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Precautions Against Hepatitis and HIV Agents
A "universal" approach should be adopted for the prevention of infections by blood and body fluid-borne organisms such as HBV and HIV. To-date, there have only been two cases of laboratory-acquired HIV infection; one attributable to needlestick injury and the other to exposure to a virus culture supernatant fluid. Numerous cases of laboratory-acquired HBV infection had been recorded through contact with infected blood or body fluids. The primary mode of infection is contact between the hands and the infected material where the virus enters through cuts and abrasions. There is no evidence that the inhalation of aerosols of blood or other body fluids plays any part in laboratory-acquired HBV infections but this could certainly not be excluded as a possibility.
Where standard precautions are used, there should be a set of standard operating procedures and only skilled staff should be employed. They should have received HBV vaccine. The WHO, but not some other authorities recommends medical surveillance and base-line serum samples.
1. Precautions against contact - protective clothing should be worn at all times and may be supplemented by plastic aprons. Good quality disposable gloves should be worn. Cuts, scratches and abrasions on the hands should be covered. Masks, visors, or goggles should be worn if there is a possibility that the face may be splashed with blood or other material. Methods for the collection and transport of specimens should be reviewed to reduce as far as possible the number of operations that expose the operator and the possibility of leaking containers. Blood may be splashed when containers are opened, and suitable precautions should be taken e.g. gripping the stopper or cap through a strip of paper wrapped around it confines dispersal. Blood specimens should be centrifuged in sealed centrifuge buckets. If serum is separated by pouring, the rim of the tube should be wiped with filter paper soaked in hypochlorite or glutaraldehyde. Care should be taken in making and handling blood films. Sampling probes of automated apparatus should be wiped with tissues held in gloved hands.
2. Precautions against injection - accidental inoculation with hypodermic needles, other sharp instruments and broken glass may be reduced by replacing such hazardous equipment with inherently safer articles. Needles may be replaced by cannulas, glass pasteur pipettes by the plastic disposable type, and other glassware by rigid plastic or break-resistant glass. All re-usable glassware should be examined before it leaves the preparation room for chips and rough edges. Used sharp objects and broken glass should be discarded into rigid containers. Special precautions should be taken against needlestick accidents. Care is also essential when approaching the sharp sampling probes of some automated instruments.
3. Action in case of accidental exposure - Instructions for action should be part of the SOPs. If the skin is accidentally punctured or that skin lesions are contaminated, immediate action is necessary. Bleeding should be encouraged under running water, a dressing applied and the accident reported and appropriate follow-up action taken. The affected part should be washed immediately with soap and water. Mucous membranes and conjunctivae should be thoroughly irrigated with water.
4. Automated equipment - automated equipment should be of the "closed system" type that is capable of being decontaminated by passing disinfectant through it. The probes should be shielded to avoid splashing. Effluent should be collected in closed bottles or discharged at least 25 cm into the waste plumbing system.
5. Inactivation of specimen - some attention has been given to the possibility of inactivating the viruses in blood and other specimens so that they are safer to work with. The most commonly used method is heating the specimen to 56oC for 30 minutes which is sufficient to inactivate HIV to undetectable levels . However, this is unlikely to have any effect on hepatitis B, which is thought to require temperatures of up to 80-90oC for inactivation. Other methods such as treatment with ethanol or with B -propiolactone has been advocated but doubts had been cast on the effectiveness of all three methods. Buffered Forman may be useful for decontaminating blood films. In the case of histopathology specimens, small specimens such as needle biopsies will be fixed and decontaminated quickly, whereas larger pieces of tissue may require several days. If frozen section work is unavoidable, the cryostat should be well shielded and the operator should wear face and eye protection. After use, the machine should be brought to room temperature and disinfected.
6. Spillage, decontamination and disposal of waste - if blood or other infected material is spilled, the spillage should be immediately mopped up with gloved hands, and disinfected using either glutaraldehyde or hypochlorite (10000 ppm). HIV is effectively inactivated by alcohol mixtures, hydrogen peroxide, hypochlorites and paraformaldehyde at the strengths usually employed in laboratories. Contaminated protective clothing should be autoclaved or bagged for hot wash laundering. Gloves should be discarded into contaminated waste receptacles for autoclaving or incineration. If street clothing is contaminated, it should be sponged with hot detergent solution, possibly with glutaraldehyde depending on the nature of the material.
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Infection Hazards of Human Cadavers