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Needlestick injuries: mechanisms and control
Journal
of Hospital
Infection
Needlestick
(1988)
12, 315-322
injuries:
mechanisms
and
control
ID. A. Kennedy
Supplies Technology Division, NHS Procurement Directorate, Department of Health and Social Security, 14, Russell Square, London WClB 5EP UK
Summary: Consideration of a linear model for venepuncture and patterns that emerge from the literature can help to understand the occurrence of occupational needlestick injuries which are common in healthcare workers. A systematic approach can also help in evaluation of potential control measures and in cost-benefit analysis. Keywords:
Occupational
injury;
needlestick
injuries;
healthcare
workers.
Introduction
A review of the literature on microbiological hazards of occupational needlestick (ONS) and sharps injuries shows that a broad spectrum of infections have been ascribed to these injuries. Most surveys demonstrate that nursing staff are a particularly at-risk group although ancillary workers and laboratory staff are also affected (Collins & Kennedy, 1987). Of special interest is a survey of occupational injuries treated in a representative sample of hospital emergency rooms in the USA (CDC, 1983). The total number of reported injuries was 3,199,359, of which 823,343 (26%) were finger injuries. Lacerations caused by knives were the most frequent single cause (10% of occupational injuries) but ranked next in order were puncture wounds from hypodermic needles which accounted for 9% of occupational injuries. However, it is not only hypodermic needles that are involved in ONS. A recent examination of the accident book of a chemical pathology department identified 11 ONS injuries arising from various pieces of analytical equipment. These included ONS by sampling probes and a small cluster of incidents associated with a blolod glucose analyser that required the use of a syringe fitted with a fixed needle to introduce the sample. The use of such a device for pipetting is deprecated (WHO, 1983). There has been growth in recognition of the potential hazards of ONS for healthcare workers. This development, not unexpectedly, appears to parallel the awareness of the potential for transmission of HIV and HBV in those who are directly or indirectly exposed to blood or other body fluids. It is calculated that the mean volume of blood inoculated in a simulated ONS with a 22 gauge needle is in the region of 1 PL (Napoli & McGowan, 1987). 0195-6701/88/080315+08
SO3.00,O
0 1988 The Hospital
315
infection
Society
316
D. A. Kennedy
Here, it is important to note that experience in the USA indicates that the risk of seroconversion after ONS with HIV infectious blood is less than 1% while the risk of developing HBV infection after- ONS with contaminated blood is 6-30% (National Committee for Clinical Laboratory Standards, 1987). Moreover, no evidence of the transmission of HIV is reported in a recent UK prospective study of 150 healthcare workers accidentally exposed to blood or body fluids from patients infected with HIV (McEvoy et al., 1987). The commercial exploitation of ideas for devices to control ONS is also developing. There is a need to evaluate these ideas in the light of the known circumstances of ONS and frequencies of occurrence. The paper considers this aspect. Opportunities
for ONS
and
potential
risk
zones
Kletz (1976) argues that there is a need to predict accidents before they occur and that by collecting information on human failure rates it is possible to do this, so that preventative action can be taken. In order to understand the occurrence of ONS, a systematic approach can be used. Venepuncture with syringe and needle is chosen as a model system because it contains elements of a range of healthcare manipulations involving needles. Furthermore, venepuncture is very common: it is estimated that in 1983 at least 80 million blood samples were taken in England (Supplies Technology Division, 1986). Other activities involving needles or sharps can be modelled similarly if required. Figure 1, a simple event tree, outlines venepuncture as a linear system which for reference purposes is divided into six different zones. The venepuncture system ends with disposal of the needle into a purpose-made sharps container because this is the preferred (Jeffries, 1987) and commonest practice in the UK. Zone 1 The needle is fitted to the syringe and is unsheathed. Until the needle is unsheathed, ONS is most unlikely unless considerable force is applied to drive the needle through the sheath. Whatever happens in this zone, the needle is uncontaminated with body fluid. Zone 2 The needle is inserted into a vein and blood is drawn into the syringe. Then, the needle is withdrawn from the vein. ONS is possible but the frequency is unknown: the needle is contaminated as soon as it comes into contact with blood. Zone 3 Two options are given. The needle is removed without sheathing (pathway A) or it is sheathed before removal (pathway B). Removal of the needle is recommended before discharge of blood into the specimen tube (Health Service Advisory Committee, 1985) and needle forceps offer a safe method of removal (DHSS, 1978). ONS is possible and the needle is contaminated. The frequency of ONS when removing needles is unknown but approximately 40% of ONS occur during resheathing and the practice is discouraged in official UK and USA guidelines (Advisory Committee on Dangerous Pathogens, 1986; CDC, 1985). It is reported that a needle may
Needlestick
injuries:
mechanisms
Fit needle ond unsheoth
2
into
control
317
I+
vein-draw
Wlthdrow
Pathwoy
and
needle
A
Pathway
B
r--i___:
3
Remove
needle I
Hondle/dlspose of sharps co,~+a,ner
6
Figure 1. Opportunities with syringe and needle.
I
for
occupational
needlestick
(ONS)
injury
during
venepuncture
pierce its sheath, may catch the side of the sheath and break off, or the sheath may fall off (Jagger, Pearson & Brand, 1986). The use of an evacuated blood collection system circumvents the need to remove the needle before discharging the blood into the container. Zone 4 The unsheathed needle is put into a sharps container. ONS is possible, especially if the sharps container is not close to the venepuncture activity (Collins & Kennedy, 1987) but the frequency is unknown. The needle is contaminated. ONS with the sheathed needle is most unlikely but the sheath may fall off (Jagger et al., 1986). The frequency of ONS associated with this is unknown. Contact with exposed needles during disposal, e.g. in the sharps container, may cause ONS. Zone 5 Disposal of the used syringe may give rise to ONS if there is contact with exposed needles n-r the sharps container. Zone 6 The sheathed or unsheathed needle is inside the sharps container. Many ONS occur because unsheathed needles penetrate the sides and
318
D. A. Kennedy
bottoms of sharps containers. It seems unlikely that a sheathed needle would penetrate a sharps container except under the most unusual circumstances. Mechanics
of ONS
and
controls
ONS and sharps injuries can be considered to be mechanical hazards, ie the hazard content is the result of contact between a person, or part of him, and a sharp object when one or both are movz?zg (Kennedy, 1988). From this perspective, three patterns can be identified from reports of ONS in the literature reviewed by Collins & Kennedy (1987). It is possible that these highlight the features of ONS in general. One person and both hands working together This can be illustrated by looking at resheathing incidents. Here, it is possible that both the needle and the sheath can move as one is advanced towards the other; i.e. both hands are working together but are not necessarily synchronized. But the safety of the procedure depends upon synchrony and co-ordination of hand movements resulting in accurate alignment of needle and the sheath. Another, perhaps the most important, reason for ONS is that the mouth of a conventional sheath is relatively small. The tip of the needle often hits the outer surface of the sheath before placement within the mouth, so that fingers holding the sheath may be struck and penetrated by the moving needle (Sumner, 1985). Similar problems have been described when collecting urine from tubing attached to drainage bags: needles can bend or go through the tubing into fingers (Collins & Kennedy, 1987). In view of these incidents it can be conjectured that the tolerance, or “distance” dividing a safe act from an unsafe one is small. In short, a safe act amounts to the hand not holding the needle being in the right place at the right time. It is easy to see how a person who is resheathing a needle can “go out of tolerance”, particularly if there are distractions such as ringing telephones or questions put by colleagues or patients. Poor lighting and fatigue may be implicated too (McCormick & Maki, 1981). Nixon et al. (1986) describe a commercially-available device, the “Needle Guard”, that permits safer resheathing. This is a simple plastic shield with a hole to accept the needle sheath. After the needle has been used the sheath is picked up with the fingers behind the shield. The needle is then guided into the sheath and the whole ejected into the sharps container. Goldwater (1987) reports that 2 year’s experience with this device shows a 82% reduction in the rate of ONS. It is thought that control devices should not require the movement of hands towards a contaminated needle (Jagger et al., 1986). The “Safe T Cap”, a device that permits single handed resheathing, has gained acceptance in a busy nuclear medicine department (Bessent, Donnet &
Needlestick
injuries:
mechanisms
and control
319
Shaw, 1987). It consists of a bench-mounted cylinder of hard plastics material having three vertical holes to accommodate sheaths of commonly-used needles. A sheath is placed in a hole with its mouth uppermost. A used needle is resheathed by introducing the tip of the needle and syringe assembly into the mouth of the sheath using a single handed movement, then applying vertical downwards pressure. A similar device to permit single-handed resheathing of the needle of an evacuated blood collection system and one folr dental needles is available (Samaranayake, 1987). Allied to this class of ONS control devices are sharps containers with integral needle removal facilities. One of these is described by Fisch, Prazuck & Lafaix (1987). A commercial version designed originally for use with double-ended dental needles is a rigid plastics container with an irremovable lid. The lid is fitted with a slot into which the needle hub is introduced and then locked into place by an integral mechanism. This facilitates the removal of the needle. After unlocking, the needle drops into the container and is inaccessible to all but the most determined person. Two people working together Heim (cited by Fricke, 1919) warns of the danger when four hands are working together and takes the view that experimental animals should never be given to an assistant to hold. Accordingly, Fricke’s manual of laboratory safety (Fricke, 1919) shows some ingenious restraining devices that enable a single worker to inoculate animals. It is clear that a struggling animal would be another factor in this opportunity for asynchrony. Furthermore, the distance between the hand of the assistant and the targetted part of the experimental animal that he is holding is small. Webber (1956) further illustrates the dangers of hand-asynchrony. He describes an incident where two workers were sitting on opposite sides of specially-constructed inoculation hood. One presented bottles of culture medium to his partner who inoculated them with tubercle bacilli using a Pasteur pipette. The assistant brought his right index finger sharply against the tip of the pipette held by the inoculator and it penetrated the assistant’s skin. In another ONS example an autoanalyser was started by one laboratory worker while another was adjusting the sample probe. ONS injuries can arise during emergency treatment when syringe and needle assemblies are quickly passed from one person to another (Collins & Kennedy, 1987). Again, the tolerances separating a safe act from an unsafe one are seen to be small. One person and an unmoving sharp object It is reported that used syringes and needles are sometimes pushed into already overfilled sharps containers so that hands can come into contact with upwards pointing needles. Sometimes the contents of sharps containers are packed down by hand to accommodate more sharps and ONS results. Brushing against a bulging sharps container, picking it up or
320
D. A. Kennedy
holding it against the body while carrying it, may give rise to ONS if needles can penetrate at the point of contact. Furthermore, needles may penetrate through the walls of some containers (Bessent et al., 1987) before they are handled. It can be seen that the risk of ONS decreases if needles are resheathed before disposal into a sharps container, after which the contaminated needle is effectively double-sheathed. Otherwise, a container resistant to penetration is necessary. Ribner et al., (1987) conclude that rigid, puncture resistant containers can substantially decrease disposal-related ONS. An adequate supply of sharps containers, available whenever they are needed, should avoid the commonest cause of overfilling (Collins & Kennedy, 1987). Discussion
In the USA, to prevent ONS it is advocated that needles should not be recapped, purposefully bent, broken, removed from disposable syringes or otherwise manipulated by hand (CDC, 1985). A similar view is taken in the UK where it is held that no attempt should be made to resheath needles and they should be placed immediately in safe sharps disposal containers after use (Jeffries, 1987). On the other hand, in New Zealand (Nixon et al., 1986) and in Australia (Goldwater, 1987) the effectiveness and rationality of non-resheathing policies is being questioned. With reference to Figure 1, and consideration of the patterns that emerge from an extensive literature search (Collins & Kennedy, 1987) it can be argued that some strategies to minimize ONS are effectively trade-offs, one against another. In other words, resheathing a used needle without a shielding device, or by using both hands, is a hazard in itself. But it minimizes opportunities for ONS downstream of the resheathing activity and especially those associated with handling and disposal of sharps containers, an area where domestic and portering staff may be innocent victims (Reed, Anderson & Hodges, 1980). However, a resheathing device will not prevent ONS between withdrawal of the needle from a vein (Zone 2 of the model) and the use of the device. And where a needle is not sheathed between its removal from a vein and its disposal into the sharps container there are also opportunities for ONS. It has been stated that a long-term prevention effort must include modifications to the design of needled instruments and these should be simple enough to use without special training or additional equipment (Jagger et al., 1986). Two devices have be described that would appear to offer protection against ONS in all the zones of Figure 1. In one, (Hodges, 1987) the needle has an integral sheath which is retracted by the user to expose the needle. After use the sheath is pushed back by the user and locks into position over the needle. It is claimed that the needle cannot be re-used and can be safely thrown into a sharps
Needlestick
injuries:
mechanisms
and control
321
container. The other (Moore, 1986) h as a light spring-loaded integral sheath which after it has been slightly twisted to expose the needle point, slides back as the needle is introduced into the vein. As the needle is withdrawn, the spring pushes the sheath back and when the needle is covered it locks into place for safe disposal. The manufacturer of the spring-loaded device recently arranged a trial of a small pre-production batch by some laboratory staff and it is understood that they found its use in venepuncture very encouraging. A bigger trial is being set up currently by DHSS and it is hoped that a report can be published in the summer of 1988. ONS control devices can increase operating costs and it will be necessary to analyse the cost-benefits (Ribner et al., 1987) before deciding on routine use; and a systematic approach is recom.mended. The opinions those of the
expressed Department
in this paper are those of the of Health and Social Security.
author
and
do not
necessarily
reflect
References Advisory Committee on Dangerous Pathogens 1986, LAVjHTLV III-the causative agent of AIDS and related conditions, London, DHSS. Bessent, R. G., Donnet, R. & Shaw, A. (1987). Device to permit recapping of syringes without risk of infection. British Medical Yournal295. 307-308. Communicable Diseases Center (1983). -Current trends in occupational finger injuries-United States 1982 Morbidity and Mortality Weekly Report 32, 589-591. Communicable Diseases Center (1985). Recommendations for preventing transmission of infection with human T-lymphotropic virus Type III/lymphadenopathy-associated virus in the worknlace. Summarv. Morbiditv and Mortalitv Weeklv Rebort 34.681-695. Collins, C. H. & Kennedy, D. A. (1987). A review. Microbiological hazards of occupational needlestick and “sharps” injuries. rournal of Applied Bacteriology 62, 385-402. Department of Health and Social Security (1978). Code of practice for the prevention of . infection in laboratories and post-mortem rooms, p.15. London, HMSO: Fisch, A., Prazuck, T. & Lafaix, C., (1987). D evice to permit recapping of syringes without risk of infection. British Medical Journal 292, 668. Fricke, W. (1919). Schutzmassnahmen bei bakteriologischem and serologischem Arbeiten, p. 47. Jena, Gustav Fischer. Goldwater, P. N. (1987). Device to permit recapping of syringes without risk of infection. British Medical Journal 292, 668. Hodges, K. (1987). AIDS-sheathing the syringe problem, New Scientist, 113 (1542), 39. Health Service Advisory Committee 1985, Safety in health service laboratories: hepatitis B. Health and Safety Commission, London, HMSO. Jagger, J., Pearson, R. D. & Brand, J. J. (1986). Avoiding the hazards of sharp instruments. Lancet i, 1275. Jeffries, D. (1987). ABC of AIDS. Control of infection policies. British MedicalJournal 295, 33-35. Kennedy, D. A. (1988). Equipment-.related hazards, Chapter 2, p. 19. In Safety in Clinical and Biomedical Laboratories, (Collins, C. H., Ed) Chapman and Hall, London. Kletz, T. A. (1976). Accident data-the need for a new look at the sort of data that are collected and analysed Journal of Occupational Accidents 95-105. McCormick, R. D. & Maki, D. G. (1981). Epidemiology of needlestick injuries in hospital personnel American Journal of Medicine 70, 928-932. Moore, T. (1986). Syringe is unique. Sunday Times. 26 October. McEvoy, M., Porter, K., Mortimer, P., Simmons, N. & Shanson, D. (1987). Prospective study of clinical, laboratory, and ancillary staff with accidental exposures to blood or
D. A. Kennedy
322 body
fluids from patients infected with HIV. British Medical Journal 294, 1595-l 597. V. M. & McGowan, J. E. (1987). How much blood is in a needlestick? TheJournal of Infectious Diseases 15.5, 828. National Committee for Clinical Laboratory Standards, 1987, Proposed guideline. Protection of laboratory workers from infectious diseases transmitted by blood and tissue, NCCLS document M29-P, Vol. 7, No. 9. National Committee for Clinical Laboratory Standards, Villanova, USA. Nixon, A. D., Law, R., Officer, J. A., Cleland, J. F. & Goldwater, P. N. (1986). Simple device to prevent accidental needle-prick injuries. Lancet i, 888-889. Reed, J. S., Anderson, A. & Hodges, G. R. (1980). Needlestick and puncture wounds: definition of the problem. American Journal of Infectious Control 8, 101-106. Ribner, B. S., Landry, M. Gholson, G. L. & Linden, L. A. (1987). Impact of a rigid, puncture resistant container system upon needlestick injuries. Infection Control 8, 63-66. Samaranayake, L. (1987). Rims and needles The Dentist, 16-17 June. Supplies Technology Division (1986). Blood specimen collection: costing and other implications of changing systems, STD/86/37, Supplies Technology Division, NHS Procurement Directorate, London, DHSS. Sumner, W. (1985). Needlecaps to prevent needlestick injuries. Infection Control 6,495-+97. Webber, W. J. (1956). Laboratory infection with Mycobacterium tuberculosis, Journal of Medical Laboratory Technology 13, 489. World Health Organisation (1983). Laboratory Biosafety Manual, p.10. Geneva, World Health Organisation. Napoli,
of Hospital
Infection
Needlestick
(1988)
12, 315-322
injuries:
mechanisms
and
control
ID. A. Kennedy
Supplies Technology Division, NHS Procurement Directorate, Department of Health and Social Security, 14, Russell Square, London WClB 5EP UK
Summary: Consideration of a linear model for venepuncture and patterns that emerge from the literature can help to understand the occurrence of occupational needlestick injuries which are common in healthcare workers. A systematic approach can also help in evaluation of potential control measures and in cost-benefit analysis. Keywords:
Occupational
injury;
needlestick
injuries;
healthcare
workers.
Introduction
A review of the literature on microbiological hazards of occupational needlestick (ONS) and sharps injuries shows that a broad spectrum of infections have been ascribed to these injuries. Most surveys demonstrate that nursing staff are a particularly at-risk group although ancillary workers and laboratory staff are also affected (Collins & Kennedy, 1987). Of special interest is a survey of occupational injuries treated in a representative sample of hospital emergency rooms in the USA (CDC, 1983). The total number of reported injuries was 3,199,359, of which 823,343 (26%) were finger injuries. Lacerations caused by knives were the most frequent single cause (10% of occupational injuries) but ranked next in order were puncture wounds from hypodermic needles which accounted for 9% of occupational injuries. However, it is not only hypodermic needles that are involved in ONS. A recent examination of the accident book of a chemical pathology department identified 11 ONS injuries arising from various pieces of analytical equipment. These included ONS by sampling probes and a small cluster of incidents associated with a blolod glucose analyser that required the use of a syringe fitted with a fixed needle to introduce the sample. The use of such a device for pipetting is deprecated (WHO, 1983). There has been growth in recognition of the potential hazards of ONS for healthcare workers. This development, not unexpectedly, appears to parallel the awareness of the potential for transmission of HIV and HBV in those who are directly or indirectly exposed to blood or other body fluids. It is calculated that the mean volume of blood inoculated in a simulated ONS with a 22 gauge needle is in the region of 1 PL (Napoli & McGowan, 1987). 0195-6701/88/080315+08
SO3.00,O
0 1988 The Hospital
315
infection
Society
316
D. A. Kennedy
Here, it is important to note that experience in the USA indicates that the risk of seroconversion after ONS with HIV infectious blood is less than 1% while the risk of developing HBV infection after- ONS with contaminated blood is 6-30% (National Committee for Clinical Laboratory Standards, 1987). Moreover, no evidence of the transmission of HIV is reported in a recent UK prospective study of 150 healthcare workers accidentally exposed to blood or body fluids from patients infected with HIV (McEvoy et al., 1987). The commercial exploitation of ideas for devices to control ONS is also developing. There is a need to evaluate these ideas in the light of the known circumstances of ONS and frequencies of occurrence. The paper considers this aspect. Opportunities
for ONS
and
potential
risk
zones
Kletz (1976) argues that there is a need to predict accidents before they occur and that by collecting information on human failure rates it is possible to do this, so that preventative action can be taken. In order to understand the occurrence of ONS, a systematic approach can be used. Venepuncture with syringe and needle is chosen as a model system because it contains elements of a range of healthcare manipulations involving needles. Furthermore, venepuncture is very common: it is estimated that in 1983 at least 80 million blood samples were taken in England (Supplies Technology Division, 1986). Other activities involving needles or sharps can be modelled similarly if required. Figure 1, a simple event tree, outlines venepuncture as a linear system which for reference purposes is divided into six different zones. The venepuncture system ends with disposal of the needle into a purpose-made sharps container because this is the preferred (Jeffries, 1987) and commonest practice in the UK. Zone 1 The needle is fitted to the syringe and is unsheathed. Until the needle is unsheathed, ONS is most unlikely unless considerable force is applied to drive the needle through the sheath. Whatever happens in this zone, the needle is uncontaminated with body fluid. Zone 2 The needle is inserted into a vein and blood is drawn into the syringe. Then, the needle is withdrawn from the vein. ONS is possible but the frequency is unknown: the needle is contaminated as soon as it comes into contact with blood. Zone 3 Two options are given. The needle is removed without sheathing (pathway A) or it is sheathed before removal (pathway B). Removal of the needle is recommended before discharge of blood into the specimen tube (Health Service Advisory Committee, 1985) and needle forceps offer a safe method of removal (DHSS, 1978). ONS is possible and the needle is contaminated. The frequency of ONS when removing needles is unknown but approximately 40% of ONS occur during resheathing and the practice is discouraged in official UK and USA guidelines (Advisory Committee on Dangerous Pathogens, 1986; CDC, 1985). It is reported that a needle may
Needlestick
injuries:
mechanisms
Fit needle ond unsheoth
2
into
control
317
I+
vein-draw
Wlthdrow
Pathwoy
and
needle
A
Pathway
B
r--i___:
3
Remove
needle I
Hondle/dlspose of sharps co,~+a,ner
6
Figure 1. Opportunities with syringe and needle.
I
for
occupational
needlestick
(ONS)
injury
during
venepuncture
pierce its sheath, may catch the side of the sheath and break off, or the sheath may fall off (Jagger, Pearson & Brand, 1986). The use of an evacuated blood collection system circumvents the need to remove the needle before discharging the blood into the container. Zone 4 The unsheathed needle is put into a sharps container. ONS is possible, especially if the sharps container is not close to the venepuncture activity (Collins & Kennedy, 1987) but the frequency is unknown. The needle is contaminated. ONS with the sheathed needle is most unlikely but the sheath may fall off (Jagger et al., 1986). The frequency of ONS associated with this is unknown. Contact with exposed needles during disposal, e.g. in the sharps container, may cause ONS. Zone 5 Disposal of the used syringe may give rise to ONS if there is contact with exposed needles n-r the sharps container. Zone 6 The sheathed or unsheathed needle is inside the sharps container. Many ONS occur because unsheathed needles penetrate the sides and
318
D. A. Kennedy
bottoms of sharps containers. It seems unlikely that a sheathed needle would penetrate a sharps container except under the most unusual circumstances. Mechanics
of ONS
and
controls
ONS and sharps injuries can be considered to be mechanical hazards, ie the hazard content is the result of contact between a person, or part of him, and a sharp object when one or both are movz?zg (Kennedy, 1988). From this perspective, three patterns can be identified from reports of ONS in the literature reviewed by Collins & Kennedy (1987). It is possible that these highlight the features of ONS in general. One person and both hands working together This can be illustrated by looking at resheathing incidents. Here, it is possible that both the needle and the sheath can move as one is advanced towards the other; i.e. both hands are working together but are not necessarily synchronized. But the safety of the procedure depends upon synchrony and co-ordination of hand movements resulting in accurate alignment of needle and the sheath. Another, perhaps the most important, reason for ONS is that the mouth of a conventional sheath is relatively small. The tip of the needle often hits the outer surface of the sheath before placement within the mouth, so that fingers holding the sheath may be struck and penetrated by the moving needle (Sumner, 1985). Similar problems have been described when collecting urine from tubing attached to drainage bags: needles can bend or go through the tubing into fingers (Collins & Kennedy, 1987). In view of these incidents it can be conjectured that the tolerance, or “distance” dividing a safe act from an unsafe one is small. In short, a safe act amounts to the hand not holding the needle being in the right place at the right time. It is easy to see how a person who is resheathing a needle can “go out of tolerance”, particularly if there are distractions such as ringing telephones or questions put by colleagues or patients. Poor lighting and fatigue may be implicated too (McCormick & Maki, 1981). Nixon et al. (1986) describe a commercially-available device, the “Needle Guard”, that permits safer resheathing. This is a simple plastic shield with a hole to accept the needle sheath. After the needle has been used the sheath is picked up with the fingers behind the shield. The needle is then guided into the sheath and the whole ejected into the sharps container. Goldwater (1987) reports that 2 year’s experience with this device shows a 82% reduction in the rate of ONS. It is thought that control devices should not require the movement of hands towards a contaminated needle (Jagger et al., 1986). The “Safe T Cap”, a device that permits single handed resheathing, has gained acceptance in a busy nuclear medicine department (Bessent, Donnet &
Needlestick
injuries:
mechanisms
and control
319
Shaw, 1987). It consists of a bench-mounted cylinder of hard plastics material having three vertical holes to accommodate sheaths of commonly-used needles. A sheath is placed in a hole with its mouth uppermost. A used needle is resheathed by introducing the tip of the needle and syringe assembly into the mouth of the sheath using a single handed movement, then applying vertical downwards pressure. A similar device to permit single-handed resheathing of the needle of an evacuated blood collection system and one folr dental needles is available (Samaranayake, 1987). Allied to this class of ONS control devices are sharps containers with integral needle removal facilities. One of these is described by Fisch, Prazuck & Lafaix (1987). A commercial version designed originally for use with double-ended dental needles is a rigid plastics container with an irremovable lid. The lid is fitted with a slot into which the needle hub is introduced and then locked into place by an integral mechanism. This facilitates the removal of the needle. After unlocking, the needle drops into the container and is inaccessible to all but the most determined person. Two people working together Heim (cited by Fricke, 1919) warns of the danger when four hands are working together and takes the view that experimental animals should never be given to an assistant to hold. Accordingly, Fricke’s manual of laboratory safety (Fricke, 1919) shows some ingenious restraining devices that enable a single worker to inoculate animals. It is clear that a struggling animal would be another factor in this opportunity for asynchrony. Furthermore, the distance between the hand of the assistant and the targetted part of the experimental animal that he is holding is small. Webber (1956) further illustrates the dangers of hand-asynchrony. He describes an incident where two workers were sitting on opposite sides of specially-constructed inoculation hood. One presented bottles of culture medium to his partner who inoculated them with tubercle bacilli using a Pasteur pipette. The assistant brought his right index finger sharply against the tip of the pipette held by the inoculator and it penetrated the assistant’s skin. In another ONS example an autoanalyser was started by one laboratory worker while another was adjusting the sample probe. ONS injuries can arise during emergency treatment when syringe and needle assemblies are quickly passed from one person to another (Collins & Kennedy, 1987). Again, the tolerances separating a safe act from an unsafe one are seen to be small. One person and an unmoving sharp object It is reported that used syringes and needles are sometimes pushed into already overfilled sharps containers so that hands can come into contact with upwards pointing needles. Sometimes the contents of sharps containers are packed down by hand to accommodate more sharps and ONS results. Brushing against a bulging sharps container, picking it up or
320
D. A. Kennedy
holding it against the body while carrying it, may give rise to ONS if needles can penetrate at the point of contact. Furthermore, needles may penetrate through the walls of some containers (Bessent et al., 1987) before they are handled. It can be seen that the risk of ONS decreases if needles are resheathed before disposal into a sharps container, after which the contaminated needle is effectively double-sheathed. Otherwise, a container resistant to penetration is necessary. Ribner et al., (1987) conclude that rigid, puncture resistant containers can substantially decrease disposal-related ONS. An adequate supply of sharps containers, available whenever they are needed, should avoid the commonest cause of overfilling (Collins & Kennedy, 1987). Discussion
In the USA, to prevent ONS it is advocated that needles should not be recapped, purposefully bent, broken, removed from disposable syringes or otherwise manipulated by hand (CDC, 1985). A similar view is taken in the UK where it is held that no attempt should be made to resheath needles and they should be placed immediately in safe sharps disposal containers after use (Jeffries, 1987). On the other hand, in New Zealand (Nixon et al., 1986) and in Australia (Goldwater, 1987) the effectiveness and rationality of non-resheathing policies is being questioned. With reference to Figure 1, and consideration of the patterns that emerge from an extensive literature search (Collins & Kennedy, 1987) it can be argued that some strategies to minimize ONS are effectively trade-offs, one against another. In other words, resheathing a used needle without a shielding device, or by using both hands, is a hazard in itself. But it minimizes opportunities for ONS downstream of the resheathing activity and especially those associated with handling and disposal of sharps containers, an area where domestic and portering staff may be innocent victims (Reed, Anderson & Hodges, 1980). However, a resheathing device will not prevent ONS between withdrawal of the needle from a vein (Zone 2 of the model) and the use of the device. And where a needle is not sheathed between its removal from a vein and its disposal into the sharps container there are also opportunities for ONS. It has been stated that a long-term prevention effort must include modifications to the design of needled instruments and these should be simple enough to use without special training or additional equipment (Jagger et al., 1986). Two devices have be described that would appear to offer protection against ONS in all the zones of Figure 1. In one, (Hodges, 1987) the needle has an integral sheath which is retracted by the user to expose the needle. After use the sheath is pushed back by the user and locks into position over the needle. It is claimed that the needle cannot be re-used and can be safely thrown into a sharps
Needlestick
injuries:
mechanisms
and control
321
container. The other (Moore, 1986) h as a light spring-loaded integral sheath which after it has been slightly twisted to expose the needle point, slides back as the needle is introduced into the vein. As the needle is withdrawn, the spring pushes the sheath back and when the needle is covered it locks into place for safe disposal. The manufacturer of the spring-loaded device recently arranged a trial of a small pre-production batch by some laboratory staff and it is understood that they found its use in venepuncture very encouraging. A bigger trial is being set up currently by DHSS and it is hoped that a report can be published in the summer of 1988. ONS control devices can increase operating costs and it will be necessary to analyse the cost-benefits (Ribner et al., 1987) before deciding on routine use; and a systematic approach is recom.mended. The opinions those of the
expressed Department
in this paper are those of the of Health and Social Security.
author
and
do not
necessarily
reflect
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