Innovative Approach to Moderating Risk of Nosocomial Infection During Anesthesia

INTRODUCTION

There are significant infection control concerns in both provider behavior and equipment domains present in the surgical anesthesia workstation (AW), placing patients and their providers at substantial risk.^1⇓⇓⇓-5 There is a clinically significant potential for microbial cross-contamination from 1 patient to subsequent patients scheduled in the same operating room (OR) because of lapses in hand hygiene, procedural task density, equipment design complexity, and difficulty in disinfecting the apparatus between patients (Figure 1).

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Figure 1.

Vectors of microbial contamination in the AW.

During the anesthetic treatment of the surgical patient, the AW represents a challenging environment where it is nearly impossible to consistently perform optimal asepsis when rendering care (Figure 2). Work from both our laboratory and clinical studies,^6⇓-8 as well as from others,^1⇓⇓-4,9 demonstrates quantifiable risks of microbial cross-contamination in the AW that must be addressed. Health care–associated infections (HAIs) are a significant national health concern carrying increased patient morbidity, mortality, and financial cost.^10,11

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Figure 2.

A typical anesthesia machine with architectural/design complexity, making cleaning and disinfection between surgical procedures very challenging.

Recent multidisciplinary expert guidance statements endorsed by the American Operating Room Nursing Association, the American Society of Anesthesiologists, the American Association of Nurse Anesthesiology, and the American Association of Anesthesia Assistants detail the grave risks of microbial iatrogenesis in the AW.⁵ Several of these recommendations relate to the need for ongoing patient safety research regarding between-procedure decontamination of the anesthesia delivery machine (ADM) as well as the potential role of disposable covers/wraps to prevent microbial contamination. This authoritative guidance noted a deficiency of, and need for, evidence-based research targeting these issues.

A clinical pragmatic trial was designed to assess a novel approach to mitigate the risk of cross-contamination in the AW. The following hypothesis was tested: Strategic barriers placed on the ADM during general anesthesia administration will decrease density and diversity of bacterial contamination over the course of sequential patients exposed to the same equipment compared with machines without the barriers.

MATERIALS AND METHODS

With institutional review board (IRB) approval from Virginia Commonwealth University Medical Center (VCUMC), 30 diverse surgical operations requiring general anesthesia care over a 3-day period were matched 1:1 as the control group (N = 15, no intervention, the uncovered condition) or the intervention group (N = 15, condom-like barriers to anesthesia machine hot spots [defined as AW elements frequently touched and difficult to disinfect, revealed in our previous work], the covered condition). These included the electronic medical record (EMR) computer control mouse, the breathing circuit pressure control (or adjustable pressure-limiting [APL]) valve, the oxygen flowmeter control, and the anesthetic agent vaporizer dials (Figure 3). This prospective, pragmatic trial involving a convenience sample of surgical patients was conducted in the main operating suites of VCUMC.

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Figure 3.

Location of condom-like protective covers: (A) vaporizer control dials, (B) oxygen flowmeter control, (C) electrical medical record control mouse, and (D) breathing circuit pressure control valve (APL valve).

A supply of elasticized condom-like covers was obtained in 3 sizes (small, medium, and large). In a prestudy test, it was established that these were nonpermeable to bacteria congruent with the full anesthesia machine wrap from the previous study.⁸

Preliminary Study: Assessing Wrap Integrity

A preliminary study was performed to test the ability of the plastic covers to prevent bacterial contamination of the ADM. A sterile condom-like cover was applied to the vaporizer dial of an ADM. The dial was scrubbed clean with ethanol prior to the application to ensure that prior contamination did not affect the results. ESwabs containing Amies media (COPAN Diagnostics Inc, Murrieta, CA) were then used to collect samples from the plastic cover (both sides) and the anesthesia machine prior to the inoculation with Staphylococcus epidermidis (ATCC 12228). The sterile plastic cover was applied over the cleaned anesthesia machine dial. Approximately 5 colonies of S epidermidis (ATCC 12228) were removed from a blood agar plate with a sterile swab and inoculated and spread onto the outside of the cleaned plastic cover. ESwabs were used to swab the outside of the plastic cover, inside of the plastic cover, and covered dial to determine if the plastic cover prevented the contamination of the ADM.

The collected swabs were taken back to the laboratory and vortexed for 2 minutes. Immediately following the vortexing, 100 µL of Amies media was removed from the ESwab tube and plated directly to a sheep blood agar (SBA) plate (Thermo Fisher Scientific, Waltham, MA). The inoculum was spread evenly over the plate using a cell spreader, and the plates were incubated for 48 hours at 35 °C to allow for bacterial growth. No bacterial growth was observed on the 3 plates prepared using samples collected prior to the addition bacteria, indicating that the ADM (area covered) and plastic cover were free of detectable bacterial contamination prior to the inoculation with S epidermidis. The only plate to demonstrate bacterial contamination from the samples collected after the addition of bacteria was the plate inoculated with the ESwab from the outside of the plastic cover. Plates prepared using samples from the inside of the cover and the knob were both free of detectable bacterial contamination, indicating that the covers prevent the contamination of the dial (Figure 4). The organism grown was then identified as S epidermidis using Gram staining, catalase testing, coagulase testing, pyrrolidonyl arylamidase (PYR) testing, and novobiocin susceptibility testing.

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Figure 4.

Preliminary study to assess wrap barrier effectiveness. Growth on SBA after 48-hour incubation (A) outside of plastic cover after inoculation with S epidermis, (B) inside of plastic cover after inoculation with S epidermis, and (C) knob covered after inoculation with S epidermis.

Conduct of the Primary Study

Ethical Considerations

With IRB assent, the study was conducted in a manner that did not deviate from the routine surgical and anesthetic treatment of the enrolled patients. Enrollment of patients in the intervention group was approved by both surgical and anesthesia team members as well as the director of OR services, all of whom were aware of the study goals and methodology. Confidentiality of patient information was assured as a given case became a randomly selected rubric, and no identifying patient information of any kind was recorded.

Culture samples were obtained from the 4 hot spots prior to the first surgical operation of the day, after the provider had completed their routine anesthesia machine checkout procedure to ensure full functionality. This was done for each of the 2 matched rooms for each of the 3 days of the study. Rooms selected on each day of the study were matched based on procedure similarity, with 1 room randomly chosen as the intervention room and the other as the control room. To prevent contamination in the intervention room, the study team used hand sanitizer and donned gloves prior to placing the covers.

Immediately following each operation, after both patient and provider exited the OR for transfer to the postanesthesia care area or intensive care unit, repeated cultures were obtained from each of the hot spots after careful removal of the covering (employing the same hand sanitizing/gloving protocol as before).

The researchers interfered with neither the environmental services staff who routinely cleaned the AW between operations, nor the anesthesia technician staff who prepared the AW for the next operation. The sequence was repeated in both the intervention OR and the control OR over the course of 3 consecutive days (Figure 5).

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Figure 5.

Chronology of culturing in the intervention and control room cases.

RESULTS

DISCUSSION

The Centers for Disease Control and Prevention published a white paper urging health care providers and institutional leadership to address the following short- and long-term goals: (1) preventing iatrogenic infection for those having surgical interventions, (2) preventing the spread of bacterial organisms, and (3) avoiding misuse of antibiotics.¹² With this mandate, as well as that of the recently published guidelines⁵ urging research directed specifically at the AW, the current pragmatic trial was taken on.

The perioperative milieu is a reservoir of bacterial (and, for that matter, viral and fungal) organisms that are pathogenic to humans. In recent work, it appears that 50% of surgical site infections are linked to bacterial pathogens that were in the OR where the patient’s procedure was performed.⁴ There is compelling and methodologically sound research that demonstrates that the endemic nature of institutional HAI is, in part, because of the inherent complexity and strength of biofilm formation and its resistance to mechanical and chemical assault, making aggressive action in hand hygiene, equipment cleaning/disinfection, and antibiotic stewardess critical areas to target.^13,14

Anesthesia care routinely involves invasive procedures, such as intravenous (IV) line placement, endotracheal intubation, and the use of needles to access nerves and the subarachnoid space, the latter to create what is known as regional anesthesia. These all bypass the usual first-line defense mechanisms of the body. Open-lumen IV access stopcocks are used in direct and continuous continuity with the patient’s circulating blood and are known to be contaminated with pathogenic organisms in about one-third of surgical procedures.^3,5,15 Using sophisticated techniques (e.g., cell genome identification, pulsed-field gel electrophoresis), organisms cultured at the open-lumen stopcock are directly linked to postoperative infection development in addition to being associated with increased postoperative death.^3,5,15

The presence of pathogens of any kind (bacterial, viral, and fungal) on high-touch areas (such as those in the present study) and the ease of their transfer to a patient’s IV access ports and to their airway during even routine care merits study and innovation to establish strategies that may prove beneficial in reducing the risk of AW-related infectious iatrogenesis. That providers wear disposable gloves is an essential component of patient care; gloving or wrapping the high-touch, difficult-to-clean ADM components seems rational on a foundational level.

The few deficiencies and concerns noted in the qualitative component of the study were largely related to the wraps slipping off. This occurred on 2 occasions with the oxygen control, likely explaining contamination in the intervention group. There were no patient safety concerns raised (e.g., hindrance of care) by the providers in the intervention group. These deficiencies are currently being addressed with attention to fit and texture of device fabric.

With respect to disinfection of equipment prior to subsequent patients coming into contact with it, the covered condition (i.e., machines with wrap barriers in place) not only served as a barrier to contamination of apparatus hot spots but served as a preventive measure to subsequent downstream (next-patient) exposure. This was a function of cover being removed at each procedure end, thus mitigating the need for between-procedure disinfection.

Although the study was conducted in a single, large metropolitan facility in the United States, the implications are significant both domestically and internationally where infectious disease transmission remains a significant public health issue. The COVID-19 crisis is but 1 condition that exemplifies the very real concerns with doing everything possible to mitigate the risk of pathogenic transmission in the health care setting.

CONCLUSION

Previous work demonstrated that use of a full apparatus barrier conveyed significant benefit to the patient in mitigating the risk of cross-contamination yet may meet resistance by providers because of access constraints. In this proof-of-concept, clinical pragmatic trial, it was demonstrated that strategic barrier applications to high-touch, universally contaminated niches on the ADM conveyed patient safety benefits by theoretically reducing the risk of AW-acquired infection and add to the call for evidence noted in the recent authoritative guidance document. This research further validates the need for routine, periodic culturing of anesthetic apparatus to reveal lapses in provider behaviors and disinfection practices.

Future research should include a larger sample size, multi-institutional representation, and an even broader patient population, including obstetrical and pediatric patients. Likewise, investigating the use of novel techniques, such as that described in the current study targeting fungal and viral pathogens, is warranted.