Until an effective HIV vaccine is in widespread use, taming the HIV epidemic will require the prevention of exposure to the virus. Activities such as on-site rapid HIV testing with early treatment of infected persons, universal precaution training, safer sex education, and needle exchange programs all are important aspects of an effective preventative strategy. However, in cases where exposure has already occurred, it is possible to decrease the risk of transmission of HIV infection through the use of postexposure prophylaxis (PEP).
The best-documented success of HIV PEP has been through the prevention of maternal to child transmission. In the National Institutes of Health, U.S. Department of Health and Human Services funded Pediatric AIDS Clinical Trials Group 076 trial, a three-arm intervention with zidovudine (prenatal, intrapartum, and postpartum) decreased the risk of neonatal HIV infection from 21% to 8%.1 Subsequent studies indicated that a significant part of the decrease in the transmission risk was based on the receipt of postnatal medication. In situations where mothers did not receive any prenatal antiretroviral therapy, the provision of antiretroviral medication to the HIV-exposed newborns within 48 hours of life decreased the risk of transmission by up to 50%.2
HIV-related PEP is now used routinely in hospitals following occupational exposure and in emergency departments following accidental or unprotected exposure to body fluids—termed nonoccupational exposure. It is important for all health care providers to be aware of current PEP recommendations, and to know how to rapidly access such information and/or consultation. This chapter will discuss HIV PEP as it relates to occupational and nonoccupational exposure to HIV.
Through June 2000, the Centers for Disease Control of the U.S. Department of Health and Human Services reported 56 cases of HIV infection in health care workers (HCWs) documented to follow occupational exposure, with an additional 138 possible cases.3 The risk of occupational exposure to potentially infectious body fluid is highest among surgical staff, followed by nonsurgical nurses (especially those in the Emergency Department), phlebotomists, and resident physicians. General surgeons report an average of 4 intraoperative percutaneous injuries per year.4 Among pediatric residents, 13–70% report at least one needle stick exposure per year.5,6
The risk of transmission of HIV from a single percutaneous injury from a contaminated needle is approximately 1 in 300 (0.3%) (Table 55–1).7 An increased risk of transmission has been associated with exposures to patients with late stage HIV infection/AIDS, hollow bore needles, a deep puncture wound, and blood observed in the involved needle.8,9 The risk of transmission of HIV from nonpercutaneous exposures is much less. For exposure to bloody fluid across mucus membranes, the risk is estimated to be less than 1/1000 (0.1%), and even less when the exposure is across intact skin.
Table 55–1. Estimated Risk of Transmission of HIV Based on Exposure