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Anaesthesia medication dispensing systems

Automation was first introduced into pharmacy practice as early as the 1970s in the form of electronic tablet counters. Unit-dose dispensing and pharmacy-based original pack dispensing systems soon followed.1

In 1989, the Pyxis MedStation (Cardinal Health, USA) was introduced onto the US market as a point-of-use automated medication management system that resides on hospital floors.2 Multiple studies have shown improved patient safety, reduced medication errors, improved efficiency, improved billing, improved regulatory compliance and improved stock management, leading to better inventory control.3-5

Other manufacturers soon followed with their own version of point-of-use automated management systems;6 however, the Pyxis MedStation is in use in nearly 90% of all US hospitals and over 4,500 healthcare facilities around the globe, and it dispenses more than 3.8 million medications each day.7

Automation in the operating room environment

One area that has been sorely lacking in automation of medication dispensing, however, is the operating room environment. Since anaesthetists administer approximately 25% of all medications in the hospital setting,8 an automated solution that has the potential of improving patient safety, reducing medication errors, increasing billing, controlling inventory and improving regulatory compliance in this arena has been sought.

In 2000, Pyxis Anesthesia Systems (A-System; see Figure 1) were introduced onto the US market.9 These systems were designed to replace the anaesthesia “cart”, with both medication and supply dispensing in mind.


  • The A-System

The A-System was designed as a five-drawer system where the top two drawers simulate a Pyxis MedStation. A computer keyboard is mounted at the top of the machine and the user enters a username and password to access the system.

Once in the system, the bottom three drawers unlock, remaining “anchored on” throughout the surgery. The anaesthetist can access any supply in the bottom three drawers, manually entering its removal into the keyboard for tracking, control, restocking and inventory.

However, to remove a medication, the user must select a patient name from a list supplied automatically from the hospital admission-discharge-transfer (ADT), select a medication to be administered from the Medication List (supplied automatically by pharmacy from the stocked formulary items) and remove the medication once it has been dispensed by the A-System.

The A-System has the capability of limiting the dispensing of medications to a single vial or ampoule by its “Mini-Matrix” drawer design. In the Mini-Matrix drawers, the entire drawer does not open; instead, the drawer opens only to the point where the next vial or ampoule of medication can be accessed.

This design seems to be an improvement over previous ones, as it limits the removal of medications by the user to the drug previously requested. However, this has led to unacceptable limitations in emergency situations, since emergency medications cannot be accessed immediately.

In response to this, the recommendation from the manufacturer is to locate an additional “locked” box on top of the Pyxis A-System for immediate access in an emergency. However, these boxes generally “disappear” and are not readily available when needed, thus leading to limited availability of emergency medications.

Another issue of concern with the original design and marketing of the Pyxis A-System is the “free access” to supplies in the bottom three drawers,  requiring manual entry of their removal. Also, since the A-System is regulated by the FDA, only pharmacy formulary items may be placed in the machine. This leads to cumbersome pharmacy formularies that include supplies not controlled or stocked by pharmacy.

  • Reconfiguration of the A-System

In light of these issues and in response to the limited access to emergency medications, a drawer reconfiguration of the A-System was needed. All anaesthesia supplies were removed and located in an automated supply tower (available as Pyxis SupplyStation or Omnicell Supply Towers), while the A-System was reconfigured using all five drawers for medications only.

This separates all medication and supply automation, and allows management and control by the respective departments responsible for their oversight. In the Pyxis A-System, all controlled substances, high-alert, lookalike and high-cost medications can be placed in the Mini-Matrix drawers, thus requiring an “extra step” for the user to obtain the medication and allowing close control of these items. Emergency medications and large items (too large to fit in a Mini-Matrix drawer, such as 5% albumin) can be located in the bottom three drawers.

One flaw in this configuration, however, is that the medications located in the bottom three “free access” drawers require manual entry into the system upon their removal, thus reducing control and monitoring. These drawers typically show lower compliance of medications removed, and occasionally allow stock-outs, since medications are filled primarily from an automated list generated by the Pyxis Anesthesia System that is sent directly to the pharmacy.10

Lost billing and charges, decreased inventory control, decreased regulatory compliance and fewer steps to obtain these medications that could result in inadvertent medication error make this design configuration less than ideal.

However, “free access” to emergency medications is a positive result. The preliminary results of a current study at the University of Miami regarding practitioners’ opinions of whether there is any limited access or hindrance caused by automated anaesthesia medication dispensing systems suggest that, overall, practitioners are comfortable that, in an emergency situation, medications will always be ready and available for immediate administration to the patient.

A suggestion of adding barcode technology to the machines has been made to the manufacturer, which may result in improved patient safety and compliance by the quick scan of all medications removed, including those in the bottom three “free access” drawers.


Although not yet perfect, anaesthesia medication dispensing systems have arrived on the scene and will require clinical trials and continuous design updates to see how best to improve automation to meet the need for improved patient safety and improved regulatory and inventory/billing compliance.


R Lebron Cooper MD
Director, Medication Safety
Miami Center for Patient Safety, University of Miami School of Medicine/ Jackson Memorial Hospital
Miami, Florida, USA
E:[email protected]


1 Swanson D. Automated dispensing – an overview of the types of systems available. Hosp Pharm 2004;11:66-8.

2 Milestone demonstrates Pyxis Corporation’s leadership in delivering automated technology for patient safety. Available at: (accessed December 2004).

3 Drug lawsuit government report. Medication dispensing machines may reduce errors. Available at: (accessed December 2004).

4 Hulse K, Edmundson L, Carroll R. Diversion of controlled substances: a catalyst for change. J Healthc Qual 2004;26:6-11,17.

5 Stevenson B. Automated medication dispensing enhances patient safety, pharmacist clinical interventions. Oconee Memorial Hospital, Seneca, SC, USA; 2002.

6 Company Profile, Omnicell Corporation. (accessed December 2004).

7 Pyxis Products Division, Cardinal Health. Available at: (accessed December 2004).

8 Medication report, Jackson Memorial Hospital. 2004 (Miami, FL, USA).

9 Introducing the new Pyxis‚ Anesthesia System, 2000. Available at: (accessed December 2004).

10 User discrepancy report, Jackson Memorial Hospital Pharmacy, January–December 2004. (Miami, FL, USA).

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