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Fatal Air Embolism Due to Perioperative Blood Recovery

Linden, Jeanne V. MD, MPH; Kaplan, Harold S. MD; Murphy, Mark T. MD

General Article

This study was initiated to investigate the incidence of acute mortality from air embolism associated with perioperative blood recovery and the causative factors and common characteristics of such fatalities.All facilities providing transfusion services in New York State are required to report severe adverse reactions to, and the total number of, transfusion and blood recovery procedures performed. Relevant data for the period from January 1990 to June 1995 were tabulated. During this time, 127,586 perioperative blood recovery procedures were performed, and 8,955,619 conventional blood components were transfused. The frequency of fatal air embolism after readministration of recovered blood was approximately 1:30,000-1:38,000; none followed conventional transfusion. Characteristics common to the fatalities (including an additional case reported before the study interval) were examined; all involved reinfusion of recovered blood under pressure. In the population studied, the incidence of fatal air embolism after the perioperative readministration of recovered blood was significantly higher than that after conventional transfusion. A model of such a system demonstrated that as much as 200 mL of air could enter the circulation in as little as 4 s, rendering visual detection and intervention extremely difficult. Education and guidelines to reduce the risk and mortality associated with this procedure are recommended.

(Anesth Analg 1997;84:422-6)

(Linden) Wadsworth Center, New York State Department of Health, Albany, New York; and Departments of (Kaplan) Pathology and (Murphy) Anesthesiology, Southwestern Medical Center, Dallas, Texas.

Accepted for publication October 18, 1996.

Address correspondence and reprint requests to Jeanne V. Linden, MD, MPH, Wadsworth Center, New York State Department of Health, P.O. Box 509, Albany, NY 12201-0509.

Intraoperative and postoperative blood recovery techniques (IBR and PBR, respectively) have become increasingly popular as concerns regarding blood safety have heightened demand for alternatives to allogeneic blood transfusion. With standard techniques, the amount of hemolysis associated with blood recovery is generally low, and red blood cell survival is normal [1-4]. Such techniques are not completely benign, however. The primary reported complications of autotransfusion are coagulopathy [5-7], dissemination of infection [8,9], and air embolism [10-13].

This study was initiated to investigate the incidence of fatal air embolism associated with perioperative reinfusion of recovered blood compared with that associated with allogeneic blood transfusions.

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Since 1990, the New York State (NYS) Department of Health has mandated reporting of errors, incidents, and severe adverse reactions to blood transfusion. Reporting of the total number of transfusion and blood recovery procedures is also required. There is 100% compliance with this reporting requirement. Data were tabulated for the period of January 1990 to June 1995. Four fatal air embolism incidents (and an additional case reported in 1986 but included here to facilitate comparison) were examined to identify causative factors.

Additionally, a simple experiment was conducted to evaluate the time available for the visual detection of air and for manual cutoff in a standard intravenous delivery system under pressure. The typical blood recovery circuit (Figure 1) includes a blood collection unit to recover shed blood from the patient. A model was devised to simulate a typical rapid intravenous fluid administration system in which external pressure is applied. The model allowed an estimation of the flow rates that might occur in such a system containing air and fluid. Known graduated volumes of air were placed in a standard 1-Liter infusion bag of lactated Ringer's solution; the remaining volume consisted of crystalloid solution. A standard pressure bag was placed around the infusion bag and inflated to 300 mm Hg. To mimic what would typically occur in a clinical setting, no attempt was made to maintain constant external pressure at 300 mm Hg during the measurement phase. The time from opening a stopcock at the end of the standard fluid administration tubing to complete expulsion of air from the inverted pressurized system was measured with a stopwatch. Data points were obtained in duplicate for each volume measurement.

Figure 1

Figure 1

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Four cases of fatal air embolism were associated with 127,586 perioperative blood recovery procedures in NYS from 1990 to 1995; none were associated with 8,955,619 conventional transfusions. During 89,644 IBR procedures, 3 fatal air embolism incidents occurred (1:30,000 IBR procedures); during 37,942 PBR procedures, 1 occurred (1:38,000 PBR procedures). During the same interval, 8,955,619 conventional blood components were transfused without any report of air embolism. The incidence of air embolism during blood recovery procedures was significantly higher than that during conventional transfusion (Fisher's exact test, P < 1 x 10-8). The reported fatalities all involved reinfusion of recovered blood under pressure.

A model devised to allow estimation of airflow rates that might occur in an air- and fluid-containing administration system under external pressure, such as in a fluid resuscitation situation, permitted 49.3 mL/s. (range 43 mL/s. to 61 mL/s.) of air to be delivered through this system when the delivery bag was externally pressurized to 300 mm Hg (Figure 2).

Figure 2

Figure 2

The four cases of fatal air embolism (and a fifth, Case 4, which was reported in 1986) associated with perioperative blood recovery and readministration procedures are illustrative of causative factors and indicate steps that might be taken to reduce the mortality associated with the procedure.

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Case 1

A 55-yr-old man with ischemic cardiomyopathy and end-stage heart disease underwent cardiac transplantation at a community hospital. Profuse bleeding into the chest cavity followed anastomosis of the allograft. No mechanical cause for the bleeding was identified, and the coagulopathy was ascribed to a residual Coumadin[R] (DuPont, Wilmington, DE) effect. Numerous units of blood and blood products were administered in an attempt to control bleeding, first without and then with a pressure infusion device. All the blood was emptied from the pressurized infusion bag. As the surgeon started to close the chest, he noticed that the right atrium, right ventricle, and pulmonary artery were expanding. Air was heard hissing through previously placed needle holes and through the right atrial suture line. The surgeon attempted to expel the air from the heart, and the patient was returned to cardiopulmonary bypass. At this point, the patient developed cardiac arrest. Air bubbles were visible within the coronary veins on the surface of the heart. Despite intensive attempts at resuscitation, including cardiac pacing, the patient died.

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Case 2

A 79-yr-old man underwent aortic valve replacement at a tertiary care medical facility. An automated IBR device was used, but the recovered red blood cells were reinfused directly from the collection bag rather than from a transfer bag as specified in the facility's standard operating procedure (SOP). Additionally, a pressure cuff was placed around the collection bag to speed delivery. At the end of the procedure, hypotension developed and air was aspirated from the pulmonary artery and right atrium. After surgery, the patient awoke and exhibited purposeful movement but soon thereafter developed renal and hepatic failure attributed to the air embolism and accompanying hypotension. He became comatose and died 1 mo later.

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Case 3

An 88-yr-old man underwent repair of an abdominal aortic aneurysm at a community hospital. A nonautomated IBR device of the rigid canister type was used. A pressure cuff was placed around the administration bag and was used intermittently during reinfusion of recovered blood. Despite attempts to purge air from the bag, after reinfusion of approximately 100 mL of blood, a large audible bolus of air was noted to enter the tubing. Air was aspirated from the pulmonary artery catheter. The patient rapidly developed hemodynamic deterioration. Resuscitative efforts were unsuccessful, and the patient died 45 min after the event. Investigation by a medical engineering consulting firm documented a defective radio frequency weld that caused the bag seam to fail, allowing the entry of air.

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Case 4

A 52-yr-old man underwent coronary artery bypass grafting at a tertiary care medical center, and an automated IBR device was used during the procedure. At skin closure, the pressurized reinfusion of recovered blood was begun, and hypotension, bradycardia, and decreased end-tidal carbon dioxide tension were quickly noted. The transfusion bag was found to contain air, which was aspirated from the pulmonary artery catheter. The thorax was reopened, and additional air was evacuated by needle aspiration from the right ventricle. Despite open-chest cardiac massage, return to cardiopulmonary bypass, intraaortic balloon pump insertion, and maximal pressor support, asystole and death occurred 4 h after the initial event.

Upon investigation, it was found that the automated IBR device in use allowed entry of air into the collection bag if left in the "empty" mode after all blood was recovered from the reservoir. Further, when in the manual mode, the system air detector was not active; rather, the system depended on constant monitoring by the operator.

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Case 5

A 41-yr-old, otherwise healthy, man underwent lumbar laminectomy with L4-L5 fusion at a community hospital. Estimated blood loss during surgery was 2,500 mL, with pre- and postsurgery hemoglobin values of 12.3 g/dL and 7.4 g/dL, respectively. After surgery, the patient was alert and was transferred to the intensive care unit with a blood recovery device in place for postoperative blood collection. Within the first 4 h, although the device contained only 150 mL of sanguinous fluid, the physician ordered the recovered fluid reinfused along with 1 U of packed red blood cells. Staff unfamiliar with the device applied a pressure cuff to the recovered blood bag to assist in the delivery of fluid. At this time, the entire bag emptied quickly and audibly. The patient immediately lost consciousness and then developed cardiac arrest. Resuscitative efforts were unsuccessful, and the patient died 30 min later. Autopsy showed a massive air embolus.

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The role of autotransfusion of recovered blood in avoiding or reducing allogeneic blood exposure is well established in thoracic, abdominal, vascular, and orthopedic surgery, as well as in trauma, liver transplants, obstetrics, and neurosurgery, and such special circumstances as crossmatch difficulties and religious objections to blood transfusion. However, the presence of perforated bowel, infection in the surgical field, malignancy, or amniotic fluid and the use of collagen hemostatic material are generally considered to be contraindications to these techniques [14]. Early cases of air embolism were related to an automated roller pump system with reservoir, which was taken off the market in 1979 [10,11]. Additionally, rare complications such as upper airway edema attributed to activation of complement [15] and hypertension attributed to catecholamine effects in a patient undergoing pheochromocytoma resection have been reported [16].

NYS Department of Health records indicate that 89,644 IBR procedures and 37,942 PBR procedures were performed from January 1990 to June 1995. During this period, there were three fatal air embolism incidents during IBR (a rate of 1:30,000 IBR procedures) and one during PBR (a rate of 1:38,000). A fifth case described herein (Case 4) occurred in 1986, before initiation of collection of comprehensive data. During the same time interval (1990-1995), 8,955,619 conventional blood components were transfused with no occurrence of air embolism reported.

While all hospitals report the number of IBR procedures performed, failure to report all procedures at some hospitals could have led to an underestimation of total procedures and a slight overestimation of the incidence of this complication. It is also possible that additional air embolism episodes went unrecognized in patients with concurrent complications, leading to an underestimate of its incidence. One small study of autologous blood recovery did not report air embolism complications [17], but no other study has reviewed the number of transfusion procedures needed to accurately identify this occurrence. The NYS Department of Health issued cautionary advisories on June 26, 1992; July 20, 1994; and September 16, 1994 to all facilities approved by the state to provide transfusion services. The fatality rates currently reported far exceed the reported rates of fatal acute hemolytic transfusion reaction to allogeneic blood, which is estimated at 1:600,000 to 1:800,000 [18,19]. They also far exceed the rate of transfusion-transmitted infection with human immunodeficiency virus, which has most recently been estimated at 1:450,000 to 1:660,000 [20].

All five of the reported cases of fatal air embolism associated with blood recovery and readministration techniques occurred in medical facilities experienced in blood recovery techniques. However, all cases were related to insufficient knowledge or lack of vigilance on the part of operators and/or to deviation from SOPs. All cases involved recovery and subsequent infusion under external pressure, which allowed air delivery to occur. The systems in use included both manual systems lacking an automated air detection system and automated systems in which the air detection system did not function properly or in which the reinfusion bag and the air detector were bypassed. It should be noted that the flaws identified in Case 4 have been corrected in current versions of the device. However, in the presence of air in the system, the concomitant use of pressure with very rapid flow rates requires flawless function of the air detector and shutoff mechanisms.

The model system constructed to simulate blood recovery and pressurized readministration permitted as much as 200 mL of air to enter the circulation in as little as four seconds. This amount has been previously estimated to constitute a fatal dose in humans [21]. Given such a rapid flow rate, the response time for the human eye and hand is most probably too slow to effectively recognize and react to an air embolus in a fluid delivery system. Operator vigilance alone would likely not suffice.

Placement of a reinfusion bag in the administration line between the blood collection unit and the patient's circulatory system serves to loosen the coupling of these systems with blood recovery (Figure 1). Bypassing the reinfusion bag necessarily increases the tightness of coupling, increasing the risk that any air within the collection system will enter the patient's circulation. Reinfusion of recovered blood under pressure is not only a complicating factor, but it may also speed events beyond the capacity of an operator who relies solely on visual detection of air to prevent a fatality.

Given the fatal outcome in these incidents of air embolism associated with IBR and their occurrence at a rate far exceeding other fatal complications of transfusion, including hemolytic incompatible transfusion reactions and transfusion-transmitted human immunodeficiency virus infection, it seems reasonable to incorporate the lessons of these cases into a set of proposed guidelines for optimizing the safe use of this increasingly popular means of hemotherapy.

The manufacturers' instructions for IBR devices should be followed in developing SOPs, and those procedures should be adhered to by all staff. Staff should be thoroughly trained in the established SOP, and there should be no transfer of operational responsibility to untrained staff. Training should emphasize identified potential failure points, such as those reflected in the following general operational guidelines:

1. Whenever possible, avoid direct reinfusion from the recovery container (i.e., transfer recovered blood into a reinfusion bag prior to administration). If this is not possible, it is necessary to remove attendant air by venting or other means.

2. Strictly limit reinfusion of recovered blood under pressure to situations in which the application of pressure is a medical necessity. The presence of air in the administration bag should be determined, and all air should be definitively expelled prior to placement of any pressure infusion device. Use of an automated air detector should be considered when using pressureaided reinfusion. However, even these automated devices may fail.

3. Maintain both human vigilance and automated monitoring in detection of air that might enter the system.

4. Carefully consider the use of postoperative blood recovery, since in many situations it is of dubious benefit [22,23]. The recovered fluid contains relatively few intact red blood cells despite its red color [24].

5. Institute refresher in-service teaching and periodic competency testing for personnel using the equipment. Include in the facility SOP a requirement for the intermittent documentation of adequate function of IBR devices by appropriate parties, such as the manufacturer or biomechanical firms.

In summary, IBR has a legitimate role as a strategy for reducing transfusion exposure. These cases, however, suggest that special care must be taken with delivery techniques because of the high mortality risk associated with air embolism. The increased hazard of fatal air embolism associated with the use of pressure suggests that it should be used only when necessary and that proper procedures and safeguards should always be utilized.

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