Nosocomial infections (Proceedings)

Nosocomial infections are defined as infections that are neither present nor incubating at the time of hospital admission. Nosocomial infections range from mild to severe, depending on the affected system and resistance of the bacteria. On average, human nosocomial infections result in a 2.5 times longer length of stay in hospital. In veterinary medicine, prolonged hospital stays can grossly affect patient outcome due to cost limitations, which can result in euthanasia if owners cannot afford to pay for the extended hospitalization and antimicrobial treatment. Universal key points for infections control include hand washing and disinfectant protocols.

Nosocomial infections can also arise from endogenous or exogenous sources. Endogenous sources imply self-infection with a patient's own overgrowth of bacterial flora, typically as a result of the use of broad spectrum antimicrobials affecting an otherwise normal balance in the patient's normal flora. Use of the broad-spectrum antibiotics may allow more resistant bacteria to survive and proliferate, while more susceptible organisms diminish. Exogenous sources are typically from outside sources, such as the use of contaminated equipment or devices, non-sterile technique in invasive procedures, or introduced from the hands of the veterinary staff onto the patient through an open wound, incision, or handling of tubes or catheters inserted into the patient. Bacteria that are most often associated with nosocomial infections include: Enterococcus spp., E. coli, Staphylococcus spp., Enterobacter spp., Klebsiella spp., Acinetobacter spp., and Pseudomonas spp. Nosocomial infections can present in many sites. The most common nosocomial infections reported in medical literature includes urinary tract infections, bloodstream infections, surgical site infections, infections of the respiratory and gastrointestinal tract.

In the critical care setting, a high rate of infection can be common due to organisms present, multiple invasive procedures and devices used, numerous care members and the type of underlying disease process present in the patient. The risk of infection increases with the patient's age, and the use of immunosuppressant drugs (such as steroids or chemotherapy agents). Other factors that influence a host's ability or defense against infection include: leukopenia, decreased granulocyte function, burns, presence of a concurrent infection, severe underlying illness, and age (very young or geriatric patients).

The hospital environment contributes negligibly to the acquisition and spread of most nosocomial infections. Therapeutics are directed towards monitoring and preventing nosocomial infections through mandatory hospital and patient care protocols. Environmental culturing in order to identify causative organisms should also be performed several times a year in heavy treatment and patient recovery areas.

CONTROL MEASURES

Hand washing is a superior method in preventing nosocomial infection. In human hospitals, hand carriage and transmission of epidemic organisms by hospital personnel onto hospitalized patients has commonly been detected. Hand washing procedures should be performed between handling of patients, after cleaning bedding or cages, prior to the handling of equipment or non-sterile procedures, and before handling of any immunocompromised pet. Hand washing should include a short wash (10 to 15 sec.) with plain soap, or longer wash (30 sec.) with a topical antibacterial agent. In the surgical setting, topical antimicrobial agents that remove both transient and resident microorganisms should be used for hand washing, as well as for surgical scrubbing.

In the ICU setting, plain soap is not recommended, as the action of plain soap does not include the removal of viable transient microorganisms. If bar soaps are used, the bar should be kept on racks to allow drainage of water; if liquid soap is used, the dispenser should be replaced or cleaned and filled with fresh products only when empty. Topical antimicrobial and antiseptic products are more efficacious hand washing agents, as it both mechanically removes and inhibits both transient and resident flora. In addition, most antimicrobial/antiseptic products allow safe application to skin, wounds, and mucous membranes. They also have the ability to bind to the stratum corneum, resulting in persistent chemical activity. Topical antiseptics or antimicrobial hand products should be used before performing any of the following:

     √ Invasive surgical procedures or the placement and/or care of intravascular catheters, indwelling catheters, or other invasive devices such as feeding tubes, lavage catheters, chest tubes, or urinary catheters

     √ Contact with immunocompromised patients such as those with burns, pressure sores/ulcers, wounds, and those undergoing chemotherapy or mechanical ventilation

     √ Care of geriatric or pediatric patients

Alcohol or alcohol based products have excellent bactericidal activity against most gram-positive and gram-negative microorganisms. Although not typically sporicidal, they do act against many fungi and viruses such as respiratory viruses, hepatitis B virus and HIV. Mechanisms of action include denaturization of microbial proteins, but can be inactivated by organic materials such as blood, mucus, and sputum. A vigorous 1-minute hand rubbing with enough alcohol to get hands wet has shown to be the most effective method for hand antisepsis by providing the greatest and most rapid reduction in microbial counts on the skin. In addition, alcohol combined with other antimicrobials or plain soap has been found to be very effective against microorganisms. The most effective product regimen for both an overall microorganism reduction profile and a skin irritation potential is the combination of alcohol gel with either an antimicrobial soap or plain lotion soap. The disadvantage to application of pure alcohol is its drying effect on the skin and the absence of residual antimicrobial activity.

Antimicrobial agent chlorhexidine gluconate is also efficacious against the spread of nosocomial infections. Chlorhexidine attains levels of antimicrobial action by causing a disruption of the microbial cell plasma membranes and precipitation of cell content. In addition, it has a persistent effect that is independent of its cumulative action, allowing it to be chemically active for 5 to 6 hours. Chlorhexidine is commonly used against gram-negative and gram-positive bacteria. It has minimal action against tubercle bacillus, and is only a fair inhibitor of fungi.

Iodine/iodophors products produce a positive antiseptic effect by penetrating cell walls. They are highly bactericidal, fungicidal, and virucidal agents. Iodophors contain water-soluble organic iodine that breaks down on the skin or mucous membranes to release free iodine. They have rapid initial antimicrobial activity after application, but minimal residual effect. Their effectiveness is reduced by the presence of organic materials such as blood and sputum.

Examples of common veterinary disinfectants

Isolation Policy

Patients with transmissible infections should be removed from the ICU or main treatment area. Protective devices such as physical barriers (gloves, gowns, or masks) should be utilized to prevent direct exposure of transmissible organisms to other patients. A dedicated staff member should handle isolation patients only, without contact to the other hospitalized patients. Routine use of gowns and gloves should also be implemented for immunocompromised patients, patients on mechanical ventilators, burn victims, septic patients, and the geriatric or pediatric pet. The following personnel protocols should be practiced: washing hands with soap before coming on duty; before and after direct or indirect contact with patients, before and after performing any bodily function, (such as blowing your nose, or using the bathroom), before preparing or serving food (and not eating in areas holding patients), before preparing or administering medications, after direct or indirect contact with a patient's excretions, secretions, or blood; and after completing your shift. Administration of injectable medications should be performed with sterile technique; reconstituted medications should be handled aseptically, and all patient tubes handled conscientiously.

Patient Procedure Protocols

Catheter Care

Cephalic catheter care should be performed every 24 hours. Remove all supportive bandages and inspect insertion site for signs of phlebitis or thrombosis, i.e. redness, swelling, or ropelike vein. Flush catheter with small amount of heparinized saline (1.0-2.0 ml) using a pulsing movement while palpating tip of catheter. If any swelling or pain results from the flush, the catheter should be removed. If the patient is not on intravenous fluids, the catheter should be flushed every 4 hours (cephalic or jugular).

If the catheter is patent, the area should be cleaned with dilute povidine scrub or alcohol wipe. Dry area well. Place a small amt povidone or antibiotic ointment over insertion site and rebandage catheter. Recommended bandaging material is two inch tape (one piece to secure the catheter, and one piece to anchor tport), cast padding in a single layer, followed by kling gauze and vetwrap for the final layer. Record date of placement of IV, as well as the date of the rewrap. The catheter should be changed on the morning of the 4th day.

Routine checks of catheters should be done every 2 hrs for leakage or swelling. Swelling distal (below) to the catheter is usually indicative of a tight bandage. Swelling proximal (above) the catheter could indicate extravasation of the administering fluid or medication. Record all checks on the observation sheet or orders.

Jugular catheter care also requires daily inspection as indicated above. The insertion site should be cleaned with povidine solution and/or alcohol. As the jugular catheter is significantly longer in length than the cephalic catheter, signs of extravasation may not be as apparent. Inspect mid-sternal area for edema on jugular catheters placed in the jugular vein, and the proximal aspect of the medial saphenous area if the catheter was inserted in either lateral or medial saphenous vessel. Bandaging material needed includes a 4X4 of gauze with antibiotic ointment, followed by a single layer of casting padding, followed by kling gauze and vet wrap. No tape is necessary to anchor a jugular catheter, as these are generally sutured in place. Note that neck bandages should have the "two finger rule", wherein the bandage is loose enough to slide two fingers under for patient comfort.

If the jugular catheter is made of polyurethane material (i.e. Arrow International®), the catheter does not need changed out within a 90 day period. Other catheter types made from polypropylene material (MILA®, Intracath®) need changed on the morning of the fifth day. Record date and site of placement, as well as date of bandage change, on observation sheets or orders.

Urinary catheter care should be performed every 24 hours, or as needed to keep the urogenital area clean. Use dilute povidone scrub and water rinse when cleaning the prepuce or vulva and the surrounding area. Flush the sheath or vestibule with 1:5 povidone solution or water. Dry area well. Collection systems should contain anti-retrograde devices or valves (i.e. Kendall Health Care®) to prevent urine from spilling back into the urethra or bladder if the bag is lifted above the patient. See Urinary Catheter Placement protocol to ensure sterility upon placement.

Surgical wound infections

Surgical incision infections are generally well localized and are characterized by the formation of thick, creamy, odorless pus. Infected wounds are usually erythematous, edematous, and painful, and almost always respond to local drainage procedures. Gram-negative wound infections usually result from contamination with enteric contents. Typical incubation period for surgical wound infections is 7 to 14 days. They usually produce fewer local signs or erythema, edema, and pain, but more often have overt signs of systemic sepsis with fever, tachycardia, and quite often, positive peripheral bacterial cultures. Wound infection caused by gram-negative enteric organisms should always be treated with drainage of the wound, debridement, and antibiotic coverage for gram-negative enteric organism and anaerobes.

Equipment

All monitoring equipment should be kept clean and inspected prior to patient use. Particular emphasis on respiratory equipment (such as endotracheal tubes) in order to prevent pneumonia, should be instituted by the veterinary team. Endotracheal tubes should be sterilized if reused. Patients that are on ventilatory support for prolonged periods can be immunocompromised; handling of any equipment should be with sterile technique only. Endotracheal tubes should be changed frequently and suctioned with sterile technique.

References

1. Rivera, Angel, Nosocomial Infections, ACVIM 2004.

2. Flaherty JP, Chou T, Arnow PM: Infection Surveillance and Control in the ICU, in Hall JB, Schmidt GA, Wood LDH (eds): Principals of Critical Care. McGraw-Hill, Inc 1992

3. Johnson JA, Murtaugh RJ: Preventing and Treating Nosocomial Infection (Part I & II) Compendium issues: May 1997 (Vol. 19, No. 5) and June 1997 (Vol. 19, No. 6)

4. Clark, Chris, DVM, University of Saskatchewan, Solving Nosocomial Infection Problems Western Veterinary Conference 2003.