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HIV exposure in health care

H ealth care workers have always suffered occupational risks from illnesses such as tuberculosis, leprosy and hepatitis B. To these have now been added the bloodborne infections HIV and hepatitis C, with the risk of transmission during medical procedures from patient to health care worker, from health care worker to patient, or from patient to patient. Epidemiological studies suggest that the risk of HIV transmission from an infected patient to a health care worker by a significant needlestick injury is about 0.3 %.1 In spite of several studies of HIV-infected health care workers, the Florida dentistremains the only documented instance of transmission of HIV from health care worker to patient in countries where sophisticated infection control guidelines are in place. Since 1983, guidelines encompassing universal precautions have offered the greatest protection for health care workers and patients alike. In the many invasiveprocedures performed by HIV-infected health care workers and the vastly greater number of procedures involving HIV-infected patients, there has been no convincing evidence of transmission without an accident or breach of infection control guidelines. How do the guidelines work? Basically, these demand that health care workers treat all blood and bodily fluids as if these are infectious, and rely on principles of hand washing, use of protective clothing, appropriate disinfection/sterilisation, sharps handling and waste management. These guidelines are coupled with policies (as recommended by various government and professional bodies) on HIVinfected health care workers which preclude their participation in exposure-prone procedures. Against this background, the recent Sydney experience (in which four patients were infected with HIV in a doctor's surgery on a single day") raises serious public health questions. These patients underwent minor skin surgery after another patient who was HIV infected. Despite considerable investigation, no identifiable breach of infection control guidelines was found. Yet, knowing that infection control does work, that HIV does not survive sterilisation and that barrier procedures prevent HIV transmission, the inescapable conclusion is that some breach must have occurred. In this case, attention was focused on the potential for contamination of multidose vials of local anaesthetic, of the kind widely used in dentistry and in minor procedures. In this issue (page 513), Druce et al. present laboratory evidence confirming the theoretical possibility of this route of transmission." First, they show that, after an injection, decompression of the syringe barrel leads to back-filling of the needle and syringe with as much as 25 ul, of fluid, which could be transferred to a multidose vial of anaesthetic. Then they show that HIV, either cell-free or within lymphocytes, can remain viable up to four hours in an anaesthetic solution, depending on the local anaesthetic used and the concentration of HIV in the inoculum. This is certainly sufficient time for single or serial passage of HIV through this medium if improperly handled. Notwithstanding this demonstration in vitro, events in vivo after HIV inoculation are certainly different because of. known natural defence mechanisms." Not all subjects inoculated via needlestick will become HIV infected. We also know that HIV is rapidly inactivated in discarded needles and syringes improperly disposed ofby injecting drug users. Adherence to infection control guidelines and the policies of voluntary compliance by health care workers with HIV testing, and subsequent exclusion of HIV-infected workers from exposure-prone procedures, offer the best protection of both public and health care workers alike. The recently released NSW Infection Control Policy and regulations," combined with the revised HIV Infected Health Care Worker Policy," should serve as a benchmark for protection against transmission of blood-borne viruses in the health care setting. Implementing these policies is essential and their monitoring should be a professional responsibility. The overwhelming majority of health care workers knowing their responsibilities will comply with the voluntary code. Continual vigilance and review of guidelines and policies are essential. The latest item to come under review is the use of multidose vials, which will increasingly be replaced by single-dose units. However, if this is not possible (as, for example, with some vaccinations) health care workers must be ultracautious, recognising that infectious fluids can be transferred by needles and syringes and that HIV can remain active in anaesthetic solutions. Ultimately, all needles and syringes should be used once only, and never transferred from patient to multidose vial. Ronald Penny