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The Infectious Disease Model
and Breaking the Chain
Of Infection
MSIPC
Fundamentals of Infection, Prevention, Control and
Epidemiology
2015
Ruth Anne Rye, RN, BS
The Infectious Disease Model
Chain of
Infection
The Chain of Infection helps to explain the infection process.
Each link represents a component or element in the cycle, and
must be present in sequential order for infection transmission to
occur. Understanding the characteristics of each link and the
relation to the other links is important to determine
interventions and strategies to break the chain and prevent
infection. Breaking the chain of infection is the responsibility of
every healthcare professional.
Infectious
Agent
Susceptible
Host
Reservoir
Chain of
Infection
Entry
Transmission
Exit
Chain of
Infection
Infectious Agent
• Bacteria
• Exogenous: from
outside the body
• Endogenous: from
inside the body
– Bacilli
– Cocci
– Spirochetes
• Virus
• Fungi
• Rickettsia
• Protozoa
Chain of
Infection

Reservoir
Storage site for growth and reproduction

•
•
•


Humans: Patient’s own flora - transient or chronically colonized
Incubating
Active disease
Convalescent
Animals
Environment
• Food, beverages, soil,
• Healthcare equipment
o Contaminated
o Handling
o Storage
Chain of
Infection
Mode of Exit
 Organism leaves the Reservoir
– Respiratory tract
• Cough, sneeze, talking
– Gastrointestinal tract
• Saliva, vomitus, feces
– Skin, mucous membranes
– Genitourinary tract
• Urine, semen, vaginal secretions
– Blood
– Mother to unborn child
– Artificial openings
Chain of
Infection
Mode of Transmission
• Contact
– Direct
– Indirect
– Droplet
• Airborne
• Other sources of infection
– Example: vector
Chain of
Infection
Mode of Entry
Infectious agent enters the new host
– Respiratory tract
• Breathing contaminated air droplets
– Gastrointestinal tract
• Eating, drinking, hand-to-mouth (fecal-oral route)
– Skin, mucous membranes
• Non-intact skin
• Hand-to-eye and nose
– Genitourinary tract
• Urinary tract, sex
– Blood
– Placenta-to-baby
Chain of
Infection
Susceptible Host
 Immune system, e.g.transplant,
extremes of age,
chemotherapy
 Barrier compromised, e.g. abrasion, burn,
device use, surgical procedure
 Additional factors, e.g. underlying disease,
medications, nutrition, stress
Breaking the Chain
Medical Asepsis
Definition: Purposeful
Prevention of infection by
• Reducing the number of
organisms and
• Preventing their spread
Practices that …….
Keep environment free from contamination
+
Keep patient free of colonization by facility microbes
=
ASEPSIS
* Also protects healthcare workers
Asepsis: Know What Is Clean
• Clean, laundered Linen
• Dishes and utensils after running through
dishwasher or cleaned + sanitized
• Employee hands following hand hygiene
• Item thoroughly washed and/or
disinfected
Asepsis: Know What Is Dirty
“Dirty” – contaminated (e.g. visible soil), used item
• Examples:
• Any obviously soiled item
• The floor
• Any patient’s body fluid
• Soiled/used dressing materials
• Toilet seat soiled with patient’s body fluids
• Gloved hands following personal care
Asepsis: Know What Is
Sterile
Sterile = Absence of all microbes
• Sterile field
• Use sterile supplies – labeled sterile
* Example – delivered in sealed package,
e.g. gauze 4x4, urinary catheter,
intravevenous fluids
Asepsis: Separation & Preventing
Contamination
Keep the three conditions separate
•Don’t allow clean or disinfected items to come in
contact with dirty items
•Clean linen falls on floor – floor considered dirty
Place in laundry for washing
Remedy the contamination immediately
•When you see that dirty, clean, and sterile not
kept apart, do something immediately
•Report any observed breach in technique
Surgical Asepsis
(sterile technique)
Practices that keep an area
or objects free from all
microorganisms
Surgical Asepsis Principles
• Only sterile items are used withint the sterile
field
• Sterile persons are gowned and gloved
• Tables are serile ony at table level
• Sterile persons touch only sterile items or areas
• Unsterile persons avoid reaching over the sterile field
• The edges of anything that encloses sterile contetns
are considered unsterile
• The sterile field is created as close as possible to the
time of use
Principles, continued
• Sterile areas are continuously kept in view
• Sterile person keep well within the sterile area
• Sterile persons keep ontact with sterile areas
to a minimum
Practices
Surgical scrub – gowning - gloving
Precautions to Prevent Transmission of
Infectious Agents
Two tier system (HICPAC 2007)
Standard Precautions
Transmission-Based Precautions
Designed to Supplement Standard Precautions
in patients with documented or suspected
infection/colonization of highly transmissible or
epidemiological important pathogens.
STANDARD PRECAUTIONS
(SP)
• Principle that all blood, body fluids, secretions (except
sweat), excretions, non-intact skin, and mucous
membranes may contain transmissible microbes
• Group of prevention practices that apply to all
patients, regardless of suspected or confirmed
infection status, in any setting in which
healthcare is delivered.
• Application of SP: determined by:
– the nature of the HCW-resident interaction, and
– the extent of anticipated blood, body fluid, or
pathogen exposure (e.g. only gloves for drawing
blood vs gown + gloves to dress a wound with
excess drainage)
 Standard Precautions
• Hand hygiene
• Personal protective equipment (PPE)
– Gloves, gown, face protection
• Patient resuscitation
• Environmental measures
– Cleaning and disinfection
– Soiled patient-care equipment
– Textiles and laundry
• Safe injection practices
• Patient placement
• Respiratory hygiene/cough etiquette
Recommendations chart: http://www.cdc.gov/ncidod/dhap/pdf/guidelines/isolation2007.pef (Table 4, pp 125, 126)
Hand Hygiene: Why?
• Single most important practice to reduce
the transmission of infectious agents in
healthcare settings
• Reduce risk of morbidity, mortality and
cost associated with healthcare-associated
infections
• Eliminate transient organisms and reduce
resident hand flora
Chain of
Infection
Evidence
The relationship between
hand hygiene and HAI’s
• Substantial evidence that hand hygiene
reduces the incidence of infections
• Historical study: Semmelweis
• More recent studies: rates lower when
antiseptic hand hygiene was performed
Hand Hygiene Methods
Hand hygiene is a general term that applies to either
handwashing, antiseptic handwash, alcohol-based handrub, or
surgical hand hygiene/antisepsis.
• Handwashing:
Washing hands with plain soap and water.
• Antiseptic handwash:
Washing hands with water and soap or other detergents
containing an antiseptic agent
• Alcohol-based handrub (ABHR):
Rubbing hands with an alcohol-containing preparation
• Surgical hand hygiene/antisepsis
Handwashing or using an alcohol-based handrub before operations by
surgical personnel
Guideline for Hand Hygiene in Health-care Settings. MMWR 2002; vol. 51, no. RR-16.
Which Method Kills
Bacteria Better?
Good
Better
Plain Soap
Antimicrobial
soap
Best
Alcohol-based
handrub
Time constraint
major obstacle for hand hygiene
• Handwashing (HW) with water and soap
requires 40–60 seconds from start to
finish
 7 times / shift = 56 min.
• Alcohol-based handrubbing (ABHR): 20–30
seconds total;
 7 times / shift = 18 min.
• If HCW used hand hygiene for
every indication in an 8 hr shift:
– HW = 16 hours !
– ABHR = 5 hours
Voss A and Widmer AF, Infect Control Hosp Epidemiol 1997:18;205-208.
Indications for ABHR
All situations where
soap and water are
not required
Dispenser Placement
and Storage
• CMS encourages use of alcohol-based hand rubs
– Dispensers in patient rooms, dining rooms and,
as determined, in all settings
• Placement in corridors and rules for storage should follow
CMS regulations
– Based on NFPA standards published in Federal
Register March 25, 2005, effective May 2005 –
(Criteria pg FR 15237)
 MSIPC website provides specific directions for
locations, e.g. distances between dispensers,
distance from electrical plates
http://www.msipc..org/advocacy.html
Recommended Hand
Hygiene Technique
• Handrubs
– Apply to palm of one hand, rub
hands together covering all
surfaces until dry
• Handwashing
– Wet hands with water, apply soap,
rub hands together for at least 15
seconds
– Rinse and dry with disposable
towel
– Use towel to turn off faucet
Guideline for Hand Hygiene in Health-care Settings. MMWR 2002; vol. 51, no. RR-16.
Indications for Hand Hygiene
NOTE: This list is too prescriptive for inclusion in a policy;
may be useful when teaching risk reduction/task
identification
•
•
•
•
•
•
•
•
When coming on-duty and at shift completion
Before and after patient contact
Between all patient contacts
Before performing invasive procedure
Before medication preparation
Before and after eating
Before donning/after removing gloves
Before and after personal restroom use
HH Indications, cont
• When moving from a contaminated body site to a
clean body site
• After touching inanimate objects that are likely to be
contaminated with pathogenic microorganisms
– Urine measuring/collecting containers
• After contact with objects (including equipment)
located in the patient’s environment
• After touching an animal or animal waste, e.g.
therapy dog, bird
• After touching garbage
• After smoking
WHEN? “My 5 Moments for Hand
Hygiene”
WHO 2009
Hand Hygiene: Patients,
Visitors, Volunteers
• PATIENTS
– Expected minimally to perform hand hygiene before meals
and after personal toilet use
– Nursing staff to review other indications with patient
• VISITORS
– Expected minimally to perform hand hygiene before meals
and after personal restroom use
– If participating in personal patient care, nursing staff will
review product use and indications for hand hygiene
Additional Considerations
•
•
•
•
•
Hand lotion
Nails
Jewelry
Glove use
Adherence
HP Barriers to adherence
• Lack of knowledge that guidelines for
hand hygiene exist
• Not recognizing opportunities during the
performance of one’s duties
• Lack of awareness for the risk of crosscontamination of organisms
Best Practice
• Facility decision regarding hand hygiene
• Input into evaluation and selection of
products
• Educate – proper HH, product safety, how
and when to use
• Competency evaluation and monitoring:
observations, quizzes, skills lab, electronic
monitoring systems, data collection forms,
• Encourage patient/family empowerment
References/Resources
• Strategies to Prevent Healthcare-Associated
Infections Through Hand Hygiene. SHEA
August, 2014
• Canada’s Hand Hygiene Challenge 2012
• Implementing AORN Recommended Practices
for Hand Hygiene
2012
• WHO Guidelines on Hand Hygiene in
Healthcare, 2009
• Guideline for Hand Hygiene in Health Care
Settings, 2002 (HICPAC)
(SP) Personal Protective
Equipment (PPE)
Personal Protective Equipment
Gloves
Gown
Facewear
Gloves
• Body substance – fluid and solids
• Mucous membrane contact – oral, nasal,
conjunctival, rectal, genital
• Non-intact skin – burns, surgical
incisions, open skin lesions
• Device insertion site
• Contaminated items
Gloves
Donning gloves
• If wearing gown, extend
to cover wrist of gown
Removing gloves
- Remember outside of
gloves are contaminated
• Grasp outside of glove
with opposite gloved
hand; peel off
• Hold removed glove in
gloved hand
• Slide fingers of ungloved
hand under remaining
glove at wrist
41
Additional Barriers
• Gown: protect arms and exposed body areas
– Example: if soiling of clothes probable, procedure
likely to generate splashes
• Facewear (mask/goggles/eyewear): protect
conjunctiva, nasal mucosa and mouth
– Example: if procedure likely to generate
splash, unprotected cough,
suctioning
• Resuscitation device: Use Standard
Precautions
Gowns
Gown: protect arms and exposed body
areas
• Example: if soiling of clothes
probable, procedure likely to
generate splashes
Removing gown:
• Unfasten neck, then waist ties
• Remove gown using a peeling
motion; gown will turn inside out
• Hold removed gown away from
body, roll into a bundle and
discard in room
43
How to Decide
• Based on nature of task
• Anticipated degree of contact
with potentially infectious
substance (anything wet)
• Level of protection needed to prevent
fluid penetration
For healthcare personnel (HP) – per
organization policy (all decisions are local)
STOP
PPE: Donning and removing
How hard can it be?
A learned skill?
Does it matter?
Practice makes perfect!
(S.P.) ENVIRONMENTAL
MEASURES
• Cleaning and disinfection
– Daily room cleaning
– Periodic cleaning
– “High touch” surfaces - bedrails,
bedside tables, IV poles, call bells, door
handles, BR surfaces, computer keyboards
• Care of soiled equipment
• Textiles and laundry
(SP) Safe injection
practices
• Use safer needle/sharp technologies, e.g.
needles/syringes, lancets (glucometers)
• Do not recap, bend, break or handmanipulate used needles
• Must recap? Use 1-handed scoop
• Place used sharps in puncture-resistant
container
Resources: MIOSHA, CMS, APIC, and others
CDC: http://www.cdc.gov/injectionsafety/
(S.P.) - Patient Placement
Prioritize for single-patient room if patient
• is at increased risk of transmission
• is likely to contaminate the environment
• does not maintain appropriate hygiene
• is at increased risk of acquiring infection
• developing adverse outcomes following
infection
(SP) Respiratory hygiene/
cough etiquette
Defined: Source containment of infectious
respiratory secretions in symptomatic patients,
beginning at initial point of encounter, e.g.
triage and reception areas in emergency depts.
and physician offices
• Cover nose/mouth when sneezing/coughing
• Use tissues and dispose in no-touch receptacle
• Practice HH after soiling with respiratory
secretions
• Wear surgical mask or maintain spatial
separation more than 3 ft (six feet?) if possible
Examples: Application of SP
• Practices that reduce or eliminate
organisms
–
–
–
–
–
–
Hand hygiene
Clean uncontaminated supplies
PPE/barriers
Sterile solutions
Sterile field when indicated
Preparation of skin
Any questions?