Introduction
A nosocomial infection is any infection acquired while the patient is hospitalized. Between the years of 2003 and 2008, 82% of veterinary teaching hospitals reported outbreaks of nosocomial infections with 45% reporting more than one outbreak. Human studies suggest that at least 1/3 of all nosocomial infections are preventable.
Etiology of Nosocomial Infections
There are numerous risk factors identified in hospitalized patients that contribute to the incidence of nosocomial infections including length of hospitalization, indwelling catheters, mechanical ventilation, use of total parenteral nutrition, antibiotic usage, use of histamine (H2) blockers, age, and immune deficiency. Of these risks factors, length of hospitalization tends to be the most significant risk factor. In critically ill patients, nosocomial infections are most frequently acquired via the urinary tract, respiratory tract, surgical incision sites, and via intravenous devices, which combined account for approximately 80% of all human reported nosocomial infections. In dogs catheter-associated UTIs account for up to 38% of nosocomial infections. Even with closed collection systems bacteriuria (a precursor to infection) can develop in 32–52% of cases.
Prevention of Nosocomial Infections
Veterinary staff are probably the biggest vectors for nosocomial infections, disseminating new infections among our small animal patients. With a few simple strategies, transmission rates of nosocomial infections can be greatly reduced. The most important intervention continues to be frequent hand washing. The role of other vectors such as stethoscopes, and lab coats remains unclear. The use of gloves, gowns and masks play a role in disease control, although they are often used inappropriately in prevention of nosocomial infections. Finally, numerous studies have shown that disinfecting hospital surfaces (benches, floors, etc.) makes no difference in the prevalence of nosocomial infections.
Hand Washing
Multiple studies have found that hand washing is the single most important measure in controlling nosocomial infections and that the hands of hospital personnel are the most common vectors of microorganism transmission between patients. Interestingly, studies show that hospital staff believe they wash their hands more often than they actually do, and tend to overestimate the duration of hand washing. In one study, hospital staff only washed their hands 30% of the time after patient contact and 50% of the time following activities defined as likely to result in heavy contamination. Poor hand washing compliance has been linked to increased hospital workload and reduced availability of hand decontamination agents.
Indications for Hand Hygiene
Before and after touching patients - hands can become infected simply by taking a pulse, blood pressure or touching intact areas of a hospitalized patient's skin.
If moving from a contaminated body site to another site during care of the same patient.
After contact with inanimate surfaces and objects (including medical equipment) in the immediate vicinity of the patient.
After removing sterile and nonsterile gloves.
Alcoholic Disinfectants vs. Medicated Soap
There is no clear evidence to state one disinfectant agent is superior to another. However, it has been estimated that for human nurses to have 100% compliance with hand washing using medicated soaps they would need to spend 16 hours of a 24 hours shift washing their hands, as opposed to only 3 hours using an alcoholic bedside dispenser (takes 20 seconds for alcoholic sprays vs. up to 80 seconds using soap). Alcohol based solutions remove more microorganisms, require less time, irritate the skin less than hand washing with soaps or other antiseptics and water. Alcohol based hand rubs are the standard of care for hand hygiene as recommended by the Healthcare Infection Control Practices Advisory Committee Guidelines.
Irrespective of which decontamination agent is used the recommendation is that it be readily available, within 3 feet of the most likely areas of use or should be carried in small bottles by hospital workers for their own personal use.
Wedding Rings and Other Hand Jewelry
Higher microbial counts after hand washing are found in hospital staff who do not remove rings, which may put patients at higher risk for nosocomial infection, particularly in operating theatres. The use of a scrub brush for surgery is questionable based on some studies which have shown a greater reduction in microorganisms with hand washing alone compared to use of a scrub brush. A recent veterinary study reported that 50% of veterinary assistant/techs wear 1–2 rings and less than 50% of respondents regularly wash their hands between patients. Being too busy is the biggest reason stated for not washing hands. About 50% of respondents report not being educated on the merits of hand washing.
Vigilance in Hand Washing
Education of staff and designating someone to "police" hand washing can greatly improve hand washing compliance. One study reports that providing feedback to staff regarding frequency of hand washing can increase compliance by 92%. However, when feedback is discontinued, compliance returns to baseline levels. This emphasizes the importance of making sure hand wash agents are readily available, that personnel are educated, and that senior staff need to set a good example by leading and encouraging others to hand wash.
Gloves
Gloves generally tend to supplement and should not replace hand washing. There are studies that document microbial contamination of hands and transmission of infections between patients despite gloves being worn. Gloves, if used, need to be changed between each patient.
Gowning
In intensive care units the use of routine gowning to help keep infectious material off clothing, in combination with gloving and hand washing was not shown to be beneficial over use of gloves and hand washing alone with regards to microorganism transmission between patients and the incidence of nosocomial infection. Note that this refers to nosocomial infections and not infectious disease transmission such as parvovirus where use of gowns play a more important role.
Masks
When originally introduced, the primary role of the facemask was to prevent microorganisms of the mouth and nose of operating team members from contaminating surgical wounds of the patient. Recent studies question the use of masks in preventing wound infections in the operating room. One study showed that after 1537 operations performed with masks on, the incidence of wound infection was 4.7%, which operations on 1551 patients without wearing masks was only 3.5%. Therefore, it appears that while masks may protect operating teams from infectious fluids of the patient and from air bourn infections, they do not protect the patient from wound infections.
Stethoscopes
There are no studies demonstrating that cleaning of stethoscopes reduces nosocomial infection rates. However, several studies have demonstrated that 90% of hospital staff stethoscopes contain potential nosocomial microorganisms and that cleaning of the stethoscopes diaphragm with alcohol swabs decreases bacterial counts by 94%. Unfortunately, when surveyed, only 48% health care providers cleaned the diaphragm of their stethoscope daily or weekly, 37% monthly, 7% yearly, and 7% had never cleaned their stethoscopes.
White Coats
White coats have been shown to be a source of cross contamination, particularly between surgical areas. The cuffs and pockets of the coat are the sites most heavily contaminated with microorganisms. Interestingly, when surveyed, half of human patients prefer their doctor to wear a white lab coat.
Preventing Catheter Associated Urinary Tract Infections
The best prevention of a urinary catheter associated infection is avoidance of urinary catheter placement unless it is essential. Situations where a urinary catheter is deemed essential includes monitoring of critically ill patient urine output (i.e., mechanically ventilated patients, oliguric/anuric renal failure etc.), cases with urethral obstruction/trauma, perioperative use in selected non ambulatory post-surgical patients, patients with open wounds, and urinary incontinence where the risk of wound contamination with urine is high. If urinary catheterization is essential, it is important to limit the duration and frequency of catheterization and ensure strict adherence to aseptic technique when placing the urinary catheter. Breaks in aseptic technique during catheter placement and disruption of the closed system are the biggest contributors to catheter associated urinary tract infections. Do not lift the collections bag/system above the patient (keep the urine collection bag below the level of the bladder to prevent reflux of urine into the bladder) and do not retro-flush the urine lines as urine in the bag and line should be considered contaminated. Empty the collection bag frequently to prevent buildup of urine and retrograde flow from excessive pressure in the collection bag or lines.
Preventing Surgical Site Infections
The duration of surgery is the biggest contributor to development of surgical site infections in veterinary patients, and the rate of infection nearly doubles for every hour of surgery in people. It is therefore recommended that surgery times be kept as short as possible without compromising sterility or surgical technique.
In people it is not recommended to shave the patient as shaving is associated with increase damage to the epithelium, which allows bacteria colonization and increased surgical site infections. Although shaving is essential in vet patients studies have shown that shaving before induction of anaesthesia is associated with higher surgical site infection rates than shaving after induction of anaesthesia. It is therefore recommended to shave veterinary patients as close to the time of surgery as possible. Clipper blades should ideally be sterilized (at least cleaned) between uses.
Preventing Catheter Related Blood Stream Infections
Catheter related blood stream infections are caused by intravascular devices, particularly central lines and are responsible for over 25% of all nosocomial blood stream infections in critically ill human patients, with a reported mortality of 25%. In a canine veterinary study bacterial colonization of IV catheters ranged from 15–48% (with colonization being a precursor to catheter related infection). Most infections resulted from skin pathogens. Although there is evidence to suggest catheter duration increases the risk of catheter related blood stream infections, human studies fail to show a difference in infection rates when catheters are changed every 3 days vs. every 7 days. Similarly, a veterinary study showed that peripheral catheters can be left in place up to 10 days provided aseptic technique is observed during placement of the catheter and very diligent catheter care. The current human recommendation is that catheters be removed as early as medically indicated but that routine catheter changes be avoided unless there is evidence of infection. Although changing the catheter may not decrease the incidence of infection, a human study showed that changing the administration sets every 72 hours resulted in a significant reduction in the incidence of Klebsiella infections in a busy neonatal unit. It is also recommended that gauze bandages be changed every 2 days and transparent dressing be changed every 5 days to allow the catheter insertion site to be diligently inspected. There is no evidence to support the role of prophylactic antibiotics in preventing central line catheter related infections.
Unfortunately it is rare for catheter related blood stream infections to be associated with inflammatory signs at the insertions site. That said the finding of inflammation at the insertion site is a reliable indicator of a catheter related infection (high specificity). The presence of an unexplained fever might be a more sensitive indicator of a catheter related blood stream infection.
Prevention of IV infection requires diligent insertion technique and meticulous catheter care. Placement of an IV catheter should be considered a surgical procedure where the skin barrier is broken with passage of the catheter. The hands must be washed prior to catheter placement and ideally gloves should be worn. The insertion site should be disinfected with alcoholic chlorhexidine or 70% isopropyl alcohol for at least 30 seconds and allowed to dry before inserting the catheter. Do not touch the insertion site after disinfection (do not palpate the vein after disinfecting). Comparing different disinfectants (2% chlorhexidine, 10% povidone-iodine and 70% alcohol), the rate of catheter associated bacteremia was 4 times lower in patients that received chlorhexidine compared to the other groups.
Use of adhesive impermeable dressing has been shown to trap sweat and blood below the dressing, increasing risk of contamination compared to gauze alone. Newer permeable dressings should minimize the risk of moisture accumulation below the dressing and subsequently decrease the risk of sepsis.
References
1. Saloojee H, Steenhoff A. The health professional's role in preventing nosocomial infections. Postgrad Med J. 2001;77:16–19.
2. Nakamura RK, Tompkins E. Nosocomial infections. Compend Contin Educ Vet. 2012;E1–E11.
3. Nakmura RK, Tompkins E, Braasch JG, et al. Hand hygiene practices of veterinary support staff in small animal private practice. J Small Anim Pract. 2012;53:155–160.