The Journal of Bone & Joint Surgery

The Journal of Bone & Joint Surgery, Volume 92, Issue 11

Scientific Articles | September 01, 2010

Commercial Liquid Bags as a Potential Source of Venous Air Embolism in Shoulder Arthroscopy

Luke Austin, MD¹; Benjamin Zmistowski, BS¹; Bradford Tucker, MD¹; Robin Hetrick, RN¹; Patrick Curry, MD¹; Gerald Williams, Jr., MD¹

¹ Rothman Institute of Orthopaedics, Thomas Jefferson University Hospital, 925 Chestnut Street, Philadelphia, PA 19107. E-mail address for L. Austin: lukesaustin@gmail.com

View Disclosures and Other Information

Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. One or more of the authors, or a member of his or her immediate family, received, in any one year, payments or other benefits in excess of $10,000 or a commitment or agreement to provide such benefits from commercial entities (Johnson & Johnson and Mitek).

Investigation performed at Rothman Institute of Orthopaedics, Thomas Jefferson University Hospital, Philadelphia, Pennsylvania

J Bone Joint Surg Am, 2010 Sep 01;92(11):2110-2114. doi: 10.2106/JBJS.I.01513

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Abstract

Background:

Venous air embolism is a rare but potentially fatal complication of arthroscopy. Fatal venous air embolism has been reported with as little as 100 mL of air entering the venous system. During liquid-only arthroscopy, avenues for air introduction into the joint are limited. Therefore, we hypothesized that commercially prepared 3-L saline-solution bags are a source of potentially fatal amounts of gas that can be introduced into the joint by arthroscopic pumps.

Methods:

Eight 3-L arthroscopic saline-solution bags were obtained and visually inspected for air. The air was aspirated from four bags, and the volume of the air was recorded. A closed-system pump was prepared, and two 3-L bags were connected to it. The pump emptied into an inverted graduated cylinder immersed in a water bath. Both bags were allowed to run dry. Two more bags were then connected and also allowed to run dry. The air was quantified by the downward displacement of water. The experiment was then repeated with the four bags after the air had been aspirated from them. This experiment was performed at three institutions, with utilization of three pump systems and two brands of 3-L saline-solution bags.

Results:

Air was visualized in all bags, and the bags contained between 34 and 85 mL of air. Arthroscopic pumps can pump air efficiently through the tubing. The total volumes of gas ejected from the tubing after the four 3-L bags had been emptied were 75, 80, and 235 mL. When bags from which the air had been evacuated were used, no air exited the system.

Conclusions:

Because a saline-solution arthroscopic pump is theoretically a closed system, venous air embolism has not been a concern. However, this study shows that it is possible to pump a fatal amount of air from 3-L saline-solution bags into an environment susceptible to the creation of emboli. Evacuation of air from the 3-L bags prior to use may eliminate this risk.

Clinical Relevance:

The importance of this study is indicated by the case reports documenting symptomatic and fatal venous air embolism despite the use of modern preventive arthroscopic equipment and techniques.

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Introduction

Introduction | Materials and Methods | Results | Discussion | References

Venous air embolism is a rare but potentially devastating complication of shoulder arthroscopy^1,2. Venous air embolism is defined as the entry of air or other medical gases into the central venous system, producing an air embolism to the right heart or pulmonary artery³. Venous air embolism has a variable clinical presentation ranging from a complete lack of symptoms to fatal cardiopulmonary collapse. When the filtering capacity of the lungs is overcome or an atrial septal defect exists, a venous air embolism may become a cerebral air embolism causing neurologic findings⁴.

During the evolution of joint arthroscopy, various media have been used to distend the joint. Bircher, in 1921, first described using oxygen or nitrous oxide to insufflate the knee joint⁵. This technique became widespread throughout the twentieth century, until two case reports of fatal air embolism (published in 1987 and 1989) revealed the dangers of using air as the insufflating agent^6,7. The authors concluded that the use of air should be abandoned and replaced with the use of saline solution or carbon dioxide (CO₂). Animal studies in which the end point was air embolism or death have shown CO₂ to be five to six times better tolerated than air^8,9. However, CO₂ can still potentiate a clinically relevant gas embolism^10,11; therefore, water or saline solution has become the arthroscopic medium of choice.

The use of liquid rather than gas to distend the joint has theoretically eliminated the risk of venous air embolism and thus decreased the surgeon's index of suspicion for this dangerous complication. Unfortunately, in practice, case reports continue to identify venous air embolism as a complication during arthroscopy. Two case reports of venous air embolism following shoulder arthroscopy have appeared in the literature^1,2. In both reports, the procedure was performed with the patient in the beach-chair position and, prior to initiation of the fluid pump, the shoulder was insufflated with 50 mL¹ or 60 mL² of air. Within one minute¹ and three minutes² after air injection, each patient had a marked decrease in the end tidal carbon dioxide level and experienced cardiopulmonary symptoms diagnosed by the authors as venous air embolism secondary to air insufflation into the joint. Both patients were fully resuscitated and later discharged without sequelae. More recently, a fatal venous air embolism occurred during standard liquid-only shoulder arthroscopy that included distal clavicular excision¹². No gas was injected at any time during the procedure, and a modern closed-system arthroscopic pump was utilized. This incident spurred us to evaluate, in the present study, the possibility of gas entry into a joint when liquid-only arthroscopy is performed without gas insufflation.

The purposes of this study were (1) to establish that gas entry into a joint is possible when liquid-only arthroscopy is performed with a closed-system arthroscopic pump, (2) to evaluate commercially prepared 3-L saline-solution bags as a source of gas, (3) to determine if the amount of gas in these 3-L bags is sufficient to cause clinically relevant or fatal venous air embolism, and (4) to develop a method to eliminate air from the closed-system pumps. We hypothesized that (1) gas entry into the joint is possible with liquid-only arthroscopy with a closed-system pump, (2) there is air in commercially prepared 3-L saline-solution bags, (3) the quantity of air is adequate to cause a fatal venous air embolism, and (4) there are methods available to eliminate air from the closed-system pumps.

Materials and Methods

Introduction | Materials and Methods | Results | Discussion | References

The experimental study was designed to test the above four hypotheses. Each experiment was performed, in an identical manner, at three different institutions. The institutions included a university hospital, a general hospital, and a surgery center. At each institution, the standard arthroscopic equipment and 3-L saline-solution bags were tested. Three different closed-system, peristaltic, arthroscopic pumps and two different brands of 3-L saline-solution bags were studied. The university and general hospitals used the same brand of 3-L saline-solution bag (brand "B"), whereas the surgery center used a different brand (brand "A").

Experimental Design

Eight 3-L bags of saline solution were obtained at random from each institution. The brand and lot numbers of each bag were recorded. The standard arthroscopic equipment at each institution was obtained, and the brand was recorded. Three experiments, as detailed below, were then undertaken.

Experiment 1

Experiment 1 was designed to quantify the volume of gas in each 3-L saline-solution bag. First, each bag was visually inspected for gas. Next, the gas was aspirated from four bags while the bag was inverted, as depicted in Figure 1. The volume of gas that was aspirated was recorded, but the composition of the gas was not ascertained.

Fig. 1

Photograph demonstrating the gas aspiration and quantification method with use of an inverted 3-L saline-solution bag and a sterile 60-mL syringe.

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Experiment 2

Experiment 2 was designed to test the ability of a closed-system pump to pull gas from the 3-L saline-solution bags and eject it from the tubing outlet. Two saline-solution bags were connected to the arthroscopic tubing with use of a Y-adaptor. The arthroscopic tubing was connected to the pump, and the pump was prepared and operated according to the manufacturer's operating instructions. A 250-mL graduated cylinder, marked in 1-mL increments, was filled completely with water and immersed, inverted, in a 10-gallon (37.9-L) container of water. The outlet of the arthroscopic tubing was placed into the inverted graduated cylinder (Fig. 2). As saline solution was pumped through the system, it displaced the water in the graduated cylinder and no changes were seen. However, when gas was pumped through the system, the gas was captured in the inverted graduated cylinder by the downward displacement of saline solution and water and could be quantified to an accuracy of 1 mL.

Fig. 2

Photograph of the experimental apparatus. Air (A) is seen to be trapped in the inverted graduated cylinder immersed in the water bath. The outflow tubing (B) is inserted into the open end of the inverted graduated cylinder. C = arthroscopic pump, and D = 3-L saline-solution bags. The water bath in this picture was different from the one used during the experiment to provide visual clarity of the inverted graduated cylinder.

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The experiment began with the performance of two trials to determine the bleed volume of the arthroscopic tubing. The tubing was primed, and the air was flushed from the tubing into the inverted graduated cylinder and quantified. Next, the volume of air in the cylinder was recorded at three intervals: after the first set of two saline-solution bags had run dry, after the second set of two bags had been connected and the residual air in the tubing had been ejected into the cylinder, and after the second set of bags had run dry. The total gas volume ejected after the four 3-L saline-solution bags had been emptied was then calculated. The experiment was designed to simulate a normal arthroscopic procedure that included one bag transition.

Experiment 3

Experiment 3 was designed to determine whether air would be pumped through the system if all of the gas was removed from the 3-L saline-solution bags before the bags were connected. The procedure for this experiment was identical to that for experiment 2, except that the gas was completely aspirated from all four bags prior to utilization.

Source of Funding

There was no external funding source for this study.

Results

Introduction | Materials and Methods | Results | Discussion | References

Experiments 1 and 2

Table I contains the composite results of experiments 1 and 2 from each institution. Visual inspection of the twenty-four 3-L saline-solution bags revealed gas in every bag. The volume of gas contained within the saline-solution bags depended on the brand of the bag. The volume of gas ranged from 70 to 85 mL (mean, 80 mL; n = 4) in brand "A" and from 34 to 40 mL (mean, 36.6 mL; n = 8) in brand "B."

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TABLE I Results of Experiments 1 and 2

			Saline-Solution Bag				Volume of Gas Entering Cylinder (mL)
Institution	Pump System	Tubing Bleed Volume*(mL)	Brand	Volume (mL)	% NaCl	Volume of Gas in Bag (mL)†	After 1st 2 Bags Emptied	After 2nd 2 Bags Connected and Residual Air in Tubing Ejected	After 2nd Bags Emptied	Total Gas Collected After 4 Bags Emptied
Surgery center	1	72, 72	A	3000	0.9	70, 80, 85, 85	80	70	85	235
University hospital	2	125, 130	B	3000	0.9	36, 40, 35, 37	0	80	0	80
General hospital	3	164, 160	B	3000	0.9	38, 34, 36, 37	0	75	0	75

*The two values in each row represent the results of two trials.
†The four values in each row represent the volumes of the four bags.

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TABLE I Results of Experiments 1 and 2

			Saline-Solution Bag				Volume of Gas Entering Cylinder (mL)
Institution	Pump System	Tubing Bleed Volume*(mL)	Brand	Volume (mL)	% NaCl	Volume of Gas in Bag (mL)†	After 1st 2 Bags Emptied	After 2nd 2 Bags Connected and Residual Air in Tubing Ejected	After 2nd Bags Emptied	Total Gas Collected After 4 Bags Emptied
Surgery center	1	72, 72	A	3000	0.9	70, 80, 85, 85	80	70	85	235
University hospital	2	125, 130	B	3000	0.9	36, 40, 35, 37	0	80	0	80
General hospital	3	164, 160	B	3000	0.9	38, 34, 36, 37	0	75	0	75

*The two values in each row represent the results of two trials.
†The four values in each row represent the volumes of the four bags.

Experiment 2 was performed to evaluate the capability of a closed-system peristaltic pump to pull air from the 3-L saline-solution bags and pump it through the system. First, two trials were performed to determine the volume of the arthroscopic tubing (Table I, column 3). Second, two bags were connected simultaneously and allowed to run dry concurrently, and the volume of gas pumped into the inverted graduated cylinder was measured (Table I, column 8). Third, two new 3-L saline-solution bags were connected and run until the residual air in the arthroscopic tubing was ejected into the graduated cylinder (Table I, column 9). Lastly, the second set of 3-L saline-solution bags was allowed to run dry (Table I, column 10). Table I, column 11, provides the total volume of gas pumped into the graduated cylinder after the four 3-L saline-solution bags were allowed to run dry. The volume of gas collected in the graduated cylinder depended on the volume of gas in the 3-L bags relative to the volume of the arthroscopic tubing. At the completion of each experiment, there was residual gas in the tubing that had not been collected in the graduated cylinder. Presumably, another bag transition would have pumped the residual gas into the graduated cylinder.

Experiment 3

Experiment 3 demonstrated a method to prevent air from being expelled from the closed-system arthroscopic pump. Experiment 2 was repeated after the gas had been evacuated from the saline-solution bags. No air was seen to enter the graduated cylinder or arthroscopic tubing at any collection time during this experiment.

Discussion

Introduction | Materials and Methods | Results | Discussion | References

Venous air embolism is a potentially serious complication of arthroscopy that can lead to cardiopulmonary symptoms, neurologic deficits, and death. The importance of this study is evidenced by the several case reports^1,2 in the literature documenting symptomatic and fatal venous air embolism despite the use of modern preventive equipment and techniques such as closed-system pumps and liquid-only arthroscopy. An additional case report appears in this issue of The Journal¹².

There are many potential pathophysiologic pathways in the development of venous air embolism. The one common thread in all pathways is the introduction of gas into the joint. Therefore, any potential source of extra-articular air should be minimized. To our knowledge, this is the first study to demonstrate that the air seen in commercially available 3-L saline-solution bags may be clinically important for the development of venous air embolism. The results of this study demonstrate that gas is present in 3-L saline-solution bags, the amount of gas is potentially fatal in humans, and gas can be pumped into the joint by most commercial pumps if the bags are allowed to run dry.

The volume of gas needed to cause symptomatic and fatal venous air embolism has been reported in the literature. Two case reports showed that as little as 50 to 60 mL of gas can lead to a symptomatic venous air embolism during shoulder arthroscopy^1,2. Fatal venous air embolism has been reported with gas volumes of 100 to 300 mL^6,13. While fatal venous air embolism is exceedingly rare, we believe that symptomatic venous air embolism is underreported. Our experiment reveals that, with use of four 3-L saline-solution bags, an adequate volume of gas can be pumped into the joint during shoulder arthroscopy to cause a symptomatic or even fatal venous air embolism.

Experiment 3 demonstrated a simple and effective method of eliminating gas from the system and preventing gas from entering the joint. Siphoning all of the gas from the 3-L saline-solution bags prior to connecting them to the pump completely eliminated the problem of gas entering the graduated cylinder (i.e., the joint). The method was 100% effective, and we recommend performing this sterile, simple procedure before the performance of any arthroscopic surgery.

Of note, the volume of the arthroscopic tubing had two interesting effects on the ability of the pump to pull gas from the 3-L saline-solution bags and inject it into the cylinder (Table I). First, the higher-volume tubing had an increased bleed volume and thus can potentially be a source of air entry into the joint if the tubing is not primed. However, we believe that priming arthroscopic tubing is the standard of care, and this source of air may be of little clinical relevance. Second, higher-volume arthroscopic tubing had a preventive effect on air entry into the joint when the 3-L saline-solution bags were allowed to run dry. If the volume of the arthroscopic tubing exceeds the volume of air in the two 3-L saline-solution bags, the air will be trapped in the tubing rather than being injected into the joint. We therefore recommend evaluating the arthroscopic tubing for gas prior to 3-L-bag transitions, especially if the 3-L bags run dry.

There are two limitations to this study. First, we tested only three different brands of arthroscopic pumps. All three brands were peristaltic pumps. It is possible that centrifugal pumps do not behave in a similar manner. Second, we tested only two brands of arthroscopic fluid bags, and there was a substantial variation in gas volume between the brands. Fortunately, 3-L saline-solution bags can easily be evaluated for gas with simple visual inspection, and we recommend that surgeons visually inspect the fluid bags that they are using.

In conclusion, venous air embolism is a potentially fatal complication of shoulder arthroscopy. Because a liquid-only arthroscopic pump is theoretically a closed system, venous air embolism has not been a concern. However, this study demonstrates that, when standard protocol is followed, it is possible to pump a fatal volume of air from commercially prepared 3-L saline-solution bags into an environment susceptible to the creation of air emboli. Surgeons should understand that venous air embolism remains a potential complication of arthroscopy and take every precaution to prevent air from entering the joint.

References

Introduction | Materials and Methods | Results | Discussion | References

Hegde RT; Avatgere RN. Air embolism during anaesthesia for shoulder arthroscopy. Br J Anaesth. 2000;85:926-7.[PubMed][CrossRef]

Faure EA; Cook RI; Miles D. Air embolism during anesthesia for shoulder arthroscopy. Anesthesiology. 1998;89:805-6.[PubMed][CrossRef]

Kim CS; Kim JY; Kwon JY; Choi SH; Na S; An J; Kim KJ. Venous air embolism during total laparoscopic hysterectomy: comparison to total abdominal hysterectomy. Anesthesiology. 2009;111:50-4.[PubMed][CrossRef]

Butler BD; Hills BA. The lung as a filter for microbubbles. J Appl Physiol. 1979;47:537-43.[PubMed]

Bircher E. Die Arthroendoskopie. Zentralbl Chir. 1921;48:1460.

Habegger R; Siebenmann R; Kieser C. Lethal air embolism during arthroscopy. A case report. J Bone Joint Surg Br. 1989;71:314-6.[PubMed]

Grünwald J; Bauer G; Wruhs O. [Fatal complication in arthroscopy in a gaseous medium]. Unfallchirurg. 1987;90:97. German.[PubMed]

Graff TD; Arbegast NR; Phillips OC; Harris LC; Frazier TM. Gas embolism: a comparative study of air and carbon dioxide as embolic agents in the systemic venous system. Am J Obstet Gynecol. 1959;78:259-65.[PubMed]

Moore RM; Braselton CW. Injections of air and of carbon dioxide into a pulmonary vein. Ann Surg. 1940;112:212-8.[PubMed][CrossRef]

Staffieri F; Lacitignola L; De Siena R; Crovace A. A case of spontaneous venous embolism with carbon dioxide during laparoscopic surgery in a pig. Vet Anaesth Analg. 2007;34:63-6.[PubMed][CrossRef]

Mommerot A; Perrault LP. Carbon dioxide embolism induced by endoscopic saphenous vein harvesting during coronary artery bypass grafting. J Thorac Cardiovasc Surg. 2006;132:1502-3.[PubMed]

Zmistowski B; Austin L; Ciccotti M; Ricchetti E; Williams G Jr. Fatal venous air embolism during saline solution-only shoulder arthroscopy. A case report. J Bone Joint Surg Am. 2010;92:2125-7.

Yeakel AE. Lethal air embolism from plastic blood-storage container. JAMA. 1968;204:267-9.[PubMed] [CrossRef]

Topics

arthroscopy ; mali ; venous air embolism ; tubing ; saline solution ; shoulder arthroscopy ; arthroscopy pump

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Luke Austin, Benjamin Zmistowski, Bradford Tucker, Robin Hetrick, Patrick Curry, Gerald Williams, Jr.; Commercial Liquid Bags as a Potential Source of Venous Air Embolism in Shoulder Arthroscopy. The Journal of Bone & Joint Surgery. 2010 Sep;92(11):2110-2114.

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