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Infection control in burns patients

Joan M Weber
1 July, 2006  

Joan M Weber
RN BSN CIC
Infection Control Coordinator
Shriners Burns Hospital
Boston, USA
E: jweber@partners.org

Infection in burn patients is a leading cause of morbidity  and mortality and remains one of the most challenging  concerns for the burns team. The importance of preventing  infection has been recognised in organised burns care since  its inception. Strategies for infection prevention and  control, including guidelines for culturing and  surveillance, isolation of patients, environmental concerns  and use of antibiotics will be discussed.

Epidemiology of infection
The development of infection depends on a source of  organisms, a mode of transmission and the susceptibility of  the patient. Infection risk for burn patients is different  from other patients in several important respects. Sources  of organisms are found in the patient’s own endogenous  (normal) flora,  exogenous sources in the environment and in  healthcare personnel. Exogenous organisms from the hospital  environment are generally more resistant to antimicrobial  agents than endogenous organisms. Organisms associated with  infection in burn patients include Gram-positive,  Gram-negative and yeast/fungal organisms.

Gram-positive organisms of particular concern include  methicillin-resistant S aureus (MRSA), vancomycin-resistant  enterococci (VRE) and the potential development of  vancomycin-resistant S aureus. MRSA has become an endemic  organism in many burns units. It has been argued that no  extraordinary efforts be made to control its spread;  however, this view has been increasingly challenged in the  era of VRE. With the increasing incidence of VRE in  hospitals, the risks associated with infection with this  organism are also increasing. Risk factors identified in  patients colonised with VRE include one or more of the  following: prior vancomycin use, prior use of  third-generation cephalosporins and antibiotics active  against anaerobes, a critically ill patient with severe  underlying disease or immunosuppression, and a prolonged  hospital stay. These factors are all present in patients  with a large burn injury, including previous vancomycin use  in units with a high endemic rate of MRSA.

Gram-negative organisms have long been known to cause  serious infection in burn patients. Gram-negative  bacteraemia has been associated with a 50% increase in  predicted mortality for patients with bacteraemia compared  to those without bacteraemia.(1) At present, Gram-negative  organisms such as P aeruginosa and A baumannii that are  resistant to multiple antibiotics are of particular concern  in both burns units and elsewhere in the hospital. Fungal  organisms, especially Candida (yeast) species and true fungi  (mould) like Aspergillus, Mucor and Rhizopus have been associated with serious infection in burn patients. Candida colonisation appears to be primarily from endogenous sources  while true fungi are ubiquitous in the environment. They can  be found in air handling and ventilation systems, plants and  soil.

Modes of transmission include contact, droplet and airborne  spread. In burn patients the primary mode is direct or  indirect contact, either from the hands of the personnel  caring for the patient or contact with inappropriately  decontaminated equipment. Burn patients are unique in their  susceptibility to colonisation from organisms in the  environment as well as in their tendency to disperse  organisms into the surrounding environment. In general, the  larger the burn injury, the greater the volume of organisms  that will be dispersed into the environment from the  patient.

The patient has three principal defences against infection:  physical defences, nonspecific immune responses and specific  immune responses. Changes in these defences determine the  patient’s susceptibility to infection.

Invasive devices, such as endotracheal tubes, intravascular  catheters and urinary catheters bypass the body’s normal  defence mechanisms. Infection from intravascular catheters  is of particular concern for burn patients because these  lines must be placed directly through or near burn-injured  tissue. Catheter-associated bloodstream infection (BSI) is caused by  organisms that migrate along the catheter from the insertion  site and colonise the catheter tip.(2) Catheter tips are  also susceptible to colonisation from haematogenous seeding  of organisms from the affected burn wound.

Incidence of infection
Incidence of infection is also affected by the size of the  patient’s burn injury. The overall incidence of infection is  low for patients with smaller (<30% total body surface area  [TBSA]) burn injuries and generally associated with the need  for invasive devices. Invasive burn wound infection is  rarely seen. When it occurs it is usually in patients with  larger (≥30% TBSA) burn injury. BSI increases dramatically  as burn wound size increases, related to increased exposure  to intravascular catheters and to burn wound  manipulation-induced bacteraemia. Pneumonia occurs most  frequently in ventilated patients and urinary tract  infection (UTI) occurs principally in patients with  indwelling urinary catheters.

Outbreaks on burn units
Outbreaks of cross-colonisation and infection are a major  challenge in burn units. They require a clear understanding  of how and why they occur in order to prevent or control  them. The exact cause for many of these outbreaks cannot be  determined. However, certain patterns are clear.

In almost all cases the colonised patient is thought to be a  major reservoir for the epidemic strain. Other important  sources include contaminated hydrotherapy equipment, common  treatment areas and contaminated equipment (eg, mattresses),  which appear to pose unique risks of cross contamination in  the burn environment. Risks associated with caring for the  burn wound, such as hydrotherapy and common treatment rooms,  are related to the use of water sources that are frequently  contaminated by Gram-negative organisms intrinsically, and  may also be contaminated by organisms from other  patients.(3) This aquatic environment is difficult to  decontaminate because of continuous reinoculation of  organisms from the patients’ wound flora and the organisms’  ability to form a protective glycocalyx in water pipes,  drains, and other areas – making them resistant to the  actions of disinfectants.

The risks associated with a “common treatment room” involve  the contamination of the surrounding environment and the  difficulty in ensuring that the room is appropriately  cleaned between successive patients. This is difficult given  the number of procedures performed each day and the  necessity of stocking the room with dressing supplies for  multiple patients. For patients at increased risk of  infection – those with 30% burn or greater, or those with  invasive devices – hydrotherapy and common treatment rooms  should be used cautiously, if at all. If dressings can be  changed at the patient bedside, this is preferable to  exposing these patients to the risks of common treatment  rooms or hydrotherapy.

The other principal modes of transmission in burn units are  by the hands of the personnel and through contact with  inadequately decontaminated equipment or surfaces. The hands  and apron area of the carer are most likely to become  contaminated, as the surfaces (ie, beds, side rails, tables  and equipment) are often heavily contaminated with organisms  from the patient. Likewise all equipment used on the patient  (ie, blood pressure cuffs, thermometers, wheelchairs and IV  pumps) are also heavily contaminated and may be transmitted  to other patients if strict barriers are not maintained and  appropriate decontamination carried out. In fact, a single  cause is uncommon in a burn unit outbreak; in almost all  instances, multiple factors contribute to its occurrence and  perpetuation.

Culturing and surveillance
Culturing and surveillance guidelines are more stringent for  the burn patient, particularly the patient with larger  injuries, because of the increased propensity for  transmission and infection in this population. The purposes  of obtaining routine surveillance cultures are:

  • To monitor the effectiveness of current wound treatment.
  • To guide perioperative or empiric antibiotic therapy.
  • To detect any cross-colonisations that occur quickly in  order to prevent further transmission.

Wound cultures should be obtained for routine surveillance  when the patient is admitted and at least weekly until the  wound is closed. Many burn centres recommend obtaining wound  cultures two or three times a week for patients with large  burn injuries. Admission cultures are particularly important  for patients transferred from other facilities, as they may  be colonised with multiply resistant organisms and serve as  an unsuspected reservoir for cross-transmission to other  patients in the unit.

Surveillance of infection has been shown to diminish the  rate of nosocomial infection as well as reduce costs related  to length of hospitalisation, isolation and the need for  antibiotic therapy. (4,5,6,7) Surveillance of infection in  burn patients should be done to monitor incidence and rates,  which have been appropriately risk-adjusted by the size of  burn injury and invasive device use. At a minimum,  surveillance should include collection of data on burn wound  infection, urinary tract infection, pneumonia and BSI.  Systematic collection of data allows the burn unit to  monitor changes in infection rates over time, identify  trends and evaluate current treatment methods.

Isolation guidelines
Standard precautions should be followed when caring for all  patients with burn injury.  The effectiveness of simple  protective barrier precautions in reducing nosocomial  colonisation and infection was shown in a study by Klein et  al in a paediatric intensive care unit (ICU).(8) Most burn  units also supported the concept of barrier techniques and  isolation. The open burn wound increases the environmental  contamination present around the patient, which is the major  difference between burn and nonburn patients.

Patients with greater than 30% TBSA burn injuries are more  immunocompromised, due to the larger size of their injury.  In combination with their loss of physical defences and need  for invasive devices, this significantly increases their  risk of infection. There is also a major risk of these  patients contaminating their environment with organisms,  which may then be spread to other patients on the unit.  These may include multiply resistant organisms, if  broad-spectrum antibiotic treatment has been required to  treat infectious complications. For these reasons, it is  recommended that patients with larger burn injuries are  isolated in private rooms or other enclosed bed spaces to  ensure physical separation from other patients. Such  isolation has been associated with a decrease in  cross-transmission of organisms.(9,10)

Special attention is also required for patients with smaller  burn injuries who are colonised or infected with multiply  resistant organisms such as MRSA, VRE or multiply resistant  Gram-negative organisms. This is especially true for  patients with wound drainage that cannot be adequately  contained in dry, occlusively wrapped outer dressings or  paediatric patients who cannot comply with hand washing or  other precautions. Patients transferred to the burns unit  after treatment in another hospital should also be included  in this group until the results of their admission cultures  are known. These patients are frequently colonised with  resistant organisms and may serve as an unsuspected  reservoir for transmission to other patients unless they are  isolated. Isolation for this group of patients generally  includes placement in a private room on contact precautions,  with the addition of droplet precautions in some  circumstances.

Patients colonised with multiply resistant organisms must  frequently have their need for isolation balanced against  their need for rehabilitation. In general, if the patient’s  wound cannot be occlusively wrapped in a dry outer dressing,  the patient should not be taken to the rehabilitation  department for therapy when other patients will be present  in the same area. If rehabilitation needs cannot be met in  the patient’s room, then sufficient time should be scheduled  in the rehabilitation department to allow for the patient’s  treatment followed by thorough cleaning of all equipment and  surfaces before the area is used by other patients. The  rehabilitation therapy staff should wear appropriate attire  during therapy.

Environmental issues
Disinfection and sterilisation guidelines for patient care  equipment must take into account the presence of extensive,  open wounds – the major distinction separating this group  from other patient populations. Following Spaulding’s scheme  for categorising patient care items and equipment, the  changes for the burn patient population involve  “semicritical” and “noncritical” items.(11) Many items, such  as blood pressure cuffs, stethoscopes and bedpans – if used  on areas without dry, occlusive dressings – may need  high-level disinfection as a semicritical item or may need  to be restricted to an individual patient.

Plants and flowers should not be allowed in units with burn  patients because they harbour Gram-negative organisms, such  as Pseudomonas species, other enteric Gram-negative  organisms and fungi. Many of these organisms are  intrinsically resistant to multiple antibiotics, which may  serve as reservoirs to colonise the burn wound.(12)

Paediatric burn patients should also have policies  restricting the presence of non-washable toys such as  stuffed animals and cloth objects. These can harbour large  numbers of bacteria and are difficult to disinfect. Toys  should be nonporous and washable, designated for individual  patient use. They should be thoroughly disinfected after use  and before being given to another child. Paper items, such  as storybooks and colouring books, should always be  designated for a single patient’s use. They should be  disposed of if they become grossly contaminated or when the  child is discharged.

Antimicrobials and burns
Systemic antimicrobial treatment must be thoughtfully  considered in the care of burn patients to prevent the  emergence of resistant organisms. The burn wound will always  be colonised with organisms until wound closure is achieved.  Administering systemic antimicrobials will not eliminate  this colonisation, but promote the emergence of resistant  organisms. If antimicrobial therapy is indicated to treat a  specific infection, it should be tailored to the specific  susceptibility patterns of the organisms as soon as this  information is available.

Conclusion
Many questions have yet to be answered for the burn patient  in relation to appropriate management of infection control  issues. The use of invasive devices, in particular central  venous catheters, should be re-evaluated in light of the new  catheter technologies and improved wound management  techniques.

An important area for future study relates to the clinical  problem of appropriate precaution strategies, particularly  for patients colonised with multiply resistant organisms.  The goal should be identifying cost-effective measures that  prevent outbreaks involving other patients on the unit.  Currently, there is wide variation in precautions for burn  patients, with no agreed upon standards followed in most  burn centres. In an era of changing healthcare priorities,  studies are also needed to evaluate the efficacy of caring  for burn patients outside the burns centre or of caring for  non-burn patients in the burns centre. The impact that burn  patients will have on existing infection rates and  infectious complications must be integral to decisions and  the effect these decisions will have on costs, patient  outcomes and patient satisfaction.

Resources
International Society for Burn Injuries
W: www.worldburn.org
American Burn Association
W: www.ameriburn.org
European Burns Association
W: www.euroburn.nl

References

  1. Mason AD Jr. McManus AT, Pruitt BA Jr. Association of  burn mortality and bacteremia: a 25-year review. Arch Surg  1986;121: 1027-31.
  2. Goldman DA and Pier GB. Pathogenesis of infection related  to intravascular catheterization. Clin Microbiol Rev  1993,6:176-92.
  3. Weber JM.Epidemiology of infections and strategies for  control. In: Carrougher GJ, editor. Burn care and therapy.  St Louis: Mosby; 1998 p. 185-211.
  4. Haley RW, Culver DH, White JW, et al. The efficacy of  infection surveillance and control programs in preventing  nosocomial infections in US hospitals. Am J Epidemiol  1985;121:182 -205.
  5. Nichols RL. Surgical wound infection. Am J Med 1991;91  Suppl 3B:54S-64S.
  6. Condon RE, Schulet WJ, Malangoni MA, et al. Effectiveness  of a surgical wound surveillance program. Arch Surg  1983;118:303-7.
  7. Olsen MM, Lee JT. Continuous 10-year wound infection surveillance: results, advantages, and unanswered questions.  Arch Surg 1990;125:794-803.
  8. Klein BS, Perloff WH, Maki DG. Reduction of nosocomial  infection during pediatric intensive care by protective  isolation. N Engl J Med 1989;320:1714-21.
  9. Burke JF, Quinby WC, Bondoc CC et al. The contribution of  a bacterially isolated environment to the prevention of  infection in seriously burned patients. Ann Surg 1977;186: 377-87.
  10. McManus AT, McManus WF, Mason AD Jr, et al.Microbial  colonization in a new intensive care burn unit. Arch Surg  1985;120:217-23.
  11. Rutala WA.Disinfection and sterilization of patient care  items. Infect Control Hosp Epidemiol 1996;17:377-84.
  12. Kates SG, McGinley KJ, Larson EL, et al. Indigenous  multiresistant bacteria from flowers in hospital and  nonhospital environments. Am J Infect Control  1991;19:156-61.