Alas, Abscesses [heart] Antibiotics

“Fake news!” All you need for effective treatment for abscesses is an incision and drainage procedure – adjunctive antibiotics are just unnecessary exposures with only marginal benefit, at best.

Then, unfortunately, two trials have been published in the New England Journal of Medicine showing benefit for antibiotics – either trimethoprim-sulfamethoxazole or clindamycin – improve the rate of clinical cure. The magnitude of benefit was somewhere in the range of a number needed to treat between 7 and 14, with infrequent harms, suggesting the balance of benefit may favor antibiotics. However, the abscesses included in these study tended to be large, suggesting perhaps these results weren’t easily generalizable.

This is a subgroup analysis of one of these two studies, trying to dredge out a specific population for whom antibiotics weren’t actually of value. And, unfortunately, for the purists among us, the results are bleak. Accounting for the diminishing statistical power and reliability of such an analysis, there are few useful signals within these data. Neither the size of the abscess nor the area of surrounding erythema reliably predicted diminishing returns from adjunctive antibiotics, nor did presence of fever or comorbid illness. The only probably reliable signal in these data, consistent with results in the era prior to MRSA, shows antibiotics are probably unnecessary for those who are not infected with staphylococci. Unfortunately, until that point where the causative agent can be easily ascertained at the time of I&D procedure, these data aren’t terribly useful in a practical sense.

So, the benefit is not universal, but it’s nothing at which to scoff. Perhaps a delayed antibiotic strategy could be considered, but, it seems most patients ought be offered antibiotics following drainage of a clinically significant abscess.

“Subgroup Analysis of Antibiotic Treatment for Skin Abscesses”

CT (Almost) Never Before LP

The guidelines describing the patients with suspected bacterial meningitis for whom neuroimaging is indicated prior to lumbar puncture are quite broad. The Infectious Disease Society of America includes virtually every imaginable mental status or immune system impairment, and guidelines in Europe are similar. The anachronistic concern: cerebral herniation in the setting of increased intracranial pressure leading to an otherwise potentially avoidable death. But, guidelines in Sweden are different. In Sweden, their neuroimaging guidelines suggest only those virtually comatose or with focal neurologic signs should undergo CT prior to LP.

In this review of patients with acute bacterial meningitis from a Swedish registry, the authors attempt to parse out whether a decision to perform CT is not only unnecessary – but also potentially harmful. They analyze 815 patients ultimately diagnosed with bacterial meningitis and stratify them by those who received LP without CT, LP before CT, and CT before LP. Presenting features and comorbid medical conditions were abstracted retrospectively, and the results were analyzed with respect to the varying guideline recommendations, mortality, and functional outcomes.

The clear winner: CT rarely before LP, as in Sweden. By their guidelines, only ~7% of those ultimately diagnosed with bacterial meningitis had indication for CT prior to LP – but, unfortunately, 52% of patients underwent imaging anyway. The reason for “winning” if adherent to the Swedish strategy, however, was not just reduced resource utilization – it was mortality and functional outcomes. Mortality was almost halved in those for whom Swedish guidelines were followed, only rarely CT prior to LP. The authors attribute the signals for the underlying mortality difference to a greater percentage of patients receiving antibiotics within 1 hour or 2 hours when no CT was performed.

This probably overstates the magnitude of harm relating to CT use, as delays in antibiotics are probably more accurately delays in diagnosis, rather than logistics impacting timely delivery of antibiotics. After all, even in those with LP prior to CT, only 41% received steroids plus adequate antibiotics, so I expect the magnitude of effect seen here likely ties more reliably to confounding individual patient factors not easily adjusted for in a retrospective analysis.

That said, I do think the Swedes are doing the right thing – the vast majority of CTs were unhelpful. Their guidelines for neuroimaging – deep coma and/or lateralizing neurologic signs – will probably pick up any relevant findings (like the subdural empyema in this series), and reduce waste while obviating any possible delays in care.

“Lumbar puncture performed promptly or after neuroimaging in adult bacterial meningitis: A prospective national cohort study evaluating different guidelines”

Enough with the Coughing!

Every Emergency Physician who has worked a night shift knows this all too well – the child brought to the ED in the middle of the night for a cough, keeping the entire family up, and the cough has been going on for weeks.

And, the not-at-all-satisfying answer: “This is pretty normal.”

This is yet another publication describing the natural history of symptoms following an upper respiratory illness. These authors in Australia enrolled children evaluated in the Emergency Department for an upper respiratory infection featuring cough. They enrolled 839 children and attempted to follow them for four weeks after the index visit, as well as through follow-up with a pulmonology specialist if seen for persistent, unresolving cough. Nearly 300 of the initially enrolled cohort was lost to follow-up over the course of the month, but of those who were contacted, two-thirds still had cough at 7 days, and a quarter were still coughing at day 21. Ultimately 171 – or 20.4% – were still coughing at day 28 and eligible for pulmonologist evaluation. Of these, about a third were identified to have a previously undiagnosed underlying chronic respiratory disorder (asthma, bronchiectasis, etc.) and about half were given the diagnosis of persistent bacterial bronchitis.

The general takeaway here is that coughs generally linger – but once a cough has persisted beyond 2-3 weeks, it is reasonable to consider alternative precipitating diagnoses other than the initial URI.

“Chronic cough postacute respiratory illness in children: a cohort study”

Steroids, Not Universally Useful For Wheezing

In asthma, steroids are fantastic. The earlier, the better. In bronchiolitis, another wheezing-spectrum illness, mostly probably not. How about the general, ambulatory, viral lower respiratory tract infections with wheezing?

This randomized, controlled trial enrolled patients at family practice clinics in Britain with non-asthmatic wheezing relating to a suspected “chest infection”. Patients received either 40mg of oral prednisolone for five days or matching placebo. The primary outcome was duration of moderately bad or worse cough, as recorded by a patient-reported symptom diary, with secondary outcomes of subsequent antibiotic use, cumulative symptom scores, and quality of life scores, and other resource utilization measures.

These authors enrolled 401 patients, 398 of whom received the study intervention. There were no important differences between enrolled groups at baseline – and, there were no reliable, important differences in measured outcomes, either the primary symptom-related outcome, or any of the secondary outcomes.

The strength of this evidence is not such that it eliminates the possibility of a clinically important benefit for a subgroup of patients, but I consider it practice-changing because there was such little reliable evidence at baseline. I have certainly felt it was reasonable to discharge patients with suspected viral LRTI, wheezing, and bronchospasm on an oral steroid based on a low risk profile and at least a hoped-for, physiologically-justified, benefit. Now, the onus is on a subsequent trial to demonstrate said benefit before resuming such practice.

“Effect of Oral Prednisolone on Symptom Duration and Severity in Nonasthmatic Adults With Acute Lower Respiratory Tract Infection”

Predicting Treatment Failure in AOM

Like most infectious diseases, acute otitis media generally breaks down into three cohorts. There are viral infections, for which early antimicrobial therapy is virtually, by definition, unhelpful. Then, there are true bacterial infections – many of which resolve without substantial morbidity regardless of antimicrobial treatment, and those which require antimicrobial therapy to prevent such. The trick, and where modern medicine typically fails miserably, is rapidly predicting into which of these cohorts a patient may fall – a conundrum leading to the epidemic of antibiotic overuse.

This is a secondary analysis of a pediatric AOM trial, first published in the New England Journal of Medicine, looking at which patients were more likely to potentially fail conservative treatment. The intervention arm received amoxicillin/clavulanate, and treatment failure occured in 31.7% of children – vastly favoring the antibiotic arm – 44.9% vs. 18.6%. In theory, this exaggerated treatment effect might help better illuminate any small predictors – but, unfortunately, with only 319 patients, meaningful statistical significance on this data dredge is hard to come by. Worse still, the best predictor of treatment failure (or, really, lack thereof)? A peaked tympanogram (A and C curves) – you know, because we’re all routinely measuring tympanometry. Grossly bulging tympanic membranes were predictive of treatment failure, which has some face validity, at least – but, again, this is as compared between severe, moderate, and mild, which requires pneumatic otoscopy to differentiate.

The question here primarily concerns: can you take away good conclusions from bad data? The magnitude of the treatment effect seen in this trial far exceeded the treatment effect expected from antibiotics in other trials. And, consistent with that questionable generalizability, their findings reflect the stringent criteria determining their diagnosis of AOM. Then, they are relying upon their misguided definition for treatment failure, which relies on otoscopic signs, the same ones that will be colinear with worsened disease on initial examination. Unfortunately, the net result of all of this meandering is essentially no clinically useful insight. Considering the limitations the examination of the screaming ill toddler, more pragmatic approaches are necessary.

“Prognostic Factors for Treatment Failure in Acute Otitis Media”

I&D Alone or With Antibiotics for the Little Guys

Most physicians provide adjunctive antibiotic therapy for large abscesses following incision and drainage – the sorts where you need a bucket and a hose. Less clear has been the small abscess – but, in the age of MRSA, the fear factor has led many to cover these, regardless. Recent evidence suggests there is a small absolute benefit to antibiotic use and clinical cure, with an NNT around 14, along with other apparent benefits regarding re-infection and spread to household contacts. These trials, however, still enrolled patients with abscesses much larger than typically encountered in routine practice.

This trial is specifically designed to break the glass on “smaller skin abscesses” – just like in the title! What does small mean to these authors? It means a suppurative cavity of 5cm in diameter, or, up to the size of a cupcake:
abscess cakeSo, before we even start, we can see we may end up with issues regarding generalizability to many of the abscesses we encounter in the Emergency Department.

This trial is comprised of three arms – clindamycin, trimethoprim-sulfamethoxazole, and placebo – and enrolled 786 patients in an attempt to detect a 10% difference between arms while accounting for 20% attrition rate. The primary outcome was test of cure at 10 days after therapy, with a variety of secondary outcomes, including new infections at one month and treatment-related adverse events.

The winner, if one can be crowned, was not placebo. At the test of cure visit in the intention-to-treat population – and likewise, the population that could be evaluated – placebo lagged behind both clindamycin and TMP-SMX by approximately a 12% absolute magnitude of difference. Recurrent infections at the same site, or another site, were lowest in the clindamycin group at 6.8% – and similar between TMP-SMX and placebo, at 13.5% and 12.4%, respectively. However, clindamycin was implicated in the highest rate of adverse events, at 21.9%, compared with TMP-SMX and placebo, at 11.1% and 12.5%, respectively. Most of the difference in adverse events can be attributed to diarrhea illness, although clostridium difficile was not isolated in any cases. There was one case of systemic hypersensitivity reaction thought to be related to TMP-SMX.

There were two main drivers for the difference in test of cure between the placebo cohort and the two antibiotic cohorts, and these were use of rescue antibiotics during the follow-up period and new infections at another site. The use of rescue antibiotics is not necessarily a reliable measure of treatment failure, but it is still reasonable to suggest this difference would not arise by chance alone, despite the small sample. Regarding generalizability to practice, the minority of abscesses were cupcake-sized, but these were still fairly substantial infections. The median size of the abscess was about 2.2cm in diameter, with surrounding erythema of 5.9cm in greatest dimension.

The takeaway, then, hinges on the generalizability of their population to your individual patient. If these are “smaller” skin abscesses, then I wager the bulk of my abscess encounters are for “tinier” abscesses. I doubt this changes much current practice with regard to antibiotics, or antibiotic selection, for those treating abscesses in the 2+cm range, but I expect the differences in cure rates shrink for smaller lesions. It falls within the realm of acceptable practice variation to weigh the harms of antibiotic use with the chance of recurrence or new infection for those lesions.

“A Placebo-Controlled Trial of Antibiotics for Smaller Skin Abscesses”

Double Coverage, Cellulitis Edition

The Infectious Disease Society Guidelines are fairly reasonable when it comes to cellulitis. Non-suppurative cellulitis – that is to say, without associated abscess or purulent drainage – is much less likely to be methicillin-resistant s. aureus. The guidelines, therefore, recommend monotherapy with a ß-lactam, typically cephalexin. Conversely, with a suppurative focus, trimethoprim-sulfamethoxazole monotherapy is an appropriate option. However, it’s reasonable to estimate current practice involves prescribing both agents somewhere between one fifth and a quarter of cases – presumably both wasteful and potentially harmful. This trial, therefore, examines this practice by randomizing patients to either double coverage or cephalexin plus placebo.

The short answer: no difference. The rate of clinical cure was a little over 80% of both cohorts in the per-protocol population. Of those with follow-up and treatment failure, over half progressed to abscess or purulent drainage on re-evaluation – and about two-thirds were cultured out as s. aureus. There was no reliable evidence, however, co-administration of TMP-SMX prevented this progression.

The really fun part of this article, however ties into the second line of their abstract conclusion:

“However, because imprecision around the findings in the modified intention-to-treat analysis included a clinically important difference favoring cephalexin plus trimethoprim-sulfamethoxazole, further research may be needed.”

This hedging stems from the fact 17.8% were excluded from the enrolled cohort for inclusion in the per-protocol analysis – and, depending on the modified intention-to-treat analysis definition, there was actually up to a 7.3% difference in failure rate favoring double coverage (76.2% vs 69.0%). This resulted from almost twice as many patients in the cephalexin monotherapy cohort taking <75% of antimicrobial therapy, missing follow-up visits, or other protocol deviations.

The best Bayesian interpretation of this finding is probably – and this is where frequentism falls apart – simply to ignore it. The pre-study odds of dramatic superiority of double coverage are low enough, and the outcome definition for the modified intention to treat cohort in question is broad enough, this finding should not influence the knowledge translation of this evidence. Stick with the IDSA soft-tissue guidelines – and one antibiotic at a time, please.  It is important to recognize – and educate patients – that about 1 in 6 may fail initial therapy, and these failures to not necessarily reflect inappropriately narrow antibiotic coverage nor therapeutic mismanagement.

“Effect of Cephalexin Plus Trimethoprim-Sulfamethoxazole vs Cephalexin Alone on Clinical Cure of Uncomplicated Cellulitis”

Blood Cultures Save Lives and Other Pearls of Wisdom

It’s been sixteen years since the introduction of Early Goal-Directed Therapy in the Emergency Department. For the past decade and a half, our lives have been turned upside-down by quality measures tied to the elements of this bundle. Remember when every patient with sepsis was mandated to receive a central line? How great were the costs – in real, in time, and in actual harms from these well-intentioned yet erroneous directives based off a single trial?

Regardless, thanks to the various follow-ups testing strict protocolization against the spectrum of timely recognition and aggressive intervention, we’ve come a long way. However, there are still mandates incorporating the vestiges of such elements of care –such as those introduced by the New York State Department of Health. Patients diagnosed with severe sepsis or septic shock are required to complete protocols consisting of 3-hour and 6-hour bundles including blood cultures, antibiotics, and intravenous fluids, among others.

This article, from the New England Journal, looks retrospectively at the mortality rates associated with completion of these various elements. Stratified by time-to-completion following initiation of the 3-hour bundle within 6 hours of arrival to the Emergency Department, these authors looked at the mortality associations of the bundle elements.

Winners: obtaining blood cultures, administering antibiotics, and measuring serum lactate
Losers: time to completion of a bolus of intravenous fluids

Of course, since blood cultures are obtained prior to antibiotic administration, these outcomes are co-linear – and they don’t actually save lives, as facetiously suggested in the post heading. But, antibiotic administration was associated with a fraction of a percent of increased mortality per hour delay over the first 12 hours after initiation of the bundle. Intravenous fluid administration, however, showed no apparent association with mortality.

These data are fraught with issues, of course, relating to their retrospective nature and the limitations of the underlying data collection. Their adjusted model accounts for a handful of features, but there are still potential confounders influencing mortality of those who received their bundle completion within 3 hours as compared to those who did not.  The differences in mortality, while a hard and important endpoint, are quite small.  Earlier is probably better, but the individual magnitude of benefit will be unevenly distributed around the average benefit, and while a delay of several hours might matter, minutes probably do not.  The authors are appropriately reserved with their conclusions, however, only stating these observational data support associations between mortality and antibiotic administration, and do not extend to any causal inferences.

The lack of an association between intravenous fluids and mortality, however, raises significant questions requiring further prospective investigation. Could it be, after these years wandering in the wilderness with such aggressive protocols, the only universally key feature is the initiation of appropriate antibiotics? Do our intravenous fluids, given without regard to individual patient factors, simply harm as many as they help, resulting in no net benefit?

These questions will need to be addressed in randomized controlled trials before the next level of evolution in our approach to sepsis, but the equipoise for such trials may now exist – to complete our journey from Early Goal-Directed to Source Control and Patient-Centered.  The difficulty will be, again, in pushing back against well-meaning but ill-conceived quality measures whose net effect on Emergency Department resource utilization may be harm, with only small benefits to a subset of critically ill patients with sepsis.

“Time to Treatment and Mortality during Mandated Emergency Care for Sepsis”

Symptoms Over Science

There’s a reason general primary care has evolved to diagnose and treat uncomplicated urinary tract infections over the phone: the patient is the authority, not any test we order.

We’ve tried relying upon some constellation of the urinalysis, the urine microscopic examination, and, finally, the urine culture. Each of these has limitations, although, in many settings, the culture result has been the gold standard. However, this culture result, some quantification of the number of colony-forming units, is also somewhat of an arbitrary diagnostic – an arbitrary numerical cut-off must be used, with its own implications for sensitivity and specificity.

This brief clinical microbiology article evaluates the urine culture as a gold standard for the diagnosis of UTI by comparing it with polymerase chain reaction-based methods for measuring the presence of pathogenic bacteria. Based on 86 asymptomatic women and 220 general practice women complaining of UTI symptoms, these authors compared the number of positive culture results with positive PCR results. Of this sample, 149 had positive cultures for e. coli, while 211 patients had positive PCR for e. coli. Finally, combining the culture results – which identified other pathogens, as well – with the PCR for e. coli, 216 of 220 symptomatic women had pathogenic bacteria identified. In the control cohort, there were similar numbers of positive culture and PCR results – ~10% in each, which these authors feel accurately reflects the general rate of asymptomatic bacteruria in the general population.

These data correlate nicely with similar findings demonstrating a negative urine culture does not exclude clinical improvement while on antibiotics, and thus the reasonable conclusion we ought simply treat appropriate symptomatic patients without specifically relying on testing.

“Women with symptoms of a urinary tract infection but a negative urine culture: PCR-based quantification of Escherichia coli suggests infection in most cases”

Vitamin C for Sepsis

This is just a quick post in response to a tweet – and hype-machine press-release – making the rounds today.

This covers a before-and-after study regarding a single-center practice change in an intensive care unit where their approach to severe sepsis was altered to a protocol including intravenous high-dose vitamin C (1.5g q6), intravenous thiamine (200mg q12), and hydrocortisone (50mg q6). Essentially, this institution hypothesized this combination might have beneficial physiologic effects and, after witnessing initial anecdotal improvement, switched to this aforementioned protocol. This report describes their outcomes in the context of comparing the treatment group to similar patients treated in the seven months prior.

In-hospital mortality for patients treated on the new protocol was 8.5%, whereas previously treated patients were subject to 40.4% mortality. Vasopressor use and acute kidney injury was similarly curtailed in the treatment group. That said, these miraculous findings – as they are exhorted in the EVMS press release – can only be considered as worthy of further study at this point. With a mere 47 patients in both treatment groups, a non-randomized, before-and-after design, and other susceptibilities to bias, these findings must be prospectively confirmed before adoption. When considered in the context of Ioannidis’ “Why Most Published Research Findings Are False”, caution is certainly advised.

I sincerely hope prospective, external validation will yield similar findings – but will likewise not be surprised if they do not.

“Hydrocortisone, Vitamin C and Thiamine for the Treatment of Severe Sepsis and Septic Shock: A Retrospective Before-After Study”