Released July 2024

Introduction

In the field of pharmacy compounding, maintaining aseptic technique is paramount to ensure the safety and efficacy of compounded medications. One of the key elements in maintaining the sterility of admixture components is the effective use of laminar air flow provided by primary engineering controls (PECs). Understanding how aseptic manipulations are performed and how objects are arranged within the direct compounding area (DCA) will prevent turbulence, and other air-flow related contamination events during compounding. Acquiring expertise on how to utilize laminar flow to your advantage will significantly enhance the quality of your compounding practices and the safety of your CSPs.

Best Practices for Utilizing Laminar Flow

To maximize the benefits of laminar flow, pharmacy professionals should adhere to best practices that ensure critical sites are exposed to HEPA-filtered air at all times within the PEC.

Not only is it critical to properly benefit from laminar flow but also to be close enough to air exiting HEPAs. This is essential to achieve a proper “air-bath” (first air). By contrast, there’s an area of backwash contamination within the first six inches of a deck’s surface. Aseptic manipulations must never occur in this zone but only in the DCA, this often referred to as “the six inch rule”. Disruptions in laminar flow, often caused by the operator’s actions, can compromise the sterility of the compounded medication. Consistently blocking or preventing exposure to laminar flow air is akin to not using a PEC at all, which significantly increases the risk of contamination. To illustrate, consider the scenario of preparing a sterile compound on a worktable without the benefit of HEPA-filtered PEC air. Without laminar flow, the risk of contamination from room air, operator movements, and equipment increases dramatically, making it nearly impossible to maintain the sterility of the CSP. To help reduce disruptions in laminar flow it’s important to identify the type of hood, or direction of your air flow, you will be working with.

Types of Laminar Flow Hoods and Their Applications

Horizontal Laminar Flow Hoods

· Description: These hoods direct HEPA-filtered air horizontally across the work surface towards the operator.

· Best Uses: Ideal for non-hazardous sterile compounding, such as preparing IV medications and ophthalmic solutions. Horizontal flow minimizes the risk of contamination from the operator’s breath or movements.

Vertical Laminar Flow Hoods

· Description: These hoods direct HEPA-filtered air vertically downwards onto the work surface.

· Best Uses: Suitable for hazardous drug compounding (e.g., chemotherapy drugs) as they provide additional protection to the operator. The downward airflow helps to capture hazardous particles and direct them away from the operator.

Figure 1.1: Table Detailing Horizontal and Vertical Laminar Flow Hoods

Supplies and Air Flow

When removing wrappers from sterile supplies, the “peel and present” method should be employed. This technique minimizes the risk of introducing contaminants by ensuring that sterile surfaces are exposed directly to the laminar airflow. Similarly, when making luer-lock connections or penetrating septa, these actions should be performed with the connection points In the path of HEPA-filtered air to maintain sterility.

The Designated Compounding Area (DCA)

In order to use laminar flow to your advantage you must work within the DCA.  

Although hoods are not typically marked with a designated compounding area (DCA), it is crucial for operators to recognize the optimal DCA to maintain optimal hood use. Working too close to the outside edge of the hood can result in room air mixing with the hood air, leading to potential contamination. Therefore, compounding should always occur within the central, protected area of the hood where laminar flow is most effective. 

Designating an appropriate DCA involves understanding the airflow dynamics within your hood and identifying the area where laminar flow is most effective. See Figure 1.1 above.  

 Additionally, where (and how) supplies and equipment are paced within the DCA are essential for optimal hood use. Supplies and equipment should be placed in a way that does not obstruct the airflow. Make sure to maintain a clear path for the laminar flow from the HEPA filter to the critical sites. To help to determine the ideal position for your equipment within the DCA, using airflow indicators such as smoke sticks, to visualize the flow within the hood can help identify areas where laminar flow may be disrupted by equipment, or operator movements.  

Avoiding Common Pitfalls

Blocking or Shadowing Laminar Flow

One common operator error in utilizing laminar flow is blocking or shadowing the airflow with hands, supplies, or equipment. This can be avoided by positioning hands and materials in a manner that does not impede the airflow. For vertical laminar flow hoods, a staggered checkered pattern is acceptable, while for horizontal flow hoods, maintaining an even plane of exposure is recommended.

Maintaining Compounding Equipment

Ensuring that all compounding equipment is certified and in good working order is essential to maintaining ISO-5 conditions. This includes regular maintenance and calibration of PECs to ensure they provide the environment they were engineered for. Additionally, operator habits play a significant role in maintaining these conditions. Training in recognizing a malfunctioning PEC (air handler noise, dimmed lighting, and maintenance tips ex.pre-filter exchanges), can increase operator awareness and expertise in the use of compounding equipment.

Conclusion

In conclusion, utilizing laminar flow to your advantage is crucial for maintaining aseptic conditions in pharmacy compounding. By understanding the dynamics of laminar flow, recognizing the importance of maintaining aseptic conditions and adhering to best practices, pharmacy professionals can ensure the safety and efficacy of their compounded medications. Remember, consistent exposure to HEPA-filtered air and avoiding disruptions in laminar flow are key to successful aseptic compounding.

About the Author

Luis Hernandez, RPh, BCSCP, is a certified sterile compounding pharmacist and the founder of Seven97 Training Solutions. Dedicated to advancing USP 797 pharmaceutical training, validation, and certification, Luis aims to promote and inspire excellence in aseptic processing, medication and patient safety, and regulatory compliance.

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