Sx on patients in shock
This untoward effect of ketamine is obviated by pre-medication with diazepam or fentanyl
What is… • Emergence Phenomenon • hallucinations and perceptual illusions
This iv induction agents shares one shortcoming with halothane and one with nitrous oxide
What is… • Etomidate • No analgesia (halothane), no muscle relaxant effect (nitrous)