Shutting down the infection superhighway

By Nick Pryke and Ian Clover

With ventilated patients being unable to communicate, ventilator-associated pneumonia (VAP) can become a difficult infection to identify. Marc-Oliver Wright and Ongjen Gajic discuss strategies to cut off the germ invasion caused by ventilator-associated pneumonia.

“When we shove a tube past all the cilia that we have in our trachea, we're basically opening up the 'autobahn' to organism. That's the first problem: You're doing something that your body doesn't want to.”
-Ongjen Gajic

Healthcare systems worldwide are in a perpetual struggle to eliminate hospital-acquired infections (HAIs) - no mean feat considering the phenomenal range of infection sources patients are potentially exposed to as soon as they cross the threshold of a hospital or clinic. Developing countries undoubtedly find themselves at the lower end of the success curve, but for developed countries, the battle remains just as aggressive. That battle becomes all the more poignant when it's on behalf of patients who are unconscious and dependant on staff and equipment for their survival.

At NorthShore University HealthSystem, the Director of Infection Control, Marc-Oliver Wright, understands how to battle on behalf of his patients - and with an average mortality rate of between two to three percent of all HAIs, that understanding can quite literally save lives. "I'd say a relatively conservative estimate would be at least somewhere between four and 10 percent of all people who are hospitalized will have had an HAI sometime during their stay," says Wright.

Ongjen Gajic, who is the Associate Professor of Medicine at the College of Medicine at Mayo Clinic, agrees that HAIs are a huge worldwide and US problem, and that their impact on the healthcare system is costly. "Worldwide, approximately 1.5 million people at any time have HAIs, with close to 100,000 cases in the United States, which is obviously a huge figure. Estimates place the costs to the US healthcare system at $5 billion annually, some $15,000 per infection."

Gajic concedes that VAP is the most common of all HAIs, pointing out that one in 10 patients who need to be placed on a ventilator for longer than 24 hours will, on average, develop VAP.

"VAP is also one of the most deadly HAIs," agrees Wright. "Yet determining whether a patient has VAP is a very difficult thing to do. In the last couple of years, American medical literature has proposed that VAP is a very poor quality metric, as the subjectivity of assessing who has VAP differs from individual to individual. The Centers for Disease Control and the National Healthcare Safety Network definition for VAP shows that the inter-observer reliability is incredibly poor. That makes it extremely difficult to give an accurate picture of what we look at when we try to define it.

"If you look at some of the national data from the National Healthcare Safety Network, we're talking somewhere between two and five VAPs for every 1000 ventilator days, but within some of the published literature those rates vary quite widely. One of our nation's leading experts typically reports that rates are far higher than what we see in the National Healthcare Safety Network. VAP is one of the most subjective HAIs that we try to measure in infection control, and it makes it exceptionally difficult."

Hard to identify

Indeed, trying to identify whether a patient has contracted VAP when they're unable to communicate certainly has its challenges. In order to diagnose or assume VAP, the medical staff must therefore have a sound comprehension of why VAP would occur in the first place: Any invasive medical device by its very nature - from a ventilator tube to a catheter - bypasses the body's natural protective barrier. When this happens, the potential for problems becomes very real.

"When you insert a peripheral IV into someone's arm, it damages the skin, which is there to keep organisms out of the body and out of the blood stream," explains Wright. "VAP is even worse because your entire respiratory system from your nose and mouth down to your lungs is aligned with protective benefits. When we shove a tube past all the cilia that we have along our trachea, we're basically opening up the 'autobahn' to organisms. That's the first problem: You're doing something that your body doesn't want to. That being said, sometimes it's medically necessary. One of the best things you can do is to get that tube out of there as quickly as possible - that's the first and most obvious element."

Gajic agrees. "The key issue is, the longer the tube is in, the worse it is for the patient. Prolonged endotracheal intubation is the critical risk factor for death. The normal barriers of your mouth and nose have been breached by the tube and, obviously, defences are lowered so bacteria from the external surroundings can enter a patient's lungs."

"Then you have oral contamination," continues Wright, "where someone who is chronically ventilated has a lack of mouth hygiene. It's not like you and I who get up in the morning and brush our teeth, gargle with Listerine and evacuate the organisms inside our mouths. Oral hygiene is incredibly important and if it's not well maintained you start to get a build-up of organisms in the mouth that eventually work their way down that super-highway directly into the lungs.

"Other things can include the manipulation of the catheter - whether we're suctioning, adjusting it or trying to extubate a patient - any time we come into contact as a healthcare worker with a tube that's going down into the patient's chest, we basically have to make sure that our hands are clean and that we're not contaminating the endotracheal tube and not giving organisms a chance to get well and truly down there."

"Strict control measures in hospitals are the most important achievable preventative strategy we can adopt," says Gajic. "Easy isolations include controlling pathogen transmission through hand hygiene and other contact precautions, so 100 percent hand washing, in and out, is imperative. Other steps we can take include decreasing the duration of endotracheal intubation as much as possible - weaning and sedation protocols had us worried that we were retracting the tube too early, but we have learned that we were usually being very conservative. Stricter protocols, such as early ambulation, the use of non-invasive ventilation and wearing masks help decrease the exposure and duration of endotracheal intubation, so the conduit between mouth and lungs is not in situ for too long a time."

Another effective option is to make sure that a ventilated patient, if medically feasible, is sufficiently elevated. Essentially, position is critical to aiding prevention; if a patient is lying on their back, they are far more likely to have organisms traveling down and inhibiting the pulmonary toilet from operating clearly. According to Wright, an optimal level of elevation should be around 30 degrees.

Accelerating from the traditional to the cutting edge, there are also a number of technologies that are adept at combating the onset of VAP. "There are things that we as healthcare providers can leverage within the healthcare system that help us actively monitor and identify issues before they become incredibly problematic," says Wright. "For example, patients have been getting their mouths cleaned in the hospital for quite some time, but we've now applied a different technique using something called chlorhexidine, which is a great bacteria killing agent that we've used in the hospital for a lot of other things, such as prepping the skin before surgery.

"They've figured out how to put chlorhexidine into some of the oral care agents that we use to clean the mouth of our patients who are on ventilators, and that drastically reduces the amount of bacteria, which in theory should also dramatically reduce the likelihood that the patient's own oral organisms or flora are going to cause problems in the ventilator. We're starting to use that at NorthShore ourselves."

Silver lining

In addition to such innovative practices, a number of other methods are becoming more widely used in the fight to reduce the incidence of VAP. One such method involves taking a plastic endotracheal tube and lining it with a free silver alloy that is already used in other anti-infective devices. This significantly reduces the likelihood of organisms being able to migrate down the tube and into the patient's lungs.

"The use of silver-coated endotracheal tubes may be used in some of the high-risk patients," says Gajic. "These high-risk patients, who are deemed to require prolonged mechanical ventilation, may potentially benefit from several other strategies too, such as continuous subglottal suction; a procedure that entails specific suction devices either with an ET tube or via a small puncture through the neck, which continuously sucks out secretions before they get to the lungs."

Another important aspect to keep in mind is the patient's position on the bed. "At NorthShore we monitor what angle the head of the bed is at for the patient, whether or not they've received their oral hygiene for that shift, whether they've had a GI prophylaxis and whether their sedation medication has been weaned sufficiently," says Wright. "The reason you would want to do that is because when a patient is on a ventilator they're often heavily sedated. That is often unavoidable, but in order to properly evaluate whether they need to continue to be on a ventilator, you need to wean that sedation medication back a little and find out the truth, so to speak.

"We then document that in our electronic medical record and they're then able to extract that data at a later point and calculate the rate at which we are achieving our process measure. These are the kinds of things that, if my mother were on a ventilator, I would want done or checked on daily. What we're able to do is to turn around and pull that data out on a regular basis, feed that back to the manager and physician for the unit and say 'You and your staff are doing a great job; you're 90 percent at this and 90 percent at that. But maybe we need to work on this area.'

"Likewise, when we identify a person that has an infection, we often pull the information for that particular patient from the medical record in an automated fashion where it's easy to find out what could be contributing to that patient's VAP. From that you can find out whether it was a lack of oral hygiene or the bed head being less than a 30 degree angle, for example, and use that information to interact with the care providers in order to work on the problem area."

Treatment

Flipping the metaphorical coin, once a patient has contracted VAP, a completely new set of perspectives needs to be adopted in order to prevent further complications. From the bedside aid of physicians and nurses, the responsibility at this stage is passed on to the microbiology laboratories at NorthShore and Mayo Clinic, with the intention of turning around a susceptibility profile; essentially finding out which antibiotics work well for a particular bug. As time is critical, a susceptibility profile can often be produced at the same time that the necessary organism is detailed to the necessary staff.

"Timely and appropriate antibiotics are the main therapy for patients with VAP," says Gajic. "The pneumonia that caused respiratory failure (and the need for ventilator care) and the new infection re likely to be resistant to some of the first line antibiotics, so the appropriate choice of antibiotics to cover possible microbes is very important, and it's largely hospital-dependent."

This point is echoed by Wright, who stresses that NorthShore's microbiology laboratories are alert to the dangers posed by incorrect antibiotic administration. "Sometimes, you might actually start antibiotics before you get the results back," he admits. "You start the patient on antibiotics for what you think might be causing the pneumonia. Then when you get the results back, you tailor your therapy to be more specific to that organism and complete the therapy. At the same time, you don't want to give up on trying to get that patient off the ventilator. While VAP is a relatively infrequent occurrence, it's not unheard of for a patient to have pneumonia, recover and still be on the vent and get another pneumonia, so you need to go after it as aggressively as possible."

One would naturally assume that starting a course of antibiotics before the known organism is released could have a detrimental effect on the patient, but as Wright points out, that is very rarely the case. "It will undoubtedly vary from organism to organism and antibiotic to antibiotic, but generally that isn't the case because what we're talking about with empiric antibiotic therapy is usually a single dose or a single day of doses. The bad things that could happen to a VAP patient are the same that can happen to any patient on any antibiotic.

"They might have an allergic reaction or it might adversely affect their kidney function - all those things that you could have with many antibiotics. But the consequences of not starting that treatment early enough are even worse. Hypothetically speaking, if I woke up and had pneumonia while my doctor is waiting 24 to 48 hours to get a result back, I would be well on my way out the door literally before the end of the day.

"Anyone entering a hospital at any time has the possibility of acquiring any sort of HAI. There are drug-resistant bacteria such as MRSA and VRE. There are bacteria that are incredibly smart too. For example, if you come in with a bacterial infection in your lungs and you get placed on antibiotics, you may very well develop what's called C. diff, which is an enteric pathogen in as much as it gives you horrible diarrhea- but it only exposes itself once the patient is put on antibiotics as the antibiotics kills everything else."

Other HAIs relative to VAP include urinary tract infections, which can be yet another source of trouble. If a patient enters the hospital environment to be placed on a ventilator, there is a very good chance that they will have a Foley catheter put in place to aid the patient's functioning and bowel movements.

In addition, and for the same reason, an intravenous line would almost always be present to feed the patient the necessary antibiotics, because swallowing pills is obviously not an option. "Hospitalized patients placed on ventilators are at risk of blood stream and urinary tract infections because they almost always have arterial, central venous and urinary cuts," says Gajic. "These insertions are sometimes unavoidable, and they do increase a patient's risk of contracting a blood stream infection. Again, these infections are partly preventable as long as adherences to strict infection control measures are put into place. We have come a long way in decreasing the risks by proactively thinking, 'When can I take the device out?' rather than having it stay unnecessarily for longer periods and become the cause of infection."

Difficult elimination

With a seemingly infinite number of potential infection routes for a ventilated patient to contract VAP, hospitals have a colossal job on their hands in attempting to prevent both HAIs and VAP. It is here that Wright is clear about the task ahead for the healthcare industry - and it seems that perhaps the term 'prevention' may be more accurate than 'elimination'.

"I realize there are many publications out there that talk about how one hospital got to zero or another hospital got to zero ventilator-associated pneumonias," says Wright. "I think that a lot of that has to do with the subjectivity of determining who has a VAP. That being said, we don't have a very good measure in infection control to assess an individual patient's risk. If you can imagine the gentleman that comes in, has to have cardiac surgery and so goes into the operating room. They intubate him, but he's relatively healthy. The next morning they take his ventilator out. Now, there's no reason why he should ever get a VAP as he's relatively healthy and intubated for a very short period of time.

"Compare that to someone who has been a quadriplegic for 20-25 years and has been chronically trached; it's going to be very difficult to prevent a pneumonia from ever happening in that individual. Say they have multiple health conditions aside from their paralysis - being on a ventilator for that period of time and never experiencing an acute lung infection? I think it's difficult, if not approaching outside the realm of possibility.

"I firmly believe that it's completely possible, plausible and fully achievable to eliminate VAP in our low-risk population and probably even in our moderate-risk patient population - someone who's on a ventilator for a couple of days or even a week. But for those who are chronically receiving artificial ventilation? Never say never, but I think unfortunately it's highly unlikely that it will ever be fully eliminated. The pathogenesis of VAP is very multi-factorial. Even if you have all the bells, whistles, silver tubes, perfect air and the perfect oral hygiene, all you need is that one loving daughter to come in and not wash her hands who wants to give daddy a kiss. There are just far too many options for this to be completely preventable."

On this issue, Gajic is equally skeptical. "Strict prevention protocols and infection control measures can mitigate, but probably not completely eliminate, the causes and complications [associated with VAP] because sometimes the original condition requires the presence of these foreign devices for a lengthy period of time, and it is simply impossible to avoid all of these infections. Foreign bodies in an organism do, obviously, break the natural defenses, they break barriers, and they cause infections."

While Wright jokingly suggests that the best way to avoid an HAI is to not become hospitalized, his quip does carry a serious message for the progression of fighting VAP: complete elimination is just not plausible. Instead, VAP should be fought by preventative methods that are backed up by a solid and efficient system, which functions instinctively when the unfortunate event of a VAP does occur. "Consistent efforts on VAP prevention will lead to reductions in the incidents of this complication and the associated burden," concludes Gajic. "So it can be greatly limited but will never, unfortunately, be completely eliminated."

Biographies

Marc-Oliver Wright is Director of Infection Control at NorthShore University HealthSystem.

Ognjen Gajic is the Associate Professor of Medicine at the College of Medicine, Mayo Clinic.

VAP statistics

VAP may account for up to 60% of all deaths from healthcare-associated infections (HAIs) in the US

Healthcare-associated pneumonia patients have a mortality rate of 20% to 33%

VAP increases patient time in the ICU by 4 to 6 days

Each incidence of VAP is estimated to generate an increased cost of $20,000 to $40,0001

Source: CDC