Bacterial filters in anesthesia: results of 9 years of surveillance

Anesthesia in patients with infectious disease caused by multi-drug resistant bacteria

PURPOSE OF REVIEW

Up to 50% of specific bacterial strains in healthcare admission facilities are multi-drug resistant organisms (MDROs). Involvement of anesthesiologists in management of patients carrying/at risk of carrying MDROs may decrease transmission in the Operating Room (OR).

RECENT FINDINGS

Anesthesiologists, their work area and tools have all been implicated in MDRO outbreaks. Causes include contamination of external ventilation circuits and noncontribution of filters to prevention, inappropriate decontamination procedures for nondisposable equipment (e.g. laryngoscopes, bronchoscopes and stethoscopes) and the anesthesia workplace (e.g. external surfaces of cart and anesthesia machine, telephones and computer keyboards) during OR cleaning and lack of training in sterile drug management.

SUMMARY

Discussions regarding the management of potential MDRO carriers must include anesthesia providers to optimize infection control interventions as well as the anesthesia method, the location of surgery and recovery and the details of patient transport. Anesthesia staff must learn to identify patients at risk for MDRO infection. Antibiotic prophylaxis, although not evidence based, should adhere to known best practices. Adjuvant therapies (e.g. intranasal Mupirocin and bathing with antiseptics) should be considered. Addition of nonmanual OR cleaning methods such as ultraviolet irradiation or gaseous decontamination is encouraged. Anesthesiologists must undergo formal training in sterile drug preparation and administration.

Heat and moisture exchangers and breathing system filters: their use in anaesthesia and intensive care. Part 1 - history, principles and efficiency

Heat and moisture exchangers and breathing system filters are intended to replace the normal warming, humidifying and filtering functions of the upper airways when these structures are bypassed during anaesthesia and intensive care. Guidance on their use continues to evolve. The aim of this part of the review is to describe the principles of their action and efficiency and to summarise the findings from clinical and laboratory studies. Based on previous studies, an appropriate minimum target for moisture output is 30 and 20 g.m⁻³ for long-duration use in intensive care and short-duration use in anaesthesia, respectively. The practice of reusing a breathing system in anaesthesia, provided it is protected by a filter, assumes that the filter is effective. However, there is wide variation in the gas-borne filtration performance, and contaminated condensate can potentially pass through some filters under typical pressures encountered during mechanical ventilation.

Filters in anaesthesia and intensive care

The use of various types of filters in anaesthesia and intensive care seems ubiquitous, yet authentication of the practice is scarce and controversies abound. This review examines evidence for the practice of using filters with blood and blood product transfusion (standard blood filter, microfilter, leucocyte depletion filter), infusion of fluids, breathing systems, epidural catheters, and at less common sites such as with Entonox inhalation in non-intubated patients, forced air convection warmers, and air-conditioning systems. For most filters, the literature failed to support routine usage, despite this seemingly being popular and innocuous. The controversies, as well as guidelines if available, for each type of filter, are discussed. The review aims to rationalize the place of various filters in the anaesthesia and intensive care environment.

Impact of hospital-wide surveillance on hospital-acquired infections in an acute-care hospital in the Netherlands

The goal of surveillance is to identify hospital-acquired infections (HAI) and risk factors, to apply targeted interventions and to evaluate their effect in an ongoing system. Continuing active surveillance in a 270-bed acute-care hospital is being performed on clinical patients, excluding day-care. The period 1984-1997 is described here. Specific surveillance-based interventions included the introduction of antimicrobial prophylaxis in gynaecology patients with postoperative urinary tract catheters and inpatients scheduled for appendicectomy and hysterectomy. General measures included education, implementation of protocols, feedback of surgeon-specific infection rates. In total, 3545 HAI were found in 13 years of surveillance. The incidence was 4.7/100 admissions and 4. 5/1000 patient days. Age-specific incidences ranged from 1.3 in the age-category 1-14 years, to 10.2 in patients aged 75 years and above. If age-specific incidences had remained at their 1984 level, over 3000 additional infections would have occurred, affecting all age groups except those up to 14 years. The distribution of types of infections differed between services. Following the targeted interventions, the rate of infections in gynaecology decreased from 19.4 per 1000 patient days in 1984 to 2.4 per 1000 patient days in 1996. The rates of wound infection following appendicectomy and hysterectomy decreased by 69% and 82%, respectively, in the period following the institution of antimicrobial prophylaxis. Over 4000 micro-organisms were isolated from the HAI; multi-resistant strains were isolated sporadically. We conclude that hospital-wide surveillance of hospital-acquired infections provides appropriate targets for interventions tailored to the specific needs of the hospital. The impact of such interventions can readily be documented from the surveillance data.

Association between implementation of CDC recommendations and ventilator-associated pneumonia at selected US hospitals

BACKGROUND

To assess whether selected recommendations in the Centers for Disease Control and Prevention "Guideline for Prevention of Nosocomial Pneumonia" were being implemented and having an impact on the occurrence of ventilator-associated pneumonia (VAP) at US hospitals, we surveyed hospitals participating in the National Nosocomial Infections Surveillance (NNIS) system.

METHODS

We mailed a questionnaire to the infection control practitioner of each NNIS hospital in 1995 and used data from the NNIS system to calculate annual rates of VAP.

RESULTS

Of the 188 hospitals surveyed, 179 (95%) returned completed questionnaires. Of these, 175 (98%) had implemented the recommended change of mechanical-ventilator breathing circuits at 48-hour or greater intervals. Of 110 hospitals using the hygroscopic condenser-humidifiers or heat-moisture exchangers with ventilators, 102 (93%) changed the hygroscopic condenser-humidifiers or heat-moisture exchangers routinely, and of 98 hospitals using bubbling humidifiers, 96 (98%) used sterile water to fill these humidifiers. Other practices for which the guideline provides no recommendation and their frequency of use by NNIS hospitals include use of hygroscopic condenser-humidifiers or heat-moisture exchangers (110/179 [61%]) and use of bacterial filters in anesthesia machines (128/171 [61%]). There was a significant decrease in the VAP rate from 1987 to 1998.

CONCLUSION

Most NNIS hospitals had implemented selected recommendations in the Centers for Disease Control and Prevention "Guideline for Prevention of Nosocomial Pneumonia" before the final publication of the revised guideline. Further studies are needed to assess the impact of these recommendations on the occurrence of VAP.