mayo medical laboratories · mayo medical laboratory procedures ©2016 mfmer | slide-32 technique...

5/17/2016

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© MFMER © MFMER

Mayo Medical Laboratories

Virtual Lectures

©2014 MFMER

© MFMER

Virtual Lectures Planning Committee Disclosure Summary

As a provider accredited by ACCME, College of Medicine, Mayo Clinic (Mayo School of CPD) must ensure balance, independence, objectivity and scientific rigor in its educational activities. Course Director(s), Planning Committee Members, Faculty, and all others who are in a position to control the content of this educational activity are required to disclose all relevant financial relationships with any commercial interest related to the subject matter of the educational activity. Safeguards against commercial bias have been put in place. Faculty also will disclose any off label and/or investigational use of pharmaceuticals or instruments discussed in their presentation. Disclosure of these relevant financial relationships will be published in activity materials so those participants in the activity may formulate their own judgments regarding the presentation.

Listed below are individuals with control of the content of this program who have disclosed…

Relevant financial relationship(s) with industry:

None

No relevant financial relationship(s) with industry:

Curtis Hanson, MD – program planning committee

Sharon Preuss – program planning committee

Bobbi Pritt, MD, MSc, DTMH – program planning committee

Cara Schmidt – program planning committee

Audrey Schuetz, MD, MPH – program presenter

References to off-label and/or investigational usage(s) of pharmaceuticals or instruments in their presentation:

None

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©2016 MFMER | slide-3

The Basics of Blood Culture Collection Audrey N. Schuetz, MD, MPH

Clinical Microbiology, Mayo Clinic, Rochester April 2016


I have no relevant financial disclosures.

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After this talk, the participant will be able to:

1. Discuss the procedures to follow for sterile collection of blood

2. State the number of blood culture sets necessary to collect for adequate recovery of clinically significant microorganisms

3. List the reasons that skin site preparation is important in blood culture collection


Blood Cultures Are Important!

• Bloodstream infection is a major cause of morbidity and mortality worldwide

• Costly to healthcare system

• Diagnosis of bloodstream infections is one of the most critical functions of the healthcare team

• Phlebotomy – proper technique

• Clinicians – appropriate ordering

• Laboratory – rapid and accurate testing

http://classroomclipart.com/clipart-view/Clipart/Gray_and_White/Health_and_Medical/23-04-2010_1RGR_jpg.htm

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Bloodstream Infection

• Bacteremia or fungemia = living microorganisms in the blood of a patient

• “-emia” – condition of the blood (Greek)

• Bloodstream infection = microorganisms multiply at a rate exceeding capacity of immune system to clear them


Sepsis

• Implies urgency and severity

• Syndrome of physiologic and biochemical abnormalities caused by infection

• Early diagnosis and appropriate treatment are critical

• Costs attributable to sepsis were $20 billion (5.2%) of total U.S. hospital costs in 2011

Singer M et al. JAMA 2016;315:801

http://classroomclipart.com/clipart-view/Health_Care_and_Medicine/na_12_5_26_jpg.htm

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Sepsis

• One in four patients with sepsis die (often more)

• From 2000 to 2010, mortality from septicemia increased by 17%

• Sicker patients

• People living longer

• Prolonged hospital stays

Buehler SS et al. Clin Microbiol Rev 2016;29:59


Sepsis

• No clear definition of sepsis

• No gold standard diagnostic test

• Only 30-40% of “sepsis” cases are culture-positive

http://www.survivingsepsis.org/Pages/default.aspx

Surviving Sepsis

Campaign

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Sepsis Terminology

• Constellation of findings

• Eg, hypotension, poor organ perfusion, biochemical abnormalities measured in blood

• Overactivated immune response to infection

• Old definition of sepsis:

SIRS Infection System

inflammatory

response

syndrome


Definitions of Sepsis Are Changing!

1991

Sepsis SIRS criteria

Severe sepsis Sepsis + organ

dysfunction

Septic shock Sepsis-

induced

hypotension

despite fluid

resuscitation

Bone RC et al. Crit Care Med 1991;20:864

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1991 2001*

Sepsis SIRS criteria

No

change

Severe sepsis Sepsis + organ

dysfunction


induced

hypotension

despite fluid

resuscitation

*Levy MM et al. Intensive Care Med 2003;29:530



1991 2016**

Sepsis SIRS criteria SEPSIS - Life-threatening

organ dysfunction caused by a

dysregulated host response to

infection Severe sepsis Sepsis + organ

dysfunction


induced

hypotension

despite fluid

resuscitation

SEPTIC SHOCK - Subset of

sepsis in which abnormalities

are profound enough to

substantially affect mortality

**Singer M et al. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA

2016;315:801

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Sepsis Implies Urgency

Table Adapted from Ferrer R et al. Crit Care Med 2014;42:1749

0.2

0.22

0.24

0.26

0.28

0.3

0.32

0.34

0.36

0-1 1-2 2-3 3-4 4-5 5-6 >6

Time to First Antibiotic, hours

Predicted Hospital Mortality


Can I trust that

this positive

blood culture

result

represents a

true infection

and not

contamination?

No growth –

cultures

negative

• Can I trust these negative blood culture

results?

http://classroomclipart.com/clipart-view/Clipart/Health/female_doctor_with_stethoscope_jpg.htm

http://classroomclipart.com/clipart-view/Clipart/Health/female_doctor_with_stethoscope_jpg.htm

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The Role of Phlebotomy in Sepsis

Detecting a bloodstream infection

• Aids in choice of antibiotic therapy

• Decreases mortality and morbidity by treating the infection

Excluding a bloodstream infection

• Allows for cessation of antibiotic therapy

• May reduce the length of hospital stay and associated costs


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What is the single most important factor that influences yield of blood

culture?

A. Blood volume

B. Timing the blood draw to correlate with a fever spike

C. Use of arterial blood rather than venous blood


What Volume of Blood to Draw?

• More microorganisms can be recovered in culture as more blood is drawn

• For adults, 20-30 mL per set is suggested

• For young children, no more than 1% of patient’s total blood volume

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Our Little Ones…

• Blood draws can be difficult

• Higher numbers of bacteria in bloodstream as compared to adults

• In a tertiary care center, 40/133 (30%) of blood cultures for patients <1 month of age were inadequate volume at <0.5mL

Connell TG et al. Pediatrics 2007;119:891


Our Little Ones…

Infants Older Children

Minimal volume 0.5 – 1 mL 1 mL

Optimal volume ≥30 mL


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What Volume of Blood to Draw?

• Normal human blood contains substances which inhibit microbial growth

• Phagocytes, lysozymes, antibodies and antibiotics

• Decrease inhibitory activity of these substances by achieving a blood:broth ratio of 1:5 or 1:10

Blood + Broth


What Is the Composition of Blood Culture Broth?

• Water and nutrients to enhance growth of microorganisms

• Anticoagulant

• Resins (charged beads) or activated charcoal - absorb antimicrobials and provide increased surface area for growth

Tomásdearg92, Wikimedia commons

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Which is considered a blood culture “set”?

A. One bottle from a single venipuncture

B. All bottles from a single venipuncture

C. All bottles from multiple venipunctures during a single day


How Many Sets to Draw?

• One set = all bottles obtained from a single venipuncture or during one catheter draw

• One order = two sets

Photo courtesy of Bobbi Pritt, MD

One set = One venipuncture

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Table adapted from Weinstein MP et al. Rev

Infect Dis 1983;5:35

1 set 2 sets 3 sets

Pathogen

yield

65% 80% 96%

Cockerill FR et al. Clin Infect Dis 2004;38:1724

0102030405060708090

100

1stset

2ndset

3rdset

Blood Cultures Positive (%)

258/282

280/282 281/282



• Draw 2 to 3 sets

• Low quantities of bacteria in blood

• Bacteremia may be intermittent

• Results of a single blood culture set are difficult to interpret

• Recent evidence suggests that 3 to 4 blood culture sets may be optimal

Weinstein MP and Doern GV. J Clin Microbiol 2011;49:S26

Single blood

cultures

should never

be drawn

from adult

patients.

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What Type of Blood Bottle to Use?

• Recommend that paired aerobic/anaerobic bottles be used

• Inoculate the aerobic bottle first if not enough blood (most bacteremias are due to aerobic and facultative bacteria)

• Pediatric patients should have pediatric bottles

• Over 6 month period at a children’s hospital, only 63% of blood cultures were drawn in pediatric blood culture bottles



Example of Blood Bottle Inoculation Guide for Adults

Mayo Medical Laboratory Procedures

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Example of Blood Bottle Inoculation Guide for Children

Mayo Medical Laboratory Procedures


Technique

1. Clean septum of blood bottles with alcohol and allow to dry

2. Disinfect the site of venipuncture

3. Do not palpate the vein after skin disinfection unless a sterile glove is worn

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Standard Skin Prep – Part I

Scrub skin with 70% isopropyl alcohol for 30 seconds and allow to air dry.



Standard Skin Prep – Part II

Apply tincture of iodine to skin in a concentric circle outwards from center. Air dry for 60 seconds.


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Skin Antiseptics


Technique Advantages Disadvantages

Tincture of

iodine

Dry 30-60

seconds after

application

Superior to

povidone-iodine

- Iodine allergy

- Must wash

away after use

Chlorhexidine

gluconate (CG)

Dry after

application

- No need to

wash away after

use

- Superior to

povidone-iodine

Cannot use for

infants < 2

months of age

(skin irritant &

chemical burns)

Povidone-

iodine

Dry for 1.5 to 2

minutes after

application

Inferior to above

products

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Tincture of Iodine vs. Chlorhexidine

• 40 seconds less time spent on skin antisepsis

• 14/15 phlebotomists preferred chlorhexidine since “easier, faster, and less messy”

Barenfanger J et al. J Clin Microbiol 2004;42:2216

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

Tincture of Iodine Chlorhexidine

2.72%

3.13%* *Rates were not

significantly different.

Contamination

Rate

Switch


When to Draw Blood Cultures?

• Draw blood before antibiotics are given

• If no significant delay (>45 minutes) in administering antimicrobials is expected

• Timing between temperature spikes?

• No positivity rate differences were found in relation to fever spikes of patients

Riedel S et al. J Clin Microbiol 2008;46:1381

CLSI. Principles and Procedures for Blood Cultures; Approved Guideline. CLSI document M47-A. 2007.

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Which Sites to Draw Blood?

• Draw from veins, not arteries

• No increased yield with arterial blood

• At least one set should be from peripheral venipuncture

• Blood cultures from indwelling intravascular access devices (catheters and ports) show higher contamination rates than venipuncture draws


Common Sources of Bloodstream Infections

0%

5%

10%

15%

20%

25%

30%

Weinstein M et al. CID 1997;24:584

http://classroomclipart.com/clipart-view/Health_Care_and_Medicine/injection_01_jpg.htm

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CDC National Healthcare Safety Network (NHSN)

• Tracks healthcare-associated infections

• Central line-associated bloodstream infections (CLABSI) reported to CDC

• VitalSigns

http://www.cdc.gov/hai/surveillance/progress-report/index.html


Transport to Laboratory

• Send bottles to laboratory within approximately two hours

• Hold bottles at room temperature

• Do not refrigerate or freeze bottles

• May kill some microorganisms

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What is an acceptable blood culture contamination rate?

A. ≤ 3%

B. One of 10 bottles

C. 7-8%


Skin as a Source of Contamination

• Over 180 bacterial species are found as normal inhabitants of skin

• “Skin flora” or commensals

• Detection of these species in only one of two sets = contaminant

• Bacillus sp. • Corynebacterium sp.

(including C. jeikeium) • Gram-positive bacillus

resembling Corynebacterium sp.

• Micrococcus sp. (and related organisms i.e. Kocuria sp.)

• Propionibacterium sp. • Rothia dentocariosa • Staphylococcus coagulase

negative (including S. lugdunensis)

• Viridans group streptococcus

CDC Common Commensals: http://www.cdc.gov/nhsn/XLS/master-organism-Com-Commensals-Lists.xlsx.

Updated January 2016.

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“Before and After”

Same site, after

proper aseptic

scrub

Culture of site

prior to aseptic

scrub technique

Slide courtesy of Bobbi Pritt, MD


Quality Assurance Monitors MONITOR CRITERIA POSSIBLE ACTION

Contamination

rate

Percentage of positive

cultures determined to be

contaminated; ≤3% is

acceptable

1. Reinforce proper

antiseptic technique

2. Change antiseptics

Overfill and

underfill of blood

bottles

Determined by type of blood

cultures used and

institutional policy

1. Reject overfilled and

underfilled bottles

2. Educate medical

staff as to

importance of

proper blood:broth

ratio

Single blood

culture set within a

24 hour period

Number and percentage of

solitary blood culture set

collected within 24 hours

Stress consensus

recommendations for

collecting 2 or more

sets on a patient

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New Tools in Microbiology Laboratory

1 day 10-18 hours

10-18 hours Molecular panel

Organism name

+/- Antibiotic resistance

2 hours


The Future is NOW…

Highly Sensitive Molecular Testing

Organism name

+/- Antibiotic resistance

8 hours

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Summary

• Sepsis is a serious and urgent condition

• Obtain at least two sets of blood cultures

• Adequate skin site cleansing is critical in reducing contaminants


Questions & Discussion

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