April, 1997


HIV Postexposure Prophylaxis

Margaret Ragni, M.D., Director, Hemophilia Center of Western Pennsylvania


Introduction:

With the availability of new antiretroviral drugs for treatment of HIV infection and better tools including HIV RNA PCR to quantitate infection, new recommendations have recently been introduced for occupational HIV exposure. The risk of occupational HIV transmission, reported by the CDC in 160 health care workers through 1996, is estimated to be quite small, 0.4% after needle stick exposure and 0.1% after mucocutaneous exposure. The purpose of this update is to review the approach to the evaluation, work-up, and treatment of a health care worker in whom high-risk HIV exposure has occurred or is strongly suspected.

 

Occupational Exposure:

Factors associated with occupational HIV transmission and seroconversion after needle stick include the depth of penetration, gauge of the needle, amount of blood injected, and viral load of the source patient. The greater the depth, the larger gauge needle, the larger the amount of blood injected, and the higher the viral load in the source patient, the greater the likelihood that HIV transmission may occur via occupational exposure. For mucocutaneous exposures, the greater the amount of virus splashed, the longer the time of exposure, and the more invasive the mode of entry, the greater the likelihood of seroconversion following exposure. The type of body fluid involved plays an important role in the risk of HIV transmission, based on the degree of cellularity of the fluid: fluids with of high cellularity, e.g. blood, semen, feces, sputum, pleural fluid, peritoneal fluid, amniotic fluid, and cerebrospinal fluid carry greater risk than those of low cellularity, e.g. urine, sweat, saliva, and tears.

Immediate Clinical Issues:

Within minutes of exposure to suspected or known HIV-infected blood, the health care worker should clean the exposed area with soap and water, or if the exposure occurred in mucous membranes, the eyes, nose, mouth, or site involved should be irrigated with cold water. The health care worker should then contact a physician, preferably an emergency room physician, and be seen immediately. The exposure should be briefly described, noting the site, source of, and time of exposure. Information should be obtained about the individual’s medications, allergies, pregnancy or breast-feeding status if a woman, hepatitis B vaccine status, and any risk factors for HIV infection. Information regarding the source patient (the one whose blood the health care worker has been exposed) should be obtained, including the source’s HIV status, and, if infected, the HIV RNA PCR (viral load), CD4, stage of disease, and antiretroviral treatment, as well as hepatitis B status. A decision should be reached regarding whether treatment is indicated, and if so, initiated within two hours of the exposure (see below). A physical examination and laboratory tests should be performed, including blood counts with differential, platelets; chemscreen, amylase; HIV antibody test, HBsAg, antiHBs (quantitative), antiHBc, antiHCV antibodies; CD4 number; and pregnancy test (for women of child-bearing age).

 

Treatment Recommendations:

Antiretroviral prophylaxis should be offered to all individuals sustaining a parenteral HIV exposure or a possible parenteral exposure, especially if the source has AIDS or a high viral load. The term parenteral refers to any exposure which pierces mucous membranes or the skin via needle stick, human bite, cut, or abrasion. The CDC recommends antiretroviral prophylaxis for all percutaneous, mucous membrane, or skin exposures where skin integrity is compromised, except those involving a source fluid not known to transmit HIV, e.g. urine, sweat, saliva, or tears. With recent evidence that combination antiretroviral therapy is more effective than monotherapy in reducing HIV viral load and preventing viral resistance, the new CDC guidelines for postexposure prophylaxis recommend the use of combination nucleoside reverse transcriptase inhibitors with or without a protease inhibitor. Specifically, combination therapy should include zidovudine (ZDV), 200 mg po q 8h, plus lamivudine (3TC), 150 mg po bid, with or without indinavir (IDV), 800 mg po q 8h, should be initiated within minutes and preferably within two hours of exposure and continued for four weeks. Indinavir must be taken one hour before or two hours after meals, and requires 1.5-2 liters of fluid intake per day to prevent kidney stones. The cost of a four-week course of ZDV plus 3TC plus IDV is $861.95 (average wholesale price, Red Book, 1997). Alternative regimens may include ZDV plus 3TC plus ritonavir (RTV) and/or saquinavir (SQV) or a-interferon (IFN).

 

Patient Treatment Decisions:

In contrast to patients who have known for years of their HIV infection, have an ongoing relationship with a physician who is familiar with AIDS treatment, and who have the luxury of time to make an informed decision regarding antiretroviral treatment, health care workers who experience an occupational HIV exposure will have to make quick decisions. This will include acknowledging that an exposure has occurred, administering immediate local measures, and informing a physician about the exposure and other highly personal information. Because this is a stressful experience, delays in seeking treatment may occur, and these may affect the outcome. Some individuals may require counseling and additional support.

 

Follow-up Visits and Testing:

The patient should be seen in follow-up for medical examination and testing for drug toxicity, including CBC and chemscreen, with amylase, at weeks 2 and 4 or more often, if medically indicated. A repeat CD4 count, HIV antibody testing, and HIV RNA PCR viral load should be performed at 6 weeks postexposure. Repeat HIV antibody testing should be performed at 6 weeks, 3, 6, and 12 months. Although testing at 12 months is not currently recommended by the CDC, ITxM does recommend it, supported by the recently report by Ridzon et al in which a health care worker exposed to HIV did not seroconvert until 12 months following exposure. It is recommended that individuals exposed to known or suspected HIV-infected individuals should refrain from blood or organ donation, abstain from sexual contact, or use condoms and a nonoxynol-containing spermicide, postpone pregnancy, and avoid breast-feeding. The teratogenicity of combination antiretroviral therapy and/or protease inhibitors is not known and should be discussed with the exposed individual. Finally, as new recommendations regarding treatment of HIV infection become available, these Postexposure Guidelines should be revised accordingly.

 

References:

1. Geberding JL. Prophylaxis for occupational exposure to HIV. Ann Intern Med 1996; 125: 497-501.

2. CDC. Update: Provisional public health service recommendations for chemoprophylaxis after occupational exposure to HIV. MMWR 1996; 45: 468-72.

3. Ridzon R et al. Simultaneous transmission of human immunodeficiency virus and hepatitis C virus from a needle-stick injury. N Engl J Med 1997; 336: 919-22.

 

Copies of the Transfusion Medicine Update can be obtained by contacting
Deborah Small, (412) 209-7320.