Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
45 Cards in this Set
- Front
- Back
|
What are the 2 main groups of inhalational anaesthetics? |
Volatile liquids Compressed gases |
|
|
What are the different volatile anaesthetics? |
Isofurane Servoflurane Halothane Desflurane |
|
|
What are the compressed gases? |
Nitrous oxide Xenon |
|
|
How can inhalational anaesthetics be administered? |
Induction chamber, face mask, nasopharyngeal insufflation, endotracheal tube, orotracheal tube, nasotracheal tube |
|
|
What is a vapouriser |
Liquid anaesthetics are delivered in a controlled manner by this method. Usually sits on the back bar. Dial to control the percentage concentration of inhalaed gas |
|
|
How does the anaesthetic machine get around the high pressure vapouriser? |
By pushing gas through at a higher than atmospheric pressure |
|
|
What is Tec |
Temperature compensated to prevent overcooling of the liquid - vapourisation is endothermic reaction |
|
|
What is the difference between a plenum type of vapouriser and a draw over vapouriser? |
Draw over vapourisers are within the system and rely on patients own respiratory efforts - less accurate than plenum type |
|
|
What are the 2 main types of scavanging? |
Passive and active scavanging |
|
|
What is passive scavanging> |
The hose being attached to a pressure relief valve on the breathing system which allows gas to be redirected to outside or a charcoal canister |
|
|
What is active scavenging? |
Extractor fan of vacuum pump to apply gentle suction at pressure relief valve - to outside |
|
|
What are the advantages to inhalational anaesthetic? |
O2 provided Airway protected Rapid induction and recovery from general anaesthesia and rapid change in anaesthetic depth is possible Minimal hepatic metabolism |
|
|
What are the disadvantages to inhalational anaesthetic? |
Expensive Pollution of the environment Personnel may be exposed to waste gases Toxic compounds risk - CO, compound A, formaldehyde |
|
|
What are properties of a good inhalational anaesthetic? |
Easily vapourised Non flammable, non explosive, stable on storage Non irritant or pungent Analgesia and muscle relaxation No renal or hepatic toxicity Smooth induction and recovery Cheap |
|
|
What are the components of the concentration gradient that an anaesthetic diffuses down? |
Vaporiser Anaesthetic System Alveoli Blood Brain |
|
|
What governs the rate of induction and recovery? |
The rate of change of the concentration of anaesthetic in the brain |
|
|
How do we monitor anaesthetic concentration in the brain> |
by monitoring the concentration in the alveoli -approximates brain concentration |
|
|
How does solubility affect uptake? |
Greater amount of the inhalational agent has to be dissolved in the blood before it can exert a pressure in the lungs and brain, rate of induction and recovery is slower |
|
|
What is the blood - gas partition coefficient? |
Describes the number of parts of gas in the blood compared to the alveolus, the higher, the more soluble it is in blood |
|
|
What will occur as a result of increased coefficient? |
Longer induction Longer recovery Slower rate of change |
|
|
What affects inhalational anaesthetic uptake in blood? |
Solubility in the blood, pulmonary blood flow, Cocentration gradient |
|
|
What affects inhalational anaesthetic uptake in the tissues? |
Solubility of agent in the tissues (tissue blood partition coefficient) Tissue perfusion Concentration gradient |
|
|
How are gaseous anaesthetic agents eliminated? |
Via the lungs, very little is metabolised (halothane having most and desflurane the least) by the liver . |
|
|
What affects rate of elimination |
The same factors affecting uptake |
|
|
What do we need to be aware of if the volatile agent is very lipid soluble? |
Slower induction and recovery due to redistribution into fat |
|
|
What is minimum alveolar concentration? |
Concentration of anaesthetic agent required to prevent movement in response to a painful stimulus. Therefore a measurement of potency |
|
|
What does it mean if MAC is low? |
Anaesthetic is high potency - very little required to produce an effect |
|
|
What how much MAC for clinical anaesthesia? |
1.25x |
|
|
What affects MAC |
Age, PaO2 and PaCo2 Hypo and hyperthermia High circulating catecholamines Pregnancy Hypotension Hyperthyroidism CNS stimulants or depressants |
|
|
What do not affect MAC? |
Duration - providing there are no complications Sex PH PaCo2 as long as it is 10-90mmhg Moderate anaemia Mean arterial blood pressure |
|
|
Why do we need to provide analgesia with the use of volatiles? |
They only produce unconsciousness, supplemental analgesia reduces pain sensetivity on recovery and reduces unconscious responses to pain |
|
|
Which gases produce CV and respiratory depression?> |
Nitrous oxide and xenon |
|
|
What are the CV effects of volatile anaesthetics? |
Hypotension, peripheral vasodilation and myocardial depression (negative intropy) |
|
|
What anaesthetics produce breath holding due to being quite pungent? |
Isofluorane and desoflourane |
|
|
What is the MAC of N2O in dogs and cats? |
200% |
|
|
Why cant you use N2O as an anaesthetic agent at normal atmospheric pressures? |
Would result in hypoxic gas mixture being delivered |
|
|
What is the advantage of adding N2O? |
MAC sparing in sub anaesthetic doses for volatile anaesthetics (less needed) Acts as analgesic at NMDA |
|
|
What is the second gas effect? |
Nitrous is relatively insoluble in the blood and is administered in high doses, its uptake into brain as well as blowoff occurs rapidly. Rapid removal from alveoli resulting in relative increase in concentration. Only works if agents have high blood solubility. (Increasing concentration gradient for volatiles |
|
|
What is diffusion hypoxia? |
At the end of the anaesthetic N2O is rapidly lost which dilutes the concentration of O2. Hypoxaemia may result unless o2 is supplemented |
|
|
Why does N20 enter gas filled spaces? |
More soluble than nitrogen so leaves blood into gas filled spaces quicker increasing pressure of volume in gas filled space |
|
|
What are the health impacts of N2O |
Vitamin B12 enzyme activity reduced Blood dyscrasias Bone marrow suppression Infertility Neurologic defecits |
|
|
Which inhalational agent is irritant? |
Isoflourane |
|
|
Which inhalational agent has the greatest negatively ionotropic effect? |
Halothane |
|
|
Which inhalational agent has the greatest reduction in systemic vascular resistance? |
Isofluorane |
|
|
Which inhalational agent has the greatest respiratory depression? |
Isofluorane |
