Touch contamination levels during anaesthetic procedures and their relationship to hand hygiene procedures: a clinical audit

A. F. Merry1,2, T. E. Miller3, G. Findon3, C. S. Webster1,2 and S. P. W. Neff1

1Department of Anaesthesia, Green Lane Hospital, Auckland, New Zealand. 2Section of Anaesthesia, Department of Pharmacology and 3Department of Medicine, University of Auckland, New Zealand*Corresponding author

Accepted for publication: September 15, 2000


    Abstract
 Top
 Abstract
 Introduction
 Methods and results
 Results
 Comment
 References
 
After different methods of hand preparation, volunteers rolled segments of sterile central venous catheter between their fingertips, and bacterial transfer was evaluated by standardized quantitative culture. The number of bacteria transferred differed between methods (P<0.001). Comparisons were made with the control group (no preparation at all; median, third quartile and maximum count=6.5, 24, 55). Bacterial transfer was greatly increased with wet hands (1227, 1932, 3254; P<0.001). It was reduced with a new rapid method, based on thorough drying with a combination of 10 s using a cloth towel followed by either 10 or 20 s with a hot-air towel (0, 3, 7 and 0, 4, 30, respectively; P=0.007 and 0.004, respectively). When asked to follow their personal routines, 10 consultant anaesthetists used a range of methods. Collectively, these were not significantly better than control (7.5, 15, 55; P=0.73), and neither was an air towel alone (2.5, 15, 80; P=0.176) nor the hospital’s standard procedure (0, 1, 500; P=0.035). If hand preparation is needed, an adequate and validated method should be used, together with thorough hand drying.

Br J Anaesth 2001; 87: 291–4

Keywords: equipment, sterilization; infection, bacterial contamination; sterilization, skin; anaesthetic techniques, i.v.; anaesthetic techniques, epidural


    Introduction
 Top
 Abstract
 Introduction
 Methods and results
 Results
 Comment
 References
 
The effects of hand preparation on skin microbial flora have been studied,13 but there are few studies in the context of the practising anaesthetist. The issue is of importance during procedures, such as the insertion of central venous or epidural catheters, when meticulous sterility is needed. However, notwithstanding formal guidelines that specify a thorough surgical scrub and the use of a sterile gown,4 we have noticed considerable variation in hand preparation by anaesthetists before sterile procedures.

The aim of washing or scrubbing hands is to reduce to a minimum the transfer of bacteria. Transient contaminants, including Gram-negative bacteria acquired during random contact with various fomites, are readily removed by hand washing. However, hands also harbour resident flora (typically Gram-positive) that are less easily eliminated and that may be transferred by touch. Moisture is a key factor determining the level of touch-associated bacterial transfer following hand washing. We proposed a rapid method of hand drying based on the combined use of a cloth or paper towel and a hot-air towel.1

We audited methods of hand preparation for the insertion of a central venous catheter, used routinely by 10 consultants in our department, and compared the efficacies of these methods with those of the hospital’s standard method, the proposed dual method of hand preparation, and an air towel alone.


    Methods and results
 Top
 Abstract
 Introduction
 Methods and results
 Results
 Comment
 References
 
Subjects
The regional ethics committee accepted the study as an audit. Members of the Department of Anaesthesia, selected in groups of 10 on the basis of availability, participated voluntarily.

Hand preparation methods evaluated
The study procedure was carried out after each of seven approaches to hand preparation:

(1) ‘Pre-test’: dry hands, no prior hand washing;

(2) ‘Wet’: rinsing hands under cold running tap water for 5 s, no drying;

(3) ‘Individual’: individual hand washing procedure routinely used by participants (specified as consultants in this group);

(4) ‘Hospital’: Green Lane Hospital’s standard hand washing procedure, which specifies taking 3 min (in total) for three scrubs with either povidone iodine or chlorhexidine soap, and then drying hands on a sterile towel;

(5) ‘Air-45’: wetting hands under cold running tap water for 5 s, followed by shaking off excess water and placing hands under hot-air drier for 45 s;

(6) ‘Cloth-air-10’: rinsing hands under cold running tap water for 5 s, followed by shaking off of excess water, drying of hands on a cloth towel (non-sterile, reusable pull down variety) and placing hands under hot-air drier for 10 s;

(7) ‘Cloth-air-20’: as for (6), but with hands under hot-air drier for 20 s.

The first two methods were investigated sequentially with the same participants on the same afternoon, but the others were investigated on separate days, with some variation in participants between occasions. Ten consultant anaesthetists in a second major hospital were also asked about their usual approach to hand preparation before central venous catheter insertion.

Study procedure
After performing the hand preparation procedure, participants rolled, in turn, four 2-cm segments of a sterile standard Cook triple-lumen central venous catheter between their fingertips, and then dropped each contaminated segment into 10 ml of sterile saline. This was vortexed for 15 s to dislodge adherent microbes. One millilitre of the suspension was then transferred into a Columbia agar pour plate. Bacterial numbers were evaluated by colony counting after 24 h incubation at 37°C.

Statistics
Data were analysed with Systat 7.0 for Windows. Analysis of variance was undertaken using logarithmically transformed means of the four counts from each individual, with group and participant as independent variables (P<=0.05 designated as significant). Post hoc comparisons were made between the control group (‘Pre-test’) and each of the other groups, using Fisher’s least-significant difference test (P<=0.01 designated as significant to allow for multiple testing).


    Results
 Top
 Abstract
 Introduction
 Methods and results
 Results
 Comment
 References
 
Twenty-eight individuals took part in the entire study. Between them, the 10 consultants in the group designated ‘Individual’ utilized five different hand-washing agents. Only one followed the hospital procedure, and only two used a gown. One anaesthetist used no hand preparation at all. Two participants spent 1 min or more, two spent approximately 30 s, and five spent 15 s or less, washing their hands. Thirty seconds or less was spent on hand drying in all cases, with 15 s or less in five. Six dried their hands on a sterile cloth, and two on an unsterile paper towel. One rinsed with methylated spirits and relied on unaided evaporation for drying. Five out of 10 expressed reluctance to leave an anaesthetized patient with minimal supervision (e.g. a nurse or anaesthetic technician) in order to wash their hands more thoroughly. The 10 consultants questioned in the second major hospital also reported a wide range of hand preparation practices before insertion of central venous catheters. Only six of these reported donning a gown, and two of the six reported following an accepted hospital procedure for hand washing before central venous catheter insertion.

The median, third quartile and maximum number of bacteria transferred to the central venous catheter segments with each method (pooled data, n=40 per group) were, ‘Pre-test’: 6.5, 24, 55; ‘Wet’: 1227, 1932, 3254; ‘Individual’: 7.5, 15, 55; ‘Hospital’: 0, 1, 500; ‘Air-45’: 2.5, 15, 80; ‘Cloth-air-10’: 0, 3, 7; ‘Cloth-air-20’: 0, 4, 30 (Fig. 1). The difference between groups in the number of bacteria transferred was significant (P<0.001). Post hoc comparisons of each group with ‘Pre-test’ showed that significantly more bacteria were transferred with ‘Wet’ (P<0.001), and significantly fewer with ‘Cloth-air-10’ and ‘Cloth-air-20’ (P=0.007 and 0.004, respectively). ‘Hospital’, ‘Individual’, and ‘Air-45’ were not significantly different from ‘Pre-test’ (P=0.035, 0.73 and 0.176, respectively).



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Fig 1 The numbers of bacteria transferred during the seven hand washing methods described in the text (each point relates to one catheter segment).

 

    Comment
 Top
 Abstract
 Introduction
 Methods and results
 Results
 Comment
 References
 
Our method of selecting participants raises the possibility of sample bias. We addressed this by including participant as an independent variable in the analysis of variance. The finding that the hospital’s standard procedure was not significantly different from the control condition (P=0.035) may well be a type II error; the findings in respect of the ‘Wet’, ‘Cloth-air-10’ and ‘Cloth-air-20’ conditions seem secure, particularly given the predominance of counts near zero for ‘Cloth-air-10’ and ‘Cloth-air-20’ (Fig. 1). The observations of hand washing practice are consistent with our personal observations within several hospitals in New Zealand and elsewhere.

When ‘accepted practice’ is routinely violated this usually implies a perception that the violation is harmless and/or that the standard is unreasonable.5 A perception of harmlessness would no doubt reflect a reliance on sterile gloves. However, wearing a gown has been shown to reduce sepsis in relation to central venous catheter insertion,6 and glove leaks have been demonstrated in 1.9–5.5% of unused gloves.7 The perception of unreasonableness is reflected in the expression by five participants of reluctance to leave an anaesthetized patient long enough to carry out a formal hand scrub.

Our data confirm the important role that residual moisture on the hands has in determining the level of bacterial translocation with touch.1 This factor has not been widely appreciated, and may negate the benefit of conscientious hand washing. The bulk of water can be quickly removed from washed hands using cloth or paper towels, but these tend to leave a film of moisture. This film can be removed by brief hand exposure to a current of hot air, but hot air is relatively inefficient for drying larger amounts of water. Although putting air towels in a clinical environment has been questioned,8 other evaluations of the use of hot-air dryers in microbiologically sensitive areas are reassuring.9 The combination of a cloth towel with an air towel seems to offer a method of hand hygiene that is at least as efficacious as formal scrub procedures, but quicker, and therefore, better suited to the pressures of clinical practice and more likely to be adopted routinely.


    Acknowledgements
 
We wish to thank Obex Medical Ltd (New Zealand) who donated the central venous catheters used in this study, Mr K. A. McGrath and Mr A. Beadle for editorial assistance, and Dr C. Frampton for statistical advice.


    References
 Top
 Abstract
 Introduction
 Methods and results
 Results
 Comment
 References
 
1 Patrick DR, Findon G, Miller TE. Residual moisture determines the level of touch-contact-associated bacterial transfer following hand washing. Epidemiol Infect 1997; 119: 319–25[ISI][Medline]

2 Larson EL. APIC guideline for handwashing and hand antisepsis in health care settings. Am J Infect Control 1995; 23: 251–69[ISI][Medline]

3 Handwashing Liaison Group. Hand washing: a modest measure—with big effects (Editorial). BMJ 1999; 318: 686[Free Full Text]

4 Australian and New Zealand College of Anaesthesists. Policy on Infection Control in Anaesthesia (Policy Document P28). Melbourne: The College, 1995

5 Reason J. Human Error. New York: Cambridge University Press, 1990

6 Raad II, Hohn DC, Gilbreath BJ, et al. Prevention of central venous catheter-related infections by using maximal sterile barrier precautions during insertion. Infect Control Hosp Epidemiol 1994; 15: 231–8[ISI][Medline]

7 Albin MS, Bunegin L, Duke ES, Ritter RR, Page CP. Anatomy of a defective barrier: sequential glove leak detection in a surgical and dental environment. Crit Care Med 1992; 20: 170–84[ISI][Medline]

8 Redway K, Knights B, Johnson K. A Comparison of the Anti-bacterial Performance of Two Hand Drying Methods (Textile Towels and Warm Air Dryers) After Artificial Contamination and Washing of Hands. London: University of Westminster, 1995

9 Taylor JH. The Evaluation of the Performance of World Warm Air Hand Driers. Chipping Campden: Campden and Chorleywood Food Research Association, 1996. Report No.: FH/24451/2