Getting it right.  Diagnosing true infections in the NICU.  It matters!

Getting it right. Diagnosing true infections in the NICU. It matters!

The scenario is often the same.  Faced with a child born to a mother with risk factors for sepsis you decide to start antibiotics.  The time comes closer to 36 – 48 hours when you must decide whether or not to continue.  Each time we examine our results and look at cultures and try to do what is right.  Yet defining right is sometimes hard for so many.  If we had 100% sensitivity and specificity for all our tests it would be easy but we don’t.  So what can we do?

If I had to have one wish though it would be that we could improve upon our diagnostic accuracy when it comes to treating suspected infections in the newborn.  As health care providers we have an extremely loud inner voice trying to tell us to minimize risk when it comes to missing a true bacterial infection.  On the other hand so much evidence has come forth in the last few years demonstrating that prolonging antibiotics beyond 48 hours is not just unwise in the absence of true infection but can be dangerous.  Increased rates of necrotizing enterocolitis is just one such example but other concerns due to interfering with the newborn microbiome have arisen in more recent years.  What follows are some general thoughts on septic workups that may help you (and myself in my own practice) as we move ahead into the New Year and may we cause less harm if we consider these.

The Role of Paired Blood Cultures

Although not published by our centre yet, we adopted this strategy for late onset sepsis a couple years back and have seen a significant reduction in work-ups deemed as true infections since adoption.  While the temptation to do only one blood culture is strong as we have a desire to minimize skin breaks consider how many more there will be if you do one culture and get a CONS organism back.  There will be several IV starts, perhaps a central line, repeat cultures etc.  If you had done two at the start and one was positive and the other negative you could avoid the whole mess as it was a contaminant from the start.  On my list of do no harms I think this may have the greatest benefit.

The Chest X-Ray Can Be Your Friend

While I am not a fan of routine chest x-rays I do believe that if you are prepared to diagnose an opacification on a chest x-ray as being due to a pneumonia (VAP or in those non-ventilated) that you need to follow this up with a repeat x-ray 24 – 48 hours later.  rdsIf the opacity is gone it was atelectasis as a true pneumonia will not clear that easily. Well worth the radiation exposure I say.

If You Are Going To Do a Work-up Make It A Complete One

We hear often in rounds the morning after a septic work-up that the baby was too sick to have an LP and that we can just check the CSF if the blood is positive.  There are two significant problems to this approach.  The first which is a significant concern is that in a recent study of patients with GBS meningitis, 20% of those who had GBS in the CSF had a negative blood culture.  Think about that one clearly… relying on a positive culture to decide to continue antibiotics may lead to partially treated GBS meningitis when you discontinue the antibiotics prematurely.  Not a good thing.  The second issue is that infants with true meningitis can have relatively low CSF WBC counts and may drift lower with treatment. Garges et al in a review of 95 neonates with true meninigits found that CSF WBC counts >21 cells per mm3 had a sensitivity of 79% and specificity at 81%.   This means that in those with true meningitis 19% of the time the WBC counts would be below 21 leading to the false impression that the CSF was “fine”.  If antibiotics were effective it could well be by 48 hours that the negative CSF culture you find would incorrectly lead you to stop antibiotics.  Message:  Do the CSF sampling at the time of the septic work-up whenever possible.

If We Aren’t Prepared To Do a Supra Pubic Aspirate Should We Not Collect Urine At All?

This provocative question was asked by a colleague last week and is based on the results of a study which was the topic of the following post: Bladder Catherterizations for UTI: Causing more harm than good?  The gist of it is that it would appear that in many cases the results of a catheter obtained urine cannot be trusted.  If that is the case then are we ultimately treating infections that don’t actually exist when the only positive culture is from a urine.  I believe using point of care ultrasound to obtain specimens from a SPA will be the way to go but in the meantime how do we address the question of whether a UTI is present or not?  May need to rely on markers of inflammation such as a CRP or procalcitonin but that is not 100% sensitive or specific either but may be the best we have at the moment to determine how to interpret such situations.

Lastly, Slow Down And Practice Good Hand Hygiene

So much of what I said above is important when determining if an infection is present or not. The importance of preventing infection cannot be understated. Audits of hand hygiene practice more often than not demonstrate that physicians are a group with some of the lowest rates of compliance. Why is that? As a physician I think it has nothing to do with ignorance about how to properly perform the procedure but rather a tendency to rush from patient to patient in order to get all the things done that one needs to do well on service or call. If we all just slow down a little we may eventually have less need to run from patient to patient as the rate of infections may drop and with it demand for our time.

If slowing down is something that you too think is a good idea you may want to have a look at the book In Praise of Slowness by Carl Honore (TED Talk by Carl Below)  which may offer some guidance how to do something that is more easily said than done. Here is hoping for a little slower pace in the new year. We could reap some fairly large benefits!

 

Bladder Catheterization For UTIs: Causing more harm than good

Bladder Catheterization For UTIs: Causing more harm than good

It is one of the first things that a medical student pledges to do; that is to do no harm. We are a fearful lot, wanting to do what is best for our patients while minimizing any pain and suffering along the way. This is an admirable goal and one which I would hope all practitioners would strive to excel at. There are times however when we can inadvertently cause more harm than good when we try to avoid what we perceive is the greater harm.
This is the case when it comes to collecting a sample of urine for culture as part of a full septic workup. If you ask most healthcare providers they will freely acknowledge that the gold standard for determining whether an infant has a UTI is a supra pubic aspirate (SPA). We so rarely do them these days however due to a whole host of reasons. Problems with collection include the timing and accuracy of needle placement both of which may often lead to an empty tap.  Secondly after a number of missed attempts and a crying infant who appears to be in pain it is understandable why bedside nurses may become frustrated with the entire experience and urge the person performing such procedures to settle on a bladder catheterization (BC) to obtain the specimen.

The Study That Compares BC and SPA Head to Head

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A recent Turkish study by Eliacik K et al published A Comparison of Bladder Catheterization and Suprapubic Aspiration Methods for Urine Sample Collection From Infants With a Suspected Urinary Tract Infection and should give us all cause for concern.  The authors performed SPA on 83 infants under 12 months with a positive urine culture by BC but who had not yet started antibiotics.  The outcome of interest was both the comparison with the culture result and to see if urinalysis from the BC could increase the strength of the information gleaned from a BC.

All in all the BC performed quite poorly when compared to the gold standard.  The false positive rate compared to SPA was 71.1%! That is to say that only 28.9% of SPA samples were positive compared to BC.  Similarly urinalysis sensitivity and specificity from BC were 66.7% (95% CI, 44.68% to 84.33%) and 93.22% (95% CI, 83.53% to 98.08%), respectively.  This means that only 2/3 of the time was the urinalysis abnormal on a BC in the presence of a true UTI.  Somewhat reassuring is that when there really was no UTI the urinalysis was mostly negative but in almost 1/10 patients it would not by itself rule out a UTI.

What Is The Harm in Continuing BC Instead of SPA?

When we try to avoid the perceived painful experience of a SPA we are going to wind up treating a large number of patients for a presumed UTI who don’t have one.  The harm in this is the exposure of such infants to prolonged courses of antibiotics which has been a subject discussed many times over on this site.  We put our patients at risk of antibiotic resistance and shifts in the gut microbiome which in the case of the preterm infant puts them at risk of necrotizing enterocolitis.  There are many other concerns with prolonging antibiotics but these few should be reason enough to strive for accuracy in obtaining the right specimen in the right way.  Putting it in a slightly different perspective, would you settle for an alternative test to a lumbar puncture which claimed to miss 1 in 10 cases and also found meningitis where there was none 71.1% of the time?!

A Way Forward – A Recipe For Success

As the saying goes, measure twice and cut once.  With the use of bedside ultrasound there should be no need to guess as to whether the bladder is full or not.  Secondly the placement of the needle should no longer need to rely on landmarking but actually seeing where the best place for needle placement is.  Assessing the bladder by ultrasound is easy and is already employed at the bedside by nurses in many areas of the hospital.  There should no longer be a reason for the empty tap as the practitioner can be called when the baby is ready as evidenced by a good amount of urine in the bladder.

Given that we have some time to do the blood culture and LP, while we wait for the SPA to be done either sucrose in the premature infant or IV analgesic may be given for the SPA while in the term or older infant there is an opportunity to put a topical analgesic cream over the site.  There really is little need for pain to factor into this any longer.

Ask any health care provider and they will tell you they want to do the best they can for their patient.  This study shows us that performing a BC is failing to meet that goal.  We need to change our ways and return to the practice of the SPA but this time we have to get it right.