REMI 2001. Bacteriemia por Pseudomonas aeruginosa: ¿monoterapia o tratamiento combinado?

Artículo original: Effect of adequate single-drug vs combination antimicrobial therapy on mortality in Pseudomonas aeruginosa bloodstream infections: a post Hoc analysis of a prospective cohort. Peña C, Suarez C, Ocampo-Sosa A, Murillas J, Almirante B, Pomar V, Aguilar M, Granados A, Calbo E, Rodríguez-Baño J, Rodríguez F, Tubau F, Oliver A, Martínez-Martínez L; Spanish Network for Research in Infectious Diseases (REIPI). Clin Infect Dis 2013; 57(2): 208-216. [Resumen] [Artículos relacionados] [Texto completo]
      
Introducción: La combinación de antibióticos en las infecciones graves puede tener dos objetivos: 1) ampliar el espectro y/o la cobertura antimicrobiana, de manera que se reduzca la posibilidad de dejar sin cubrir el microorganismo causal; 2) tratar un microorganismo difícil con dos antibióticos, para, consiguiendo un efecto sinérgico o al menos aditivo, aumentar la efectividad de la antibioterapia. Muchos estudios sobre tratamiento antibiótico combinado no han distinguido claramente estos dos objetivos, lo que les resta utilidad y validez. En el caso particular de las infecciones por Pseudomonas aeruginosa, la elevada tasa de resistencias (tabla I) [1] obliga a considerar siempre el primer objetivo (p. ej.: prescribir dos antibióticos potencialmente activos, para asegurarse de que al menos uno lo es); respecto al segundo objetivo, tradicionalmente se ha considerado que "dos antibióticos activos es mejor que uno", pero la evidencia en este sentido es controvertida [2-4].
      
Resumen: En un análisis post-hoc de un estudio de cohortes realizado en 10 hospitales españoles en pacientes con un primer episodio de bacteriemia monomicrobiana por Pseudomonas aeruginosa se estudió la influencia sobre la mortalidad a los 30 días del uso de uno o dos antibióticos activos, empíricamente y como tratamiento definitivo. Se incluyeron 593 pacientes, con una mortalidad del 30% a los 30 días, y del 13% en las primeras 48 horas. Se realizó análisis multivariable, que incluyó un índice de propensión para recibir tratamiento antibiótico combinado. Solo el 56% recibieron un tratamiento empírico adecuado (al menos un antibiótico activo), y de ellos solo el 20% recibió tratamiento activo con dos antibióticos. No se encontraron diferencias en la mortalidad ni en el análisis crudo ni en el ajustado entre los pacientes tratados empíricamente con cero, uno o dos antibióticos activos, ni entre los que recibieron tratamiento definitivo (tras conocer el antibiograma con la CMI) con cero, uno o dos antibióticos activos. No se encontró ningún subgrupo en el que el tratamiento combinado fuera más efectivo.
      
Comentario: El estudio, a pesar de ser el mayor publicado hasta ahora de bacteriemia por PA, no resuelve la controversia entre tratamiento único o combinado. Como los autores señalan, el principal inconveniente para evaluar la eficacia de un tratamiento en un estudio observacional es que los tratamientos no se prescriben al azar, sino de acuerdo a las características del paciente; el intento de corregir este sesgo mediante análisis multivariante y análisis de propensión es la mayoría de las veces insuficiente, y exige en todo caso un tamaño muestral muy alto, que en el caso de la bacteriemia por PA es difícil de conseguir. En este estudio los tratamientos combinados se usaron en pacientes de mayor riesgo, como es lógico, y no se pudo probar una mayor supervivencia con el tratamiento combinado; de hecho ni siquiera se pudo probar que un tratamiento antibiótico "adecuado" (activo) fuera más eficaz que uno "inadecuado" (no activo). La hipótesis planteada (dos mejor que uno) requiere un ensayo clínico de tamaño suficiente para poder resolverla.

Tabla I. Bacteriemia por Pseudomonas aeruginosa: resistencia a antibióticos [1]


Antibiótico
% de resistencia
Ceftazidima
23,7
Cefepima
38,4
Aztreonam
98,4
Piperacilina-tazobactam
27,9
Imipenem
32,1
Meropenem
30,1
Ciprofloxacino
34,2
Levofloxacino
37,4
Gentamicina
21,1
Tobramicina
18,4
Amikacina
6,3
Colistina
1,1
190 casos, año 2008, de 10 hospitales españoles

Eduardo Palencia Herrejón
Hospital Universitario Infanta Leonor, Madrid.
© REMI, http://medicina-intensiva.com. Octubre 2014.

Enlaces:
  1. Overexpression of AmpC and efflux pumps in Pseudomonas aeruginosa isolates from bloodstream infections: prevalence and impact on resistance in a Spanish multicenter study. Cabot G, Ocampo-Sosa AA, Tubau F, Macia MD, Rodríguez C, Moya B, Zamorano L, Suárez C, Peña C, Martínez-Martínez L, Oliver A; Spanish Network for Research in Infectious Diseases (REIPI). Antimicrob Agents Chemother 2011; 55(5): 1906-1911. [PubMed] [Texto completo
  2. β-Lactam plus aminoglycoside or fluoroquinolone combination versus β-lactam monotherapy for Pseudomonas aeruginosa infections: a meta-analysis. Vardakas KZ, Tansarli GS, Bliziotis IA, Falagas ME. Int J Antimicrob Agents 2013; 41(4): 301-310. [Resumen
  3. Impact of definitive therapy with beta-lactam monotherapy or combination with an aminoglycoside or a quinolone for Pseudomonas aeruginosa bacteremia. Bliziotis IA, Petrosillo N, Michalopoulos A, Samonis G, Falagas ME. PLoS One 2011; 6: e26470. [PubMed] [Texto completo]
  4. Impact of adequate empirical combination therapy on mortality from bacteremic Pseudomonas aeruginosa pneumonia. Park SY, Park HJ, Moon SM, Park KH, Chong YP, Kim MN, Kim SH, Lee SO, Kim YS, Woo JH, Choi SH. BMC Infect Dis 2012; 12(308). [PubMed
Búsqueda en PubMed:
  • Enunciado: Tratamiento antibiótico de la bacteriemia por Pseudomonas aeruginosa
  • Sintaxis: "pseudomonas aeruginosa"[mh] AND bacteremia[mh] AND "anti-bacterial agents"[mh] 
  • [Resultados]
           

Soft neck collar to replace hard – times are a changin!

image from http://www.actimed.com.au/images/products/collar.jpg (no conflicts of interest exist)

We have posted about this growing controversy of prehospital cervical spine neck collars previously since last year, when UK prehospital faculty published a consensus statement , highlighting lack of evidence for hard neck collars and raising concerns of harm being done. Since then Norwegian and Dutch ambulance protocols have shown signs of change to modify or even eliminate the use of hard neck collars in prehospital setting.

Via my PHARM network I had heard in my own state of Queensland, Australia, that one Brisbane hospital/ED had changed to using soft neck collars and remarkably that the QUeensland Ambulance Service was planning to remove all hard neck collars and replace with soft neck collars.

When the QAS SOP and EBM review are published online by QAS/Queensland Health I will post it up but its clear the decision has been made and rollout implementation will be soon underway. For now most QAS units still  use hard neck collar as per current SOP but the soft neck collar SOP will be phased in, in near future.

To be honest, whilst seemingly radical decision, I support it fully!

Times are a changin!

Whats your opinion?

 


Filed under: Prehospital medicine Tagged: hard, neck-collars, soft

Predicting survival after avalanches

More than 150 people die each year after being buried in an avalanche, and mortality is greater than 50% for this condition. Unfortunately, a large amount of resources are used on patients who ultimately expire, so determining which ones are likely to survive can safe costs and allow better utilization of resources such as extracorporeal life support (ECLS) warming and air evacuation.

Of the 3 common causes of cardiac arrest after avalanche, only hypothermia is likely to have good outcomes. Trauma and hypoxia have poor outcomes. Most algorithms have providers stop resuscitation for severe trauma, and airways packed with snow. However, ascertaining hypoxia vs hypothermia is less obvious. Prior attempts used potassium >10 mmol/L or >12 as a surrogate marker for cellular death from hypoxia, but no other markers are used.

So these authors took 20 years of data from the North French Alps, which ended up being only 48 patients with cardiac arrest.  18 of them had ROSC pre-hospital, and only of those 2 were eligible for ECLS. 19 of the 30 without ROSC were also eligible for ECLS. In total, only 8 survived, 5 from the pre-hospital ROSC group, and 3 from the non-ROSC. Of the 8 survivors, only 3 had favorable neurologic outcomes.

All of these were patients with rescue collapse, that is loss of vital signs after extrication or transfer. 3 other patients with rescue collapse died however. Other indicators for survival in their analysis are the presence of a rescue pocket, K <4.3 (nobody survived above 4.2, but some nonsurvivors had levels below this), and coagulation disturbances. Interestingly, their data showed no overlap of prothrombin time between survivors and non-survivors, but they sadly did not give the values, only as ratios. Other values such as PaO2, PaCO2, lactate, and bicarb are not predictive.

Unfortunately, for such a long time period of collections, there were very few survivors. The retrospective nature also limits analysis. It does look like we need to reduce the cutoff for resuscitation from values of K from 10-12 mmol/L to a lower number (7?). Also, identification of coagulation abnormalities may help. Perhaps POC thromboelastograms may be a way to identify those that do not merit resuscitation.

Survival after avalanche-induced cardiac arrest
http://www.ncbi.nlm.nih.gov/pubmed/24971508

The post Predicting survival after avalanches appeared first on EBM Gone Wild.

Back pain…

Back pain is one of the most frequent complaints in the ED.  The vast majority of patients do not have a life threatening or highly morbid pathology.  Unfortunately, this patient did:

 

CT LSpine 1 LS spine 2

This is a CT scan under bone windows.  It shows erosive changes based around the L4-L5 disc, eroding into the inferior endplate of L4 and the superior endplate of L5. These findings are concerning for discitis-osteomyelitis. It is favored to have both acute
and chronic components.

Finding this pathology is somewhat like finding a needle in a haystack.  However, pay attention to signs such as fever, repeat ED visits without a firm diagnosis, focal weakness, and predisposing factors such as IV drug abuse, history of endocarditis, or immunosuppression.  Sedimentation rate and C-reactive protein are often elevated in this disorder (among others).

CT is a readily available, quick way to diagnose this pathology but it isn’t as sensitive as MRI.  Plain films are not reliable but may show changes similar to the CT above.  Nuclear medicine bone scans as well as PET scans can be used but are not commonplace in the ED.

Author:  Russell Jones, MD

Image Contributor:  Zachary Skaggs


Filed under: CT, Non-Trauma, Orthopedics Tagged: Discitis, Osteomyelitis

Ultrasound Leadership Academy: Introduction to Ultrasound

By Michael Macias

By Michael Macias

Welcome to the Ultrasound Leadership Academy (ULA) summary blog series. I just recently joined the ULA which is essentially an online advanced ultrasound education experience put on by the team from Ultrasound Podcast which brings cutting edge learning to emergency medicine personnel through a variety of interactive platforms including video lectures, google hangouts with experts, simulation, live conferences and real time scanning with a pocket-sized ultrasound device known as a Vscan.

Over the next year I will be posting summaries of the key learning points from my experience. If you want to learn more about the program you can visit Ultrasound Leadership Academy or Ultrasound Podcast to see more from the hosts of this awesome program.


Introduction

The idea of performing ultrasound in the emergency room isn't that new. We can trace back its history to a radiologist by the name of Golderberg in the 70s, who had the outlandish idea of injecting saline into the abdomens of cadavers and using an ultrasound to detect it. Here in lied the birth of the FAST exam.

But ultrasound in the emergency room isn't simply an extension of the physical exam. We don't bring it along and slap in on everyone's abdomen or chest just to take a peak inside. We can think of Emergency Ultrasound as something slicker and a bit more tailored, designed to answer a specific question. 

Emergency Ultrasound should be:

  • Performed for a clearly defined condition (Is there a pericardial effusion?)
  • A focused, goal-directed exam (I am not going to scan this persons entire body.)
  • Characterized by 1-2 features (Is there fluid around the heart? Is the RV collapsing?)
  • Easily learned and performed (I am not going to determining the exact EF of a patient.)
  • Quick (You have 10 other patients your seeing, let's make this quick.)
  • Have a direct impact on patient care (A urgent pericardiocentesis may save this patient's life)
  • Point of Care (At the beside, reliable and available) 

Ultrasound Machine 

Choosing the right ultrasound machine can be difficult. Ultimately if you want to incorporate ultrasound into your practice you need to find what purposes you will be using it for, what features you must have and also think about how much money you can spend.

Some features to consider:

  • Image quality (This will often be synonymous with more money but you need to also consider additional features such as M-mode)
  • User interface (Mac vs Windows...same concept, make sure your interface shows you want to want to know when scanning)
  • Boot and battery (Are you in an office or a ED? What is the battery life like?)
  • Transducers (You need a linear and phased array probe at minimum)
  • Connectivity (What are you going to do with your images? How do you want to export them? Wired vs wireless?)
  • Durability/Service (Are you going to destroy your US machine? May want to consider something sturdy...In-house service versus ship out?..cost plays into this as well) 

Transducers

All transducers were not made equal. 

The transducer

The transducer

  • Piezoelectric crystals- Vibrate to generate sounds waves which will go out to hit tissue and bounce back and be converted to electric signal and thus an image

  • Matching layer- Allows easy transmission of sound waves just as US jelly does 

  • Backing material- Dampening agent that gives time for the PZT crystals to 'listen' for return signal

High Frequency

  • High resolution
  • Shallow penetration
  • Vascular access
  • DVT
  • Skin/MSK/small parts
  • Linear or intracavitary probes

Low Frequency

  • Low resolution
  • Deep penetration
  • Abdominal imaging
  • Pleural spaces
  • Curvilinear or phased-array probes

Physics

1 minute synopsis I promise. 

  • Frequency: Number of cycles over a period of time measured in Hertz (cycles/second)
  • Period- Time from beginning of wave to the end 
  • Wavelength: Distance from beginning of wave to the end (which is inversely proportional to period)
  • Amplitude: Height of the wave

Take Home: Long wavelength will penetrate deep into body and have low resolution since it cannot discriminate between closes structures while short wavelength will penetrate shallow and discriminate highly between close structures. 

Speed: US travels through different mediums at different speeds. This will be important when thinking about artifacts created during scanning. 

  • Air 500 m/s -> Soft Tissue 1540 m/s -> Bone/Solids 3000 m/s

Pulsed Ultrasound: Most of the time the ultrasound is listening for returning echoes. For example, a pulse may be sent from PZT for 1 msec and will listen for the next 999 msec for returning sound waves. 

Time = Distance: The US machine determines how far from probe objects are based on the time it takes for sound wave to return after hitting that object. 

More terminology: Make sure you know how to describe what your seeing.

  • Near field: Half of US screen closest your probe.
  • Far field: Half of US screen farthest from your probe.
  • Hyperechoic: Appears bright and white which means that it contains high calcium content such as bone/stones/tendons. 
  • Anechoic: Appears black on screen which means it is fluid or artifact known as shadowing
  • Grey areas: The inbetween. Describe these areas with respect to surrounding tissue

Knobology 

The art of turning knobs. There are several knobs that we need to know how to use to make our images look better but first a quick look at probe terminology.

   

Knob Lingo:

  • Gain: This determines overall brightness. Optimal gain allows for proper distinction of structures while too much gain leads to artifact
  • Time Gain Compensation: This allows you to vary the gain according to depth. For instance you may have a bright structure in the near field and want to see the far field. You can preferentially turn down gain in the near field or turn up gain in the far field independently. 
  • Depth: This determines essentially how long the US machine will listen for returning signals. Make sure to decrease depth to optimally characterize necessary structures. Your point of interest should be in the middle of the screen ideally. 
  • Focus: This allows you to heighten resolution of particular depth within the particular view on your screen. If this doesn't matter then place focus at bottom of the screen. 
  • Modes: Different modes serve a particular function
    • B Mode/2-D/Grey scale is our standard mode. 
    • M Mode stands for motion mode which allows us to look at a particular line of interest on the screen and observe this line over time
    • Color doppler analyzes fluid flow towards and away from probe and displays this as a color gradient.
    • Power doppler is useful for presence of absence of flow but does not show direction.
    • Pulsed Wave doppler is useful for fluid velocity, assessing hemodynamics and cardiac function. 

Artifacts

These are tricky little things. In a nutshell, artifacts are structures that don't represent true anatomic structures.

  • Shadowing:Represent areas where acoustic signal is not penetrating. This is not limited to bony structures but rather anything with a high calcium content, such as those gallstones you're seeing in the gallbladder.
  • Reverberation: Ultrasound pulse strikes tissue and bounces back to transducer and then back into tissue and back to transducer again taking 2x,3x,4x as long making it seem as if there are multiple similar appearing structures. This is often seen when evaluating the pleural surface. Since these are in multiples, the distance between each artifact should be equal.
  • Edge artifact: This occurs as a result of refraction as wave changes medium from air-sold or air-fluid interface leading to shadowing behind structure as sound waves at bent in a different direction. This is often seen along the edge of the gallbladder, do not confuse this with a gallstone shadow. 
  • Acoustic enhancement: This results from the fact that when ultrasound waves travel through fluid there is not as much attenuation as compared to tissue. Therefore tissue deep to fluid filled structures will appear brighter. You may see this when looking at the bladder or gallbladder.
  • Ringdown: This is in essence a very rapid reverberation and is often seen with metallic objects or pulmonary edema. For example, b-lines seen in pulmonary edema are actually constructed of very tightly bound horizontal lines. 
  • Mirror image: This is often seen around the heart or the diaphragm. When an ultrasound beam hits the diaphragm it reflects off and changes direction, hits tissue, bounces back and hits diaphragm and then returns back to transducer. Remember that time = distance so therefore the machine will assume that this object is past the diaphragm given the time it took to return. When you see a mirror image of liver on the other side of the diaphragm this lets us known that there is no consolidation or fluid in the lung base. 

That's it for this week.

If you are interested in learning more about the ULA learning experience, visit their website below:

  ULA_logo_1.png  

If you are interested in purchasing eBooks 'Introduction to Bedside Ultrasound', Volume 1 & 2, from Dr. Mallin and Dr. Dawson, for less than $1, visit Ultrasound Podcast Consumables.


More Resources:

Just Roll With It.

  This was a 17-yo male with no PMH who presented to the ED complaining of decreasing visual acuity in his left eye that had been worsening over the past month. It had progressed to the point where he could only differentiate between light and dark. He felt like a ‘curtain was falling’ when he tried to see through his left eye. He denied trauma, environmental exposures, prior vision problems, photophobia, eye discharge or eye redness.   While awaiting the ophthalmology consult, a point-of-care ocular ultrasound was performed and the following video clip was obtained. Image courtesy of Dr. Shiu Lin Tsai.   Thank you for playing! Answers and explanations will be posted in a few days. If you want to see YOUR image included in the next Image of the Month, please email interesting stills and/or clips in addition to a small blurb on the patient to Lorraine Ng at  PEMFellowscom@gmail.com.