BT_PM 1.3 Pre-emptive and preventive analgesia


Glass poppies Andy Paiko


A few weeks ago I ran a series of posts on this LO.

I ran out of steam before reaching the last of the bullet points. This was partly because the area has held so much hope from a theoretical mechanistic viewpoint but there is little strong scientific evidence to support benefit from particular clinical practice – how disappointing….

I thought it might be timely to revisit now, just before the written exam. I wish there were a rapidly acting pre-emptive analgesic, I could prescribe, to make tomorrow less painful for those of you about to sit. However, the best prescription, to make the day easier, is to have studied well and practised lots – which I am sure all of you who read this blog will have done. BEST WISHES!!

The latest edition of Acute Pain Management: Scientific Evidence has a section on this topic (I hope that link takes you there. If it doesn’t, the book is freely available here [see section 1.5]).

BT_PM 1.3  Describe the basic physiological mechanisms of pain including:

· Pre-emptive and preventive analgesia

Pre-emptive analgesia, by definition, must be given before a noxious stimulus occurs TRUE/FALSE

The aim of pre-emptive and preventive analgesia is to reduce sensitisation   TRUE/FALSE

The NMDA receptor plays an important role in central sensitisation  TRUE/FALSE

Peri-operative ketamine infusions may have a role in preventing the development of chronic post-surgical pain    TRUE/FALSE

Outcomes in this area have been muddied by fraudulent research   TRUE?FALSE

BT_PM 1.3 Describe the central processing of pain

In the protracted series on this LO, today we have made it to the brain. Again a complex area, but one where it is important to have some fundamentals sorted in your minds.

Version 2

I thought you might need something beautiful today as an antidote to all the pain… Here is the inverted dome ceiling of the Palau de la Musica in Barcelona. The whole building is amazing and the ceiling even more sublime in person

BT_PM 1.3  Describe the basic physiological mechanisms of pain including:

• Central processing of pain


Nuclei in the lateral thalamus mediate the processing of the sensory and discriminative aspects of pain   TRUE/FALSE

The amygdala is involved placing pain within an emotional context, which may enhance to inhibit the pain experienced     TRUE/FALSE

The primary somatosensory cortex is involved with both sensory and emotional processing of pain    TRUE/FALSE

Nuclei in the medial thalamus have projections to areas involved with the affective experience of pain      TRUE/FALSE

At the level of the brainstem, and through associated neural networks, there is modulation of the autonomic response to pain  TRUE/FALSE

BT_PM 1.3 Describe the physiology of signal conduction in relation to pain

I am going to interpret this as signal conduction from the periphery to the brain, in other words, conduction along the primary and secondary (or projection) afferents.


This is definitely an area where you don’t want the wires getting crossed…… (photo Ho Chi Minh City)

BT_PM 1.3  Describe the basic physiological mechanisms of pain including:

· Conduction


Voltage gated sodium channels are important in normal and abnormal transmission of signals along the primary afferent neurone  TRUE/FALSE

Increased potassium conductance in the primary afferent neurone will tend to enhance signal transmission    TRUE/FALSE

Nociceptive-specific projection afferents predominate in Rexed lamina I and respond exclusively to noxious stimuli   TRUE/FALSE

Wide dynamic range neurones receive input from visceral and somatic sources TRUE/FALSE

Activation of NMDA receptors, on the post synaptic membrane, occurs readily at normal signal transmission strength TRUE/FALSE

BT_PM 1.3 Describe the physiology of spinal cord modulation of pain

Rather than asking what can happen to the pain signal at the spinal cord, perhaps we should ask what doesn’t happen!!

This is a complex area, but it is important to understand some basic principles…


This pretty crumby photo of the maze at Schloss Schönbrunn reminded me of today’s topic…

BT_PM 1.3 Describe the basic physiological mechanisms of pain including:

· Spinal cord modulation


In the dorsal horn, both inhibitory and excitatory interneurones may synapse with the primary afferent   TRUE/FALSE

GABA is an important neurotransmitter of inhibitory interneurones  TRUE/FALSE

Virtually all primary afferents exert their excitatory effects on postsynaptic structures by the release of glutamate TRUE/FALSE

Opioid receptors are found pre- and post-synaptically on neurones in the dorsal horn TRUE/FALSE

Descending inhibitory pathways exert their influence at the dorsal horn   TRUE/FALSE


There are some more relevant statements at this post  from early 2017

Over at aGasgal, I have put up a couple of  my favourite simple diagrams related to pain pathways.


BT_PM 1.3 Physiology of peripheral nociception

Happy new year to everyone. I hope that the first days of 2018 have treated you kindly.

There are quite a few LOs on the neurobiology of pain, but not many posts here on the topic (I’m not surprised….)


Above is a poppy ( complete with bumble bee) taken at Port Arthur, where I suspect a lot of pain was both felt and inflicted….

I have taken today’s statements from Hemmings and Egan’s book which has quite a good chapter on nociceptive physiology.

BT_PM 1.3   Describe the basic physiological mechanisms of pain including:

· Peripheral nociception


Activation of peripheral opioid receptors reduces the likelihood an nociceptive signal being transmitted       TRUE/FALSE

Nocioceptors have both afferent and efferent functions TRUE/FALSE

Endogenous ligands of nociceptors include bradykinin and 5-HT    TRUE/FALSE

Primary hyperalgesia can occur when peripheral nociceptors are sensitised TRUE/FALSE

Each nociceptor responds to a single ligand/stimulus    TRUE/FALSE