Anesth Analg 2003;97:1074-1077
© 2003 International Anesthesia Research Society
TECHNOLOGY, COMPUTING, AND SIMULATION
Relative Performance of the Level 1 and Ranger Pressure Infusion Devices
Michael P. Eaton, MD, and
Anahat K. Dhillon, BA
Department of Anesthesiology, University of Rochester School of Medicine and Dentistry, Rochester, New York
Address correspondence to Michael P. Eaton, MD, Department of Anesthesiology, University of Rochester School of Medicine and Dentistry, 601 Elmwood Ave., Box 604, Rochester, NY 14642. Address e-mail to michael_eaton{at}urmc.rochester.edu Reprints will not be available from the author.
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Abstract
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Pressure infusion devices are often used to administer fluids in the operating room, but they may rarely be associated with serious venous air embolism. We studied the performance of the Level 1 and the Ranger Pressure Infusor in the laboratory. The Ranger delivered less air and delivered fluid faster than the Level 1 but did not warm fluid or blood as well. Although the Ranger device may be safer in terms of the risk of air embolism, its inferior warming performance shows that the optimal pressure infusion device has yet to be manufactured.
IMPLICATIONS: Pressure infusion devices are widely used to treat patients with large-volume blood loss. The use of these devices may subject patients to the risk of venous air embolism. Our study found the new Ranger device to be superior to the widely used Level 1 in air elimination.
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Introduction
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Pressure infusion devices (PIDs) such as the Level 1 (Level 1 Technologies, Inc., Rockland, MA) are widely used to maintain normovolemia and normothermia in patients experiencing large-volume blood loss. The development of these devices has allowed anesthesiologists to manage patients undergoing trauma, vascular, and other complex operations with significantly less risk of hypovolemia, hypothermia, and associated morbidity and mortality.
However, the use of PIDs is not without risk. IV fluid bags and other bags used in volume delivery (e.g., cell-saver bags) contain volumes of air sufficient to cause significant venous air embolism (VAE) (1,2). To avoid this complication, the clinician using a PID must always carefully purge all air from the bag before its placement in the device, or the PID itself must purge the air during infusion. The need to remove air from any fluid container used in the device is emphasized in the instructions for the Level 1 and Ranger (Ranger Pressure Infusor; Augustine Medical, Eden Prairie, MN) PIDs. Because these devices are often used during cases involving large-volume shifts accompanied by significant hemodynamic instability, the clinician may at times be distracted from removing the air from bags placed in the PID. Adhikary and Massey (3) reported a case of fatal air embolism resulting from the use of the Level 1 PID. Many anesthesiology departments have had such mortalities or near misses (O’Reilly M, personal communication, 2002). At the October 2002 Director’s Retreat of the Anesthesia Patient Safety Foundation, Dr. O’Reilly, the session moderator, stated that until the air embolism risk has been minimized, available PIDs should be taken off the market.
Recently Augustine Medical introduced a PID, based on their Ranger blood/fluid warmer, that the company claims has superior air elimination capabilities compared with competing devices. We undertook this study to determine whether the Ranger PID eliminates air better than the Level 1 device and also to assess its abilities to deliver fluid rapidly at physiologic temperature.
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Methods
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In a laboratory evaluation, two different Level 1 PIDs (System H-1025; Level 1 Technologies, Inc.) owned by Strong Memorial Hospital were compared with two Ranger PIDs supplied to the hospital for evaluation by the manufacturer. All devices were evaluated for function by the hospital’s medical engineering laboratory before use. Two different disposable fluid sets for the Level 1 were evaluated: the D50 and D100. Two of each of these disposables were used in each Level 1. Two Ranger high-flow fluid sets were used in each Ranger PID. All sets were new out of the box and were inspected for flaws before use. Each disposable was put through an identical series of fluid-delivery trials to assess its ability to deliver fluid rapidly, warm the fluid to physiologic temperature, and purge air from the system (Table 1).
Data were analyzed with the JMP statistics package for Macintosh (SAS Institute, Inc., Cary, NC). Tukey-Kramer honestly significant difference analysis for comparison of multiple paired data was used to compare fluid and blood delivery times, temperatures, and air delivery.
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Results
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The Ranger device was more effective in eliminating air from the fluid set at all challenge volumes (Table 2). The Ranger PID delivered fluid at a faster rate than the Level 1 with either set, but at a lower output temperature (Table 2).
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Discussion
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The recent Institute of Medicine Report on Medical Errors (4) highlights the need for complex medical devices such as PIDs to be as safe as possible. Using systems solutions (i.e., making the environment, equipment, and procedures safer) to minimize risk in potentially fatal situations is mandatory when predictable human behavior (such as failure to remove air from fluid bags) may increase that risk. Currently available PIDs, such as the Level 1, are not safe if clinicians do not always take the extra steps required to de-air bags of IV fluid before placing them in the device to avoid VAE. Although appropriate de-airing may occur most of the time, case reports and anecdotal evidence suggest that clinicians occasionally omit this safety step (2,3). A better system design would include one or more mechanisms to prevent the adverse sequelae of such an oversight.
The degree of morbidity from VAE is a function of both the volume embolized and the rate at which it enters the heart. Rapid air infusion is more likely to be lethal, with <50 mL causing symptoms in adults (5) and as little as 200 mL being potentially fatal (2). A PID pressurized to 300 mm Hg (standard operating pressure in the PIDs tested) can cause delivery of this fatal dose in as little as 4 seconds.
Both Level 1 and Ranger disposables incorporate a gas-permeable membrane that allows air to leave the system without fluid leakage. The membrane in the Level 1 disposable is incorporated into a combination filter/air eliminator distal to the warming element (Fig. 1). The membrane surface area is 0.57 cm2, less than one thirtieth of the Ranger’s membrane area of 17.7 cm2. This large difference in the area available for air purging likely explains the significant difference in performance between the two devices. Hartmannsgruber and Gravenstein (1) found that at rapid flow rates, the Level 1 allowed up to 98% of a 60-mL air bolus to pass by the air eliminator. Sixty milliliters is within the range of air volumes we typically found in unspiked IV fluid bags.
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Figure 1. Air-purging elements of the Level 1 (left) and Ranger (right). Center is the Level 1 element seen end-on with the cap and filter cut away. Arrows indicate gas-permeable membranes.
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Although it would be uncommon to encounter 200 mL of air in commercially available IV fluid bags, we chose this volume for our study for four reasons: 1) it has been described as a minimal fatal dose (2), 2) it would be a more stringent test of the air-venting systems on the PIDs investigated, 3) previous studies revealed that the Level 1 air eliminator performed poorly at smaller air volumes (1), and 4) 200 mL was the maximum air volume that would fit easily into full liter bags of normal saline. Additionally, it is likely that bags filled by automated blood salvage devices contain significantly larger amounts of air, consistent with reports of fatal VAE (2). Although the Level 1 may have vented air effectively at slow flow rates, we were primarily interested in the maximum risk of VAE, so we chose to study the systems at their fastest flow rates. These flow rates are frequently used in resuscitation and also maximally stress the devices’ ability to warm fluid and blood.
According to our data, the Ranger Pressure Infusor seems to be an acceptable alternative to the Level 1, at least in terms of minimizing the potential for air embolism. However, lower delivered fluid temperature with the Ranger Pressure Infusor may place patients at risk for hypothermia.
Large-volume blood loss during surgery stresses both resuscitation equipment and the clinician, creating an environment that favors errors of omission. The need to minimize the adverse effects of these errors mandates that companies improve the design of their products to ensure that all clinicians have access to safe, reliable fluid resuscitation equipment.
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Acknowledgments
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Supported in part by a grant from Augustine Medical, Eden Prairie, MN.
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References
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- Hartmannsgruber MWB, Gravenstein N. Very limited air elimination capability of the level 1 fluid warmer. J Clin Anesth 1997; 9: 233–5.[ISI][Medline]
- Linden JV, Kaplan HS, Murphy MT. Fatal air embolism due to perioperative blood recovery. Anesth Analg 1997; 84: 422–6.[Abstract]
- Adhikary GS, Massey SR. Massive air embolism: a case report. J Clin Anesth 1998; 10: 70–2.[ISI][Medline]
- Kohn LT, Corrigan JM, Donaldson MS. To err is human: building a safer health system. Washington, DC: National Academy Press, 2000.
- deWet C, Harrison L, Jacobsohn E. Air embolism. In: Atlee JL, ed. Complications in anesthesia Philadelphia: Saunders, 1999: 323–5.
Accepted for publication June 3, 2003.
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Abstract
Introduction
