Monthly Archives: October 2018

The physics of maiming a child (repost because of “those” scooters)

Dear Driver,

When you backed out of a driveway and did not even see how I swerved around behind your car to avoid T-boning you, how dare you have the temerity to tell me you were careful!  I was 7 feet tall, dressed in bright yellow and traveling at no more than 10 km/h.  Perhaps a simple lesson in physics will help you and your fellow “driveway backers” to realise how dangerous you are and to adopt safer driving practices.

In the diagram you can see a car backing out of a driveway.  Typically when you are at the edge of your property and have a fence (see photo below) blocking your view of the footpath you are able to see about 1.7 metres along the footpath.  Let us imagine that there is a child on a trike riding at 5 km/h just out of your line of sight.  How long  does it take them to travel that 1.67 metres?  The physics is quite easy.

5 km/h is 5000 metres in 60 x 60 seconds, ie about 1.4 m/s.  Putting this in the formula above means that it takes about 1.2 seconds for the child to travel that 1.67 metres. 

Now consider this. According to design guidelines for safe bicycle use 2.5 seconds must be allowed for someone to observe the danger, react, apply brakes and stop.  In other words, if you covered the distance from your driveway to the middle of the footpath, about 1 metre, in under 1.2 seconds you will almost certainly hit the child.  That is a speed of just 3 km/h!!!!!

Now consider who else is on the footpath, all legally:

  • Pedestrians 5 km/h
  • Joggers 5- 15 km/h
  • Kids on skateboards or scooters 10 km/h
  • Child on bicycle with small wheels, 10 km/h
  • Mobility scooter, 5-10 km/h
  • Me on my Trikke, 10 km/h
  • Postie on a bike 5-10 km/h.

For those going 10 km/h your speed needs to be just over 1.5 km/h to hit someone! That’s the legal people … but the Lime scooters at 20 km/h mean it all the more necessary to slow down.

So, before you do some damage here is what you can do:

  • Never back out of a driveway unless you really really must.  If you think you must because of the design of your driveway, change the design!
  • Cut back those hedges, remove some of that fence so that you can see further. [ City councils… please make a by-law to make this happen].
  • Always always always stop at the end of your driveway (BEFORE THE FOOTPATH) and toot a horn.  Then proceed very very slowly.

By the way, you are legally obliged to give way:

(1)
A driver entering or exiting a driveway must give way to a road user on a footpath, cycle path, or shared path (as described by clause 11.1A(1)).

Thank you for considering the physics of maiming a child, may you never find your self in such a terrible situation.

Regards,

Dr John Pickering

A typical driveway with almost non-existant visibility
 A typical driveway with almost non-existent visibility

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Feature Image: Intangible Arts https://www.flickr.com/photos/intangible/ under Creative Commons Attribution 2.0 licence.

Cheesecake files: A new test to rule out heart attacks in just a few minutes.

Your chest hurts, you go to the hospital (good move), you get rushed through and a nurse takes some blood and measures the electrical activity of your heart.  A doctor asks you some questions.  While she does so, the blood is being tested – the results are back already! Yeah, they are negative and everything else is OK, it’s not a heart attack – you can go home.  This is the likely scenario in the near future thanks to new blood test technology which we, in Christchurch hospital’s Emergency Department, have been fortunate to be the first in the world to trial in patients. The results of our pilot study have now been published ( in a Journal of the American Medical Association (JAMA Cardiology).

About 65,000 patients a year are investigated for heart attacks in New Zealand emergency departments, yet only about 15% of them are actually having a heart attack.  New Zealand leads the world in having become the first country in the world in which all patients are assessed by an accelerated diagnostic pathway that enables rapid evaluation of the patients and can send people home after two blood tests taken two to three hours apart (see here for more).  This means many patients who once-upon-a-time would have been admitted to hospital overnight, are now able to be reassured after 4-6 hours that they are not having a heart attack and can go home.  Nevertheless, there are enormous advantages for both patient and health system to being able to come to the conclusion that the pain isn’t life threatening earlier. The cork in the bottle preventing this happening is the time it takes for a blood sample to be analysed for signs of damage to the heart. These blood tests typically take 1 to 2 hours from the time of sampling (within ~15 minutes of arrival in the ED) until the results are available for the doctor to review.  Because doctors are dealing with multiple patients at a time, their review and decisions around whether to allow the patient to go home, or to be admitted for more investigation, are further delayed.  A point-of-care test is one that happens with a small machine near the bedside and can produce results available to the doctor even while they are still examining the patient.  Until now, though, the precision of these machines has not been good enough to be used in emergency departments.  When one manufacturer told us that their new technology may now have sufficient precision we were keen to test it,  so we, in a first-in-the-world study, undertook a study in patients entering the emergency department of Christchurch hospital whom the attending doctor was investigating for a possible heart attack.

Thanks to the volunteer patients (I love volunteers) who gave some extra blood we measured the troponin concentration by this new point-of-care test (called the next generation point of care troponin I: TnI-Nx). Troponin comes from the heart muscle and is released into the blood during a heart attack. When the troponin concentrations in the blood are very very low we can be confident that the source of the patient’s discomfort is not a heart attack.  Low concentrations require a very precise measurement test. Often, a very low concentration means the patient can safely go home. In 354 volunteers we measured troponin with the TnI-Nx assay when they first came to the emergency department.  Their treatment didn’t change, and all clinical decisions were based on the normal laboratory based troponin (measured on entry to the emergency department and again 2 hours later). From the blood samples we collected and measurements we made, we could work out what could have happened if we had used the TnI-Nx results instead.

In our study the TnI-Nx troponin measurement was as good as, and possibly slightly better, than the laboratory based troponin measurement at ruling-out a heart attack. We found 57% of the patients being investigated had troponin concentrations measured with TnI-Nx below a threshold at which we could be confident that they were not having a heart-attack.  All 57 patients who were actually having a heart attack had higher concentrations.

When implemented our results may mean that instead of waiting 3-6 hours for a results, half of patients being investigated could know within about 30 minutes of arriving at the ED whether they are having a heart attack or not.  This early reassurance would be a relief to many, as well as reducing over-crowding in the emergency department and freeing up staff for other tasks.  But before we implement the new test, we must validate it in more patients – this is a study we are carrying out now.  Validation will enable us to more precisely determine a threshold concentration for TnI-Nx for clinical use which we can, with a very high degree of certainty, safely use to rule-out a heart attack.

The test also should allow people living in rural areas to get just as good care as in emergency departments because it could be deployed in rural hospital and general practices.  This would save many lengthy, worrying, and expensive trips for people to an urban emergency department.

This study was carried out by the Christchurch Emergency Department research group (director and senior author Dr Martin Than) in conjunction with the Christchurch Heart Institute (University of Otago Christchurch).  My colleague, Dr Joanna Young did much of the hard yards, and we thank our clinical research nurses and assistant for all they did to take blood samples, collect data, and lend a hand around the ED.  The manufacturer of the blood test, Abbott Point-of-care, provided the tests free of charge, but they were blinded to the results and all analysis was conducted independent of them.

How we envisage TnI-Nx may be used in the future to allow very early rule out of heart attacks

Please note – patients experiencing sudden onset chest-pain should always seek immediate medical attention.

I am fortunate to hold a Senior Research Fellowship in Acute Care sponsored by the Canterbury Medical Research Foundation, the Emergency Care Foundation, and the Canterbury District Health Board which enables me to participate in these studies.

ps.  You’ll have to read some of my older posts if you want to know why “Cheesecake files”

 

The Treatment of Kidney Failure in New Zealand

I am delighted to introduce a guest post from Dr Kelvin Lynn. Dr Lynn worked as a Nephrologist at Christchurch Hospital for 35 years and retired in 2015.  He is the lead author for a book just published:

The Treatment of Kidney Failure in New Zealand

Authors: Kelvin L Lynn, Adrian L Buttimore, Peter J Hatfield, Martin R Wallace 2018

ISBN PDF – 978-0-473-45293-3

Available at no charge at www.kidneys.co.nz/Kidney-History from 16 October 2018.

Dr Kelvin Lynn and his fellow editors tell the history of the treatment of people with kidney failure in New Zealand; beginning in the early 1950s this story encompasses remarkable experiences of patients and their families, and of the contributions made by dedicated health professionals. It also reveals the challenges and ethics of meeting an ever-increasing demand for treatment.

New Zealand doctors were early adopters of new dialysis technology. The first peritoneal dialysis (PD treatment in New Zealand occurred at Wellington Hospital in 1954. Two young doctors tried a recently reported treatment using homemade equipment – classic Number 8 wire technology. Dr Neil Turnbull was a medical registrar in 1954 when he admitted a pale, vomiting, dehydrated 24-year-old woman who had not passed urine for the past nine days. Fifteen days before admission she had tried to terminate an unwanted pregnancy by infusing a Dettol solution into her cervical canal. In spite of rehydration with blood and five per cent glucose she became comatose. It was then that pathology registrar, Dr Dave Reid, suggested trying PD, which he had recently read about in the New England Journal of Medicine.  After mixing 20 litres of a glucose solution in sterilised glass bottles they had to stop as the solution had caramelised. They supposed the autoclave (steriliser) had been too hot and were proved right when after the autoclave temperature was reduced the new glucose solution remained clear. This was not the end of their technical problems, however, for after running two litres of the solution through the polythene tube that they had inserted into the right iliac fossa with a trocar and cannula, there was no drainage. Undeterred, they pulled the tube out and established good drainage by pricking holes in the tubing with a hot 22-gauge needle. After three days of peritoneal dialysis the patient began passing increasing volumes of urine and then regained consciousness. When last seen by Turnbull in 1992, she had normal renal function.

This book recounts the contribution of doctors, nurses, technicians, and patients and their families to the story of kidney treatment in New Zealand. Social and political changes in our country since the 1950s have critically influenced the development of treatment services for New Zealanders with kidney failure. The improvements in technology and community expectations regarding access to treatment over the past 50 years are discussed as well as the issues for patients and families coming to terms with kidney failure and its treatment.

This story is illustrated with many anecdotes and historical photographs.

  • The experience of living a life with kidney failure is recounted from patient interviews.These stories are a testament to the bravery and determination of these individuals. Rob Brydon’s story demonstrated what ordinary people were able to do in the face of kidney failure.

Rob began home haemodialysis on 31 August 1976 just after getting married. After two failed transplants, the second from his brother Nev, he remains on HHD over 40 years later.  Most of this time, he worked full-time. Following redundancy in 1993, he started his own painting business which he ran for ten years until he had both legs amputated below the knee, bringing this to an end. Rob had a profound anaemia as the result of having both his kidneys removed to control his high blood pressure. He built his own house while his haemoglobin concentration was only 40 to 50 g/L, and subsequently Rob was one of the first patients in New Zealand to benefit from erythropoietin treatment for renal anaemia. Rob remembers the burden of having to reuse dialysers and blood lines and the unpleasantness of using formalin for sterilisation. His advice to other dialysis patients is to “try to keep your life as normal as possible.”

  • There are chapters devoted to the professional development of renal nurses and dialysis technicians who have played a key role in the progress made in kidney treatment. Nurses were important members of the early clinical teams who pioneered dialysis treatment. Now renal nursing is an established nursing specialty. Hospital technicians who maintained the early dialysis equipment quickly took up clinical roles, particularly in training patients for dialysis at home.
  • There is an account of the trends and statistics of dialysis treatment in the past and a chapter discussing where dialysis treatment may go in the future.

The first home dialysis machine used in New Zealand Drake Willock 4011 1972

Enquiries to kidneyhistory@gmail.com