BT_PO 1.54 Pharmacology of beta receptor blocking agents

jan 2006 156

I asked about these drugs in the recent in exams and was fascinated (read horrified and astounded) that only one person had a plausible explanation as to how these little chaps cause hypotension…..

These drugs are actually mentioned in 5 LOs BT_PO 1.54 and BT_PO 1.57-1.60

We see a lot of patients on these drugs, partly because they have been shown to confer a survival advantage in people with heart failure, so it is probably a good idea to know a bit about them…

BT_PO 1.54 Describe the pharmacology of commonly used alpha and beta receptor blocking agents, their clinical use, adverse effects and use in the perioperative period

 

Metoprolol is metabolised by the CPY2D6, and hence prone to large inter individual variation in response   TRUE/FALSE

Beta1 selective blockers produce a significant reduction in blood pressure when given to normotensive individuals     TRUE/FALSE

Hypotension with beta blockers is mediated by the dilation of vessels in skeletal smooth muscle   TRUE/FALSE

Beta blockers cause a reduction in the release of renin TRUE/FALSE

Some beta blockers have an alpha agonist effect TRUE/FALSE

BT_PO 1.125 Pharmacology of cancer chemotherapeutic agents, especially problems that such agents may cause during the perioperative period

I was asked about this in my Primary Exam! I have to admit that I had elected not to study the chemotherapeutics, (not a strategy that I would recommend 😉) but fortunately I was able to drag something from the back of my brain….

There is one chemotherapeutic drug in particular which has very significant anaesthetic implications ( I was unaware of this 20 yrs ago!) and you should have some knowledge of it.

Several others can have effects on organ systems which may be of consequence once anaesthesia is administered.

There is an  overview of the topic, with an anaesthetic bent, here, but all the standard texts will have chapter on chemotherapeutic agents.

rosy-periwinkle-400x266

Several chemotherapeutic drugs, including vincristine, are derived from the above plant, the Madagascar Periwinkle…..

BT_PO 1.125 Outline the pharmacology of cancer chemotherapeutic agents with particular reference to problems that such agents may cause during the perioperative period

The risk of oxygen induced pulmonary toxicity, following bleomycin treatment, persists for life  TRUE/FALSE

Anthracyclines, such as doxurubicin and daunorubicin, may cause an acute myocarditis TRUE/FALSE

Anthracyclines may cause a chronic dilated cardiomyopathy, which is dose dependent in nature TRUE/FALSE

Vincristine can cause both a peripheral and autonomic neuropathy TRUE/FASLE

The bone marrow suppression associated with chemotherapy usually preserves platelets TRUE/FALSE

Another structure quiz

This seemed to be popular last time.

As with the structures shown previously, you are unlikely to have to draw these in the exam. Some of them, you wouldn’t be expected recognise. If you don’t recognise the molecule, have a look at its structure and see what clues that gives you to its function. Several of the molecules are related to each other. All of these molecules are, or have been, used in anaesthetic practice.

I have included a couple of historic interest

1.

Chloroform

 

2.

iso-structure

3.

medchem1ic_Enflurane_full_498_229__0_native

 

4.

1200px-Codein_-_Codeine.svg

5.

1200px-Morphin_-_Morphine.svg

6.

150px-(1S,2S)-Tramadol_gespiegelt.svg

7.

naloxone.jpg.pagespeed.ce.Q70R1-33LY-2

8.

Tubocurarine.svg

9.

g-386

10.

g-590

 

 

BT_GS 1.16 Describe alterations to drug response due to obesity

Ok, I’ve paraphrased that LO a bit, so that we can stay with the topic for one more day.

We give drugs to people with a high BMI on a daily basis (at least at the institution I work in..), so it is important that we know what the implications of a larger lipid load are and how to adjust our dosing…

For today’s picture I have chosen another one of Andy Paiko’s amazing glass works.

andy-paiko-glass-syringe

 

BT_PO 1.16  Describe alterations to drug response due to physiological change with particular reference to the elderly

This is a complicated issue [I’m giving you a free true statement]

It is appropriate to dose muscle relaxants, such as vecuronium and rocuronium, based on ideal body weight (IBW)    TRUE/FALSE

When using propofol for maintenance of anaesthesia, calculate the infusion rate based on total body weight (TBW)    TRUE/FALSE

The increased cardiac output seen in morbid obesity, will hasten recovery from volatile anaesthesia TRUE/FALSE

Plasma levels of pseudocholinesterase are increased with morbid obesity TRUE/FALSE

Suxamethonium doses should be based on TBW  TRUE/FALSE

Are your patients talking about this…..

Two posts in one day!! Thought I might as well post about this whilst it was back in my brain.

On June 7 Richard Fidler conducted an interview on ABC local radio, on the topic of consciousness and anaesthesia.

Two patients asked me about it within 24 hrs of it airing……

One, who had listened to it on the day of his procedure, was mildly terrified by the interview ( I hadn’t heard it at that stage, but did my best to reassure him).

I listened to the interview on my walk in to work the following morning.

The first patient of the day mentioned the interview to me. She was fascinated! She had me repeat a random word to her throughout the case to see if she could recall it after the event – she couldn’t! [although I didn’t hypnotise her]

It came to mind today as I was listening to one of my favourite podcasts, Chat10Looks3 , where the interview is discussed again.

It is worth listening to. Make up your own minds about it. It is always good to be cognisant of the information out patients are receiving about our specialty – the information doesn’t always come from us…..

Another cool book that should be on the ‘Recommended Texts for the Primary’ list

9781905237166-us

Most people don’t find pharmacokinetics particularly palatable. This book is arguably one of the most enjoyable ways you can learn about pharmacokinetics. This book doesn’t just entertain but it also gives you a sound understanding of PK concepts as they relate to the practising anaesthetist. It is under 200 pages and can be read in a day. It is fairly non PC which accounts for half its charm. Nothing in there about TCI sadly.

Addendum by woundedwildebeest… I got to see this post when it was a draft and bought the book. I definitely second this recommendation. Funny, educational, with even a dramatic twist on the last page. I’d suggest reading a chapter at a time and applying it in theatre before moving on to the next.

BT_PO 1.116 composition, indications and risks of blood products

These questions relate to Fibrinogen:

Q. Is designated by the Roman numeral II.  TRUE/ FALSE

Q. Is the predominant clotting factor found in Prothrombinex.  TRUE/ FALSE

Q. Is the predominant clotting factor found in the circulation.  TRUE/ FALSE

Q. Has a reduced concentration in the pregnant individual.  TRUE/ FALSE

Q. Is a Vitamin K dependent clotting factor.  TRUE/ FALSE

 

Methoxyflurane

BT_PM 1.9

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

  • ï‚·  Opioids
  • ï‚·  Tramadol
  • ï‚·  Local anaesthetic agents (also refer to the Regional and local anaesthesia clinical fundamental)
  • ï‚·  NSAIDs
  • ï‚·  Paracetamol
  • ï‚·  NMDA antagonists
  • ï‚·  Anticonvulsants
  • ï‚·  Antidepressants
  • ï‚·  Corticosteroids
  • ï‚·  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

Queen’s Birthday Special

It seems serendipitous that last week’s posts were obstetric related and today is the Queen’s Birthday holiday…

Queen Victoria was a relatively early adopter of anaesthesia and received chloroform anaesthesia for the birth of her 8th and 9th children, Leopold in 1853 and Beatrice in 1857. The chloroform was administered via an open drop technique, during the second stage of labour, with the aim of achieving semi-consciousness. The Queen is quoted as saying the chloroform was “soothing, quieting and delightful beyond measure”

 


It was James Simpson who, in 1847, first suggested the use of anaesthesia for labour. Initially obstetricians were almost universally opposed to the use of anaesthesia for labour, citing it as unnecessary for a natural process and concerned for the safety aspects.

John Snow, who anaesthetised Queen Victoria on both occasions, was a physician with a career spanning interest in anaesthesia. He experimented widely, on animals, using different inhaled substances in an attempt to find superior anaesthetic agents. He realised that the volatility of an agent declined as it was vaporised , due to the drop in temperature. Consequently he developed and early vaporiser, with a brass chamber which was immersed in water, to minimise temperature fluctuations. He appears to have been a man of great scientific rigour, which likely inspired confidence amongst the Queen’s physicians and eased the path for her to receive anaesthesia, when she and Prince Albert requested it. He was also a strong proponent of a doctor separate to the surgeon administering the anaesthetic. One of his major works On Chloroform and Other Anaesthetics and their Administration was published following his death is 1858. If you click on the title it will take you to a copy of the book, with William Morton’s name handwritten across the top!

John Snow made another great contribution to medicine as an epidemiologist. He was a believer that cholera was transmitted by contaminated water, contrary to popular belief at the time. Following an outbreak in London in 1854, he conducted an extensive epidemiological investigation tracking the details of victims and non victims to identify where they sourced their water. He identified the likely source as a pump on Broad Street, Armed with his research, he went to town officials and convinced them to remove the pump handle, making it impossible to draw water from the pump. The outbreak stopped almost instantly! It wasn’t until 1883 that Vibrio cholerae was isolated by Robert Koch and the means of transmission confirmed.

John Snow died age 45. Just imagine what he might have contributed to our speciality ( and others) if he had lived a long life……

John_Snow

BT_GS 1.59 Describe the pharmacological principles and sources of error with TCI

kindle cover2504Many of us use TCI on a daily basis. Indeed some people use it almost exclusively. Fewer appreciate the remarkably small data set that the algorithms were created from. Even fewer understand the limitations of the algorithms. If you want to find the answers to the statements below can I suggest you look at the chapter “Everything you should know about Propofol TCI” in the book The First Year. It can be freely downloaded from the College Library: click on Library Guides> Medical Education> Featured Resources and scroll to the bottom. The pdf is waiting for you. The cover is reproduced above. The TCI pump algorithms are poorly treated in the texts.

Q. A TCI using the Marsh algorithm will give the same dose of propofol to an eighty year old and a twenty year old patient of the same weight.  TRUE/ FALSE

Q. TCI can be used for morbidly obese patients.  TRUE/ FALSE

Q. The Minto algorithm for Remifentanil was devised by an Australian anaesthetist.  TRUE/ FALSE

Q. Plasma or effect site TCI can be used effectively for the Schnider algorithm.

Q. The James equations are used to calculate LBM in the Minto and Schnider algorithms.  TRUE/ FALSE