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Am Fam Physician. 2000;61(10):3171-3174

Control of Nitrous Oxide During Cryosurgery

The National Institute for Occupational Safety and Health (NIOSH) of the Centers for Disease Control and Prevention has published a hazard controls document (HC 29) on the control of nitrous oxide gas during cryosurgery. Studies have shown that airborne concentrations of nitrous oxide from cryosurgical units can be effectively controlled by ventilation and maintenance of the equipment. If this is not possible, substitution with a less hazardous cryogenic gas may also be appropriate.

Compressed gases such as nitrous oxide are often used to reach the cold temperatures needed for cryosurgery. Instruments used in cryosurgery are designed to allow the gas to expand through a valve inside the metal tip of the cyrosurgical probe, causing the tip to reach extremely low temperatures. According to NIOSH, if the exhaust gas from the instruments is not vented properly, gas concentrations in the air can reach several thousand parts per million during a procedure. Depending on the rate of ventilation in the room, levels of this gas can remain elevated for long periods of time. To prevent short-term behavioral and long-term reproductive health effects that can be caused by nitrous oxide, exposure to the gas should be minimized.

Most newer cryosurgical units are equipped with a scavenging port from which the gas is exhausted. The NIOSH document outlines several safe methods of ventilation. These include routing the exhaust directly to the outdoors, discharging the exhaust into a nonrecirculating general ventilation system and sending the exhaust to a vacuum scavenging system. The document also discusses routine maintenance of the equipment and recommends the substitution of carbon dioxide when scavenging is not possible. NIOSH states that carbon dioxide is less hazardous and has a much higher airborne exposure limit than nitrous oxide. The manufacturer of the cryosurgical unit should be consulted for guidance with the use of carbon dioxide.

For more information about controlling this hazard or for information about other occupational safety and health issues, call NIOSH at 800-35-NIOSH (800-356-4674) or visit the NIOSH Web site at

ACOG Bulletin on Domestic Violence

While domestic violence affects persons in all age, racial and socioeconomic groups, women make up the majority of victims. Because the problem is so widespread, the Committee on Underserved Women of the American College of Obstetricians and Gynecologists (ACOG) has developed an educational bulletin on domestic violence. ACOG Educational Bulletin no. 257 appears in the December 1999 issue of Obstetrics and Gynecology.

The term “domestic violence” commonly refers to violence perpetrated against adolescent and adult females within the context of family or intimate relationships. According to the committee, the true extent of domestic violence is difficult to ascertain. The U.S. Department of Justice estimates that violence by an intimate partner accounts for nearly 21 percent of all violent crimes experienced by women; 30 percent of female murder victims are killed by an intimate partner.

Identification of abuse victims may be difficult, states the committee. Physicians may not realize the widespread prevalence of the problem. Other barriers to identification include time constraints, fear of offending the patient and a feeling of powerlessness in the area of treatment. Asking patients a few behavioral-specific questions in private should help to identify most abused women.

Once the victim has disclosed the domestic abuse, the physician should acknowledge the trauma, provide education and support, and offer referrals to community support services. ACOG recommends assessing the victim's immediate safety and helping her to establish a safety plan. Information on how to establish a safety plan can be given to the patient or left in an area where the victim can pick it up privately.

The committee stresses the importance of accurate documentation after screening for domestic violence. Direct quotations of the patient's explanation of her injuries and photographs may help if the patient takes legal action against the perpetrator.

The ACOG bulletin also discusses special populations that may be affected by domestic violence, such as children of abuse victims, elderly persons and pregnant women, and legal issues that are involved in the reporting of suspected abuse.

OSHA Directives on the Use of Safety Needles

The Occupational Health and Safety Administration (OSHA) recently issued new compliance directives that will enforce the use of available, approved and effective safety engineered needles in almost every health care facility in the United States. The issuance and enforcement of the new directives, “Enforcement Procedures for the Occupational Exposure to Bloodborne Pathogens,” are expected to cause a complete, rapid conversion in the medical sharps market from conventional to safety engineered devices.

According to the directives, every employer must record and report all incidents of accidental needle sticks, and also establish an exposure control plan that documents the evaluation and implementation of appropriate engineering controls that are designed to eliminate or minimize exposure to bloodborne pathogens. Employers must also implement and use these controls to eliminate occupational exposure or reduce it to the lowest possible extent.

The exposure control plan should identify and document all job classifications in which employees have occupational exposure. OSHA requires that the plan be reviewed and updated at least every 12 months and whenever necessary to reflect new or modified tasks and procedures that affect occupational exposure and to reflect new or revised employee positions with occupational exposure.

To enforce OSHA's Occupational Exposure to the Bloodborne Pathogens Standard, the directives establish policy and provide clarification to ensure that uniform inspection procedures are followed. Failure to create an exposure control plan or to implement the compliance directives would be classified as a serious violation, in which case the employer could be cited and fined for failure to comply.

For more information on the compliance directives, write to OSHA at the U.S. Department of Labor, Office of Public Affairs, Room N3647, 200 Constitution Ave., Washington, D.C. 20210; call 202-693-1999; or visit the OSHA Web site at

Report on the Health Care of U.S. Children

Infections and birth-related problems cause the majority of hospitalizations in infants and preschool-aged children, while asthma, injuries and mental health problems lead to more hospitalizations of children older than five years than any other conditions, according to the new “Annual Report on Access to and Utilization of Health Care for Children and Youth in the United States—1999.” The report was compiled by the Agency for Healthcare Research and Quality (AHRQ), formerly the Agency for Health Care Policy and Researc.

The report found that adolescents between 15 and 17 years of age are hospitalized mainly for problems related to pregnancy and child-bearing. Uninsured persons in this age group are the most likely to not have a usual source of health care and the least likely to use office-based health care professionals, such as family physicians and pediatricians. The report also provides data on health insurance coverage and use of ambulatory care services.

This report is the first in a new series of annual reports by the AHRQ on access to and use of health care by children and adolescents in the United States. The statistics in the report are taken from the AHRQ's Medical Expenditure Panel Survey and the Healthcare Cost and Utilization Project Nationwide Inpatient Sample databases.

Copies of the report (AHRQ 00-R014) may be obtained free of charge by writing the AHRQ Publications Clearinghouse, P.O. Box 8547, Silver Spring, MD 20907. The report may also be obtained by calling 800-358-9295 or from AHRQ InstantFAX: 301-594-2800.

Autologous Chondrocyte Implantation for Knee Damage

The Health Technology Advisory Committee (HTAC) has published an issue brief on autologous chondrocyte implantation for the treatment of chondral knee damage. HTAC was established in 1992 by the Minnesota state legislature. It is an independent, nonpartisan advisory body that evaluates new and emerging health care technologies based on existing scientific research and technology assessments.

Damage to the hyaline cartilage of the knee can cause pain, swelling and disabling joint dysfunction. Options for the management of cartilage defects currently include debridement or abrasion arthroplasty, subchondral drilling and microfracture. These treatments are not always effective and, when they are, the benefits may not last. If the damage is not repaired, it can lead to progressive degenerative changes and, eventually, total knee replacement. Autologous chondrocyte transplantation is now being evaluated as a better way to treat knee cartilage defects.

In autologous chondrocyte transplantation, the patient's own cartilage cells are used to repair the damage to the articular cartilage. The procedure involves collecting and producing an ex vivo culture of articular cartilage cells, which are implanted into the defect to regenerate and repair the articular surface. In the United States, only one company produces ex vivo cell chondrocyte culture.

Although autologous chondrocyte transplantation appears to be a promising alternative to standard approaches for managing cartilage defects of the knee, the effectiveness of the procedure has not been established and the long-term outcome is unknown. According to HTAC, well-designed, randomized, controlled trials are needed to prove the efficacy of this method, define patient selection criteria and determine long-term benefits, compared with alternative management strategies. Currently, autologous chondrocyte transplantation is a reasonable treatment alternative only for carefully selected patients.

This report and others published by HTAC may be obtained by calling 651-282-6974; There is no charge for the reports. All HTAC reports are also available through the Web at

Patterning in Children with Neurologic Impairment

The Committee on Children with Disabilities of the American Academy of Pediatrics (AAP) has published a statement on the use of patterning in the treatment of children with neurologic impairment. The AAP committee states that patterning is based on an outmoded and oversimplified theory of brain development. According to the statement, current medical information does not support the efficacy of patterning, and the use of this treatment continues to be unwarranted. The AAP statement appears in the November 1999 issue of Pediatrics.

For more than 40 years, patterning has been advocated in the treatment of children with brain damage, learning disabilities, Down syndrome, cerebral palsy and autism. Many organizations, including the AAP, have issued cautionary statements about the usefulness of this treatment. In response to media coverage, inquiries from parents and public officials, the use of alternative forms of treatment in such children and the existence of a new generation of physicians who may be unaware of the programs that involve the use of patterning, the AAP has reviewed the current status of this controversial treatment.

Patterning involves a series of exercises that are intended to improve the “neurologic organization” of a child with neurologic impairments. These exercises must be performed over many hours during the day by several persons. These persons must manipulate the child's head and extremities in patterns that are thought to simulate the prenatal and postnatal movements of children who are not impaired.

The published results of patterning therapy have been inconclusive. Some children with brain disabilities who were reported to have benefited from treatment had been given a misdiagnosis or an overly pessimistic prognosis.

According to the AAP committee, physicians should work closely with the parents of children with neurologic disabilities to ensure that they have access to all standard services available in their communities. After the diagnosis is made, controversial treatments should be discussed as part of the child's initial management plan.

Based on past and current studies, the AAP committee concludes that patterning is not an effective treatment, the claims of its advocates are unproven, and the demands and expectations placed on the families of these children are so great that their financial resources may be depleted substantially and family relationships could be harmed.

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