gms | German Medical Science

In the context of a clinical trial, bone marrow extractions via iliac crest puncture were to be performed in a cardiac procedure room. In this room, pacemaker and defibrillator implantations are performed in addition to coronary angiographies and, if necessary, surgical interventions (e.g. stent implantation). The respective procedure room is equipped with a ventilation and air conditioning (VAC) system. This system was retrofitted; therefore, inlets and outlets were installed on the walls for constructional reasons. Only one outlet is located at the ceiling. When the cardiac catheter laboratory was retrofitted with the VAC system, a version of DIN 1946-4 [1], in effect until 2008, applied; room class 1 was not further subdivided in this version. Only in the 2008 edition of DIN 1946-4 [2] are rooms in which minor procedures (insertion of small implants, invasive angiographies, cardiac catheterizations and endoscopic examination of sterile body cavities) are performed explicitly defined as cleanroom class 1b. Accordingly, the following requirements had to be met: mixed airflow, positive air balance (positive pressure in the procedure room), no defined protection zone and outdoor air rate of 1200 m³/h.

After inquiry at the “Arzneimittelüberwachungs- und -prüfstelle des Landesamts für Gesundheit und Soziales Mecklenburg-Vorpommern” (State Office of Drug Surveillance and Testing, State Office of Health and Social Welfare, Mecklenburg-Vorpommern) and a subsequent site inspection, concerns were raised regarding hygienic safety during the harvesting of bone marrow. It was said that the equipment, monitors and furniture of the said cardiac procedure room would hamper cleaning and disinfections measures, would probably impair functional capability of the ventilation and air conditioning system and could, in summation, result in an increased risk of contamination during the aseptic extraction of bone marrow via iliac crest puncture. To dispel the concerns of the supervisory body, the quality of ventilation with verification of the protection zone and measurement of the microbial and particulate pollution of indoor room air at rest and during a simulated bone marrow extraction (in operation), as well as the impact of surface disinfection and sterile draping of the furniture on indoor air quality were to be investigated.

In principle, it can be assumed that there is no risk of contamination by room air during the harvesting of bone marrow cells via iliac crest puncture. On the contrary, maintenance of aseptic conditions is determined by the level of patient skin antisepsis, draping of the puncture area, preoperative surgical hand disinfection, sterile clothing of the surgical team and the use of surgical masks.

The room (Figure 1 [Fig. 1]) is ventilated by two large, plate-shaped intake filters (Z1 and Z2, each approx. 2 m high and 1.5 m wide) with terminal H13 filters. The exhaust air is discharged through the exhaust outlet A1 on the ceiling of the room, and through exhaust outlet A2 over the entire vertical extent of the wall. This results in mixed airflow in the room.

To determine whether the VAC system results in a displacement of indoor room air, airflows in the room were visualized using a fog generator, and the flow pattern was documented by video recordings.

To test the performance of the VAC system, the number of particles and colony forming units (CFU) in the room air before and after disinfection were determined at rest and in operation. For in-operation measurements, a surgical procedure was simulated. The team consisted of the operating physician, an assisting nurse and a patient. Two additional persons were present in the operating room as measurement personnel.

Particle counting (size classes 0.5 µm and 5.0 µm) was carried out using an ABAKUS^TM Air airborne particle counter (LMT Leschke Messtechnik Frankfurt/Oder). Prior to measurement recordings, zero adjustment was performed with a particle-impermeable cleaning filter. Measurements were conducted in triplicate, and the analysis was based on mean values. To determine the number of CFUs in the room air, the airborne bacteria sampler MAS 100 (Zinsser Analytik Frankfurt/Main) was used. Cultivation was carried out on Columbia Blood Agar (heipha Dr. Müller GmbH, Eppelheim). For contact sampling of surfaces, RODAC plates with blood agar and Tween/lecithin/histidine disinhibitor (heipha Dr. Müller GmbH, Eppelheim) were used. After sampling, the plates were incubated for 48 h at 36°C as described [3] and subsequently incubated for 7 d at 22°C for the detection of fungi.

Besides the operating table, the cardiac catheter laboratory is equipped with an X-ray unit, an emergency trolley with defibrillator, an anesthesia unit, a desk, a medicine trolley and monitors that are permanently installed on the ceiling. To reduce the impact of furniture and equipment on room air contamination, all furniture and equipment were covered with sterile surgical drapes (Figure 2 [Fig. 2], Figure 3 [Fig. 3]).

The air pressure in the procedure room was positive with respect to the anteroom.

Due to the positioning of the intake and exhaust filters (Figure 1 [Fig. 1]), there was a risk of short-circuit airflow. The existence of short-circuit airflow was ruled out by visualization of airflow conditions. Furthermore, it could be ascertained that there was no functional impairment of the VAC system due to monitors or other equipment being located in the room. In addition, a zone in which no turbulence was observed and in which room air was conducted uniformly to both sides and downwards was identified within the operating area. The position of this optimal zone without turbulence and with conduction of descending air was marked on the ceiling to ensure that the operating physician can stay within the protection zone during performance of an iliac crest puncture.

Since no limit values exist for the evaluation of air quality in rooms used for medical purposes, the evaluation was conducted according to guideline values for cleanroom classes according to the EU Guideline to Good Manufacturing Practice for Medicinal Products (EG-Leitfaden der Guten Herstellungspraxis für Arzneimittel) [4], and the action and limit values derived from it (Table 1 [Tab. 1]).

Particle counts at rest measured in the cardiac catheter laboratory were in clean room class D range (Table 2 [Tab. 2]), except for measuring point A1. Particle counts in the anteroom with values approx. 2 to 3.5 times higher than above the operating table indicated a functional mixed airflow (Table 2 [Tab. 2]).

No CFUs were detectable in the supply air, which verified the integrity of the VAC system. CFU counts in the room air the of the operating field area were in clean room class C range, which is acceptable in mixed airflow conditions (Table 2 [Tab. 2]). For evaluation of CFUs, the EU guideline does not distinguish between measurements “at rest” and “in operation”. However, with 5 people present in the room, no or only a minor increase in CFUs in the room air was observed. The detected bacterial species were without exception non-pathogenic bacteria/commensals of the body surface. No pathogenic bacteria could be isolated.

The particle count in the cardiac procedure room could be significantly decreased by disinfecting surfaces and equipment as well as covering equipment with sterile drapes prior to the scheduled iliac crest puncture. This is illustrated by the reduced particle counts for measurements at rest (Table 2 [Tab. 2], Table 3 [Tab. 3]). Moreover, particle counts measured in operation were all in cleanroom class B range according to the EU guideline and significantly below particle counts in the control room, which is also ventilated, and in the unventilated anteroom. In some cases, the particle count of the in-operation measurement showed a 10fold reduction (Table 3 [Tab. 3]) compared to the preceding measurement at rest (Table 2 [Tab. 2]). Another notable finding was that in operation, particle counts for the 0.5 µm size class in the operating field did not increase (but even decreased), only in the 5 µm size class, an approximately 2fold increase was observed.

In the operating area, particle counts are low compared to other measurement points; this confirms the efficient routing of airflow in this area.

According to the EU guideline for Good Manufacturing Practice, CFU counts in the area of the operating field at rest were in cleanroom class B range (limit 10 CFU/m³) and in operation in the lower cleanroom class C range (limit 100 CFU/m³, Table 4 [Tab. 4]). The EU guideline does not distinguish between measurements “at rest” and “in operation” for evaluation of CFUs. However, with 5 people present in the room, again no or only a minor increase in CFUs in the room air was observed. Thus, only minor microbial contamination of room air, which can be reliably controlled by the VAC system, was observed even under in operation conditions.

The detected bacterial species were without exception body surface commensals. No pathogens were isolated in any measurement.

The testing of effectiveness of surface disinfection by contact plate culture in the cardiac procedure room in a spot check indicated that the procedure had been carried out properly (Table 5 [Tab. 5]).

To test the quality of surface disinfection, a hygienic examination of surrounding areas via contact plate cultures was performed in the cardiac procedure room 4 weeks after implementation of the additional protective measures immediately prior to a scheduled procedure. The result did not indicate any microbial hazard (Table 6 [Tab. 6]).

The test results document the functional safety of the VAC system with regard to both particle counts and number of CFUs. This could be confirmed by a separate measurement comparing at rest and in operation conditions during cardiac catheterization. Due to the positioning of the patient and the activity of the team alone, particle counts increased 2 to 4 fold (Table 7 [Tab. 7]). Even more clearly noticeable than in the particle counts is the functional efficiency of the VAC system in the developments of CFU counts in the room air (Table 7 [Tab. 7]). During positioning of the patient, the number of CFUs is increased 4 to 9-fold. During the intervention, the microbial contamination of the room air decreases significantly due to the performance of the VAC system. With one exception, no pathogens were detectable.

Due to the implementation of additional protective measures for improvement of asepsis, particle counts in the procedure room could be reduced by up to 10 fold.

With regard to particle counts and CFU at rest, requirements for cleanroom class B according to the EU guideline were met. Since the EU guideline does not specify any guiding value for “in operation” conditions – which is explained by the fact that it characterizes the conditions for the manufacturing of sterile products, i.e. 5 persons moving through the room without special cleanroom clothing are more than a worst case scenario – it cannot be taken as a basis for “in operation” situations. Moreover, it has to be considered that the EU guideline emphasizes the fact that guidelines should be subject to hygienic interpretation.

From this perspective, the following conclusion can be drawn: from a hygienic point of view, bone marrow aspirations may be performed under the present hygienic air conditions in the cardiac procedure room. This is emphasized by the results of sedimentation plate tests in the operating area (Table 5 [Tab. 5]). Floor disinfection had no impact on particle and germ counts in the operating field when laminar air flow was employed [5], whereas surface disinfection under mixed airflow conditions in combination with aseptic covering of furniture and equipment resulted in an approx. 10 fold reduction of particle and microbial contamination in the operating area.

To permanently guarantee the high hygienic standard for the harvesting of bone marrow in the cardiac procedure room, standard operating procedures (SOP) have been created based on the above findings. Therein, hygienic safety requirements during preparation, execution and aftercare of iliac crest punctures are specified. Moreover, measures for the disinfection of equipment and surfaces as well as the draping of equipment and monitors by the department personnel and the cleaning service are described.

The main provisions are cited in extracts below:

• The harvesting of bone marrow is performed under aseptic conditions comparable to those during a surgical procedure.
• Skin damage, skin disease or infection at or in close vicinity of the puncture site are a contraindication for a bone marrow aspiration
• If necessary, the puncture site and its surroundings have to be cleaned and should subsequently be amply wetted with an alcohol-based skin antiseptic for 1 min using a sterile swab. Afterwards the skin in the puncture area is sealed using Integuseal, followed by sterile covering of the puncture area and a stab incision prior to insertion of the puncture needle.
• No perioperative antibiotic prophylaxis is performed.
• Entry through the air lock, surgical hand disinfection and donning of sterile protective clothing (low performance) are carried out analogously to surgical procedures. During execution of the puncture, the number of persons present in the procedure room should be kept to a minimum. This is underlined by the results listed in Table 7 [Tab. 7].
• Harvesting of bone marrow and blood is carried out according to separate SOPs. For bone marrow aspiration, only single-use puncture needles are used.
• When a bone marrow extraction is scheduled, the procedure room will be subjected to disinfection cleaning on the previous evening after the last cardiac procedure has been completed. The disinfection cleaning is regulated in a separate SOP for the cleaning firm. During the required measurements in the procedure room, surgical masks have to be worn at all times. The mask should only be changed if breathing is impaired due to dampening of the mask.
• On the previous evening, after the disinfection, all equipment and furniture that cannot be removed from the room (including ceiling-suspended and free-standing monitors, C-arm, control cabinet) are also wipe disinfected and covered with sterile draping, shelves are covered with sterile draping. On the next morning, the bone marrow extraction should be performed first, prior to cardiac procedures. Immediately prior to the puncture, the patient contact area is covered with a sterile sheet. After the bone marrow aspiration, a disinfection of the near-patient working area is carried out before the next procedure.

The performance of microbiological monitoring is also laid down in a separate SOP.

The respective department personnel receive instruction on hygienic conduct once a year. At the same time, this instruction is used to check the SOP for necessary amendments.

The cardiology department personnel are highly motivated to implement the content of the SOP. Hygienic investigations and the developing of the SOP were carried out in tight cooperation. Many tasks in the context of the inspection as well as the analysis of the investigation results were carried out in cooperation with the department. This has resulted in a high degree of understanding and individual responsibility.

This has created framework conditions that, in combination with the motivation of the personnel, will accommodate the goal of guaranteeing maximum safety for the patient and ensuring the sterility of the bone marrow extract.