eGFR vs CrCl

Estimated glomerular filtration rate (eGFR) and creatinine clearance (CrCl) are often, incorrectly, used interchangeably when discussing renal function and drug dose adjustment.

Creatinine clearance, usually estimated using the 1976 Cockcroft-Gault formula rather than actually measured by (notoriously unreliable) 24-hour urine collection, has traditionally been used for drug dosing as it is relatively standardised despite overestimating renal function due to tubular secretion of creatinine. In addition to the usual caveats associated with basing renal function estimates on serum creatinine (acute illness, muscle mass, diet, etc), accuracy of the formula is limited by changes to serum creatinine assays and the rise in obesity since 1976.

Renal function is assessed nowadays using formula-derived eGFR (actual GFR is impracticable to measure routintely). Until recently this was usually calculated using the MDRD formula (1999), which has been well validated but has limited accuracy above 60 mL/min. Laboratories in Australia now report eGFR calculated using the superior CKD-EPI formula (2009). Although both of these formulae give better estimates of true renal function (GFR) than CrCl, they are both still based on serum creatinine with its associated caveats above.

Some studies have shown a reasonable concordance between CrCl (Cockcroft-Gault) and eGFR (MDRD) with respect to drug dosing,1 whereas others have noted significant differences.2–3 At the end of the day, CrCl and eGFR are not the same thing and prescribers should remain vigilant as to which measurement has been used to formulate dosage adjustment recommendations.

References:
1. Stevens LA, et al. Am J Kidney Dis 2009;54:3342
2. Wargo KA, et al. Ann Pharmacother 2006;40:124853
3. Park EJ, et al. Ann Pharmacother 2012;46:117487

Biotechnology descriptors

Whilst giving a presentation at grand rounds recently, I noted that approved names for biological medications in Australia are suffixed with a three-letter abbreviation – the “biotechnology descriptor” – to indicate the biotechnology production system used, e.g. insulin lispro (rbe).

The most common biotechnology descriptors are:

  • ghu – gene-activated human cell line
  • rbe – recombinant bacteria Escherichia coli
  • rch – recombinant Chinese Hamster ovary cell line
  • rmc – recombinant mouse cell line
  • rys – recombinant yeast Saccharomyces cerevisiae

Incidentally, I cringe whenever someone refers to this group of medications as “biologics” – an Americanism that has crept into the Australian medical lexicon. Australian English still retains the “-ical” ending (rather than shortening to “-ic” in American English), therefore we should continue to refer to these medications as “biologicals”.

A day in the life of a medical registrar

14 new patients post-take (1 DOA)
7am consultant rounds
Interviewed by the police
Discussion with an Assistant Coroner
Rescued from a difficult dilemma by one of the geriatricians (again)
Spoke with the hospital Director of Medical Services
AWOL patient urinating on the hospital front lawn
Challenging discussions with families about end-of-life issues
Asked for two consults at 4pm (because my consultant specifically wanted me to ask)
Somehow didn’t get shouted at for the late consults
Finished my ward round after-hours
Left the hospital at 7.30pm

… and very grateful for my fantastic intern Angela!

Leeches in modern medicine

Leeches have been used medicinally for centuries, with their most well-known role in the former practice of blood-letting. In modern medicine, however, the medicinal leech (Hirudo medicinalis) has found a niche role in plastic/reconstructive surgery where it can be used to reduce venous congestion and encourage microcirculation.

medicinal leeches

medicinal leeches

Specially prepared leeches are attached to the relevant part (e.g. at-risk surgical flap) and allowed to feed. Once gorged they detach themselves and are collected for re-use. Heparin wipes may be used at the bite site to prolong the therapeutic anticoagulation effect.

medicinal leeches

At our centre, collected leeches are prepared for re-use by placing in them saline – apparently this encourages them to regurgitate their initial feed. Subsequent feeds are less effective, so after 1-2 feeds the leech is “retired” using concentrated saline and flushed down a sluice sink.

Outdoor smoking bans in NSW

Amendments to the Smoke-free Environment Act 2000 (NSW) will come into force next week, further restricting tobacco smoking in public areas in New South Wales.

Smoking is already banned in enclosed public areas in NSW.

From 7 January 2013, smoking will also be banned in the following outdoor places:

  • within 10 metres of children’s play equipment in outdoor public places
  • public swimming pools
  • spectator areas of sports venues
  • public transport stops/platforms (including bus stops and taxi ranks)
  • within 4 metres of entrances to public buildings

Furthermore, from 6 July 2015 smoking will also be banned in commercial outdoor dining areas (i.e. al fresco).

Australia is a world leader in tobacco harm reduction. It’s good to see further action being taken to protect public health through reducing exposure to second-hand smoke.

More information: health.nsw.gov.au/tobacco/Pages/smokefree-areas-faq.aspx

My colonial medical elective

Now that I’ve finally completed the Sydney Medical Program, it’s about time that I finally post some long-overdue reflections on my elective terms in London and Hong Kong at the start of the year.

The Royal London Hospital (Barts and The London, QMUL)

The Royal London Hospital

My first elective term was spent at The Royal London Hospital under Barts and The London School of Medicine and Dentistry (Queen Mary, University of London). The Royal London Hospital is a 650-bed tertiary hospital and the principal facility of the Barts and The London NHS Trust. It is particularly known as one of London’s major (level one) trauma centres and the home of the London Air Ambulance (Helicopter Emergency Medical Service), however a full range of medical and surgical specialties are represented.

Drs Po and Preston

I was assigned to the gastroenterology team under consultant gastroenterologist Dr Sean Preston. He was an excellent supervisor and I was lucky to have spent quite a lot of time under his guidance during my elective. Dr Roocroft (the F1 house officer) was also a great mentor, teaching me the ins and outs of being a house officer in the NHS.

Work casual

Work attire in NHS hospitals is very appropriately guided by infection control considerations. In summary:

  • no tie
  • sleeves rolled-up to elbows
  • no watch (most male doctors wear their watch on their belt)

The Royal London Hospital

The logic (and comfort) of this policy was such that I continued with this after returning to Sydney, where it was still convention for male doctors to wear ties.

Speaking English

There were a few differences in the medical vocabulary used in the UK, which took a little while for me to get used to. The most prominent ones during my elective were:

bleeper – pager
phlebotomy – venepuncture
OGD (oesophageogastroduodenoscopy) – endoscopy
TTA (to take away) – discharge summary

EastEnders

I alluded in a previous post that I lived in hospital accommodation. Indeed I found myself living in John Harrison House, The Royal London Hospital, Whitechapel E1 2DR for the duration of my stay in London. Whilst relatively cheap (approx. £100/week), it was rather spartan. One of the other JHH residents described living there as punishment for his sins, whilst more colourful language was employed by one of the senior registrars.

One of the unexpected consequences of living in Whitechapel, with its majority non-white population, was the difficulty I had in trying to find a decent full English breakfast. Despite there being half a dozen (halal) fried chicken shops on Whitechapel Rd alone, there were very few decent cafés in the area. Spotting a modern-looking café on New Rd advertising that they served “English breakfast”, I stepped into Zaza’s Café (E1 1HJ)… only to realise that they served a halal version of English breakfast: smoked turkey, beef sausage, egg, baked beans, mushroom & toast. It wasn’t bad, but it’s just not the same! Thereafter I quickly learnt the Arabic characters for halal (حلا).

Queen Mary Hospital (HKU)

My second elective term was spent at Queen Mary Hospital under the Faculty of Medicine, The University of Hong Kong. Queen Mary Hospital (est. 1937) is a 1400-bed tertiary hospital and the principal facility of the Hong Kong West Cluster, with a catchment area population of over 500,000 people.

Queen Mary Hospital, Hong Kong

I was attached to a final-year group undertaking their Specialty Clerkship rotation. This works rather differently from the way our attachments work during clinical years – instead of being attached to a specific medical/surgical specialty team for the duration of a clinical attachment, each group of HKU students is allocated to one general medical ward where they’re expected to clerk patients (with seemingly little direct role in patient care). They take part in case discussions, PBL tutorials, and clinics with consultants from different specialties over the course of the term. Often ward-based tutorials were quite crowded, particularly with the confined spaces inside most hospital wards in Hong Kong (see pic below – I wasn’t standing at the back).

Ward tutorial, QMH

Masquerade

I was in Hong Kong during the 2009 influenza H1N1 “swine flu” pandemic. Following their experience during the SARS epidemic, all Hong Kong hospitals had activated what they termed “pandemic emergency response level E2″. One of the E2 requirements was that a surgical face mask was required in all clinical areas – effectively meaning that staff/students had to wear surgical masks all day!

Emergency E2 clinical attire

White coat syndrome

In total contrast to NHS policy, Hong Kong clinical attire convention was still very conservative and included the wearing of a “clean, white laboratory coat”. I’d never previously worn a lab coat in the clinical setting, but noticed two advantages: (i) it was handy having large pockets in which to put my stuff (e.g. Oxford Handbook of Clinical Medicine), and (ii) I got my student/staff discount at the hospital cafeteria and Starbucks without having to show any ID. Nevertheless, once I returned to Sydney I greatly appreciated not having to wear a lab coat.

HKU Specialty Clerkship group a/b, 2010 rotation 1

Finally, I’d like to take this opportunity to acknowledge and thank the Specialty Clerkship group to which I was attached – Fifian, Jimi, James, Vincent, Rosemary, Edgar and Sha Sha – for helping me to fit-in and manage the language barrier.