Methoxyflurane

BT_PM 1.9

Describe the pharmacology of the following agents applicable to pain management, including:

  •   Opioids
  •   Tramadol
  •   Local anaesthetic agents (also refer to the Regional and local anaesthesia clinical fundamental)
  •   NSAIDs
  •   Paracetamol
  •   NMDA antagonists
  •   Anticonvulsants
  •   Antidepressants
  •   Corticosteroids
  •   Inhalational analgesics – nitrous oxide, methoxyflurane

Methoxyflurane has a risk of nephrotoxicity and hepatotoxicity TRUE/FALSE

Methoxyflurane can be used in paediatric practice TRUE/FALSE

Methoxyflurane is safe in patients with Malignant Hyperpyrexia. TRUE/FALSE

The “Penthrox” inhaler dispenses 2-4% methoxyflurane. TRUE/FALSE

A large proportion of the inhaled methoxyflurane that is taken up by the body is removed from the body by exhalation. TRUE/FALSE

BT_GS 1.27 Describe the pharmacology of nitrous oxide

These questions actually relate to Entonox which, as I’m sure you all know, is a 50:50 mixture of oxygen and nitrous oxide.

Q. An Entonox cylinder contains a mixture of liquid and vapour.  TRUE/ FALSE

Q. An Entonox cylinder is coloured French blue and white.  TRUE/ FALSE

Q. The Poynting effect refers to how interactions between two different gases leads to a change in their physical properties.  TRUE/ FALSE

Q. Entonox provides about 0.5 MAC.  TRUE/ FALSE

Q. Can cause megaloblastic anaemia.  TRUE/ FALSE

2017.1 : SAQ 5

Describe the advantages and disadvantages of using nitrous oxide as part of a general anaesthetic (well, this wasn’t exactly the question, I have corrected the spelling error that was on the paper :P)

BT_GS 1.27

This was a commonly used component of anaesthesia up until the late 90s. Can you sum up why it was used almost universally then, why many anaesthetists don’t use it routinely now, and where you think it should fit into your anaesthetic practice?

Nitrous oxide is more soluble in blood than desflurane   TRUE/FALSE

Nitrous oxide is more soluble in blood than nitrogen  TRUE/FALSE

Nitrous oxide undergoes approximately 10% hepatic metabolism  TRUE/FALSE

Nitrous oxide increases plasma homocysteine levels  TRUE/FALSE

Nitrous oxide is an analgesic agent  TRUE/FALSE

 

BT_GS 1.23 Physical Properties of Inhalational Agents

Before we do vaporisers, we should cover some of the physical properties of these agents.

BT_GS 1.23 Describe the physical properties of inhalational agents, including the:

· Principles of vaporisation of inhalational agents

· Properties of an ideal inhalational anaesthetic agent

· Structure-activity relationships of inhalational agents

TRUE/FALSE A partition coefficient of 1.4 means that at equilibrium the partial pressure in blood is 1.4 times that in the alveolus

TRUE/FALSE Saturated vapour pressure increases with temperature

TRUE/FALSE Boiling point decreases with falling atmospheric pressure

TRUE/FALSE Maximum sevoflurane concentration at sea level is 33%

TRUE/FALSE Using desflurane in a sevoflurane vaporiser would result in a sub anaesthetic desflurane dose

Below is a picture of a Schimmelbusch Mask.

A piece of gauze was placed over the top of the mask, and then the operator dripped ether onto the gauze. What would happen if you tried this with sevoflurane? Why was it safe to do with ether?

schimmelbusch

BT_GS 1.26 Inhalational Agent Toxicity

BT_GS 1.26 Describe the toxicity of inhalational agents

TRUE/FALSE CYP3A4 is responsible for the oxidative metabolism of halogenated inhaled anaesthetic agents

TRUE/FALSE Desflurane is less likely to cause hepatitis than Isoflurane

TRUE/FALSE Intrarenal metabolism of methoxyflurane can lead to oliguric renal failure

TRUE/FALSE Compound A exposure during anaesthesia causes a transient rise in blood creatinine and urea in humans

TRUE/FALSE Desflurane and Sevoflurane may produce signifcant quantities of carbon monoxide when used with dry CO2 absorbents

BT_GS 1.49 Mechanisms of Anaesthesia

I am hoping to focus on inhalational agents this week—as long as I can get all the questions written in time.

BT_GS 1.49 Discuss proposed mechanisms of anaesthesia and the sites of action of anaesthetic agents including the physiology and pharmacology of neurotransmitters and their receptors (that is, GABA, excitatory amino acids, acetylcholine, noradrenaline, dopamine and serotonin)

TRUE/FALSE Nitrous oxide produces analgaesia through actions on opioidergic neurons in the periaqueductal gray matter

TRUE/FALSE Inhaled anaesthetic agents probably have their action through inhibition of axonal propagation
TRUE/FALSE There is a rough correlation between inhalational anaesthetic potency and ability to hyperpolarize neurons.
TRUE/FALSE Halogenated inhaled agents increase the affinity of the GABA receptor for GABA
TRUE/FALSE Inhaled anaesthetics most likely have their action by perturbing the biophysical properties of lipid bilayers

I know you have all been sleepless with anticipation, desperate to know the answer to last week’s photo quiz. The final picture is of a boiler to produce steam for use in the CSSD. There are more medical gases in the hospital than you might think!

BT_GS 1.48 Regional Circulation

Back to some core pharmacology today 🙂 The link is to inhalational effects, although this LO itself is quite broad, and would cover a multitude of agents.

BT_GS 1.48 Describe the effects of anaesthetic agents on regional circulation

TRUE/FALSE Nitrous oxide has similar vasodilating effects to sevoflurane
TRUE/FALSE Desflurane abolished autoregulation of cerebral blood flow at 0.7 MAC
TRUE/FALSE Sevoflurane reduces pulmonary vascular resistance
TRUE/FALSE Sevoflurane should not be used above 1.3 MAC because of the risk of coronary steal
TRUE/FALSE Sevoflurane causes a dose dependent decrease in hepatic arterial blood flow