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

Networks vs districts

After only five-and-a-half months, our Local Health Networks (LHNs) in New South Wales are being rebranded again*. It seems that the new NSW government has decided to make its mark on the health service by fiddling with semantics. The Health Services Amendment (Local Health Districts and Boards) Act 2011 was proclaimed on 16 May and appears primarily to rebrand LHNs as “Local Health Districts” and LHN Governing Councils as “Local Health District Boards”.

Sydney Local Health District

Presumably the new terminology is intended to further evoke localism and the memory of hospitals being governed by local hospital boards. The legislation does not, however, appear to introduce any material changes to the structure/function of the health service. Hm… Well I guess we’ll be getting another new set of stationery…

* The original Area Health Services were amalgamated (and renamed) on 1 January 2006. Under the National Health and Hospitals Network agreement, the Area Health Services were demerged (mostly to the pre-2006 boundaries) and renamed Local Health Networks on 1 January 2011.