The value of protective isolation in preventing nosocomial infections in high risk patients

Since infection is a major cause of death in the patient whose immune responses have been compromised (immunocompromised patient), considerable attention has been focused on developing methods for the prevention of infection. This has primarily been directed at suppressing or eliminating the host's endogenous microbial burden and in decreasing the acquisition of new organisms. The prevention techniques which have been employed vary in complexity from single-room isolation to elaborate systems utilizing air-filtration and decontamination. The most sophisticated of these regimens is the total protected environment (TPE) consisting of a high-efficiency-particulate-air (HEPA)-filtered laminar air flow room which is surface disinfected and in which the patient is fully decontaminated with oral nonabsorbable antibiotics, cutaneous antisepsis, orificial antibiotics and a semisterile diet. The cumulative data to data have shown that the TPE affords a significant (albeit incomplete) reduction in the incidence of serious infections in severely compromised patients. Such protection from infection permits the delivery of novel therapies which might have been precluded because of consequent hematologic or immunologic toxicity. Nonetheless, the TPE is also elaborate, cumbersome and expensive, and its utilization for patients with immunodeficiency syndromes, bone marrow failure states and cancer depends heavily on the success of available therapy (e.g., immunoreconstitution, transplantation, intensive chemotherapy) for the patient's underlying disorder. Critical evaluation of the TPE and alternative prevention strategies are imperative to assure the effective and appropriate utilization of limited hospital resources.

Prevention of infection on the oncology unit

Various combinations of immune deficiency, tumor effect, surgery, ionizing radiation, chemotherapy, and neutropenia result in infection-prone states for hospitalized cancer patients. Recognition of nosocomial infection may be difficult, and fever may be the only finding. Pathogens may be exogenously acquired from the contaminated hospital environment. Transmission by contact with hospital personnel is the usual mode of exogenous acquisition of hospital bacteria, and handwashing is the most effective means of prevention. The utility of conventional protective isolation in prevention of exogenous transmission is in question. Inattention to infection control measures by nurses and physicians may result in higher infection rates and more serious types of infections. Endogenous infection by the patient's own bacteria and fungi also occurs in the cancer ward. Autoinfection is "amplified" by the use of cannulae, catheters, and other hospital devices. Meticulous nursing care, particularly in neutropenic persons, is important in reducing the incidence of endogenous spread of microbes. Exogenous and endogenous infections in neutropenic patients are reduced using laminar air flow rooms combined with prophylactic antibiotics. It is still not clear if these expensive measures are effective in prolonging survival of patients with acute leukemia.

Simple and microbiologically safe portable transport unit for patients requiring protected isolation

The removal of a patient from a laminar air flow room during protected isolation poses the risk of his microbial contamination and infection. Nonetheless, temporary removal from the laminar air flow room may be necessary for certain medical procedures or for psychological relief during prolonged periods of isolation or both. A means for protecting patients during temporary removal from the laminar air flow room is highly desirable. A previously described total body garment has been shown to be microbiologically safe and effective, but is expensive, cumbersome, and not very adaptable to patients of different ages and body sizes. We now present an alternative, microbiologically safe transportation system which delivers, high-efficiency particulate air-filtered air over the head and neck through a modified, lightweight, commercially available helmet and power supply and which can be comfortably and reliably used by isolated patients.

Containment aircraft transit isolator

The Containment Aircraft Transit Isolator is a self-contained unit capable of transporting a patient with a highly virulent disease and at the same time providing maximum microbiological security while full nursing care and treatment are carried out. The isolator was employed in a trans-Atlantic simulated aeromedical evacuation in a Canadian Forces Boeing 707. During the exercise, flight testing was undertaken and nursing care, treatment, and decontamination procedures were developed and evaluated. Flight medical personnel were trained in the use of the unit. It was concluded that flight-trained medical teams, well versed in general aviation medicine and with a detailed familiarity with the isolator, are necessary for safely transporting patients with exotic diseases.

Attempts to control clothes-borne infection in a burn unit, 3. An open-roofed plastic isolator or plastic aprons to prevent contact transfer of bacteria

An open-roofed plastic isolator was built in a single patient isolation room in a burn unit. It was designed to prevent contact contamination only, as this had been shown to be the important route of cross-colonization in the unit. To exclude any possible effect on airborne transfer of bacteria, the isolator was first examined by means of an airborne particle tracer of the same size as bacteria-carrying particles. Such experiments indicated that the isolator might prevent some transfer out of but not into the isolator. This was not confirmed in simulated nursing experiments nor in a patient study, where the air counts of bacteria were practically the same inside and outside the isolator wall. Two patients only were nursed in the isolator. Both patients acquired exogenous colonizations from other patients, one with Ps. aeruginosa and the other with S. aureus. Nursing in the isolator was difficult and staff-demanding. In simulated nursing experiments, plastic aprons and gauntlets as the only protective measures against contact contamination gave as much protection to a mock patient as did the isolator. S. aureus were released from nurses' clothes more easily during work with the isolator than in open nursing with aprons and gauntlets. In conclusion, the isolator did not seem to be a realistic alternative to impermeable clothes such as plastic aprons as a means of preventing clothes-borne cross-contamination between burn patients.

[Use of plastic isolators in the prevention of infection in high risk patients with hematologic diseases]

The authors report a microbiological study of the flora of high risk adults with blood diseases isolated in hermetically sealed plastic isolater. This type of isolation is very effective in the prevention of infections due to hospital germs as such contamination occurred only twice in 292 days isolation and was found in only 0.8% on samples. The efficacy of methods of body decontamination and the incidence of infective complications in our series is also reported.

Negative-pressure plastic isolator for patients with dangerous infections

A negative-pressure plastic isolator is effective for dealing with patients suffering from dangerous infections. So far it has been used to treat seven patients suspected of having infections due to Lassa, Marburg, or Ebola viruses. One patient spent 32 days in the isolator. The isolator was proved comfortable and acceptable to patients, and it gives the nursing and medical attendants a high degree of protection. All routine nursing and medical procedures can be carried out with minimal interference by the physical barrier, though it is not practicable to undertake artificial respiration or haemodialysis.

Evaluation of Vickers-Trexler isolator in children undergoing bone marrow transplantation

Four children, 5 months to 15 years of age, underwent bone marrow transplantation in Vickers-Trexler isolator tents. Two grafts were elective. During 170 days of isolation no clinical infections due to exogenous micro-organisms developed despite severe immunodeficiency. The decontamination regimen and sterile procedures used, as well as the microbiological results, are described. This form of isolation in paediatric practice was found to be highly acceptable to both patients and staff.

Isolation for high-risk patients

Standard isolation accommodation provides adequate protection against the infectious diseases prevalent in the U.K. but higher standards are necessary for more dangerous infections imported from overseas. These may be provided reasonably cheaply by modifying existing wards but staff are still exposed to risk. By physically separating the patient from the attendants, the Trexler plastic isolator affords a greater degree of protection and is of particular value when dealing with a dangerous infection against which there is no form of immunization.

The development of isolators

A series has been developed of closed-system isolators which provide patients with the same effective control of microbial infection as is possible in the laboratory animal. These isolators are used to protect susceptible patients from exogenous infection as well as to prevent the spread of dangerous pathogens from infected patients. The six models of isolators are designed for use in operating theatres, or on the wards and to transport patients.

A source isolator for infected patients

A plastic, mechanically ventilated source isolator with filters in the air effluent was designed to enable infected patients to be nursed and treated in a general ward or to be transported without risk to staff or other contacts. Two models of isolator were developed. Their potential value was tested by the challenge of heavy dispersal, inside the isolator, of bacteria (a) from patients with burns, during the change of dressings, (b) from contaminated bedding during simulated bed-making, and (c) from the dispersal of a suspension of Bacillus subtilis var. globigii. Sampling of air by slit samplers outside the isolator and, in comparable control patients, from the air of the room in which dressings were changed, showed consistently lower counts of bacteria and of Staph. aureus during dressings when the isolator was used; on removal of the isolator canopy there was, in some experiments, a considerable increase in airborne bacteria, due to residual bacteria in the isolator of to the re-dispersal of bacteria which settled on the patient and his bedding during the dressing. Simultaneous sampling with slit samplers inside and outside the isolator during and after bed-making or dispersal of B. subtilis var. globigii showed an almost complete protection of the air outside the isolator against contamination by bacteria released inside the isolator.

Plastic isolators for treatment of acute leukaemia patients under "germ-free" conditions

A gnotobiotic isolation system based on those developed in veterinary research has been constructed for hospital use. Fifteen patients with leukaemia and neutropenia spent a total of 110 weeks in plastic isolators, and none acquired any infection. Endogenous flora was effectively suppressed by topical antiseptics and gastrointestinal decontamination effected with nonabsorbable antibiotics. The isolator system was acceptable to patients and staff and much cheaper than the use of sterile rooms. Other advantages of the system are portability, easy storage, and use on ordinary open wards without prejudice to the microbiological protection afforded. It is as yet uncertain whether protective environments of this type will substantially improve the outcome of treatment for the acute leukaemias.

[Neurosurgery in strict asepsis. First trials in an operation isolator during the placement of 10 ventriculoperitoneal derivations]

Authors report on a series of ten ventricular-cardiac or peritoneal derivations performed under operative field isolation, air-tight and sterile enclosure that makes possible to perform surgery under strict aspsis. The first results compared with those mentioned in the medical literature, let foresee a fall in the occurence of post-operative infections. The technique is adaptable to neurosurgery and does not complicate the operative process.

Microbial isolators for use in the hospital

Isolators made of flexible transparant plastic film maintain a physical separation between clean and dirty areas without interfering with the use of the isolated space. The reliability with which isolators maintain sterility has been demonstrated by the germ-free rearing of the common laboratory and domestic animals. Isolators are used routinely in orthopaedic surgery and for protecting patients who have severe congenital immune deficiency disease or are made infection-prone because of therapy.