Tag Archives: Intensive Care Unit

Cheesecake files: Of bathtubs and kidneys

Sitting in the bathtub you notice that there is a slow leak around the plug.  You adjust the taps to maintain a flow of water that exactly counteracts the loss due to the leak; the water level stays constant.  This is called a steady state and the same thing happens with out kidneys and the molecule used to assess their function.  Our bodies generate creatinine at a constant rate which finds its way into the blood.  Under normal circumstances our kidneys excrete that creatinine into the urine at the same constant

rate.  The creatinine concentration in the blood, therefore, stays constant.  When our kidneys get injured (as they very often do in hospitalised patients) this is like plugging the leak.  Just as the water level in the bathtub would rise slowly – undetectable at first – so too does the creatinine concentration rise slowly.  It normally takes a couple of days to be noticed.  Most of my work has been about trying to detect this injury to the kidney early.  However, if the kidneys start to recover then excess creatinine is only slowly cleared from the blood by the kidney – a process that similarly can take a day or two before it is detected.  Just as not knowing if the kidneys have been harmed makes treatment and drug dosing difficult for the nephrologists and intensivists, so too is not knowing if they have recovered.  My latest publication (aka a cheesecake file) that has appeared in press presents a simple tool for the physicians to try and determine if kidney function has recovered after having been compromised.

This particular piece of work began when a St Louis Nephrologists (a kidney doc), Dr John Mellas, contacted me to say that although a manuscript of his had been rejected by reviewers, he thought there was merit and could I help him (he found me through a search of the literature).  I confessed to being one of the reviewers who had rejected the manuscript!  Fortunately, John was forgiving.  His problem was that he was called in to the intensive care unit to look at a patient with high blood creatinine concentration.  Should he put the patient on dialysis or should he wait?  If he knew if the kidney was already recovering, then he would be less likely to put on dialysis. We talked about the issue for a while and eventually settled on a possible tool which we could test by looking at the behaviour of creatinine over time in abut 500 patients in the ICU.  The tool is quite simple.  It is the ratio of the creatinine that is excreted to the creatinine that is generated.  If more creatinine is being generated than excreted then probably the kidney function is still below normal, however, if more is excreted than generated then probably the kidney is recovering.  The difficulty is that there is no way to measure in an individual what the creatinine generation is.  We ended up using equations based on age, sex, and weight to estimate creatinine generation.  This is a bit like using an equation which takes into account pipe diameter, mains water pressure, and how many turns of the screw the tap has had to determine the rate of water flow.  Creatinine excretion, though, can be easily measured by recording total urine production over several hours (we suggest 4h) and multiplying this by the concentration of creatinine in the urine.

We discovered that by using the ratio between estimated creatinine generation and creatinine excretion we were able to tell in most patients if the kidney was recovering or not.  My hope is that physicians will test this out for themselves.  The good thing is that it requires only minimal additional measurements (and costs) beyond what are already made in ICUs, yet may save many from expensive and invasive dialysis.

Pickering, J. W., & Mellas, J. (2014). A Simple Method to Detect Recovery of Glomerular Filtration Rate following Acute Kidney Injury. BioMed Research International, 2014. doi:10.1155/2014/542069

 

Does being unconscious mean you should miss out?

The front page of the Herald this morning questions the participation of unconscious patients in clinical trials.

While I understand Auckland Women’s Health Council co-ordinator Lynda Williams unease, I also detected a failure to understand the process of how progress in medicine is made.

First, all research in such cases is approved by ethics committees which include lay people and patient advocates. That is clear in the article. In my experience they are very very thorough at ensuring the best interests of patients are highest priority. Family or whanau consent is almost always required (especially if the research involves an intervention*). These are the same family or whanau who are talking with medical staff and, at times, providing consent for medical interventions.  When a person is vulnerable it is up to all around them to treat them with respect and care.  Offering them, through their family, the opportunity to participate in research is showing respect for them as a valued member of society who is prepared to give in the interests of others.  Indeed, it is a right of the patient, through their family, to be offered such research.

Second, without such research there can be no progress in medical treatment of unconscious critically ill patients. In order to save lives interventions must be made at critical junctures during the progress of a disease, normally at the earliest possible time. It is in the best interests of us all that such research take place. The alternative is to give up hope and allow current mortality rates to remain as they are. I research a disease (Acute Kidney Injury) which affects 1 in 3 people in the Intensive Care Unit and increases their chances of dying about 4 times. There is no treatment and it is devilishly difficult to detect in the early stages. An estimated 2 million a year die because of Acute Kidney Disease. Without the generosity of family and friends allowing trialling of an intervention (always based on years of prior research and judged to be possibly efficacious) there will be no progress and the death toll will remain high. I salute family and patients around the world who have participated in such studies in the past, and will do so in the future.

Disclaimers: 1. I have no knowledge or understanding of the antiobiotic trial under discussion.  2. I have been involved in an intervention study where participants were unconscious at the time consent was obtained.

*Note, there are some circumstances where when minutes count an intervention is required.  Research in these areas is ethically more difficult, but no less necessary.  I welcome public debate in this area.  While ethics committees can deal with ensuring minimisation of harm in such circumstances, we do need to decide as a society what sacrifices of individual rights we should make for the greater good.

Two new Health Research Council grants worth crowing about

This week’s announcement by the HRC of Feasibility Study and Emerging Researcher grants have many great projects.  Two in particular are worth crowing about (because they have some relationship to kidneys and they involve two excellent people).  I have put summaries in their own words below, but first my comments.

Dr Palmer (Department of Medicine, University of Otago Christchurch), who has appeared on this blog site before, conducts what in the trade are called “meta-analyses” and “systematic reviews.”  Simply put, these are methods to extract the best possible evidence from all the studies that have been done for the effectiveness of a treatment.  Just as one person may toss a coin 4 times in a row and get 4 heads, so too can any one trial give a mistaken impression that a treatment is efficacious (or not) when it really isn’t (or is).  By pooling together many treatments Suetonia provides the very best quality evidence available.  Given that Chronic Kidney Disease affects a large and growing proportion of us, knowing which treatments have the best outcomes is of national significance, not merely to our health but also to the national budget.  A particular problem is that after a trial it can be many many years until meaningful health outcomes are know (e.g. if the treatment delays dialysis need or reduces mortality).  Suetonia’s study will assess the effectiveness of surrogate endpoints for clinical trials.  Surrogate endpoints, such as plasma creatinine which I’ve discussed many time in this blog, are physiologically related to the functioning of an organ or to a disease state as well as statistically associated with future hard outcomes.  However, their use in trials is limited by how well they are associated and how they are used.  I look forward to finding out what Suetonia discovers.

Mrs Rachael Parke (Auckland DHB) is an experienced nurse undertaking a PhD. Ensuring patients have adequate fluids on board is particularly crucial to the kidneys and other organs. Obviously with surgery any blood loss needs to be compensated for. However, there are also physiological changes in where fluid is distributed throughout the body.  Cardiopulmonary bypass, used in cardiac surgery, is a particular risk factor for Acute Kidney Injury. In the past the practice has been to give large amounts of fluid in order to ensure adequate fluid is given.  However, recent research has shown that too much fluid can have a negative impact (increased mortality).  A more restrictive fluid regime may have very meaningful outcomes.  Rachael is investigating, in a randomised controlled trial, if restricting fluid improves outcomes.  The outcome she is most interested in is how long patients stay in the hospital.  This is a very practical outcome for both patient and budget.  I am particularly pleased that this study is nurse-led.  Nurses play an incredibly important role in research as well as patient management.

In their own words:

Dr Suetonia Palmer: Making better clinical decisions to prevent kidney disease

More than ten percent of adults will develop chronic kidney disease. The effectiveness of many treatments used to improve outcomes in kidney disease is tested against surrogate (indirect) markers of health (e.g., cholesterol levels or blood pressure).

Unexpectedly, subsequent systematic analysis has identified little evidence to show that treatment strategies based on these surrogate markers translate to improved health for patients. Serum creatinine and proteinuria levels are commonly-used markers of kidney function to guide treatment.

The research involves using systematic review methods to summarise the quality of evidence for using proteinuria and serum creatinine as markers of treatment effectiveness in clinical trials. It will be determined whether using these markers to guide clinical care improves patient health or, conversely, leads to treatment-related harm or excessive use of ineffective medication.

These summaries will help clinicians and patients make better shared decisions about which therapeutic strategies actually improve clinical outcomes in kidney disease.

Mrs Rachel Parke: Fluid therapy after cardiac surgery – A feasibility study

Following cardiac surgery, patients receive large amounts of fluid in the intensive care unit. This may cause problems with wound healing and delay hospital discharge. A planned randomised controlled trial of a restrictive fluid regime as compared to a more liberal approach utilising advance hemodynamic monitoring, aims to reduce the amount of fluid patients receive and reduce hospital length of stay. This feasibility study aims to determine whether this nurse-led protocol is practicable and feasible and will help answer the research question. This study is simple and inexpensive and if it demonstrates a decreased length of hospital stay then this will represent a significant benefit for both individual patients and the health system.