BT_PO 1.127 Outline the effects of anaesthesia and surgery on immune function

Nozawa Onsen

UPDATE: 26/9/18 for those who are interested, here is a relevant fairly recent article from BJA Education. It has opioids in the title but also talks about the impact of other anaesthetic agents. Interestingly it also discusses anti-nocioception (another tricky one…)

As a group, the participants in this blog (I can’t bring myself to says bloggers!) have been trying to address those LOs which are yet to receive a post – some of the remaining ones are quite unattractive ….

I don’t think this one is necessarily unattractive. It is an area that I suspect with continue to receive increasing attention in coming years as a target to improve peri-operative outcome.

It isn’t however a straightforward topic and not one that jumps out at you to learn – I suspect that is why is has been neglected.

Primer for the Primary Exam has this topic as low in importance, so don’t spend too long on it.

It is hard to find good simple information on this topic. Miller’s Anesthesia, in the chapter Nutrition and Metabolomics, covers the stress response to surgery and the effects of anaesthesia well. It also has a bit on the immune effects. The chapter is located beyond page 3000, perhaps giving us all a hint….

BT_PO 1.127  Outline the effects of anaesthesia and surgery on immune function

Immune cells express receptors (eg GABA-A) that are known targets of anaesthetic drugs T/F

It is likely that anaesthesia and surgery affect immune function T/F

It is too early to make definitive statements regarding the best anaesthetic combination to maintain a competent immune system T/F

Avoidance of hypothermia is known to assist in the maintenance of immune competency T/F

BT_PO 1.128 Describe the immunological basis and pathophysiological effects of hypersensitivity

Hedgerow by Angela Singer currently exhibited at Te Papa, Wellington

With the recent publication of the findings of the NAP6 audit, hypersensitivity (HS) is in the spotlight.

I have previously posted on anaphylaxis here but today we will stay a bit broader.

It may not be essential to know the exact Gell and Coombs classification of HS reactions, but it is not too complicated ( although I see that there have been some more recent amendements to it) and I think it does help with understanding of this reasonably common group of conditions

Power and Kam do this topic by far the best of the recommended texts in their chapter on the immune system. It would be reasonable for you to know the answer to the top 3.

BT_PO 1.128  Describe the immunological basis and pathophysiological effects of hypersensitivity

A single allergen may only produce a single type of HS reaction T/F

Type II hypersensitivity reactions, caused by antibodies binding to cell based antigens, include ABO incompatibility reactions T/F

A type I HS reaction can only occur after a prior exposure to the antigen T/F

I wouldn’t expect you to know the answer to these, but have a look if you are interested

Extrinsic allergic alveolitis is an example of Type III hypersensitivity caused by small immune complex deposition in tissues T/F
(as an aside the names of the causes of extrinsic allergic alveolitis are so descriptive . There is a list of some of them here – Hot Tub lung 😳)

Stevens-Johnson syndrome is a type of type IV hypersensitivity T/F

And one last thing. Blood is potentially a very immunogenic product. Have a think about the hypersensitivity reactions that can be caused by homologous blood. Then, have a think of what other immune mediated problems blood can cause.

BT_RT 1.6 Describe the physiological basis of anaphylactic and anaphylactoid reactions

OLYMPUS DIGITAL CAMERA

Relatives of the little guy hiding in the poppy, are big culprits in this department…

Anaphylaxis – arrgghh! I think this is one of the most awful complications associated with anaesthesia – its idiosyncratic nature mades it hard to avoid even with careful practice and, although rare, despite gold standard treatment a few patients will have a terrible outcome.

Anaphylaxis is obviously not a normal physiological response and hence tends not to be covered in physiology textbooks. Of those books on the reading list, Hemmings and Egan Ch 6 Adverse Drug Reactions and Miller Ch 34 Anaesthetic Implications of Concurrent Disease, both discuss it. Here  is and article from BJA Education and the Australian and New Zealand Anaesthetic Allergy Group have a wide range of resources especially for management of suspected anaphylaxis.

UPDATE SEPT 2018: following the comments after this post was originally published, I have amended the nomenclature of the statements. Unfortunately the LO remains as it is for now….

BT_RT 1.6 Describe the physiological basis of anaphylactic and anaphylactoid reactions

The first four of these statements are core and the answers and be found in the textbook references above

Allergic anaphylaxis is a Type 1 hypersensitivity reaction T/F

Following initial exposure to an allergen, IgE anitbodies are generated with circulate in the plasma until a repeat exposure T/F

Products of mast cells may be released en masse with both allergic and non-allergic anaphylactic reactions T/F

The symptoms of allergic anaphylaxis can all be attributed to histamine T/F

These two require a bit more thought (although the answer to the first in the books 😉 )

The severity of an non allergic but not allergic anaphylactic reaction may be reduced by giving a drug slowly T/F

Immediately after a life threatening allergic anaphylactic reaction, the same drugs may be given without risk if the same response T/F

2017.2 SAQ 11

Describe the immunology, mediators and pathophysiology of anaphylaxis. Do not discuss management.

Anaphylaxis continues to be a major cause of anaesthetic morbidity and mortality. Understanding the pathophysiology is essential in order to comprehend the management of this complex, challenging emergency.

T / F  histamine is released from MAST cells during anaphylaxis – it causes bronchospasm via H1 receptors

T / F  anaphylaxis to muscle relaxants can occur due to prior sensitisation from exposure to some cosmetics, or pholcodeine cough mixture

T / F  MAST cell degranulation occurs when an allergen binds to IgG on the MAST cell surface

T / F  histamine, leukotrienes and platelet activaing factor all increase vascular permeability during anaphylaxis – many litres of IV fluid can be needed during resuscitation

T / F  patients with anaphylaxis will reliably show a rash or urticaria

T / F  if you suspect a penicillin allergy, 100 mg of cephazolin can be given IV to determine if it is safe to give that drug