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Three Part Question

In [patients presenting to the Emergency Department] does [taking blood cultures from freshly inserted peripheral intravenous cannula rather than by dedicated venepuncture] result in [higher rates of contamination]?

Clinical Scenario

Your hospital has a policy which states that blood cultures should be taken by dedicated venepuncture, rather than from freshly inserted intravenous cannulae, in order to reduce the risk of contamination. You wonder if this is supported by the literature.

Search Strategy

Medline 1950-07/07 using the DIALOG interface.
[culture] AND [(cannula OR catheter)] AND [peripheral] AND [(contamination OR contaminated OR contaminate)] AND [LG=EN]

Search Outcome

Altogether 102 papers were found, of which 4 helped to answer the question posed.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Ramsook C, et al. 2000 USA	2,431 children, (age not specified)	Individual cohort study	Contamination rate	Higher in blood drawn by IV cannula vs. venepuncture (45/1,295 = 3.4% vs. 22/1,0084 = 2.0%, chi-square p=0.043)	Patients on antibiotics/immunocompromised not excluded. Aerobic culture only Different antisepsis protocols for nurses and lab phlebotomists
Isaacman DJ, Karasic RB. 1990 USA	99 children under 18 years old, mean age 52.2 months, median 22.9 months; excluding patients who had received antibiotics in previous 48 hours, significant skin disease, immunodeficiency or povidone-iodine sensitivity. Two cultures taken	Individual cohort study	Contamination rate	No difference between IV cannula samples and those from dedicated phlebotomy (1/99 vs. 1/99).	Small numbers with only 2 contaminated cultures 1 from IV line and 1 from standard (the standard culture was from a child with complex congenital heart disease). Nursing staff aware of study.
Norberg A et al. 2003 USA	Study in two phases: first phase when cultures were taken from freshly inserted IV cannulae; second phase when specimens taken by dedicated venepuncture. 4,108 blood cultures; 2,108 from IV cannula; 2,000 from dedicated phlebotomy. Patients with indwelling devices excluded from study.	Observational study	Contamination rate	Higher in IV cannula group: 191/2108; from dedicated phlebotomy 56/2000, chi-square, p<0.001.	There may have been more selective ordering of blood cultures in the second phase when physicians realised that this would require additional venepuncture, compared to the first phase when cultures were taken from intravenous cannulae.
Smart D et al. 1993 Australia	All ED patients (940) assessed as requiring blood cultures (mean age 59 years) 286 needle change before inoculation; 141 no needle change before inoculation; 437 by IV cannula.	Individual cohort study	Contamination rate	No significant difference between groups.	8% (76) of patients excluded for 'protocol violations; - inadequate documentation/antisepsis and incorrect technique (5)

Clinical Bottom Line

Taking blood samples for culture from a freshly inserted IV cannula appears to be associated with higher rates of contamination than when samples are taken by dedicated venepuncture. Additionally, in the papers we looked at, there is no convincing evidence that the isolation of true pathogens is affected by collection method.

References

1. Ramsook C, Childers K, Cron SG, Nirken M. Comparison of blood-culture contamination rates in a pediatric emergency room: newly inserted intravenous catheters versus venipuncture. 2000 Oct;21(10):649-51.
2. Isaacman DJ, Karasic RB. Utility of collecting blood cultures through newly inserted intravenous catheters. 1990 Nov;9(11):815-8.
3. Norberg A, Christopher NC, Ramundo ML, Bower JR, Berman SA. Contamination rates of blood cultures obtained by dedicated phlebotomy vs intravenous catheter. 2003 Feb 12;289(6):726-9.Click here to read
4. Smart D, Baggoley C, Head J, Noble D, Wetherall B, Gordon DL. Effect of needle changing and intravenous cannula collection on blood culture contamination rates. 1993 Jul;22(7):1164-8.